These videos provide information on pathogens and pathways of drinking-water contamination, principles and methods of small drinking-water supply treatment, reticulation systems, sampling and monitoring, and how outbreaks can happen in drinking-water supplies. They were produced by the New Zealand Ministry of Health as part of the Drinking-water Assistance Programme.
They support drinking-water quality improvement, especially in small and self-supplies.
Don’t bug me!
Pathogens and pathways in drinking-water supplies – 22 minutes
This video looks at the access and presence of pathogens in drinking-water supplies. It is intended for small drinking-water supplies. It is useful for Pacific countries.
[Ministry of Health logo]
Voice-over: This DVD has been produced by the New Zealand Ministry of Health. It provides information on the pathogens and pathways of contamination that can affect small drinking-water supplies.
[Music, as the animation fades in. It shows a river in the New Zealand bush. It zooms in through the bush to the river.]
Voice-over: Drinking water is usually safe in this country, but not always. It has been shown that most urban supplies in New Zealand, in medium and large cities, have safe water – better than most parts of the world.
[The animation begins to pan across the river.]
Voice-over: In small supplies, this may not be the case. There can be germs in drinking water – bacteria, viruses and protozoa.
[The animation pans across to a house on the hillside, with the speaker standing outside. He stands next to an outdoor tap, holding a cup.]
Speaker: These are microscopic organisms that can't be seen by the naked eye but which can cause serious illness, and sometimes even death. It doesn't take much for a water supply to become contaminated. A dead rat in a water tank or a cow pat in a river can make many people who drink the water sick. This is why keeping a community's water supply safe to drink is vitally important. Someone has to work hard at keeping the bugs out of the water. If the system breaks down or if someone doesn't do their job properly or if the water is not being treated at all, then the results can be disasterous.
[He turns on the tap and fills his cup. The camera zooms in on the water.]
Title [on a bubbly background]: Don’t Bug Me: Pathogens and Pathways in Drinking Water Supplies
[The title fades out, and the scene changes to a park. An old man sits on a bench, with his dog tied up next to him.]
Old man: There was an outbreak of entric disease – about 3500 people were affected – and, um ah – [he falls asleep].
Dog: The town pulled their water out a lake, which is filled up with people running round in boats. And on the sides of the lake there was a whole lot of people living in houses with waste water. The waste water gets pumped up along the lake shore. One of those pump stations failed so sewage ran into the lake. And unfortunately it failed right where the pump taking water out of the lake was so they pumped water with sewage round. And most of the town – particularly most of the children in the town – got diarrhoea-type illnesses, vomiting and diarrhoea.
[The scene changes to a young man standing outside a marae.]
Young man: You may think that your water's safe. You may never get sick cos you've got an iron gut like me. But I tell you what, it's a different story for our tamariki and our kaumātua. If they're getting sick, you know you've got a problem. And we had a situation at our marae a few years ago where some of our manuhiri got sick. And some of the people on the committee said to me, 'It's the water, it's the water making them sick.' I said, 'It's not the water. People've been drinking that water for years.' And they eventually convinced me to go up and check the stream, and when we went up there there was a dead cow in there.
[Shot of the young man up the stream, hands over his mouth because there's a dead cow in the water.]
Young man [voice-over]: Never bothered ever checking them before.
Young man: But ... what we found that day, made our visitors sick. It's part of our traditions, our tikanga, to look after our visitors and make sure that they're well and healthy. But because I didn't check, they got sick.
So, what I'm saying to you is that you've got to make sure that your water's clean and pure. Not only for your visitors, but for your kids, for your tamariki, for your kuia, for everyone.
It's not worth risking it, at the end of the day. It's not worth it.
[The location changes to a classroom. A woman in a lab coat stands at the front next to a projection of a bacteria diagram. The diagram points out the plasma membrane, cytoplasm, cell wall, DNA, ribosomes, pili and flagella.]
Woman: One of the major sources of water contamination is bacteria. Bacteria are single-celled organisms. Bacteria have been around for a very long time, appearing on earth 400 million years ago.
[The location changes to a family kitchen, with the mum, dad and son sitting around a table.]
Dad: Most bacteria don't really affect us at all. It's not that all bacteria are bad, eh?
[The son looks disinterested.]
Dad: Doesn't harm us, we don't harm it – it's got nothing to do with us.
Mum: And actually, a lot of bacteria are really good.
Dad: Well, I guess –
Mum: Because they can actually help digest food in your intestine.
Dad: Yeah. And you've got all that bacteria on your skin.
Mum: Yeah. And the good bacteria can actually keep the bad bacteria at bay. And there's actually really only a small group of bacteria that are really harmful to humans.
Dad: And they're the pathogens.
Mum: Yeah. Like campylobacter.
Dad: Yeah, I had campylobacter. It was terrible. And shigella and salmonella.
Mum: Yeah, salmonella.
Dad: And Salmonella Dub, that's the band, eh. And shigella sounds like a girl's name.
[The son puts his head on the table.]
Dad: Hey, this is my daughter, Shigella.
Mum (disapprovingly): Mm.
[The image changes to a bacteria, having its picture taken as if it were for a police line-up. It is holding a card that has 'Ministry of Health' written on the top, and a number. Then the location changes to a cell with two bacteria in it. One of the bacteria is up against the cell door and is talking to us. The other one is trying to saw through the bars on the window.]
Bacteria: If people get me through their mouths and into their guts, I will work in about, say, 18 hours or thereabouts to make people sick. People are more likely to get diarrhoea and ... well, I can really cause very nasty illness. And effectively I'm attacking the inside of your gut.
[The scene changes to a resturant. First we see a woman looking at a menu, then we see that she is sitting across from a man.]
Man: Do you know that if you took all the people who ever lived – not just the people who are alive now, but everyone who ever lived – did you know that you've got more bacteria in your mouth than that?
[She begins to put down the menu, looking unimpressed.]
Man: And one single gram of faeces, you imagine that, you hold a single gram of faeces in your hand – [she begins to look around, as if for an escape route] – and there are a trillion bacteria, not mention the dirty hand. There's the faecal–oral route. Who's the scientist who worked that out, did he wash his hands?
[The woman is glaring at him.]
Man: They're the largest population on earth. Billions, billions. [He wave his hands.]
Woman: Dennis, you really need to find a new hobby. [She stands up and leaves.]
Dennis: Where are you going, come back ...
[The scene changes to a 'Pathogens Anonymous' meet-up. The pathogens are sitting round in a circle.]
Pathogen: Um, hi, I'm campylobacter and I'm a pathogen.
Group leader: And how've you been doing this week?
Campylobacter: Ah, well, it started off ok, but I got on some kid's fingers and then I got into his stomach and then I was in his gut and I, I just couldn't help myself. I just, I started multiplying. [The group draws their breath in disapprovingly.]
Group leader: It's alright, it's alright, we're not here to judge. Tell us what happened, did you try the exercises?
Campylobacter: I did, I tried the breathing exercises. [Does some sharp breaths in and out.] It didn't really work, really. Well, I tried, I tried, I tried to stop myself from multiplying. I tried, but I just couldn't.
Group leader: What happened? Can you tell me what happened?
Campylobacter: Ok, well ...
[The campylobacter starts to sing.]
When I'm in a place that's moist and warm ...
[We see the campylobacter appear on a stage with a spotlight on it.]
And I'm so lonely I could cry,
Through cellular division ...
[The campylobacter splits into two campylobacter.]
I start to multiply.
[A farm backdrop appears on the stage, and the camyplobacter put on straw hats.]
Given conditions that are favourable,
Every 20 minutes we will subdivide.
[The campylobacter split into 4 camptylobacter. The background changes to a shop storefront. They put on barbershop quarter-style hats.]
1, 2, 4, 8,
16, 32, 64, 128,
[The curtain drops, then rises again on a church full of campylobacter.]
I say, 512,
I say, 1024,
I say, 2048,
I say, 4096,
[The lights change and only one campylobacter is left onstage.]
We're going to ...
[The other campylobacter also appear on stage and start to can-can.]
... multiply through your body,
We'll multiply exponentially,
We'll colonise your intestine,
We'll make you sick, we'll make you nauseous,
We'll give you diarrhoea.
[The campylobacter start to split again.]
We'll multiply, multiply,
[The scene changes back to the woman at the front of a classroom. Her slide changes to a diagram of the protozoa giardia.]
Woman: Protozoa are also single-celled organisms – [the slide changes to a protozoa cryptosporidium emerging for a cyst] – but they are a lot larger than bacteria.
[The scene changes to a lab room with an older guy in a lab coat.]
Man: You don't need to swallow many protozoa to make you very sick. [He wiggles his fingers.] They multiply like bacteria and can completely line the inside of your gut – [he lifts a finger warningly] – which means that the body can't make use of the food you eat. Two common protozoa are giardia and cryptosporidium.
[The scene changes to a protozoa sitting at a bar.]
Protozoa: Yeah, well, I'm a protozoa. And one of my favourite places to hang out is in the intestine. An animal intestine. Cow's one of my favourites. And I just hang out there and then the cow poops me out. And so, right, I'm in the cowpat, and the cowpat starts to cool down, and I don't like an environment that's cool, so I go into my cyst state.
[The animation shows the protozoa, on a cowpat, curling up into a tiny ball.]
Protozoa: And that protects me there, that can protect me there ...
[The animation shows a cow pooing next to a river. It's raining.]
Protozoa [voice-over]: ... just sitting in the soil until I'm picked up by another animal. [The cowpat runs into the river.]
Protozoa [back at the bar]: Hopefully a human. And then it only just takes one of me to get down into the digestive system, and I can replicate. And then what may happen is, the intestine might expel me, after a period of time. And I'm quite difficult to get rid of, but eventually I will be passed through the digestive system, end up back in the soil again, in my cyst state.
[The scene changes to a news show, with a bacteria reading the news while a giant protozoa is shown rampaging through a city. The ribbon at the bottom of the screen reads 'Protozoa attacks bacteria city.']
Newsreader: We interrupt this programme to bring you a special news report. It appears that protozoa have entered the intestine.
[The image switches to a roving news bacteria, with worried bacteria and a rampaging protozoa in the background.
Newsreader: Can you tell me what's happening at the moment, Wendy?
Wendy: Yes, Jim. Protozoa are much larger than the bacteria, as you can see behind me. It's really quite scary. [The protozoa is seen picking up bacteria and eating them.] And they're actually ... they're eating the bacteria. And it seems like they're multiplying. [The protozoa splits in two.] Yes, they're multiplying now, Jim.
Newsreader: So, what's gonna happen next, Wendy?
Wendy: Well, Jim, the protozoa are going to attach themselves to the intenstine wall. And they're going to completely line the intestine, so that no food can get into the body. They're going to make our host very sick indeed, Jim.
Newsreader: So are there any good protozoa, Wendy?
Wendy: Well ... not for humans, Jim. But in the human body, they can be deadly.
[The image switches to two bacteria watching TV. One is knitting and one hold the remote.]
Knitting bacteria: Why is the news always so bad? Why can't we change the channel?
[The image switches to the TV, and the channel changes to a title screen reading 'Virus attack'. Spacey music plays.]
[The scene is in black and white, and shows a spaceship moving through space.]
Voice-over: Viruses are much smaller than bacteria and they can be harder to kill.
[The spaceship lands on an asteroid and opens its hatch.]
Voice-over: A virus is basically just a simple package of DNA or RNA [a laser comes out the hatch and begins to make the asteroid big and bubbly] that reproduces by integrating into the host cell and making copies of itself.
[The asteroid explodes and dozens of little spaceships come out. The image changes to a woman on a TV screen, still in black and white.]
Woman: The waterborne viruses that we recognise as potential problems in New Zealand are [the image changes to show a norovirus] norovirus, that's a virus which can cause diarrhoea.
[The image changes to hepatitis A.] There's hepatitis A, hepatitis A virus, which causes liver disease. And that's a virus which survives very well in water and is recognised almost entirely as being waterborne.
There's also adenoviruses [the image changes to show an adenovirus]. These are a range of viruses which are often associated with recreactional water – swimming pools [the image changes to a young boy underwater with goggles on] – and they can cause throat infections and eye infections. And some of those cause diarrhoea and gastroenteritis as well.
And the other group of viruses are the enteroviruses. [The image changes to show a polio virus.] And one of the examples there is polio virus, which is a virus which can cause paralysis, meningitis, heart disease, liver diseases, all sorts of horrible things.
[The scene changes to two men, one tall, one short, in a water treatment plant.]
Tall man: Water can be contaminated by human viruses when there is human waste discharged into it. So that's faecal waste. And viruses can be harder to kill with chlorine than bacteria.
Short man: And the other difficulty with viruses, especially the waterborne ones, is that they're so small they can pass through filters.
[The scene change back to the woman at the front of the classroom. Her slide changes to show a helminth, a wormlike creature, with parts of its body labelled, like the spicules, medio-lateral ray, testes and intestine.]
Woman: Helminths are worms that live in the intestines of animals and humans. The tapeworm is a common helminth. Helminth are much larger than bacteria and protozoa. In fact, some are up to a metre in length. The eggs of a helminth, which appear in urine and faeces, can be accidentally ingested by a human.
When it hatches, it will grow into a worm and live in the human body as a parasite. Because they are so large, tapeworms can physically block the intestines.
[The scene changes to the family at the kitchen table again.]
Mum: They're a major source of disease in some countries because –
Dad: Not in New Zealand, they're not.
Dad: We don't have a problem here, but yeah, in other countries they are a major source of problem. Health problems.
Mum: Yeah. Serious health problems.
Dad: Very serious.
[The scene changes back to the woman in the classroom. Her slide changes to show some cyanobacteria.]
Woman: Cyanobacteria is the name given to a group of organisms that live in colonies. They live in water and, like plants, they produce their own food through photosynthesis. The reason we have so much oxygen in the atmosphere is because cyanobacteria produced it billions of years ago.
It is also known as blue-green algae, though it's not actually algae.
[The scene changes to a woman being interviewed. We can see the interviewer and a man holding a boom mic, as well as the woman herself.]
Woman: So the problem with cyanobacteria is they produce a range of natural toxins that we call cyanotoxins. And those cyanotoxins are obviously a health risk to humans consuming that water or even just having contact with the water.
Couple of cases in Brazil, one in 1996 where a hospital's water supply became contaminated and dialysis patients received this contaminated water. And I think 56 of them died, from complications associated to it.
Woman: Yeah, and another case in Brazil, where a water supply became contaminated and 88 people died.
[The image switches to show a funeral.]
Woman [voice-over]: So yeah, there are some quite serious cases of it.
[Back to the woman.]
Woman: And in Australia, another incident where a dam experienced a big cyanobacterial bloom, and they treated it with algacide – which actually causes the cyanobacteria to die, which lyses the cells and releases this massive pulse of toxins into the supply. And in that case I think they hospitalised 150 children.
Title: The Faecal–Oral Route
[Back to the classroom, where a slide comes up showing a washbasin and a poster reading 'Wash your hands'.]
Woman: The faecal–oral route refers to any way that faecal material can enter into the human digestive system. There are many ways this can happen, such as a person not washing her hands after going to the toilet and then eating food, or a farmer, milking a cow, picking up bacteria off the cow's udder and then wiping his mouth. Faecal contamination can then pass into the mouth, and bacteria or protozoa can then enter the gut and start to reproduce.
[Scene changes to show a man in front of a run-down looking house.]
Man: Well, it was a long dry summer. And there wasn't a lot of water around. And it started to pour down with rain and I thought, well, I'll just get a big bucket [the image shows a man in the rain, collecting water coming out the roof spouting] and whipped round the back when it was really pouring down and stuck the bucket under it.
And I thought, great! And that's the water that I drank that day. Until at about, you know, 5 or 6 o'clock at night, I thought uh-oh. And I had to rush off to the loo.
The sh– diarrhoea. [Laughs] And it felt like giving birth, really – not that I know much about giving birth! But yeah, it was pretty hard out. And I was told there were rabbits on the roof [image switches to show some rabbits and their poo on the roof] but they were actually rats! [Rabbits turn into rats.] And there was a lot of rat poo around, I know that. So that wasn't very good.
And birds – probably actually predominantly birds, a lot of bird poop up there.
[The scene changes to show a farmer by a river.]
Farmer: Yeah, well, we've all been sick for months, you know. And you know this health guy came along and he came along the back and had a look at the farm. And he said, 'Look, here's the pipe. You know, where your water's coming from. [Image shows show cows crossing a river.] And all these cows are crossing the river up there, and that's flowing downstream and going into your water pipe. And now you're drinking it.' [Back to the farmer.]
I mean, that didn't even occur to me. We didn't even think about it, we were just turning the tap on and drinking the water. So we just moved the pipe, about a hundred metres up the stream, above where the cows cross, and we've been right as rain.
[The scene changes to show two women, one older, one younger, sitting on a bench in front of a house.]
Older woman: Well, we went and we bought this house in the country. And it was really nice.
Younger woman: It was more than nice, and it was more of a cottage than a house. Yes, you remember.
Older woman: Yeah. The neighbours –
Younger woman: It was our dream home.
Older woman: The neighbours [the image switches to show a cross section of a house and the plumbing under it] above us had a septic tank. But all the water was going, all the stuff from the septic tank was going into our drinking water. [The animation shows toilet waste going into the septic tank, and that leaking into the groundwater.] And it was draining into what we thought was beautiful spring water [the waste goes into the pipe connected to the women's home]. And it was draining all this effluent. And it was making us really really sick.
Younger woman: And of course it was filled with, you know –
Older woman: Poos.
Younger woman: Nasty bits. And we were – we were sure it was pure. And there we were busily drinking it, and encouraging the children to drink more of it, when it was contaminated.
[The scene switches to show another farmer, out in front of an open water trough, with cows in the background.]
Farmer: Ok, well, we just woke up one morning, and the whole tribe were starting to feel sick in the stomach. And we ended up, like 10 o'clock in the morning, we had them all at home, vomiting and diarrhoea and all that sort of stuff. And well, we had to trace it back to somewhere, and we realised the day before we were out filling the feeding troughs, water troughs, with the hose and stuff like that, and ... something happened.
[Image changes to show a hose in a trough, and the water draining out.]
Oh, that's right, yeah yeah, we left the hose, you know, you drop the hose in the trough, turn it on and go away and do something else, and meantime the pressure had dropped, and the water from the troughs had gotten sucked back up [image switches to show someone turning on the tap and dirty water coming out] through the system and into our drinking water, and that's what the kids were drinking. So were we, for that matter. So we were all out to it.
[Back to the classroom. The slide changes to show a water supply and a water tank. The water supply is connected to a hose which drops into the water tank. The direction of water flow is labelled, running from the water supply through to the tank.]
Woman: Backflow occurs when contaminated water [slide switches to show water flowing in the opposite direction after a drop in water pressure] is sucked back into the water supply when water pressure drops.
[Scene changes to show a tortoise in a zoo enclosure.]
Tortoise: The other problem with backflow, where if you have a system where somebody is using the water in such a way that if the pressure in the main water system drops, water can be sucked back into the mains. This can spread organisms.
We had a case in the zoo, when the people were mixing up an arsenic weedicide and they left the hose in the tanker that was, that they were mixing up the weedicide in. There was a pressure drop and one of the workmen was drinking some of the water later on and he died of arsenic poisoning.
Title: E. coli testing
[Back in the classroom, the woman's slide switches to show some E. coli bacteria.]
Woman: When we test water for contamination, it woudl be very expensive and time-consuming to test for every possible kind of bacteria, protozoa or virus. Instead, we test for just one bacteria: E. coli.
[Scene switches to a couple of cows looking over a fence.]
Cow: E. coli is a bacteria which is found in human and animal excrement.
Cow 2 [laughing]: Excrement.
[Scene changes to show a young woman, with a writing pad in one hand, and a small chilly bin in the other, skateboarding down the street.]
Woman: Well, E. coli is found in faeces and faecal material so if we find it in the water, it means that the water, of course, has been contaminated with faecal material.
[Scene changes to show a man at a school, taking a sample from an outside tap.]
Man: You know, for drinking water, you want no bacteria. You want no E. coli. E. coli indicates that there is disease-causing organisms, there may be disease-causing organisms in the water. So you want your drinking water to have no E. coli.
[Scene switches to show a woman in a laboratory with a UV light box, incubator and other equipment. She has a sample container of water in front of her.]
Woman: Well, first, we make sure that the water is the right temperature. And then we add the medium [she adds a powder to the sample] to make the bacteria grow. And then we shake it up [she shakes the bottle and we leave it in the incubator for 48 hours [she places the container in the incubator].
[She then holds two containers, one which has colourless water in it.] Now, this one here is clear, so it's a negative result. [She lifts the other container higher. It has yellow water in it.] Now, this is a positive test. And when we put it under a UV light [she puts the yellow container in the lightbox, where it starts to glow] we can see the fluorescent glow, which indicates that E. coli are present.
This means that the water is contaminated and may contain other pathogens. And this is just one of the ways we test for E. coli.
[The scene switches back to the man from the very start of the video.]
Man: We need to make sure that when people turn on the tap to get a drink of water, that there are no bacteria, no viruses, and no other pathogens. Even a small number of pathogens can have a huge impact because they multiply so easily. Just one germ can become 10 million in a short space of time. This is why the treatment of water is vitally important.
Everyone should be confident that the water they drink is absolutely safe.
[End music rises.]
[Ministry of Health logo]
Download Don't Bug Me! (MP4, 134 MB) – right click and choose 'Save As'
Making it safe!
Principles and methods to treat small drinking-water supplies – 36 minutes
This video provides information on some of the treatment methods that small drinking-water supplies can use to help them provide safe drinking-water.
Download Making it safe! (MP4, 423 MB) – right click and choose 'Save As'
Tanks, pumps & pipes
Small drinking-water supply reticulation systems – 15 minutes
This video provides information on reticulation systems for small drinking-water supplies.
[Ministry of Health logo]
Voice-over: This DVD has been produced by the New Zealand Ministry of Health. It provides information on the operation and management of reticulation systems for small drinking water supplies.
Title: Tanks, Pipes and Pumps: Small Drinking Water Supply Reticulation Systems
[Scene shows a man outside his house, using a hose to water his vege garden.]
Man: The benefit of treated and reticulated drinking water is that it provides safe running water to the consumer at the turn of a tap. The decline in waterborne disease over the past century in developed countries is a direct outcome of water treatment. But all water suppliers, including the small water supplier, has the job of not just making water safe to drink, but also making sure that the water remains safe after leaving the water treatment plant until the point of delivery.
[Scene shows a different man outside a rural house. He carries a toolkit.]
Man: A water storage and distribution system is called a reticulation system. This refers to the tanks and pipes used to get water from a treatment plant to a house or building. Often, its component parts include storage tanks [a storage tank appears in the empty yard outside the house], reservoirs [a reservoir appears behind and above the storage tank], pumps [a pump appears by the storage tank], meters, pipes [the pipes appear, connecting the pump to the house] and backflow prevention valves.
But a simple roof tank, and the pipes which use gravity to feed to a tap, is also a reticulation system.
The reticulation system needs to be a safe and secure system of getting water from the treatment plant to the consumer.
[Scene showing an older man in an office with a harbour view.]
Man: Many water treatment plants actually spend less money on the treatment facilities than they do on reticulation systems. But it's often easy to overlook to vulnerability to recontamination of water within a reticulation system. Once the water is clean, we do not want it to be recontaminated. Nearly half of all outbreaks in waterborne disease in the USA between 1995 and 1998 were caused, not by problems in the treatment plant, but by deficiencies in the reticulation system.
[Back to the man from the start of the video, who is now sitting on his deck with a jug of water and a glass.]
Man: Ensuring that water remains safe after it leaves the water treatment facility until it gets to the point of delivery is a major challenge. [He fills his cup.] But as a water supplier, your responsibility doesn't end with getting the water clean with treatment processes. It includes making sure it stays clean and safe when it's in the distribution system, keeping it clean until it comes out of the tap [he lifts his glass to drink].
[Scene changes to show a man standing in front of a water tank. The tank has a pipe coming out of the ground and one leading into the shed behind the tank.]
Man: We just upgraded the treatment plant and got a new UV unit, filter system. And then we tested the water and found that we were still getting E. coli in the storage tank. Talk about frustrating. And really really disappointing too, to find out that as soon as we'd treated it, it was getting contaminated as soon as we put it in the tank. After spending all that money, time and effort. I guess I assumed that once the water was clean, it would stay clean.
[Shot shows the opening in the roof of the water tank.]
It turns out that the tank has a sloping roof, and the lid didn't fit properly [a round lid appears over the squarish opening]. So the rain was washing the bird poo off the roof, into the water that had only just been treated. And the problem was so easy to fix. And we just thought that once we'd treated the water that the job was finished.
It turns out that having a UV system was a waste of time if we just let the water sit there getting contaminated again while it was in storage.
[Scene changes to show a woman standing out on the street, with a cafe and post shop on the other side of the road behind her.]
Woman: Once the treated water has left the treatment plant, we don't want this water recontaminated. In other words, treated water needs to be protected from any contamination that may allow bacteria, protozoa or viruses to get back into the water.
[Scene changes to show a technician working on a pump that has been taken off side of a storage tank.]
Technician: But recontamination covers more than just recontamination from pathogens. For example, pump equipment should be selected and installed to prevent recontamination by pollutants that might get into the water. Like lubricants from the pumps.
[Scene changes to show the man from the second scene, sitting on top a storage tank with his toolkit out. He is on the phone.]
Man [on the phone]: Yeah yeah, oh good, ok. [He puts the phone down.]
Man: Tank vents are a necessary part of the system. They must be covered or screened by a mesh screen. [He lifts up an example of a screen, and puts it down on the vent at the top of the tank.] Secure hatches and non-corrosive screens are needed to prevent small animals or birds from entering and recontaminating the water. Overflow pipes also need to be protected from entry by birds or animals.
[The man looks inside the hatch of the water tank, and speaks into the tank.]
Man [echoing]: To ensure the reticulation system remains secure, it needs to be regularly maintained. This could include inspections of tank hatches, vents and overflows, and period microbiological tests to confirm recontamination hasn't occured.
[Scene changes to show a woman standing outside a different, plastic-looking storage tank.]
Woman: Storage facilities are necessary so that the communities they service are provided with enough water for a period of time – at least 24 hours at the average flow rate – in case the supply from the treatment plant is interrupted.
If we were dosing chlorine as a disinfectant, remember reservoirs can also act as a place where contact time with chlorine and inactivation of pathogens occurs.
[Scene changes to show a young woman standing in front of a couple of fenced-off storage tanks.]
Woman: There are two basic types of storage reservoirs, and the supplier needs to choose which suits best for their own particular water source and availability, as well as the needs of the consumer.
Ground-level storage tanks are excellent for the small supplier and are simple to construct and maintain. These can be constructed on a hill that's high enough to provide adequate system pressure. The size of the reservoir will depend on the peak and average demands.
[The background behind the woman changes to show a water tower.]
Elevated reservoirs or water towers like this one, which aren't very common in New Zealand, hold water at a height that maintains pressure to the distribution system without the need for continuous pumping.
[Scene changes to show a man in a hard hat checking the ceiling of a leaking building.]
Man: Construction materials need to be given consideration. A tank with a roof constructed from treated timber – see, look at that [he points his torch at where the leak is worst] – can release arsenic from the timber treatment chemicals into the water ...
[Shot changes to a diagram showing treated water separated from treated timber by a robust liner.]
Man [voice-over]: ... unless the timbers are protected with a robust liner.
[Back to the man.]
Man: Asphalt or tar cannot be used for waterproofing the interior of the reservoir because they can chemically contaminate the water.
[Scene changes to show a woman in a lab coat, inspecting an open water tank. She is up a ladder looking in. There is green all around the tank above the water level.]
Woman: Rough surfaces or crevices in the walls of reservoirs need to be avoided as these provide a haven for slimes or biofilms [she points at the green stuff].
Biofilms can shield some pathogens from chlorine. And particularly vulnerable are the interface of air and water [she points again], scum lines or rings.
[Shot changes to show a diagram of the interface between water and tank wall. There is a crevice in the tank wall, filled with a biofilm. The residual chlorine is effective in the water itself, but it is not effective in the biofilm filling the crevice.]
Woman [voice-over]: These are excellent places for pathogens to be masked from residual chlorine in a tank. So tanks need to be inspected regularly and biofilms removed by water-blasting.
[Scene changes to show the woman standing outside the plastic-looking storage tank.]
Woman: A top-filling bottom-emptying regime [Shot changes to show a diagram of a well-designed tank, where the water comes in from a pipe above the water level, the water circulates inside the tank, and then leaves via a pipe at the bottom. Residual chlorine is effective throughout the tank.] is the best way to get residual chlorine circulating and avoiding short circuiting.
[Diagram changes to show a short circuiting tank, where water enters and leaves the tank through pipes at the bottom of the tank. The water moves straight through the tank, and residual chlorine is not effective.]
Woman [voice-over]: Short circuiting is when water enters the cistern and then goes straight out, leaving the bulk of the water static.
[Scene changes to a show a different woman, standing outside a water tank that is behind a fence.]
Woman: It's important to choose a site for a storage tank which is still accessible during floods and other hazards, and easy to access for maintenance. Fencing, padlocks and other security measures also need to be thought about. [A possum walks along the fence.]
[Shot changes to show two lids at the top of a tank. The lids are shaped like plugs, and fill the hole. The top one is labelled 'no lip', and the edge of the hole is flat. The top one is labelled 'lid with lip', and the hole has a raised edge, so the lid sits higher.]
Woman [voice-over]: Lids need to have a lip in order to prevent ingress.
[Back to the woman. The possum walks along the top of the water tank.]
Woman: They also need to be padlocked to keep intruders out.
[The possum falls into the water tank with a splash.]
[Scene changes to show a woman inside a shed. There is a pumping system against the walls behind her.]
Woman: To get water from one place to another requires water pressure. This can be achieved by using gravity pressure or by artificial pressure created by a pumping system. However, if a poorly selected pump is used, the water pressure may get too high and burst pipes, allowing pathogens into the system. Also, if the power supply fails, the water is interrupted. Fluctuations in water pressure can disrupt biofilm and resuspend any sediments in the pipe, increasing the turbidity of the water.
[Scene changes to show a man with a toolbelt in a kitchen.]
Man: Water pressure, whether created by pumps or by gravity, needs to maintain adequate pressure at the tap.
[He turns the kitchen tap on and water comes out in a strong flow, then turns it off again.]
Some pumps have the advantage in that they automatically turn on to maintain water pressure when the pressure drops – for example, when a tap is turned on.
[He turns the tap on and off again.]
Pumping systems should be selected to suit the daily needs of consumers and the layout of the reticulation system being used.
[Scene changes to show the same man outside, looking at a pipe underneath a house.]
Man: Construction materials used in the various components of a reticulation system also to be given consideration. Alkathene pipes, like these ones for example [points at the pipe], are not designed to withstand high pressures. It's also important to choose materials that will not be corroded by water.
[Scene changes to show a different man, at the computer in an office.]
Man: Backflow occurs when any water, foreign liquids or other substances flow back into a water system. I'll show you these, take a look at this [he turns on the computer].
[Shot changes to the diagram shown on the computer. This is labelled 'normal flow of water', and shows an outside tap, with a hose attached which leads up and unders the top of a water tank. The water pressure is high (20 kPA as indicated on a pressure gauge) and so the water flows up into the tap, then up the hose and down into the water tank.]
Man [voice-over]: Ok, this can happen because the pressure of the water in the system reduces and sucks the foreign liquid into it.
[The pressure drops until it gets to -20kPA, and the flow of water reverses from the tank and into the water supply. The tank begins to drain. This is labelled 'mains pressure loss'.]
Reverse flows, or backflows can be created in a number of different ways by difference in water pressures. This causes water to flow back into the distribution system.
[Back to the man.]
Man: It's not a good thing. The negative pressure can be caused by things like mains breaks, inadequate flow, undersized mains, shut downs for repairs, or the use of online boost pumps.
[The scene changes to show the woman in the shed again.]
Woman: There are many documented incidents of backflow that have resulted in sickness and sometimes even death. In a situation where the risk of backflow is identified, there are 2 real choices. Either remove the connection completely [she indicates the pump behind her] or install a method of protection such as a backflow prevention device.
The choice of the most appropriate method of backflow prevention depends on the level of risk that is identified. In order of security, the options are –
[Shot changes to show a diagram of a tap above a basin. The tap is above water level, and there is an air gap between the water and the tap. The tap is high enough above the basin that the water would overflow before it could reenter the tap.]
Woman [voice-over]: – an air gap –
[Diagram changes to show a reduced pressure backflow preventer. This equipment is shaped to fit between two pipes. There is an upstream isolating valve on the left and and a downstream isolating valve on the right. These have two check valves, and underneath the space between the two check valves there is a pressure differential release valve.]
– a reduced pressure backflow preventer, which is two spring-loaded check valves with a pressure regulated release valve between them –
[Diagram changes to show a double check valve assembly. On the left of the assembly is the inlet and on the right is the outlet. Both the inlet and the outlet have a manual shutoff valve attached. Between then are two check module assemblies.]
– or a double check valve assembly.
[Scene changes to show a man and woman standing outside a shed.]
Woman: Creating an air gap is the least expensive form of backflow prevention. This is when you have air space between outlet of the water flowing into the tank and the surface of the water in a tank – just like the cistern in a flush toilet. The air gap prevents the water from flowing uphill and forming a siphon.
[Diagram showing a tap sitting above water level over a basin. The basin is half full.]
Woman [voice-over]: You can see this demonstrated here.
[The basin fills up and the water level rises.]
When the water reaches the highest level it can [the water stops rising and there is an air gap between the tap and the water] the tap is above the water. There is an air gap.
[Back to the two people.]
Woman: Now watch the same system, but where the tap is too low or there's a pipe or hose attached to it that goes below the rim.
[Diagram showing a wap below the rim of a basin, as the water level rises.]
Woman [voice-over]: There is no air gap, and the water pressure in the system reduces.
[The water in the diagram reaches the mouth of the tap, and because there is no air gap, begins to flow backwards into the tap.]
The dirty water from the sink can be siphoned or sucked into the water system.
[Back to the two people.]
Man: Last year one of our pipes burst, so we found out where it was leaking and dug it up with the intention of fixing it.
[Shot of the man digging up an area of ground.]
Man [voice-over]: Dug it up, exposed it, and left a hole around it so we could work on it.
[Close up on the broken pipe in a muddy hole.]
Now the leak meant that the hole we dug slowly filled up with water.
[The hole around the pipe fills up. Back to the man.]
Man: We thought to ourselves that at least the water coming out was clean. What we didn't figure on was that there was a slight drop in water pressure and some of the water in the hole got sucked back into the system. [Back to the hole, where the water level drops, then to the man again.] And that water wasn't clean any more.
What's more, as soon as this water got into our tanks, we couldn't guarantee that any of it was clean any more. A total nightmare. One small backflow prevention device and more care and hygiene during maintenance, and we could have saved ourselves a whole lot of headaches. Not to mention stomach aches and diarrhoea.
[Scne changes to show a man working on fixing some of the pipes by a water tank.]
Man: Maintenance of a water distribution system is necessary to ensure a reliable and safe supply of water. As such, it's very important that high standards of hygiene are upheld during maintenance, otherwise recontamination can occur.
[He inspects a piece of pipe. Note that he is wearing gloves.]
Wherever possible, all connections should be made under dry conditions. Dirty piping needs to be thoroughly cleaned and disinfected.
Disinfection can be done using a squirt bottle [he lifts one up] of industrial strength bleach. [He sprays the disinfectant over the pipe.] Squirt the bleach all over and inside the pipe [he does so] before connections are made. Be careful though – this stuff can burn you badly if it gets on your skin.
[Scene changes to show the woman in a lab coat next to the open water tank again. The tank has green slime above the water level. The woman is holding the end of a vacuum cleaner.]
Woman: Biofilm on pipes needs to be scoured or flushed out from time to time, and the storage tanks should be cleaned periodically. One good way to do this is with a swimming pool vacuum cleaner. Alternatively, you could install a tank vacuum system. This is simply a pipe which acts as a siphon when the water level in the tank reaches a certain level.
[Shot of a diagram of a storage tank. There is a later of sediment at the bottom of the tank, and a small amount of water above that. A pipe starts at the layer of sediment, follows the tank wall and leaves at the top of the tank. It then leads back down to the ground, which is labelled 'waste water to discharge area'.]
Woman [voice-over]: The pipe, through siphon action [the tank begins to fill] sucks up and expells the water from the lowest level of the tank [the water rises above the top of the pipe, and the pipe starts draining out the side] including the layer of sludge at the bottom [the sediment also gets sucked up and expelled from the pipe].
[Scene changes to show an older man inside an office. He sits next to the woman who explained air gaps earlier.]
Man: Hygienic management of the workplace during maintenance is essential to stop recontamination of the treated water and to maintain the hygienic integrity of the reticulation system.
After maintenance, the system ought to be reconnected, then pressure tested, flushed, disinfected, and then samples taken to test for bacteriological quality. It is essential to disinfect the pipes –
Woman: And tanks.
Man: – before placing the system back in service.
Woman: After this, the pipes and tanks can be drained and filled with drinking water. After 24 hours, if the bacteriological test is clear, then you may bring the system back into use.
[Scene changes to show a man outside by a water tank.]
Man: We can't stress it enough – the respsonsibility of a small supplier to manage a reticulation system. It's really really important, because keeping the water clean throughout the storage and distribution process is as important as getting the water clean in the first place.
[Scene changes to show the man from the very beginning of the video cooking a barbeque.]
Man: Maintaining the effectiveness of the reticulation system, ensuring it is sealed and safe, that water pressure is maintained, that maintenance is done in such a way that recontamination cannot occur is important.
The reticulation system needs to be designed while keeping in mind the type and availablity of source water, and the needs of the community for whom the water is being provided.
Pressure management systems, whether by pump or gravity, and backflow prevention devices should also be chosen to suit the needs of the reticulation system.
As a small water supplier, your responsibility doesn't end with getting the water clean, but with storing and distributing clean water until the water comes out of the tap.
[Ministry of Health logo]
[Simmonds Brothers logo: www.simmondsbrothers.com]
Download Tanks, Pumps & Pipes (MP4, 39.7 MB) – right click and choose 'Save As'
Checking it out
Sampling and monitoring small drinking-water supplies – 23 minutes
This video provides information on sampling and monitoring small drinking-water supplies.
Voice-over: This DVD has been produced by the New Zealand Ministry of Health. It provides information on the monitoring, sampling, field analysis and telemetry useful in small drinking-water supplies.
Title: Checking it Out: Sampling and Monitoring for Small Drinking Water Supplies
[Animation shows a man on a skifield.]
Skifield man: It is important to know what is happening in your water supply. Monitoring allows the person responsible for supplying the water to know if, for example, the turbidity is too high, or if the UV is not working, or if there is E coli in the water.
Microbiological sampling involves taking an amount of water and trying to cultivate bacteria in the water. Field analysis involves small instruments to check FAC, pH or turbidity. Remote monitoring uses some kind of monitoring system to tell you what is happening in your water supply.
How do we know that the 3 principles are working? We need to have quality control assurance, which means that your treatment and reticulation system needs to be monitored.
[The location changes to a lake, where a different man is out on a boat. He sits next to a box with small sample bottles inside it, and has a sampling pole with a clamp on the end. He is wearing a life jacket.]
Boating sampler: When taking samples from a treatment plant or reticulation system, health and safety can be a concern and needs to be considered.
[Now he is sitting at the top of a water tower. There is a ladder against the tower.]
Safe access to sampling sites is really important. This includes entry into a confined space such as a reservoir, or a pump or valve chamber. The hazards with doing this [the ladder falls down] can include things like lack of oxygen, falling from ladders or even drowning.
[Back to the lake.]
Now, sampling source water from a surface supply such as a river, that might mean you've got to wade into the river, and so you've got to be careful about that, don't get washed away. If samples are to be taken from a lake, you may have to use a boat, and in that case you've got to make sure that you're capable of handling the boat safely. Well, a second person should always be there, just to help out if things go bad.
[The location changes to the lake docks, where a different man stands with a sampling pole.]
Lake-side sampler: There are ways of doing things and tools available which can reduce the risk of an accident. Proper training and equipment for entering confined spaces or working around water might make the difference between getting a job done and having a bad day.
[Close up on the sampling pole holding a bottle in the clamp.]
Lake-side sampler [voice-over]: The use of things like sampling poles with clamps to hold bottles on the end are helpful.
Lake-side sampler: They can remove the need to enter water that is being sampled. The most important thing is to think about the workplace risks and hazards of the things you're doing, then work out how you can reduce the risks.
[The location changes to a laboratory, with a UV light box, an incubator, and lots of flasks in the background. A woman stands behind the bench.]
Female lab worker: When taking samples, a number of things need to be considered. Firstly, you need to make sure that the sample being collected is representative of the water you want to test. The whole point of sampling is to test a small amount of water, the results of whice can tell you about the water as a whole.
For example, it is not a good idea to take a microbiological sample from the surface film on the water, where the air and water meet –
[Shot of a bottle attached to the sampling pole entering the water]
Female lab worker [voice-over]: – because things in the water here could contaminate the sample. [The bottle is dipped under the surface film of the water, and is removed once it is full.] You need to take the water from underneath the surface.
[Back the the man in the boat.]
Boating sampler: If you want to sample the water going into a treatment plant, you need to take it from the intake pipes, or as near to the plant as possible. If you're using water from a lake, sampling the water from the other side of the lake wouldn't be representive of the water going into the plant.
[The location changes to an office, where a young woman and an older man are talking.]
Older man: If you are going to sample water from within the treatment plant, you need to think about what you are trying to find out – [Woman makes agreeing noise] – what it is you want the sample to show you.
Young woman: Yeah. And if you're using UV disinfection, the inactivation of pathogens is instantaneous. If treatment involves filtration, the removal of pathogens also happens in the time of filtration.
Older man: That's right. So if you want to know if the process is effective, you can take the sample straight after the treatment process.
Young woman: However, some disinfectants need time for the process to work effectively.
Older man: Mm. If you use chlorine as a disinfectant, then a certain amount of contact time is needed in order for the chlorine to inactivate the pathogens.
Young woman: So if a sample is taken close to where the chlorine is added, the test results may show an inaccurate result. The sample needs to be taken further through the system.
Older man: Probably from the water in the contact or treated storage tanks.
[Shot of a street map, with a water treatment plant highlighted on the map. The shot pans across the map.]
Kitchen sampler [voice-over]: In a reticulation system, the water in the reticulation system is likely to be of a poorer quality than the water leaving the treatment plant. So you might want to take a sample from the very end of the reticulation system, [The map shows a highlighted household some distance from the treatment plant] maybe the household tap.
[Crossfade to a man in a kitchen with a sample bottle.]
Kitchen sampler: If you're doing microbiological sampling, it's best to sample from the extremities of the system. [He turns on the tap.] If you want to know if the water in the system is retaining its FAC, you could sample twice – once at the treatment plant, and once in the reticulation system.
[The location changes to a stream running through the bush. A woman standing on some nearby rocks, with a sample bottle hold onto a sampling pole.]
Stream sampler: Another very important problem is the potential for the person collecting the sample to contaminate it. If the person taking the sample is collecting it while standing in the water, they may contaminate the water. Bottles clamped to the end of a pole can be used to take samples in such a way [she dips the pole into the stream] that the sampler doesn't need to go into the water for microbiological sampling. [She lifts the pole up again, with a full bottle on the end.] The sample bottle needs to be sterile.
For chemical sampling, the bottle needs to be chemically clean. For some analysis, preservatives may need to be added or reagents need to be in the bottle before the sample is collected. Laboratories will provide you with the correct sample bottles.
[The location changes to a stream with a bridge running over it. A man stands next to the stream, holding a bottle with the lid removed.]
Sampler: The lid must not be put on the ground when the sample is taken, as contaminants may get on the lid. In fact the lid should be held the right way up while the sample is being taken. [The man puts the bottle into the water, and describes how he does it.]
Sampler [voice-over]: The bottle must be pushed through the surface of the water facing down, and then held towards the flow of the stream.
[The location changes to a lake, where the man holds a full bottle. He indicates his hand.]
Sampler: In this way, contaminants from the collector's hand don't contaminate the sample.
If the water is not flowing, such as in a lake, the bottle must be moved forwards to create a flow, see?
[He moves a bottle through the water and it fills up.]
Sampler [voice-over]: If you're sampling from a boat, the sample must be taken upstream of the boat.
[Shot of a bottle labelled: 14, Waikanae 6002, Resv. Outlet 14.1, 8/11, 08:46, PB.]
Sampler [voice-over]: And once the sample has been collected, make sure the container isn't contaminated by putting fingers or pH probes or anything else like that into the bottle.
Female lab worker [voice-over]: The sample must then be labelled with the details of the sample – the date and time of sampling [arrows point at 8/11 and 08:46] and the name of the sampler [an arrow points at PB].
[We see the woman in the laboratory again. She has a labelled bottle in front of her.]
Female lab worker: It is very important to discuss the samples you are collecting with the laboratory that will be doing the analysis. They should be able to provide you with written instructions on how to take each of the samples you are collecting.
[Back to the lake docks.]
Lake-side sampler: Now it's not possible to test for all the pathogens that could contaminate a water supply. So what we use is one microorganism – the bacteria E. coli – to indicate if the water has faecal contamination. If any E. coli is present, then this should be seen as an indication that the source water is contaminated and your treatment processes aren't coping, or there's a problem of some kind.
This should raise some questions – has something changed in the catchment?
[Shot of some cows crossing a stream.]
Lake-side sampler [voice-over]: Has someone moved cattle or shape through an area upstream of the intake?
[Shot of some diggers doing work next to a stream.]
Lake-side sampler [voice-over]: Has there been a landslip in the catchment that's making the water dirty? Is the disinfection system ineffective due to the turbidity?
[Shot of an exposed pipe in a muddy hole.]
Lake-side sampler [voice-over]: Is there a problem in the reticulation system, I don't know, backflow, for example?
Lake-side sampler: Should the chlorine dose be increased? Or should the whole system be shut down for a while so the problem can be found and fixed? You might even need to tell people to boil their drinking water until things are sorted out.
[Back to the laboratory.]
Female lab worker: E. coli analysis needs to be done by a laboratory, with the special equipment needed to incubate samples and grow the bacteria. Normally a water supplier will collect a sample in a sterile container provided by the lab, and then take the sample to the lab to be cultured.
There are a number of ways to analyse for E. coli. But they all involve growing the bacteria, and counting or calculating how many there are. And the number of E. coli in a sample tells you how badly contaminated the water is.
[The location changes to a shed with a water tank out the back.]
Man by water tank: Worldwide, E. coli sampling is the standard way of showing their water is safe to drink. But microbiological sampling is not the only sampling that can be done. Things like free available chlorine, pH and turbidity can tell a water supply operator a lot about their system and how well it's operating. Larger water suppliers generally monitor their system's performance by using continuous online probes testing all the time. However, smaller suppliers will generally sample manually.
[The location changes to a treatment plant, where a woman stands with lots of monitoring equipment around her.]
Treatment plant woman: Chlorine, when it's added to water supply, reacts with organic material in the water. That's how it inactives bacteria and viruses. But this uses up some of the chlorine and the chlorine that is left is called 'free available chlorine' or FAC.
FAC reduces over time. Sunlight or warm temperatures also reduce FAC. So if you're using chlorine as a disinfectant, it's important to test the FAC to make sure you've got enough to do the job.
But you need to test for FAC on site. Because if you take the sample then wait for a couple of hours to do the analysis, the results will probably change.
[Shot of a chlorine analyser that has a sample bottle inserted.]
Treatment plant woman [voice-over]: You can test FAC by using an electronic analyser with a digital read-out.
[Shot of the woman adding a chemical to a test tube of water. The water turns red. There is a chlorine tester on the bench as well.]
Treatment plant woman [voice-over]: Or using equipment that measures the FAC by the amount of colour produced when a reagent is added to the water.
[The woman slots the test tube in a free slot in the chlorine tester, so that she can compare the colour of two samples.]
Treatment plant woman: This is very similar to the method used for testing the chlorine in a swimming pool or spa pool, but much more accurate. They are pretty easy tests to do.
[The location changes to outside a building, with a small cupboard on the wall. There is a risk management plan hanging beside it, with headings like 'What could go wrong?' 'Indications' and 'Plan of action' on it.]
Risk management man: It's important to store any reagents used to do test kits according to their instructions. They need to be kept in a dark, cool place. [He indicates the cupboard.] The reagents will have a use-by date and it's important to check this, because out-of-date reagents can give an inaccurate result. So you need to throw all old reagents away.
[Shot of the open cupboard. It has some boxes and empty sample bottles inside. The man puts a box labelled 'Test kit' on one of the shelves.]
Risk management man [voice-over]: Test kits also need to be checked from time to time to make sure they're accurate. This is called calibration.
[The location changes to a treatment building. The woman who was sampling the stream stands next to some pipes.]
Stream sampler: When you get an FAC test result you need to understand and interpret it. Most likely it will confirm to you that everything is ok. But if it is high, you might need to reduce the amount of chlorine you are adding. Or if it is low, you may need to increase the amount.
Testing for FAC gives you the information you need to adjust the dose. But remember, the test is for the chlorine that is available as a disinfectant after some has been combined with organic matter, not the actual dosage amount of chlorine. The FAC should ideally be greater than 0.2 milligrams per litre of water to make sure you have enough disinfectant to control bacteria and viruses. 3 milligrams per litre of water is too high and the water will taste pretty bad.
[The location changes to an office, where a man sits at a computer.]
pH man: pH is a measurement of the acidity of water. It's measured on a scale of 1 to 14.
[He brings up a pH chart on the computer. It goes from acid (1) to alkaline (14), with battery acid marked in at 4 and caustic soda at 14.]
pH man [voice-over]: 7 is neutral, lower than 7 is acidic and greater than 7 is alkaline. Ideally, water suppliers should try to keep drinking water at a pH level of between 7 and 8 [an arrow points to this on the screen].
The level of pH is important in chlorinated supplies because a high pH reduces the effectiveness of chlorine. But if the pH is too low, the water can leech metals from plumbing fittings, which can be a health risk over time. So keeping the pH constant at about 7 is important for water suppliers.
[The location changes to a sheep farm. A man stands next to a fenced-off pipe.]
Groundwater man: Well, in New Zealand groundwaters often have a low pH of about 6 or 6.5. This is because the groundwater can have a high CO2 content [CO2 = carbon dioxide]. The pH can be increased by aerating the water – blowing bubbles through it or tricking it over a rough surface. Aeration removes CO2 from the water, increasing the pH.
Another way to increase the pH is to add lime or soda ash to the water. Sometimes the pH can be too high. This can be caused by the water flowing through or over limestone. The water picks up the calcium from the limestone and this increases the alkalinity.
[The location changes to an orchard, where a woman has been picking peaches.]
Peach picker: In some source waters, the pH is very constant and it doesn't change much at all over time. Groundwater that comes from a bore which is not affected by surface run-off generally has a constant pH. But if the water comes from a shallow bore, the pH of the water may change every time it rains. And surface waters have pH that sometimes changes quite rapidly. Mostly, New Zealand source waters have a low pH.
[The location changes to some fenced-off water tanks. The woman from the treatment plant kneels next to the tanks with her testing equipment.]
Treatment plant woman: You can test pH with a similar kit to the chlorine test kits. [She adds a drop of liquid to the water in a test tube, and the water changes to pink.] A reagent is added to the water [the tube is added to a pH tester so that its colour can be compared to the example] and the change in colour is compared with a colour chart.
[Shot of an electronic pH analyser.]
Treatment plant woman [voice-over]: You can also get an electronic analyser with a probe that you put in the water, and it gives a digital read-out.
Treatment plant woman: Just like FAC testing, the sample needs to be testing in the field just after being taken because sunlight and time affect the result.
[The location changes to a treatment plant. A man stands next to some canisters with 'Danger: chlorine' printed on them.]
Treatment plant man: If pH tests show that the water doesn't change you can reduce the pH tests to as low as 1 a year. But if the pH of the water changes, you need to test it to get an idea of what the range of variation is and what causes the changes. If you're using chlorine you need to monitor the pH to ensure the chlorine continues to be effective.
[The location changes to a car. The man who was describing how to store reagents is driving through the bush.]
Risk management man: The temperature of water can be important in treatment processes and sampling. Microbiological samples need to be analysed as soon after they have been collected as possible – within 6 hours. While they're being transported to a lab, you need to make sure they don't get too warm, or any bacteria in the sample may multiply. The best thing is to try and keep the sample at the same temperature it was when it was collected, or a little cooler.
[Shot of a little chilly bin on the backseat.]
It's good to carry the samples in a chilly bin with a cool pad in it. This should keep the temperature between about 4 and 10 degrees.
[The location changes to outside a shed. The lake-side sampler and the young woman from the office meeting and the man from the lake pier stand together.]
Lake-side sampler: In some water treatment processes temperature can be important. So if the water is too cold, the process happens very slowly. What it means – what it may mean is that in winter, when the water is colder, the flow rate through the filter may need to be slower. And chemical reactions, they're affected by temperature as well. They go faster when the water is warmer.
[The location changes to a water treatment plant.]
Young treatment plant woman: In water treatment plants using UV or chlorine to disinfect the water, dosages may need to be adjusted according to the temperature of the water. In warmer water the disinfection becomes more effective and in colder water it's less effective. And with chlorine the temperature could also affect the contact time that's required. So the most important thing about water temperature is to know what it is at different times of the year so you can understand how it might affect your treatment processes.
[The location changes back to the stream with a bridge over it. The man from the sheep farm, is doing some sampling there. He holds a thermometer and a cup.]
Groundwater man: When you're testing the temperature of source water or water in a water treatment plant, it's best not to put the thermometer into the actual water. If you're using a thermometer and it breaks, it'll release mercury into the water. But also, if you're using a temperature probe, you want the water to be still, not flowing.
The best thing to do is to take a small amount of water into a container and test this. [He puts the thermometer into the cup.]
[The location changes to thw water tank. A man stands outside with a sample bottle and a portable turbidity meter.]
Turbidity sampling man: A turbidity test tells you how dirty the water is, that is, how much suspended material is in the water. It's measured in units called nephelometric turbidity units or NTUs.
This analysis can be done with a portable turbidy meter. [He puts the water sample into the turbidity meter.]
To test turbidity, you take a sample of the water and put it into the turbidity meter. The instrument measures the turbidity by shining a beam of light through the water and measuring the intensity of light that passes through.
[The location changes to a stream. A woman holds several sample bottles.]
Turbidity sampling woman: These instruments are pretty sensitive. They measure differences in turbidity that you couldn't see with the naked eye. For example, by looking at a number of different samples, you wouldn't be able to tell the difference between 10, 1 and 0.1 NTU. But 0.1 NTU would be very good turbidity for drinking water. 1 NTU would be only just good enough, and 10 NTU would be considered unacceptable.
A normal clean-looking river would be about 10 NTU [the stream gets higher and turns brown] but a dirty river in flood could be up to 5000 NTU.
[The location changes to a laboratory, where an older man stands. He has a German accent.]
German man: It's difficult water for protozoa, so turbidity is often used as a substitute for protozoa testing. The idea is that if the water has low turbidity, say less than 0.5 NTU, there is very little risk that it will contain protozoa cysts. The more turbidity, the more chance of protozoa.
[Back to the shed, where the lake-side sampler is now by himself.]
Lake-side sampler: Measuring turbidity is a good way of knowing how well your treatment system is working, because it tells you how clean the treated water is. Some water supplies actually automatically turn off and alert and operator if the turbidity of the treated water gets over a certain amount.
[The location changes to another laboratory. An older woman has her turbidity meter and other measuring instruments plugged in to the wall.]
Older woman: The instruments used to measure the water quality, like any other equipment in a water supply, need to be maintained on a regular basis, otherwise they could give incorrect information about the quality of the water. The instruments need to be calibrated from time to time.
Calibration is the process of comparing the results the instrument is giving to a known value, a reference standard or a laboratory test.
[Back to a water treatment building, where the man ho was out testing turbidity and the younger female lab worker in a water treatment building are holding testing instruments.]
Turbidity sampling man: For example, to test if an FAC test kit is still accurate, we could ask someone from a laboratory to come out to the treatment plant and test a sample at the same time we take a sample. We can then compare results.
If our instrument is not reading the same as the lab sample, we can then make a change to the instrument. Another option could be to send the instrument away to a lab or the instrument supplier for calibration.
[Back to the lab with the older woman.]
Older woman: How often you need to calibrate each instrument will be outlined in the instrument manufacturer's instructions. However, if your instrument has been identified in your PHRMP [water safety plan] as being critical, then you may wish to do the calibration more often.
[The location changes to a computer lab, where a man and a woman sit together.]
Computer lab man: Telemetry means to measure from a distance. So telemetry is an electronic system which monitors the apparatus at the water treatment plant and lets the supplier know what is going on at the plant without them having to travel to the plant.
Telemetry usually uses something like a wireless system or the cellular network to let the supplier know if their turbidity is too high, or if their FAC is too low, or other information like that.
[The location changes to an office, where a man sits. He has an American accent.]
American man: A slightly more advanced usage of it is to give you early warning of something that's going wrong. For instance if you're going to run out of water, it would be nice to know about it before some irate person calls you up and says, 'I've turned the tap on and nothing's on.'
[Back to the kitchen. The lake-side sampler and the young woman from the water treatment plant stand together.]
Lake-side sampler: You can get information about just about anything using telemetry. It's just a case of connecting the instruments, like a turbidity meter, up to the system.
Younger treatment plant woman: Yeah, but you need to think about how much information you need. Like do you want to know if the turbidity is over a certain level, or exactly how high it is?
Lake-side sampler: And do you need to know just that the UV system is not working, or do you need to know the level of transmittance?
Younger treatment plant woman: What about for small drinking water supplies?
Lake-side sampler: Well, probably the most helpful use of telemetry is to just have a simple alarm to let you know that something's gone wrong.
Younger treatment plant woman: That's right. And if you set up the treatment plant so that it shuts down if the chlorine runs out, or the turbidity gets too high, then a pager can let you know that there's a problem.
Lake-side sampler: Yeah. And then you can just run down to the treatment plant and see what's going on.
Younger treatment plant woman: And if you've got enough storage then you can keep supplying water while you get things fixed.
[Back to the computer lab.]
Computer lab woman: The water supplier needs to have a system for their particular situation, and a system to give them the type of information that they need. For small suppliers, a simple alarm to let the person responsible know if something has gone wrong can be very helpful, and make sure that they don't provide water that's not safe to drink.
[Back to the skifield, where the man from the start of the video is standing with a drink.]
Skifield man: If you are responsible for the supply of safe water, it's essential that you know what is happening in your water catchment area, in your treatment plant and in your reticulation system. If, for example, heavy rain adversely affects the turbidity of your water, your UV system may not be able to operate to its capacity and pathogens may be getting through the treatment plant and into your reticulation system.
In other words, the small provider – no less than the large treatment plant – needs to have quality control. And for quality control, the water supplier needs to know what is happening at each stage of water collection, water treatment and water distribution. This means that the water supply needs to be monitored at all stages from source, to treatment, to tap supply.
[Ministry of Health logo]
[Simmonds Brothers logo: www.simmondsbrothers.com]
Download Checking it out (MP4, 270 MB) – right click and choose 'Save As'
When it all hits the fan!
How outbreaks can occur in small drinking-water supplies – 10 minutes
This video demonstrates how outbreaks can occur in small drinking-water supplies.
Title: When It All Hits the Fan! How Outbreaks Can Occur in Small Drinking Water Supplies
[Animation shows two trampers out in the bush. Birds are singing in the background. The two trampers get to a clearing, where someone has set up a tent.]
Female tramper: This looks like a great spot to camp for the night. There’s somebody already camping.
Male tramper: Yeah, I’m so ready to stop.
[They enter the clearing to talk to the man already camping there.]
Male tramper: Hi, I’m John, and this is my partner Sally.
Camper: Hi, I’m Nigel, nice to meet ya.
Sally [standing in front of a stream]: Hey, isn’t it great to live in a country that’s so clean? Not like other countries, where they have cholera in their rivers. Here you can drink straight out of the river.
Nigel: It’d be a brave person to do that. A lot of people think that, but it’s not true. Our streams and rivers can look really clean, but it’s not always safe to drink unless you bring it to the boil. You get some water, I’ll light the fire and we’ll have ourselves a cup of tea.
[Sally scoops some water into a billy, and puts it over the firepit.]
Sally: So, what kinds of bugs and germy things are in there?
[Nigel lights the fire.]
Nigel: Well, you’ve got a number of things. For example there are bacteria, which are tiny single-celled organisms. [The image zooms in on the water in the billy, and we see two pink cartoony bacteria.
Bacteria 1: It’s not fair bacteria have got such a bad name. A lot of us are actually really good for humans.
Bacteria 2: Yeah, it’s just a few who spoil it for the rest of us.
[Another bacteria appears. It is red, has horns and a pitchfork.]
Bacteria 3: What? [It coughs] What, what are you looking at?
[We go back to Nigel.]
Nigel: Then there are protozoa, which are also single-celled organisms, but they’re a lot bigger than bacteria.
[Back to the water, where there are two protozoa. The water is starting to bubble.]
Protozoa: Are you feeling hot, or it is just me?
Sally: Well, they’re still too small to see with the naked eye though.
Nigel: Oh yeah, they’re microscopic. But even smaller than bacteria are viruses. [Back to the boiling water, where two viruses are attached to the side of the billy.]
Virus [sounding pained]: Don’t know how long I can hold on ... ooooooooohh [it gets boiled off the side of the billy].
Nigel: They can be quite hard to kill.
Sally: Wow. You’re quite the expert, aren’t you?
[Back to the campfire. Sally and Nigel are sitting down while John is hammering in tent pegs.]
Nigel: Well, I should be. Part of my job’s keeping an eye on small water supplies around the region.
Sally: Shame you weren’t with us on our last holiday. It was a disaster.
John: Yeah, it wasn’t our best holiday. It was our midwinter ski trip – Sally and me and our two daughters. [Flashback to Sally and John in the car with two girls in the back, leaving home for their trip.] We usually meet up with some friends once a year.
[Back to everyone by the campfire.]
John: Yeah, the first thing I heard something was wrong was when I was standing in the queue for the lift, the ski lift, and ah – two instructors in front of me. One of them said to the other one –
[Flashback. Up on the mountain, two ski instructors are waiting in the queue for the lift.]
Instructor: Are you sick yet? Coz just about everyone else I know is.
[Back to the campfire.]
John: Um, so that’s when I first got an inkling that there might be something wrong.
Nigel: Oh, this is last July at the local ski field.
Sally: Yeah, that’s right.
Nigel: Yeah, I was part of the team that got called in. That was quite a bad outbreak.
Sally: Bad is the word. We’d been skiing all day, and were at the minigolf later in the evening – [Flashback. On the minigolf course, one of their daughters is looking a little queasy.]
And my daughter was feeling fine one minute [the other people on the course are looking at her], and then she threw up on the course– [everyone’s faces fall]
John [muttering]: Which wasn’t a good look.
[Back to the campfire.]
Sally: Mm. And that was when the illness started in the children.
[Flashback. Their daughter is in bed with a thermometer in her mouth. Sally checks how hot her forehead is.]
John: My other daughter didn’t throw up, but just felt a bit off-colour and had a bit of a temperature one night.
[Back to the campfire.]
Sally: And I was worse. I had diarrhoea, vomited a couple of times, and then had diarrhoea for about 7 days. [She covers her mouth like she’s embarrassed.]
Nigel: Oh, bad luck. I suspect you probably had cryptosporidiosis or a camphylobacter infection, rather than, or rather than norovirus infection, which I suspect is what you and the kids had a touch of, John. A norovius infection usually goes away after a couple of days.
Sally: One of our friend’s children was also really really crook. She had a full night staying up and vomiting, high fevers for two and a half days.
Nigel: Again, that sounds like norovirus.
John: We heard later it was something in the water. You could buy bottled water– [Flashback to John filling his bottle at the water cooler, with his girls waiting in line behind him] –but it was quite warm in the cafeteria, so I just kept filling my bottle from the water pump [End flashback] – you can only drink so much coffee before you get the jitters. And the kids did the same.
Sally: Anyway, next morning was when I started feeling really sick, so we didn’t hang around. That was the end of the holiday for us. And I really don’t want to talk about the trip home.
[Flashback. John and Sally are watching TV at home in the evening. They look a bit miserable. The TV screen reads ‘Newsflash’ and then 'Ski field health scare’.]
John: Apparently there were quite a few people sick like us. I saw it on the news.
[Back to the campfire.]
Nigel: Yeah, I actually had a big part of that investigation, probably just after you guys left. We started getting information from local GPs, and they were seeing an increased number of people with gastro-like problems. So I raced up there to check it out. It was a bit like trying to solve a whodunnit.
[Fade out, then to a car pulling up on the road.]
Nigel [voice-over]: It was 11 am. I was the first investigator on the scene. [We see Nigel on the skifield, with the chairlift in the background. Nigel is taking notes and dressed up like a stereotypical private investigator.]
Immediately, I could see something was wrong. [In the background, one of the skiers on the chairlift throws up. The scene switches to Nigel inside, talking to the manager in their office. There is a box of disposable gloves on the manager's desk.]
I met with the management and suggested first off that the cleaners wear gloves to protect themselves [Nigel lifts a glove out the box, while the manager twiddles his thumbs] and clean up any mess with a diluted bleach solution. [He wags his finger at the manager.] I didn’t want the cleaners to become sick too.
[Back to Nigel taking notes outside on the skifield.] Whatever it was, the cause had to be identified and neutralised as soon as possible. Here were my chief suspects. One, [we see someone shaking hands with another person, and germs from the first person’s hand moving over to the second person’s] person-to-person spread through inadequate hand hygeine, particularly around toilet facilities.
Nigel [on the skifield]: I can’t stress enough how important it is to wash hands thoroughly after using the toilet and before preparing food. [We see someone eating a sandwich with germs on the sandwich, and germs around the person’s mouth.]
Nigel [voice-over]: Two, a large food outbreak associated with one of the cafeterias. [We see someone drinking a glass of water with germs in it, and swallowing the germs.] And lastly, the water supply.
[Back to Nigel on the skifield.]
I continued the investigation. Here’s what I knew: [we see a map of the skifield, with red Xs popping up at various places] people from a whole range of different sites on the mountain were ill.
[A bunch of Xs pop up on the main buildings] People who had eaten at the main cafeteria were ill. But people who had eaten different kinds of food were also ill [Xs pop up on one of the smaller buildings] and some people brought their own food with them [Xs pop up at the carparks].
[Back to Nigel on the skifield.]
It immediately looked like it wasn’t going to be a food problem, coz you couldn’t explain all the illness based off some food exposure. [Nigel crosses ‘Bad Food?’ off in his notebook.] It was much wider than that.
[Back to Nigel in the manager’s office.] The management assured me there’d been no water issues, and no problems with sewage or anything like that [Zoom in on the manager, who is starting to sweat] so I didn’t suspect the water supply.
[Back to the skifield, where Nigel crosses ‘Water Supply?’ off in his notebook.]
[Nigel looks at a bathroom tap through a magnifying glass.] I was busy following some hand hygiene leads but it was getting nowhere. [He looks away from the tap, like he suspects something.] I smelled a rat. It just didn’t add up.
Nigel [on the skifield]: I decided to go pay the management another little visit. [Nigel knocks on the manager’s door.]
Nigel [voice-over]: This time they came clean. [Inside the office, the manager looks despondent.] Turns out they actually had had problems with the sewage. Here’s what happened.
[We see a map of the mountain top, showing a lake, a stream, and the location of the top ski hut.]
There was a lake further up the mountain, which was the lake they drew the water from. [Arrows appear indicating the movement of water from the lake to the ski hut, draining the lake.] However, there wasn’t much water in the lake this season, so they’d started also using water from the stream [arrows indicate the water being taken from the stream] that ran down the side of the mountain.
[We switch to a view of a pipe running underground.] It was around this time that a soft drink can became lodged in the sewage system [a can falls down the pipe and gets stuck in a bend], causing the whole thing to overflow down the valley [sewage begins to flow into the pipe, but gets stuck behind the can and backs up] and into the stream they drew their water from.
Nigel [on the skifield]: I explained it wasn’t a good idea to have the sewage treatment system uphill from the water supply, where it could flow into the water used for drinking if anything went wrong. I think they learned their lesson. And for me, it was another mystery solved [Nigel winks and does a thumbs up. Back to the campfire.]
John: That could be quite serious, couldn’t it? Withholding that kind of information.
Nigel: Yeah. They could have been prosecuted for not fully cooperating.
Sally: The ski operation was closed for a day, wasn't it? [We see the road that heads up the mountain to the skifield. The road is empty.] Which, you know, you can imagine how much money was involved in doing that. [Moving backwards down the road, we see two ‘caution’ tapes in an X shape behind a ‘closed’ sign.] So they certainly must have suffered financially.
[Back to the campfire.]
John: And they also suffered in terms of reputation, because once this thing got out into the media– [we see a newspaper with a big headline reading ‘Ski field not safe!’] –it was as big as Ben Hur.
[Back to the campfire.]
Sally: It’s a bit of a worry, isn’t it? Makes you wonder how much of our drinking water is actually safe.
Nigel: Well, in this country, drinking water is usually safe. Most water supplies in medium and large cities have safe water. Small water supplies around the country may not be so safe though. This includes water for camping grounds, small rural communities, sports clubs, marae, that sort of thing.
[We see a fenced water supply out near the bush. A possum walks along the top of the fence.] It doesn’t take much for a water supply to become contaminated.
John: One dead possum in the water tank ... [The possum gets to the top of the water supply and falls in.]
Nigel: Yeah, yeah, can make a lot of people very sick. [Back to the campfire.] Outbreaks often occur when a combination of things go wrong. The source water is unusually dirty and the UV light has failed or the chlorine has run out. Sometimes one thing could be anticipated, and one isn’t.
[Flashback. A rural school.] We had a situation a while back. [The school bell rings, but there are no students.] Most of the students at a country school had been laid low by some kind on infection. [Back to the campfire.] A nasty diarrhoea-type illness. [Inside one of the classrooms, there are only two students and a lot of empty desks.] It only came to our notice because a school nurse contacted the health authorities to find a safe way to clean up a lot of vomit.
[We see Nigel investigated a pipe outside the school building. This time he is dressed in his lab coat.] I was part of the investigation team that got sent to the school to have a look at the environment. You know, where the sewage discharge went [we see another investigator looking at the water supply] and also looked at the drinking water system, [another investigator is inside looking at the kitchen tap] kitchen. [End flashback.]
Sally: How did you test the drinking water supplies? Did you just go to a tap and–
Nigel: Well, yeah, it was quite a few samples. We did what we call ‘E. coli’ testing. E. coli isn’t usually harmful in itself, but if E. coli’s found, it indicates there’s faecal matter in the water.
[Flashback. The investigator who’d been looking at the water supply is in the lab checking at a bunch of samples. She shakes one of the samples and it turns yellow.]
Sure enough, we found E. coli [zoom in on the sample, to show a happy pink wiggly germ] which showed us that treatment had failed and pathogens were getting through into the drinking water. [End flashback.]
John: How did the treatment fail?
Nigel: They had a UV treatment system, and there was a lot of organic material coming off the swamp. Lots of suspended particles, which made the water cloudy. Without filters before the water got the UV, it was wasn’t able to work very well.
[We see an image of the UV system, which puts rays into the water. One germ gets zapped by the rays and dies.]
Pathogens can sort of hide behind large particles [another germ comes along, but it is behind a particle of something ] and so don’t get zapped by the UV light. [The particle gets zapped, but the germ survives. Another one comes along without a particle to hide behind and does get zapped.]
And then we found out later that the previous week [the UV light turns off and the germs get through unharmed] the light had blown a bulb.
[We switch to the school caretaker on the phone in his office. He looks pretty slack – he has his feet on his desk and is watching TV while he talks.]
Caretaker: Ah, I think the UV bulb has blown. Nah, I’m not sure what size. Hold on, I’ll have a look.
[Back to the campfire.]
Nigel: And a new bulb had arrived a couple of days later and he put it in – and in the interim had done nothing else. So it wasn’t what you would call good water management. Certainly not the way to do it – even if he had chlorinated the water in the interim it might’ve addressed most of the problem. They needed a contingency plan. If the main disinfection system fails, then do something else. Waiting around for a new bulb isn’t enough.
John: So what was actually contaminating the water?
Nigel: A neighbour was grazing cows around the water source. I think he even took cattle down to the swamp, which drained down into the school’s property. They didn’t know what they were drinking. [Shot of a cow in a paddock, pooing on the grass. The poo flows down across the grass.] If they’d’ve done some monitoring, they would’ve found out.
Sally: Yuck, that’s disgusting.
Nigel: Yup. So now they’ve got back-up UV lights and a new generator in case the power fails. And I hear they’ve got a new caretaker.
John: Yeah, I suppose you’ve gotta take care if you’re a caretaker [laughs]. Tea everybody? [He holds out the billy.]
Everyone: Cheers! [They clap their mugs together.]
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