Science Unlocked: How do you clean water?

DW (English)

Edith Kimani wants to find out: Is it possible to turn polluted water into drinking water just using DIY filters?

Transcript

00:00How safe is your tap water? I mean, do you trust it enough to drink it? I don't.

00:04Which is why I have to buy drinking water. And most people in the city of Nairobi do.

00:09I mean, there are places in this country and other parts of Africa where you can find safe

00:14filtered drinking water, but not here. So today I want to do three things. How safe is tap water?

00:20Now the second thing I want to identify is if I can make this water drinkable. Can I actually

00:25make it safe? And how? So that's step number two. How do you like my handwriting by the way?

00:30And finally, we need to test our results. So we must test in a lab. But first, let's quickly

00:38understand where our water comes from. Nairobi sources most of its water from nearby dams,

00:44as well as some groundwater reservoirs. The problem is that the city doesn't supply enough water,

00:50which means that extra water is supplied through water trucks, boreholes, or water cellars. It also

00:56means that pipes, which in some cases are old and leaky, are also illegally tapped and damaged.

01:02The result is we have no idea how clean the water coming out of our taps actually is.

01:08All right, it's time to do some experiments. I've got a jar here, which I want to clean first with some

01:14rubbing alcohol, just so that it's completely clean and decontaminated. All right, that looks pretty clean

01:21to me. One of these samples will have the tap water and the second sample will boil that water for about

01:26a minute or two. And when we take the samples to the lab, I'm very curious to see if there's going to

01:31be a noticeable difference. So let's go fill this in. We've got our first sample of just tap water.

01:39We've not done anything to it. And our second sample of boiled water is actually still a bit warm.

01:46Nice. And for our third sample, we took raw river water. So I'm just going to hold this here. Oh,

01:51you can see that. All the floating goodness in there. We'll collect some of this water and filter it

01:59and boil it and take it to the lab and see if there's going to be a significant difference between

02:03our first sample, second sample, third sample. And of course, we're going to have a fourth one.

02:08Let's get filtering. What types of pollutants might we find in water here in Kenya? Microbial

02:15contaminants, bacteria and viruses from human and animal waste, heavy metals such as lead and mercury

02:24often found in industrial runoff, pesticides and chemicals from agricultural activities that seep

02:31into water sources. All of these pollutants have a negative effect on our health, either in the

02:36short term or long term. That's why we don't want them in our water. I've put together everything we

02:43need for our DIY filter. You're going to need a container to collect your filtered water. This

02:47funnel, a cloth that's going to come right here, a rubber band, some sand, charcoal and gravel. So you

02:54take your piece of cloth and you attach it to the bottom here. Then we start layering the filter.

02:59Now we're mimicking what already exists in nature. So we start with sand, charcoal. Then we're going

03:05to need some more sand, more charcoal. Now it looks something a little bit like this. And then we take

03:11a little bit of the gravel. And finally, we've got our raw river water. The whole point is to see if

03:17this can look a little better after it's gone through our filters.

03:20The filtered and boiled river water. They're now ready to be taken to the lab and see what the

03:32scientists say. Hi Dinesh. Hi. Thanks for, oh wait, I forgot something. Oh, much better. We're going to be getting to these

03:42questions in a little while. We did send you a couple of samples about a week ago. I'm guessing

03:47you have the results. We do. Let's go to the tap water. Is there anything from our tap water sample

03:53that we should be concerned about? Of course, yes. Of course, yes. According to the results,

03:58the recommended pH should be between 6.5 to 8.5. But as you can see here, the pH is 8.82.

04:06That really makes it unfit for consumption. What happened then after we boiled our water? Could

04:12we have fixed that? Fortunately, I can see, yes. The results show that after boiling, the pH

04:19level reduced to allowable limits. 8.43. 8.43. Wow. So just on the edge. Just on the edge. But that's

04:27really good news that just a simple thing as boiling your water can already eliminate something

04:33like, you know, alkalinity in your water. Then we have the raw river water. There are a number of

04:39parameters and very serious ones to say that have indicated this water was not fit for consumption.

04:45We realized that there were several, several microbes in this water, both with pathogenic and

04:51non-pathogenic and the number was huge. We went ahead and checked a parameter called E.coli. If you find

04:57your E.coli in water, it indicates fecal contamination. Fecal contamination could be from

05:03sewer, from mammals, from people, from birds. When they grow, there is a substrate that is broken down

05:11and therefore that substrate makes the E.coli bacteria to appear greenish blue because it has got a unique

05:18enzyme. Sorry, I can't get over how awful it looks. It just looks like a disease. And we went ahead and

05:26checked Staphylococcus aureus. What is Staphylococcus aureus? It sounds very good in the mouth.

05:31It sounds a sweet name, though not very interesting to interact with. Okay. They are always very

05:39resistant to even antibiotics sometimes, some of them. So this Staphylococcus, as we can see,

05:44it was present in this water and for its case, it should not even be present at all. Even presence

05:51of one indicates the water is not fit for consumption. Okay, so let's move on to our fourth and

05:56final sample. I'm very curious about this because I thought that having filtered and boiled it, it would

06:01look a little better. From the look of things, it doesn't look great, but the results indicate

06:06otherwise. With regard to microbial parameters, it indicates that everything is okay. Would you drink it?

06:13Until I check for the chemical parameters. Okay. This river water indicates that there are high levels

06:20of manganese and fluoride. So therefore, it's not fit for consumption. I thought fluoride was good

06:27in water because of its benefits for our teeth or am I misinformed? No, everything to a given level

06:36becomes a poison, you know. Right. Yes. So everything above a given threshold becomes unfit. Okay.

06:42All right. So what have we learned from our little DIY experiment today? Well, the first thing is that

06:47despite looking very clean, tap water isn't always safe. This one we learned did not have any pathogens,

06:53but something as simple as a pH can disqualify it from being safe. So good to note. However,

06:58we also learned that doing something as simple as boiling the water can bring it up to safety

07:03standards. What else did we learn? That our waters here in Nairobi are in a sad state and that they

07:09contain all kinds of contaminants from microbes to chemical ones. We did also see though that combining

07:16our different methods of filtration and boiling can significantly improve the quality of water,

07:21making it perhaps not safe for consumption, but for other uses. So tell me, what are the experiments

07:26do you want us to do for you? We really enjoy doing this. So thank you for watching and see you next time. Bye-bye.

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