At MMTC-PAMP, my project involves coming up with a strategy to provide safe drinking water to villages that have very limited access to quality water. Over the past eight weeks, I’ve learned more about water than I ever thought possible. Everyone has heard that the human body is around 60% water and that the ground is a great source for freshwater. Here are some things I’ve learned this summer:
1. More than just H2O
100% distilled water is not safe for drinking. In fact, the water we usually drink contains plenty of dissolved compounds: calcium, magnesium, chlorine, fluorine, sulfurs, and other organic compounds. Chlorine is often added to tap water to kill harmful bacteria while fluorine is added to prevent tooth decay. Our bodies need minerals to function, and drinking water is a great source. In fact, drinking “soft” water, water low in calcium and magnesium salts, has been correlated increased morbidity and mortality from cardiovascular disease.
2. So many parameters
The World Health Organization and Indian government have both outlined a long list of biochemical parameters that drinking water should follow. A detailed water analysis report, like the ones that MMTC-PAMP’s ecology lab creates regularly to test its own drinking water, measures water for all of these chemicals to ensure that it falls between the recommended ranges. Who knew that water was so complicated?
3. Access vs. quality
Providing access to water and ensuring quality of water are two separate but highly related issues. In Mewat, the district that MMTC-PAMP is located, both access and quality are large issues for the majority of the population. Recently, when I asked a villager whether or not he thought drinking water from various sources was safe to drink, he replied, “Why should I even care about how good the water is when I don’t even have any water to drink?” Wells in Mewat often run dry, and the government tap water supply is highly irregular and often shuts down because the residents don’t pay their water bills. As a result, many villagers have resorted to purchasing water from private tankers, nicknamed the “Water Mafia” who illegally pump water from nearby wells and sell it. Although this solves access, it far from solves quality: 90% of the tankers supply unpotable water. Any solution that is designed must address both access and quality.
4. Dirty water can make you sick
Impurities in the water we drink can cause many illnesses. Most notable are water-borne diseases like rotavirus, the most common cause of diarrhea, cholera, and hepatitis A; but there are also many other illnesses caused by nonmicrobial impurities. Groundwater is often contaminated with high levels of fluorine, lead, or arsenic. Too much fluorine can cause fluorosis; lead can cause lead poisoning leading to learning disabilities; and arsenic can cause arsenic poisoning. While human actions can contaminate groundwater through the use of fertilizers or leaking sewers, soil composition can also drastically affect the composition of groundwater.
5. Sweet or Salty
How would you describe to someone what water tastes like? Water just taste like…. water. Measuring water’s total dissolved solids (TDS) is one of the easiest ways to get a broad sense of how contaminated it is. TDS simply measures how much stuff is present in the water. While this could be simple salts, poisonous lead, or E. Coli, TDS is a very simple metric that’s often used. In a lab, TDS is measured using a conductivity meter, but our tongues are also great at differentiating between very subtle differences in salt concentration. This is why when we asked villagers how bottled water tastes, they all exclaimed that it’s sweet. Compared to Mewat’s unpotable groundwater, whose TDS varies from 1000ppm to 7000ppm, bottled water tastes as sweet as gulab jamun. For comparison, seawater has a TDS of around 30,000ppm.
6. The ground purifies but don’t dig too deep
Mewat really struggles with this. Groundwater is usually a great source of drinking water. Soil acts as a natural filter, so by the time water reaches a natural aquifer, many microbial impurities are removed. However, if the groundwater table isn’t replenished by rainwater as quickly as it’s depleted, the water table falls. And the deeper you go, the saltier the water gets. Not only are villages in Mewat struggling to afford more powerful, more expensive pumps that get access the deeper groundwater, but the water that they pump from such depths is saltier, way above the WHO’s recommendations.
7. One filter doesn’t fit all
Water can be filtered a number of different ways, and several highly specific filters have been designed. Slow sand, rapid sand, multimedia filtration, activated carbon, Birm media, RO, UV disinfection, and many many more are often used in series to fine tune the composition of water. One size definitely does not fit all, and the filtration system for a particular village needs to be designed for the particular input water. For example, Birm media is only included if the raw water has a high concentration of iron, and RO is only required if the raw water has a high TDS.
8. Reverse osmosis
Osmosis is indisputably everyone’s favorite process, second maybe only to the Calvin Cycle1. Water naturally moves from areas of low concentration to areas of high concentration. Reverse osmosis is a process where water with high TDS is pressure pumped through a selective filter so that the opposite happens: water flows from high concentration to low concentration. As a result, water with high TDS can be converted to water with lower TDS and some wastewater. Because Mewat’s groundwater has such a high TDS, RO filtration is essential.
1 Definitely not sarcasm