Rural Drinking Water Solutions
By Li Ling 14 July, 2015
Ling Li outlines how & which Point Of Use (POU) system is best to deliver safe drinking water in rural areas
WHO claimed that the world has met the Millennium Development Goal target of halving the proportion of people without sustainable access to safe drinking water in 2012, but there are still 783 million people living in rural areas lacking safe drinking water.1 This means that more than 783 million tonnes of safe drinking water is needed to be produced to solve this problem (assuming one person drinks 3 L of water every day).
In three countries, Bangladesh, Benin, and Cambodia (covered in a report by the World Bank), 46 million people lack access to clean water. The problem costs these countries 0.2–0.7 percent of gross domestic product (GDP) a year—at least US$275 million in total.
“… the main enemy against safe drinking-water is about two dozen infectious diseases predominantly caused by fecal microorganism contamination of the water source.”
For those people, the main enemy against safe drinking-water is about two dozen infectious diseases predominantly caused by fecal microorganism contamination of the water source.3 The minimum infectious doses for average healthy adults range from just a few organisms for Salmonella typhi (typhoid causing bacteria), to several hundred organisms for Shigella ﬂexneri (dysentery-causing bacteria), and to several million cells of Vibrio cholera (cholera-inducing cells).4 These doses are signiﬁcantly lower for infants and small children than for the general adult population.4
Moreover, there still exists a big question mark on the water qualities provided by existing wells with pumps, and how long those existing facilities could provide uncontaminated drinking water.
Chinas’ solution is not suitable for all due to high costs & energy demands
A big step taken by the Chinese government is connecting every rural village with sophisticated water distribution systems. Despite the apparent advantages a water distribution system could bring, there are many downsides it might encounter. The high construction investment of a water distribution system, the great amount of energy required by the pumping process, and the high maintenance cost will limit the wide application of this approach around the world. Even if all those problems are solved, almost 40% of water brought to the household will be used for toilet flushing, which is a huge waste. Not to mention that a water distribution system with proper maintenance could have 10 to 20% leakage.5 More importantly, it could bring secondary biological or chemical contamination if the distribution process is not well designed or monitored.6
The high maintenance cost of China’s water distribution system will limit its global application
Point of Use systems (POU) offer the best solve
In many other places, to consider building up a drinking water distribution system unless all the problems mentioned above (but not limited to) could be well tackled. In those places, chemical treatment like chlorination is not feasible since people cannot handle the process safely, while physical treatment like UV disinfection is not feasible either since no electricity is provided. Therefore, the very traditional way of a point of use (POU) system in treating water is boiling. But boiling becomes a less favored option since the process takes time and is limited by the availability or affordability of energy sources.4 Besides, the high energy requirement and low energy efficiency in boiling water also contribute to global warming.
Point of Use systems are the best way to go but price can be an issue
Another practical option is filtration. A report written by TECHNEAU on “International Market Survey on Membrane-Based Products for Decentralized Water Supply” introduced three types of POU systems.7
- Ceramic POU systems: One of the manufacturers (names can be found in the original paper) provided POU systems with a good consistency in the produced water quality but an extremely high price of about 200 USD for a 4-member family living in low-income economies. The price is about 20% of their annual income.8 Two other manufacturers (names can be found in the original paper) provides POU systems with lower consistency in the produced water quality but a lower price of about 80 USD for a 4-member family living in low-income economies. The price is about 8% of their annual income.8
- Reverse osmosis POU systems & Ultrafiltration POU systems: These two systems are mainly made of plastic, which is less vulnerable than ceramic when falling on ground or dashing with other things. However, both of them, as sold by the manufacturers, provide better water qualities at a price of twice or 3 times of the ceramic POU systems.
Price is a major factor which determines if a system is successfully applied in rural areas
This shuts the door for the reverse osmosis
One could say that the major factor determines whether a system could be successfully applied in rural areas is the price, which immediately shut the door for the reverse osmosis POU systems and ultrafiltration POU systems. It might be true for the reverse osmosis POU systems, since the system provides unnecessarily high water quality resulting in high capital and maintenance cost due to fouling caused by natural organic and inorganic compounds.
Ultrafiltration POU systems provide best filtration and price balance but are not a fix all
However, the statement does not hold for the ultrafiltration POU systems. An ultrafiltration POU system usually has very high removal efficiency of turbidity and more than 99.99% kill of bacteria.7 However, it does not reject many of natural organic and inorganic compounds in water, resulting in less possibility of fouling of the filter. Therefore, the capital and maintenance cost of ultrafiltration filter could be lower. In addition, the development of the materials and the fabrication process could further reduce its cost.
Ultrafiltration POU systems deliver high efficiency at low costs
Even the price of ultrafiltration POU systems can be reduced to 80 USD for a 4-member family living in low-income economies, it is still high. If some proper pre-treatment is applied, the price could be further reduced by extending the lifespan of the systems. Designing of those pre-treatment processes requires well-trained engineers.
Ultrafiltration POU systems cannot treat all contaminates therefore other processes also needed
In some cases, microbial contamination in water is not the only problem. Water source can be contaminated by harmful natural minerals, industrial wastewater, or landfill leachate. Simple units including pre-treatment enhanced ultrafiltration POU systems could not guarantee the water quality. Other treatment processes should be implemented. But the cost for treating water will significantly increase. In these cases, when the cost is too high, reaching for a new water source is necessary.
1 Progress on Drinking Water and Sanitation 2014 Update. World Health Organization and UNICEF.
2 Tapping the Market Opportunities for Domestic Investments in Water for the Poor. The World Bank and International Finance Corporation.
3 Arnal, J.M.A., Fernandez, M.S., Verdu, G.M., Garcia, J.L., 2001. Design of a membrane facility for water potabilization and its application to third world countries. Desalination, 137, 63-69.
4 Peter-Varbanets, M., Zurbrügg, C., Swartz, C., Pronk W., 2009. Decentralized systems for potable water and the potential of membrane technology, Water Research, 43, 245-265.
5 Control and Mitigation of Drinking Water Losses in Distribution Systems. US Environmental Protection Agency.
6 Secondary Drinking Water Regulations: Guidance for Nuisance Chemicals. US Environmental Protection Agency. https://water.epa.gov/drink/contaminants/secondarystandards.cfm
7 International Market Survey on Membrane-Based Products for Decentralized Water Supply (POU and SSS Units). TECHNEAU
8 The World Bank. https://data.worldbank.org/about/country-and-lending-groups#Low_income
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