SODIS: An effective water treatment system
There are still about 20 million Bangladeshis who lack access to safe drinking water
Abu Hena Mostofa Kamal
Clean water is a cornerstone of sustainable development. The Sustainable Development Goals address this issue in their goal number 6, which aims to: Ensure availability and sustainable management of water and sanitation for all. Target 6.1 specifies: by 2030, achieve universal and equitable access to safe and affordable drinking water for all and substantially increasing recycling and safe reuse globally.
SODIS (Solar disinfection) is a simple household water treatment system, which has the potential to make a powerful contribution to the achievement of goal number 6 of the SDGs in Bangladesh. SODIS has a proven track record in reducing viruses, bacteria, and protozoa in water and of diarrheal disease incidence. The technique is affordable, environmentally sustainable, and socially acceptable. SODIS is one of the household water treatment system (HWTS) officially recommended by the World Health Organisation (WHO). To date 33 countries in Africa, Latin America and Asia have been using the SODIS technique for water disinfection/purification.
Even though Bangladesh has made considerable progress in tackling the water crisis, and in improving health and sanitation, there are still about 20 million people who lack access to safe drinking water. The problem is particularly salient in arsenic hot spots and salinity prone coastal areas, where an estimated 43,000 Bangladeshis every year die of waterborne diseases, mostly in poor rural areas. However, water shortages are a problem shared by both rural and urban areas. In Bangladesh, fetching water is especially strenuous for women, since they are in charge of water for household use. Rural women find themselves under tremendous pressure and water scarcity is often a cause of domestic violence. Even in coastal areas where water is evidently more available, women must often make several trips every day to fetch water from distant sources. Increased salinity has further exacerbated the vulnerability of already marginalized and disaster-prone coastal communities. In the remote villages of Bagerhat in the southern part of Bangladesh, water scarcity has even had serious impacts on marriage. Parents are not interested in matches that would rehouse their children to villages where water is scarce. Parents also do not want their daughters to marry men from such communities in order to prevent them from the stress of walking wide distances to fetch water. Moreover, the skins of young women are reported to have roughened because of the increased salinity of water from nearby sources.
Science of SODIS - how it works: Solar energy provides two mechanisms of treatment for SODIS i) thermal (pasteurization), ii) UV radiation. Either thermal or radiation can work independently, but studies indicate synergistic effects when the two are applied together. This means that the mortality of the microorganisms increases when they are exposed to both temperature and UV-A light at the same time. SODIS was developed in the 1980s as an inexpensive method for disinfecting water used for oral rehydration solutions. In 1991, the Swiss Federal Institute for Environmental Science and Technology began to investigate and implement SODIS as a household water treatment option to prevent diarrhea in developing countries. The combined effects of UV-induced DNA alteration, thermal inactivation, and photo-oxidative destruction inactivate disease-causing organisms. Pathogenic microorganisms are vulnerable to two effects of the sunlight: radiation in the spectrum of UV-A light (wavelength 320-400nm) and heat (increased water temperature). SODIS is ideal to disinfect small quantities of water.
The efficiency of the SODIS process is dependent on the amount of sunlight available. Solar radiation however is unevenly distributed and varies in intensity from one geographical location to another depending on latitude, season and the time of the day. The most favourable regions for SODIS are the semi-arid regions located between latitude 15N and 35N (as well as 15S and 35S). Bangladesh is located between latitude 2034˝N and 2638˝N and solar radiation ranges from 4 to 5 KWh/m2 (total radiation per day). Bangladesh is therefore in a good position to rely on solar energy for the disinfection of drinking water.
SODIS uses solar energy to destroy pathogenic microorganisms causing water borne diseases and thereby it improves the quality of drinking water. UV treatment is effective against bacteria such as E.coli, Vibrio cholerae, Salmonella paratyphi, as well as viruses such as bacteriophages and rotaviruses.
SODIS improves the microbiological quality of drinking water, and it therefore improves the family health.
SODIS can serve as an entry point for health and hygiene education.
SODIS provides individual users with a simple method that can be applied at household level under their own control and responsibility.
SODIS is easy to understand and does not require literacy. It is therefore suitable for contexts with very low levels of education.
In particular, SODIS entails great benefits for women who save the time, which they now use for fetching and boiling water from distant sources, as well as the time and toil invested in collecting fuel. Relieving women from this burden allows them to engage in other, productive activities that improve the family wellbeing. This in turn can strengthen their position in the family and their self-esteem.
Safe drinking water also positively impacts on the health of children and increases their capacities for studying efficiently. This in turn should have a positive impact on the drop-out rate from the schools.
SODIS relies on a renewable, natural source of energy and it reduces the need for traditional, environmentally damaging energy sources such as firewood and kerosene/gas. Consequently, the use of SODIS reduces deforestation, which is a major environmental problem in most developing countries including Bangladesh.
SODIS also decreases air pollution caused by the burning of conventional energy sources. Public water supply systems in developing countries often fail to provide water safe for consumption. One of the reasons is the governments lack of financial resources. SODIS mitigates this problem by making people less dependent on the governments supply.
SODIS does not require a large and costly infrastructure and is therefore easily replicable in self-help projects.
Financial advantages: Household expenditures can be reduced when the users family health is improved because less financial resources are required for medical care. In addition, expenses for traditional energy sources such as gas, kerosene and firewood decrease. Only limited resources are required for the procurement of transparent plastic bottles. Therefore even the poorest members of communities can afford SODIS.
SODIS is a simple and low-cost method for addressing a severe issue that currently hinders sustainable development in many parts of Bangladesh. By providing easy access to potable water and ensuring year round safe water access for the communities, it has the potential to considerably improve the circumstances of people living in arsenic hot spots and salinity prone coastal areas of Bangladesh. However, in order to enact its potential, awareness of SODIS needs to be raised among the people in charge. Leverage can be maximized if policy-makers on national and local levels, i.e. the Department of Public Health and Engineering (DPHE), and the Union Parishad (LGIs), and competent NGOs work together to actively promote SODIS among their constituencies and beneficiaries. By doing so, they will assist Bangladesh in achieving SDG 6 and have an impact on the well-being of millions of people.
The writer is a development professional e-mail [email protected]
