Summary of Week 5 of Introduction to Household Water Treatment and Safe Storage (Coursera – École Polytechnique Fédérale de Lausanne)
It is important to understand whether household water treatment (HWT) products are achieving improvements in health (i.e. removing pathogens). Users do not only need access to effective options, but use them correctly and consistently. By testing the products, governments, implementers and funders can be informed of the performance.
Efficacy: The World Health Organisations (WHO) developed global performance standards based on their drinking-water risk-based approach. WHO has a tiered evaluation – highly protective, protective and limited protection – using log removal values of viruses, bacteria and protozoa. Chemical parameters are important but have yet to be developed. It is important to note that WHO measures efficacy (i.e. removal under controlled conditions), not effectiveness (i.e. removal in the real word).
Compliance: The consistent use of HWT is highly context-dependent and can be affected by personal and external factors. Conceptual frameworks to analyse compliance include the RANAS psychological model and IBM-WASH. Compliance is hard to measure.
Health impact: How much can diarrhea be prevented by improving water quality alone? There are significant health gains but it is complicated and expensive to measure. Routine monitoring and evaluation should focus on use before attempting to measure health impact.
Cost-effectiveness: Cost-effectiveness could consider cost benefit (money for money), cost effectiveness (money for DALYs) and willingness to pay (money for HWTS). Cost benefit adds up the costs of the intervention (e.g. meeting the Water MDG target) and weights it against the benefits resulting from the intervention (e.g. reduced diarrheal disease). Cost effectiveness looks only at the cost and considers which approach is the cheapest to achieve a desired outcome. One study found that chlorine and SODIS had the lowest cost.
Often decisions on the use of HWTS technologies are made on the program or government level. Selecting options comprises establishing the context (e.g. water to be treated), defining objectives and assessing the options against objectives. The criteria used is important, and multi-criteria decision analysis can be applied to the selection process.
Summary of Week 4 of Introduction to Household Water Treatment and Safe Storage (Coursera – École Polytechnique Fédérale de Lausanne)
Business models describe how organisations create and capture value. This can be in the form of a nonprofit, social business or for-profit. Business model innovations in water treatment include diversification, water payment methods, cost recovery, and extending distribution channels.
If the goal of household water treatment and storage (HWTS) is to maximise social good, then HWTS should target the most vulnerable populations, such as schools and integrated with health approaches. Healthcare systems are already in contact with the most vulnerable people, and HWTS can increase the efficacy of other health interventions, such as antenatal care and HIV/AIDs.
One role that governments could play is to respect, protect and fulfill the right to water. In the context of HWTS, governments could facilitate access to information on HWTS and the efforts to stakeholders to promote and provide HWTS. Governments could formalise this through national action plans.
Summary of Week 2 of Introduction to Household Water Treatment and Safe Storage (Coursera – École Polytechnique Fédérale de Lausanne)
In water treatment (and in life), the question is what level of risk is acceptable. WHO defines safe drinking water as water that presents no significant risk to health over a lifetime of consumption.
The water safety framework comprises health-based targets, water safety plans and verification. Health-based targets include performance measures in terms of log reduction values.
It is important to note that measuring water quality is not the same as water safety because water quality varies in space and time, and no E.coli does not mean no contamination. Multiple treatment barriers should be put in place to remove contaminants.
Health-based targets include performance measures in terms of log reduction values. Water quality measurement does not mean water safety because water quality is variable in space and time, and no E.coli does not mean no contamination
Water treatment options: Sedimentation and filtration
A household-level treatment process typically comprises sedimentation, filtration, disinfection and safe storage.
- Sedimentation removes turbidity (suspended particles in water), and some pathogens. Turbidity itself has no health risks, but has impacts on subsequent treatment steps. Mechanisms include gravity settling, and coagulation and flocculation.
- Membrane filtration works on size exclusion, electrostatic effects and biological activity.
- Ceramic filters work on physical and electrostatic removal. It is common to brush silver onto filters, which contributes to bacteria reduction and prevents biofilm growth and clogging.
- Biosand filtration also uses size exclusion, electrostatic effects and biological activity.
Summary of Week 1 of Introduction to Household Water Treatment and Safe Storage (Coursera – École Polytechnique Fédérale de Lausanne)
There are many diseases caused by poor water, sanitation and hygiene. In particular, diarrhea is a leading cause of mortality and morbidity.
Diseases related to poor water, sanitation and hygiene can be classified according to its transmission pathways: waterborne, water-washed, water-based and water-related. This is the Bradley classification, and informs the selection of appropriate control mechanisms.
These diseases are caused by pathogens that can be described by its biological type: protozoa, bacteria, viruses and helminths. These are transmitted through pathways illustrated by the F-diagram.
Because it is impractical to measure all pathogens, faecal indicators area used. Escherichia coli (E.coli) is generally considered the most suitable, although it does not necessarily co-relate to contamination risk. A more complete picture can be obtained by also doing a sanitary inspection. Contamination can occur at the point of the water resource, delivery, collection and transport, household storage, and consumption.
Household water treatment offers the opportunity to remove contamination that occurs before consumption. Treatment processes include sedimentation (pre-treatment), filtration, boiling, UV radiation (solar disinfection) and chlorine. Each process has different levels of effectiveness and different applications.