Project Lead(s): Yu-Ling Cheng
Rainwater harvesting (RWH) has considerable potential to address the shortage of potable water that affects an estimated 1.1 billion people worldwide. RWH is prevalent in parts of Africa, Latin America and Asia, and is used by tens of millions of people.
In coastal Bangladesh, rainwater is collected and stored in large cisterns for use during the four to six months of the dry season. However, water is often contaminated during the collection and storage process, causing many health problems for millions of users.
The idea of this project was to develop a system to improve the microbial quality of household-level harvested rainwater by minimizing water contamination during collection and storage, and treating residual contamination, if necessary, just prior to use.
An extensive analysis of the contexts under which RWH systems were used in rural Bangladesh was undertaken, including analysis of prevalent drinking water sources and systems, and various community-level water filtration systems. Investigators examined RWH systems in five villages, ranging from household systems to those established for hospitals and schools, and interviewed users and developers of those systems.
Extensive analysis led the research team to conclude that minimizing water contamination during collection and storage, vis-à-vis a superior collection system, would be the most cost-effective and scalable solution.
The project team successfully designed both manually-operated and automatic rooftop-collection system concepts that, together with a crude filtration system (made with local fabrics, such as Sari), can considerably improve microbial quality of harvested rainwater. These approaches result in the collection of sufficient and much cleaner water, and are largely independent of roof type.
The approaches also prevent organic matter, insects and other impurities from entering the system during collection and storage. This is achieved by incorporating a pre-filtration system to remove residual solid particles and organic matter before collected rainwater enters the storage cistern, and by including a self-activated collection surface (a sliding roof device) to reduce reliance on operator diligence and maximize water collection when no one is home to attend/activate the system.
The manually-operated prototype system has been installed in Bangladesh for approximately three months (as of October 2016), with some initial testing and observations recorded.
Bangladeshi collaborators continue to collect and analyze water samples at rainfall events; monitoring total coliform, E. Coli and BOD (biological oxygen demand).