U.S. SJWP Winner Applies Sanitation Research to Composting Toilets in India

Nishita Sinha from Chatham, N.J., won the 2016 U.S. Stockholm Junior Water Prize for her research on improving performance of two-pit composting toilets installed in India. Photo courtesy of Allison O’Brien, AOB Photo.

Nishita Sinha from Chatham, N.J., won the 2016 U.S. Stockholm Junior Water Prize for her research on improving performance of two-pit composting toilets installed in India. Photo courtesy of Allison O’Brien, AOB Photo.

Nishita Sinha from Chatham, N.J., has a personal connection to her research. The winner of the 2016 U.S. Stockholm Junior Water Prize began 2 years ago trying to improve sanitation in Payagpur, North India.

After witnessing and learning the dangers of open defecation in the village where her grandmother resides, Sinha started working to garner support from organizations to install 61 two-pit composting toilets in Payagpur. She wanted each family to have one of these systems, develop a sense of responsibility and ownership for their toilets, and facilitate any maintenance the system would need, according to Sinha’s research report.

The system consists of a toilet seat, primary pit, and secondary pit. Inside each pit sits a honeycomb brick structure surrounded by sand that acts as a slow sand-filtration system. Waste enters the primary pit, and solids settle at the bottom. After about 3 to 5 years of use by a single family, the primary pit fills and is closed off. Effluent then is directed into the secondary pit. Solid waste in the primary pit anaerobically decomposes into safe, odorless fertilizer between 1 and 2 years. The fertilizer then can be harvested and land-applied, the report says.

As Sinha became more familiar with the system’s design and observed its installation, she became increasingly concerned about how it handled liquid waste. As solid waste fills up each pit, liquid waste, which can contain bacteria and dissolved solids, flows through the honeycomb-brick structure and into the surrounding soil. Initial analysis suggested that the sand filtration alone was insufficient for removing fecal coliform contaminants, the report says. So, she began researching ways to improve the system.

Sinha created tabletop plug-flow reactors to test the ability of other filtration methods to remove fecal coliform bacteria. She compared bacterial concentration in simulated human waste before and after treatment to find that incorporating sand-pebble filtration can help improve the effectiveness of these toilets by as much as 83% during moderate use. Using a combination of the filters allowed more volume of wastewater to be treated before contaminants escaped the system. And because liquids from the toilets travel horizontally through the filter instead of vertically, this could mean a longer retention time and more thorough filtration, the report says.

From left, Joshua Zhou, North Carolina state winner, and Nishita Sinha, New Jersey state and U.S. SJWP winner, enjoy a group activity making rainsticks to donate to a local North Carolina elementary school during the U.S. SJWP competition. Photo courtesy of Allison O’Brien, AOB Photo.

From left, Joshua Zhou, North Carolina state winner, and Nishita Sinha, New Jersey state and U.S. SJWP winner, enjoy a group activity making rainsticks to donate to a local North Carolina elementary school during the U.S. SJWP competition. Photo courtesy of Allison O’Brien, AOB Photo.

“Nishita’s study to develop safe sanitation solutions showed not only an understanding of the technical issues associated with designing sanitary facilities to decompose the organic component of waste, but also recognized the need to reduce the bacterial concentration associated with the waste,” said Jeanette Brown, chair of the SJWP review committee.

Sinha already has worked with organizations installing the toilets and obtained permission to add her researched materials to future installations to measure their efficacy in real-life. “Soil samples will be collected and analyzed for fecal coliform contamination right after installation and then three months, six months, and one year after installation,” the report says.

As winner of the 2016 U.S. SJWP competition, Sinha received $10,000 and an all-expenses-paid trip to Stockholm where she will represent the U.S. in the international competition, held during World Water Week, Aug. 28 through Sept. 2.

— Jennifer Fulcher, WEF Highlights

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