As a part of the two-day Indo-German conference on Sustainability at IIT Madras, researchers here have designed a zero-discharge toilet that neither requires conventional electricity supply nor yields any fluid output. The research project, funded by the Department of Science and Technology (DST), treats black water (waste water and sewage from toilets) using solar energy to make it reusable.
The 4-5% solid waste (faeces) in the black water is segregated and treated in a special arrangement so that the dried sludge can be used either as a biofuel or fertiliser for gardening. “We have developed a pilot system which works on synthetic faeces and urine prepared as per composition from earlier research projects,” said professor Ligy Philip, who is part of the research team. The system has a mechanical separator, distillation unit and dryer — all of which uses solar energy to operate. “The liquid waste (urine) is distilled using an electrical distillation unit to recover water and minerals,” she added.
D Kirthika, a research scholar involved in the project, said that when this distilled output was monitored for various parameters, around 60-70% was clear water in a condensed state, which can be used for washing purposes. “The rest, 30-20% yellowish in colour (due to presence of high organic content) can be used for flushing and the 10% reject, high in organic matter and nutrient content, can be dried and used as fertiliser,” explained Kirthika.
Meanwhile, solid matter (faeces) was dried using an electric dryer to remove bacteria and moisture content. Researchers claimed that moisture removal rate of dried matter was found to be 87% and dried faeces was found to be rich in nutrient content and free from bacteria and parasites. “Therefore, dried faecal matter can be used as soil conditioner and also as biofuel,” Kirthika told City Express. This system, apart from generating a reliable source of water, also reduces pollution, improves sanitation and provides access to good fertiliser and soil conditioners. Several projects developed at IIT and other technical institutes including a sustainable septage management and electric grids were displayed at the two-day conference.