Across the world, about 80 percent of wastewater is dumped back into the ecosystem without being treated. Untreated wastewater leads to a range of problems and contributes to faecal contamination of drinking water sources for about 1.8 billion people. Treating wastewater requires treatment plants that can be expensive. Now, a Bengaluru-based startup ECOSTP Technologies has developed a new and efficient design for sewage treatment plants that takes inspiration from the digestive system of cows. It is so efficient that it does not even need the power to run. Cows have a powerful digestive system made up of four chambers containing bacteria that do not need oxygen. As grass passes through these chambers, the bacteria break it down into smaller parts eventually converting it to gas, nutrients, water, and waste. [Bengaluru-resident Tharun] Kumar and his team developed a treatment plant to mimic this structure and used the bacteria from cow dung to break down the waste in wastewater. Their plants do not even require power. Instead, they use gravity to move wastewater across chambers. In the treatment plant, the further wastewater travels, the cleaner it gets. Eventually, the solid waste settles down, and the wastewater is converted into gas and clear water, which can be safely reused. "Since inception, we have saved 280 million litres of water and have saved 315 MW of power which is equivalent to powering 35 villages for a year," Kumar, co-founder, and CEO of ECOSTP Technologies [said].