In Mexico, only 30% of domestic wastewater is appropriately treated, mainly due to high costs associated with building and mantaining sewerage. This leads to untreated wastewater being directly discharged, or conducted to abandoned centralized treatment plants.

César (27) and his team have created an ‘ecosystem in a tank’ which treats wastewater onsite through a process known as vermifiltration. The solids are instantly separated from the water when entering the tank and processed by earthworms into vermicast, which in turn serve as filter media for primary wastewater treatment. As earthworms wiggle, they promote air circulation in the system, avoiding bad smell production. Moreover, this filter is compact, easy to install and mantain, and cost-competitive compared to traditional anaerobic septic tanks.