Please fill out our survey: https://docs.google.com/forms/d/e/1FAIpQLScrZYl99TBNyETIsLPXZkeTXHgstTeI_suICs6PZa8X8yK3OQ/viewform?usp=sf_link
Check out these organizations:
LeAF: https://www.leaf-wageningen.nl/en/leaf/For-whom/Public-sector-NGOs.htm
Centre for Science and Environment: https://www.cseindia.org/tag/sewage
UN Water: https://www.unwater.org/water-facts/quality-and-wastewater/