Small Wastewater Systems Many small and rural communities, including those in Indian Country and along the U.S.-Mexico border, struggle with aging or inadequate wastewater treatment systems, or do not have access to basic wastewater services. Small communities have 10,000 or fewer people and an average daily wastewater flow of less than 1 million gallons. Wastewater is water that has been used for various purposes around a community, including sewage, stormwater, and all other water used by residences, businesses, and industry. Wastewater requires treatment before it returns to lakes, rivers, and streams to protect the health of the waterbody and community.