Fairfield Suisun Sewer District

Water that flows from kitchens and bathrooms inside local homes and businesses can contain harmful organisms and substances that present potential health and environmental hazards. Our job is to collect that wastewater, draw it safely away from your property and transport it for processing that eliminates these potential hazards. The District owns and operates the wastewater treatment plant that s

erves Fairfield, Suisun City and Travis Air Force Base. Water that drains from kitchens and bathrooms inside local homes and businesses flows to the wastewater treatment plant, where it is cleansed through various biological and chemical steps. The wastewater collection system is designed somewhat like a tree. The smallest-diameter branch sewers in city streets are connected to individual homes and small businesses. Several branch lines connect to main sewers that serve entire neighborhoods or business districts. They, in turn, feed into larger diameter trunk lines that lead into our treatment facility. Wastewater undergoes a multi-step treatment process at our central facility. First, the wastewater passes through a screening process that traps large solid objects that may have accidentally entered the system. Grit chambers then remove sand and sediment from the flow, and primary sedimentation tanks allow heavier food-related wastes to settle from the water. Next, an intermediate treatment step uses bacteria growing on large honeycomb-like plastic blocks in towers to remove a significant proportion of remaining organic matter. The next step, called “activated sludge treatment,” takes place in concrete tanks bubbling with air, where more microorganisms consume any remaining organic matter. Following aeration, the water is transferred to a secondary sedimentation pond for removal of the microorganisms. Any particles remaining are extracted as the water runs through a network of tertiary sand filters. Lastly, the water is disinfected with UV light to kill pathogenic organisms. Solids removed during the various processes are thickened and treated through a process called “digestion” in a closed vessel. Methane gas produced as a natural byproduct of the digestion process is used to fuel electrical generators that the District owns, thereby reducing reliance on PG&E for electrical energy. A “dewatering” process further dries the solids, preparatory to proper disposal. The fully treated water leaving the treatment plant is nearly as clean as drinking water. The plant’s complex pollutant-removing treatment processes protect the health and environment of local citizens and the Suisun Marsh.