Plant Scale Phosphorus Removal by Primary Addition of Sodium Aluminate

The Great Lakes are the receiving waters for municipal wastewaters and treatment plant effluents in this area. The lakes are now experiencing excessive eutrophication resulting in the accelerated aging of these bodies Of water. The Lake Michigan Enforcement Conference required 85 percent phosphorus removal from all major effluents discharging into the Lake Michigan watershed by December, 1972. The Grafton, Wisconsin Wastewater Treatment Plant was one of the first plants in the watershed to design and operate phosphorus removal facilities. The Grafton, Wisconsin Wastewater Treatment Plant is designed to treat an average flow of 1.0 mgd and a maximum flow of 2.55 mgd. Influent flow is divided between a conventional activated sludge unit (East Plant) and a contact stabilization unit (South Plant). Effluent from both plants discharges into the Milwaukee River which is tributary to lake Michigan. A sampling program was carried out during 1971-1972 to evaluate the effectiveness of primary addition of sodium aluminate for phosphorus removal on a plant scale basis. The sampling program at the Grafton, Wisconsin Wastewater Treatment Plant entailed the 24-hour composite sampling of the raw wastewater, the East Plant\u27s primary and final effluents and the South Plant\u27s primary and final effluents. Composite samples at these locations were collected during a period when sodium aluminate was added to the influents of both primary clarifiers. In addition, composite samples were collected from these locations during a period when sodium aluminate was not being added for phosphorus removal. The samples collected were analyzed for various forms of phosphorus, Biochemical Oxygen Demand (8005), Chemical Oxygen Demand (COD), arrmonia nitrogen, organic nitrogen, total volatile and fixed residue, volatile and fixed suspended solids, pH, and fecal coliforms. Addition of sodium aluminate prior to the primary clarifiers resulted in improved primary removals of BOD5, COD, suspended solids, fecal coliforms, organic nitrogen and phosphorus in comparison to primary treatment operation without aluminate addition. Overall plant treatment efficiency during sodium aluminate addition was only significantly improved with respect to phosphorus removals in comparison to overall plant operation without aluminate addition