The complexity of biological activities and the number of process variables important to nutrient removal in advanced activated sludge wastewater treatment plants (WWTPs) require the use of process simulation. Process simulation can help engineers evaluating different treatment processes and designing the best biological nutrient removal (BNR) process. It can help operators optimize their plant performance and, at the same time, reduce their operating cost associated with aeration and methanol addition.
The Graton Water Resource Recovery Facility (WRRF) in Sonoma County, Calif., is owned and operated by Graton Community Service District (GCSD). GCSD was mandated in 2004 to upgrade its 1979 secondary aerated lagoon to tertiary discharge standards. Before considering the most economical upgrade option for GCSD, Lescure Engineers (Santa Rosa, Calif.) evaluated the biological treatment capacity of the existing lagoon system. It determined that the lagoons have sufficient capacity to deliver effluent meeting the numerical BOD limit for tertiary effluent.
This case study analyzed phosphorus (P) removal from municipal wastewater during the past four summer permit seasons at the Greene County Sugarcreek Water Resource Reclamation Facility. The facility has utilized both chemical removal and enhanced biological phosphorus removal (EBPR) to provide supplemental P removal in excess of metabolic P removal in order to comply with concentration-based effluent P limits. Both methods were demonstrated to achieve an effluent total phosphorus (TP) concentration of less than 0.5 mg/L. Alum was utilized for chemical phosphorus removal.