OC San P1 and P2 Operating Range Values (ORVs) and plant performance during sampling period.

AS = activated sludge, TF = Trickling Filter, SC = Solids Contactor, MCRT = mean cell residence time, BOD-T = total biological oxygen demand. MCRT for all secondary treatment processes are calculated daily by OC San using the below equations. OCWD proposes to use the OC San-calculated values of MCRT for assessment of ORVs related to LRV credit value. BOD-T (P1 TF) is measured by OC San as a daily composite. Mean Cell Residence Time (MCRT) Calculations: P1 Activated Sludge Processes MCRT = (Volume of reactor x MLSS) ÷ [(WAS flow x WAS MLSS) + (Effluent Flow x Effluent TSS)]; where MLSS = mixed liquor suspended solids, WAS = waste activated sludge, and TSS = total suspended solids. P2 Trickling Filter Solids Contactor MCRT = [(Volume of reactor x MLVSS) + (Volume of reactor RSS VSS)] ÷ [(Waste Flow x RSS VSS) + (Effluent Flow x Effluent VSS)]; where MLVSS = mixed liquor volatile suspended solids, RSS VSS = raw sewage sludge volatile suspended solids, and VSS = volatile suspended solids. (XLSX)