Definition of operating guidelines for nitrification from historical operations records

The Sanford, Florida Water Reclamation Facility has experienced recurring problems over the past several years with incomplete nitrification. The objective of this investigation is to determine useful guidelines for plant operation to address nitrification requirements. The effluent problems were believed to result from a combination of operational and equipment hardware problems, including excessive sludge wastage and oxygen supply limitations. This study evaluates historical operating records to identify empirical trends which relate nitrification efficiency and specific operating parameters. To determine the cause of partial loss of nitrification, periods of change in the ammonia concentration were identified for detailed examination. For these episodic periods, chronological plots were prepared for each independent variable (solids residence time, dissolved oxygen concentration temperature, pH, and hydraulic residence time) and the dependent variable (ammonia concentration). The results of this analysis showed the solids residence time (SRT) and the dissolved oxygen (DO) concentration to be the primary factors affecting the ammonia concentration. The episodes where DO was the limiting factor proved to be mainly due to equipment problems, while the SRT problems resulted from operational practices. The temperature and the hydraulic residence time (HRT) also impacted the ammonia concentration. Proper control over the amount of sludge wasted would greatly improve the nitrification efficiency of the plant. The plant could maintain a high nitrification efficiency if certain operational standards are followed. The DO concentration should not be allowed to drop below 2mg/L. More importantly, the SRT must be maintained above five days from April through September and above eight days from October through March