Startup and Operation of North America's Largest Biological Aerated Filter Ammonia Removal System

Onondaga Lake, located in Central New York State within the City of Syracuse limits, had the dubious distinction as being one of the most polluted lakes in the U.S. In 1998, Onondaga County signed an Amended Consent Judgement (ACJ) with the State requiring $380 million worth of projects to increase the level of treatment at the Metropolitan Syracuse Wastewater Treatment Plant (Metro Plant), as well as to address CSOs. The most significant of the ACJ projects was the addition of ammonia and phosphorus removal facilities at the Metro Plant. With a total construction cost of approximately $130 million, these facilities were focused on achieving some of the strictest nutrient discharge limits in the country. Based on water quality modeling, ammonia limits were established and included in the ACJ. The innovative biological aerated filters (BAF) technology was recommended for Stage II and III ammonia removal. Pilot studies at the Metro Plant confirmed the technology as capable of achieving the limits. The systems piloted included the Kruger Biostyr and the Infilco Degremont Biofor. The result of an evaluated bid process, which took into consideration both capital and operating costs, was the procurement of the Biostyr BAF. The 18-cell BAF facility is the largest of its kind constructed in North America, with cells sized at 57 feet by 28 feet by 26 feet deep (including 12 feet of media). Average design flow is 84 mgd, with a 150 mgd peak capacity. Design influent ammonia concentration was 17 mg/l and design ammonia loadings were set at 40 pounds per 1000 cubic foot per day average and 48 pounds per 1000 cubic foot per day maximum month. Construction began in the Summer of 2001 and was completed by the November 1, 2003 consent order date. A detailed startup plan provided system descriptions, equipment lists, startup prerequisites, inspection and certification requirements, startup checklists, process and instrumentation diagrams (P&IDs) as well as specific contract requirements for startup. Due to the construction schedule and the consent order deadline, startup had to begin during the coldest time of the year in Central New York. Remarkably, the system came up to performance level as indicated in Figure 1, in a very short time. The system achieved Stage III compliance within 60 days of startup, an impressive feat, considering water temperature was at approximately 10 degrees C for the entire period. The stringent effluent limits of a monthly average concentration are consistently met and the system has operated without any major issues. The three-year data set indicates only three days out of about 1000 days of operation, where the monthly average limit was exceeded by daily data. The system has been able to accommodate flow swings from less than 50 mgd to approximately 150 mgd, in a matter of hours, during severe wet weather conditions. The results of the three year operation indicate that the system is achieving Stage III levels years in advance of the consent order schedule. Those who have studied Onondaga Lake attest that the Lake is already showing a marked improvement.