Upgrading the Wastewater Treatment System of a Slaughterhouse and Meat Packing Facility

This work discusses the case study of a slaughterhouse and meatpacking facility in need of upgrading its wastewater treatment system. The existing wastewater treatment system consisted of the following major components: (i) raw wastewater lift station No.1; (ii) screens (three units); (iii) anaerobic reactors (seven concrete tanks) connected in series; (iv) lift station No.2; (v) aerated polishing pond; (vi) chlorination system; (vii) effluent storage pond and (viii) sprayfield. In absence of sanitary sewer in the vicinity of the facility, the treated effluent is land applied through an on-site slow-rate land application system (sprayfield) permitted for 40,000 gallons per day. The water quality criteria at the effluent require meeting limits of 5-day carbonaceous biochemical oxygen demand (cBOD5 ), total nitrogen (TN) and total phosphorus (TP) of less than 100 mg/L, 64 mg/L and 13 mg/L, respectively. Additional limits are to be met in the groundwater monitoring wells at the sprayfield. This paper discusses the shortcomings of the existing system in reference to the regulatory limits and outlines the alternatives considered to mitigate the problem. Based on the historical data made available by the owner and results from recent testing the following influent loadings were considered in the conceptual design of the new system: BOD5 3,070 mg/L, total suspended solids (TSS) 4,060 mg/L, total dissolved solids (TDS) 2,144 mg/L, TN 384 mg/L and TP 35 mg/L. The new system was designed to treat 120,000 gallons per day of average flow. Meeting future capacity needs, complying with water quality limits, utilizing existing treatment components, minimizing cost, and ease in operation were all criteria considered in the design of the new system. Treatability tests of the wastewater proved critical in supporting the need for a dissolved air floatation (DAF) unit as part of the treatment to effectively minimize the impacts of fats, oil and grease (FOG) and suspended solids on downstream processes.