Low-cost treatment of meat processing wastewater with a sand/gravel bioreactor system

Abstract. A wastewater treatment system was designed and constructed at a turkey processing plant to treat up to 757,000 L day^-1 (200,000 gal day^-1) based on research conducted at the Ohio State University on aerobic sand/gravel bioreactors. In total, 1.6 hectares (4 acres) of land were used to site twelve 25 x 55 m (82 x 180 ft) sand bioreactors. The objectives were to learn the resource needs to construct a system, quantify the construction and operating costs, and measure the system performance. The system construction cost was $1,426,000 and $57,600 per year to operate. On a cost per m³ basis, the capital and operation cost is $1.30 m^-3 ($0.00390 gal^-1). Effluent fats, oils and grease are not detectable. CBOD₅ and total suspended solids are always below the NPDES discharge limits of 10 mg/l CBOD₅ and 12 mg/l total suspended solids. Ammonia-N is sometimes discharged from the bioreactors in excess of the NPDES standards of 1 mg/ in summer and 3 mg/l in winter. An ion-exchange system is used to remove the residual ammonia from the effluent.