Treatment of Meat-processing Wastewater With a Low-cost Sand/gravel Bioreactor System

A full-scale sand/gravel bioreactor system was constructed to treat wastewater at a small turkey processing plant. The system was designed to treat 757,000 L day-1 at an application rate of 6 cm day-1. Twelve 25 x 55 m sand bioreactors cover 1.6 ha. Construction cost was $1,426,000 and the plant costs $57,600 per year to operate. Normalized to volume of wastewater treatment, the capital and operation cost is $1.03 m-3. The plant began discharging effluent in 2013. Throughout its operation, the plant has met all effluent requirements for CBOD5, TSS and fat, oil and grease (FOG). FOG was always below the detection level of 5 mg L-1 in the treated effluent. Ammonia is removed by the sand/gravel bioreactors through the summer months. During the winter/spring months supplemental ammonia removal with an ion-exchange system is used to meet effluent standards. The low cost of a sand bioreactor makes it suitable for small meat processors.