USE OF UASB TECHNOLOGY TO TREAT CRAB PROCESSING WASTEWATERS

Crab cooker wastewater contains high concentrations of chemical oxygen demand (GOD), total suspended solids (TSS), and total Kjeldahl nitrog en (TKN). Biological treatment of the wastewater releases high concent rations of ammonia. In this paper the treatment of crab cooker wastewa ter by means of upflow anaerobic sludge blanket (UASB) technology was evaluated. When treating unamended crab cooker wastewater, UASB perfor mance appeared similar to upflow anaerobic bed filter (UBF) and upflow anaerobic packed filter (UPF) reactor performances. When treating una mended wastewater at an organic loading rate (OLR) of 3.0 g COD/L/d (0 .25 d(-1) FIM ratio), a UASB reactor's effluent soluble COD fluctuated and increased to above 6,000 mg/L. Batch toxicity assays indicated th at unionized ammonia limited anaerobic treatment performance. Unionize d ammonia concentrations of 41 and 120 mg/L (as nitrogen) caused 50 an d 80% inhibition, respectively, of acetate-utilizing methanogens. Acid ification of the feed wastewater greatly enhanced UASB treatment perfo rmance by reducing reactor pH and wastewater feed suspended solids con centrations. When fed acidified wastewater at an OLR of 6.4 g COD/L/d (F/M = 0.3 d(-1)), a UASB reactor's effluent soluble COD was 1,220 mg/ L. The wastewater feed TSS was reduced from 910 mg/L, prior to acidifi cation, to 249 mg/L in the reactor's effluent.