Anaerobic biological treatment of frozen seafood wastewater

The effect of salinity was studied on the anaerobic treatment of raw, frozen seafood wastewater. A single-stage of four organic loading rates (OLRs) ranging from 0.58 to 1.45 kg COD/m(3).day and two stages of five OLRs in acidogenic reactors ranging from 0.29 to 2.31 kg chemical oxygen demand (COD)/m(3).day were fed into laboratory-scale bioreactors. The wastewater contained a COD of 1,735 mg/L with high salinity, sodium ion (Na+) and nitrogen (N) contents of 8.63 parts per thousand 5,071, and 165 mg/L, respectively. In the single-stage operation, the COD and total volatile solids (TVS) removal reached maxima of 55 and 63%, respectively, at 0.58 kg COD/m(3).day. In the two-stage operation, the COD and TVS removal were 65 and 70% at the most appropriate OLR of 1.16 kg COD/m(3).day. At this OLR, the highest CH(4)content and CH(4)yield obtained were not satisfactory at 26.62% and 71 L (reported at standard temperature and pressure)/kg COD removed, respectively. For both types of operation, the biogas did not contain sufficient methane (CH4) in all tests at all OLRs. The salts, Na+, and N at the levels in this study did not upset the organic removal efficiency but did adversely affect CH(4)production. Two-stage anaerobic operation could not prevent toxicity due to the characteristics of this wastewater.