Treatment of fish processing wastewater in a one- or two-step upflow anaerobic sludge blanket (UASB) reactor

The performance of one-step UASB reactors treating fish processing wastewater of different lipid levels was determined using artificially generated influent simulating that of the canning of sardines and tuna. The organic loading rates (OLR) and the hydraulic retention times (HRT) were 5–8 g COD.L⁻¹.d⁻¹ and 11–12 hours, respectively. In treating a wastewater that contains 3–4 g.L⁻¹ total COD of which 5–9% was lipids, the COD removal and conversion to methane were ca.78% and 61%, respectively. In treating a wastewater with a higher lipid content (ca. 47% of the total COD), the total COD removed and converted to methane were 92% and 47%, respectively. A considerable part of the influent total COD was removed via adsorption on reactor surfaces and sludge particles. The adsorption of lipids on sludge particles threatens the stability of the UASB operation. Thus, the performance of a first-step UASB reactor in removing suspended solids (SS) from a “high-lipid” wastewater was also determined in this study.