Treatment of high strength acidic wastewater with a completely mixed anaerobic filter

Abstract A completely mixed anaerobic filter, in which the influent organic matter concentration is diluted with recirculated effluent, was found to effectively remove organic matter concentrations in high strength acidic wastewater, at a range of organic loadings and shockloads. The methane in the generated gas accounted for 93% of the COD removal in the unit, while a solids balance indicated that only 0.012 g VSS was produced per g COD removed. Due to the low solids production and the initial seeding of the unit with digested sludge no nutrient additions were required during the 518 day period even though the COD:P and COD:N ratios were as high as 4360:1 and 39:1, respectively. Although a possible heavy metal toxicity was observed in the unit, this was eliminated after sulfide addition.