Anaerobic Co-Digestion of a Single Source Oily Waste and High Strength Pet Food Wastewater: A Study of Failure and Revival of a Full Scale Digester

This paper focuses on the revival of a formerly failed digester of 1800 m3 volume. The most obvious cause of failure was identified to be due to capping caused by foam and scum, as result of attempting to treat oil rich, high strength wastewater. The revival was affected by implementing co-digestion in a 3-step remedial procedure. Though in the typical sense, codigestion involves separate waste streams, here a single waste stream was manipulated to apply the concept of co-digestion. Through the virtual co-digestion the digester presently succeeds to treat the daily plant effluent flows of 50 m3 with COD > 45 g/L and around 10 tons of sludge/day which has around 20% oil and fat, exhibiting a COD removal > 90%.The digester operates at 35±1 °C and HRT of 30 days with loading rates of 3.4 kg COD/m3d and 1.3 kg O&G/m3d. The biogas generated from this digester is sufficient to operate a 40 hp boiler at 100 psi.