Anaerobic treatment of sludge from a MSW landfill leachate treatment plant

A study was carried out of anerobic treatment in the mesophilic range (37degreesC) of sludge from a leachate treatment plant (Biomembrat system) at the MSW landfill of Asturias. The reactor chosen was of the UASB type, with a useful capacity of 9 litres, operating at an HRT of 9 days. The COD values of said sludge ranged between 10 000 and 19 400 mgO(2)/l. Start-up of the reactor was realized in 7 stages, beginning with sludge diluted with distilled water and progressively increasing the amount of sludge fed into the reactor (from 10% up to 100%). The study was carried out for a period of 224 days. With the aim of favouring the growth of methanogenic flora, different amounts of methanol were added to the feed, ranging between 6.75 and 1 ml/l of feed in the first and last stages, respectively. In the two last stages, recirculation of the effluent was carried out (recirculation ratio: 2) with the two-fold aim of producing agitation in the reactor and of decreasing both the COD and the solids content of the reactor influent. The biodegration of the organic matter achieved with the anaerobic treatment of the sludge was high, obtaining decreases in COD of 87% by the end of the process. Purging of the digested sludge represented approximately 16% of the volume of the treated sludge.