SEMI-CONTINUOUS APPLICATION OF LEACHATE AND SEPTIC TANK EFFLUENT TO INCREASE AND ACCELERATE BIOGAS PRODUCTION IN LANDFILLS

Abstract

This project focused on evaluating the production of biogas from urban solid waste with semi-continuous application of leachate and domestic sewage septic tank effluent. The work lasted 12 months and was carried out at ASMOC with 16 reactors of 1,000 liters each. The base of each reactor was filled with layers of gravel, followed by 0.5m of MSW, prepared according to ASMOC's gravimetry, and a layer of topsoil. The material was compacted manually using a socket in which 10% of the volume was used as a headspace at the top of the reactors. Of these, 4 were irrigated with leachate from the old landfill cell, 4 with concentrated leachate; 4 with cesspit effluent and the other 4 received neither leachate nor cesspit effluent. 20L of leachate and effluent were fed into the corresponding reactors every 15 days. Half of each system was irrigated every two weeks with 30L of water to simulate rainfall. The composition and flow rate of the biogas produced was measured for each reactor, one point at a time, on a daily basis. It was found that rainfall interferes with methane production in landfills. The best performance in methane production was achieved with the introduction of leachate in both the dry and rainy periods. The irrigation of septic tank effluent in the dry season increases methane production in landfills. Finally, under the conditions tested, the recirculation of raw leachate is the best alternative for increasing methane production in landfills, both in the dry and rainy seasons.