Improvement in the Biodgradability of Dry Anaerobic Reactor Sludge Using Various Pre-treatment Methods

Archis Ambulkar, Grad.

Lycoming County Resources Management Services, Ine. (LCRMS) in Lycoming County is involved in landfilling of municipal solid waste (MSW) as a part of waste management practices. LCRMS presently has about 8 years of capacity remaining for landfilling of MSW. Also, it is difficult to site new landfills. Hence, LCRMS undertook a project with Bucknell University to explore the possibility of anaerobic degradation of MSW using a Dry Anaerobic Reactor (DAR) at landfill. A DAR with capacity of 280 liters was run at 30 % total solids (TS) concentration with 15 days of solids retention time (SRT) at the landfill. The basic purpose of research undertaken as a part of thesis was to study the effect of various pretreatments on improving the biodegradability of MSW in DAR. Improvement in biodegradation would lead to destruction of more MSW, generation of less waste for landfilling and production of more methane which is a source of energy. Various treatments such as trace metals (TM) supplementation to, caustic & microwave, and heat & caustic treatments of DAR sludge and ultrasonic treatment of feed MSW were performed to study the improvement in unit methane production. Studies related to trace metals (Fe, Co and Ni) supplementation to DAR were performed by running reactors in the laboratory under conditions similar to the reactor at LCRMS. Four reactors were run with first being a control reactor and the other three supplemented mainly with TM, yeast, and TM with yeast. The reactors were run for one month and there was essentially no improvement in unit methane production after metal and yeast supplementation. Also, the effect of ultrasonic treatment on MSW at a sample concentration of 4% and 8% solids at the sonication power of 93.3 W/L for 20 minutes yielded an increase in unit methane production by 24 % and 50 % for 4 % and 8 % samples respectively as compared to untreated MSW.

Additional studies were performed related to the post-treatment of DAR sludge from the DAR. Effects of caustic and microwave treatment were studied with caustic concentrations up to 2 N. Amongst the treatments considered, experiments indicated best results for only microwaving (no caustic) and 0.6 N treatments with an increase in unit methane production from DAR by 21 mLi gm COD and 12 mLi gm COD compared to untreated DAR sample. For the effect of caustic and heat treatment, caustic concentration was also varied up to 2 N and the samples were subjected to temperatures varying between ambient to 200°C. Samples at lower temperatures (ambient - 50°C) were treated between 1 Hr to 24 Hrs, whereas samples above 100°C were treated at 1 Hr treatment time. Overall, amongst various treatments considered, the sample treated at 175°C gave best results with an increase in unit methane production by 120 mLigm COD-DAR sludge (630 % as that of untreated sample). Also, amongst the samples treated in lower temperature range indicated best results for 50°C sample at 1 Hr with an increase in unit methane production by 40 mLigm COD-DAR sludge (210 % as that of untreated sample).