Effect of length: Diameter ratio in polyethylene biodigesters on gas production and effluent composition

Abstract

The treatments arranged as a 4*2 factorial were: Length and diameter ratio and retention time of plastic plug-flow biodigesters. The design was a single changeover with experimental periods of 40 days on each retention time. The length: diameter ratios wee 8:0.6, 5:0.6, 3:0.6 and 2:0.6m with hydraulic retention times of 10 or 20 days. For each retention time, the amount of manure (DM) was kept constant by adding water according to retention times. The manure solid concentration in the influent for 10 days retention time was 4 % and for 20 days was 8 %. The proportion of ammonia-N in total N increased markedly with different forms from the raw manure of 13.2±1.83, influent slurry in the range of 27.55± 3.05 and the effluent of 48.17±1.27 as pfor ent. Biogas production as litres per 100 litres liquid volume biodigester, and ammonia concentrations in effluent, did not differ between different length:diameter ratios nor between retention times.