Impact of Sudden Change in Feed Substrate Types on Steady Response of Suspended Growth Anaerobic Reactors

Abstract

Industries in developing countries add new production lines producing altogether different waste stream. This newer waste invariably finds its way to existing anaerobic treatment system causing gradual/sudden change in feed substrates affecting its steady performances. This study investigates steady response of anaerobic reactors subjected to sudden change in feed substrate types, assesses its impact on biomass and explores possibility of restoring pre-changed steady responses again. Three suspended growth batch anaerobic reactors (R1, R2 and R3) were started-up and operated in three different phases. In Phase–I, all the reactors were operated for 65 d on jaggery feed at an organic loading rate (OLR) of 1.40 kg COD/m3 d to obtain steady responses. In Phase–II, the change in feed substrate types were applied suddenly to R2 (from jaggery to cerelac) and R3 (from jaggery to neutralized acetic acid) while keeping R1 as the control and operated for 64 d on the same OLR. R2 gave steady response with reduced biogas production whereas complete cessation of biogas production was observed in R3. The total methanogenic activity of R3 biomass yielded comparable values with R1 and R2 biomasses indicating preservation of biomass integrity. When R2 and R3 were restored suddenly again with jaggery feed in Phase–III at the same OLR, R3 recovered quickly and all the reactors gave similar steady responses comparable to Phase–I.