Effect of Low Temperatures on the Performance of an Anaerobic Baffled Reactor (ABR)

Abstract

The effect of a decrease in operating temperature on the performance of two 10 dm3 anaerobic baffled reactors (ABR) was examined in terms of steady state chemical oxygen demand (COD) removal efficiency. To minimise variations, and have a totally biodegradable feed, a synthetic carbohydrate (sucrose)–protein (meat extract) substrate was used. The reactors were operated at 20 h hydraulic retention time (HRT), 4 g dm−3 COD, and 35°C as a base‐line condition. Because of their different histories, the reactors responded differently to a decrease in operating temperature to 25°C. Reactor 1 remained stable at 97% COD removal, whereas Reactor 2 decreased to 93% removal, but rose to 97% after adding an effluent recycle of 0·25. At 15°C, the efficiency of Reactor 1 dropped to 75%, while the removal of Reactor 2 declined to 83%, and no improvement in efficiency occurred with an effluent recycle at 0·25. At 25°C, the decreased rate of catabolism of the slow‐growing syntrophs and methanogens resulted in a shift of the volatile fatty acids (VFA) peak to the second compartment. However, the biomass present in the reactor prevented VFAs breaking through in the effluent. Nevertheless, at 15°C VFAs were present in the effluent, perhaps due to the lower rates of metabolism and an increase in the Ks for VFAs. Finally, at 15°C part of the increase in the effluent COD was due to the enhanced production of soluble microbial products (SMP), or a decrease in their metabolism, with these compounds constituting some 10% of the inlet COD. © 1997 SCI.

A study of the kinetics and the effect of trace elements on mixed anaerobic fermentative biogas production by ternary quadratic general rotary unitized design

“…Biogas production is affected by pretreatment methods used for dung and straw and by temperature, the ratio of carbon to nitrogen, and trace elements. [19] Furthermore, it has been shown that trace elements are also essential nutrients for micro-organism activity [20,21] and for the structure of enzymes, such as methyl-coenzyme M reductase and the coenzyme M methyltransferase complex.…”

The effect of shock loads on SAF bioreactors for sewage treatment works

“…This greater removal suggests the process was not fully loaded. First stage bioreactors for carbon removal might be expected to operate at >1kgBOD/m 3 .day but better performance at higher organic loadings are reported in this study compared to some previous other work on high levels of performance, for example Masse and Massé [8] and Nachaiyasit [4]. This was attributed to higher biomass concentrations and better mixing.…”

“…Masse and Massé [8] reported on larger organic shock loads (OLR was increased from 2.60 TCODg/L/day to 3.92 TCODg/L/day with a maximum 6.25 TCODg/L/day) to four SBRs and also reported a small and temporary effect on performance efficiency measured as Soluble Chemical Oxygen Demand (SCOD) and Volatile Fatty Acid (VFA) concentrations. Although Nachaiyasit [4] believed that during hydraulic shocks the rate of mass transfer of substrate into the biomass aggregates appeared to be the limiting factor. The major factor controlling the overall performance rate during organic shocks should be the kinetics of the uptake and consumption by the biomass.…”

“…The effect of higher biomass concentrations in aerobic reactors usually enhances their stability rather than improves COD removal. In contrast, during hydraulic shocks the rate of mass transfer of substrate into the biomass aggregates is likely to be the limiting factor [4].…”

“…The literature has evidenced that bioreactors can handle short-term and long-term shock loads and sometimes even tolerate triple organic loading rate (OLR) [5][6][7][8]. The longer-term shock should lead to a new "steady state" which is identical to the original operating conditions in terms of TOC removal and other parameters [4]. The time to achieve steady state is proportional to biomass concentration, i.e.…”