Uncoupled Metabolism Stimulated by Chemical Uncoupler and Oxic-Settling-Anaerobic Combined Process to Reduce Excess Sludge Production

Abstract

The effects of three uncoupled metabolic systems (conventional activated sludge process with the addition of 3,3', 4',5-tetrachlorosalicylanilide [TCS], oxic-settling-anaerobic [OSA] process modified by insertion of a sludge-holding tank in the sludge return line, and TCS and OSA combined process) on reducing excess sludge production were studied. Compared with the control conventional activated sludge process, the most effective system was the combined process, which could reduce excess sludge production by 46.90%. The 180-d operation results confirmed that TCS is an effective chemical uncoupler in reducing the sludge yield but that it had an adverse effect on substrate removal capability, effluent nitrogen concentration, and sludge settleability. The OSA process decreased excess sludge production by only 26% but had less adverse effect on effluent quality and could improve sludge settleability. The effluent total phosphorous concentration of the three systems was slightly lower than of the control unit. Microbial populations were monitored by both microscopic and molecular biologic analysis method (polymerase chain reaction [PCR]-denaturing gradient gel electrophoresis [DGGE]). The presence of TCS caused metazoans to disappear and decreased the number and activity of protozoa. PCR amplification of 16S rRNA and sequent DGGE analysis found a shift in the diversity of the predominant species. The results imply that OSA combined with the chemical uncoupler process may effectively reduce excess sludge yield and not affect process performance significantly.

Reduction of Excess Sludge Production in an Activated Sludge System Based on Lysis-Cryptic Growth, Uncoupling Metabolism and Folic Acid Addition

“…This phenomenon may be attributed to the release of intracellular polymers under anoxic/anaerobic condition, which can act as floc-bridging agents to improve the settling properties of the sludge (Ye and Li, 2005), as observed for the average values obtained for SVI in OSA.R (76 mL/g and 64 mL/g, for OSA 16h .R and OSA 10h .R, respectively).…”

“…Nevertheless, several studies investigating folic acid addition described no significant interference in the substrate and nutrient removal efficiencies (Dubé et al, 2002;Bertacchi, 2005). Using TCS and TCS combined with the OSA process, Ye and Li (2005) demonstrated a decline in the nutrient removal rate, with effluent concentrations that were higher compared to the control system. However, as demonstrated in this study, the authors found that the substrate removal efficiency was not affected, and the system could also stimulate an increase in the rate of specific substrate uptake (Ye and Li, 2005;Low and Chase, 1998).…”

“…Using TCS and TCS combined with the OSA process, Ye and Li (2005) demonstrated a decline in the nutrient removal rate, with effluent concentrations that were higher compared to the control system. However, as demonstrated in this study, the authors found that the substrate removal efficiency was not affected, and the system could also stimulate an increase in the rate of specific substrate uptake (Ye and Li, 2005;Low and Chase, 1998). The TSS effluent concentrations were in the same range for all of the systems in both phases of the experiment; however, the phase 2 influent concentration was greater than the concentration in phase 1.…”

Metabolic uncoupling of Shewanella oneidensis MR‐1, under the influence of excess substrate and 3, 3′, 4′, 5‐tetrachlorosalicylanilide (TCS)

“…It belongs to a class of chemicals termed as protonophores because of their ability to shuttle electrons across the cell membrane. A number of previous studies have shown TCS to be capable of reducing the biomass yield of activated sludge cultures, effectively at lower concentrations compared to other uncouplers (Chen et al, 2000(Chen et al, , 2002(Chen et al, , 2004Ye and Li, 2005;Ye et al, 2003).…”

Comparing the effects of three pre-treatment disintegration techniques on aerobic sludge digestion: biodegradability enhancement and microbial community monitoring by PCR–DGGE

“…Previous studies have successfully used this technique to monitor the impact of sludge reduction processes on sludge microbial communities. For example, the use of a chemical uncoupler led to a shift in the predominant microbial species [14,15], the oxic-settling anaerobic process (OSA) led to more abundant species [16] and thermal treatment led to the increase in thermophilic bacteria populations [17]. Recently, Tan et al [18] demonstrated that there was a change in the microbial consortia after a heat-alkaline treatment.…”