Specific Methanogenic Activity Of Sludge Research Articles

Membrane fouling and performance of anaerobic ceramic membrane bioreactor treating phenol- and quinoline-containing wastewater: granular activated carbon vs polyaluminum chloride.

Although anaerobic membrane bioreactor (AnMBR) has been proposed for the treatment of phenolic wastewater, the membrane fouling is still a major obstacle. The effects of dosing of granular activated carbon (GAC) and polyaluminum chloride (PACl) on the treatment performance and membrane fouling of anaerobic ceramic membrane bioreactor were investigated for treating phenol- and quinoline-containing wastewater. The results suggested that the one-off dosing of GAC resulted in a decrease of protein/carbohydrate ratio, which might account for the aggravation of membrane fouling alongside with the decreased flocs size. Nevertheless, the substrate uptake rates (SUR) of phenol and quinoline, and the specific methanogenic activity of sludge at the GAC dosing stage of experimental reactor (R1) were 8.79 ± 0.63mg phenol g-1 MLVSS d-1, 7.01 ± 0.09mg quinoline g-1 MLVSS d-1 and 0.27 ± 0.01g CODCH4 g-1 MLVSS d-1, which were 1.69, 3.59 and 1.93 times higher than that of the control reactor (R2). The dosing of PACl reduced the membrane fouling rate by changing the floc structure of sludge, as well as the component of SMP and EPS. However, the substrate uptake rate of quinoline was declined. This work provides a comprehensive evaluation on the effect of GAC and PACl dosing on membrane fouling and performance of anaerobic ceramic membrane bioreactor treating phenol-and quinoline-containing wastewater.

Inhibition of ammonia on anaerobic digestion of synthetic coal gasification wastewater and recovery using struvite precipitation

Coal gasification wastewater (CGW) contains very high concentrations of phenols and ammonia. However, the potential impact of ammonia on the anaerobic digestion of phenols remained unclear. Firstly, the methanogens and phenols degraders had a good tolerance up to 1gL−1 of total ammonia nitrogen (TAN), but the substrate utilization rate for phenol, and specific methanogenic activity of sludge were decreased by 89% and 67% at 5g TAN L−1, and 94% and 100% at 10g TAN L−1, respectively. Secondly, the optimum struvite crystallization conditions (pH=8.5, 10g TAN L−1, n(Mg2+):n(TAN):n(PO43−)=1:1:1) were obtained by the orthogonal tests. Thirdly, the removal efficiencies of chemical oxygen demand (COD) and phenols were recovered to around 82% and 66%, respectively in the upflow anaerobic sludge blanket reactor using the pretreatment of struvite precipitation at 10g TAN L−1 and 1g phenols L−1. Therefore, anaerobic digestion coupled with struvite precipitation was considered as an alternative way for CGW treatment.

Performance robustness of the UASB reactors treating saline phenolic wastewater and analysis of microbial community structure

Anaerobic digestion was an important way to remove phenols from saline wastewater; however the anaerobic microorganisms were adversely affected by high concentration of salts. In order to clarify the performance robustness and microbial community structure for anaerobic digestion of saline phenolic wastewater, the UASB reactors were compared to treat phenolic wastewater under saline and non-saline conditions. The saline reactors were operated stably with phenols concentration increasing from 100 to 500mgL−1 at 10g Na+ L−1. The robustness of the saline reactors was weakened at 1000mg phenols L−1 and 10g Na+ L−1. However, the substrate utilization rates (SURs) for phenol, catechol, resorcinol, hydroquinone, and the specific methanogenic activity (SMA) of sludge were decreased by 95%, 85%, 97%, 78%, and 68%, respectively with phenols concentration enhancing from 1000 to 2000mgL−1. Moreover, the SURs for phenol, catechol, resorcinol, hydroquinone, and the SMA of sludge were reduced by 32%, 65%, 74%, 45%, and 59%, respectively with Na+ concentration increasing from 10 to 20gL−1, in comparison with the values obtained at 10g Na+ L−1 and 1000mg phenols L−1. Finally, the analysis of microbial community structure demonstrated that phenols degraders were less tolerant to high concentrations of Na+ and phenols than methanogens.

Efficient methanogenic degradation of alcohol ethoxylates and microbial community acclimation in treatment of municipal wastewater using a submerged anaerobic membrane bioreactor

The effect of alcohol ethoxylates on the treatment of municipal wastewater by a submerged anaerobic membrane bioreactor was investigated by a 400days operation including the treatment efficiency, methanogenic activity of sludge and microbial community structure. The results indicated that alcohol ethoxylates (5.0–200mg/L) was efficiently degraded and converted into methane due to the similar COD removal 95.5–98.8% and rising biogas production rate (2.30–4.25L/d) compared with control (96.8% and 2.55L/d). The microbes in sludge could copy with the presence of alcohol ethoxylates in wastewater by releasing more SMP and EPS, which caused a higher membrane fouling rate. Moreover, via long term acclimation, the specific methanogenic activity of sludge was greatly enhanced due to the changes of microbial community structure. Hence, the sludge self-acclimation to alcohol ethoxylates was responsible to the efficient methane recovery in treatment of municipal wastewater.

Enhanced treatment of wastewater from the vitamin C biosynthesis industry using a UASB reactor supplemented with zero-valent iron

The effects of zero-valent iron (Fe0) on the performance of a mesophilic upflow anaerobic sludge blanket (UASB) reactor treating high-strength wastewater from the vitamin C biosynthesis industry (VCW) was investigated during a 200-day period. The results showed that the chemical oxygen demand (COD) removal efficiency, CH4 content in biogas, specific methanogenic activity of sludge, and phosphate removal efficiency were significantly improved up to 81.8–96.1%, 76.5–79.6%, 1.71–2.87 g CH4-COD g−1 VSS d−1 and 68.5–85.2%, respectively, at elevated organic loading rates (OLRs) in the Fe0-amended reactor (RFe). In contrast, the corresponding values of 65.3–83.4%, 69.1–70.8%, 1.12–1.95 g CH4-COD g−1 VSS d−1 and 1.4–1.6%, respectively, were recorded in the control (R0). Elevated ferrous concentration of nearly 400 mg L−1 in sludge was detected in RFe, whereas in the effluent of both reactors it was low (<1.0 mg L−1). Batch tests further showed that Fe0 significantly enhanced the biodegradability of the VCW as shown by an increase in BOD/COD ratio from 0.41 to 0.65, and could serve as the electron donor for methanogenesis by anaerobic sludge, which were responsible for the differences between RFe and R0. The results suggest this integrated Fe0-microbial system is promising in facilitating the anaerobic digestion of VCW in UASB reactors.

Start-up of EGSB Reactor for Treatment of Wastewater Containing Pentachlorophenol

By using a Lab-scale Expanded Granular Sludge Bed (EGSB) reactor, the strategies of start-up and the changes of characteristics of granular sludge before and after start-up were investigated. In the first stage, the pentachlorophenol (PCP) concentration in wastewater was fixed at 5 mg/L, and the organic loading rate (OLR) gradually increased. The OLR increased to 5.4 kg COD/(m 3 -reactor d) after 25 days. Then began the second stage, OLR was stabilized as 5 kg COD/(m'-reactor d), while the PCP concentration was gradually increased. The PCP loading rate increased to 94.7 mg/(L-reactor d) in 63 days after the second stage start-up, the COD removal and PCP removal were 91.2% and 99.6% respectively. The EGSB reactor has the ability to bear PCP overloading to some extent. After the start-up was finished, the settlement velocity of granular sludge increased, the specific methanogenic activity of sludge and dechlorination rate of PCP were apparently increased. The results show that the two-stage start-up strategy is appropriate.

Thermophilic sulfate reduction and methanogenesis with methanol in a high rate anaerobic reactor

Sulfate reduction outcompeted methanogenesis at 65 degrees C and pH 7.5 in methanol and sulfate-fed expanded granular sludge bed reactors operated at hydraulic retention times (HRT) of 14 and 3.5 h, both under methanol-limiting and methanol-overloading conditions. After 100 and 50 days for the reactors operated at 14 and 3.5 h, respectively, sulfide production accounted for 80% of the methanol-COD consumed by the sludge. The specific methanogenic activity on methanol of the sludge from a reactor operated at HRTs of down to 3.5 h for a period of 4 months gradually decreased from 0. 83 gCOD. gVSS(-1). day(-1) at the start to a value of less than 0.05 gCOD. gVSS(-1). day(-1), showing that the relative number of methanogens decreased and eventually became very low. By contrast, the increase of the specific sulfidogenic activity of sludge from 0. 22 gCOD. gVSS(-1). day(-1) to a final value of 1.05 gCOD. gVSS(-1). day(-1) showed that sulfate reducing bacteria were enriched. Methanol degradation by a methanogenic culture obtained from a reactor by serial dilution of the sludge was inhibited in the presence of vancomycin, indicating that methanogenesis directly from methanol was not important. H(2)/CO(2) and formate, but not acetate, were degraded to methane in the presence of vancomycin. These results indicated that methanol degradation to methane occurs via the intermediates H(2)/CO(2) and formate. The high and low specific methanogenic activity of sludge on H(2)/CO(2) and formate, respectively, indicated that the former substrate probably acts as the main electron donor for the methanogens during methanol degradation. As sulfate reduction in the sludge was also strongly supported by hydrogen, competition between sulfate reducing bacteria and methanogens in the sludge seemed to be mainly for this substrate. Sulfate elimination rates of up to 15 gSO(4)(2-)/L per day were achieved in the reactors. Biomass retention limited the sulfate elimination rate.