Mechanistic insights into different illumination positions control algae production in anaerobic dynamic membrane filtration (AnDM) during decentralized wastewater treatment.

Sunlight illumination has the potential to control the stability and sustainability of dynamic membrane (DM) systems. In this study, an up-flow anaerobic sludge blanket (UASB) reactor was combined with DM under different illumination positions (direct, indirect and no illumination) to treat wastewater. Results indicated that the UASB achieved a COD removal up to 87.05 % with an average methane production of 0.28 L/d. Following treatment by the UASB, it was found that under illumination, the removal of organic substances by DM exhibited poor performance due to algal proliferation. However, the DM systems demonstrated efficient removal of ammonia nitrogen, ranging from 96.21 % to 97.67 % after stabilization. Total phosphorus removal was 45.72 %, and membrane flux remained stable when directly illuminated. Conversely, the DM system subjected to indirect illumination showed unstable membrane flux and severe fouling resistance. These findings offer valuable insights into optimizing illumination positions in DM systems under anaerobic conditions.

Improved stability of up-flow anaerobic sludge blanket reactor treating starch wastewater by pre-acidification: Impact on microbial community and metabolic dynamics.

Poor processing stability has been cited as the fatal shortcoming of the up-flow anaerobic sludge blanket (UASB) reactor treating starch wastewater (SW). In this study, the SW treatment performance in a one-stage UASB reactor and a pre-acidification equipped UASB process were evaluated together with the microbial dynamics. The results revealed that the pre-acidification provided improvements in terms of the substrate utilization diversity and the stability of the microbial community structure on the UASB reactor. Anaerolineaceae/Methanosaeta was the core functional microbiota in the pre-acidification equipped UASB reactor, indicated the superior abilities on the acetogenic methanogenesis of granules. The genus of Methanobacterium, a hydrogenotrophic methanogen was dominant in the archaeal community in the one-stage UASB reactor. The granules performed very strong hydrogen affinity in methane production, a small amount of propionate was detected in the effluent. These were abnormal, which suggested the high hydrogen turn-over rate in the one-stage UASB reactor.

Reduction of alkalinity supplementation for acid-based wastewater treatment using a thermophilic multi-feed upflow anaerobic sludge blanket reactor.

Generally, Shochu distillery wastewater treatment is required the addition of alkalinity agents for an increase of pH in the UASB reactor. However, to reduce the cost of alkalinity supplementation, cost-effective reactor operation method has been desired. This study aimed to reduce the alkalinity supplementation for a thermophilic (55°C) multi-feed up-flow anaerobic sludge blanket (MF UASB) reactor for the low-cost treatment of the wastewater from the production of the Japanese distilled alcohol called shochu. Shochu distillery wastewater contains high concentrations of organics (46,500-57,600 mgCOD L-1; COD: chemical oxygen demand) and volatile fatty acids (16,200-25,000 mgCOD L-1), and low pH (4.1-4.5). With alkalinity supplementation of 0.045 mgCaCO3 mgCOD-1 using 24% NaOH, the MF UASB reactor achieved an 87 ± 2% COD removal rate with an organic loading rate of 24 kgCOD m-3 day-1 for 554 days reactor operation (hydraulic retention time of 10 h and influent concentration of 10,000 mgCOD L-1). The organic removal rate decreased to 19 ± 3% in the MF UASB reactor when alkalinity supplementation was reduced to 0.015 mgCaCO3·mgCOD-1. In this study , the minimum alkalinity supplementation was 0.045 mgCaCO3 mgCOD-1 at an organic loading rate of 24 kgCOD m-3 day-1.

Biochar facilitates rapid restoration of methanogenesis by enhancing direct interspecies electron transfer after high organic loading shock.

This study evaluated the effectiveness of biochar addition against high organic loading shock (OLS) of 80 kg COD/m3/d in up-flow anaerobic sludge blanket (UASB) reactors (R1 with biochar; R2 without biochar). After OLS of 24 h, R2 suffered the irreversible acidification (pH of 5.42 ± 0.07) with low biogas production of 0.08 ± 0.01 m3/kg COD/d. In contrast, the biogas production in R1 restored rapidly to 0.33 ± 0.04 m3/kg COD/d, and effluent pH in R1 returned to 7.01 ± 0.22. With addition of biochar, potential direct interspecies electron transfer (DIET) partners, including volatile fatty acids (VFAs)-oxidizing bacteria (Bacteroidetes, Smithella, Desulfovibrio, Geobacter) and methanogens (Methanosaeta, Methanosarcina) were enriched in R1, which were conductive to maintain the balance of acidogenesis and methanogenesis. Moreover, the retention of Methanosaeta and Methanosarcina coupled with biochar maintained the structural stability of granular sludge in R1 under the pressure of OLS and VFAs, which guaranteed the stability of anaerobic system.

Application of in-situ H2-assisted biogas upgrading in high-rate anaerobic wastewater treatment.

The H2-assisted biogas upgrading approach has recently attracted much interest as a low-cost and environmentally friendly alternative to commonly used ex-situ/ physiochemical biogas upgrading techniques. However, most studies conducted to date have been limited to anaerobic solid-waste treatment characterized by flocculant sludge and low organic loading rates (OLR). In an attempt to expand its application to high-rate anaerobic wastewater treatment, an innovative two-stage up-flow anaerobic sludge blanket reactor system was employed using anaerobic granular sludge. We found that the CH4 content of product gas was consistently >90% and that H2 and CO2 concentrations stayed below 5%, even when OLR was increased from 1 to 5 g L-1 d-1 and H2 feeding rates were increased from 0.13 to 0.63 g L-1 d-1. We were also able to show that CO (5-10%) in H2-rich syngas didn't inhibit methanogenesis or had significant impact on microbial community structure, suggesting that H2-assisted biogas upgrading with H2-rich syngas is feasible.

Performance improvement and model of a bio-electrochemical system built-in up-flow anaerobic sludge blanket for treating ß-lactams pharmaceutical wastewater under different hydraulic retention time.

This paper focused on the performance of an up-flow bio-electrochemical system (UBES) for treating the ß-lactams pharmaceutical wastewater under different hydraulic retention time (HRT). UBES is added a bio-electrochemical system below the three-phase separator based on up-flow anaerobic sludge blanket (UASB). Comparisons of chemical oxygen demand (COD) removal, accumulation of volatile fatty acid (VFA) and biogas production were investigated during the 316-day operation time, which was divided into five parts with HRT of 96 h, 72 h, 48 h, 36 h and 20 h, respectively. The average COD removal efficiency of UBES could reach 45.3 ±â€¯7.5%, 72.2 ±â€¯3.5%, 86.2 ±â€¯1.4%, 75.9 ±â€¯1.8% and 64.9 ±â€¯2.0%, which were 2.4%, 6.1%, 6.4%, 10.2%, 8.7% more than those of UASB under different HRTs, respectively. Biogas production as well as methane production of UBES were significantly higher than UASB during the whole changing HRT process, the maximum methane yield of UBES was 0.31 ±â€¯0.07 L/gCODremoved. Accumulation of VFA in UBES was discovered to be lighter than UASB, the minimum average VFA in UBES was 131.9 ±â€¯18.5 mg/L, which was obtained at HRT of 48 h. These results proved that UBES can slow down the inhibition of VFA on methanogens to make sure a good performance on COD removal and biogas production than UASB. Moreover, the relationships between methane production and VFA, biogas production and COD consumption were analyzed. A cost and benefit were analyzed for evaluating the potential of UBES in practical applications compared with UASB. Finally, radial basis function neural network (RBFNN) model was developed and fitted well with the experimental data, which can be employed to predict the effluent quality of the UBES and UASB.

Degradation of guar in an up-flow anaerobic sludge blanket reactor: Impacts of salinity on performance robustness, granulation and microbial community.

Guar is extensively used during shale gas exploitation and is a major component in the flowback water. The viscosity of guar has adverse effects for the treatment of flowback water. This study investigated the degradation of guar at different salinities with an up-flow anaerobic sludge blanket (UASB) reactor. The effects of salinity on guar degradation, granular characteristics and microbial community were also studied. Results showed that more than 79% of guar was removed at hydraulic retention time (HRT) of 10 h, even at a concentration of 10000 mg L-1 of NaCl. Increasing salinity decreased granular size and hydrophobicity, but improved the secretion of EPS (especially for protein). Low salt condition 2500 mg L-1 presented faster degradation rate of guar. Salinity resulted in insignificant difference on bacterial community, but decreased the abundance of methanogens. Bacteroides, Prolixibacter and Pelolinea are essential genera in guar degradation. The results demonstrated the potential of UASB in the treatment of flowback water.

Role of biochar in the granulation of anaerobic sludge and improvement of electron transfer characteristics.

For improving the formation of anaerobic sludge granulation and its electron transfer characteristics, two up-flow anaerobic sludge blanket (UASB) reactors (R1 with 4 g/L biochar; R2 without biochar) were built in this study. With the addition of biochar, the lag time of methanogenesis was shortened by 28.6%, and the strengthening factor of COD removal rate reached 1.6. At the same time, the conductivity of granular sludge in R1 (23.29 ±â€¯0.99 µS/cm) was 2-fold of that in R2, and the integrity coefficient and hydrophobicity of granular sludge were improved significantly. According to the results of microbial community succession and electron transfer characteristics, the added biochar not only favors the anaerobic sludge granulation working as an inert core, but also facilitates the selective enrichment of potential direct interspecies electron transfer (DIET) partners such as Methanothrix and Geobacter spp. for enhancing the DIET process.

The feasibility study of autotrophic denitrification with iron sludge produced for sulfide control.

Ferric iron is widely dosed in wastewater treatment plants dealing with sulfide for septicity control, which generates a great amount of iron-rich chemical sludge that is challenging and costly to dispose. This study investigates the feasibility of using this iron sludge as the electron donor for autotrophic denitrification, not only realizing high nitrogen removal efficiency without additional carbon source requirement, but also partially mitigating iron-rich chemical sludge disposal and reduce sludge production by enriching low-yield autotrophic denitrifiers in the system. Both batch tests and performance monitoring of a lab-scale up-flow anaerobic sludge blanket reactor with a more than 300 days of operation were conducted. All the results confirmed the feasibility of using iron sludge as electron donor for autotrophic denitrification. The nitrate reduction rate with iron sludge was highly influenced by the type of ferrous electron donor and the electron donor/acceptor ratio. Ferrous hydroxide had significantly higher nitrate reduction rate than ferrous sulfide at the same electron donor/acceptor ratio. The nitrate reduction rate also accelerated with the increase of the electron donor/acceptor ratio. However, if the total surface area of the iron sludge is considered for comparison, it was shown that ferrous hydroxide and ferrous sulfide provided similar nitrate reduction rates of around 0.02 mmol N/m2/d in this study, indicating total surface area would be the key parameter for denitrification efficiency for the solid phase electron donor.

Enhanced treatment of Fischer-Tropsch (F-T) wastewater using the up-flow anaerobic sludge blanket coupled with bioelectrochemical system: Effect of electric field.

The coupling of bioelectrochemical system (BES) with an up-flow anaerobic sludge blanket (UASB) was established for enhanced Fischer-Tropsch (F-T) wastewater treatment while the UASB (control group) was operated in parallel. The presence of electric field could offer system a more reductive micro-environment that lower the ORP values and maintain the appropriate pH range, resulting in the higher chemical oxygen demand (COD) removal efficiency and methane production for BES-UASB (86.8% and 2.31±0.1L/(L·d)) while those values in control group were 72.1% and 1.77±0.08L/(L·d). In addition, the coupled system could promote sludge granulation to perform a positive effect on maintaining stability of pollutants removal. The high-throughput 16S rRNA gene pyrosequencing in this study further confirmed that the promoting direct interspecies electron transfer (DIET) between Geobacter and Methanosarcina might be established in BES-UASB to improve the syntrophic degradation of propionate and butyrate, finally facilitated completely methane production.

Elemental sulfur recovery and spatial distribution of functional bacteria and expressed genes under different carbon/nitrate/sulfide loadings in up-flow anaerobic sludge blanket reactors.

To characterize the impact of influent loading on elemental sulfur (S0) recovery during the denitrifying and sulfide oxidation process, three identical, lab-scale UASB reactors (30cm in length) were established in parallel under different influent acetate/nitrate/sulfide loadings, and the reactor performance and functional community structure were investigated. The highest S0 recovery was achieved at 77.9% when the acetate/nitrate/sulfide loading was set to 1.9/1.6/0.7kgd-1m-3. Under this condition, the genera Thauera, Sulfurimonas, and Azoarcus were predominant at 0-30, 0-10 and 20-30cm, respectively; meanwhile, the sqr gene was highly expressed at 0-30cm. However, as the influent loading was halved and doubled, S0 recovery was decreased to 27.9% and 45.1%, respectively. As the loading was halved, the bacterial distribution became heterogeneous, and certain autotrophic sulfide oxidation genera, such as Thiobacillus, dominated, especially at 20-30cm. As the loading doubled, the bacterial distribution was relatively homogeneous with Thauera and Azoarcus being predominant, and the nirK and sox genes were highly expressed. The study verified the importance of influent loading to regulate S0 recovery, which could be achieved as Thauera and Sulfurimonas dominated. An influent loading that was too low or too high gave rise to insufficient oxidation or over-oxidation of the sulfide and low S0 recovery performance.

Communities stimulated with ethanol to perform direct interspecies electron transfer for syntrophic metabolism of propionate and butyrate.

Direct interspecies electron transfer (DIET) has been considered as an alternative to interspecies H2 transfer (IHT) for syntrophic metabolism, but the microorganisms capable of metabolizing the key intermediates, such as propionate and butyrate, via DIET have yet to be described. A strategy of culturing the enrichments with ethanol as a DIET substrate to stimulate the communities for the syntrophic metabolism of propionate and/or butyrate was proposed in this study. The results showed that the syntrophic propionate and/or butyrate degradation was significantly improved in the ethanol-stimulated reactor when propionate/butyrate was the sole carbon source. The conductivity of the ethanol-stimulated enrichments was as 5 folds (for propionate)/76 folds (for butyrate) as that of the traditional enrichments (never ethanol fed). Microbial community analysis revealed that Geobacter species known to proceed DIET were only detected in the ethanol-stimulated enrichments. Together with the significant increase of Methanosaeta and Methanosarcina species in these enrichments, the potential DIET between Geobacter and Methanosaeta or Methanosarcina species might be established to improve the syntrophic propionate and/or butyrate degradation. Further experiments demonstrated that granular activated carbon (GAC) could improve the syntrophic metabolism of propionate and/or butyrate of the ethanol-stimulated enrichments, while almost no effects on the traditional enrichments. Also, the high H2 partial pressure could inhibit the syntrophic propionate and/or butyrate degradation of the traditional enrichments, but its effect on that of the ethanol-stimulated enrichments was negligible.

Potential enhancement of direct interspecies electron transfer for syntrophic metabolism of propionate and butyrate with biochar in up-flow anaerobic sludge blanket reactors.

Promoting direct interspecies electron transfer (DIET) to enhance syntrophic metabolism may be a strategy for accelerating the conversion of organic wastes to methane, but microorganisms capable of metabolizing propionate and butyrate via DIET under methanogenic conditions have yet to be identified. In an attempt to establish methanogenic communities metabolizing propionate or butyrate with DIET, enrichments were initiated with up-flow anaerobic sludge blanket (UASB), similar to those that were previously reported to support communities that metabolized ethanol with DIET that relied on direct biological electrical connections. In the absence of any amendments, microbial communities enriched were dominated by microorganisms closely related to pure cultures that are known to metabolize propionate or butyrate to acetate with production of H2. When biochar was added to the reactors there was a substantial enrichment on the biochar surface of 16S rRNA gene sequences closely related to Geobacter and Methanosaeta species known to participate in DIET.

On-site evaluation of the performance of a full-scale down-flow hanging sponge reactor as a post-treatment process of an up-flow anaerobic sludge blanket reactor for treating sewage in India.

A down-flow hanging sponge (DHS) reactor is a novel, unaerated, aerobic, biofilm reactor that is used to polish effluent received from an up-flow anaerobic sludge blanket (UASB) reactor for treating municipal sewage. A full-scale DHS reactor was constructed for post-treatment of a full-scale UASB reactor at a municipal sewage treatment plant in India. Performance of the DHS reactor was evaluated with respect to organic removal over 1800 days of continuous operation. The UASB+DHS system consistently produced effluent with chemical oxygen demand (COD), biochemical oxygen demand (BOD), and suspended solids (SS) values of 37, 6.0 and 19 mg L(-1), on average, respectively. The sludge yield of the DHS reactor was estimated to be 0.04 kg SS kg(-1) COD removed or 0.12 kg SS kg(-1) BOD removed, which is considerably lower than other aerobic treatment methods that have been employed for polishing UASB effluent.

Kinetics of municipal sewage degradation in EGSB and UASB reactors at 10°C / 西安交通大学学报·英文版

Kinetics of municipal sewage degradation in Expanded Granular Sludge Bed (EGSB) and Up-flow Anaerobic Sludge Blanket (UASB) reactors at 10°C were investigated via continuous experimental equipments. The results indicated that the whole reaction process can be simulated by the first-order dynamic equation model. Dynamic parameters such as k, Vmax and Ks of UASB in hydrolysis acidification stage were 1.08 d-1, 2.8 d-1 and 372 mg/L comparing to those of 1.18 d-1, 3.5 d-1 and 112 mg/L in the methanogenesis stage respectively. The EGSB's k, Vmax and Ks were 2.91 d-1, 14.3 d-1 and 470 mg/L in the hydrolysis acidification stage comparing to those of 1.68 d-1, 6.6 d-1 and 103 mg/L in the methanogenesis stage respectively. Comparison of k values of the two stages in UASB and EGSB indicates that hydrolysis acidification stage is the controlling step for the whole reaction process of UASB, while methanogenesis stage is the controlling step in EGSB. Compared with UASB, municipal sewage treatment by EGSB at 10°C can reach the same effluent requirement with lower retention time due to its effluent recirculation.

Kinetics of municipal sewage degradation in EGSB and UASB reactors at 10℃ / 药物分析学报

Kinetics of municipal sewage degradation in Expanded Granular Sludge Bed (EGSB) and Up-flow Anaerobic Sludge Blanket (UASB) reactors at 10℃ were investigated via continuous experimental equipments. The results indicated that the whole reaction process can be simulated by the first-order dynamic equation model. Dynamic parameters such as k, Vmax and Ks of UASB in hydrolysis acidification stage were 1.08 d-1, 2.8 d-1 and 372 mg/L comparing to those of 1.18 d-1, 3.5 d-1 and 112 mg/L in the methanogenesis stage respectively. The EGSB's k, Vmax and Ks were 2.91 d-1, 14.3 d-1 and 470 mg/L in the hydrolysis acidification stage comparing to those of 1.68 d-1, 6.6 d-1 and 103 mg/L in the methanogenesis stage respectively. Comparison of k values of the two stages in UASB and EGSB indicates that hydrolysis acidification stage is the controlling step for the whole reaction process of UASB, while methanogenesis stage is the controlling step in EGSB. Compared with UASB, municipal sewage treatment by EGSB at 10 ℃ can reach the same effluent requirement with lower retention time due to its effluent recirculation.