Nitrifying and denitrifying bacteria in aerobic granules formed in sequencing batch airlift reactors

The purpose of this study was to investigate nitrifying bacteria and denitrifying bacteria isolated from aerobic granules. Aerobic granules were formed in an internal-circulate sequencing batch airlift reactor (SBAR) and biodegradation of NH₃ ^?-N was analyzed in the reactor. Bacteria were isolated and determined from aerobic granules using selected media. The growth properties and morphology of bacteria colonies were observed by controlling aerobic or anaerobic conditions in the culture medium. It was found that bacteria in aerobic granules were diverse and some of them were facultative aerobes. The diversity of bacteria in aerobic granules was a premise of simultaneous nitrification and denitrification.     

Investigation of As, Mn and Fe fixation inside the aquifer during groundwater exploitation in the experimental system imitated natural conditions

Water-dissolved oxygen was supplied into anaerobic aquifer , which oxidized Fe(II), Mn(II) and trivalent arsenic and changed them into undissolved solid matter through hydrolysis, precipitation, co-precipitation and adsorption processes. The experiment was carried out on the column imitated a bore core of anaerobic aquifer with water phase containing Fe(II), Mn(II), As(III) concentration of 45.12 mg/L, 14.52 mg/L, 219.4 μg/L, respectively and other ions similarly composition in groundwater. After 6 days of air supply, concentration of iron reduced to 0.38 mg/L, manganese to 0.4 mg/L, arsenic to 9.8 μg/L (equivalent 99.16% of iron, 97.25% of manganese and 95.53% of arsenic fixed), and for other ions, the concentration changed almost according to general principles. Ion phosphate and silicate strongly influenced on arsenic removal but supported iron and manganese precipitation from water phase. Based on the experimental results, new model of groundwater exploitation was proposed.     

Treatment of methylene blue-containing wastewater using microorganisms supported on granular activated carbon under packed column operation

We studied the feasibility of using biological granular activated carbon-packed column in treating methylene blue-containing wastewater. The granular activated carbon with immobilized microbes was packed into a column and fed with 3 liter methylene blue-containing wastewater daily. With initial 1350 mg/l of methylene blue and 1550 mg/l of chemical oxygen demand, it was observed that the colour and chemical oxygen demand removal efficiencies were 99 and 78%, respectively. The high treatment performance of the system could be due to the simultaneous adsorption and biodegradation processes and advantages of immobilized microbes compare to suspended cell system.     

活性艳红X-3B的厌氧生物降解与机理

以活性艳红X-3B(RBR)为研究对象,分3个不同浓度组研究其在厌氧颗粒污泥作用下的降解性能,并采用生物降解动力学方程拟合其降解过程,同时利用GC-MS分析RBR的生物降解途径.试验结果表明,RBR在厌氧颗粒污泥中降解性能很好,去除率可达93.67%,且其降解过程符合二级反应动力学,其半衰期约为3.561 h.从GC-MS和UV-可见光谱的分析得出,RBR在厌氧颗粒污泥的作用下偶氮键断裂,且生成的芳香胺类化合物进一步降解为小分子的烃类、酚类、醇类和脂类化合物.     

Concept and application of anaerobic suspended granular sludge bed （SGSB） reactor for wastewater treatment

Bed expansion serves an important function in the design and operation of an upflow anaerobic reactor. An analysis of the flow pattern of expanded granular sludge bed （EGSB） reactors shows that most EGSB reactors do not behave as expanded bed reactors, as is widely perceived. Rather, these reactors behave as fluidized bed reactors based on the classic chemical reactor theory. In this paper, four bed expansion modes, divided as static bed, expanded bed, suspended bed, and fluidized bed, for bioreactors are proposed. A high-rate anaerobic suspended granular sludge bed （SGSB） reactor was then developed. The SGSB reactor is an upflow anaerobic reactor, and its expansion degree can be easily controlled within a range to maintain the suspended status of the sludge bed by controlling upfiow velocity. The results of the full-scale reactor confirmed that the use of SGSB reactors is advantageous. The full-scale SGSB reactor runs stably and achieves high COD removal efficiency （about 90%） at high loading rates （average 40 kg-COD·m^-3·d^-1, maximum to 52 kg·COD·m^-3 ·d^-1） based on the SGSB theory, and its expansion degree is between 22% and 37%.     

Electrocatalytic biofilm reactor for effective and energy-efficient azo dye degradation: the synergistic effect of MnOx/Ti flow-through anode and biofilm on the cathode

● MnO _x /Ti flow-through anode was coupled with the biofilm-attached cathode in ECBR. ● ECBR was able to enhance the azo dye removal and reduce the energy consumption. ● Mn^IV=O generated on the electrified MnO _x /Ti anode catalyzed the azo dye oxidation. ● Aerobic heterotrophic bacteria on the cathode degraded azo dye intermediate products. ● Biodegradation of intermediate products was stimulated under the electric field. Dyeing wastewater treatment remains a challenge. Although effective, the in-series process using electrochemical oxidation as the pre- or post-treatment of biodegradation is long. This study proposes a compact dual-chamber electrocatalytic biofilm reactor (ECBR) to complete azo dye decolorization and mineralization in a single unit via anodic oxidation on a MnO_x/Ti flow-through anode followed by cathodic biodegradation on carbon felts. Compared with the electrocatalytic reactor with a stainless-steel cathode (ECR-SS) and the biofilm reactor (BR), the ECBR increased the chemical oxygen demand (COD) removal efficiency by 24 % and 31 % (600 mg/L Acid Orange 7 as the feed, current of 6 mA), respectively. The COD removal efficiency of the ECBR was even higher than the sum of those of ECR-SS and BR. The ECBR also reduced the energy consumption (3.07 kWh/kg COD) by approximately half compared with ECR-SS. The advantages of the ECBR in azo dye removal were attributed to the synergistic effect of the MnO_x/Ti flow-through anode and cathodic biofilms. Catalyzed by Mn^IV=O generated on the MnO_x/Ti anode under a low applied current, azo dyes were oxidized and decolored. The intermediate products with improved biodegradability were further mineralized by the cathodic aerobic heterotrophic bacteria (non-electrochemically active) under the stimulation of the applied current. Taking advantage of the mutual interactions among the electricity, anode, and bacteria, this study provides a novel and compact process for the effective and energy-efficient treatment of azo dye wastewater.     

Performance of a hybrid anaerobic-contact oxidation biofilm baffled reactor for the treatment of decentralized molasses wastewater

A novel hybrid anaerobic-contact oxidation biofilm baffled reactor （HAOBR） was developed to simultaneously remove nitrogenous and carbonaceous organic pollutants from decentralized molasses wastewater in the study. The study was based on the inoculation of anaerobic granule sludge in anaerobic compartments and the installation of combination filler in aerobic compartments. The performance of reactor system was studied regarding the hydraulic retention time （HRT）, microbial characteristics and the gas water ratio （GWR）. When the HRT was 24h and the GWR was 20：1, total ammonia and chemical oxygen demand （COD） of the effluent were reduced by 99% and 91.8%, respectively. The reactor performed stably for treating decentralized molasses wastewater. The good performance of the reactor can be attributed to the high resistance of COD and hydraulic shock loads. In addition, the high solid retention time of contact oxidation biofilm contributed to stable performance of the reactor.     

Anaerobic treatment of wastewater containing methanol in upflow anaerobic sludge bed (UASB) reactor

The direct conversion of methanol into methane is the main process in anaerobic treatment of methanol containing wastewater. However, acetic acid can also be produced from methanol theoretically, which may probably result in an abrupt pH drop and deteriorate the anaerobic process. Therefore, it is interesting to know what would really happen in an anaerobic reactor treating methanol wastewater. In this study, an up-flow anaerobic sludge bed (UASB) reactor treating methanol wastewater was operated. The chemical oxygen demand (COD), acetic acid and pH of the effluent were monitored at different loadings and influent alkalinity. The results showed that the anaerobic reactor could be operated steadily at as low as 119 mg/L of influent alkalinity and high organic loading rate with no obvious pH drops. Volatile fatty acids accumulation was not observed even at strong shock loadings. The microorganisms in the sludge at the end of the test became homogeneous in morphology, which were mainly spherical or spheroidal in shape.     

Coupled aerobic and anoxic biodegradation for quinoline and nitrogen removals

Quinoline (C₉H₇N) commonly occurs in wastewaters from the chemical, pharmaceutical, and dyeing industries. As quinoline is biodegraded, nitrogen is released as ammonium. Total-N removal requires that the ammonium-N be nitrified and then denitrified. The objective of this study was to couple quinoline biodegradation with total-N removal. In a proof-of-concept step, activated sludge was sequenced from aerobic to anoxic stages. The ammonium nitrogen released from quinoline biodegradation in the aerobic stage was nitrified to nitrate in parallel. Anoxic biodegradation of the aerobic effluent then brought about nitrogen and COD removals through denitrification. Then, simultaneous quinoline biodegradation and total-N removal were demonstrated in a novel airlift internal loop biofilm reactor (AILBR) having aerobic and anoxic zones. Experimental results showed that the AILBR could achieve complete removal of quinoline, 91% COD removal, and 85% total-N removal when glucose added as a supplemental electron donor once nitrate was formed.     

Enhanced 4-chlorophenol biodegradation by integrating Fe2O3 nanoparticles into an anaerobic reactor: Long-term performance and underlying mechanism

• 4-chlorophenol biodegradation could be enhanced in Fe₂O₃ coupled anaerobic system. • Metabolic activity and electron transport could be improved by Fe₂O₃ nanoparticles. • Functional microbial communities could be enriched in coupled anaerobic system. • Possible synergistic mechanism involved in enhanced dechlorination was proposed. Fe₂O₃ nanoparticles have been reported to enhance the dechlorination performance of anaerobic systems, but the underlying mechanism has not been clarified. This study evaluated the technical feasibility, system stability, microbial biodiversity and the underlying mechanism involved in a Fe₂O₃ nanoparticle-coupled anaerobic system treating 4-chlorophenol (4-CP) wastewater. The results demonstrated that the 4-CP and total organic carbon (TOC) removal efficiencies in the Fe₂O₃-coupled up-flow anaerobic sludge blanket (UASB) were always higher than 97% and 90% during long-term operation, verifying the long-term stability of the Fe₂O₃-coupled UASB. The 4-CP and TOC removal efficiencies in the coupled UASB increased by 42.9±0.4% and 27.5±0.7% compared to the control UASB system. Adding Fe₂O₃ nanoparticles promoted the enrichment of species involved in dechlorination, fermentation, electron transfer and acetoclastic methanogenesis, and significantly enhanced the extracellular electron transfer ability, electron transport activity and conductivity of anaerobic sludge, leading to enhanced 4-CP biodegradation performance. A possible synergistic mechanism involved in enhanced anaerobic 4-CP biodegradation by Fe₂O₃ nanoparticles was proposed.     

Metallic wastewater treatment by sulfate reduction using anaerobic rotating biological contactor reactor under high metal loading conditions

An-RBC reactor is highly suited to treat metallic wastewater. Metal removal is due to sulfide precipitation via sulfate reduction by SRB. Cu(II) removal was the best among the different heavy metals. Maximum metal removal is achieved at low metal loading condition. Metal removal matched well with the solubility product values of respective metal sulfide salts. This study was aimed at investigating the performance of anaerobic rotating biological contactor reactor treating synthetic wastewater containing a mixture of heavy metals under sulfate reducing condition. Statistically valid factorial design of experiments was carried out to understand the dynamics of metal removal using this bioreactor system. Copper removal was maximum (>98%), followed by other heavy metals at their respective low inlet concentrations. Metal loading rates less than 3.7 mg/L?h in case of Cu(II); less than 1.69 mg/L?h for Ni(II), Pb(II), Zn(II), Fe(III) and Cd(II) are favorable to the performance of the An-RBC reactor. Removal efficiency of the heavy metals from mixture depended on the metal species and their inlet loading concentrations. Analysis of metal precipitates formed in the sulfidogenic bioreactor by field emission scanning electron microscopy along with energy dispersive X-ray spectroscopy (FESEM-EDX) confirmed metal sulfide precipitation by SRB. All these results clearly revealed that the attached growth biofilm bioreactor is well suited for heavy metal removal from complex mixture.     

Effect of dilution rate on dynamic and steady-state biofilm characteristics during phenol biodegradation by immobilized Pseudomonas desmolyticum cells in a pulsed plate bioreactor

Continuous pulsed plate bioreactor (PPBR) was used for phenol biodegradation. Pseudomonas desmolyticum cells immobilized on granular activated carbon was used. Dynamic and steady state biofilm characteristics depend on dilution rate (DR). Lower DR favour phenol degradation and uniform, thick biofilm formation. Exo polymeric substance production in biofilm are favoured at lower dilution rates. Pulsed plate bioreactor (PPBR) is a biofilm reactor which has been proven to be very efficient in phenol biodegradation. The present paper reports the studies on the effect of dilution rate on the physical, chemical and morphological characteristics of biofilms formed by the cells of Pseudomonas desmolyticum on granular activated carbon (GAC) in PPBR during biodegradation of phenol. The percentage degradation of phenol decreased from 99% to 73% with an increase in dilution rate from 0.33 h?1 to 0.99 h?1 showing that residence time in the reactor governs the phenol removal efficiency rather than the external mass transfer limitations. Lower dilution rates favor higher production of biomass, extracellular polymeric substances (EPS) as well as the protein, carbohydrate and humic substances content of EPS. Increase in dilution rate leads to decrease in biofilm thickness, biofilm dry density, and attached dry biomass, transforming the biofilm from dense, smooth compact structure to a rough and patchy structure. Thus, the performance of PPBR in terms of dynamic and steady-state biofilm characteristics associated with phenol biodegradation is a strong function of dilution rate. Operation of PPBR at lower dilution rates is recommended for continuous biologic treatment of wastewaters for phenol removal.     

Feasibility assessment of up-flow anaerobic sludge blanket treatment of sulfamethoxazole pharmaceutical wastewater

The UASB system successfully treated sulfamethoxazole pharmaceutical wastewater. High concentration sulfate of this wastewater was the main refractory factor. UASB recovery performance after a few days of inflow arrest was studied. The optimal UASB operating conditions for practical application were determined. Treatment of sulfamethoxazole pharmaceutical wastewater is a big challenge. In this study, a series of anaerobic evaluation tests on pharmaceutical wastewater from different operating units was conducted to evaluate the feasibility of using anaerobic digestion, and the results indicated that the key refractory factor for anaerobic treatment of this wastewater was the high sulfate concentration. A laboratory-scale up-flow anaerobic sludge blanket (UASB) reactor was operated for 195 days to investigate the effects of the influent chemical oxygen demand (COD), organic loading rate (OLR), and COD/SO₄^2? ratio on the biodegradation of sulfamethoxazole in pharmaceutical wastewater and the process performance. The electron flow indicated that methanogenesis was still the dominant reaction although sulfidogenesis was enhanced with a stepwise decrease in the influent COD/SO₄^2? ratio. For the treated sulfamethoxazole pharmaceutical wastewater, a COD of 4983 mg/L (diluted by 50%), OLR of 2.5 kg COD/(m³·d), and COD/SO₄^2? ratio of more than 5 were suitable for practical applications. The recovery performance indicated that the system could resume operation quickly even if production was halted for a few days.     

Degradation of ammonium dinitramide (ADN) in digested sewage sludge under strict anaerobic conditions

The biodegradation of one popular nitramine energetics, ammonium dinitramide (ADN) by mixture of denitrifying bacterial species was investigated. ADN was observed to be effectively mineralized in the anaerobic mixed culture. The initial ADN concentration of 250 mg/L was reduced to non‐detectable levels (> 99% removal efficiency) in 5 days of incubation under anaerobic conditions. Final products generated from anaerobic degradation of nitramine energetics by anaerobic metabolism were NH₄ ⁺, CH₄, and CO₂ that were released to the environment with the denitrifiers’ growth. In addition, it was found that the activity of denitrifiers was inhibited by high concentration of ammonia generated through the degradation reactions of energetic nitrites.     

硝基苯降解菌在厌氧序批式反应器中处理硝基苯废水的应用

通过接种硝基苯降解菌于厌氧序批式反应器（ASBR），研究静态试验条件下和厌氧序批式工艺对硝基苯的降解规律，研究表明，应用生物强化技术处理硝基苯废水，具有很高的处理效率。     

Anaerobic decolorization of an azo dye by a mixed culture

Wool dyeing wastewater contains xenobiotic compounds that can be removed by biotechnological processes. Studies on various dyes showed that anaerobic processes are suitable to alter azo dyes as a first step of the biodegradation process. These compounds are reduced by anaerobic consortia to aromatic amines and its ultimate degradation can be achieved by a further aerobic treatment.

Studies on degradation rate of an wool acid dye were performed in batch systems inoculated with anaerobic biomass. A commercial diazo dye, Acid Red 73, was added to the synthetic medium in which glucose was used as sole carbon source.

Results indicated that the Acid Red 73 was partially degraded by a mixed culture of anaerobic bacteria and a decolorization of 90% was obtained. Kinetics studies on removal of the colour showed that the decolorization rate was several times faster than the degradation rate of glucose for a range of dye concentrations between 60 mg/L and 400 mg/L. A first order kinetic model was used for dye concentrations up to 200 mg/L. For higher concentrations a model similar to the Michaelis‐Menten equation was better fitted to the experimental data.     

石油烃厌氧生物降解代谢产物研究进展

石油烃厌氧生物降解代谢产物的分析对于石油烃厌氧降解机制的研究、功能微生物的筛选以及微生物活动的原位监测具有指示性作用.综述了近年来石油烃厌氧生物降解代谢产物的研究进展.石油烃厌氧降解的初始活化方式主要包括脱氢羟基化、加延胡索酸以及羧化等.其中,加延胡索酸是不同种类的微生物通常采用的代谢方式.同时,将代谢产物按照气体、无机离子和有机酸进行分类,并针对各类物质特别是瞬时性、低浓度的有机酸类产物常采用的分析方法进行归纳.通过实例强调了代谢产物作为潜在生物标记物的应用,并对石油烃厌氧降解代谢产物分析方法的发展提出展望.图3参58     

Comparison of metabolic nitramine degradation by denitrifying species

The biodegradation of two popular nitramine energetics were investigated. The HMX (octa‐hydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine) was mineralized by anaerobic mixed denitrifiers in digested sewage sludge culture. An initial HMX concentration of 120 mg/L decreased to a non‐detectable level (> 99% removal efficiency) in 8 days of incubation under strict anaerobic conditions. It was, however, not effectively metabolized by single denitrifying species, P. aeruginosa, B. subtilis in a nitrogen limiting condition under their optimum growth conditions. The other nitramine energetic, ADN (ammonium dinitramide), was mineralized well in the anaerobic mixed culture. The initial ADN concentration of 250 mg/L was reduced to non‐detectable levels (> 99% removal efficiency) in 5 days of incubation under anaerobic conditions. These results show that the anaerobic mixed culture, compared to the pure monoculture, is superior in the degradation of nitramine energetics.     

Anaerobic biodegradation of trimethoprim with sulfate as an electron acceptor

Anaerobic biodegradation of trimethoprim (TMP) coupled with sulfate reduction. Demethylation of TMP is the first step in the acclimated microbial consortia. The potential degraders and fermenters were enriched in the acclimated consortia. Activated sludge and river sediment had similar core microbiomes. Trimethoprim (TMP) is an antibiotic frequently detected in various environments. Microorganisms are the main drivers of emerging antibiotic contaminant degradation in the environment. However, the feasibility and stability of the anaerobic biodegradation of TMP with sulfate as an electron acceptor remain poorly understood. Here, TMP-degrading microbial consortia were successfully enriched from municipal activated sludge (AS) and river sediment (RS) as the initial inoculums. The acclimated consortia were capable of transforming TMP through demethylation, and the hydroxyl-substituted demethylated product (4-desmethyl-TMP) was further degraded. The biodegradation of TMP followed a 3-parameter sigmoid kinetic model. The potential degraders (Acetobacterium, Desulfovibrio, Desulfobulbus, and unidentified Peptococcaceae) and fermenters (Lentimicrobium and Petrimonas) were significantly enriched in the acclimated consortia. The AS- and RS-acclimated TMP-degrading consortia had similar core microbiomes. The anaerobic biodegradation of TMP could be coupled with sulfate respiration, which gives new insights into the antibiotic fate in real environments and provides a new route for the bioremediation of antibiotic-contaminated environments.     

Treatment of spent wash in anaerobic mesophilic suspended growth reactor (AMSGR)

Approximately 400 KL of spent wash or vinasse per annum is generated at an average COD concentration of 100,000 mg/l, by over 250 distilleries in India. There is an urgent need to develop, assess and use ecofriendly methods for the disposal of this high strength wastewater. Therefore, an attempt was made to investigate a few aspects of anaerobic digestion of spent wash collected from a distillery. The study was carried out in a 4 L laboratory scale anaerobic mesophilic suspended growth reactor. After the successful startup, the organic loading was increased stepwise to assess the performance of the reactor. During the study period, biogas generated was recorded and the maximum gas generated was found to be 16.9 L at an Organic Loading Rate (OLR) of 38 g COD/L. A 500% increase in the Volatile Fatty Acid (VFA) concentration (2150 mg/L) was observed, when the OLR was increased from 38 to 39 g COD/L. During the souring phase the removal of COD, Total Solids (TS) and Volatile Solids (VS) were in the order of 52%, 40% and 46% respectively. The methane content in the biogas varied from 65% to 75%.