Anaerobic Biological Treatment Research Articles

Coupling Fe3O4 and micro-hydrogen for enhancing the anaerobic bio-conversion of phenol: Methanogenesis pathway and interspecies electron transfer

Low anaerobic biological conversion rate is a challenge in the anaerobic biological treatment of phenol wastewater. The dominant syntrophic acetate oxidation and hydrogenotrophic methanogenesis (SAO-HM) pathway is expected to solve the problem. However, there are raw studies on artificially simulating a dominant SAO-HM pathway for enhancing the anaerobic bio-conversion of phenol. In this study, Fe3O4 and micro-hydrogen (Fe3O4/H2) was used to strengthen the anaerobic bio-conversion of phenol by simulating the dominant SAO-HM pathway. The results suggested Fe3O4 and H2 had a coupling promotion on the anaerobic bio-conversion of phenol and Fe3O4/H2 increased the relative abundance of Syntrophus (29.35%), Syntrophorhabdu (3.27%), Clostridium (3.01%) and Methanobacterium (65.74%), indicating Fe3O4/H2 formed a dominant SAO-HM pathway. However, Fe3O4/H2 obviously reduced the conductivity of sludge, the extracellular protein and the functional gens pilA, pilB and OmcS, implying direct interspecies electron transfer (DIET) generated by Fe3O4 was interfered by micro hydrogen in extracellular electron transport process which reduced the efficiency of extracellular electron transport. This study remind that extracellular electron transport cannot be ignored in the dominate SAO-HM pathway for the anaerobic bio-conversion of phenol.

EVALUATING WASTEWATER TREATMENT EFFICIENCY OF MEDICAL CENTERS IN BINH DUONG PROVINCE

This paper presents a comprehensive analysis of the wastewater management system implemented at a medical center located within the Bau Bang Industrial Park in Binh Duong province, Vietnam. With a staff of 166 and 60 beds, the facility operates in accordance with TCVN 4470:2012 General Hospital design standards, serving a diverse range of water demands including domestic, medical, and auxiliary requirements. The wastewater management system is meticulously designed to handle both rainwater and wastewater separately. Rainwater is efficiently collected through surface and roof drainage networks, while domestic and medical wastewater undergo discrete collection processes. The medical center's wastewater treatment facility, operating at a capacity of 100 m³/day, employs a multistage treatment process to ensure compliance with stringent regulatory standards (QCVN 28:2010/BTNMT, column B, K = 1). This process includes preliminary treatment, anaerobic and aerobic biological treatment, membrane filtration, and disinfection. The facility consistently meets quality parameters outlined in QCVN 28:2010/BTNMT, exhibiting effective removal rates for organic pollutants, suspended solids, ammonia, phosphates, and pathogens. Furthermore, the medical center demonstrates commendable environmental stewardship through its stormwater drainage infrastructure, which integrates seamlessly with the local drainage network, safeguarding against environmental contamination. Overall, the wastewater management practices at the medical center exemplify best practices in environmental management within the healthcare sector. This study provides valuable insights into the design, implementation, and performance evaluation of wastewater treatment systems in industrial settings, contributing to the global discourse on sustainable wastewater management practices.

Ceramics as potential materials in pollution prevention and control

AbstractThe social progress, economic growth, and meteoric urbanization prompt the exploitation of available resources triggering the contagion of the biological and physical elements of the atmosphere irrationally causing global environmental pollution. Environmental contamination monitoring is a dire necessity. Although a number of technologies find mention in the literature for environmental remediation, however, environmental catalysis is an advanced steadily growing technique for pollution abatement. In this dimension, ceramic materials have turned heads due to their wide‐scale application areas. Hitherto, research is being done on advanced ceramics to fabricate novel modules for energy storage applications, in designing green buildings, pollution rheostats, and environmental engineering. This article deals with the abatement of environmental contaminants by adopting various methodologies such as aerobic and anaerobic biological treatments, adsorption, chemical oxidation, membrane separation, photocatalysis, ozonation using the ceramic as precursor materials. The ceramic membranes are cost‐effective, ecofriendly, efficacious, and green approach to obliterate toxins and harmful gases released in environment. Even though, limited literature is available on the abolition of harmful contaminants from air and soil using ceramic materials, an attempt has been made to present currently available data with best of our knowledge. This article will sensitize researchers to refabricate novel materials for environment sustainability.

The important role of high sludge concentration in anaerobic biological systems with low COD/SO42- sulfate-containing wastewater predicted by machine learning: Insights from microbial community and metabolic pathways

In anaerobic biological systems, sulfate reduction efficiency is influenced by multiple factors synergistically, particularly under low chemical oxygen demand-to-sulfate ratio (COD/SO42-) conditions. Enhancing sulfate reduction efficiency under low COD/SO42- conditions is challenging due to the deficiency of electron donors. In this study, two anaerobic systems were operated with a gradual decrease in COD/SO42-. The primary objective was to investigate the correlations among various influential factors, the efficacy of sulfate reduction, and the progression of microbial communities. The results showed that even with a decrease in COD/SO42- to 0.1, the sulfate reduction efficiency could reach 70% under high sludge concentration. Machine learning predictions identified sludge concentration as the most influential factor under low COD/SO42- conditions. The functional gene analysis confirmed that the sulfate reduction under high sludge concentration was primarily governed by the dissimilatory pathway and exhibited minimal reliance on COD/SO42-. These findings provide theoretical support and a novel approach for the anaerobic biological treatment of sulfate-containing wastewater under low COD/SO42- conditions.

Magnetite encapsulated in carbon shell particles (Fe3O4@C) to boost anaerobic methanogenesis of chloramphenicol wastewater

Magnetite (Fe3O4) is extensively applied to enhance efficacy of anaerobic biological treatment systems designed for refractory wastewater. However, the interaction between magnetite, organic pollutants and microorganisms in digestion solution is constrained by magnetic attraction. To overcome this limitation and prevent magnetite aggregation, the core-shell composite materials with carbon outer layer enveloping magnetite core particles (Fe3O4@C) were developed. The impact of Fe3O4@C with varying Fe3O4 mass ratios on the anaerobic methanogenesis capability in the treatment of chloramphenicol (CAP) wastewater was investigated. Experimental results demonstrated that Fe3O4@C not only enhanced chemical oxygen demand (COD) removal efficiency and biogas production by 2.42-13.18% and by 7.53%-23.25%, respectively, but also reduced the inhibition of microbial activity caused by toxic substances and the secretion of extracellular polymeric substances (EPS) by microorganisms responding to adverse environments. The reinforcing capability of Fe3O4@C increased with the rise in Fe3O4 content. Furthermore, High-throughput pyrosequencing illustrated that Fe3O4@C enhanced the relative abundance of Methanobacterium, a hydrogen-utilizing methanogen capable of participating in direct interspecies electron transfer (DIET), by 5%. Metagenomic analysis indicated that Fe3O4@C improved the decomposition of complex organics into simpler compounds by elevating functional genes encoding key enzymes associated with organic matter metabolism, acetogenesis, and hydrogenophilic methanogenesis pathways. These findings suggest that Fe3O4@C have the potential to strengthen both the hydrogenophilic methanogenesis and DIET processes. This insight offers a novel perspective on the anaerobic bioaugmentation of high-concentration refractory organic wastewater.

Adsorption enhanced biological treatment of hydrothermal liquefaction aqueous phase derived from municipal sludge

Hydrothermal liquefaction (HTL) is a promising method for municipal sludge valorization through waste minimization and biofuel production. The process wastewater, HTL aqueous, presents a significant challenge for scale-up due to recalcitrant compounds. In this study, granular activated carbon (GAC) was used to remove potential inhibitors from HTL aqueous through adsorption to enhance aerobic and anaerobic biological treatment. GAC removed up to 61 % chemical oxygen demand (COD), 50 % biochemical oxygen demand (BOD) and potential inhibitors, such as total phenolic compounds (87 %) and N-heterocycles (90 % of pyridines) at 100 g/L. Conversely, most volatile fatty acids remained in HTL aqueous. Subsequently, mesophilic and thermophilic specific methane potential increased by up to 97 % and 83 %, respectively. BOD increased by up to 50 %, which enhanced BOD/COD ratio from 81 % to 93 % before and after adsorption. This study established the groundwork for HTL aqueous adsorption, described mechanism for pollutant removal, and provided insights for biological treatment.

Anaerobic treatment of fruit and vegetable wastewater using EGSB: From strategies for regulating over-acidification to microbial community

Fruit and vegetable waste (FVW) are characterized by high-water content. Solid-liquid separation of FVW by crushing-extrusion physical pre-treatment provides fruit and vegetable wastewater (FVWW), and then for anaerobic biological treatment to recover methane, which is considered a cost-effective approach. However, anaerobic treatment of FVWW faces difficulties with low methane productivity and over-accumulation of volatile fatty acids (VFAs). In this study, the expanded granular sludge bed (EGSB) reactor was used for the anaerobic treatment of FVWW and the regulatory strategy to alleviate over-acidification was proposed. When the influent chemical oxygen demand (COD) concentration was 10000 mg/L, the hydraulic retention time (HRT) was 2 days, the organic loading rate (OLR) reached 5 g COD/L/d, the maximum methane productivity reached 301.14 ± 2.32 mL/g COD with a COD removal rate of 96 % ± 2 %. Lower VFAs accumulation was observed when decreasing the influent COD concentration to the same OLR compared with extending HRT, resulting in 38.5 % higher methane productivity. Decreasing the influent COD concentration not only benefited the enrichment of acetogens and hydrogenotrophic methanogens but also specifically enriched syntrophic bacteria. The enhanced syntrophic acetogenesis and hydrogenotrophic methanogens maybe the main reasons for promoting the degradation of propionate and butyrate and improving the methane productivity.

Recent Advanced Biological Wastewater Treatment Technologies

Conventional wastewater treatment approaches such as activated sludge processes often rely on energy-intensive and resource-demanding processes. However, emerging technologies offer promising solutions to improve the sustainability of wastewater management. This review examines three innovative technologies, including anaerobic membrane bioreactor (AnMBR), partial nitritation/anammox (PN/A), and microalgae-based processes, and their potential advantages over traditional methods. AnMBR combine membrane filtration with anaerobic biological treatment, enabling high-quality effluent, reduced sludge production, and a compact footprint. The PN/A is a two-step biological process that can achieve efficient nitrogen removal with lower aeration requirements. Microalgae-based systems leverage photosynthetic organisms to remove nutrients and organic matter while generating biomass for potential resource recovery. Each alternative technology has strengths and limitations that must be carefully evaluated based on the site-specific factors, such as wastewater characteristics, treatment objectives, and local conditions. Continued research and technological development is necessary to address the remaining technical and economic barriers impeding their wider adoption. Integrating multiple alternative technologies in a treatment train can help optimize overall performance by leveraging the complementary advantages of different processes. This holistic approach can advance the sustainable wastewater management, promoting resource efficiency, energy savings, and environmental protection.

Effect and mechanism of Mn2+ on urease activity during anaerobic biological treatment of landfill leachate.

As a crucial hydrolytic enzyme, urease plays a vital role in anaerobic biological treatment. It is well-known that manganese ions are abundant in landfill leachate, but their concentration fluctuates significantly. However, few studies have investigated the effect and mechanism of different concentrations of Mn2+ on urease activity during anaerobic biological treatment of landfill leachate. This paper aimed to investigate the effects and mechanisms of different concentrations of Mn2+ on urease activity. The results showed that an appropriate amount of Mn2+ could significantly enhance urease activity, while a high concentration of Mn2+ could inhibit it. Insight into the mechanisms behind this phenomenon, various methods such as Zeta potential, particle size, ultraviolet spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, and statistical analysis were employed in our study. Research suggested that, on one hand, Mn2+ may form hydrogen bonds with the side chain amino or carboxyl groups of urease amino acid residues, affecting the structure of urease through hydrogen bonding. Additionally, Mn2+ also binds to urease through hydrophobic interactions. On the other hand, the C-OH and C-N functional groups in urease have a strong affinity for Mn2+, and changes in these functional groups can greatly enhance the activity of urease. Furthermore, under the action of high concentrations of Mn2+, while the structure of urease becomes more stable, there is also a steric hindrance phenomenon that affects the substrate from entering the catalytic center. Therefore, studying the mechanism of Mn2+ affecting urease activity has significant biological significance and provides a new perspective for exploring the impact of metals on anaerobic bioprocessing of landfill leachate.

Assessment of molecularly imprinted polymers for selective removal of diclofenac from wastewater by laboratory and pilot-scale adsorption tests

This study investigated the potential of Molecularly Imprinted Polymers (MIPs) to integrate schemes for wastewater reuse and to serve as effective adsorbent for the removal of a target emerging contaminant (i.e., diclofenac – DCF), after or within pilot scale anaerobic biological treatments. Batch tests were performed to evaluate the effect on DCF removal during anaerobic biological processes by enriching activated sludge of an Upflow Anaerobic Sludge Blanket (UASB) reactor (TSS =19.6 g/L), and an Anaerobic Membrane Bioreactor (AnMBR) (TSS = 120 mg/L) reactors with MIPs (3 mg/L). Therefore, tertiary treatments were investigated by columns adsorption tests that were performed first at lab scale using DCF (15 mg/L) solution in deionized water, and then in-site by treating the anaerobic permeate effluent from the AnMBR at pilot scale level (DCF 500 μg/L). Clogging or blockage of the column bed was not observed during these field tests, where the saturation process of MIPs was slower compared to laboratory tests that used deionized water. In addition, the empirical Thomas Model, Yoon-Nelson Model, Dose-Response Model and Adam Bohart Model showed very good fittings with the experimental data obtained during experiments performed with both synthetic water and anaerobic effluents showing their suitability for the description of breakthrough curves. Finally, it was observed that after regeneration the MIPs can be efficiently reused since adsorption capacity is sufficiently preserved.

Effects of nitrate reduction on the biotransformation of 1H-1,2,4-triazole: Mechanism and community evolution

Due to the refractory of 1 H-1,2,4-triazole (TZ), conventional anaerobic biological treatment technology is usually restricted by low removal efficiency and poor system stability. In this study, TZ biodegradation and nitrate reduction was coupled to improve the removal efficiency of TZ from polluted wastewater. Batch assay was performed with pure culture strain Raoultella sp. NJUST42, which was reported to have the capability to degrade TZ in our previous study. Based on batch assay result, complete removal of TZ could be achieved in the presence of nitrate, whereas only 50% of TZ could be removed in the control system. Long-term stability experiment indicated that the relative abundance of microorganisms (Bacteroidetes_vadinHA17, Georgenia, Anaerolinea, etc) was obviously enhanced under nitrate reduction condition. During long-term period, major intermediates for TZ biodegradation such as [1,2,4]Triazolidine-3,5-diol, hydrazine dibasic carboxylic acid and carbamic acid were detected. A novel TZ biotransformation approach via hydration, TZ-ring cleavage, deamination and oxidation was speculated. PICRUSt1 and KEGG pathway analyses indicated that hydration (dch), oxidation (adhD, oah, pucG, fdhA) of TZ and nitrate reduction (Nar, napA, nrfA, nirBK, norB, nosZ) were significantly enhanced in the presence of nitrate. Moreover, the significant enrichment of TCA cycle (gab, sdh, fum, etc.) indicated that carbon and energy metabolism were facilitated with the addition of nitrate, thus improved TZ catabolism. The proposed mechanism demonstrated that TZ biodegradation coupled with nitrate reduction would be a promising approach for efficient treatment of wastewater contaminated by TZ.

Removal of RNA viruses from swine wastewater using anaerobic membrane bioreactor: Performance and mechanisms

The effective removal of viruses from swine wastewater using anaerobic membrane bioreactor (AnMBR) is vital to ecological safety. However, most studies have focused only on disinfectants, whereas the capabilities of the treatment process have not been investigated. In this study, the performance and mechanism of an AnMBR in the removal of porcine hepatitis E virus (HEV), porcine kobuvirus (PKoV), porcine epidemic diarrhea virus (PEDV), and transmissible gastroenteritis coronavirus (TGEV) are systematically investigated. The results show that the AnMBR effectively removes the four viruses, with average removal efficiencies of 1.62, 3.05, 2.41, and 1.34 log for HEV, PKoV, PEDV and TGEV, respectively. Biomass adsorption contributes primarily to the total virus removal in the initial stage of reactor operation, with contributions to HEV and PKoV removal exceeding 71.7 % and 68.2 %, respectively. When the membrane is fouled, membrane rejection dominated virus removal. The membrane rejection contribution test shows the significant contribution of membrane pore foulants (23–76 %). Correlation analysis shows that the surface characteristics and size differences of the four viruses contribute primarily to their different effects on biomass adsorption and membrane rejection. This study provides technical guidance for viral removal during the treatment of high-concentration swine wastewater using an AnMBR.

Coupling of biogas residue biochar and low-magnitude electric fields promotes anaerobic co-digestion of sewage sludge and food waste.

Biochar-assisted anaerobic digestion (AD) remains constrained due to the inefficient decomposition of complex organics, even with the direct interspecies electron transfer (DIET) pathway. The coupling of electrochemistry with the anaerobic biological treatment could shorten lengthy retention time in co-digestion by improving electron transfer rates and inducing functional microbial acclimation. Thus, this work investigated the potential of improving the performance of AD by coupling low-magnitude electric fields with biochar derived from the anaerobically digested biogas residue. Different voltages (0.3, 0.6, and 0.9 V) were applied at various stages to assess the impact on biochar-assisted AD. The results indicate that an external voltage of 0.3 V, coupled with 5 g/L of biochar, elevates CH4 yield by 45.5% compared to biogas residue biochar alone, and the coupled approach increased biogas production by up to 143% within 10 days. This finding may be partly explained by the enhanced utilization of substrates and the increased amounts of specific methanogens such as Methanobacterium and Methanosarcina. The abundance of the former increased from 4.0 to 11.3%, which enhances the DIET between microorganisms. Furthermore, the coupling method shows better potential for enhancing AD compared to preparing iron-based biochar, and these results present potential avenues for its broader applications.

Treatment of aqueous phase from hydrothermal liquefaction of municipal sludge by adsorption: Comparison of biochar, hydrochar, and granular activated carbon

Hydrothermal liquefaction (HTL) is promising for treating waste with high moisture, such as municipal sludge, and producing biocrude (a petroleum-like biofuel). However, a large amount of wastewater byproduct, HTL aqueous, is generated. The presence of hazardous compounds (e.g., phenolic compounds and nitrogenous organics) makes HTL aqueous the biggest bottleneck for full-scale implementation at treatment plants. This study investigated the adsorption of various pollutants, focusing on chemical oxygen demand (COD), in HTL aqueous to granular activated carbon (GAC), biochar, and hydrochar. It assessed the effect of pH, temperature, time, and adsorbent concentration on adsorption efficiency and identified proper adsorbent and process conditions for removing most of the pollutants from HTL aqueous. GAC showed the highest adsorption capacity (184 mg/g) for COD, surpassing biochar (44 mg/g) and hydrochar (42 mg/g). The adsorption of COD to all adsorbents followed pseudo-second-order kinetic and Freundlich isotherm, suggesting that the adsorption of HTL aqueous pollutants is a heterogeneous and multilayer process, limited by chemosorption. The adsorption was endothermic, favored by elevated temperatures and neutral pH. This means adsorption is more efficient and economical for treating HTL aqueous that is a hot stream at the large-scale and it saves chemical needs. Lastly, GAC was highly efficient and selective in removing harmful pollutants, such as COD (up to 66%), total phenolic compounds (up to 94%), pyrazines (up to 99%), pyridines (up to 100%), and cyclic ketones (up to 95%) while preserving valuable volatile fatty acids (VFAs) and ammonia for subsequent recovery. Removal of potentially inhibitory compounds and preserving VFAs are crucial for carbon recovery in anaerobic biological treatment of HTL aqueous. The results suggested the necessity of optimizing adsorbent dose for maximizing removal of specific group of inhibitory compounds in full-strength HTL aqueous for enhancing downstream biological treatment. Lastly, this study established the groundwork for HTL aqueous adsorption, elucidating its effectiveness and mechanism for pollutant removal.

Research on the Application and Mechanisms of Electroactive Microorganisms in Toxicants Monitoring: A Review.

A biological treatment is the core process for removing organic pollutants from industrial wastewater. However, industrial wastewater often contains large amounts of toxic and harmful pollutants, which can inhibit the activity of microorganisms in a treatment system, precipitate the deterioration of effluent quality, and threaten water ecological security from time to time. In most of the existing anaerobic biological treatment processes, toxic effects on microorganisms are determined according to the amounts of end-products of the biochemical reactions, and the evaluation results are relatively lacking. When microorganisms contact toxic substances, changes in biological metabolic activity precede the accumulation of reaction products. As sensitive units, electroactive microorganisms can generate electrical signals, a change in which can directly reflect the toxicity level. The applications of electroactive microorganisms for the toxicity monitoring of wastewater are very promising. Further attention needs to be paid to considering the appropriate evaluation index, the influence of the environment on test results, mechanisms, and other aspects. Therefore, we reviewed the literature regarding the above aspects in order to provide a research foundation for the practical application of electroactive microorganisms in toxicant monitoring.

Oxidation of sulfides following anaerobic municipal wastewater treatment for non-potable reuse applications

Anaerobic secondary biological wastewater treatment could increase energy efficiency by avoiding energy-intensive aeration while producing methane that could be harvested for energy production.

Revealing the roles of biochar derived from iron-rich fermented sludge residue in anaerobic digestion

Anaerobic biological treatment of waste activated sludge (WAS) is proven as a low-carbon footprint technology with dual advantages of bio-fuel recovery and sludge stabilization. However, sludge residue after anaerobic biological treatment has been a serious obstacle to build waste-free cities. In this study, sludge residue, iron-rich sludge residue, and iron-rich fermented sludge residue were selected as the raw materials of biochar and the roles of prepared biochar in anaerobic digestion of WAS were investigated. Results indicated that the prepared biochar improved methane production and biochar derived from iron-rich fermented sludge residue (PFF-BC) obtained the best performance, with an increment of 23.4%. Mechanism analysis illustrated that the structural characteristics of PFF-BC were updated, including iron species, defect levels, and specific surface area, which played positive roles in the conversion of intermediate metabolites. Meanwhile, the compositions and electro-activity properties of extracellular polymeric substances were both stimulated by PFF-BC. Correspondingly, the activities of electron transport system and cytochrome c increased by 23.4% and 36.7%, respectively. For microbial communities, the abundances of electroactive microorganisms (such as Anaerolineaceae, Syntrophomonas and Methanosaeta) increased and direct interspecies electron transfer might be established, improving CO2-reduction and acetoclastic methanogenesis pathways. These findings will provide important references for stepwise resource recovery and final disposal of WAS.

Long-term presence of microplastics in aerobic and anaerobic sequential batch reactors: Effect on treatment, microbial diversity, and microplastics morphology

Sewage treatment plants (STPs) are identified as the significant sink and source of microplastics (MPs) in aquatic bodies and terrestrial systems. A major fraction of MPs gets retained in STPs for a longer duration, and their potentiality for secondary MPs generation and additives leaching remain under investigated. Therefore, this study focussed on the effect of long-term exposure of aerobic and anaerobic biological sewage treatment units on MPs, along with the effect of MPs on treatment efficiency and microbial consortium. A mixture of polyvinyl chloride, polystyrene, and nylon MPs at 262 MPs/L was spiked in the aerobic and anaerobic sequential batch reactors (SBRs) for 120 days at the start of study. The study revealed a release of noteworthy fraction of secondary MPs into the reactors from spiked MPs. At the end of 120th day, the presence of secondary generated MPs was estimated as 1000 ± 71 MPs/L and 650±141 MPs/L in aerobic and anaerobic SBRs respectively. Most of the observed secondary MPs were of size < 300 µm. Leaching of additives, i.e. cyclohexylamine, cyclotetradecane, octadecanol, pipericine etc., into the SBR effluents were also observed. The depuration capacities of the reactors were not affected with the presence of MPs during the study. While the microbial diversity and abundance were negatively impacted in aerobic SBRs, no such impacts were observed in anaerobic SBRs due to MPs. These results do suggest such exposures to potentially cause secondary MPs and chemical pollution in receiving matrices for the treated effluent, as well as effect on the native microbial community.

Production of C2+ products in novel microbial electrosynthesis coupled with anaerobic membrane bioreactor

Aim to realize in-situ CO2 reduction to multi-carbon (C2+) products in anaerobic biological treatment systems, a microbial electrosynthesis coupled with anaerobic membrane bioreactor (MES-AnMBR) was constructed with the carbon nanotubes based hollow fiber membranes as the separation unit and the biological cathode, simultaneously. Acetic acid and ethanol as the main C2+ products with the highest concentration of 230 mg/L and 7.05 mg/L were obtained in MES-AnMBR, respectively. The genes related to acetic acid and ethanol production were remarkably up-regulated, such as pta, ACSS1_2(acs), ALDH, yiaY, frmA, adhE and yahK with the respective relative abundance of 0.49‰, 0.75‰, 0.62‰, 0.173‰, 0.19‰, 0.30‰ and 0.07‰. Cloacibacterium and Geobacter as types of electrochemically active bacteria could involve in the electron transfer. Macellibacteroides with the abundance of 16.7% became the main bacteria for acetic acid, butyrate and iso-butyrate even ethanol production. Moreover, MES-AnMBR owned a stable and good effluent quality with the average effluent COD of 22.56 mg/L (average removal rate of 95.4%). The effluent COD was 0 mg/L for many times during the operation. Benefiting from the electrochemical effect, the main membrane fouling types occurred on the membranes was reversible membrane fouling, which accounted for 52.2% and easily recovered by hydraulic cleaning.

Study on the degradability of plastics with prodegradant additives during anaerobic and aerobic biological waste treatment processes

The degradability of conventional plastic packaging specimens made from PP and PET, that were produced with novel prodegradant additives, was investigated during biological waste treatment processes. The additives were merchandised to foster the degradation of commodity plastics by enzymatic or by abiotic processes. Four different plastic packaging specimens and two different additives were evaluated for their biodegradability during anaerobic and aerobic waste treatment conditions. Aerobic treatment was investigated in laboratory rotting tests, simulating conditions during composting in a plant according to the Austrian state-of-the-art, while anaerobic treatment was investigated in laboratory digestion reactors. The study shows that only the PET specimens showed a loss of mass of ca. 6.5%, during 50 days of digestion at 52 °C. None of the specimens degraded during the aerobic rotting process. None of the materials fragmented into microplastic particles of sizes > 1 mm under the investigated conditions. However, FTIR analysis revealed the oxidation in the case of PP specimens, which indicated a mediated oxidation process during composting, independent of the merchandised mechanism of predegradation. Under anaerobic conditions, the plastic specimens containing reactors produced more biogas within the first 20 days of digestion, that did not originate from an observable degradation of the plastics.