Performance of a three-stage membrane bioprocess treating the organic fraction of municipal solid waste and evolution of its archaeal and bacterial ecology

Enhanced printing and dyeing wastewater treatment using anaerobic-aerobic systems with bioaugmentation

Printing and dyeing wastewater (PDW) is characterized by various pollutants, making it one of the most difficult industrial wastewaters to treat and poses a serious threat to the natural environment and public health. This study investigated the use of an anaerobic-aerobic system combined with bioaugmentation using Ochrobactrum anthropi S1 to treat PDW. The results indicated that after three rounds of inoculation, Ochrobactrum anthropi S1 successfully colonized the system, achieving final removal efficiencies of reactive black 5, Cr(Ⅵ), COD, and ammonia nitrogen of 95 %, 65 %, 90 %, and 85 %, respectively. Microbial community analysis further revealed differences in community dynamics between the anaerobic and aerobic phases. During the anaerobic phase, microbial community assembly was primarily shaped by stochastic processes (60 %), whereas the aerobic phase was governed by deterministic processes (65 %). Additionally, co-occurrence network analysis suggested that microorganisms in the aerobic phase may form more complex interactions compared to the anaerobic phase, thereby enhancing pollutant removal efficiency. This study confirms that bioaugmentation with Ochrobactrum anthropi S1, combined with anaerobic-aerobic technology, is an effective strategy for treating PDW, enhancing both system stability and microbial performance.

A review on anaerobic membrane bioreactors for enhanced valorization of urban organic wastes: Achievements, limitations, energy balance and future perspectives

Sustainable urban development is threatened by an impending energy crisis and large amounts of organic wastes generated from the municipal sector among others. Conventional waste management methods involve greenhouse gas (GHG) emission and limited resource recovery, thus necessitating advanced techniques to convert such wastes into bioenergy, bio-fertilizers and valuable-added products. Research and application experiences from different scale applications indicate that the anaerobic membrane bioreactor (AnMBR) process is a kind of high-rate anaerobic digester for urban organic wastes valorization including food waste and waste sludge, while the research status is still insufficiently summarized. Through compiling recent achievements and literature, this review will focus on the following aspects, including AnMBR treatment performance and membrane fouling, technical limitations, energy balance and techno-economic assessment as well as future perspectives. AnMBR can enhance organic wastes treatment via complete retention of functional microbes and suspended solids, and timely separation of products and potential inhibitory substances, thus improving digestion efficiency in terms of increased organics degradation rates, biogas production and process robustness at a low footprint. When handling high-solid organic wastes, membrane fouling and mass transfer issues can be the challenges limiting AnMBR applications to a wet-type digestion, thus countermeasures are required to pursue extended implementations. A conceptual framework is proposed by taking various organic wastes disposal and final productions (permeate, biogas and biosolids) utilization into consideration, which will contribute to the development of AnMBR-based waste-to-resource facilities towards sustainable waste management and more economic-environmental benefits output.

Strategies for recovery of imbalanced full-scale biogas reactor feeding with palm oil mill effluent

Background

Full-scale biogas production from palm oil mill effluent (POME) was inhibited by low pH and highly volatile fatty acid (VFA) accumulation. Three strategies were investigated for recovering the anaerobic digestion (AD) imbalance on biogas production, namely the dilution method (tap water vs. biogas effluent), pH adjustment method (NaOH, NaHCO₃, Ca(OH)₂, oil palm ash), and bioaugmentation (active methane-producing sludge) method. The highly economical and feasible method was selected and validated in a full-scale application.

Results

The inhibited sludge from a full-scale biogas reactor could be recovered within 30–36 days by employing various strategies. Dilution of the inhibited sludge with biogas effluent at a ratio of 8:2, pH adjustment with 0.14% w/v NaOH, and 8.0% w/v oil palm ash were considered to be more economically feasible than other strategies tested (dilution with tap water, or pH adjustment with 0.50% w/v Ca(OH)₂, or 1.25% NaHCO₃ and bioaugmentation) with a recovery time of 30–36 days. The recovered biogas reactor exhibited a 35–83% higher methane yield than self-recovery, with a significantly increased hydrolysis constant (k_H) and specific methanogenic activity (SMA). The population of Clostridium sp., Bacillus sp., and Methanosarcina sp. increased in the recovered sludge. The imbalanced full-scale hybrid cover lagoon reactor was recovered within 15 days by dilution with biogas effluent at a ratio of 8:2 and a better result than the lab-scale test (36 days).

Conclusion

Dilution of the inhibited sludge with biogas effluent could recover the imbalance of the full-scale POME-biogas reactor with economically feasible and high biogas production performance.

Bacterial communities on soil microplastic at Guiyu, an E-Waste dismantling zone of China

Recent studies of microplastic have focused on aquatic environment, but its impacts on soil ecosystems were poorly understood, particularly on bacterial communities. In this study, the bacterial taxon and functional composition of soil microplastic-attached communities at Guiyu, a notorious e-waste dismantling area in Guangdong Province, China, were investigated by means of high-throughput sequencing. The results revealed that fundamental difference in bacterial communities existed among microplastics selected from three plots with different dismantling methods and their surroundings, suggesting that microplastic surface created a new ecological niche in soil environment, and the bacteria adapted well to the surface-related lifestyle. The formation of microplastic-attached bacteria depended not only on various dismantled plastic materials, but also on disassembly methods that caused different soil physicochemical characters which might also influence the bacterial communities. As the hydrocarbon degraders, the family Hyphomonadaceae were also found on soil microplastic, further confirming that microorganisms played a role in biodegrading microplastic in e-waste zone. The analysis of functional profiles speculated that microplastic-attached bacteria had the potential to degrade pollutants. This study provides a new perspective for exploring microplastic-associated bacteria and increasing our understanding of microplastic pollution in terrestrial ecosystems.

Dynamics and response of microbial diversity to nutritional conditions in denitrifying bioreactor for linear alkylbenzene sulfonate removal

The aim of this study was to evaluate the microbial structure and phylogenetic diversity under the influence of nutritional conditions and hydraulic retention time (HRT) in fluidized bed reactors (FBR), operated in short HRT (8 h - FBR8; 12 h - FBR12) for linear alkylbenzene sulfonate (LAS) removal from laundry wastewater. After each phase, biofilm samples from FBR8 and FBR12 were submitted to microbial sequencing by Mi-Seq Illumina®. Higher LAS removal rates were observed after 313 days, achieving 99 ± 3% in FBR12 (22.5 ± 5.9 mg LAS/L affluent) and 93 ± 12% in FBR8 (20.6 ± 4.4 mg LAS/L affluent). Different modifications involving genera of bacteria were observed throughout the reactors operation. The identified microorganisms were, mostly, related to LAS degradation and nitrogen conversion such as Dechloromonas, Flavobacterium, Pseudomonas, and Zoogloea.

Full-scale anaerobic reactor samples would be more suitable than lab-scale anaerobic reactor and natural samples to inoculate the wheat straw batch anaerobic digesters

This study evaluated the effects of the inocula from natural wetland, lab-scale and full-scale anaerobic reactors on wheat straw anaerobic digestion. Three replicate batch reactors were constructed for each inoculum to investigate the reactor performances and microbial communities. Reactors seeded with full-scale reactor samples were started up most rapidly, achieved the highest methane production, and were recognized as the higher efficient reactors. The dominance of acetoclastic methanogens, including Methanosaeta and Methanoscrina, was crucial for the higher efficient reactors, whereas hydrogenotrophic methanogens were dominant in other reactors. Genus Treponema, which could enhance the cellulose degradation and conduct homoacetogenesis, was first reported to be dominant in the bacterial communities of high efficient reactors. Inoculum sources and process conditions were suggested to be the deterministic factors in shaping the microbial communities in the higher efficient reactors. These findings contribute to the startup of new anaerobic reactors.

Monitoring of Air Microbial Contaminations in Different Bioenergy Facilities Using Cultural and Biomolecular Methods

Bioaerosol exposure linked to the bioenergy production from waste and its effects on human health in occupational and residential environments has rising interest nowadays. The health risk associated with the exposure includes mainly infective diseases, allergies, chronic bronchitis, and obstructive pulmonary disease. A risk assessment's critical point is the bioaerosol quality and quantity characterization. The aim of this study is to evaluate the application of different methods for the analysis of bioaerosol sampled in bioenergy plants. This study involved six Italian plants for the treatment of biomasses and energy production. Bioaerosol cultural evaluation was performed, by Surface Air System (SAS) sampler, and DNA was extracted from PM0.49 samples and Low Melting Agar plates. qRT-PCR followed by Denaturing Gradient Gel Electrophoresis (DGGE) and band sequencings were performed. The cultural method is able to detect less than 15% of what is evaluable with bio-molecular methods. A low sample alfa-diversity and a high beta-biodiversity in relation to feedstock and process were observed. Sequencing showed microorganisms with a hygienic-sanitary relevance such as Arcobacter, Pseudomonas, Enterobacter, Klebsiella, Enterococcus and Bacillus. Integrated cultural and biomolecular methods can be more exhaustive to evaluate bioaerosol's exposure in the occupational environment.

Responses of ammonia-oxidizing bacteria community composition to temporal changes in physicochemical parameters during food waste composting

This paper aimed to identify and prioritize some environmental parameters that affect AOB community composition during food waste composting.

Prokaryote community dynamics in anaerobic co-digestion of swine manure, rice straw and industrial clay residuals

The aim of this study was to analyze the effect of the addition of rice straw and clay residuals on the prokaryote methane-producing community structure in a semi-continuously stirred tank reactor fed with swine manure. Molecular techniques, including terminal restriction fragment length polymorphism and a comparative nucleotide sequence analyses of the prokaryotic 16S rRNA genes, were performed. The results showed a positive effect of clay addition on methane yield during the co-digestion of swine manure and rice straw. At the digestion of swine manure, the bacterial phylum Firmicutes and the archaeal family Methanosarcinaceae, particularly Methanosarcina species, were predominant. During the co-digestion of swine manure and rice straw the microbial community changed, and with the addition of clay residual, the phylum Bacteroidetes predominated. The new nutritional conditions resulted in a shift in the archaeal family Methanosarcinaceae community as acetoclastic Methanosaeta species became dominant.

Microbial ecology overview during anaerobic codigestion of dairy wastewater and cattle manure and use in agriculture of obtained bio-fertilisers

The anaerobic co-digestion of dairy wastewater (DW) and cattle manure (CM) was examined and associated with microbial community's structures using Denaturing Gradient Gel Electrophoresis (DGGE). The highest volatile solids (VS) reduction yield of 88.6% and biogas production of 0.87 L/g VS removed were obtained for the C/N ratio of 24.7 at hydraulic retention time (HRT) of 20 days. The bacterial DGGE profile showed significant abundance of Uncultured Bacteroidetes, Firmicutes and Synergistetes bacterium. The Syntrophomonas strains were discovered in dependent association to H2-using bacteria such as Methanospirillum sp., Methanosphaera sp. and Methanobacterium formicicum. These syntrophic associations are essential in anaerobic digesters allow them to keep low hydrogen partial pressure. However, high concentrations of VFA produced from dairy wastes acidification allow the growth of Methanosarcina species. The application of the stabilised anaerobic effluent on the agriculture soil showed significant beneficial effects on the forage corn and tomato plants growth and crops.

Biomethane production and dynamics of microflora in response to copper treatments during mesophilic anaerobic digestion

This study discussed the effects of different concentrations (0.625, 1.875 and 3.125 mM) of copper (Cu) in the form of CuSO4 on biomethane production and on the dynamics of microbial communities during the mesophilic anaerobic digestion (AD) of cow manure. The effects on biomethane production were found to depend on CuSO4 concentrations. After 50 days of AD, treatment A3 (3.125 mM) had lower cumulative biomethane production than the no-Cu control. The maximum value of cumulative biomethane production was detected under treatment A2 (1.875 mM). These results suggested that the stimulation or inhibition to biomethane production might be related to the concentration and chemical forms of Cu. Moreover, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) was used to discuss the dynamics of microbial communities. Results revealed that different concentrations of CuSO4 had effects on the richness and diversity of bacterial and archaeal communities. The predominance of Bacteroidetes bacterium (GU339485.1) was verified through the sequencing of the dominant DGGE bands. Furthermore, Bacteroidetes bacterium could be detected during the whole AD process and is adaptable to a certain concentration range of CuSO4.

Effects of different SRT on anaerobic digestion of MSW dosed with various MSWI ashes

This study investigated different solid retention time (SRT) on municipal solid waste (MSW) anaerobic digestion with various MSW incinerator fly ash (FA) and bottom ash (BA) addition. Results showed that biogas production rates (BPRs, ≈ 200 to ≈ 400 mL/gVS) with organic loading rate of ≈ 0.053 gVS/gVS(reactor) (Day 1-435, SRT 20 days, SRT20) at FA 1g/d (FA1), BA 12 g/d (BA12) and BA 24 g/d (BA24) dosed bioreactors increased after adaptation. BPRs with SRT10 and SRT5 decreased while BPRs with SRT40 showed to increase compared to initial BPRs (≈ 200 mL/gVS) with SRT20. SRT5 operation reduced the BPRs (≈ 10 - ≈ 90 mL/gVS) significantly and only BA12 and BA24 dosed bioreactors could recover the BPRs (≈ 100 - ≈ 200 mL/gVS) after SRT20 operation (Day 613-617) compared to FA1 and FA3 and control. Released levels of Co, Mo and W at BA12 and BA24 dosed bioreactors showed most potential to improve MSW anaerobic digestion.

Using fluorescence excitation-emission matrix spectroscopy to monitor the conversion of organic matter during anaerobic co-digestion of cattle dung and duck manure

In this study, the removal of volatile solids (VSs) and soluble chemical oxygen demand (SCOD) by co-digesting cattle dung (CD) and duck manure (DM) was determined and compared with the reduction achieved with CD or DM digestion alone. Moreover, fluorescence excitation-emission matrix spectroscopy was utilised to characterise the conversion mechanisms of organic nitrogen. It was found that the co-digestion provided 71% VS reduction compared with 58% for CD and 61% for DM. The amounts of COD removed were 28%, 23% and 31% for CD, DM and the mixture, respectively. Tyrosine-like/fulvic-like fluorescence intensity (FI) ratios increased during the initial 15days of co-digestion and were associated with an increase in total nitrogen in the supernatant. After 15days, CD and DM exhibited a lower tryptophan-like/fulvic-like FI ratio (0.8-1.6), whereas the co-digestion remained stable at a high level (3.0-3.6), rendering an improved microbial population and biochemical activity.

Recent developments in anaerobic membrane reactors

Anaerobic membrane reactors (AnMBRs) have recently evolved from aerobic MBRs, with the membrane either external or submerged within the reactor, and can achieve high COD removals (~98%) at hydraulic retention times (HRTs) as low as 3 h. Since membranes stop biomass being washed out, they can enhance performance with inhibitory substrates, at psychrophilic/thermophilic temperatures, and enable nitrogen removal via Anammox. Fouling is important, but addition of activated carbon or resins/precipitants can remove soluble microbial products (SMPs)/colloids and enhance flux. Due to their low energy use and solids production, and solids free effluent, they can enhance nutrient and water recycling. Nevertheless, more work is needed to: compare fouling between aerobic and anaerobic systems; determine how reactor operation influences fouling; evaluate the effect of different additives on membrane fouling; determine whether nitrogen removal can be incorporated into AnMBRs; recover methane solubility from low temperatures effluents; and, establish sound mass and energy balances.

Microbial communities and their performances in anaerobic hybrid sludge bed-fixed film reactor for treatment of palm oil mill effluent under various organic pollutant concentrations

The anaerobic hybrid reactor consisting of sludge and packed zones was operated with organic pollutant loading rates from 6.2 to 8.2 g COD/L day, composed mainly of suspended solids (SS) and oil and grease (O&G) concentrations between 5.2 to 10.2 and 0.9 to 1.9 g/L, respectively. The overall process performance in terms of chemical oxygen demands (COD), SS, and O&G removals was 73, 63, and 56%, respectively. When the organic pollutant concentrations were increased, the resultant methane potentials were higher, and the methane yield increased to 0.30 L CH₄/g COD_removed. It was observed these effects on the microbial population and activity in the sludge and packed zones. The eubacterial population and activity in the sludge zone increased to 6.4 × 10⁹ copies rDNA/g VSS and 1.65 g COD/g VSS day, respectively, whereas those in the packed zone were lower. The predominant hydrolytic and fermentative bacteria were Pseudomonas, Clostridium, and Bacteroidetes. In addition, the archaeal population and activity in the packed zone were increased from to 9.1 × 10⁷ copies rDNA/g VSS and 0.34 g COD-CH₄/g VSS day, respectively, whereas those in the sludge zone were not much changed. The most represented species of methanogens were the acetoclastic Methanosaeta, the hydrogenotrophic Methanobacterium sp., and the hydrogenotrophic Methanomicrobiaceae.

Influence of step increases in hydraulic retention time on (RS)-MCPP degradation using an anaerobic membrane bioreactor

The effects of different hydraulic retention time (HRT) on (RS)-MCPP utilisation was investigated by decreasing the feed flow rate in an anaerobic membrane bioreactor (AnMBR). Results showed an average COD removal efficiency of 91.4%, 96.9% and 94.4% when the reactor was operated at HRT 3, 7 and 17 d, respectively. However, when the HRT was reduced to 1d, the COD removal efficiency declined to just only 60%, confirming the AnMBR is stable to a large transient hydraulic shock loads. The (RS)-MCPP removal efficiency fluctuated from 6% to 39% at HRT 3 d, however when it was increased to 7 and 17 d, the removal efficiency increased to an average of 60% and 74.5%. In addition, (RS)-MCPP specific utilisation rates (SUR) were dependent on the HRT and gradually improved from 18 to 43 μg mg VSS(-1) d(-1) as flow rate increased.

Changes in bacterial communities from anaerobic digesters during petroleum hydrocarbon degradation

Anaerobic biodegradation of petroleum hydrocarbons (PHC) to methane has been recognized to occur in oil reservoirs and contaminated surface sites alike. This process could be employed efficiently for the treatment of contaminated materials, including petrochemical wastes and PHC-contaminated soil, since no external electron acceptor is required. Moreover, the controlled production of methane in digestion plants, similarly to the anaerobic digestion (AD) of energy crops or organic residues, would enable for energy recovery from these wastes. At present, little is known about the bacterial communities involved in and responsible for hydrocarbon fermentation, the initial step in PHC conversion to methane. In the present study, the fate of two different methanogenic communities derived from the AD of wastewater (WWT) and of biowaste, mixed with PHC-contaminated soil (SWT), was monitored during incubation with PHC using denaturing gradient gel electrophoresis (DGGE) of 16S rDNA genes amplified with Bacteria-specific primers. During 11 months of incubation, slight but significant degradation of PHC occurred in both sludges and distinct bacterial communities were developing. In both sludges, Bacteroidetes were found. In addition, in WWT, the bacterial community was found to be dominated by Synergistetes and Proteobacteria, while Firmicutes and unidentified members were abundant in SWT. These results indicate that bacterial communities from anaerobic digesters can adapt to and degrade petroleum hydrocarbons. The decontamination of PHC-containing waste via fermentative treatment appears possible.

The anaerobic digestion of solid organic waste

The accumulation of solid organic waste is thought to be reaching critical levels in almost all regions of the world. These organic wastes require to be managed in a sustainable way to avoid depletion of natural resources, minimize risk to human health, reduce environmental burdens and maintain an overall balance in the ecosystem. A number of methods are currently applied to the treatment and management of solid organic waste. This review focuses on the process of anaerobic digestion which is considered to be one of the most viable options for recycling the organic fraction of solid waste. This manuscript provides a broad overview of the digestibility and energy production (biogas) yield of a range of substrates and the digester configurations that achieve these yields. The involvement of a diverse array of microorganisms and effects of co-substrates and environmental factors on the efficiency of the process has been comprehensively addressed. The recent literature indicates that anaerobic digestion could be an appealing option for converting raw solid organic wastes into useful products such as biogas and other energy-rich compounds, which may play a critical role in meeting the world's ever-increasing energy requirements in the future.

Parameters affecting the stability of the digestate from a two-stage anaerobic process treating the organic fraction of municipal solid waste

This paper focused on the factors affecting the respiration rate of the digestate taken from a continuous anaerobic two-stage process treating the organic fraction of municipal solid waste (OFMSW). The process involved a hydrolytic reactor (HR) that produced a leachate fed to a submerged anaerobic membrane bioreactor (SAMBR). It was found that a volatile solids (VS) removal in the range 40-75% and an operating temperature in the HR between 21 and 35 °C resulted in digestates with similar respiration rates, with all digestates requiring 17 days of aeration before satisfying the British Standard Institution stability threshold of 16 mg CO(2) g VS(-1) day(-1). Sanitization of the digestate at 65 °C for 7 days allowed a mature digestate to be obtained. At 4 g VS L(-1) d(-1) and Solid Retention Times (SRT) greater than 70 days, all the digestates emitted CO(2) at a rate lower than 25 mg CO(2) g VS(-1) d(-1) after 3 days of aeration, while at SRT lower than 20 days all the digestates displayed a respiration rate greater than 25 mg CO(2) g VS(-1) d(-1). The compliance criteria for Class I digestate set by the European Commission (EC) and British Standard Institution (BSI) could not be met because of nickel and chromium contamination, which was probably due to attrition of the stainless steel stirrer in the HR.

Linking microbial community structure to membrane biofouling associated with varying dissolved oxygen concentrations

In order to elucidate how dissolved oxygen (DO) concentration influenced the generation of extracellular polymeric substance (EPS) and soluble microbial products (SMP) in mixed liquor and biocake, 16S rDNA fingerprinting analyses were performed to investigate the variation of the microbial community in an aerobic membrane bioreactor (MBR). The function of microbial community structure was proved to be ultimately responsible for biofouling. Obvious microbial community succession from the subphylum of Betaproteobacteria to Deltaproteobacteria was observed in biocake. High concentration of EPS in biocake under the low DO concentration (0.5 mg L(-1)) caused severe biofouling. The correlation coefficient of membrane fouling rate with EPS content in biocake (0.9941-0.9964) was much higher than that in mixed liquor (0.6689-0.8004).

Microbial community dynamics in mesophilic anaerobic co-digestion of mixed waste

This paper identifies key components of the microbial community involved in the mesophilic anaerobic co-digestion (AD) of mixed waste at Rayong Biogas Plant, Thailand. The AD process is separated into three stages: front end treatment (FET); feed holding tank and the main anaerobic digester. The study examines how the microbial community structure was affected by the different stages and found that seeding the waste at the beginning of the process (FET) resulted in community stability. Also, co-digestion of mixed waste supported different bacterial and methanogenic pathways. Typically, acetoclastic methanogenesis was the major pathway catalysed by Methanosaeta but hydrogenotrophs were also supported. Finally, the three-stage AD process means that hydrolysis and acidogenesis is initiated prior to entering the main digester which helps improve the bioconversion efficiency. This paper demonstrates that both resource availability (different waste streams) and environmental factors are key drivers of microbial community dynamics in mesophilic, anaerobic co-digestion.