In this work, a one-stage dual internal circulation airlift anaerobic/anoxic/aerobic (DCAL-A2O) bioreactor was continuously operated for concurrent removal of nutrients and organics from milk ...processing wastewater (MPW). Special configuration of the airlift A2O bioreactor created possibility of the formation of desired anaerobic, anoxic and aerobic zones in a single unit. The process functionality of the bioreactor was examined under three influential operating variables i.e. hydraulic retention time (HRT; 7–15 h), air flow rate (AFR; 1–3 L/min) and aerobic volume ratio (AVR; 0.324–0.464). The optimum region was identified at HRT of 13h, AFR of 2L/min and AVR of 0.437, leading to TCOD, TN and TP removal efficiency of 94.5 %, 59.6 %, and 62.2 %, respectively, and effluent turbidity of 8 NTU. The impact of feed biodegradability on the process performance of the bioreactor treating the MPW, soft drink wastewater (SDW) and soybean oil plant wastewater (SOW) was also assessed. From the results, the feed characteristics affected significantly the nutrients removal. Moreover, the feeding location played an effective role in the nutrient removal while treating the MPW at optimum operating conditions. In this study, the change in residual organic matters as soluble microbial products (SMP) was monitored at various operating conditions. In addition, the impact of SMP extracted from sludge, extracellular polymeric substances (EPS) comprising of loosely bound EPS (LB-EPS) and tightly bound EPS (TB-EPS) was analyzed on sludge characteristics as bio-flocculation and settleability properties. According to the obtained data, the increase in operating variables led to the reduction in contents of effluent SMP, sludge SMP, LB-EPS, turbidity, and SVI, thereby, the enhancement in the sludge characteristics. Meanwhile, analysis of microbial communities verified the presence of various functional bacterial species. The cost operating evaluation confirmed the cost effectiveness of the airlift A2O bioreactor in reduction of energy consumption for the MPW treatment.
One-stage dual internal circulation airlift A2O bioreactor. Display omitted
•Simultaneous CNP removal was investigated in a one-stage DCAL-A2O bioreactor.•The impact of wastewater biodegradability and feeding location was evaluated on the bioreactor performance.•The sludge characteristics were explored throughout multiple experimental runs.•Operational cost estimates were performed under different operating conditions.•The coexistence and mutualistic development of various functional bacterial were observed in the context of PCR assays.
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•SSF emerged as a promising bioprocess for microbial secondary metabolites production.•Certain SMs are produced in SSF with impressive yield compared to SmF.•Novel bioreactor ...designing is major requisite for large scale application of SSF.•Scale-up, heat dissipation and mass transfer are major challenges of SSF processing.
Microbial secondary metabolites (SMs) are the intermediate or the product of metabolism produced during fermentation process. SMs are produced during stationary phase and play a major role in competition, antagonism and self defence mechanisms. These metabolites finds application in the pharmaceuticals, food, cosmetics etc. These are produced besides primary key metabolites (e.g., amino acids, lipids, carbohydrates etc.). Growth condition in solid-state fermentation (SSF) resembles microorganism’s own native environment allowing the microorganisms to adapt best. Recent developments in bioprocessing has identified specific SSF practices that have a significant impact on SMs production. The practice of SSF, representing new opportunities to design better bioprocessing with potential genetic development goals for expanding the list of exciting SMs. Current updates cover advanced techniques on SSF to improve microbial SMs production and their ease of operation and cost-effective production strategies. Various factors affecting the SSF have been discussed with respect to sustainable development of novel SSF strategies for SMs production.
► Anaerobic membrane bioreactors (AnMBRs) have been evaluated for domestic wastewater (DWW) treatment. ► Adequate DWW treatment in AnMBRs is achievable at low temperatures for long SRTs. ► Membrane ...fouling energy demands need to be reduced. ► Efficient permeate dissolved methane handling methods must be established. ► A quantitative environmental and economic evaluation framework is needed for AnMBRs.
Interest in increasing the sustainability of water management is leading to a reevaluation of domestic wastewater (DWW) treatment practices. A central goal is to reduce energy demands and environmental impacts while recovering resources. Anaerobic membrane bioreactors (AnMBRs) have the ability to produce a similar quality effluent to aerobic treatment, while generating useful energy and producing substantially less residuals. This review focuses on operational considerations that require further research to allow implementation of AnMBR DWW treatment. Specific topics include membrane fouling, the lower limits of hydraulic retention time and temperature allowing for adequate treatment, complications with methane recovery, and nutrient removal options. Based on the current literature, future research efforts should focus on increasing the likelihood of net energy recovery through advancements in fouling control and development of efficient methods for dissolved methane recovery. Furthermore, assessing the sustainability of AnMBR treatment requires establishment of a quantitative environmental and economic evaluation framework.
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•EMBR provides the possibility of removing specific pollutants from a wastewater.•Biomass and waste are kept separated for improving both streams optimization.•Membrane helps to ...protect microorganism from direct contact with toxic species.•More works are needed to develop highly selective and permeable membrane.•Biofilm thickness optimization and control need more exploration.
Combining bioreactor and membrane, known as a membrane bioreactor (MBR), has been considered as an attractive strategy to solve the limitations of conventional activated sludge process, such as biological instability, poor sludge quality, and low concentration of mixed liquor suspended solid. Unlike the other MBRs, extractive membrane bioreactor (EMBR) focuses on enhancing the efficiency of wastewater treatment through toxic compounds extraction by using a selective membrane. Even though EMBR has been successfully demonstrated in wastewater and waste gas treatment by several studies, it still faces some obstacles such as biofilm formation and low selectivity of the membrane towards a specific component. Appropriate biofilm formation control strategies and membrane with high selectivity are needed to solve those problems. This paper reviews EMBR including its potential applications in wastewater treatment, denitrification process, and waste gas treatment. In addition, challenges and outlook of EMBR are discussed.
Operation of membrane bioreactors (MBRs) for wastewater treatment is hampered by the membrane biofouling resulting from microbial activities. However, the knowledge of the microbial ecology of both ...biofilm and activated sludge in MBRs has not been sufficient. In this study, we scrutinized microbial communities of biofilm and activated sludge from 10 full-scale MBR plants. Overall, Flavobacterium, Dechloromonas and Nitrospira were abundant in order of abundance in biofilm, whereas Dechloromonas, Flavobacterium and Haliscomenobacter in activated sludge. Community structure was analyzed in either biofilm or activated sludge. Among MBRs, as expected, not only diversity of microbial community but also its composition was different from one another (p < 0.05). Between the biofilm and activated sludge, community composition made significant difference, but its diversity measures (i.e., alpha diversity, e.g., richness, diversity and evenness) did not (p > 0.05). Effects of ten environmental factors on community change were investigated using Spearman correlation. MLSS, HRT, F/M ratio and SADm explained the variation of microbial composition in the biofilm, whereas only MLSS did in the activated sludge. Microbial networks were constructed with the 10 environmental factors. The network results revealed that there were different topological characteristics between the biofilm and activated sludge networks, in which each of the 4 factors had different associations with microbial nodes. These results indicated that the different microbial associations were responsible for the variation of community composition between the biofilm and activated sludge.
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•Microbial communities of ten actual MBRs were scrutinized using Miseq sequencing.•Both microbial composition and structure differed among the MBRs.•Some environmental factors could explain the compositional variation among the MBRs.•Both microbial composition and networks were different between the biofilm and activated sludge.•It was confirmed that the variation in microbial association resulted in the compositional difference.
The goal of the current article is to update new findings in membrane fouling and emerging fouling mitigation strategies reported in recent years (post 2010) as a follow-up to our previous review ...published in Water Research (2009). According to a systematic review of the literature, membrane bioreactors (MBRs) are still actively investigated in the field of wastewater treatment. Notably, membrane fouling remains the most challenging issue in MBR operation and attracts considerable attention in MBR studies. In this review, we summarized the updated information on foulants composition and characteristics in MBRs, which greatly improves our understanding of fouling mechanisms. Furthermore, the emerging fouling control strategies (e.g., mechanically assisted aeration scouring, in-situ chemical cleaning, enzymatic and bacterial degradation of foulants, electrically assisted fouling mitigation, and nanomaterial-based membranes) are comprehensively reviewed. As a result, it is found that the fundamental understanding of dynamic changes in membrane foulants during a long-term operation is essential for the development and implementation of fouling control methods. Recently developed strategies for membrane fouling control denoted that the improvement of membrane performance is not our ultimate and only goal, less energy consumption and more green/sustainable fouling control ways are more promising to be developed and thus applied in the future. Overall, such a literature review not only demonstrates current challenges and research needs for scientists working in the area of MBR technologies, but also can provide more useful recommendations for industrial communities based on the related application cases.
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•Findings in MBR fouling and its control reported in recent years were reviewed.•Fouling mechanisms of biopolymers in MBRs have been comprehensively revealed.•Biologically induced dispersal of biofilm is effective in fouling control.•Electrically assisted fouling mitigation has attracted much attention in MBRs.•The stability and performance of nano-based membranes in MBRs should be tested.
•Thermophilic membrane bioreactor technologies are systematically reviewed.•Thermophilic membrane bioreactor technologies have a number of advantages.•Membrane fouling is the major challenge for ...thermophilic membrane bioreactor applications.•Challenges and opportunities of thermophilic membrane bioreactors are identified.
This study undertakes a state-of-the-art review on thermophilic membrane bioreactors (ThMBRs). Thermophilic aerobic membrane bioreactors (ThAeMBR) and thermophilic anaerobic membrane bioreactors (ThAnMBR) have been widely tested for various high-temperature industrial wastewater treatments at lab- and pilot-scale studies and full-scale applications. The biological and membrane performances of the ThAeMBRs and ThAnMBRs could be better, comparable or poorer, as compared to the mesophilic ones. In general, sludge yield was much lower, biodegradation kinetic was higher, and microbial community was less diversity in the ThAeMBR and ThAnMBR systems. The results from the literature show that ThMBR technology has demonstrated many advantages and is a promising technology for industrial wastewater treatment and sludge digestion. Furthermore, challenges and opportunities of various ThMBRs for industrial applications are identified and discussed.
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•MBBF-SMBR following ozonation efficiently removes organics from shale gas wastewater.•Compared with traditional SMBR, MBBF-SMBR shows higher removal of organics.•MBBF-SMBR shows low ...membrane fouling and suitable resilience during operation.•High amount of specific bacteria with biodegradation ability are found in MBBF-SMBR.•Enhanced genes about membrane transport and nitrogen metabolism are found in biofilm.
Shale gas wastewater (SGW) with complex composition and high salinity needs an economical and efficient method of treatment with the main goal to remove organics. In this study, a coupled system consisting of ozonation and moving-bed-biofilm submerged membrane bioreactor (MBBF-SMBR) was comprehensively evaluated for SGW treatment and compared with a similar train comprising ozonation and submerged membrane bioreactor (SMBR) without addition of carriers attaching biofilm. The average removal rates of MBBF-SMBR were 77.8% for dissolved organic carbon (DOC) and 37.0% for total nitrogen (TN), higher than those observed in SMBR, namely, 73.9% for DOC and 18.6% for TN. The final total membrane resistance in SMBR was 40.1% higher than that in MBBF-SMBR. Some genera that specifically contribute to organic removal were identified. Enhanced gene allocation for membrane transport and nitrogen metabolism was found in MBBF-SMBR biofilm, implying that this system has significant industrial application potential for organics removal from SGW.
Diclofenac (DCF) is a common anti-inflammatory pharmaceutical that is often detected in waste wasters, effluents and surface waters. Recently, DCF was included in the watch list of substances in EU ...that requires its environmental monitoring in the member states. DCF is also known to harmfully affect several environmental species already at concentrations of ≤1μg/l. This review focuses on the occurrence and fate of DCF in conventional wastewater treatment processes. Research done in this area was gathered and analyzed in order to find out the possibilities to enhance DCF elimination during biological wastewater treatment. More precisely, human metabolism, concentrations in wastewater influents and effluents, elimination rates in the treatment train, roles of sorption and biotransformation mechanisms during the treatment as well as formation of transformation products are reported. Additionally, the effect of process configuration, i.e. conventional activated sludge (CAS), biological nutrient removal (BNR), membrane bioreactor (MBR) and attached-growth bioreactor, and process parameters, i.e. solids retention time (SRT) and hydraulic retention time (HRT) are presented. Generally, DCF is poorly biodegradable which often translates into low elimination rates during biological wastewater treatment. Only a minor portion is sorbed to sludge. MBR and attached-growth bioreactors may result in higher elimination of DCF over CAS or BNR. Long SRTs (>150d) favor the DCF elimination due to sludge adaptation. Longer HRTs (>2–3d) could significantly increase the elimination of DCF during biological wastewater treatment. Bioaugmentation could be used to enhance DCF elimination, however, this requires more research on microbial communities that are able to degrade DCF. Also, further research is needed to gain more information about the deconjugation processes and biotic and abiotic transformation and the nature of transformation products.
•Diclofenac (DCF) is poorly biodegraded and sorbed into sludge.•Biotic elimination of DCF could be enhanced by the following techniques.•Use of MBR or attached-growth biomass process•Increase the hydraulic retention time to >2–3days•Enrich DCF degrading bacteria into the reactor (i.e. long SRTs or bioaugmentation)
