Wastewater Treatment Bioreactors Research Articles

A critical Review on Advanced Membrane Bioreactors for Wastewater Treatment: Fouling Reduction and Energy Demand

Objectives:Rapid industrialization has highlighted the importance of addressing environmental issues and the increasing demand for water supply. As a result, innovative solutions to improve water circulation management in both public and industrial sectors have been proposed, one of which is the introduction of Membrane Bioreactor (MBR) technology. This study aims to understand the mechanisms and characteristics of membrane fouling in MBR processes and compare the associated energy consumption, with the goal of improving process efficiency and energy performance.Methods:In this study, various factors influencing the MBR process were considered to analyze the mechanisms and characteristics of membrane fouling. The impact of fouling on the process was assessed, and energy consumption was compared. Specifically, the power consumption of flat-sheet and hollow-fiber MBRs was analyzed, focusing on the proportion of energy used for microbial treatment and membrane cleaning. The Specific Energy Demand (SED) was calculated to evaluate the energy consumption efficiency of different fouling control methods in MBRs.Results and Discussion:In typical MBR processes, 68.0% (flat-sheet) and 53.0% (hollow-fiber) of the power consumption is attributed to air scouring for microbial treatment and membrane cleaning. Notably, 57.0% (flat-sheet) and 36.0% (hollow-fiber) of the power is consumed to supply air for detaching adhered foulants to maintain filtration performance. These results indicate that aeration is a major energy consumer in MBR processes. SED is a critical indicator for assessing the energy consumption of specific fouling control methods, with typical MBR processes having an SED of 0.2-0.3kWh/m3. In contrast, using a non-aerated membrane module with reciprocating inertial force for fouling control reduces SED to 0.005-0.01 kWh/m3, representing a 20-60 fold decrease in energy consumption, highlighting the need for energy reduction.Conclusion:This study provides insights into fouling reduction characteristics in MBR processes, suggesting a new paradigm for enhancing the economic feasibility of MBR technology. Applying non-aerated membrane modules to reduce energy consumption can significantly improve MBR efficiency, contributing to energy reduction and environmentally friendly technology development. Therefore, strategies to maximize energy efficiency and minimize environmental impact in MBR processes are essential.

Greenhouse gas emission and denitrification kinetics of woodchip bioreactors treating onsite wastewater

The accurate evaluation of denitrification rate and greenhouse gas (GHG) emission in field-scale woodchip bioreactors for onsite wastewater treatment are problematic due to inevitably varied environmental conditions and underestimated GHG production with limited analysis of dissolved gas in field samples. To address these problems, batch incubation experiments were conducted with controlled conditions to precisely evaluate the denitrification kinetics and N2O and CH4 emission of both gaseous and dissolved phases in fresh (6 months) and aged (5 years) woodchip bioreactors treating onsite wastewater at high (1–3 mg L-1) and no (0 mg L-1) dissolved oxygen (DO) levels. NO3- removal rate decreased from 37.5–119.0 g NO3--N m-3d-1 at no DO to 8.8–16.6 g NO3--N m-3d-1 at high DO (1–3 mg L-1) due to the growth suppression of NO2- reducing microorganisms (37–55 % lower nirS+nirK abundance). However, the presence of high DO increased N2O emission level from 5.6–6.9 mg N2ON m-3 at no DO to 179.5–273.6 mg N2ON m-3) due to the enhanced growth of NO reducing microorganisms (1–7 times higher norB levels) and the decreased abundance of N2O reducing microorganisms (53–75 % lower nosZ abundance). On the other hand, increased DO level negatively correlated with CH4 production (1.0–3.9 g CH4-C m-3d-1) in fresh woodchips, while showed insignificant impact on CH4 production (0.1–1.4 g CH4-C m-3d-1) in aged woodchips. Woodchip age increase (5 years) negatively impacted the NO3- removal rate (75–85 % lower than fresh woodchips) and CH4 production rate (>3 times lower than fresh woodchips), probably due to the reduced biomass density of NO2- reducing microorganisms (52–58 % lower nirS+nirK abundance) and methanogens (95–98 % lower mcrA levels). The incubation results suggested that long hydraulic retention time (>2–5 days) and anaerobic/anoxic condition are preferred for the optimal NO3- removal and low N2O emission potential of woodchip bioreactors treating onsite wastewater.

Synergic treatment of domestic wastewater and food waste in an anaerobic membrane bioreactor demo plant: Process performance, energy consumption, and greenhouse gas emissions

Ambient operation and large-scale demonstration have limited the implementation and evaluation of anaerobic membrane bioreactors (AnMBRs) for low-strength wastewater treatment. Here, we studied these issues at an AnMBR demo plant that treats domestic wastewater and food waste together at ambient temperatures (7–28 °C). At varied hydraulic retention times (HRTs, 8–42 h), the AnMBR achieved a COD removal efficiency and biogas production of 80.4% ± 3.9% and 66.5 ± 9.4 NL/m3-Influent, respectively. Moreover, a stable high membrane flux of 14.4 L/m2/h was reached. The electric energy consumption for the AnMBR operation was 0.269–0.433 kW·h/m3, and 49.4%–91.3% could be compensated by the electric energy produced from methane production. At an HRT of 10 h, the AnMBR system demonstrated an impressively low net electric energy consumption of merely 0.05 kW·h/m3, resulting in a net greenhouse gas emission of 0.015 CO2-eq/m3, cutting 85% compared to the conventional activated sludge process. Achievements in this study provide key parameters for the ambient operation of AnMBR and demonstrate that AnMBR is an energy-saving and low-carbon solution for low-strength wastewater treatment.

Long-term operation of a full-scale membrane bioreactor for industrial wastewater treatment using polyvinyl fluoride hollow fiber membranes: A systematic evaluation during 18-year operation

A membrane bioreactor (MBR) is a robust, high-performance technology for wastewater treatment that has been commercialized and disseminated worldwide since 1990. Despite broad implementation of this technology in the wastewater sector, ultralong operation beyond the membrane lifetime has rarely been reported. Therefore, the objectives of this study were to investigate (1) the effectiveness of a manually-operated feedback strategy to prevent membrane biofouling by dosing with sodium hypochlorite and oxalic acid and (2) the organic carbon removal of industrial wastewater treated by a full-scale MBR system in a chemical plant. The manually-operated feedback strategy consisted of monitoring the transmembrane pressure (TMP) by a test module in a bench-scale MBR to detect an inflection point, that is, the point (15 kPa) at which the TMP switched from growing gradually to exponentially in time. Biocake formation became noticeable at the inflection point, suggesting the TMP at which the membrane should be chemically washed to prevent severe biofouling. A full-scale MBR system was installed with a polyvinylidene fluoride (PVDF) membrane for organic carbon removal. The membrane was washed with 3000 mg/L of sodium hypochlorite and 1 wt% oxalic acid when the TMP reached 15 kPa during operation. The MBR was successfully operated for over 18 years without the PVDF membrane being damaged or compromised by biofouling. Characterization of the foulants on the membrane surface revealed that membrane washing removed inorganic (calcium and iron) and organic (acid amides and polysaccharides) foulants, plausibly by the action of oxalic acid and sodium hypochlorite, respectively. Installing a robust PVDF membrane and performing chemical washing at an inflection point in the TMP dynamics enabled ultralong MBR operation beyond the regular membrane lifetime. The implementation of the advocated strategy paves the way for the low CO2 footprint operation of a PVDF MBR, which does not require frequent membrane replacement and laborious membrane ex-situ cleaning.

Artificial neural network modeling for the prediction, estimation, and treatment of diverse wastewaters: A comprehensive review and future perspective

The application of artificial neural networks (ANNs) in the treatment of wastewater has achieved increasing attention, as it enhances the efficiency and sustainability of wastewater treatment plants (WWTPs). This paper explores the application of ANN-based models in WWTPs, focusing on the latest published research work, by presenting the effectiveness of ANNs in predicting, estimating, and treatment of diverse types of wastewater. Furthermore, this review comprehensively examines the applicability of the ANNs in various processes and methods used for wastewater treatment, including membrane and membrane bioreactors, coagulation/flocculation, UV-disinfection processes, and biological treatment systems. Additionally, it provides a detailed analysis of pollutants viz organic and inorganic substances, nutrients, pharmaceuticals, drugs, pesticides, dyes, etc., from wastewater, utilizing both ANN and ANN-based models. Moreover, it assesses the techno-economic value of ANNs, provides cost estimation and energy analysis, and outlines promising future research directions of ANNs in wastewater treatment. AI-based techniques are used to predict parameters such as chemical oxygen demand (COD) and biological oxygen demand (BOD) in WWTP influent. ANNs have been formed for the estimation of the removal efficiency of pollutants such as total nitrogen (TN), total phosphorus (TP), BOD, and total suspended solids (TSS) in the effluent of WWTPs. The literature also discloses the use of AI techniques in WWT is an economical and energy-effective method. AI enhances the efficiency of the pumping system, leading to energy conservation with an impressive average savings of approximately 10%. The system can achieve a maximum energy savings state of 25%, accompanied by a notable reduction in costs of up to 30%.

Life cycle and efficiency assessment of fixed-bed bioreactor using recycled shredded plastics compared with conventional activated sludge bioreactor for dairy wastewater treatment

Adopting a highly efficient and low-cost bed bioreactor for the treatment of high-strength dairy wastewater has received unprecedented significance. Therefore, the concept of “waste as a resource” was brought up in this study and recycled shredded plastics (RSPs) were used to structure a fixed bed for activated sludge expansion. The performance of the RSP-attached growth system (AGS) and conventional suspended growth system (SGS) with intermittent anaerobic/aerobic conditions were scrutinized for dairy wastewater treatment. In addition, their environmental repercussions, greenhouse gas (GHG) emissions, and ecological footprint were explored to provide innovative insights into the field of research. The AGS system outperformed with substantial COD, nitrate, and phosphorus removal efficiencies (>89 %) in hydraulic retention time of 4 h, aeration time of 27 min, and COD/P ratio of 120. Notably, the SGS system outcompeted in the environmental impacts and energy usage, which accounted for 1.03–4.38 times higher than that for the AGS system. The electricity consumption and wastewater treatment process had striking roles in human carcinogenic toxicity, freshwater/marine ecotoxicity, and human health. The most required energy for AGS and SGS operations was supplied by fossil fuels, which increment GHG emissions from 4.31 to 8.77 kg CO2 eq for the AGS and SGS, respectively. Moreover, the reduction of electricity usage dramatically decreased human carcinogenic toxicity and marine ecotoxicity. Summing up, this study sheds light on the RSPs' capability to support activated sludge and ensure alignment with environmental criteria for dairy wastewater treatment.

Benefits of fungal-to-bacterial quorum quenching as anti-biofouling strategy in membrane bioreactors for wastewater treatment and water reuse

This study addresses membrane biofouling in membrane bioreactors (MBRs) by exploring fungal-to-bacterial quorum quenching (QQ) strategies. While most research has been focused on bacterial-to-bacterial QQ tactics, this study identified fungal strain Vanrija sp. MS1, which is capable of degrading N-acyl-homoserine lactones (signaling molecules of Gram-negative bacteria). To determine the benefits of fungal over bacterial strains, after immobilization on fluidizing spherical beads in an MBR, MS1 significantly reduced the fouling rate by 1.8-fold compared to control MBR, decreased extracellular polymeric substance levels in the biofilm during MBR operation, and favorably changed microbial community and bacterial network, resulting in biofouling mitigation. It is noteworthy that, unlike Rhodococcus sp. BH4, MS1 enhanced QQ activity when switching from neutral to acidic conditions. These results suggest that MS1 has the potential for the effective treatment of acidic industrial wastewater sources such as semiconductor and secondary battery wastewater using MBRs.

Co-occurrence of simultaneous carbon and nitrogen removal and in-situ sludge separation in a novel single unit combined airlift bioreactor (CALBR) for milk processing wastewater treatment

Combined anaerobic-aerobic bioreactors offer considerable potential for treating different industrial wastewaters. However, difficulty in maintaining a stable coexistence of anaerobic, anoxic, and aerobic microbial communities and the necessity of space-consuming external settlers remain as crucial drawbacks associated with these systems. In this study, an innovative single stage combined airlift bioreactor (CALBR) comprising multiple bioreactors (anaerobic/anoxic/aerobic) and an internal settler (a rotating spiral separator for in-situ separation of biomass) was exploited to achieve simultaneous carbon and nitrogen removal from milk processing wastewater (MPW). Results demonstrated that the anaerobic pre-treatment zone made a substantial contribution towards COD and TN removal. Successful biomass separation and high effluent quality revealed that the rotating spiral separator can be used as a coupled clarifier to sustain higher biomass concentration through boosting the sludge compressibility and settleability which further upgrades the overall treatment bioprocess. sCOD removal, TN removal, SVI, and effluent turbidity of ˃96%, ˃75%, ˂90 mL/g, and ˂10 NTU were reached, respectively under optimum condition. The outcomes suggested that the novel CALBR is a promising technology which has a great potential to be transferred into practical implementation for high-rate combined biological wastewater treatment and sludge separation.

Investigation of the performance of the combined moving bed bioreactor-membrane bioreactor (MBBR-MBR) for textile wastewater treatment

The present study focused on the investigation of the performance of a Moving Bed Bioreactor coupled with a Membrane Bioreactor (MBBR-MBR) on a small scale for textile wastewater treatment. The parameters examined in this study included the removal efficiency of chemical oxygen demand (COD), biochemical oxygen demand (BOD), total suspended solids (TSS), turbidity, color, and heavy metals (HM). The two reactors were operated consecutively and maintained aerobic conditions. The idea is to reduce the pollutant load significantly through the activity of microorganism attached to the biofilm covered carriers in MBBR and successive membrane filtration. The system demonstrated a favorable outcome even in a smaller hydraulic retention time (HRT) of 1 day, which presents a significant advantage in terms of cost and space saving. The removal effectiveness of COD attained a maximum of 92 %, BOD reached a maximum of 95 %, and the color removal performance obtained a removal efficiency of 87 %. Furthermore, the treatment showed remarkable efficiency in removing up to 100 % of TSS and 96 % of turbidity. Additionally, an evaluation was conducted on the elimination of heavy metals, including Zinc (Zn), Lead (Pb), Chromium (Cr), and Iron (Fe). The efficacy of removing these HMs was found to exceed 85 %. All these favorable outcomes contribute to the improvement of effluent quality, mitigation of contamination hazards, and fouling reduction.

Effect of long chain fatty acids on biogas production and biochemical kinetics in anaerobic bioreactors: a review

Long Chain Fatty Acids (LCFAs) are the primary intermediate byproduct of the lipid (fats, oils, and greases) degradation process, and if they accumulate in high concentrations, they can cause failure or reduce the performance of anaerobic bioreactors due to sludge flotation issues, biochemical kinetics problems for soluble substrates, inhibition of microbial activity, and inefficient biogas recovery. Understanding the biochemical kinetics of anaerobic bioreactors requires taking into account the entire process, including microbe growth, substrate degradation, and product synthesis. Biochemical kinetics of anaerobic treatment is the study of polymer biodegradation rates of insoluble organic matter in wastewater, which is the mechanism of bond breaking and bond formation in biochemical reactions. As a result, biochemical kinetics allow for the design of both desired and undesirable reaction phases. The kinetic parameters acquired are utilized to design, operate, and optimize anaerobic bioreactors for wastewater treatment on a technical scale.

Exploring novel quorum quenching strain: Enhanced disrupting autoinducer-2 bacterial communication to combat biofouling in membrane bioreactor for wastewater treatment

Prior investigations concerning quorum quenching (QQ), which hinders quorum sensing (QS) in microbial communication, concentrated predominantly on N-acylhomoserine lactones (AHLs), which are communicated merely by gram-negative bacteria. However, to combat biofouling more effectively, particularly biofilm-related issues, it is important to explore the inhibition of autoinducer-2 (AI-2), a universal signal (interspecies communication) employed by both gram-negative and gram-positive bacteria. This study aimed to isolate and identify novel strains capable of more effectively inhibiting AI-2 signaling for use in engineering fields. The results revealed that the newly isolated strain Pantoea sp. PL-1 demonstrated remarkable efficacy in attenuating AI-2 signals, leading to a substantial reduction in the AI-2 precursor (S)-4,5-dihydroxy-2,3-pentandione (DPD) in both its pellet (with a DPD removal efficiency of 90.8 % after 180 min, with a rate constant of k = 0.8 h−1) and supernatant form (66.9 %, k = 0.37 h−1). Interestingly, the findings indicate that strain DKY-1, a strain previously reported to exhibit AI-2 QQ activity, only reduced DPD levels in its supernatant form (extracellular activity), while both the pellet and the supernatant of strain PL-1 demonstrated AI-2 QQ activity, indicating both intracellular and extracellular QQ activity. Adding the PL-1 supernatant to co-cultures of two AI-2 QS strains, E. coli K12 and P. mirabilis, successfully reduced DPD by 40 % and 70 %, respectively, without impeding their growth. Additionally, when assessing the impact of PL-1 to minimize membrane biofouling in a membrane bioreactor, it demonstrated superior performance compared to the DKY-1 strain, with a 40 % improvement. The AI-2 QQ compound of PL-1 has been identified as highly hydrophilic and low-molecular-weight, and its exact properties have not yet been fully elucidated. Therefore, uncovering its identity may be an important goal for future research.

Algal-Based Hollow Fiber Membrane Bioreactors for Efficient Wastewater Treatment: A Comprehensive Review

The treatment of living organisms is a critical aspect of various environmental and industrial applications, ranging from wastewater treatment to aquaculture. In recent years, algal-based hollow fiber membrane bioreactors (AHFMBRs) have emerged as a promising technology for the sustainable and efficient treatment of living organisms. This review provides a comprehensive examination of AHFMBRs, exploring their integration with algae and hollow fiber membrane systems for diverse applications. It also examines the applications of AHFMBRs in various areas, such as nutrient removal, wastewater treatment, bioremediation, and removal of pharmaceuticals and personal care products. The paper discusses the advantages and challenges associated with AHFMBRs, highlights their performance assessment and optimization strategies, and investigates their environmental impacts and sustainability considerations. The study emphasizes the potential of AHFMBRs in achieving enhanced nutrient removal, bioremediation, and pharmaceutical removal while also addressing important considerations such as energy consumption, resource efficiency, and ecological implications. Additionally, it identifies key challenges and offers insights into future research directions. Through a systematic analysis of relevant studies, this review aims to contribute to the understanding and advancement of algal-based hollow fiber membrane bioreactors as a viable solution for the treatment of living organisms.

Performance of Fe-dosing membrane bioreactor and evaluation of phosphorus recovery as vivianite after long-term operation

In this study, the influence of high concentration of iron on the nutrient removal, membrane fouling and microbial diversity of membrane bioreactor for wastewater treatment were systematically investigated. Moreover, the potential of phosphorus recovery in the form of vivianite was assessed after the long-term operation. The results show that TP concentration in effluent was decreased to 1.07 ± 0.47 mg/L (without Fe addition), 0.41 ± 0.23 mg/L (Fe/P = 2), 0.20 ± 0.12 mg/L (Fe/P = 4). Compared with control group, the TN concentration in effluent was higher at the high concentration of iron, which was due to the decreased nitrite-oxidizing bacteria (NOB) by microbial population analysis. Membrane fouling was alleviated by enlarging floc size and reducing supernatant COD via adding iron. Besides, it was detected that the amorphous ferric oxide and Fe(III) bound phosphorus were the main Fe and P speciation and vivanite (ca. 29 %). The anaerobic environment was conducive to the formation of vivianite and the phosphorus recovery as vivanite was recommended based on the results of current study.

Performance evaluation and microbial dynamics of submerged anaerobic membrane bioreactors for municipal wastewater treatment

It is challenging to treat municipal wastewater anaerobically and gain energy to provide an economically sustainable process. In this study, the municipal wastewater treatment performance of AnMBR was investigated, and the membrane fouling along with the microbial community dynamics were evaluated. In this scope, COD and nutrient removal, methane production, SMP and EPS, TMP, CST, SRF, and microbial community within the reactor were investigated. AnMBR was operated in two periods. In the first period (P1), HRT and flux averaged 23.5 ± 0.4 h and 3 ± 0.1 LMH, respectively. In the second period (P2), HRT and flux averaged 12.4 ± 1.2 h and 5.7 ± 0.5 LMH, respectively. The OLRs were 0.53 ± 0.04 and 1.00 ± 0.14 kg/(m3·d) for P1 and P2, respectively. Maximum COD removal efficiency around 92 % was obtained while average methane yield was 207 ± 17.3 mL CH4/gCODconsumed. AnMBR permeate has the potential for agricultural irrigation due to its high nutrient content and quality. The bacterial community abundance changed through the acclimation and operation of AnMBR. Carbohydrate and amino acid metabolisms are the major metabolism cluster. The bacterial family fermenting carbohydrates under anaerobic conditions Anaerolineaceae and anaerobic mesophilic acetogens Bacteroidetes were the predominant families in the bacterial community. No significant fouling has been observed during AnMBR operation, as the modification of the membrane module has contributed to the alleviation of fouling, which resulted in obtaining stable flux and constant TMP. The treatment of municipal wastewater with AnMBR can be energy-positive without heating in tropical climates.

A novel γ-Fe3O4-N-BC combined membrane bioreactor for wastewater treatment: Performance and mechanism

In this study, a new type of iron–nitrogen doped biochar (γ- Fe3O4-N-BC) was developed to improve nutrient removal efficiency and mitigate membrane fouling in combination with MBR. The characteristion of γ-Fe3O4-N-BC, N-BC, and BC revealed that the BET surface area (SBET) of γ-Fe3O4-N-BC, which was 1320.86 m2/g, was greater than that of N-BC (702.75 m2/g) and BC (1033.63 m2/g). The excellent SBET exhibited by γ-Fe3O4-N-BC compared to that of the other biochars is attributed to hydrogen bonding and electrostatic interactions. Compared to the addition of N-BC or BC or the absence of biochar, the addition of γ-Fe3O4-N-BC in the membrane bioreactor (MBR) resulted in superior wastewater treatment performance, for which the average removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), and total phosphorus (TP) were 94.65 %, 82.56 %, and 65.90 %, respectively. Moreover, after inoculation with γ-Fe3O4-N-BC, the TMP increase rate and time required to reach 42.37 kPa were 2.35 kPa/d and 18 d, respectively. The investigation of the effect of the γ-Fe3O4-N-BC concentration on MBR performance showed that the nutrient removal efficiency in the 500-MBR greater than that in the 350-MBR, 650-MBR, and 800-MBR, and that the membrane fouling was more ameliorative. A mechanistic investigation demonstrated that the 500-MBR had a beneficial influence on sludge biomass growth and helped to improve the nutrient removal capacity of the MBR. The 500-MBR improved the flocculability and stability of the sludge flocs in the MBR by increasing particle size and zeta potential. Changes in the extracellular polymeric substance (EPS) concentration and the smaller protein (PN) / polysaccharide (PS) ratio in 500-MBR also had significant impacts on alleviating the adhesion and accumulation of fouling layers on the improved membrane surface. Consequently, this study provides a new method for nutrient removal and membrane fouling mitigation in the MBR process.

Anti-biofouling performance and microbial communities of an integrated fixed-film activated sludge membrane bioreactor with a fibrous carrier material: Pilot-scale demonstration

Widespread use of membrane bioreactors for high-performance wastewater treatment depends on the prevention of biofouling during membrane filtration, which can reduce operating costs. Biofouling is usually prevented using mechanical and chemical membrane treatment methods, which can be time-consuming and expensive. In this study, we developed bio-capsules as a fluidizing carrier material in an integrated fixed-film activated sludge membrane bioreactor (IFAS-MBR). The bio-capsules were prepared from moniliform polyvinylidene chloride fibrous balls enclosed in a spherical plastic basket, and could harbor protozoa and metazoa. A pilot-scale anoxic–oxic IFAS-MBR system with a total volume of 132 m3 was operated to remove organic carbon and nitrogen from municipal wastewater at a high permeate flux (0.84 m3/m2/day). The efficacy of the bio-capsules and the prokaryotic/eukaryotic community structures in the system were investigated. After operation for 1 year, the system demonstrated stable removal of organic carbon (76.0 % ± 15.5 % as total organic carbon, 93.1 ± 5.3 % as BOD, and 88.5 ± 5.2 % as CODMn) and nitrogen (71.3 % ± 9.3 %) despite fluctuations in the influent concentrations. Increases in transmembrane pressure (TMP) were retarded from its increase rates from 0.56 kPa/day to 0.149–0.224 kPa/day by the bio-capsules, and the TMP was kept constant at around 20 kPa throughout the operational period. High-throughput sequencing of 16S rRNA gene amplicons showed that the prokaryotic family Pirellulaceae was metabolically active and correlated with the TMP. According to the 18S rRNA gene sequencing, the eukaryotic metazoan Bdelloidea was more abundant in the bio-capsules than in activated sludge, which was supported by microscopic observations. These results suggest that the application of bio-capsules prevents increases in the TMP by harboring the procaryotes and eukaryotes responsible for biofouling mitigation in the IFAS-MBR system.

Evaluation of the Effect of Microalgae Chlorella vulgaris on the Performance of Membrane Bioreactor for Industrial Wastewater Treatment

Water pollution, especially from industry, is a problem that continues to emerge and even get worse. Rising sludge events often occur in industrial wastewater treatment processes. Process engineering with the addition of microalgae is proposed in this study to overcome the occurrence of rising sludge and improve wastewater quality based on dissolved oxygen levels. The control variables used were MLSS 1000 mg/L, microalgae Chlorella vulgaris 106 L, and urea and TSP 1,75 kg each. The dependent variable is rising sludge and DO levels while the independent variable is time. This research went through several stages, namely seeding microalgae, seeding microalgae into activated sludge in MBBR, experimenting with combining microalgae and activated sludge in MBBR, and installing ultrafiltration membranes with a WWTP capacity of 150 m3/day. The addition of microalgae in the MBBR process has a positive impact in improving the quality of industrial wastewater, which is characterized by the absence of rising sludge and DO levels exceeding the minimum threshold.

Biofouling Control by Facultative Quorum Quenching Bacteria in Anaerobic Membrane Bioreactors for High-Strength Wastewater Treatment

Biofouling Control by Facultative Quorum Quenching Bacteria in Anaerobic Membrane Bioreactors for High-Strength Wastewater Treatment

Polyethylene terephthalate cap‐based bioreactors for combined domestic and dye wastewater treatment

AbstractIn the current study, a sequencing batch reactor (SBR), a sequencing batch biofilm reactor (SBBR) and a moving bed biofilm reactor (MBBR) were designed and used to treat actual samples of combined domestic and dye (Congo red) wastewaters over a 10‐hour cycle. A new application of reusing plastic bottle caps in the SBBR and MBBR was examined. In the SBR, maximum chemical oxygen demand (COD) removal of up to 66% ± 3% was achieved after nine cycles of operation. In the SBBR, a rapid increase in COD removal efficiency was observed during the first cycle, with a noticeable improvement in performance in subsequent cycles, eventually reaching a maximum COD removal efficiency of 77% ± 3%. In the MBBR, maximum COD removal of up to 88% ± 3% was achieved after nine cycles of operation. The biodegradation occurred during two phases in the SBR and SBBR, as an anaerobic phase in the first 2 hours and then as an aerobic phase in the last 8 hours of operation; the MBBR operated in the fully saturated aerobic phase for 10 hours. Of the three reactors used, results for the MBBR in the fully aerobic condition by using polyethylene terephthalate caps as a biocarrier, demonstrated the optimum conditions under which to treat and biodegrade Congo red at all concentration in each cycle. The maximum removal efficiency, which equalled 99% ± 1%, was recorded at an optimal concentration of 50 mg/L. Additionally, five kinetic models were proposed to assess microbial growth activity, and the results demonstrated the elimination of toxic effects when using polyethylene terephthalate caps as biocarriers in the MBBR. The laboratory experiments were consistent with the Monod model.

Microalgae biofilm photobioreactor and its combined process for long-term stable treatment of high-saline wastewater achieved high pollutant removal efficiency

High-saline wastewater treatment processes have a high energy demand, while microalgae-driven wastewater biotechnology is both economical and environmentally friendly, and the use of microalgae to treat high-saline wastewater can effectively reduce energy consumption. However, it is unclear whether the performance of microalgae reactor can be stable for a long time. In this study, an open continuous-flow biofilm photobioreactor using Dunaliella salina was innovatively constructed, and operated in combination with a membrane bioreactor (MBR) for high-saline wastewater treatment. The purpose of this study was to investigate the long-term performance of MBR, MBPBR alone and their combined operation for the removal of organic matter, phosphorus and nitrogen, explore the pathway and mechanism of nitrogen and phosphorus removal by MBPBR, and evaluate the feasibility of MBPBR-MBR integrated system for the treatment of saline wastewater. The MBR effectively removed most of the organic matter and converted ammonia nitrogen into nitrate nitrogen, which is a preferred nitrogen source for the growth of Dunaliella salina, thereby providing favorable water quality for Dunaliella salina in the subsequent MBPBR. The MBPBR, with a hydraulic retention time (HRT) of 72 h, achieved a NO3--N removal load of 74.9 g N/(m3∙d) and a removal efficiency of approximately 60 %, and the PO43--P removal load of 8.33 g P/(m3∙d) and removal efficiency of over 80 %. The MBR-MBPBR system demonstrated long-term stability, achieving removal efficiencies of 84.3 %, 81.6 %, and 91.0 % for COD, TN and PO43--P, respectively. Within the MBPBR, the growth of algae and their assimilation contributed 44.9 % and 38.7 % of the nitrogen and phosphorus removal, respectively. The abundance of Dunaliella salina in the MBPBR remained at approximately 90 % for over 40 days of operation, providing an opportunity for Dunaliella salina recovery. These findings provide valuable insights into the utilization of microalgae for the treatment of high-salinity wastewater, while also supporting the practical implementation of microalgae-based treatment methods for such wastewater.