Anaerobic membrane bioreactors for treatment of emerging contaminants: A review

Unveiling the influence of microaeration and sludge recirculation on enhancement of pharmaceutical removal and microbial community change of the novel anaerobic baffled biofilm - membrane bioreactor in treating building wastewater

This research aims to conduct a comparative investigation of the role played by microaeration and sludge recirculation in the novel anaerobic baffled biofilm-membrane bioreactor (AnBB-MBR) for enhancing pharmaceutical removal from building wastewater. Three AnBB-MBRs - R1: AnBB-MBR, R2: AnBB-MBR with microaeration and R3: AnBB-MBR with microaeration and sludge recirculation - were operated simultaneously to remove Ciprofloxacin (CIP), Caffeine (CAF), Sulfamethoxazole (SMX) and Diclofenac (DCF) from real building wastewater at the hydraulic retention time (HRT) of 30 h for 115 days. From the removal profiles of the targeted pharmaceuticals in the AnBB-MBRs, it was found that the fixed-film compartment (C1) could significantly reduce the targeted pharmaceuticals. The remaining pharmaceuticals were further removed with the microaeration compartment. R2 exhibited the utmost removal efficiency for CIP (78.0 %) and DCF (40.8 %), while SMX was removed most successfully by R3 (microaeration with sludge recirculation) at 91.3 %, followed by microaeration in R2 (88.5 %). For CAF, it was easily removed by all AnBB-MBR systems (>90 %). The removal mechanisms indicate that the microaeration in R2 facilitated the adsorption of CIP onto microaerobic biomass, while the enhanced biodegradation of CAF, SMX and DCF was confirmed by batch biotransformation kinetics and the adsorption isotherms of the targeted pharmaceuticals. The microbial groups involved in biodegradation of the targeted compounds under microaeration were identified as nitrogen removal microbials (Nitrosomonas, Nitrospira, Thiobacillus, and Denitratisoma) and methanotrophs (Methylosarcina, Methylocaldum, and Methylocystis). Overall, explication of the integration of AnBB-MBR with microaeration (R2) confirmed it as a prospective technology for pharmaceutical removal from building wastewater due to its energy-efficient approach characterized by minimal aeration supply.

Anaerobic removal of contaminants of emerging concern in municipal wastewater: Eco-toxicological risk evaluation and strategic selection of optimal treatment

In the last decades, the interest for anaerobic process as a mainstream treatment of municipal wastewater increased due to the development of high-rate anaerobic bioreactors able to achieve removal kinetics comparable to the aerobic ones. Moreover, they have the additional advantages of energy production, nutrient recovery and reduced excess sludge yield, which are interesting features in the frame of sustainability wastewater treatment goals. These appealing factors increased the research demand to evaluate the potential of the anaerobic removal for contaminants of emerging concern (CECs) in municipal wastewater. However, despite the growing interest for the subject, literature is still fragmentary and reviews are mainly focused on specific technologies and target compounds or groups of compounds. We propose this review with the main objectives of presenting the state of knowledge, the performances of anaerobic systems for CECs' removal and, more important, to give the reader guidelines for optimal treatment selection. In the first part, a general overview of the investigated technologies at different scale, with a special focus on the recently proposed enhancements, is presented. Collected data are analysed to select the target CECs and the analysis results employed to define the optimal technological solution for their removal. A first novelty element of the paper is the original procedure for contaminant selection consisting of a risk assessment tool for CECs, based on their frequency of detection, concentration and potential for biosorption in wastewater treatment plants. Data of selected target CECs are combined with compound and technology performance data to implement a flowchart tool to evaluate the optimal treatment strategy, which constitute another, even more important, novelty element of this study.

Advances in identifying and managing emerging contaminants in aquatic ecosystems: Analytical approaches, toxicity assessment, transformation pathways, environmental fate, and remediation strategies

Emerging contaminants (ECs) are increasingly recognized as threats to human health and ecosystems. This review evaluates advanced analytical methods, particularly mass spectrometry, for detecting ECs and understanding their toxicity, transformation pathways, and environmental distribution. Our findings underscore the reliability of current techniques and the potential of upcoming methods. The adverse effects of ECs on aquatic life necessitate both in vitro and in vivo toxicity assessments. Evaluating the distribution and degradation of ECs reveals that they undergo physical, chemical, and biological transformations. Remediation strategies such as advanced oxidation, adsorption, and membrane bioreactors effectively treat EC-contaminated waters, with combinations of these techniques showing the highest efficacy. To minimize the impact of ECs, a proactive approach involving monitoring, regulations, and public education is vital. Future research should prioritize the refining of detection methods and formulation of robust policies for EC management.

A systematic review on the current situation of emerging pollutants in Mexico: A perspective on policies, regulation, detection, and elimination in water and wastewater

Emerging pollutants (EPs) emerged as a group of new compounds whose presence in the environment has been widely detected in Mexico. In this country, different concentrations of pharmaceutical compounds, pesticides, dyes, and microplastics have been reported, which vary depending on the region and the analyzed matrix (i.e., wastewater, surface water, groundwater). The evidence of the EPs' presence focuses on the detection of them, but there is a gap in information regarding is biomonitoring and their effects in health in Mexico. The presence of these pollutants in the country associated with lack of proper regulations in the discharge and disposal of EPs. Therefore, this review aims to provide a comprehensive view of the current environmental status, policies, and frameworks regarding Mexico's situation. The review also highlights the lack of information about biomonitoring since EPs are present in water even after their treatment, leading to a critical situation, which is high exposure to humans and animals. Although, technologies to efficiently eliminate EPs are available, their application has been reported only at a laboratory scale thus far. Here, an overview of health and environmental impacts and a summary of the research works reported in Mexico from 2014 to 2023 were presented. This review concludes with a concrete point of view and perspective on the status of the EPs' research in Mexico as an alert for government entities about the necessity of measures to control the EPs disposal and treatment.

Anaerobic Digestion as a Core Technology in Addressing the Global Sanitation Crisis: Challenges and Opportunities

Successfully addressing the complex global sanitation problem is a massive undertaking. Anaerobic digestion (AD), coupled with post-treatment, has been identified as a promising technology to contribute to meeting this goal. It offers multiple benefits to the end users, such as the potential inactivation of pathogenic microorganisms in waste and the recovery of resources, including renewable energy and nutrients. This feature article provides an overview of the most frequently applied AD systems for decentralized communities and low- and lower-middle-income countries with an emphasis on sanitation, including technologies for which pathogen inactivation was considered during the design. Challenges to AD use are then identified, such as experience, economics, knowledge/training of personnel and users, and stakeholder analysis. Finally, accelerators for AD implementation are noted, such as the inclusion of field studies in academic journals, analysis of emerging contaminants, the use of sanitation toolboxes and life cycle assessment in design, incorporation of artificial intelligence in monitoring, and expansion of undergraduate and graduate curricula focused on Water, Sanitation, and Hygiene (WASH).

Recent advances in microbial engineering approaches for wastewater treatment: a review

In the present era of global climate change, the scarcity of potable water is increasing both due to natural and anthropogenic causes. Water is the elixir of life, and its usage has risen significantly due to escalating economic activities, widespread urbanization, and industrialization. The increasing water scarcity and rising contamination have compelled, scientists and researchers, to adopt feasible and sustainable wastewater treatment methods in meeting the growing demand for freshwater. Presently, various waste treatment technologies are adopted across the globe, such as physical, chemical, and biological treatment processes. There is a need to replace these technologies with sustainable and green technology that encourages the use of microorganisms since they have proven to be more effective in water treatment processes. The present review article is focused on demonstrating how effectively various microbes can be used in wastewater treatment to achieve environmental sustainability and economic feasibility. The microbial consortium used for water treatment offers many advantages over pure culture. There is an urgent need to develop hybrid treatment technology for the effective remediation of various organic and inorganic pollutants from wastewater.

Selection of priority emerging contaminants in surface waters of India, Pakistan, Bangladesh, and Sri Lanka

The challenge of emerging contaminants (ECs) in global surface water bodies and particularly in low- and middle-income countries such as India, Pakistan, Bangladesh, and Sri Lanka, is evident from the literature. The complexity arises from the high costs involved in EC analysis and the extensive list of ECs, which complicates the selection of essential compounds for scientific and regulatory investigations. Consequently, monitoring programs often include ECs that may have minimal significance within a region and do not pose known or suspected ecological or human health risks. This study aims to address this issue by employing a multi-risk assessment approach to identify priority ECs in the surface waters of the aforementioned countries. Through an analysis of occurrence levels and frequency data gathered from published literature, an optimized risk quotient (RQ) was derived. The findings reveal a priority list of 38 compounds that exhibit potential environmental risks and merit consideration in future water quality monitoring programs. Furthermore, the majority of antibiotics in India (12 out of 17) and Pakistan (7 out of 17) exhibit a risk quotient for antimicrobial resistance selection (RQAMR) greater than 1, highlighting the need for devising effective strategies to mitigate the escalation of antibiotic resistance in the environment.

The fate of sulfamethoxazole and trimethoprim in a micro-aerated anaerobic membrane bioreactor and the occurrence of antibiotic resistance in the permeate

This study investigates the effects, conversions, and resistance induction, following the addition of 150 μg·L-1 of two antibiotics, sulfamethoxazole (SMX) and trimethoprim (TMP), in a laboratory-scale micro-aerated anaerobic membrane bioreactor (MA-AnMBR). TMP and SMX were removed at 97 and 86%, indicating that micro-aeration did not hamper their removal. These antibiotics only affected the pH and biogas composition of the process, with a significant change in pH from 7.8 to 7.5, and a decrease in biogas methane content from 84 to 78%. TMP was rapidly adsorbed onto the sludge and subsequently degraded during the long solids retention time of 27 days. SMX adsorption was minimal, but the applied hydraulic retention time of 2.6 days was sufficiently long to biodegrade SMX. The levels of three antibiotic-resistant genes (ARGs) (sul1, sul2, and dfrA1) and one mobile genetic element biomarker (intI1) were analyzed by qPCR. Additions of the antibiotics increased the relative abundances of all ARGs and intI1 in the MA-AnMBR sludge, with the sul2 gene folding 15 times after 310 days of operation. The MA-AnMBR was able to reduce the concentration of antibiotic-resistant bacteria (ARB) in the permeate by 3 log.

Rapid adsorption of benzotriazole onto oxidized carbon cloth as an easily separable adsorbent

A commercial carbon cloth (CC) was oxidized by HNO3 acid and the features of the plain and oxidized CC were evaluated. The results of characterization illustrated that HNO3 oxidization duplicated the oxygen-containing functional groups and the surface area of the CC. The adsorption performance of the plain and oxidized CC (Oxi-CC) toward benzotriazole (BTR) was compared. The results disclosed that the uptake of BTR by oxidized CC was greater than the plain CC. Thence, the affinity of oxidized CC toward BTR was assessed at different conditions. It was found that the adsorption was quick, occurred at pH 9 and improved by adding NaCl or CaCl2 to the BTR solution. The kinetic and isotherm studies revealed that the surface of Oxi-CC is heterogeneous and the adsorption of BTR follows a physical process and forms multilayer over the Oxi-CC surface. The regenerability and reusability study illustrated that only deionized water can completely regenerate the Oxi-CC and that the Oxi-CC can be reused for five cycles without any loss of performance. The high maximum adsorption capacity of Dubinin-Radushkevich isotherm model (252 mg/g), ease of separation and regeneration, and maintaining the adsorption capacity for several cycles revealed the high efficiency and economical and environmental feasibility of Oxi-CC as an adsorbent for BTR.

In-depth insight on microbial electrochemical systems coupled with membrane bioreactors for performance enhancement: a review

A conventional activated sludge (CAS) system has traditionally been used for secondary treatment in wastewater treatment plants. Due to the high cost of aeration and the problem of sludge treatment, researchers are developing alternatives to the CAS system. A membrane bioreactor (MBR) is a technology with higher solid-liquid separation efficiency. However, the use of MBR is limited due to inevitable membrane fouling and high energy consumption. Membrane fouling requires frequent cleaning, and MBR components must be replaced, which reduces membrane lifetime and operating costs. To overcome the limitations of the MBR system, a microbial fuel cell-membrane bioreactor (MFC-MBR) coupling system has attracted the interest of researchers. The design of the novel bioelectrochemical membrane reactor (BEMR) can effectively couple microbial degradation in the microbial electrochemical system (MES) and generate a microelectric field to reduce and alleviate membrane fouling in the MBR system. In addition, the coupling system combining an MES and an MBR can improve the efficiency of COD and ammonium removal while generating electricity to balance the energy consumption of the system. However, several obstacles must be overcome before the MFC-MBR coupling system can be commercialised. The aim of this study is to provide critical studies of the MBR, MES and MFC-MBR coupling system for wastewater treatment. This paper begins with a critical discussion of the unresolved MBR fouling problem. There are detailed past and current studies of the MES-MBR coupling system with comparison of performances of the system. Finally, the challenges faced in developing the coupling system on a large scale were discussed.

Physico-chemical and biological remediation techniques for the elimination of endocrine-disrupting hazardous chemicals

Due to their widespread occurrence and detrimental effects on human health and the environment, endocrine-disrupting hazardous chemicals (EDHCs) have become a significant concern. Therefore, numerous physicochemical and biological remediation techniques have been developed to eliminate EDHCs from various environmental matrices. This review paper aims to provide a comprehensive overview of the state-of-the-art remediation techniques for eliminating EDHCs. The physicochemical methods include adsorption, membrane filtration, photocatalysis, and advanced oxidation processes. The biological methods include biodegradation, phytoremediation, and microbial fuel cells. Each technique's effectiveness, advantages, limitations, and factors affecting their performance are discussed. The review also highlights recent developments and future perspectives in EDHCs remediation. This review provides valuable insights into selecting and optimizing remediation techniques for EDHCs in different environmental matrices.

Anaerobic Membrane Bioreactor (AnMBR) for the Removal of Dyes from Water and Wastewater: Progress, Challenges, and Future Perspectives

The presence of dyes in aquatic environments can have harmful effects on aquatic life, including inhibiting photosynthesis, decreasing dissolved oxygen levels, and altering the behavior and reproductive patterns of aquatic organisms. In the initial phase of this review study, our aim was to examine the categories and properties of dyes as well as the impact of their toxicity on aquatic environments. Azo, phthalocyanine, and xanthene are among the most frequently utilized dyes, almost 70–80% of used dyes, in industrial processes and have been identified as some of the most commonly occurring dyes in water bodies. Apart from that, the toxicity effects of dyes on aquatic ecosystems were discussed. Toxicity testing relies heavily on two key measures: the LC50 (half-lethal concentration) and EC50 (half-maximal effective concentration). In a recent study, microalgae exposed to Congo Red displayed a minimum EC50 of 4.8 mg/L, while fish exposed to Disperse Yellow 7 exhibited a minimum LC50 of 0.01 mg/L. Anaerobic membrane bioreactors (AnMBRs) are a promising method for removing dyes from water bodies. In the second stage of the study, the effectiveness of different AnMBRs in removing dyes was evaluated. Hybrid AnMBRs and AnMBRs with innovative designs have shown the capacity to eliminate dyes completely, reaching up to 100%. Proteobacteria, Firmicutes, and Bacteroidetes were found to be the dominant bacterial phyla in AnMBRs applied for dye treatment. However, fouling has been identified as a significant drawback of AnMBRs, and innovative designs and techniques are required to address this issue in the future.

A Comprehensive Review on Wastewater Nitrogen Removal and Its Recovery Processes

Discharging large amounts of domestic and industrial wastewater drastically increases the reactive nitrogen content in aquatic ecosystems, which causes severe ecological stress and biodiversity loss. This paper reviews three common types of denitrification processes, including physical, chemical, and biological processes, and mainly focuses on the membrane technology for nitrogen recovery. The applicable conditions and effects of various treatment methods, as well as the advantages, disadvantages, and influencing factors of membrane technologies, are summarized. Finally, it is proposed that developing effective combinations of different treatment methods and researching new processes with high efficiency, economy, and energy savings, such as microbial fuel cells and anaerobic osmotic membrane bioreactors, are the research and development directions of wastewater treatment processes.

Current research trends on emerging contaminants pharmaceutical and personal care products (PPCPs): A comprehensive review

Pharmaceutical and personnel care products (PPCPs) from wastewater are a potential hazard to the human health and wildlife, and their occurrence in wastewater has caught the concern of researchers recently. To deal with PPCPs, various treatment technologies have been evolved such as physical, biological, and chemical methods. Nevertheless, modern and efficient techniques such as advance oxidation processes (AOPs) demand expensive chemicals and energy, which ultimately leads to a high treatment cost. Therefore, integration of chemical techniques with biological processes has been recently suggested to decrease the expenses. Furthermore, combining ozonation with activated carbon (AC) can significantly enhance the removal efficiency. There are some other emerging technologies of lower operational cost like photo-Fenton method and solar radiation-based methods as well as constructed wetland, which are promising. However, feasibility and practicality in pilot-scale have not been estimated for most of these advanced treatment technologies. In this context, the present review work explores the treatment of emerging PPCPs in wastewater, via available conventional, non-conventional, and integrated technologies. Furthermore, this work focused on the state-of-art technologies via an extensive literature search, highlights the limitations and challenges of the prevailing commercial technologies. Finally, this work provides a brief discussion and offers future research directions on technologies needed for treatment of wastewater containing PPCPs, accompanied by techno-economic feasibility assessment.

Efficiency of Diclofenac Removal Using Activated Sludge in a Dynamic System (SBR Reactor) with Variable Parameters of pH, Concentration, and Sludge Oxygenation

Recently, traditional wastewater treatment systems have not been adapted to remove micropollutants, including pharmaceutical substances, which, even at low concentrations, cause adverse changes in aquatic and terrestrial living organisms. The problem of drug residues in the environment has been noticed; however, no universal legal regulations have been established for concentrations of these compounds in treated wastewater. Hence, the aim of the article was to determine the possibility of increasing the efficiency of diclofenac removal from activated sludge using the designed SBR reactor. This study included six cycles, working continuously, where each of them was characterized by changing conditions of pH, oxygenation, and composition of the synthetic medium. In each cycle, three concentrations of diclofenac were analyzed: 1 mg/L, 5 mg/L, 10 mg/L for the hydraulic retention time (HRT) of 4 d and the sludge retention time (SRT) of 12 d. The highest removal efficiency was achieved in the first test cycle for pH of natural sediment at the level of 6.7-7.0 (>97%), and in the third test cycle at pH stabilized at 6.5 (>87%). The reduced content of easily assimilable carbon from synthetic medium indicated a removal of >50%, which suggests that carbon in the structure of diclofenac restrained microorganisms to the rapid assimilation of this element. Under half-aerobic conditions, the drug removal effect for a concentration of 10 mg/L was slightly above 60%.

A critical review on retaining antibiotics in liquid digestate: Potential risk and removal technologies

Substantial levels of antibiotics remain in liquid digestate, posing a significant threat to human safety and the environment. A comprehensive assessment of residual antibiotics in liquid digestate and related removal technologies is required. To this end, this review first evaluates the potential risks of the residual antibiotics in liquid digestate by describing various anaerobic digestion processes and their half-lives in the environment. Next, emerging technologies for removing antibiotics in liquid digestate are summarized and discussed, including membrane separation, adsorption, and advanced oxidation processes. Finally, this study comprehensively and critically discusses these emerging technologies' prospects and challenges, including techno-economic feasibility and environmental impacts.

Biotransformation of 17β-Estradiol through a Denitrifying Sludge

17β-estradiol (E2) is the natural estrogen with the most significant potential for endocrine disruption in the biota of aquatic ecosystems at trace concentrations. It is, therefore, essential to study treatments for water polluted with E2 that would guarantee its complete elimination and mineralization. Denitrification is a biological process shown to have the capacity to completely biodegrade drugs, such as ampicillin. This work is aimed to evaluate the biotransformation of 17β-estradiol by employing a denitrifying sludge. The assays performed were: (I) abiotic with 3.5 mg E2-C L^-1 and (II) denitrifying with 10 mg CH₃COO^--C L^-1 as the reference, 10 mg E2-C L^-1 as the sole electron donor, and a mixture of (mg L^-1) 10 E2-C with 10 CH₃COO^--C at C N^-1 of 1.1. The E2-C and NO₃^--N consumption efficiencies were greater than 99%, and HCO₃^--C and N₂ production yields were close to 1 in all assays. The denitrifying sludge could biodegrade up to 10 mg E2-C L^-1 as the sole electron donor and when mixed with 10 mg CH₃COO^--C L^-1. No intermediate metabolites were generated from the process.

Anaerobic membrane bioreactors for pharmaceutical-laden wastewater treatment: A critical review

Pharmaceuticalsare a diverse group of chemical compounds widely used for prevention and treatment of infectious diseases in both humans and animals. Pharmaceuticals, either in their original or metabolite form, find way into the wastewater treatment plants (WWTPs) from different sources. Recently, anaerobic membrane bioreactors (AnMBR) has received significant research attention for the treatment of pharmaceuticals in various wastewater streams. This review critically examines the behaviour and removal of a wide array of pharmaceuticals in AnMBR with primary focus on their removal efficiencies and mechanisms, critical influencing factors, and the microbial community structures. Subsequently, the inhibitory effects of pharmaceuticals on the performance of AnMBR and membrane fouling are critically discussed. Furthermore, the imperative role of membrane biofouling layer and its components in pharmaceuticals removal is highlighted. Finally, recent advancements in AnMBR configurations for membrane fouling control and enhanced pharmaceuticals removal are systemically discussed.

Enhanced energy production and biological treatment of swine wastewater using anaerobic membrane bioreactor: Fouling mechanism and microbial community

This study aimed to reveal the membrane fouling mechanisms during anaerobic membrane bioreactor (AnMBR) operation for swine wastewater treatment under different organic loading rates (OLR). Results showed that AnMBR could achieve high pollutant removal (71.9-83.6 %) and energy recovery (0.18-0.23 L-CH₄/g-COD) at an OLR range of 0.25-0.5 g-COD/g-VSS.d, realizing energy production. However, higher OLR would aggravate the membrane fouling due to accumulation of fine sludge particles, organic foulants, and extracellular polymeric substances (EPS) on cake layer. Based on the high-throughput sequencing, microbial communities significantly changed and fouling-causing bacteria (e.g. Pseudomonas, Methanosarcina and Methanothrix) enriched in the cake layer at higher OLR conditions, leading to lower membrane permeability. Backwash can effectively remove the cake layer from the membrane surface and recover membrane permeability. The present study provides important information about membrane fouling and microbial information that could have significant impact on large-scale AnMBR application.

Bacteriophage cocktail as a promising bio-enhancer for methanogenic activities in anaerobic membrane bioreactors

This study aimed to explore the effect of a bacteriophage cocktail, pyophage, on the treatment of wastewater containing antibiotics in an anaerobic membrane bioreactor (AnMBR). During the operational period, performance of the AnMBR was monitored through the changes in chemical oxygen demand (COD), antibiotic removal, transmembrane pressure, and biogas production. Microbial community structure and composition, as well as the occurrence of antibiotic resistance genes were analyzed through shotgun metagenomics analysis. When exposed to pyophage, COD removal efficiency was enhanced up to 96%, whereas membrane fouling was delayed by 25%. Average biogas production was doubled from 224.2 mL/d in control with antibiotics to 447.3 mL/d when exposed to pyophage cocktail with considerable alterations to the archaeal and bacterial community structures. Most notably, the methanogenic community shifted from dominance of Methanothermobacter to Methanoculleus, along with syntrophic bacteria. The results provide insight into the synergistic effects of phage-bacteria and methanogenic communities and illustrate the potential of bacteriophages as bio-enhancers.

Sustainable Treatment Techniques for Emerging Pollutants—The Case of Personal Hygiene Products

Personal care products (PCPs) enter wastewater primarily through greywater. Treatment plants have not been able to remove this type of contaminant, although PCP abatement techniques have been developed in recent years. The objective of the current study has been to encounter the sustainable technique that keeps the optimal balance between the criteria considered in the comparison. Therefore, a bibliographic review was conducted in scientific databases of the last eight years, demonstrating that co-composting, anaerobic–aerobic sequencing bioreactors and contaminant absorption through the use of carbon nanotubes are the ones with the least environmental impact. Subsequently, the Saaty and Modified Saaty methods were applied, with a comparative criteria of construction costs, maintenance costs, efficiency and the stage of development. The results indicated that the co-composting technique is the best sustainable technique of those studied, with a score of 0.86/1, which means that the criteria analyzed maintain very close values between them. The co-composting technique yields a low environmental impact in eliminating personal care products. This research work constitutes a practical and easy-to-use tool for decision makers, since it allows finding an optimal elimination treatment for PCPs.

Augmentation characteristics and microbial community dynamics of low temperature resistant composite strains LTF-27

Biogas production in the cold regions of China is hindered by low temperatures, which led to slow lignocellulose biotransformation. Cold-adapted lignocellulose degrading microbial complex community LTF-27 was used to investigate the influence of hydrolysis on biogas production. After 5 days of hydrolysis at 15 ± 1 °C, the hydrolysis conversion rate of the corn straw went up to 22.64%, and the concentration of acetic acid increased to 2596.56 mg/L. The methane production rates of total solids (TS) inoculated by LTF-27 reached 204.72 mL/g, which was higher than the biogas (161.34 mL/g), and the control group (CK) inoculated with cultural solution (121.19 mL/g), the methane production rate of volatile solids (VS) increased by 26.88% and 68.92%, respectively. Parabacteroides, Lysinibacillus, and Citrobacter were the main organisms that were responsible for hydrolysis. While numerous other bacteria genera in the gas-producing phase, Macellibacteroides were the most commonly occurring one. Methanosarcina and Methanobacteriaceae contributed 86.25% and 11.80% of the total Archaea abundance during this phase. This study proves the psychrotrophic LTF-27's applicability in hydrolysis and biomass gas production in low temperatures.

Evaluation of membrane cake fouling mechanism to estimate design parameters of a submerged AnMBR treating high strength industrial wastewater

A mathematical model, which was previously developed for submerged aerobic membrane bioreactors, was successfully applied to elucidate the membrane cake-layer fouling mechanisms due to bound extracellular polymeric substances (eEPS) in a submerged anaerobic membrane bioreactor (SAnMBR). This biofouling dynamic model explains the mechanisms such as attachment, consolidation and detachment of eEPS produced in the bioreactor on the membrane surface. The 4th order Runge-Kutta method was used to solve the model equations, and the parameters were estimated from simulated and experimental results. The key design parameters representing the behaviour of cake fouling dynamics were systematically investigated. Organic loading rate (OLR) was considered a controlling factor governing the mixed liquor suspended solids (MLSS), eEPS production, filtration resistance (R_t), and transmembrane pressure (TMP) variations in a SAnMBR. eEPS showed a proportional relation with OLR at subsequent MLSS variations. The consolidation of EPS increased the specific eEPS resistance (α_s), influencing the cake resistance (R_c). The propensities of eEPS showed a positive correlation with R_t and TMP. The outcomes of the study also estimated a set of valuable design parameters which would be vital for applying in AnMBRs treating industrial wastewater.

Removal of Emerging Contaminants from Wastewater Streams Using Membrane Bioreactors: A Review

Water is a very valuable natural resource. As the demand for water increases the presence of emerging contaminants in wastewater has become a growing concern. This is particularly true when one considers direct reuse of wastewater. Obtaining sufficient removal of emerging contaminants will require determining the level of removal for the various unit operations in the wastewater treatment process. Membrane bioreactors are attractive as they combine an activated sludge process with a membrane separation step. They are frequently used in a wastewater treatment process and can operate at higher solid loadings than conventional activated sludge processes. Determining the level of removal of emerging contaminants in the membrane bioreactor step is, therefore, of great interest. Removal of emerging contaminants could be by adsorption onto the biomass or membrane surface, biotransformation, size exclusion by the membrane, or volatilization. Given the fact that most emerging contaminants are low molecule weight non-volatile compounds, the latter two methods of removal are usually unimportant. However, biotransformation and adsorption onto the biomass are important mechanisms of removal. It will be important to determine if the microorganisms present at given treatment facility are able to remove ECs present in the wastewater.

UV-filter pollution: current concerns and future prospects

UV-filters are widely used in cosmetics and personal care products to protect users' skin from redamage caused by ultraviolet (UV) radiation from the sun. Globally, an estimated 16,000 to 25,000 tonnes of products containing UV-filters were used in 2014 with modern consumption likely to be much higher. Beyond this use in cosmetics and personal care products, UV-filters are also widely used to provide UV-stability in industrial products such as paints and plastics. This review discusses the main routes by which UV-filters enter aquatic environments and summarises the conclusions of studies from the past 10 years that have investigated the effects of UV-filters on environmentally relevant species including corals, microalgae, fish, and marine mammals. Safety data regarding the potential impact of UV-filters on human health are also discussed. Finally, we explore the challenges surrounding UV-filter removal and research on more environmentally friendly alternatives to current UV-filters.

Bioaugmentation improves the anaerobic co-digestion of cadmium-containing plant residues and cow manure

Phytoremediation causes a large quantity of phytoremediation residues rich in heavy metals (HMs). This kind of plant residue can be used as a substrate for anaerobic digestion (AD) to reduce the content of HM-containing biomass, but high concentrations of HMs will inhibit the digestion efficiency and reduce the conversion efficiency of plant residues. Bioaugmentation may be an effective method to improve the degradation efficiency and methane yield of plant residues rich in HMs. In this study, a cellulose-degrading anaerobic bacteria Paracoccus sp. Termed strain LZ-G1 was isolated from cow dung, which can degrade cellulose and simultaneously adsorb Cd²⁺. The Cd²⁺ (10 mg/L)-adsorbtion efficiency and cellulose (463.12 g/kg)-degradation rate were 65.1 % and 60.59 %, respectively. In addition, using the strain LZ-G1 bioaugmented Cd²⁺-containing plant residues and cow manure mixed AD system, the system's biogas and methane production significantly increased (98.97 % and 142.03 %, respectively). During the AD process, the strain LZ-G1 was successfully colonized in the digestion system. Furthermore, the microbial community analysis revealed that LZ-G1 bioaugmentation alleviates the toxicity of free Cd²⁺ to the microbial community in the AD system, regulates and restores the archaea genus dominant in the methanogenesis stage, and restores the relative abundance of dominant bacteria associated with biomass hydrolysis. The restoration of the microbial community increased the biogas yield and methane production rate. Thus, bioaugmentation provides an easy and a feasible method for the actual on-site treatment of HM-rich phytoremediation residues.

Antibiotic transformation in an anaerobic membrane bioreactor linked to membrane biofilm microbial activity

Although extensive research to date has focused on enhancing removal rates of antibiotics from municipal wastewaters, the transformation products formed by anaerobic treatment processes remain understudied. The present work aims to examine the possible roles that the different microbial communities of an anaerobic membrane bioreactor (AnMBR) play in the transformation of antibiotics during wastewater treatment. As part of this work, sulfamethoxazole, erythromycin, and ampicillin were added in separate stages to the influent of the AnMBR at incremental concentrations of 10, 50, and 250 μg/L each. Antibiotic-specific transformation products detected during each stage, as identified by high resolution LC-MS, are reported herein. Results suggest that both isoxazole (sulfamethoxazole) and β-lactam (ampicillin) ring opening could be facilitated by the AnMBR's bioprocess. Microbial community analysis results indicated that relative activity of the system's suspended biomass consistently shifted towards syntrophic groups throughout the duration of the experiment. Notable differences were also observed between the suspended biomass and the AnMBR's membrane biofilms. Membrane-attached biofilm communities showed high relative activities of several specific methanogenic (Methanothrix and Methanomethylovorans), syntrophic (Syntrophaceae), and sulfate-reducing (Desulfomonile) groups. Such groups have been previously identified as involved in the formation of the antibiotic degradation products observed in the effluent of the AnMBR. The activity of these communities within the biofilms likely confers certain advantages that aid in the biotransformation of the antibiotics tested.

Construction of biotreatment platforms for aromatic hydrocarbons and their future perspectives

Aromatic hydrocarbons (AHCs) are one of the major environmental pollutants introduced from both natural and anthropogenic sources. Many AHCs are well known for their toxic, carcinogenic, and mutagenic impact on human health and ecological systems. Biodegradation is an eco-friendly and cost-effective option as microorganisms (e.g., bacteria, fungi, and algae) can efficiently breakdown or transform such pollutants into less harmful and simple metabolites (e.g., carbon dioxide (aerobic), methane (anaerobic), water, and inorganic salts). This paper is organized to offer a state-of-the-art review on the biodegradation of AHCs (monocyclic aromatic hydrocarbons (MAHs) and polycyclic aromatic hydrocarbons (PAHs)) and associated mechanisms. The recent progress in biological treatment using suspended and attached growth bioreactors for the biodegradation of AHCs is also discussed. In addition, various substrate growth and inhibition models are introduced along with the key factors governing their biodegradation kinetics. The growth and inhibition models have helped gain a better understanding of substrate inhibition in biodegradation. Techno-economic analysis (TEA) and life cycle assessment (LCA) aspects are also described to assess the technical, economical, and environmental impacts of the biological treatment system.

Recent developments in physical, biological, chemical, and hybrid treatment techniques for removing emerging contaminants from wastewater

Emerging contaminants (ECs) in wastewater have recently attracted the attention of researchers as they pose significant risks to human health and wildlife. This paper presents the state-of-art technologies used to remove ECs from wastewater through a comprehensive review. It also highlights the challenges faced by existing EC removal technologies in wastewater treatment plants and provides future research directions. Many treatment technologies like biological, chemical, and physical approaches have been advanced for removing various ECs. However, currently, no individual technology can effectively remove ECs, whereas hybrid systems have often been found to be more efficient. A hybrid technique of ozonation accompanied by activated carbon was found significantly effective in removing some ECs, particularly pharmaceuticals and pesticides. Despite the lack of extensive research, nanotechnology may be a promising approach as nanomaterial incorporated technologies have shown potential in removing different contaminants from wastewater. Nevertheless, most existing technologies are highly energy and resource-intensive as well as costly to maintain and operate. Besides, most proposed advanced treatment technologies are yet to be evaluated for large-scale practicality. Complemented with techno-economic feasibility studies of the treatment techniques, comprehensive research and development are therefore necessary to achieve a full and effective removal of ECs by wastewater treatment plants.

Addition of Trichocladium canadense to an anaerobic membrane bioreactor: evaluation of the microbial composition and reactor performance

Membrane bioreactors are powerful systems for wastewater treatment and the removal of toxic compounds. However, membrane biofouling stands in the way of their widespread usage. In this study, the saprophytic fungus Trichocladium canadense was used as the bioaugmentor in an anaerobic membrane bioreactor (AnMBR) and its impact on membrane biofouling, biogas production, the microbial communities of the reactor and removal of the common antibiotics erythromycin (ERY), sulfamethoxazole (SMX) and tetracycline (TET) from synthetic wastewater was investigated. The results indicated that through bioaugmentation with 20% T. canadense, membrane biofouling was slowed by 25%, the chemical oxygen demand removal increased by 16% and a higher efficiency removal of ERY and SMX was achieved. The presence of T. canadense significantly increased the abundance and diversity of the biofilm archaeal community and the bacterial phylum Firmicutes, a known bio-foulant.

Anaerobic membrane bioreactors for wastewater treatment: Challenges and opportunities

Anaerobic membrane bioreactors (AnMBRs) have become a new mature technology and entered into the wastewater market, but there are several challenges to be addressed for wide applications. In this review, we discuss challenges and potentials of AnMBRs focusing on wastewater treatment. Nitrogen and dissolved methane control, membrane fouling and its control, and membrane associated cost including energy consumption are main bottlenecks to facilitating AnMBR application in wastewater treatment. Accumulation of dissolved methane in AnMBR permeate decreases the benefit of methane energy and contributes to methane gas emissions to atmosphere. Separate control units for nitrogen and dissolved methane add system complexity and increase capital and operating and maintenance (O & M) costs in AnMBR-centered wastewater treatment. Alternatively, methane-based denitrification can be an ideal nitrogen control process due to simultaneous removal of nitrogen and dissolved methane. Membrane fouling and energy associated with membrane fouling control are major limitations, in addition to membrane cost. More efforts are required to decrease capital and O & M costs associated with the control of dissolved methane nitrogen and membrane fouling to facilitate AnMBRs for wastewater treatment. PRACTITIONER POINTS: AnMBRs can accelerate anaerobic wastewater treatment including dilute wastewater. Nitrogen and dissolved methane control is detrimental for AnMBR application to wastewater treatment. Membrane biofilm reactors using gas-permeable membranes are suitable for simultaneous nitrogen and dissolved methane control. High capital and O & M costs from membranes are a major bottleneck to wide application of AnMBRs. Dynamic membranes could be an option to reduce capital and O & M costs for AnMBRs.

Comparative overview of advanced oxidation processes and biological approaches for the removal pharmaceuticals

Nowadays, pharmaceuticals are the center of significant environmental research due to their complex and highly stable bioactivity, increasing concentration in the water streams and high persistence in aquatic environments. Conventional wastewater treatment techniques are generally inadequate to remove these pollutants. Aiming to tackle this issue effectively, various methods have been developed and investigated on the light of chemical, physical and biological procedures. Increasing attention has recently been paid to the advanced oxidation processes (AOPs) as efficient methods for the complete mineralization of pharmaceuticals. Their high operating costs compared to other processes, however, remain a challenge. Hence, this review summarizes the current and state of art related to AOPs, biological treatment and their effective exploitation for the degradation of various pharmaceuticals and other emerging molecules present in wastewater. The review covers the last decade with a particular focus on the previous five years. It is further envisioned that this review of advanced oxidation methods and biological treatments, discussed herein, will help readers to better understand the mechanisms and limitations of these methods for the removal of pharmaceuticals from the environment. In addition, we compared AOPs and biological treatments for the disposal of pharmaceuticals from the point of view of cost, effectiveness, and popularity of their use. The exploitation of coupling AOPs and biological procedures for the degradation of pharmaceuticals in wastewater was also presented. It is worthy of note that an integrated AOPs/biological system is essential to reach the complete degradation of pharmaceuticals; other advantages of this hybrid technique involve low energy cost, an efficient degradation process and generation of non-toxic by-products.

Occurrence, influence and removal strategies of mycotoxins, antibiotics and microplastics in anaerobic digestion treating food waste and co-digestive biosolids: A critical review

Food waste anaerobic digestion (FWAD) can be assisted with the co-digestion of manures, agricultural waste, and sewage sludge. Nevertheless, contaminants like mycotoxins, antibiotics, and microplastics (MPs) could be introduced and negatively affect the AD system. Over 180 literatures involved the occurrence, influence and removal strategies of these three types of pollutants in AD were summarized in this review. Aflatoxin B1(AFB1) as the most concerned mycotoxins were poorly degraded and brought about inhibitions in short-term. Considering methanogenesis inhibition and occurrence concentration, the risk of oxytetracycline and norfloxacin were identified as priority among antibiotics. Leaching toxic additives from MPs could be responsible for the AD inhibition, while their materials and sizes could also prolong the acidification and methanation processes in FWAD. Strategies of bioaugmentation technologies and bioreactors to enhance the removal were suggested. Perspectives were provided for a better understanding of the fates of reviewed contaminants and their elimination in FWAD systems.

Potential Environmental and Human Health Risks Caused by Antibiotic-Resistant Bacteria (ARB), Antibiotic Resistance Genes (ARGs) and Emerging Contaminants (ECs) from Municipal Solid Waste (MSW) Landfill

The disposal of municipal solid waste (MSW) directly at landfills or open dump areas, without segregation and treatment, is a significant concern due to its hazardous contents of antibiotic-resistant bacteria (ARB), antibiotic resistance genes (ARGs), and metal resistance genes (MGEs). The released leachate from landfills greatly effects the soil physicochemical, biological, and groundwater properties associated with agricultural activity and human health. The abundance of ARB, ARGs, and MGEs have been reported worldwide, including MSW landfill sites, animal husbandry, wastewater, groundwater, soil, and aerosol. This review elucidates the occurrence and abundance of ARB, ARGs, and MRGs, which are regarded as emerging contaminants (ECs). Recently, ECs have received global attention because of their prevalence in leachate as a substantial threat to environmental and public health, including an economic burden for developing nations. The present review exclusively discusses the demands to develop a novel eco-friendly management strategy to combat these global issues. This review also gives an intrinsic discussion about the insights of different aspects of environmental and public health concerns caused due to massive leachate generation, the abundance of antibiotics resistance (AR), and the effects of released leachate on the various environmental reservoirs and human health. Furthermore, the current review throws light on the source and fate of different ECs of landfill leachate and their possible impact on the nearby environments (groundwater, surface water, and soil) affecting human health. The present review strongly suggests the demand for future research focuses on the advancement of the removal efficiency of contaminants with the improvement of relevant landfill management to reduce the potential effects of disposable waste. We propose the necessity of the identification and monitoring of potential environmental and human health risks associated with landfill leachate contaminants.

Occurrence and Fate of Emerging Pollutants in Water Environment and Options for Their Removal

Emerging pollutants (EPs) are chemicals known to cause major impacts on the terrestrial, aquatic life and human health as a result of their chronic and acute toxicity. Although lots of studies on EPs behavior in the aquatic environment are currently available in literature, an urgent requirement exists to complete toxicological studies and develop and implement efficient and ecological methods for their removal. This paper raises some relevant problems related to water environment pollution with EPs, the risks they can generate for aquatic life and humans and opportunities to reduce the effects of pollution by EPs removal. Categories of emerging chemicals of concern in the environment, their sources, fate and impacts, with some examples are discussed. Organic UV filters are shortly presented as a relative new EPs category, with a focus on the need to develop extensive experimental studies on their environmental occurrence, fate and removal. Furthermore, sources for the aquatic environment resulting from discharging EPs directly into rivers from wastewater treatment plants are examined. The incidence of environmental and human health risks related to EPs is also considered. The removal of EPs from the environment as a solution to risk mitigation is addressed, with emphasis on several non-conventional processes involving biological removal of EPs. The paper provides a critical look at the current challenges posed by the presence of emerging pollutants in the aquatic environment, with critical comments and recommendations for further research to reduce the impact of EPs on water and human health and improve the performance of developed methods for their removal.