Tracking Cryptosporidium in urban wastewater treatment plants in a cold region: Occurrence,species and infectivity

• Cryptosporidium in WWTPs in a cold region was investigated in different seasons. • The overall removal efficiency of Cryptosporidium in WWTPs was over 84%. • The infectivity rate declined below 53% in effluents mainly due to disinfection. • The infectivity of Cryptosporidium increased with a seasonal drop in temperature. • Low temperature promotes binding protein retention and virulence genes expression. This study investigated the occurrence, species, infectivity and removal efficiency of Cryptosporidium spp. across typical wastewater treatment train. Samples from different process units were collected seasonally and synchronously from four wastewater treatment plants (WWTPs) in Northeastern China. Live Cryptosporidium oocysts were identified in most samples from both influent (97.50%) and effluent (90.00%) wastewaters of the four WWTPs, at an average density of 26.34 and 4.15 oocysts/L, respectively. The overall removal efficiency was 84.25%, and oocysts were mainly removed (62.01%) by the modified secondary sedimentation process. Ten Cryptosporidium species were identified in the effluent samples. C. andersoni, C. bovis, and C. ryanae were the three most prevalent species. Oocyst viability assays indicated no reduction of excystation rate during the primary and secondary wastewater treatments (varied in the range of 63.08%–68.50%), but the excystation rate declined to 52.21% in the effluent after disinfection. Notably, the Cryptosporidium oocysts showed higher infection intensity in the cold season (winter and spring) than that in summer and autumn. The influences of environmental temperature on virulence factors of Cryptosporidium were further examined. It was observed that more extracellular secretory proteins were bound on the oocyst surface and several virulence genes were expressed relatively strongly at low temperatures, both of which could facilitate oocyst adhesion, invasion, and host immune evasion. This research is of considerable interest since it serves as an important step towards more accurate panoramic recognition of Cryptosporidium risk reduction in WWTPs, and especially highlights the potential health risk associated with Cryptosporidium in cold regions/seasons.     

Distribution of antibiotic resistance genes and their association with bacteria and viruses in decentralized sewage treatment facilities

• Distribution of ARGs in decentralized sewage facilities were investigated. • Bacitracin-ARGs were most predominant ARGs in rural wastewater. • ARGs were identified in bacterial and viral community. • ARGs of rpoB, drfE, gyrA and parC were both correlated with bacteria and phages. • More attention should be paid to the risk of spreading ARG by phages. The distribution of antibiotic resistance genes (ARGs) has been intensively studied in large-scale wastewater treatment plants and livestock sources. However, small-scale decentralized sewage treatment facilities must also be explored due to their possible direct exposure to residents. In this study, six wastewater treatment facilities in developed rural areas in eastern China were investigated to understand their risks of spreading ARGs. Using metagenomics and network analysis tools, ARGs and bacterial and viral communities were identified in the influent (INF) and effluent (EFF) samples. The dominant ARGs belonged to the bacitracin class, which are different from most of municipal wastewater treatment plants (WWTPs). The dominant hosts of ARGs are Acidovorax in bacterial communities and Prymnesiovirus in viral communities. Furthermore, a positive relationship was found between ARGs and phages. The ARGs significantly correlated with phages were all hosted by specific genera of bacteria, indicating that phages had contributed to the ARG’s proliferation in sewage treatment facilities. Paying significant concern on the possible enhanced risks caused by bacteria, viruses and their related ARGs in decentralized sewage treatment facilities is necessary.     

Diffusive gradients in thin films using molecularly imprinted polymer binding gels for in situ measurements of antibiotics in urban wastewaters

• Selective molecularly imprinted polymer (MIP) binding gel was prepared. • MIP-DGT showed excellent uptake performance for antibiotics. • In situ measurement of antibiotics in wastewaters via MIP-DGT was developed. • The MIP-DGT method was robust, reliable, and highly sensitive. Urban wastewater is one of main sources for the introduction of antibiotics into the environment. Monitoring the concentrations of antibiotics in wastewater is necessary for estimating the amount of antibiotics discharged into the environment through urban wastewater treatment systems. In this study, we report a novel diffusive gradient in thin films (DGT) method based on molecularly imprinted polymers (MIPs) for in situ measurement of two typical antibiotics, fluoroquinolones (FQs) and sulfonamides (SAs) in urban wastewater. MIPs show specific adsorption toward their templates and their structural analogs, resulting in the selective uptake of the two target antibiotics during MIP-DGT deployment. The uptake performance of the MIP-DGTs was evaluated in the laboratory and was relatively independent of solution pH (4.0–9.0), ionic strength (1–750 mmol/L), and dissolved organic matter (DOM, 0–20 mg/L). MIP-DGT samplers were tested in the effluent of an urban wastewater treatment plant for field trials, where three SA (sulfamethoxazole, sulfapyridine, and trimethoprim) and one FQ (ofloxacin) antibiotics were detected, with concentrations ranging from 25.50 to 117.58 ng/L, which are consistent with the results measured by grab sampling. The total removal efficiency of the antibiotics was 80.1% by the treatment plant. This study demonstrates that MIP-DGT is an effective tool for in situ monitoring of trace antibiotics in complex urban wastewaters.     

Energy neutrality potential of wastewater treatment plants: A novel evaluation framework integrating energy efficiency and recovery

• Framework of indicators was established based on energy efficiency and recovery. • Energy neutrality potential of 970 wastewater treatment plants was evaluated. • Analysis of characteristics and explanatory factors was carried out. • Pathways for improving the energy neutrality potential were proposed. Wastewater treatment plants (WWTPs) consume large amounts of energy and emit greenhouse gases to remove pollutants. This study proposes a framework for evaluating the energy neutrality potential (ENP) of WWTPs from an integrated perspective. Operational data of 970 WWTPs in the Yangtze River Economic Belt (YREB) were extracted from the China Urban Drainage Yearbook 2018. The potential chemical and thermal energies were estimated using combined heat and power (CHP) and water source heat pump, respectively. Two key performance indicators (KPIs) were then established: the energy self-sufficiency (ESS) indicator, which reflects the offset degree of energy recovery, and the comprehensive water–energy efficiency (CWEE) indicator, which characterizes the efficiency of water–energy conversion. For the qualitative results, 98 WWTPs became the benchmark (i.e., CWEE= 1.000), while 112 WWTPs were fully self-sufficient (i.e., ESS≥100%). Subsequently, four types of ENP were classified by setting the median values of the two KPIs as the critical value. The WWTPs with high ENP had high net thermal energy values and relatively loose discharge limits. The explanatory factor analysis of water quantity and quality verified the existence of scale economies. Sufficient carbon source and biodegradability condition were also significant factors. As the CWEE indicator was mostly sensitive to the input of CHP, future optimization shall focus on the moisture and organic content of sludge. This study proposes a novel framework for evaluating the ENP of WWTPs. The results can provide guidance for optimizing the energy efficiency and recovery of WWTPs.     

What have we known so far for fluorescence staining and quantification of microplastics: A tutorial review

• Fluorescence staining provides a fast and easy method to quantify microplastics. • Factors that influence staining are summarized to obtain an optimum staining effect. • Natural organic matter can be stained by dye and interfere with quantification. • Fluorescence staining is applied in both field and laboratory studies. • Future work involves developing new dyes and automated image-analysis methods. Understanding the fate and toxicity of microplastics (MPs,<5 mm plastic particles) is limited by quantification methods. This paper summarizes the methods in use and presents new ones. First, sampling and pretreatment processes of MPs, including sample collection, digestion, density separation, and quality control are reviewed. Then the promising and convenient staining procedures and quantification methods for MPs using fluorescence dyes are reviewed. The factors that influence the staining of MPs, including their physicochemical properties, are summarized to provide an optimal operation procedure. In general, the digestion step is crucial to eliminate natural organic matter (NOM) to avoid interference in quantification. Chloroform was reported to be the most appropriate solvent, and 10–20 μg/mL are recommended as optimal dye concentrations. In addition, a heating and cooling procedure is recommended to maintain the fluorescence intensity of MPs for two months. After staining, a fluorescence microscope is usually used to characterize the morphology, mass, or number of MPs, but compositional analysis cannot be determined with it. These fluorescence staining methods have been implemented to study MP abundance, transport, and toxicity and have been combined with other chemical characterization techniques, such as Fourier transform infrared spectroscopy and Raman spectroscopy. More studies are needed to focus on the synthesis of novel dyes to avoid NOM’s interference. They need to be combined with other spectroscopic techniques to characterize plastic composition and to develop image-analysis methods. The stability of stained MPs needs to be improved.     

Research progress on distribution,sources, identification,toxicity, and biodegradation of microplastics in the ocean,freshwater, and soil environment

• Microplastics are widely found in both aquatic and terrestrial environments. • Cleaning products and discarded plastic waste are primary sources of microplastics. • Microplastics have apparent toxic effects on the growth of fish and soil plants. • Multiple strains of biodegradable microplastics have been isolated. Microplastics (MPs) are distributed in the oceans, freshwater, and soil environment and have become major pollutants. MPs are generally referred to as plastic particles less than 5 mm in diameter. They consist of primary microplastics synthesized in microscopic size manufactured production and secondary microplastics generated by physical and environmental degradation. Plastic particles are long-lived pollutants that are highly resistant to environmental degradation. In this review, the distribution and possible sources of MPs in aquatic and terrestrial environments are described. Moreover, the adverse effects of MPs on natural creatures due to ingestion have been discussed. We also have summarized identification methods based on MPs particle size and chemical bond. To control the pollution of MPs, the biodegradation of MPs under the action of different microbes has also been reviewed in this work. This review will contribute to a better understanding of MPs pollution in the environment, as well as their identification, toxicity, and biodegradation in the ocean, freshwater, and soil, and the assessment and control of microplastics exposure.     

Composition,dispersion, and health risks of bioaerosols in wastewater treatment plants: A review

• Bioaerosols are produced in the process of wastewater biological treatment. • The concentration of bioaerosol indoor is higher than outdoor. • Bioaerosols contain large amounts of potentially pathogenic biomass and chemicals. • Inhalation is the main route of exposure of bioaerosol. • Both the workers and the surrounding residents will be affected by the bioaerosol. Bioaerosols are defined as airborne particles (0.05–100 mm in size) of biological origin. They are considered potentially harmful to human health as they can contain pathogens such as bacteria, fungi, and viruses. This review summarizes the most recent research on the health risks of bioaerosols emitted from wastewater treatment plants (WWTPs) in order to improve the control of such bioaerosols. The concentration and size distribution of WWTP bioaerosols; their major emission sources, composition, and health risks; and considerations for future research are discussed. The major themes and findings in the literature are as follows: the major emission sources of WWTP bioaerosols include screen rooms, sludge-dewatering rooms, and aeration tanks; the bioaerosol concentrations in screen and sludge-dewatering rooms are higher than those outdoors. WWTP bioaerosols contain a variety of potentially pathogenic bacteria, fungi, antibiotic resistance genes, viruses, endotoxins, and toxic metal(loid)s. These potentially pathogenic substances spread with the bioaerosols, thereby posing health risks to workers and residents in and around the WWTP. Inhalation has been identified as the main exposure route, and children are at a higher risk of this than adults. Future studies should identify emerging contaminants, establish health risk assessments, and develop prevention and control systems.     

Microplastics removal strategies: A step toward finding the solution

• Physical, chemical and biological methods are explored for MPs removal. • Physical methods based on adsorption/filtration are mostly used for MPs removal. • Chemical methods of MPs removal work on coagulation and flocculation mechanism. • MBR technology has also shown the removal of MPs from water. • Global policy on plastic control is lacking. Microplastics are an emerging threat and a big challenge for the environment. The presence of microplastics (MPs) in water is life-threatening to diverse organisms of aquatic ecosystems. Hence, the scientific community is exploring deeper to find treatment and removal options of MPs. Various physical, chemical and biological methods are researched for MPs removal, among which few have shown good efficiency in the laboratory. These methods also have a few limitations in environmental conditions. Other than finding a suitable method, the creation of legal restrictions at a governmental level by imposing policies against MPs is still a daunting task in many countries. This review is an effort to place all effectual MP removal methods in one document to compare the mechanisms, efficiency, advantages, and disadvantages and find the best solution. Further, it also discusses the policies and regulations available in different countries to design an effective global policy. Efforts are also made to discuss the research gaps, recent advancements, and insights in the field.     

Characterization and seasonal distribution of microplastics in the nearshore sediments of the south-east coast of India,Bay of Bengal

• MPs in the coastal sediment of south-east coast of India are quantified. • High MPs are recorded near river mouths and nearshore regions. • Polyethylene and polypropylene are the major polymers observed. • MPs contamination is higher than the values reported elsewhere. In view of increasing Microplastics (MPs) contamination in the marine environment and dearth of baseline data, a study was conducted on the abundance, characterization, and seasonal distribution of MPs in the nearshore sediments of the south-east coast of India. Sediment samples (n = 130) were collected at a distance of 1 km and 10 km from the shore region at varying depths (8–45 m) along the Chennai to Puducherry coast (165 km stretch), representing two seasons, i.e., south-west (July 2019 and July 2020) and north-east (January 2020) monsoons. The average abundance of MPs at the 22 offshore sites along the Chennai to Puducherry coast varied from 9±4.3 to 19±12.9 particles/50 g dry weight, in July 2019 and January 2020, respectively. July 2020 had an average abundance of 10±4.5 particles/50 g dry weight. Spatially, high levels of MPs were found at 1km stations and transects in proximity to the river inlets, and temporally, the north-east month recorded the maximum concentration. The dominant morphotype was the filament, and the major polymers were polyethylene and polypropylene. Scanning Electron Microscope (SEM) images revealed the surface irregularity and degradation of MPs due to weathering. The study highlights that high sediment contamination by MPs occurs during heavy rainfall and accumulates closer to river inlets. Eventually, this study suggests that appropriate management of plastic wastes on the landside will reduce MP contamination in the marine environment.     

Fate of microplastics in a coastal wastewater treatment plant: Microfibers could partially break through the integrated membrane system

• Fate of microplastics in integrated membrane system for water reuse was investigated. • Integrated membrane system has high removal efficiency (>98%) for microplastics. • Microplastics (>93%) were mainly removed through membrane bioreactor treatment. • Small scale fiber plastics (<200 μm) could break through reverse osmosis (RO) system. • The flux of microplastics maintained at 2.7 × 10¹¹ MPs/d after the RO treatment. Rare information on the fate of microplastics in the integrated membrane system (IMS) system in full-scale wastewater treatment plant was available. The fate of microplastics in IMS in a coastal reclaimed water plant was investigated. The removal rate of microplastics in the IMS system reached 93.2% after membrane bioreactor (MBR) treatment while that further increased to 98.0% after the reverse osmosis (RO) membrane process. The flux of microplastics in MBR effluent was reduced from 1.5 × 10¹³ MPs/d to 10.2 × 10¹¹ MPs/d while that of the RO treatment decreased to 2.7 × 10¹¹ MPs/d. Small scale fiber plastics (<200 μm) could break through RO system according to the size distribution analysis. The application of the IMS system in the reclaimed water plant could prevent most of the microplastics from being discharged in the coastal water. These findings suggested that the IMS system was more efficient than conventional activated sludge system (CAS) for the removal of microplastics, while the discharge of small scale fiber plastics through the IMS system should also not be neglected because small scale fiber plastics (<200 μm) could break through IMS system equipped with the RO system.     

The abundance,characteristics and diversity of microplastics in the South China Sea: Observation around three remote islands

• A high abundance of floating MPs was found in the southern South China Sea. • Transparent film and fiber were predominant in water and organisms, respectively. • 84.7% of floating MPs and 54.5% of MPs in vivo belonged to PP and PE. • Characteristics of MP in organisms were different from those of inshore ones. Surrounded by emerging markets with considerable plastic consumption, the South China Sea has been a focus area of microplastic research. A survey on the floating microplastics (>0.3 mm) and microplastics ingested by fish and mollusks was conducted around three remote islands here. Compared with the results from several previous studies, a high abundance of floating microplastics (with a median of 1.9 × 10⁵ items/km² or 0.7 items/m³) was observed, revealing another “hot spot” for microplastics. Polyolefin, especially polypropylene, was the main component. The diversity index and evenness index were calculated and evaluated based on the composition of microplastics. The characteristic peaks of Raman spectra concerning pigmented microplastics were provided. Transparent sheets/films were predominant in the water sample, which was quite different from a similar study in this sea area (8.9% for film), and only 16.4% of floating microplastics (>0.3 mm) were fibers/lines, implying that the main sources of floating microplastics (>0.3 mm) might be household/agricultural consumption activities. The transparent fiber/line was also dominant in organisms. It is suggested that the main sources of microplastics ingested by organisms might be both fabric fibers and fishing/aquaculture.     

Overlooked nitrogen-cycling microorganisms in biological wastewater treatment

• AOA and comammox bacteria can be more abundant and active than AOB/NOB at WWTPs. • Coupled DNRA/anammox and NO_x-DAMO/anammox/comammox processes are demonstrated. • Substrate level, SRT and stressors determine the niches of overlooked microbes. • Applications of overlooked microbes in enhancing nitrogen removal are promising. Nitrogen-cycling microorganisms play key roles at the intersection of microbiology and wastewater engineering. In addition to the well-studied ammonia oxidizing bacteria, nitrite oxidizing bacteria, heterotrophic denitrifiers, and anammox bacteria, there are some other N-cycling microorganisms that are less abundant but functionally important in wastewater nitrogen removal. These microbes include, but not limited to ammonia oxidizing archaea (AOA), complete ammonia oxidation (comammox) bacteria, dissimilatory nitrate reduction to ammonia (DNRA) bacteria, and nitrate/nitrite-dependent anaerobic methane oxidizing (NO_x-DAMO) microorganisms. In the past decade, the development of high-throughput molecular technologies has enabled the detection, quantification, and characterization of these minor populations. The aim of this review is therefore to synthesize the current knowledge on the distribution, ecological niche, and kinetic properties of these “overlooked” N-cycling microbes at wastewater treatment plants. Their potential applications in novel wastewater nitrogen removal processes are also discussed. A comprehensive understanding of these overlooked N-cycling microbes from microbiology, ecology, and engineering perspectives will facilitate the design and operation of more efficient and sustainable biological nitrogen removal processes.     

Less attention paid to waterborne SARS-CoV-2 spreading in Beijing urban communities

• A survey on individual’s perception of SARS-CoV-2 transmission was conducted. • Waterborne transmission risks are far less perceived by individuals. • Precautions of preventing wastewater mediated transmission are implemented. • The precautions for wastewater transmission are less favored by the public. • Education level differs the most regarding to waterborne transmission perception. SARS-CoV-2 has been detected in various environmental media. Community and individual-engaged precautions are recommended to stop or slow environmentally-mediated transmission. To better understand the individual’s awareness of and precaution to environmental dissemination of SARS-CoV-2, an online survey was conducted in Beijing during March 14–25, 2020. It is found that the waterborne (especially wastewater mediated) spreading routes are far less perceived by urban communities. The precautions for wastewater transmission are less favored by the public than airborne and solid waste mediated spreading routes. Such risk communication asymmetry in waterborne transmission will be further enlarged in places with fragile water system. Furthermore, education level is the most significant attribution (Sig.<0.05) that causes the difference of awareness and precautions of the waterborne transmission among the respondents, according to the variance analysis results. Our survey results emphasize the urgent need for evidence-based, multifactorial precautions for current and future outbreaks of COVID-19.     

Effects of hydraulic retention time on net present value and performance in a membrane bioreactor treating antibiotic production wastewater

• The membrane bioreactor cost decreased by 38.2% by decreasing HRT from 72 h to 36 h. • Capital and operation costs contributed 62.1% and 37.9% to decreased costs. • The membrane bioreactor is 32.6% cheaper than the oxidation ditch for treatment. • The effluent COD also improved from 709.93±62.75 mg/L to 280±17.32 mg/L. • Further treatment also benefited from lower pretreatment investment. A cost sensitivity analysis was performed for an industrial membrane bioreactor to quantify the effects of hydraulic retention times and related operational parameters on cost. Different hydraulic retention times (72–24 h) were subjected to a flat-sheet membrane bioreactor updated from an existing 72 h oxidation ditch treating antibiotic production wastewater. Field experimental data from the membrane bioreactor, both full-scale (500 m³/d) and pilot (1.0 m³/d), were used to calculate the net present value (NPV), incorporating both capital expenditure (CAPEX) and operating expenditure. The results showed that the tank cost was estimated above membrane cost in the membrane bioreactor. The decreased hydraulic retention time from 72 to 36 h reduced the NPV by 38.2%, where capital expenditure contributed 24.2% more than operational expenditure. Tank construction cost was decisive in determining the net present value contributed 62.1% to the capital expenditure. The membrane bioreactor has the advantage of a longer lifespan flat-sheet membrane, while flux decline was tolerable. The antibiotics decreased to 1.87±0.33 mg/L in the MBR effluent. The upgrade to the membrane bioreactor also benefited further treatments by 10.1%–44.7% lower direct investment.     

Occurrence and fate of typical antibiotics in wastewater treatment plants in Harbin,North-east China

• The concentration distributions and removals of 12 antibiotics were investigated. • Macrolides and fluoroquinolones presented relatively higher concentrations. • The removal of antibiotics did not differ among the different treatment processes. As a new pollutant, antibiotics in the environment and their removal in wastewater treatment plants (WWTPs) have gained considerable attention. However, few studies investigated antibiotics in the north-eastern areas of China. By employing high-performance liquid chromatography-tandem mass spectrometry, the concentration distribution and removal of 12 antibiotics belonging to four types (cephalosporins, sulfonamides, fluoroquinolones, and macrolides) were investigated in influents and effluents as well as the removal efficiencies of four typical treatment processes in 18 wastewater treatment plants of Harbin City, north-eastern China. Macrolides and fluoroquinolones presented relatively higher detection concentrations and rates both in the water and in the sludge phases. Sulfonamides and cephalosporins displayed higher detection concentrations in the water phase. The representative antibiotics in influents and effluents included ROX, NOR, OFL, SMX, AZI, and CLA, with detection rates above 95%. The detection rates of the other six antibiotics exceeded 30%. In the sludge, the other five antibiotics, except SMX, presented relatively higher detection concentrations and rates, with detection rates greater than 95%. For cephalosporin, the detection rates of CTX and CFM in the sludge were 0. The removal efficiencies for the 12 antibiotics differed greatly, with average values ranging from 30% to 80% and the highest values for cephalosporin. The removal of antibiotics did not differ significantly among the four different treatment processes.     

Development of combined coagulation-hydrolysis acidification-dynamic membrane bioreactor system for treatment of oilfield polymer-flooding wastewater

• We created a combined system for treating oilfield polymer-flooding wastewater. • The system was composed of coagulation, hydrolysis acidification and DMBR. • Coagulant integrated with demulsifier dominated the removal of crude oil. • The DMBR proceed efficiently without serious membrane fouling. A combined system composed of coagulation, hydrolysis acidification and dynamic membrane bioreactor (DMBR) was developed for treating the wastewater produced from polymer flooding. Performance and mechanism of the combined system as well as its respective units were also evaluated. The combined system has shown high-capacity to remove all contaminants in the influent. In this work, the coagulant, polyacrylamide-dimethyldiallyammonium chloride-butylacrylate terpolymer (P(DMDAAC-AM-BA)), integrated with demulsifier (SD-46) could remove 91.8% of crude oil and 70.8% of COD. Hydrolysis acidification unit improved the biodegradability of the influent and the experimental results showed that the highest acidification efficiency in hydrolysis acidification reactor was 20.36% under hydraulic retention time of 7 h. The DMBR proceeded efficiently without serious blockage process of membrane fouling, and the concentration of ammonia nitrogen (NH₃-N), oil, chemical oxygen demand and biological oxygen demand in effluent were determined to be 3.4±2.1, 0.3±0.6, 89.7±21.3 and 13±4.7 mg/L.     

Water-level based discrete integrated dynamic control to regulate the flow for sewer-WWTP operation

• A model-free sewer-WWTP integrated control was proposed. • A dynamic discrete control based on the water level was developed. • The approach could improve the sewer operation against flow fluctuation. • The approach could increase transport capacity and enhance pump efficiency. This study aims to propose a multi-point integrated real-time control method based on discrete dynamic water level variations, which can be realized only based on the programmable logic controller (PLC) system without using a complex mathematical model. A discretized water level control model was developed to conduct the real-time control based on data-automation. It combines the upstream pumping stations and the downstream influent pumping systems of wastewater treatment plant (WWTP). The discretized water level control method can regulate dynamic wastewater pumping flow of pumps following the dynamic water level variation in the sewer system. This control method has been successfully applied in practical integrated operations of sewer-WWTP following the sensitive flow disturbances of the sewer system. The operational results showed that the control method could provide a more stabilized regulate pumping flow for treatment process; it can also reduce the occurrence risk of combined sewer overflow (CSO) during heavy rainfall events by increasing transport capacity of pumping station and influent flow in WWTP, which takes full advantage of storage space in the sewer system.     

Bioinspired cellulose-based membranes in oily wastewater treatment

• Cellulose-based membrane separates oily wastewater mimicking the living things. • The three central surface mechanisms were reviewed. • Preparation, performance, and mechanism are critically evaluated. • First review of wettability based cellulose membrane as major material. • The current and future importance of the research are discussed. It is challenging to purify oily wastewater, which affects water-energy-food production. One promising method is membrane-based separation. This paper reviews the current research trend of applying cellulose as a membrane material that mimics one of three typical biostructures: superhydrophobic, underwater superoleophobic, and Janus surfaces. Nature has provided efficient and effective structures through the evolutionary process. This has inspired many researchers to create technologies that mimic nature’s structures or the fabrication process. Lotus leaves, fish scales, and Namib beetles are three representative structures with distinct functional and surface properties: superhydrophobic, underwater superoleophobic, and Janus surfaces. The characteristics of these structures have been widely studied and applied to membrane materials to improve their performance. One attractive membrane material is cellulose, which has been studied from the perspective of its biodegradability and sustainability. In this review, the principles, mechanisms, fabrication processes, and membrane performances are summarized and compared. The theory of wettability is also described to build a comprehensive understanding of the concept. Finally, future outlook is discussed to challenge the gap between laboratory and industrial applications.     

Sludge fermentation liquid addition attained advanced nitrogen removal in low C/N ratio municipal wastewater through short-cut nitrification-denitrification and partial anammox

• Sludge fermentation liquid addition resulted in a high NAR of 97.4%. • Extra NH₄⁺-N from SFL was removed by anammox in anoxic phase. • Nitrogen removal efficiency of 92.51% was achieved in municipal wastewater. • The novel system could efficiently treat low COD/N municipal wastewater. Biological nitrogen removal of wastewater with low COD/N ratio could be enhanced by the addition of wasted sludge fermentation liquid (SFL), but the performance is usually limited by the introducing ammonium. In this study, the process of using SFL was successfully improved by involving anammox process. Real municipal wastewater with a low C/N ratio of 2.8–3.4 was treated in a sequencing batch reactor (SBR). The SBR was operated under anaerobic-aerobic-anoxic (AOA) mode and excess SFL was added into the anoxic phase. Stable short-cut nitrification was achieved after 46d and then anammox sludge was inoculated. In the stable period, effluent total inorganic nitrogen (TIN) was less than 4.3 mg/L with removal efficiency of 92.3%. Further analysis suggests that anammox bacteria, mainly affiliated with Candidatus_Kuenenia, successfully reduced the external ammonia from the SFL and contributed approximately 28%–43% to TIN removal. Overall, this study suggests anammox could be combined with SFL addition, resulting in a stable enhanced nitrogen biological removal.     

Wastewater treatment meets artificial photosynthesis: Solar to green fuel production,water remediation and carbon emission reduction

• Mitigating energy utilization and carbon emission is urgent for wastewater treatment. • MPEC integrates both solar energy storage and wastewater organics removal. • Energy self-sustaining MPEC allows to mitigate the fossil carbon emission. • MPEC is able to convert CO₂ into storable carbon fuel using renewable energy. • MPEC would inspire photoelectrochemistry by employing a novel oxidation reaction. Current wastewater treatment (WWT) is energy-intensive and leads to vast CO₂ emissions. Chinese pledge of “double carbon” target encourages a paradigm shift from fossil fuels use to renewable energy harvesting during WWT. In this context, hybrid microbial photoelectrochemical (MPEC) system integrating microbial electrochemical WWT with artificial photosynthesis (APS) emerges as a promising approach to tackle water-energy-carbon challenges simultaneously. Herein, we emphasized the significance to implement energy recovery during WWT for achieving the carbon neutrality goal. Then, we elucidated the working principle of MPEC and its advantages compared with conventional APS, and discussed its potential in fulfilling energy self-sustaining WWT, carbon capture and solar fuel production. Finally, we provided a strategy to judge the carbon profit by analysis of energy and carbon fluxes in a MPEC using several common organics in wastewater. Overall, MPEC provides an alternative of WWT approach to assist carbon-neutral goal, and simultaneously achieves solar harvesting, conversion and storage.