Per-and polyfluoroalkyl (PFAS) eternal pollutants: Sources, environmental impacts and treatment processes

Per- and polyfluoroalkyl substances (PFAS) have become a growing environmental concern due to their tangible impacts on human health. However, due to the large number of PFAS compounds and the analytical difficulty to identify all of them, there are still some knowledge gaps not only on their impact on human health, but also on how to manage them and achieve their effective degradation. PFAS compounds originate from man-made chemicals that are resistant to degradation because of the presence of the strong carbon-fluorine bonds in their chemical structure. This review consists of two parts. In the first part, the environmental effects of fluorinated compound contamination in water are covered with the objective to highlight how their presence in the environment adversely impacts the human health. In the second part, the focus is put on the different techniques available for the degradation and/or separation of PFAS compounds in different types of waters. Examples of removal/treatment of PFAS present in either surface or ground water are presented.

Nanoplastics removal from spiked laundry wastewater using electro-peroxidation process

Microplastics and nanoplastics (NPs) in laundry wastewater (LWW) are major sources of plastic particles in wastewater treatment plants. Unlike microplastics, almost no information exists in the literature on the degradation of NPs in LWW. In this work, the degradation of NPs in commercial LWW by the electro-peroxidation process is investigated. The obtained results demonstrated that already existing ions in LWW such as Cl- contribute to faster degradation of NPs and a complete removal could be obtained as fast as 40 min. In addition, three-dimensional excitation and emission matrix fluorescence analysis was performed, which revealed humic acid-like, aromatic proteins-like, and fulvic acid-like compounds could be oxidized after 20, 40, and 60 min of treatment respectively. The effects of operating parameters on the process performance were then examined by response surface methodology (RSM) models. The results showed that initial TOC concentration was the most important parameter influencing negatively the percentage of NP degradation. Afterward, optimization of the process revealed that the energy consumption could be minimized at 31.2 mA/cm2, 0.025 mol/L [Na2SO4], and 52 min treatment time for 52.2 mg/L initial TOC. Finally, analysis of treated LWW showed no toxicity on Daphnia magna. This study showed that the electro-peroxidation process can completely degrade NPs in LWW without any remaining toxic compounds.

Trends and challenges in the valorization of kitchen waste to polyhydroxyalkanoates

Kitchen waste (KW) is frequently available for free or with a negative cost due to its huge production. It contains a large proportion of organic substances, especially fermentable sugars, which can be used for bioplastic (polyhydroxyalkanoates or PHA) synthesis. Nevertheless, due to the difficulties in processing, various pre-treatments of KW are being investigated to enhance the concentration of simple sugars released during its hydrolysis. The effective use of KW will help in minimizing the issues of its inappropriate disposal. However, the review on KW to bioplastic synthesis is rarely reported in the literature. Hence, this particular review provides a comprehensive summary of the updated research developments in KW valorization and its potency as a feedstock for PHAs synthesis. Additionally, the impacts of KW, its availability, the necessary pre-treatments for the biopolymerization process, as well as the prospects and challenges for industrially generating sustainable PHAs, are critically discussed.

Artificial intelligence techniques in electrochemical processes for water and wastewater treatment: a review

In recent years, artificial intelligence (AI) techniques have been recognized as powerful techniques. In this work, AI techniques such as artificial neural networks (ANNs), support vector machines (SVM), adaptive neuro-fuzzy inference system (ANFIS), genetic algorithms (GA), and particle swarm optimization (PSO), used in water and wastewater treatment processes, are reviewed. This paper describes applications of the mentioned AI techniques for the modelling and optimization of electrochemical processes for water and wastewater treatment processes. Most research in the mentioned scope of study consists of electrooxidation, electrocoagulation, electro-Fenton, and electrodialysis. Also, ANNs have been the most frequent technique used for modelling and optimization of these processes. It was shown that most of the AI models have been built with a relatively low number of samples (< 150) in data sets. This points out the importance of reliability and robustness of the AI models derived from these techniques. We show how to improve the performance and reduce the uncertainty of these developed black-box data-driven models. From the perspectives of both experiment and theory, this review demonstrates how AI techniques can be effectively adapted to electrochemical processes for water and wastewater treatment to model and optimize these processes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40201-022-00835-w.

Advancements in laundry wastewater treatment for reuse: a review

Laundry related activities produce huge quantity of wastewater that is very rich in lint, dyes, surfactants, and detergents. The large amount of laundry wastewater (LWW) is generated by extensive human activities. LWW needs to be treated in order to tackle the challenging problem of water pollution and to accomplish water sustainability. To achieve this success, LWW can be reused for several purposes such as irrigation, construction activities, vehicle washing etc. However, there are several challenges in the reclamation of LWW like effective handling of the wastewater and meeting the regulatory criteria. Based on the literature review it seems that a single treatment process is not sufficient to treat LWW up to acceptable reuse standards. To that end, different treatment chains have been proposed: i) hybrid processes combining membrane filtration with adsorption; ii) advanced oxidation process using ultraviolet (UV) and hydrogen peroxide (H₂O₂); iii) coagulation-flocculation combined with sand filtration; iv) combination of ozonation process, adsorption, and ultrafiltration (UF). This review paper discusses the selection of suitable treatment technology depends on several factors: i) a well-designed equipment, ii) cost-effectiveness of treatment method and iii) desired characteristics of the treated water. The review paper also presents solutions for treatment and reclamation of LWW.

Comparison of homogeneous and heterogeneous electrochemical advanced oxidation processes for treatment of textile industry wastewater

This study aimed at understanding the influence of the generation of oxidants in a heterogeneous way at boron-doped diamond (BDD) anode (anodic oxidation (AO)) or homogeneously in the bulk (electro-Fenton (EF)) during treatment of a textile industry wastewater. Both processes achieved high TOC removal. A yield of 95 % was obtained by combining EF with BDD anode during 6 h of treatment. The EF process was found to be faster and more efficient for discoloration of the effluent, whereas AO was more effective to limit the formation of degradation by-products in the bulk. An advantage of AO was to treat this alkaline effluent without any pH adjustment. Operating these processes under current limitation allowed optimizing energy consumption in both cases. However, using BDD anode led to the formation of very high concentration of ClO₃^-/ClO₄^- from Cl^- oxidation (even at low current density), which appears as a key challenge for treatment of such effluent by AO. By comparison, EF with Pt anode strongly reduced the formation of ClO₃^-/ClO₄^-. Operating EF at low current density even maintained these concentrations below 0.5 % of the initial Cl^- concentration. A trade-off should be considered between TOC removal and formation of toxic chlorinated by-products.

Management of greywater: environmental impact, treatment, resource recovery, water recycling, and decentralization

Wastewater generated from households can be classified into greywater and blackwater. Greywater makes up a substantial portion of household wastewater. Such water consists of wastewater released from kitchen sinks, showers, laundries, and hand basins. Since the greywater is not mixed with human excreta and due to the low levels of pathogenic contamination and nitrogen, it has received more attention for recycling and reusing in recent decades. Implementing decentralized greywater treatment systems can be an effective solution to overcome water scarcity by supplying a part of water requirement, at least non-potable demand, and decreasing pollutant emissions by eliminating long-distance water transportation in remote regions, like rural and isolated areas. This review focuses on greywater management in terms of reducing environmental risks as well as the possibility of treatment. Effective management of water reclamation systems is essential for a decentralized approach and to ensure the protection of public health. In this regard, the environmental impacts of disposal or reusing the untreated greywater are discussed. Furthermore, the most appropriate technologies that can be employed for the decentralized treatment of greywaters like constructed wetlands, waste stabilization ponds, membrane systems, and electrochemical technologies are described. Finally, this review summarizes resource recovery and sustainable resource reuse.

A comprehensive review on current technologies for removal of endocrine disrupting chemicals from wastewaters

In the recent years, endocrine disrupting compounds (EDCs) has received increasing attention due to their significant toxic effects on human beings and wildlife by affecting their endocrine systems. As an important group of emerging pollutant, EDCs have been detected in various aquatic environments, including surface waters, groundwater, wastewater, runoff, and landfill leachates. Their removal from water resources has also been an emerging concern considering growing population as well as reducing access to fresh water resources. EDC removal from wastewaters is highly dependent on physicochemical properties of the given EDCs present in each wastewater types as well as various aquatic environments. Due to chemical, physical and physicochemical diversities in these parameters, variety of technologies consisting of physical, biological, electrochemical, and chemical processes have been developed for their removal. This review highlights that the effectiveness of EDC removal is highly dependent of selecting the appropriate technology; which decision is made upon a full wastewater chemical characterization. This review aims to provide a comprehensive perspective about all the current technologies used for EDCs removal from various aquatic matrices along with rising challenges such as the antimicrobial resistance gene transfer during EDC treatment.

Tertiary treatment of a mixture of composting and landfill leachates using electrochemical processes

The study investigated the treatment efficiency of coupled electrocoagulation (EC) and electrooxidation (EO) processes for landfill leachate treatment in batch and continuous mode. The EC process (iron anode and graphite cathode) at 18.2 mA/cm² for 2.5 min resulted in COD, turbidity, total phosphorus, total coliforms and fecal coliforms removal of 58.1, 72.9, 98.5, 97.9, and 97.2% respectively. Under the same operating conditions, the coupled EC/EO (Ti-Pt anode, bipolar iron electrode, and graphite cathode) processes showed that the COD, turbidity, total phosphorus, total coliforms, and fecal coliforms removal of 56.5%, 78.3%, 96.3%, 97.2% and fecal coliforms 72.7%, respectively. The energy costs associated with the EC and EC/EO were 0.11 and 0.25 $/m³, respectively. Compared to the batch configuration, the continuous configuration of EC resulted in similar processing performance. However, the EC/EO process resulted in the production of chlorates, perchlorates, and trihalomethanes as by-products. Moreover, the continuous process slightly increases the pH and ammonia concentration of the leachate and also resulted in the metallic sludge production with an average dryness of 4.2%. The toxicity tests determined that the treated effluent was not toxic to Rainbow trout and Daphnia.

Electrochemical degradation of nanoplastics in water: Analysis of the role of reactive oxygen species

Microplastics and nanoplastics (NPs) are emerging water contaminants which have recently gained lots of attention because of their effects on the aquatic systems and human life. Most of the previous works on the treatment of plastic pollution in water have been focused on microplastics and a very limited study has been performed on the NPs treatment. In this work, the role of main reactive oxygen species (ROSs) in the electrooxidation (EO) and electro-peroxidation (EO-H₂O₂) of NPs in water is investigated. In-situ generation of hydroxyl radicals (^•OH), persulfates (S₂O₈^2-), and hydrogen peroxide (H₂O₂) were performed using boron-doped diamond (BDD) as the anode, whereas titanium (in EO process) and carbon felt (CF, in EO-H₂O₂ process) were used as cathode. In the EO process, NPs were mainly oxidized by two types of ROSs on the BDD surface: (i) ^•OH from water discharge and (ii) SO₄^•- via S₂O₈^2- reaction with ^•OH. In EO-H₂O₂ process, NPs were additionally degraded by ^•OH formed from H₂O₂ decomposition as well as SO₄^•- generated from direct or indirect reactions with H₂O₂. Analysis of the degradation of NPs showed that EO-H₂O₂ process was around 2.6 times more effective than EO process. The optimum amount of NPs degradation efficiency of 86.8% was obtained using EO-H₂O₂ process at the current density of 36 mA·cm^-2, 0.03 M Na₂SO₄, pH of 2, and 40 min reaction time. In addition, 3D EEM fluorescence analysis confirmed the degradation of NPs. Finally, the economic analysis showed the treatment of NPs using EO-H₂O₂ process had an operating cost of 2.3 $US.m^-3, which was around 10 times less than the EO process. This study demonstrated that the in-situ generation of ROSs can significantly enhance the degradation of NPs in water.

Greywater characteristics, impacts, treatment, and reclamation using adsorption processes towards the circular economy

The gap between water demand and available water supply led to wastewater treatment, particularly greywater. Due to specific characteristics of grey wastewater, treatment and recycling of this type of wastewater capture global attention. This paper presents a literature review of the remediation of greywater by adsorption processes. Besides, the reclamation of the grey wastewater in the context of the circular economy is highlighted. In this regard, the characterization of various types of grey wastewater, the potential risks associated with greywater, and the properties of reclaimed water as per the regulation or guideline are summarized. These standards vary based on the application of reused water and from a country to another country. Furthermore, this review elucidates the adsorption process in terms of the type of adsorbents, modification of adsorbents and their regeneration process, adsorption isotherm, kinetics and thermodynamic of adsorption, and optimization of adsorption system. Finally, the removal of different pollutants from greywater by various adsorbents and techno-economic aspects are illustrated.

Potential of agro-industrial produced laccase to remove ciprofloxacin

Ciprofloxacin (CIP), a widely used antibiotic, is frequently detected in the environment due to insufficient wastewater and water treatment. Hence, novel, green and cost-effective technologies are required to enhance the removal of these pollutants. The potency of crude enzymes, especially laccases, produced by white-rot fungi was tested to assess their effectiveness to degrade CIP from water. Crude laccase alone could not oxidize CIP. The addition of syringaldehyde, a redox mediator, resulted in a decrease in antibiotic concentration up to 68.09±0.12% in 24 h, which was the highest removal efficiency achieved with 0.15 mg/mL syringaldehyde and 2 mg/mL of crude laccase (0.1 U/ml). Crude laccase oxidation of CIP was inhibited after 6 h of treatment. To compare, a pure enzyme with the same activity as the crude one removed 86% of CIP in 24 h. No inhibitory effect during the treatment was observed. The estimation of antimicrobial efficiency revealed that after 6 h of treatment, the toxicity towards Escherichia coli decreased by 30%. The wastewater treatment by the crude laccase-mediated system was estimated to significantly reduce the cost of enzymatic treatment.

Enhancement of landfill leachate treatment using extracellular polymeric substances as bio-flocculants

Fermentation of Klebsiella pneumoniae was conducted using crude glycerol fortified with secondary paper mill sludge as a carbon source in 5 L fermenter. After 96 hours of fermentation, the fermented broth contained mostly microbial cells surrounded by extracellular polymeric substances (EPS) and other particulate residues from paper mill sludge and glycerol. When this fermented broth is used as it is, it is called broth EPS (B-EPS). When the fermented broth is centrifuged, the supernatant solution is separated from the rest of the microbial cells and from sludge residues. This supernatant is called Slime-EPS (S-EPS). Both types of EPS were used for treatment of landfill leachate. S-EPS showed better flocculation activity (85%) than B-EPS (70%). EPS was also used in combination of Al₂(SO₄)₃ or FeSO₄. The removal efficiency of COD with use of S-EPS combined with FeSO₄ (more than 80% of COD removal) was higher than with S-EPS alone (48% of COD removal). Better results were recorded when S-EPS (0.015 g/L) was combined with FeSO₄ (2 g/L) at pH 8. A remarkable reduction of the following parameters was recorded: COD (82%), total nitrogen (44%), phosphorus (50%) and removal of metals such as Ca (64.3%) and Mg (62.4%).

Bioconversion of organic wastes into value-added products: A review

Rapid urbanization has increased the demand for food, feed, and chemicals that have in turn augmented the use of fossil-based resources and generation of organic waste. Owning to the characteristics like high abundance, renewability, and ease of accessibility, valorization of organic wastes serves as a potential solution for waste management issues. Several industrial wastes, due to their organic and nutrient-rich composition, have been utilized as a resource for the production of value-added products such as biofuels, biopesticides, biohydrogen, enzymes, and bioplastics via microbial fermentation processes. The process consists of pre-treatment of the waste biomass, production of value-added product in reactors and downstream processing for product's recovery. The integration of new comprehensive technologies for organic waste utilization will also stimulate the transition towards a circular economy. Therefore, the feasibility and sustainability of the production of various value-added products from biowastes and byproduct streams will be discussed in the present review.

Efficiency of an up-flow Anaerobic Sludge Blanket reactor coupled with an electrochemical system to remove chloramphenicol in swine wastewater

The application and design of treatment systems in wastewater are necessary due to antibiotics' potential toxicity and resistant genes on residual effluent. This work evaluated a coupled bio-electrochemical system to reduce chloramphenicol (CAP) and chemical oxygen demand (COD) on swine wastewater (SWW). SWW characterization found CAP of <10 μg/L and 17,434 mg/L of COD. The coupled system consisted of preliminary use of an Up-flow Anaerobic Sludge Blanket Reactor (UASB) followed by electrooxidation (EO). The UASB reactor (primary stage) was operated for three months at an organic load of 8.76 kg of COD/m³d and 50 mg CAP/L as initial concentration. In EO, we carried out a 2² (time operation and intensity) factorial design with a central composite design; we tried two Ti cathodes and one anode of Ti/PbO₂. Optimal conditions obtained in the EO process were 240 min of operation time and 1.51 A of current intensity. It was possible to eliminate 44% of COD and 64.2% of CAP in the preliminary stage. On bio-electrochemicals, total COD and CAP removal were 82.35 and >99.99%, respectively. This coupled system can be applied to eliminate antibiotics and other organic pollutants in agricultural, industrial, municipal, and other wastewaters.

A review on production of polyhydroxyalkanoate (PHA) biopolyesters by thermophilic microbes using waste feedstocks

Polyhydroxyalkanoates (PHAs) are produced by numerous microbes as a subcellular energy source. Despite of their diverse applications, exorbitant production cost limits their commercial synthesis. Apart from various cost determining factors such as cost-effective feedstocks or economic recovery methods, the use of appropriate bacteria holds the key to reduce the fermentation economics. Extremophiles, especially thermophilic PHA producers, could make the bioprocess economically viable by reducing the production cost in several aspects. Using variety of waste feedstocks as carbon substrates could open the way for the valorisation of industrial waste streams and cost-effective PHA production. Therefore, the article critically reviews the current knowledge of the synthesis of PHA polyesters in thermophilic conditions. Additionally, it summarises several studies on thermophilic PHA producing bacteria grown on various waste substrates. To conclude, the paper focuses on screening and recovery methods as well as technical challenges in thermophilic PHA production.

Concomitant production of value-added products with polyhydroxyalkanoate (PHA) synthesis: A review

The concern over the damaging effects of petrochemical plastics has inspired innumerable researchers to synthesize green plastics. Polyhydroxyalkanoates (PHAs) are promising candidates as they are biodegradable and possess characteristics similar to conventional plastics. However, their large-scale production and market application still have a long way to go due to the high production cost associated. Approaches like using industrial wastes as substrates and developing green strategies for PHA extraction during downstream processing have been investigated to make the process more economical. Recently, PHA production cost was minimized by concomitant synthesis of other valuable bioproducts with PHA. Investigating these co-products and recovering them can also make the process circular bioeconomic. Therefore, the paper attempts to review the recent strategies for the simultaneous synthesis of value-added bioproducts with PHA together with the challenges and opportunities for their large-scale production and applications.

Statistical optimization of arsenic removal from synthetic water by electrocoagulation system and its application with real arsenic-polluted groundwater

Arsenic presence in the water has become one of the most concerning environmental problems. Electrocoagulation is a technology that offers several advantages over conventional treatments such as chemical coagulation. In the present work, an electrocoagulation system was optimized for arsenic removal at initial concentrations of 100 µg/L using response surface methodology. The effects of studied parameters were determined by a 2³ factorial design, whereas treatment time had a positive effect and current intensity had a negative effect on arsenic removal efficiency. With a p-value of 0.1629 and a confidence of level 99%, the type of electrode material did not have a significant effect on arsenic removal. Efficiency over 90% was reached at optimal operating conditions of 0.2 A of current intensity, and 7 min of treatment time using iron as the electrode material. However, the time necessary to accomplish with OMS arsenic guideline of 10 µg/L increased from 7 to 30 min when real arsenic-contaminated groundwater with an initial concentration of 80.2 ± 3.24 µg/L was used. The design of a pilot-scale electrocoagulation reactor was determined with the capacity to meet the water requirement of a 6417 population community in Sonora, Mexico. To provide the 1.0 L/s required, an electrocoagulation reactor with a working volume of 1.79 m³, a total electrode effective surface of 701 m², operating at a current intensity of 180 A and an operating cost of 0.0208 US$/day was proposed. Based on these results, electrocoagulation can be considered an efficient technology to treat arsenic-contaminated water and meet the drinking water quality standards.

Treatment processes for microplastics and nanoplastics in waters: State-of-the-art review

In this work, established treatment processes for microplastics (MPs) and nanoplastics (NPs) in water as well as developed analytical techniques for evaluation of the operation of these processes were reviewed. In this regard, the strengths and limitations of different qualitative and quantitative techniques for the analysis of MPs and NPs in water treatment processes were first discussed. Afterward, the MPs and NPs treatment processes were categorized into the separation and degradation processes and the challenges and opportunities in their performance were analyzed. The evaluation of these processes revealed that the MPs or NPs removal efficiency of the separation and degradation processes could reach up to 99% and 90%, respectively. It can be concluded from this work that the combination of separation and degradation processes could be a promising approach to mineralize MPs and NPs in water with high efficiency.

Bivalve shells (Corbula trigona) as a new adsorbent for the defluoridation of groundwater by adsorption-precipitation

Defluoridation of groundwater was performed in a batch reactor using bivalve shell powder (BSP) as adsorbent. The physicochemical characteristics of BSP, studied by Fourier Transform Infrared, X-ray Diffraction and Inductively Coupled Plasma-Optical Emission Spectrometry after dissolution, have shown that BSP was mainly composed of crystalline CaCO₃ (∼97.8%). The effects of pH, initial fluoride concentration, adsorbent dose and contact time on the adsorption capacity of BSP were investigated. For an initial fluoride concentration of 2.2 mg/L and with 16 g/L of BSP, after 8 hours of treatment, 27.3% were eliminated at pH 7.5 versus 68% at pH 3, highlighting the efficiency of the adsorption process. The difference in adsorption capacity as a function of pH was correlated to the pHpzc of the BSP, which was equal to 8.2. Thus, at pH below pHpzc, electrostatic attraction between the fluoride anions and the positively charged adsorbent could justify the adsorption mechanism. Fittings of experimental data have evidenced that the adsorption kinetics were of pseudo-second order whereas the adsorption isotherms were of Langmuir type. The chemical precipitation of calcium fluoride was also revealed to occur upon release of Ca²⁺ from partial dissolution of CaCO₃ in acidic conditions.

Physicochemical assessment of urban wastewater of Cotonou (Benin)

The present study aims to fill the data gap analysis in urban wastewaters characteristics in Benin and its statistical analysis. Physicochemical parameters such as pH, electrical conductivity (EC), Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD₅), Total Kjeldahl Nitrogen (TKN), Total Phosphorus (TP) and UV Absorbance at 254 nm, were determined on domestic (greywater and blackwater) and industrial (hospital, pharmaceutical and commercial laundry) wastewater in Cotonou city. Analysis of variance showed a strong significant difference in the physico-chemistry of the various effluents. The pharmaceutical wastewater has the highest concentration of organic pollution (COD = 5,912 ± 1,026 mg/L, Abs.UV254 = 2.667 ± 0.327 cm^-1). The organic load of blackwater is mainly in particulate and biodegradable form. Besides, the correlation study showed the limits of pH and EC as an indicator of organic load. Furthermore, the choice of COD or BOD₅ as the main design parameter would be limited to blackwater treatment. Abs.UV254 was found to be the parameter having a strong relationship with other parameters of all effluents except blackwater. It then takes priority over COD for the treatment of greywater and industrial wastewater. For future wastewater treatment plant design, we recommend to consider Abs.UV254 as an important parameter.

Identifying economical route for crude glycerol valorization: Biodiesel versus polyhydroxy-butyrate (PHB)

Crude glycerol, a by-product of biodiesel industry, has been used for production of biodiesel and polyhydroxy-alkanoates. But question is: which product is economically favorable using crude glycerol as substrate? In this study, energy balance and economic assessment has been carried out for crude glycerol valorization for B10 biodiesel and polyhydroxy-butyrate (PHB) production. For same quantity of crude glycerol utilized, energy ratio for B10 production was higher than PHB production while unit production cost for B10 was lower than that of PHB. For 50 million L plant capacity of biodiesel, unit production cost was 0.77 $/L B10 while for 2 million kg plant capacity of PHB, unit production cost was 4.88 $/kg PHB. Thus, in present scenario production of biodiesel seems economically better than production of PHA with crude glycerol as raw material. This study is useful for researchers, environmental scientists and industries in identifying effective route for crude glycerol valorization.

Food waste valorization: Energy production using novel integrated systems

Management of food waste (FW) is a global challenge due to increasing population and economic activities. Presently, landfill and incineration are the keyways of FW management, while economical and environmental sustainability have been an issue. Therefore, the biological processes have been investigated for resource and energy recovery from FW. However, these biological approaches have certain drawbacks and cannot be a complete solution for FW management. Therefore, this review aims to offer a detailed and complete analysis of current available technologies to achieve environmental and economical sustainability. In this context, zero solid waste discharge for resource and energy recovery has been put into view. Corresponding to which several innovative technologies using integrated biological methods for resource and energy recovery from FW have been elucidated.

Treatment of microplastics in water by anodic oxidation: A case study for polystyrene

Water pollution by microplastics (MPs) is a contemporary issue which has recently gained lots of attentions. Despite this, very limited studies were conducted on the degradation of MPs. In this paper, we reported the treatment of synthetic mono-dispersed suspension of MPs by using electrooxidation (EO) process. MPs synthetic solution was prepared with distilled water and a commercial polystyrene solution containing a surfactant. In addition to anode material, different operating parameters were investigated such as current intensity, anode surface, electrolyte type, electrolyte concentration, and reaction time. The obtained results revealed that the EO process can degrade 58 ± 21% of MPs in 1 h. Analysis of the operating parameters showed that the current intensity, anode material, electrolyte type, and electrolyte concentration substantially affected the MPs removal efficiency, whereas anode surface area had a negligible effect. In addition, dynamic light scattering analysis was performed to evaluate the size distribution of MPs during the degradation. The combination of dynamic light scattering, scanning electron microscopy, total organic carbon, and Fourier-transform infrared spectroscopy results suggested that the MPs did not break into smaller particles and they degrade directly into gaseous products. This work demonstrated that EO is a promising process for degradation of MPs in water without production of any wastes or by-products.

Acclimatization of microbial community of submerged membrane bioreactor treating hospital wastewater

This study was performed to understand the dynamics of the microbial community of submerged membrane bioreactor during the acclimatization process to treat the hospital wastewater. In this regard, three acclimatization phases were examined using a mixture of synthetic wastewater (SWW) and real hospital wastewater (HWW) in the following proportions; In Phase 1: 75:25 v/v (SWW: HWW); Phase 2: 50:50 v/v (SWW: HWW); and Phase 3: 25:75 v/v (SWW: HWW) of wastewater. The microbial community was analyzed using Illumina high throughput sequencing to identify the bacterial and micro-eukaryotes community in SMBR. The acclimatization study clearly demonstrated that shift in microbial community composition with time. The dominance of pathogenic and degrading bacterial communities such as Mycobacterium, Pseudomonas, and Zoogloea was observed at the phase 3 of acclimatization. This study witnessed the major shift in the micro-eukaryotes community, and the proliferation of fungi Basidiomycota was observed in phase 3 of acclimatization.

A review on recovery of proteins from industrial wastewaters with special emphasis on PHA production process: Sustainable circular bioeconomy process development

The economy of the polyhydroxyalkanoate (PHA) production process could be supported by utilising the different by-products released simultaneously during its production. Among these, proteins are present in high concentrations in liquid stream which are released after the cell disruption along with PHA granules. These microbial proteins can be used as animal feed, adhesive material and in manufacturing of bioplastics. The recycling of the protein containing liquid stream also serves as a promising approach to maintain circular bioeconomy in the route. For this aim, it is important to obtain good yield and limit the drawbacks of protein recovery processes and associated costs. The review focuses on recycling of the liquid stream generated during acid/thermal-alkali treatment for PHA production that would close the gap in linear economy and attain circularity in the process. Examples to recover proteins from other industrial waste streams along with their applications have also been discussed.

Electro-oxidation of secondary effluents from various wastewater plants for the removal of acetaminophen and dissolved organic matter

Electro-oxidation of acetaminophen (ACT) in three different doped secondary effluents collected from a conventional Municipal Waste Water Treatment Plant (MWWTP), a MWWTP using a membrane bioreactor (WWTP MBR) and a lab-scale MBR treating source-separated urine (Urine MBR) was investigated by electro-Fenton (EF) coupled with anodic oxidation (AO) using sub-stoichiometric titanium oxide anode (Ti₄O₇). After 8 h of treatment, 90 ± 15%, 76 ± 3.8% and 46 ± 1.3% of total organic carbon removal was obtained for MWWTP, MWWTP-MBR and Urine-MBR respectively, at a current intensity of 250 mA, pH of 3 and [Fe²⁺] = 0.2 mM. Faster degradation of ACT was observed in the WWTP MBR because of the lower amount of competitive organic matter, however, >99% degradation of ACT was obtained after 20 min for all effluents. The acute toxicity of the treated effluent was measured using Microtox® tests. Results showed an initial increase in toxicity, which could be assigned to formation of more toxic by-products than parent compounds. From 3D excitation and emission matrix fluorescence (3DEEM), different reactivity was observed according to the nature of the organic matter. Particularly, an increase of low molecular weight organic compounds fluorescence was observed during Urine MBR treatment. This could be linked to the slow decrease of the acute toxicity during Urine MBR treatment and ascribed to the formation and recalcitrance of toxic organic nitrogen and chlorinated organic by-products. By comparison, the acute toxicity of other effluents decreased much more rapidly. Finally, energy consumption was calculated according to the objective to achieve (degradation, absence of toxicity, mineralization).

Effect of cathode material and charge loading on the nitrification performance and bacterial community in leachate treating Electro-MBRs

Electro-MBR technology, which combines an electrocoagulation process inside the mixed liquor of a membrane bioreactor, was studied for the treatment of a high-strength ammonia leachate (124 ± 4 mg NH₄-N L^-1). A lab-scale aerobic Electro-MBR was operated with a solid retention time of 45 days, hydraulic retention times of 24h and 12h, and charge loading ranging from 100 to 400 mAh L^-1. At 400 mAh L^-1, with a combination of a Ti/Pt cathode and a sacrificial iron anode, removal percentages for ammonia nitrogen, total organic carbon, and total phosphorus were 99.8%, 38%, and 99.0%, respectively. At 400 mAh L^-1, the estimated ferric ion dosage was 325 mg Fe³⁺ L^-1. Experiments conducted with different cathode materials showed that previously reported inhibition phenomena may result from a cathodic nitrate reduction into ammonia nitrogen. Conventional cathode materials, such as graphite, have electrochemical nitrate reduction rates of -0.03 mg NO₃-N mAh^-1. By comparison, when using Ti/Pt, the rate was -0.0045 mg NO₃-N mAh^-1(85% lower than graphite due to its low hydrogen overpotential). Charge loading tested in this study had no significant impact on both nitrification performance and microbial population diversity. However, the relative abundance of the mixed liquor's Nitrosomonas increased from 4.8% to 8.2% when the charge loading increased from 0 to 400 mAh L^-1. Results from this study are promising for future applications of the Ti/Pt - Iron Electro-MBR in various high-strength ammonia wastewater treatment applications.

Photocatalytic Degradation of Myclobutanil and Its Commercial Formulation with TiO₂ P25 in Slurry and TiO₂/β-SiC Foams

Viticulture is one of the crops most subject to pest control by fungicides. Their drainage towards the fresh water affects the aquatic environment, the fauna, the flora and especially the human health. It is therefore necessary to find an adequate solution to solve this problem. Heterogeneous photocatalysis is an advanced oxidation method for the degradation and mineralization of organic pollutants in water and air using semi-conductor (e.g., TiO²). TiO₂ P25 in suspension (0.75 g·L^-1) is used to treat Myclobutanil contaminated water and a commercial formulation Systhane™ 20EW, a fungicide produced by BASF. After 120 min of batch treatment under our conditions (pH = 6.7, Co = 10 mg ·L^-1), 96% and 98% of Myclobutanil and Systhane were removed with 94% and 92% mineralization, respectively. In order to avoid the recovery of nanoparticles of TiO² P25 after treatment, we have taken care of β-SiC foam cells. Under the same experimental conditions, 45% and 56% of Myclobutanil and Systhane degraded after 4 h with mineralization of 29% and 27%, respectively in recirculation in a fixed-light photoreactor by UV-A lamps. These results are very encouraging: filtering is not necessary to separate the catalyst from the treated water, it is very important for large-scale use of this process.

Ciprofloxacin removal via sequential electro-oxidation and enzymatic oxidation

The combination of electro-oxidation and enzymatic oxidation was tested to evaluate the potency of this system to remove ciprofloxacin (CIP), a fluoroquinolone antibiotic, from water. For the electro-oxidation boron-doped diamond (BDD) and mixed metal oxides anodes were tested, at three current densities (4.42, 17.7 and 35.4 A/cm²). BDD anode at 35.4 A/cm² exhibited the highest removal efficiency in the shortest time (>90 % removal in 6 min). For the enzymatic oxidation, laccase from Trametes versicolor was chosen. Laccase alone was not able to remove CIP; hence the influence of redox mediators was investigated. The addition of syringaldehyde (SA) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) resulted in enhanced CIP transformation. About 48.9±4.0 % of CIP remained after 4 h of treatment when SA-mediated laccase was applied and 87.8±6.6 % in the case of ABTS-mediated laccase. The coupling of enzymatic oxidation followed by electro-oxidation led to 73 % removal of the antibiotic. Additionally, the antimicrobial activity increased up to its original efficiency after the treatment. The combination of electro-oxidation followed by enzymatic oxidation led to 97-99 % removal of CIP. There was no antimicrobial activity of the solution after the treatment. The tests with wastewater confirmed the efficacy of the system to remove CIP from the complex matrix.

Techno-economic analysis for extracellular-polymeric substances (EPS) production using activated sludge fortified with crude glycerol as substrate and its application in leachate treatment

Economic assessment of bio-flocculant production process has been carried out by SuperPro Designer where extracellular-polymeric substances (EPS) were produced using activated sludge fortified with crude glycerol in fermenter followed by centrifugation. Considering EPS concentration of 60 g/L in production fermenter at 96 h, the unit production cost for slime EPS was estimated to be $ 0.95/L. The unit price of S-EPS was sensitive to inoculum size and EPS productivity (EPS concentration and fermentation time) in the fermented broth. Economic analysis was also conducted for EPS aided leachate treatment. The unit leachate treatment cost was 7.78 $/m³ and was sensitive to S-EPS unit production cost. To get same leachate treatment cost as current industrial practice (4 $/m³), S-EPS unit production cost should lower down to $ 0.5/L. The process has several advantages: 1) sludge and crude glycerol valorization for bio-flocculant production 2) Leachate treatment using environment friendly bio-flocculant.

Electro-generation of hydrogen peroxide using a graphite cathode from exhausted batteries: study of influential parameters on electro-Fenton process

In this work, the study of hydrogen peroxide (H₂O₂) electro-generation using graphite from exhausted batteries (Gr-Bat) was conducted. Linear sweep voltammetry and electrolysis experiments were carried out in a single compartment electrochemical cell. Study of the possibility to use this electrode revealed that it presents, as vitreous carbon (VC) electrode, a reduction of oxygen with two successive waves (bi-electronic reduction). The first wave corresponds to the reduction of O₂ to H₂O₂, while the second one corresponds to the reduction of H₂O₂ to H₂O. The cathodic potentials for electro-generation of H₂O₂ appeared at -600 and -700 mV vs. Ag/AgCl for Gr-Bat and VC electrodes, respectively. Subsequently, electrolysis experiments were conducted by imposing the potentials required for H₂O₂ formation. The effect of several operating parameters on H₂O₂ production, such as the nature and concentration of the electrolyte, the pH, the presence of ferrous ions and O₂ injection were studied using Gr-Bat and VC electrodes, respectively. For both electrodes, the acidic medium was more favorable for H₂O₂ electro-generation. The oxygen injection in solution promoted an increase of H₂O₂ concentration, but its effect was more pronounced in the case of VC electrode. Application for crystal violet degradation by electro-Fenton revealed that Gr-Bat had the best purification performance. A removal rate of 73.18% was obtained with Gr-Bat electrode against 62.27% with VC electrode for an electrolysis time of 120 min. This study has demonstrated the possibility of recycling Gr-Bat by using them as cathode materials in the electro-Fenton process.

MBR treatment of leachates originating from waste management facilities: A reference study of the design parameters for efficient treatment

The main objective of the study was to define the interaction between the solid retention time (SRT) and the contaminant loading rate on a membrane bioreactor's efficacy in removing contaminants frequently detected (chemical oxygen demand (COD), NH₄⁺, total phosphorus and metals) above the discharge criteria in waste-originating leachates. The rates and coefficient calculated from this study's experimental data can be used for the design of membrane bioreactor treating wastewaters, even beyond the scope of this experiment. Over a period of 152 days, SRTs of 28 and 47 days and HRTs of 13, 25, 36 and 52 h were studied using a real leachate with a constant composition. Results showed that membrane bioreactors can efficiently treat >1850 mg COD L^-1 d^-1 of highly to moderately biodegradable COD, with the SRT having no significant impact on the removal of recalcitrant COD. Overall ammonium removal rates of >740 mg NH₄-N L^-1 d^-1 can be achieved as long as a residual alkalinity of 200 mg CaCO₃ L-1 and an adequate dissolved oxygen concentration (6-7 mg L^-1) are both maintained. Overall phosphorus removal rates are independent of the phosphorus loading rate. However, the highest overall phosphorus removal rate (39 ± 2 mg P per g of total suspended solids) was obtained at the lowest SRT (28 days) due to an increased extracellular polymeric substance production. Finally, membrane bioreactor's metal removal capacity is mostly dependent on the metals' affinity to both the leachate's recalcitrant COD as well as sludge concentrations.

Identifying the link between MBRs' key operating parameters and bacterial community: A step towards optimized leachate treatment

A MBR treating compost leachate was studied in order to link the operating parameters (solid and hydraulic retention time) to contaminant's specific bacterial catabolic activity. In this context, a lab-scale aerobic membrane bioreactor was operated for 200 days, at solid retention times (SRT) of 30 and 45 days and four different contaminant load rates. Results showed that increasing the food to microorganism ratio (F/M) by increasing the contaminant load rates lessened the selectivity pressure, which allowed the proliferation of subdominant operational taxonomic units (OTU) (relative abundance >3%) that were otherwise inhibited by highly adapted dominant OTUs (relative abundance >10%). Subsequently, increasing the SRT resulted in a lower species richness and the selection of two dominant types of bacteria: 1) genera with low growth rates that feed on non-limiting substrates or substrates with few competitors, and 2) genera with metabolisms that are highly specific to the available substrates and that can outcompete the other genera by using the substrate more efficiently. The bacterial population evolution observed during this study suggests that the mixed liquor population diversity and structure can be modulated with the operating conditions for the bioenhancement of contaminant specific catabolic activity. Identified dominant and subdominant genera were linked to the MBR's NH₄⁺ and COD removal performances. Interestingly, nitrification performances were unaffected by the organic load rate and the Nitrosomonas relative abundance.

Cost, energy and GHG emission assessment for microbial biodiesel production through valorization of municipal sludge and crude glycerol

In this study, cost simulations were made based on 20 million L blended biodiesel B-10 production per year using INRS and conventional process. In case of INRS process, microbial lipid was produced by T. oleaginosus using washed municipal secondary sludge fortified with crude glycerol while lipid was extracted from wet biomass using biodegradable surfactant and petroleum-diesel (PD). The conventional process uses commercial substrates for lipid production and organic solvents for lipid extraction from dry biomass. The unit B-10 production cost of INRS process was estimated to be $ 0.72/L for an annual capacity of 20 million L, which is 9.5 times more economical than conventional biodiesel production process. For INRS process, the unit B-10 biodiesel production cost was sensitive to plant capacity and lipid productivity during the fermentation. INRS process exhibited positive net energy gain and positive GHG capture, which proves to be energetically and environmentally viable.

The bacterial community structure of submerged membrane bioreactor treating synthetic hospital wastewater

The pharmaceuticals are biologically active compounds used to prevent and treat diseases. These pharmaceutical compounds were not fully metabolized by the human body and thus excreted out in the wastewater stream. Thus, the study on the treatment of synthetic hospital wastewater containing pharmaceuticals (ibuprofen, carbamazepine, estradiol and venlafaxine) was conducted to understand the variation of the bacterial community in a submerged membrane bioreactor (SMBR) at varying hydraulic retention time (HRT) of 6, 12 and 18 h. The variation in bacterial community dynamics of SMBR was studied using high throughput sequencing. The removal of pharmaceuticals was uniform at varying HRT. The removal of both ibuprofen and estradiol was accounted for 90%, whereas a lower removal of venlafaxine (<10%) and carbamazepine (>5%) in SMBR was observed. The addition of pharmaceuticals alters the bacterial community structure and result in increased abundance of bacteria (e.g., Flavobacterium, Pedobacter, and Methylibium) reported to degrade toxic pollutant.

Kinetics and mechanism of Paraquat's degradation: UV-C photolysis vs UV-C photocatalysis with TiO2/SiC foams

In this study, the photolytic and photocatalytic removal of the herbicide paraquat is investigated under UV-C (254 nm). For photocatalytic experiments, SiC foams were used with P25-TiO₂ nanoparticles deposited by dip-coating. The foams were characterized by scanning electron microscopy and paraquat's degradation under UV-C photolysis or photocatalysis, followed by UV-vis spectroscopy, total organic carbon analyzer, LC-MS and ion chromatography. After 3 h of reactions by photolysis and photocatalysis, 4% and 91% of TOC removal were observed. An analysis of degradation by-products showed a similar degradation pathway with pyridinium ions observed by LC/MS and carboxylic acids (succinate, acetate, oxalate and formate) detected by ion chromatography. In conclusion, these two different photo-degradation processes are able to remove paraquat and produce similar by-products. However, the kinetics of degradation is rather slow during photolysis and it is recommended to combine the UV-C lightning with a TiO₂ photocatalyst to improve the mineralization rate.

Appearance of ciprofloxacin/chlortetracycline-resistant bacteria in waters of Québec City in Canada

Most of the waterborne fecal pathogens belong to the family of Gram-negative bacteria. Hence, minimal inhibitory concentrations of chlortetracycline and ciprofloxacin antibiotics towards Gram-negative representative, Enterobacter aerogenes were estimated, which were 7 μg/ml and 0.125 μg/ml, respectively. The combined antimicrobial effect of chlortetracycline and ciprofloxacin against E. aerogenes was also investigated to establish their potential interaction towards the pathogens present in water. Eventually, the water samples obtained from various drinking water treatment plants from Québec municipality were tested for the occurrence of chlortetracycline-, ciprofloxacin- and chlortetracycline/ciprofloxacin-resistant strains.

Microwave-assisted one-pot conversion of agro-industrial wastes into levulinic acid: An alternate approach

Brewery liquid waste (BLW), brewery spent grain (BSG), apple pomace solid wastes (APS), apple pomace ultrafiltration sludge (APUS) and starch industry waste (SIW) were evaluated as alternative feedstocks for levulinic acid (LA) production via microwave-assisted acid-catalyzed thermal hydrolysis. LA production of 204, 160, 66, 49 and 12 g/kg was observed for BLW, BSG, APS, APUS, and SIW, respectively, at 140 °C, 40 g/L substrate concentration (SC), 60 min and 2 N HCl (acid concentration). Based on the screening studies, BLW and BSG were selected for optimization studies using response surface methodology. Maximum LA production of 409 and 341 g/kg for BLW and BSG, respectively were obtained at 160 °C, 4.5 M HCl, 85 g/L SC and 27.5 min. Results demonstrated the possibility of using brewery wastes as promising substrates for economical and higher yield production of LA, a renewable platform chemical and versatile precursor for fuels and chemicals.

Optimization process of organic matter removal from wastewater by using Eichhornia crassipes

This study aimed to determine the optimal conditions for organic matter removal from wastewater by Eichhornia crassipes (E.C). As a matter of fact, a complete factorial design was used to determine the effect of residence time (X₁), plant density (X₂) and initial chemical oxygen demand (COD) concentration (X₃) on the phytoremediation process. The process's performance was measured on COD (Y₁), NH₄⁺ (Y₂) and PO₄^3- (Y₃), with the results indicating a reduction of 8.59-81.71% of COD (Y₁); 22.53-95.81% of NH₄⁺ (Y₂) and 0.54-99.35% of PO₄^3- (Y₃). Then, the first-order models obtained for COD, NH₄⁺ and PO₄^3- removal were validated using different statistical approaches such as statistical and experimental validation. Moreover, multi-response optimization was carried out through different scenarios. On the whole, the results obtained indicated that two serial ponds are required for an optimum organic matter removal by Eichhornia crassipes. Indeed, for the first pond, a residence time of 15 days is needed with a plant density of 60 ft/m² and an initial concentration of about 944 mg/L. The second was the same residence time as the first with similar plant density of 60 ft/m² and an initial load 192 mg/L (> 200 mg/L). Optimal organic matter removal from wastewater using Eichhornia crassipes requires two ponds arranged in chain.

Activation of persulfate by homogeneous and heterogeneous iron catalyst to degrade chlortetracycline in aqueous solution

This study investigates the removal of chlortetracycline (CTC) antibiotic using sulfate radical-based oxidation process. Sodium persulfate (PS) was used as a source to generate sulfate radicals by homogeneous (Fe²⁺) and heterogeneous (zero valent iron, ZVI) iron as a catalyst. Increased EDTA concentration was used to break the CTC-Fe metal complexes during CTC estimation. The influence of various parameters, such as PS concentration, iron (Fe²⁺ and ZVI) concentration, PS/iron molar ratio, and pH were studied and optimum conditions were reported. CTC removal was increased with increasing concentration of PS and iron at an equal molar ratio of PS/Fe²⁺ and PS/ZVI processes. PS/Fe²⁺ and PS/ZVI oxidation processes at 1:2 (500 μM PS and 1000 μM) molar ratio showed 76% and 94% of 1 μM CTC removal in 2 h. Further increased molar ratio 1:2 onwards, PS/Fe²⁺ process showed a slight increase in CTC degradation whereas in PS/ZVI process showed similar degradation to 1:2 (PS/Fe) ratio at constant PS 500 μM concentration. Slower activation of persulfate which indirectly indicates the slower generation of sulfate radicals in PS/ZVI process showed higher degradation efficiency of CTC. The detected transformation products and their estrogenicity results stated that sulfate radicals seem to be efficient in forming stable and non-toxic end products.