Evaluation of pathogen disinfection efficiency of electrochemical advanced oxidation to become a sustainable technology for water reuse

Modelling and optimization of membrane process for removal of biologics (pathogens) from water and wastewater: Current perspectives and challenges

As one of the 17 sustainable development goals, the United Nations (UN) has prioritized "clean water and sanitation" (Goal 6) to reduce the discharge of emerging pollutants and disease-causing agents into the environment. Contamination of water by pathogenic microorganisms and their existence in treated water is a global public health concern. Under natural conditions, water is frequently prone to contamination by invasive microorganisms, such as bacteria, viruses, and protozoa. This circumstance has therefore highlighted the critical need for research techniques to prevent, treat, and get rid of pathogens in wastewater. Membrane systems have emerged as one of the effective ways of removing contaminants from water and wastewater However, few research studies have examined the synergistic or conflicting effects of operating conditions on newly developing contaminants found in wastewater. Therefore, the efficient, dependable, and expeditious examination of the pathogens in the intricate wastewater matrix remains a significant obstacle. As far as it can be ascertained, much attention has not recently been given to optimizing membrane processes to develop optimal operation design as related to pathogen removal from water and wastewater. Therefore, this state-of-the-art review aims to discuss the current trends in removing pathogens from wastewater by membrane techniques. In addition, conventional techniques of treating pathogenic-containing water and wastewater and their shortcomings were briefly discussed. Furthermore, derived mathematical models suitable for modelling, simulation, and control of membrane technologies for pathogens removal are highlighted. In conclusion, the challenges facing membrane technologies for removing pathogens were extensively discussed, and future outlooks/perspectives on optimizing and modelling membrane processes are recommended.

Electrochemical arsenite oxidation for drinking water treatment: Mechanisms, by-product formation and energy consumption

The mechanisms and by-product formation of electrochemical oxidation (EO) for As(III) oxidation in drinking water treatment using groundwater was investigated. Experiments were carried out using a flowthrough system, with an RuO2/IrO2 MMO Ti anode electrode, fed with synthetic and natural groundwater containing As(III) concentrations in a range of around 75 and 2 µg/L, respectively. Oxidation was dependent on charge dosage (CD) [C/L] and current density [A/m2], with the latter showing plateau behaviour for increasing intensity. As(III) concentrations of <0.3 µg/L were obtained, indicating oxidation of 99.9 % of influent As(III). Achieving this required a higher charge dosage for the natural groundwater (>40 C/L) compared to the oxidation in the synthetic water matrix (20 C/L), indicating reaction with natural organic matter or other compounds. As(III) oxidation in groundwater required an energy consumption of 0.09 and 0.21 kWh/m3, for current densities of 20 and 60 A/m2, respectively. At EO settings relevant for As(III) oxidation, in the 30-100 C/L CD range, the formation of anodic by-products, as trihalomethanes (THMs) (0.11-0.75 µg/L) and bromate (<0.2 µg/L) was investigated. Interestingly, concentrations of the formed by-products did not exceed strictest regulatory standards of 1 µg/L, applicable to Dutch tap water. This study showed the promising perspective of EO as electrochemical advanced oxidation process (eAOP) in drinking water treatment as alternative for the conventional use of strong oxidizing chemicals.

Study of helminth eggs ( Ascaris suum) inactivation by anaerobic digestion and electrochemical treatment

Background

The use of insufficiently treated wastewater or Faecal sludge in agriculture raises concerns because of the pathogen content. Helminth eggs (HE) are one of the most crucial pathogens for ensuring public health and safety. Widely used disinfection treatment methods do not guarantee the complete inactivation of helminth eggs. The current study evaluated the effectiveness of anaerobic digestion and electrochemical process on helminth ( Ascaris suum) egg inactivation.

Methods

Lab-scale biochemical methane potential (BMP) assay was conducted by spiking A. suum eggs in a serum bottle. Total solid (TS), volatile solid (VS), pH, biogas production and its composition, and volatile fatty acids (VFA) were analyzed along with A. suum inactivation every third day for the initial 15 days and fifth day for 45 days. In the second set of experiments, a hypochlorite (4700 ppm) solution was generated by electrolysis of aqueous NaCl solution in a membrane-less electrochemical cell. The hypochlorite was diluted (940, 470, 235, and 156ppm) in wastewater, spiked with A. suum eggs and then examined for inactivation at regular intervals.

Results

The results of the anaerobic digestion treatment documented 98% inactivation of A. suum eggs (0.15 eggs/mL) in 35 days and remained at 0.14 eggs/mL until day 45. Correlation analysis revealed a positive relationship between non-viable eggs and pH and a negative relationship with all the other parameters. Electrochemical treatment achieved 10% inactivation at 940 ppm concentration in 24h.

Conclusions

This study revealed that the inactivation of A. suum eggs by anaerobic digestion or electrochemical treatment is a combined effect of more than one parameter.

An integrated approach for the assessment of the electrochemical oxidation of diclofenac: By-product identification, microbiological and eco-genotoxicological evaluation

Diclofenac (DCF), a contaminant of emerging concern, is a non-steroidal anti-inflammatory drug widely detected in water bodies, which demonstrated harmful acute and chronic toxicity toward algae, zooplankton and aquatic invertebrates, therefore its removal from impacted water is necessary. DCF is recalcitrant toward traditional treatment technologies, thus, innovative approaches are required. Among them, electrochemical oxidation (EO) has shown promising results. In this research, an innovative multidisciplinary approach is proposed to assess the electrochemical oxidation (EO) of diclofenac from wastewater by integrating the investigations on the removal efficiency and by-product identification with the disinfection capacity and the assessment of the effect on environmental geno-toxicity of by-products generated through the oxidation. The electrochemical treatment successfully degraded DCF by achieving >98 % removal efficiency, operating with NaCl 0.02 M at 50 A m-2. By-product identification analyses showed the formation of five DCF parental compounds generated by decarboxylic and CN cleavage reactions. The disinfection capacity of the EO technique was evaluated by carrying out microbiological tests on pathogens generally found in aquatic environments, including two rod-shaped Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli), one rod-shaped Gram-positive bacterium (Bacillus atrophaeus), and one Gram-positive coccus (Enterococcus hirae). Eco-toxicity was evaluated in freshwater organisms (algae, rotifers and crustaceans) belonging to two trophic levels through acute and chronic tests. Genotoxicity tests were carried out by Comet assay, and relative expression levels of catalase, manganese and copper superoxide dismutase genes in crustaceans. Results highlight the effectiveness of EO for the degradation of diclofenac and the inactivation of pathogens; however, the downstream mixture results in being harmful to the aquatic ecosystem.

The Rise of Electroactive Materials in Face Masks for Preventing Virus Infections

Air-transmitted pathogens may cause severe epidemics, posing considerable threats to public health and safety. Wearing a face mask is one of the most effective ways to prevent respiratory virus infection transmission. Especially since the new coronavirus pandemic, electroactive materials have received much attention in antiviral face masks due to their highly efficient antiviral capabilities, flexible structural design, excellent sustainability, and outstanding safety. This review first introduces the mechanism for preventing viral infection or the inactivation of viruses by electroactive materials. Then, the applications of electrostatic-, conductive-, triboelectric-, and microbattery-based materials in face masks are described in detail. Finally, the problems of various electroactive antiviral materials are summarized, and the prospects for their future development directions are discussed. In conclusion, electroactive materials have attracted great attention for antiviral face masks, and this review will provide a reference for materials scientists and engineers in antiviral materials and interfaces.

Water treatment and reclamation by implementing electrochemical systems with constructed wetlands

Seasonal or permanent water scarcity in off-grid communities can be alleviated by recycling water in decentralized wastewater treatment systems. Nature-based solutions, such as constructed wetlands (CWs), have become popular solutions for sanitation in remote locations. Although typical CWs can efficiently remove solids and organics to meet water reuse standards, polishing remains necessary for other parameters, such as pathogens, nutrients, and recalcitrant pollutants. Different CW designs and CWs coupled with electrochemical technologies have been proposed to improve treatment efficiency. Electrochemical systems (ECs) have been either implemented within the CW bed (ECin-CW) or as a stage in a sequential treatment (CW + EC). A large body of literature has focused on ECin-CW, and multiple scaled-up systems have recently been successfully implemented, primarily to remove recalcitrant organics. Conversely, only a few reports have explored the opportunity to polish CW effluents in a downstream electrochemical module for the electro-oxidation of micropollutants or electro-disinfection of pathogens to meet more stringent water reuse standards. This paper aims to critically review the opportunities, challenges, and future research directions of the different couplings of CW with EC as a decentralized technology for water treatment and recovery.