Treatment of bypass wastewater using potassium ferrate(VI): assessing the role of mixing

Sources, Fate, and Detection of Dust-Associated Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS): A Review

The occurrence of sand and dust storms (SDSs) is essential for the geochemical cycling of nutrients; however, it is considered a meteorological hazard common to arid regions because of the adverse impacts that SDSs brings with them. One common implication of SDSs is the transport and disposition of aerosols coated with anthropogenic contaminants. Studies have reported the presence of such contaminants in desert dust; however, similar findings related to ubiquitous emerging contaminants, such as per- and poly-fluoroalkyl substances (PFAS), have been relatively scarce in the literature. This article reviews and identifies the potential sources of dust-associated PFAS that can accumulate and spread across SDS-prone regions. Furthermore, PFAS exposure routes and their toxicity through bioaccumulation in rodents and mammals are discussed. The major challenge when dealing with emerging contaminants is their quantification and analysis from different environmental media, and these PFAS include known and unknown precursors that need to be quantified. Consequently, a review of various analytical methods capable of detecting different PFAS compounds embedded in various matrices is provided. This review will provide researchers with valuable information relevant to the presence, toxicity, and quantification of dust-associated PFAS to develop appropriate mitigation measures.

Leachate post-treatment by electrocoagulation process: Effect of polarity switching and anode-to-cathode surface area

In the electrocoagulation process, passivation or corrosion of the electrodes is one of the biggest challenges that cause a drop in treatment effectiveness. In this study, the effect of polarity switching was investigated, for the first time, in an attempt to enhance electrocoagulation treatment's ability to remove chemical oxygen demand (COD) and color from pretreated landfill leachate. Moreover, the ratio of the anode to cathode surface area and rotating electrode were examined in light of experimental results. The effect of different parameters, including the stirring speed, initial leachate pH, electrical current density, anode to cathode surface area ratio, and polarity switching time on system efficiency, was evaluated using the one-factor-at-a-time (OFAT) classical method. According to the results, polarity switching resulted in an almost 18% increase in COD removal, 14% increase in color removal, 13% decrease in electrical energy consumption (EEC), 51% decrease in the specific sludge production (TSS/COD), and improved electrode performance compared to non-polarity switching mode. The findings of this research showed the highest COD and color removal efficiencies, which were 34% and 67%, respectively, in a 120 min period, a stirring speed of 135 rpm, the initial leachate pH of 9, the current density of 14.4 mA/cm², the anode/cathode surface ratio of 0.35, and the polarity switching time of 300 s.

Disinfection and antimicrobial processes

This is a review of some of the literature published in 2019 related to disinfection and antimicrobial processes. This review includes the following main sections: drinking water disinfection, wastewater disinfection, and antimicrobial resistance. PRACTITIONER POINTS: Emerging technologies to disinfect viruses in drinking water treatment plants are growing. Developing processes to adequately treat bypass wastewater exceeding the plant's capacity is crucial. Antimicrobial resistance poses a major challenge leading to being classified as emerging pollutants.

Soluble chemical oxygen demand removal from bypass wastewater using iron electrocoagulation

In-plant wastewater treatment strategies to handle bypass wastewater exceeding design capacity are insufficiently investigated in the scientific literature notwithstanding their importance in ensuring sustainable wastewater management. In this study, the effectiveness of iron electrocoagulation was investigated, for the first time, to enhance primary treatment capability in removing soluble chemical oxygen demand (sCOD) from bypass wastewater. In addition, the appropriate assumptions and experimental protocols for the application of adsorption isotherm models, widely used to describe the electrocoagulation process, were discussed in light of experimental results. Under neutral pH conditions, the bypass wastewater treatment was performed to test the effects of three preselected variables (electrolysis duration, current density, and temperature) on sCOD removal. Using a 15 mA/cm² current density, an average 52% sCOD removal efficiency was achieved after 15 min at 23 °C while approximately 40 min were needed to attain comparable removal efficiency at 8 °C. sCOD removals of 74% and 87% were achieved after 40 min treatment using a 22 mA/cm² current density at 8 °C and 23 °C, respectively. Experimental results and theory show that adsorption equilibrium was not reached in the electrocoagulation cell; consequently, variable-order-kinetic (VOK) models derived from Langmuir and Langmuir-Freundlich adsorption expressions were adapted to describe the process. These models were modified to account for the de facto estimation of ferric hydroxide (adsorbent) mass that accounts for the conversion of ferrous ion to particulate end products. The Langmuir-based VOK model was found to better describe sCOD removal under all the operating conditions tested and showed the sCOD removal mechanism to be consistent with chemisorption. This research shows the promising ability of iron electrocoagulation to achieve superior removal of sCOD as compared to established and emerging standalone bypass wastewater treatment technologies.