Hybrid electrocoagulation/electroflotation/electrodisinfection process as a pretreatment for seawater desalination

Enhanced chromium removal from tannery wastewater through electrocoagulation with iron electrodes: Leveraging the Box-Behnken design for optimization

This study is focused on reducing total chromium level in tannery wastewater through the electrocoagulation process, in order to comply with the maximum permissible limits (MPL) and to determine the effects from its main operating factors. For this purpose, a batch electrocoagulation reactor was manufactured using iron electrodes. Next, the response surface methodology was applied in the experimental design using a Box-Behnken design (BBD) with three factors: current intensity, treatment time, and p H level. In addition, the total chromium removal percentage was taken as a response variable. The corresponding statistical analysis revealed that the treatment time, current intensity, and p H level variables were significant at a confidence level of P - v a l u e < 0.05 . Obtained in this study for a 99 % total chromium removal were: current intensity ( I ) = 2.9 A , time ( t ) = 18.1 min , and p H = 5.6 . Our results indicated that the electrocoagulation process effectively removes total chromium from tannery effluents up to MPL values.

Review of Hybrid Membrane Distillation Systems

Membrane distillation (MD) is an attractive separation process that can work with heat sources with low temperature differences and is less sensitive to concentration polarization and membrane fouling than other pressure-driven membrane separation processes, thus allowing it to use low-grade thermal energy, which is helpful to decrease the consumption of energy, treat concentrated solutions, and improve water recovery rate. This paper provides a review of the integration of MD with waste heat and renewable energy, such as solar radiation, salt-gradient solar ponds, and geothermal energy, for desalination. In addition, MD hybrids with pressure-retarded osmosis (PRO), multi-effect distillation (MED), reverse osmosis (RO), crystallization, forward osmosis (FO), and bioreactors to dispose of concentrated solutions are also comprehensively summarized. A critical analysis of the hybrid MD systems will be helpful for the research and development of MD technology and will promote its application. Eventually, a possible research direction for MD is suggested.

Hybrid electrochemical/membrane couplings processes for enhancing seawater pretreatment and desalination

This research focuses on boosting seawater pretreatment and desalination through electrocoagulation (EC)/ultrafiltration (UF) and electrocoagulation (EC)/nanofiltration (NF) processes. We first optimized the key parameters of the EC process using aluminum (Al) and iron (Fe) electrodes. Experimental results show EC process is efficient under optimal conditions. Second, membrane filtration using UF (ES10B), NF(UTC60) and NF(200) as post-processing steps to the EC process were experimented with. EC(Al)/NF(UTC60) combination resulted in the highest removal rate of organic matter (COD 98%, TOC 95%, fluorescence [humic and fulvic acids] 68%), optical density (OD600nm 75%, turbidity 70%, conductivity 64%). In terms of major ions removal, up to 55% was achieved as NF decreases conductivity, salinity, and hardness. EC(Al)/NF(UTC60) seawater permeate demonstrated the best results in terms of lowest flux decline (J/Jo  = 0.9) and fouling, which was realized by resistance in series and recovery factor rate (%). Additionally, NF(UTC60) fouling reversibility led to a longer lifetime and higher recovery factor (93%). PRACTITIONER POINTS: Pretreatment by hybrid processes was experimented with to enhance the saline water treatment. Organic matter (COD 98%, TOC 95%, fluorescence [humic and fulvic acids] 68%) and turbidity were successfully removed. Salinity and hardness (conductivity 64%) were highly reduced by NF. Flux decline, retention rate, and membrane fouling were studied.

Continuous electrocoagulation treatment system for partial desalination of tropical brackish peat water in Sarawak coastal peatlands

Sarawak coastal peatlands located on Borneo Island have vast availability of brackish peat water sources especially in some coastal rural areas. However, brackish peat water is currently underutilized as the source for water treatment plants due to excessive salinity levels. As such, this study aims to investigate the salinity reduction in brackish peat water sources for domestic consumption in Sarawak coastal peatlands by utilizing continuous electrocoagulation treatment with aluminium electrodes. Correspondingly, this study analyzes the effects of salinity percentage, electric current, and flow rate on salinity reduction with electrocoagulation treatment. This study has found that the treated salinity levels in brackish peat water with 30 % of salinity percentage meet the Malaysia Class I in National Water Quality Standard. The study has also identified both monolayer and multilayer adsorption that occurs in electrocoagulation treatment as the precursor to salinity reduction. In addition, the presence of in-situ aluminium hydroxide coagulants could adsorb some sodium chloride from brackish peat water with 70 % of salinity percentage at 2503 mg/g of maximum adsorption capacity and 2.65 min^-1 of adsorption rate. This study has also found that electrocoagulation treatment could achieve 91.78 % of maximum salinity reduction efficiency at an optimum electric current of 5 A and flow rate of 1.2 L/min in brackish peat water with 30 % of salinity percentage. This treatment system costs only Ringgit Malaysia (RM) 0.29 or United States Dollars (USD) 0.06 per meter cubic of treated brackish peat water. Overall, this study demonstrates that continuous electrocoagulation treatment could partially desalinate brackish peat water with 30 % of salinity percentage in which the treated salinity levels could be utilized for domestic consumption in Sarawak coastal peatlands at reasonable cost.

Corrosion of Titanium Electrode Used for Solar Saline Electroflotation

The solar electroflotation (EF) processes using saline electrolytes are today one of the great challenges for the development of electrochemical devices, due to the corrosion problems that are generated during the operation by being in permanent contact with Cl^- ions. This manuscript discloses the corrosion behavior of titanium electrodes using a superposition model based on mixed potential theory and the evaluation of the superficial performance of the Ti electrodes operated to 4 V/SHE solar electroflotation in contact with a solution of 0.5 M NaCl. Additionally provided is an electrochemical analysis of Ti electrodes regarding HER, ORR, OER, and CER that occur during the solar saline EF process. The non-linear superposition model by mixed potential theory gives electrochemical and corrosion parameters that complement the information published in scientific journals, the corrosion current density and corrosion potential in these conditions is 0.069 A/m² and -7.27 mV, respectively. The formation of TiO₂ and TiOCl on the anode electrode was visualized, resulting in a reduction of its weight loss of the anode electrode.

Recent Desalination Technologies by Hybridization and Integration with Reverse Osmosis: A Review

Reverse osmosis is the leading technology for desalination of brackish water and seawater, important for solving the growing problems of fresh water supply. Thermal technologies such as multi-effect distillation and multi-stage flash distillation still comprise an important portion of the world’s desalination capacity. They consume substantial amounts of energy, generally obtained from fossil fuels, due to their low efficiency. Hybridization is a strategy that seeks to reduce the weaknesses and enhance the advantages of each element that makes it up. This paper introduces a review of the most recent publications on hybridizations between reverse osmosis and thermal desalination technologies, as well as their integration with renewable energies as a requirement to decarbonize desalination processes. Different configurations provide improvements in key elements of the system to reduce energy consumption, brine production, and contamination, while improving product quality and production rate. A combination of renewable sources and use of energy and water storage systems allow for improving the reliability of hybrid systems.

Recent advances in adsorption and coagulation for boron removal from wastewater: A comprehensive review

The anthropogenic emission of boron to river has become a serious problem that deteriorates the water quality and endangers the ecosystem. Although boron is a micronutrient, it is toxic to plants, animals and humans upon exposure. In this review, we first present the sources of the boron-containing streams and their composition, and then summarize the recent progress of boron removal methods based on adsorption and coagulation systematically. The boron-spiked streams are produced from coal-fired and geothermal power plants, the manufacturing and the activities of oil/gas excavation and mining. The adsorbents for boron removal are classified into the ones functionalized by chelating groups, the ones on the basis of clays or metal oxide. Three subgroups reside in the coagulation approach: electrocoagulation, chemical precipitation and chemical oxo-precipitation. The hybrid technology that combines membrane process and adsorption/coagulation was covered as well. To provide a comprehensive view of each method, we addressed the reaction mechanism, specified the strength and weakness and summarized the progress in the past 5 years. Ultimately, the prospective for future research and the possible improvement on applicability and recyclability were proposed.

Pretreatment technologies for industrial effluents: Critical review on bioenergy production and environmental concerns

The implementation of different pretreatment techniques and technologies prior to effluent discharge is a direct result of the inefficiency of several existing wastewater treatment methods. A majority of the industrial sectors have known to cause severe negative effects on the environment. The five major polluting industries are the paper and pulp mills, coal manufacturing facilities, petrochemical, textile and the pharmaceutical sectors. Pretreatment methods have been widely used in order to lower the toxicity levels of effluents and comply with environmental standards. In this review, the possible environmental benefits and concerns of adopting different pretreatment technologies for renewable energy production and product/resource recovery has been reviewed and discussed.