Sulfate radical-based advanced oxidation processes (SR-AOPs) employing heterogeneous catalysts to generate sulfate radical (SO4 −) from peroxymonosulfate (PMS) and persulfate (PS) have been extensively employed for organic contaminant removal in water. This article aims to provide a state–of–the–art review on the recent development in heterogeneous catalysts including single metal, mixed metal, and nonmetal carbon catalysts for organic contaminants removal, with particular focus on PMS activation. The hybrid heterogeneous catalyst/PMS systems integrated with other advanced oxidation technologies is also discussed. Several strategies for the identification of principal reactive radicals in SO4 −–oxidation systems are evaluated, namely (i) use of chemical probe or spin trapping agent coupled with analytical tools, and (ii) competitive kinetic approach using selective radical scavengers. The main challenges and mitigation strategies pertinent to the SR-AOPs are identified, which include (i) possible formation of oxyanions and disinfection byproducts, and (ii) dealing with sulfate produced and residual PMS. Potential future applications and research direction of SR-AOPs are proposed. These include (i) novel reactor design for heterogeneous catalytic system based on batch or continuous flow (e.g. completely mixed or plug flow) reactor configuration with catalyst recovery, and (ii) catalytic ceramic membrane incorporating SR-AOPs.

Generation of sulfate radical through heterogeneous catalysis for organic contaminants removal: Current development, challenges and prospects

Pretreatment methods to improve sludge anaerobic degradability: a review.

Electrochemical processes have been extensively investigated for the removal of a range of organic and inorganic contaminants. The great majority of these studies were conducted using nitrate-, perchlorate-, sulfate-, and chloride-based electrolyte solutions. In actual treatment applications, organic and inorganic constituents may have substantial effects on the performance of electrochemical treatment. In particular, the outcome of electrochemical oxidation will depend on the concentration of chloride and bromide. Formation of chlorate, perchlorate, chlorinated, and brominated organics may compromise the quality of the treated effluent. A critical review of recent research identifies future opportunities and research needed to overcome major challenges that currently limit the application of electrochemical water treatment systems for industrial and municipal water and wastewater treatment. Given the increasing interest in decentralized wastewater treatment, applications of electrolytic systems for treat...

Challenges and Opportunities for Electrochemical Processes as Next-Generation Technologies for the Treatment of Contaminated Water

State of the art and review on the treatment technologies of water reverse osmosis concentrates.

Globally, there is increasing awareness that renewable energy and energy efficiency are vital for both creating new economic opportunities and controlling the environmental pollution. AD technology is the biochemical process of biogas production which can change the complex organic materials into a clean and renewable source of energy. AcoD process is a reliable alternative option to resolve the disadvantages of single substrate digestion system related to substrate characteristics and system optimization. This paper reviewed the research progress and challenges of AcoD technology, and the contribution of different techniques in biogas production engineering. As the applicability and demand of the AcoD technology increases, the complexity of the system becomes increased, and the characterization of organic materials becomes volatile which requires advanced methods for investigation. Numerous publications have been noted that ADM1 model and its modified version becomes the most powerful tool to optimize the AcoD process of biogas production, and indicating that the disintegration and hydrolysis steps are the limiting factors of co-digestion process. Biochemical methane potential (BMP) test is promising method to determine the biodegradability and decomposition rate of organic materials. The addition of different environmentally friendly nanoparticles can improve the stability and performance of the AcoD system. The process optimization and improvement of biogas production still seek further investigations. Furthermore, using advanced simulation approaches and characterization methods of organic wastes can accelerate the transformation to industrializations, and realize the significant improvement of biogas production as a renewable source and economically feasible energy in developing countries, like China. Finally, the review reveals, designing and developing a framework, including various aspects to improve the biogas production is essential.

Anaerobic co-digestion process for biogas production: Progress, challenges and perspectives

Technologies to recover nitrogen, phosphorus, and potassium from waste streams have undergone accelerated development in the past decade, predominantly due to a surge in fertilizer prices and stringent discharge limits on these nutrients. This review provides a critical state of art review of appropriate technologies which identifies research gaps, evaluates current and future potential for application of the respective technologies, and outlines paths and barriers for adoption of the nutrient recovery technologies. The different technologies can be broadly divided into the sequential categories of nutrient accumulation, followed by nutrient release, followed by nutrient extraction. Nutrient accumulation can be achieved via plants, microorganisms (algae and prokaryotic), and physicochemical mechanisms including chemical precipitation, membrane separation, sorption, and binding with magnetic particles. Nutrient release can occur by biochemical (anaerobic digestion and bioleaching) and thermochemical treatm...

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Technologies to Recover Nutrients from Waste Streams: A Critical Review

Decreasing activated sludge thermal hydrolysis temperature reduces product colour, without decreasing degradability.

In hydrolysis-limited anerobic systems, the key parameters describing degradation are degradability extent ( fd), and the lumped apparent first order coefficient (khyd). These are often measured in biological methane potential (BMP) tests. Using modern techniques, it should also be possible to estimate these parameters in full-scale systems, especially where inputs are dynamic. In this study, we evaluated fd and khyd values and uncertainty based on nonlinear parameter estimation from (i) BMP tests and (ii) effluent gas and solids from two full-scale digesters fed with highly variable feed flows and concentrations (up to 6 kgCODm3 day1). The substrate was thermally hydrolyzed activated sludge, and the inoculum for BMP tests was from the full-scale digesters. While identifiability of both parameters in the BMP tests was generally good, only fd could be well identified using continuous data. For khyd using continuous data, normally only a lower limit could be found (upper was unbounded). In addition, parameters as estimated on different outputs (VS and gasflow) and two different digesters were consistent, with an fd value of 0.45– 0.55, and a khyd value of >5 day1. Gradual changes in fd over the 450 days could be related to upstream changes. fd values as estimated in BMP tests were consistent (if conservative)with continuous estimates, with a fd in BMP of 0.4–0.5. khyd values were an order of magnitude lower (0.15– 0.25 day1 vs. >5 day1), and this translated to very poor model performance when BMP-estimated values were used in the continuous model. This means that while BMP testing may be used for project feasibility analysis, values obtained should not be used for dynamic modeling. The parameter confidence regions found were highly nonlinear, especially for continuous systems, indicating that iterative or sampling techniques are required for an estimate of real parameter uncertainty.

Estimation of Hydrolysis Parameters in Full-Scale Anerobic Digesters

Solutions of sulfate have often been used as background electrolytes in the electrochemical degradation of contaminants and have been generally considered inert even when high-oxidation-power anodes such as boron-doped diamond (BDD) were employed. This study examines the role of sulfate by comparing electro-oxidation rates for seven persistent organic contaminants at BDD anodes in sulfate and inert nitrate anolytes. Sulfate yielded electro-oxidation rates 10–15 times higher for all target contaminants compared to the rates of nitrate anolyte. This electrochemical activation of sulfate was also observed at concentrations as low as 1.6 mM, which is relevant for many wastewaters. Electrolysis of diatrizoate in the presence of specific radical quenchers (tert-butanol and methanol) had a similar effect on electro-oxidation rates, illustrating a possible role of the hydroxyl radical (•OH) in the anodic formation of sulfate radical (SO4•–) species. The addition of 0.55 mM persulfate increased the electro-oxidati...

Removal of Persistent Organic Contaminants by Electrochemically Activated Sulfate.

https://espace.library.uq.edu.au/view/UQ:350928/UQ350928_OA.pdf

Stephan Tait

Papers

Technologies to Recover Nutrients from Waste Streams: A Critical Review

Decreasing activated sludge thermal hydrolysis temperature reduces product colour, without decreasing degradability.

Estimation of Hydrolysis Parameters in Full-Scale Anerobic Digesters

Removal of Persistent Organic Contaminants by Electrochemically Activated Sulfate.

Anaerobic co-digestion of pig manure and algae: Impact of intracellular algal products recovery on co-digestion performance