Opportunities and challenges in sustainable treatment and resource reuse of sewage sludge: A review

Sludge or waste activated sludge (WAS) generated from wastewater treatment plants may be considered a nuisance. It is a key source for secondary environmental contamination on account of the presence of diverse pollutants (polycyclic aromatic hydrocarbons, dioxins, furans, heavy metals, etc.). Innovative and cost-effective sludge treatment pathways are a prerequisite for the safe and environment-friendly disposal of WAS. This article delivers an assessment of the leading disposal (volume reduction) and energy recovery routes such as anaerobic digestion, incineration, pyrolysis, gasification and enhanced digestion using microbial fuel cell along with their comparative evaluation, to measure their suitability for different sludge compositions and resources availability. Furthermore, the authors shed light on the bio-refinery and resource recovery approaches to extract value added products and nutrients from WAS, and control options for metal elements and micro-pollutants in sewage sludge. Recovery of enzymes, bio-plastics, bio-pesticides, proteins and phosphorus are discussed as a means to visualize sludge as a potential opportunity instead of a nuisance

Oxygen evolution reaction

Oxygen evolution reaction is evinced as one of the main rate-determining steps for clean energy production, energy security supply and therefore for the evolution of a sustainable society. The production of clean energy, the security of energy supply (autonomy) and lower cost of energy supply constitute the main key points for a sustainable future. It is known, that a sustainable future can be achieved only if the current power supply shifts to other sources than the conventional ones; with the renewable energy sources and hydrogen fuel to own a leading role. The oxygen evolution reaction mechanism in acidic and alkaline media remains a mystery even today, after so many years of research activities. Bockris in 1954 and then Bockris and Huq in 1956 were the initial founders of the oxygen evolution reaction mechanism study. Then, many mechanisms were suggested and up-to-date many materials have been studied, with the metal perovskite oxides to be the most promising candidates. When this ‘mystery’ is solved, then a big step towards a sustainable future will become. © Springer Nature Switzerland AG 2020