Treatment and disposal of sewage sludge is still a worldwide challenging problem. Improper sludge treatment results in severe environmental impact and endangering public health. Moreover, sewage sludge disposal is a cost-intensive process. Therefore, pathogen removal and solid reduction are indispensable for sludge disposal management. In this study, a novel electrochemical method in alkaline media was developed to break down the sludge structure at room temperature. A reduction of 24.85% in total solids and 46.42% in volatile solids was achieved, which represents approximately a 25% reduction in the sludge disposal cost when compared to conventional treatment methods. Also, a 90% reduction in energy consumption was demonstrated when compared to other electrochemical methods. The post-processed samples characterization showed that a large quantity of organic material was released from the sludge samples into the liquid phase, which indicates the potential to reduce the residence time in anaerobic digesters and to generate more biogas. The proposed treatment demonstrated the feasibility of pathogen removal and biosolid production for safe landfilling or agriculture applications such as fertilizers.

A tremendous amount of waste activated sludge (WAS) ends up in landfilling even after a substantial retention time during anaerobic digestion. This leftover activated sludge is an organic-rich material with the high potential to produce value-added chemicals such as short chain fatty acids (SCFAs). In the present study, a novel electrochemical conversion of activated sludge (E-WAS) was carried out on the surface of non-precious electrodes (nickel, stainless-steel and copper) in alkaline media at low applied potential and temperature. Cyclic voltammetry showed that Cu (II)/Cu (III) and Ni (II)/Ni(III) redox couple catalyzed the WAS oxidation reaction to produce SCFAs and hydrogen. The results revealed that Cu(II)/Cu(III) has higher catalytic oxidation capability towards SCFAs. Yields of 48.7, 21.4, and 14.6 mg SCFAs per g of volatile solids were achieved by using copper, nickel and stainless-steel as working electrodes, respectively. Post analysis characterization techniques indicate that copper oxide films lead to WAS oxidation. Total volatile solid removal of 30% was obtained at 35°C and 1.65 V in 0.2 M NaOH after 2 h of operation in an electrochemical digestor with copper electrodes which is more efficient than a conventional alkaline treatment (24 h, 55%, 1M NaOH). Ammonia was produced as the by-product of E-WAS oxidation. The highest amount of ammonia (250 mg L−1) was obtained by using nickel as the working electrode after 2 h operation at 35°C and 1.35 V applied potential. The change in WAS morphology revealed that the copper oxide film is an effective electrocatalyst for WAS disinfection.

Solid waste mismanagement causes environmental contamination. Sewage sludge is the byproduct of the wastewater treatment process and contains pathogenic organisms (e.g Salmonella spp., Escherichia coli, etc.). Anaerobic digestion is widely used for sewage sludge treatment. However, the major drawback of this process is the sluggish rate of sludge biodegradation. Therefore, the retention time in the typical digester is long (between 20-30 days) which consequently results in substantial energy consumption. On the other hand, approximately 50- 60 % of the operational cost in the wastewater treatment plant is dedicated to the treatment and disposal of waste. Hence, it is essential to develop a treatment method to decrease energy consumption. Alkaline treatment is an attractive process for sludge destruction and improvement in the sludge biodegradability. Furthermore, electrochemical oxidation of the organic materials is an environmentally friendly alternative pathway to disintegrate the sludge microbial cells and eliminate the pathogen bacteria from biosolid for safe disposal. Therefore, the combined alkaline electrochemical technique could expedite waste degradation by using the synergetic functions and increase efficiency of the treatment. To overcome the challenges related to the conventional treatment method, our research group has developed a novel, energy-efficient mixed alkali-electrochemical sludge treatment in a membraneless electrochemical system at room temperature and low applied potential. In this study, the bimetallic (platinum-iridium) nanocatalyst was synthesized with modified polyol method. The thermal behavior of the raw sludge and the residue biosolid after electrolysis was evaluated by using thermogravimetric analysis (TGA). To determine the effect of electrolysis on the chemical structure of biosolid, the Fourier-transform infrared spectroscopy-Attenuated Total Reflection (FTIR-ATR) and elemental analysis techniques were applied. Ammonia was produced as a byproduct of the waste treatment which can be converted to hydrogen through electrolysis. A considerable amount of solid reduction was achieved by implementing a short electrolysis treatment which diminished the waste transportation and disposal cost to a large extend. Furthermore, the energy consumption was significantly lower than the previous research studies. In this presentation, results from this study including (i) the electrochemical performance of catalyst for sewage sludge treatment (ii) pathogen disinfection and (iii) biosolid characterization will be provided.

During the wastewater biological treatment process, a significant amount of waste activated sludge (WAS) is produced, which must be properly treated before disposal. The cost of WAS disposal accounted for nearly 50–60% of a wastewater treatment plant’s operating costs. The disposal of a large amount of WAS has become a serious environmental and economic problem as wastewater treatment capacity has increased. Furthermore, WAS has been considered as a sustainable resource due to a high organic matter content (>40%, mainly proteins, and carbohydrates) with an average calorific value of 6094 kcal/kg. As a result, harnessing bioenergy from WAS could resolve both environmental and economic issues raised by the growing amount of WAS.The intermediate chemicals in anaerobic digestion are short-chain fatty acids (SCFAs) (e.g., acetic acid, propionic acid, butyric acid, etc.). SCFAs are more beneficial (600-3815$/ton) than biogas (150$/ton) and produced in a shorter period (less than 2d). SCFAs production from waste activated sludge is getting popular in wastewater treatment plants (WWTPs) because SCFAs can be used for a variety of applications, including biohydrogen production, bioplastics (polyhydroxyalkanoate (PHA), and biological nutrient removal.Electrochemical treatment has been shown to be a powerful and environmentally friendly method of disrupting sludge floc and sludge disintegration to create SCFAs by oxidizing complex organic compounds on the electrode surface. On the other hand, the alkaline pH is more favorable for protein and carbohydrate destruction which results in a substantial increase in SCFAs production. Furthermore, methanogenesis reactions are mitigated in alkaline media, so that more SCFAs accumulate as a final product.In this study, the electrochemical treatment under an alkaline environment was utilized in a single chamber electrolysis cell at low operating temperatures (25-55 °C) to achieve solid reduction and SCFAs production. The effect of the operating condition such as applied potential, electrode materials, operating temperature, and alkaline agent concentration on SCFAs production was investigated. The waste activated sludge solid before and after treatment was characterized by thermogravimetric analysis (TGA), Scanning electron microscope (SEM), and elemental analysis techniques. The supernatant liquid after electrochemical treatment was evaluated with gas chromatography- flame ionization detector (GC-FID) to analyze the SCFAs concentration. In this presentation, the results from this research study will be provided including volatile solid removal, SCFAs concentration, and solid residue characterization.