Enhancement of sludge dewaterability by three-dimensional electrolysis with sludge-based particle electrodes

Enhanced sludge solubilization by a fluidized electrode: Granular activated carbon promoted electrochemical oxidation

Electrochemical sludge pretreatment is receiving increasing attention because of its small footprint and higher environmental compatibility. However, the limited effective area of electrode plates and the low conductivity of sludge hinder the widespread application of electrochemical pretreatment. In this study, granular activated carbon (GAC) was employed to construct a fluidized electrode electrochemical system (FEE) to promote electrochemical pretreatment. Under the optimal operating parameters, the FEE system could effectively facilitate sludge decomposition, indicated by 126% increase in soluble chemical oxygen demand (SCOD) and 23.1% reduction in sludge volume. Mechanism study revealed that the addition of GAC significantly enhanced the conductivity of sludge, thereby promoting the oxidation capacity of FEE system. Furthermore, continuously generated H2O2 in FEE further promoted sludge solubilization. GAC offered an effectively, green and sustainable enhancement approach for sludge electrochemical pretreatment.

Harmless and resourceful utilization of solid waste: Multi physical field regulation in the microbiological treatment process of solid waste treatment

Solid waste (SW) treatment methods mainly include physical, chemical, and biological methods, while physical and chemical methods have advantages such as fast effectiveness and short treatment time, but have high costs and were prone to secondary pollution. Due to the advantages of mild conditions and environmental protection, microbial methods have attracted the attention of numerous researchers. Recently, promotion of biological metabolic activity in biotreatment technology by applying multiple physical conditions, and reducing the biochemical reaction energy base to promote the transfer of protons and electrons, has made significant progress in harmless and resourceful utilization of SW. This paper main summarized the harmless and resourceful treatment methods of common bulk SW. The research of physical field-enhanced microbial treatment of inorganic solid waste (ISW) and organic solid waste (OSW) was discussed. The advantages and mechanisms of microbial treatment compared to traditional SW treatment methods were analyzed. The multi-physical field coupling enhanced microbial treatment technology was proposed to further improving the efficiency of large-scale treatment of bulk SW. The application prospects and potential opportunities of this technology were analyzed. Novel research ideas for the large-scale harmless and resourceful treatment of bulk SW were provided.

Coupling sludge-based biochar and electrolysis for conditioning and dewatering of sewage sludge: Effect of char properties

The addition of sludge-based biochar during electrochemical pretreatment of sewage sludge, as an efficient hybrid technology, is potentially to be applied in sludge deep-dewatering. The chars functioned as conductors, catalysts and skeleton particles could enhance the sludge dewaterability and increase the calorific value of the dewatered sludge cake. However, the effect of synthesis conditions on the char properties and further on the dewatering performance is still unknown. Herein, the sludge-based particle electrodes (SPEs) under three main synthesis conditions, including liquid-solid ratio, pyrolysis temperature and time, were prepared. The sludge-based biochars (i.e., SPE-400, SPE-600, and SPE-800 pyrolyzed under 400, 600 and 800 °C, respectively) were characterized and utilized as three-dimensional electrodes during sludge electrolysis. The increased pyrolysis temperature (within 400-800 °C) resulted in the enrichment of metallic ions and increment of specific surface area and pore volume of SPE, which led to the increased catalysis and adsorption sites for viscous proteins (PNs). Particularly, the pores of SPE-800 provided more drainage channels as skeleton builders. Compared with raw sludge, the capillary suction time (CST) and the specific resistance of filtration (SRF) of the treated sludge with 3D-SPE-800 were reduced by 58.12% and 81.01%, respectively, but the net sludge solids yield (Y_N) was increased by 87.05%. The highest decrease of hydrophilic α-Helix content in PNs (from 9.93% to 7.30%) was observed when using SPE-800 as particle electrode, revealing the crucial role of char characteristics on protein reduction and subsequent dewatering enhancement. The synergistic effects of electrolysis and sludge-based biochar provided a new insight for a closed-loop pretreatment of sewage sludge in the wastewater treatment plant.

Application of Advanced Oxidation Technology in Sludge Conditioning and Dewatering: A Critical Review

Sludge dewatering is an important link in sludge treatment. In practical engineering, the dewatering effect of unconditioned sludge is very poor. The use of advanced oxidation technology can improve sludge dewatering performance, reduce sludge capacity, and remove micro-pollutants, which is beneficial for sludge post-treatment and disposal. Based on the current status of sludge conditioning and dehydration, the characteristics of the advanced oxidation method for sludge dehydration were systematically explained using various free radical reaction mechanisms and dehydration conditions. The effects of various advanced oxidation technologies on sludge conditioning and dewatering has been extensively discussed. Finally, the application prospects of the advanced oxidation technology in sludge conditioning and dewatering are presented.

A novel conditioning approach for amelioration of sludge dewaterability using activated carbon strengthening electrochemical oxidation and realized mechanism

Sludge dewatering is an essential process for reduction of sludge volume to decrease cost of ultimate disposal. In this study, a novel method using activated carbon (AC) strengthening electrochemical (EC) treatment (EC/AC) was adopted to improve greatly sludge dewaterability. It was shown that capillary suction time (CST) and water content of dewatered sludge cake (Wc) were reduced to 55.9 ± 1.24 s and 64.3 ± 1.23%, respectively, under the optimal conditions of EC voltage 20 V, EC time 30 min and 0.2 g/g dry solid (DS) AC. AC with rich functional groups as "the third electrode" intensified electrooxidation by forming multiple microelectrodes and electron transfer capacity and conductivity of sludge were strengthened by AC in EC system, which were illustrated by electrochemical analysis. It could be found that zeta potential and particle size were increased and surface roughness was reduced after EC/AC treatment intensifying sludge hydrophobicity. Form the results of rheological behaviors of sludge, flowability was strengthened and viscosity was weakened under the conditioning of EC/AC. Besides, colloidal force and gel-like network strength were lessened, which was also verified by organic matters and percentage of inviable cells. At the same time, intracellular matters were released and degraded and bound water was released converting into free water. In addition, sludge compressibility and structural strength were increased and porous structure was formed facilitating water outflow via addition of mesoporous AC as skeleton builder, which eventually led to an improved separation efficiency of solid-water and sludge dewaterability. The results of heavy metals suggested that sludge cake after EC/AC treatment was favorable for land application.