Analysis of Reject Water Formed in the Mechanical Dewatering Process of Digested Sludge Conditioned by Physical and Chemical Methods

Reverse Solute Diffusion Enhances Sludge Dewatering in Dead-End Forward Osmosis

Wastewater treatment plants produce high quantities of excess sludge. However, traditional sludge dewatering technology has high energy consumption and occupies a large area. Dead-end forward osmosis (DEFO) is an efficient and energy-saving deep dewatering technology for sludge. In this study, the reverse osmosis of salt ions in the draw solution was used to change the sludge cake structure and further reduce its moisture content in cake by releasing the bound water in cell. Three salts, NaCl, KCl, and CaCl2, were added to the excess sludge feed solution to explore the roles of the reverse osmosis of draw solutes in DEFO. When the added quantities of NaCl and CaCl2 were 15 and 10 mM, respectively, the moisture content of the sludge after dewatering decreased from 98.1% to 79.7% and 67.3%, respectively. However, KCl did not improve the sludge dewatering performance because of the "high K and low Na" phenomenon in biological cells. The water flux increased significantly for the binary draw solute involving NaCl and CaCl2 compared to the single draw solute. The extracellular polymer substances in the sludge changed the structure of the filter cake to improve the formation of water channels and decrease osmosis resistance, resulting in an increase in sludge dewatering efficiency. These findings provide support for improving the sludge dewatering performance of DEFO.

Possibilities of Managing Waste Iron Sorbent FFH after CO2 Capture as an Element of a Circular Economy

With a growing need to reduce greenhouse gas emissions, innovative carbon dioxide sorbents are being sought. One of the sorbents being tested is nanoparticle ferric hydrosol (FFH). In parallel with sorbent testing, it is also necessary to test the used sorbent after carbon dioxide capture (FFHCO2) and to develop an optimal method for its processing and management. The research described in this article evaluated the potential use of FFHCO2 in dewatering, coagulation and bioleaching processes. The research results indicate that the basic strategy for dealing with waste FFHCO2 sorbent should be to minimize the amount of waste by volume reduction-dewatering. Recycling of FFHCO2 as an iron waste coagulant or its processing products by bioleaching had no technological justification. It is only proposed to recover the material-iron compounds-if it is environmentally and economically justified.

Optimizing sludge dewatering efficiency with ultrasonic Treatment: Insights into Parameters, Effects, and microstructural changes

Sludge dewatering plays a critical role in the efficient and cost-effective management of wastewater treatment plants. Ultrasonic treatment has emerged as a promising technique for improving dewatering processes. This study aims to evaluate the impact of ultrasonic treatment on sludge dewatering characteristics. A series of experiments were conducted to evaluate the dewatering characteristics of sludge under ultrasonic treatment. Experimental data was collected, and the effects of ultrasonic parameters on dewatering efficiency were analyzed. Ultrasound has the capacity to disintegrate sludge flocs, liberate tightly bound water, and enhance sludge dewatering capabilities. The application of ultrasound leads to the breakdown of sludge flocs, which facilitates a substantial amount of organic acids or carbonates. This, in turn, modifies the pH value of the sludge. Additionally, ultrasound induces instantaneous high temperature and pressure within the liquid phase, consequently elevating the temperature of the sludge slurry. Optimum ultrasound energy density and duration of ultrasound treatment exist. For the sludge samples analyzed in this investigation, it was determined that the optimal ultrasonic energy density is 9.8 W, while the optimal duration of ultrasound treatment is 30 s. Excessively escalating the sound energy density or prolonging the duration of ultrasound may yield unfavorable outcomes in terms of sludge dewatering effectiveness. To enhance sludge dewatering, it is crucial to select appropriate ultrasonic energy density and duration of ultrasonic treatment. This study demonstrates the positive impact of ultrasonic treatment on the dewatering characteristics of sludge. The findings provide valuable insights into the potential of ultrasonic technology for enhancing sludge dewatering.

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.