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Solids processing and disposal
Published in Rumana Riffat, Taqsim Husnain, Fundamentals of Wastewater Treatment and Engineering, 2022
In the CambiTM process, primary and secondary sludge is dewatered to approximately 17% solids before entering a pulping vessel. In the pulping vessel, the mixed sludge is heated to approximately 80°C, and then transferred to the thermal hydrolysis digester vessel, where it is heated to 160°C at a pressure of approximately 5.5 bar for 15–30 minutes. After digestion, the sludge is released to a flash tank which is at atmospheric pressure. The pressure drop between the digester and the flash tank causes cell lysis and a decrease in temperature to 100°C. A series of heat recovery and heat transfer systems are required to optimize the energy use of the process. Sludge in the flash tank is diluted with treated effluent to ensure that the solids concentration in the digester is not excessive. Figure 12.12 provides a flow diagram of the CambiTM process. After thermal hydrolysis the viscosity of sludge is significantly reduced, thus allowing the digester to be operated at solids concentrations of about 9%. The digester sizes can be significantly reduced in the CambiTM process.
Vacuum-assisted thermal drying of wastewater treatment sludge
Published in Journal of the Air & Waste Management Association, 2021
Yasar Avsar, Arslan Saral, Fatih Ilhan, Bahar Akyuz, Mustafa Talha Gonullu
Providing thermal energy is necessary if dehydrating the sludge is needed. In the future, heat drying techniques are expected to be the leading methods for the drying of municipal or industrial sludge. As an advanced deep dehydration technique, heat drying has been used worldwide. The method using only electric heating to reduce water content of sludge is not viable in regard to the energy economy. To make this method more useful or considerable in terms of energy consumption, reduced pressure conditions could be used so that the evaporation temperature of water is reduced under vacuum conditions resulting in lower energy consumption. The underlying reason is thought to be the fact that thermal hydrolysis involves the use of heat and/or pressure treatment improves sludge digestibility (Jumoke et al. 2019). In another study under vacuum conditions at 40°C–80°C temperatures activated sludge reached at high solid dry ratio (Hippinen and Ahtila 2004).
Sludge: next paradigm for enzyme extraction and energy generation
Published in Preparative Biochemistry and Biotechnology, 2019
Santosh Kumar Karn, Awanish Kumar
Thermal hydrolysis or hydrothermal treatment is a process in which the sludge is heated as an aqueous phase to temperatures varying between 120 °C and 400 °C.[31] The primary aim of sludge thermal hydrolysis is to get useful resources like fatty acids, phosphorous, biogas, etc.[54] Depending upon the primary aim, there are several modifications in the process. The potential of hydrothermal treatment for the recovery of energy from sludge can also be done and depends upon the process performance strongly. Volatile fatty acids and other biodegradable dissolved organic compounds can be constructively used as an energy or organic carbon source in the anaerobic digestion step or in the denitrification step of the wastewater treatment process. Heat necessary to increase the temperature of the sludge can easily be recovered and reused by application of heat exchangers. However, it is not clear what happens to the toxic substance associated with sludge. An intensive post-treatment will be necessary to solve the different problems and issues with sludge.
Evaluation of impact of sludge types and solids content on sludge treatment using microwave enhanced advanced oxidation process
Published in Environmental Technology, 2023
Moutoshi Saha, Asha Srinivasan, Ping Huang Liao, Kwang Victor Lo
Sewage sludge, which is rich in organics and nutrients, can be converted to biogas production via anaerobic digestion and valuable products through nutrient recovery processes. Anaerobic digestion has been established as a cost efficient and sustainable sludge treatment technology [8]. However, it is a slow process and requires high retention time and a larger digester volume. Pre-treatment of sewage sludge can help to increase the anaerobic digestion rate, reduce retention time and digester volume requirement by enhancing microbial cell lysis and the biodegradability of organic matter [9,8,10]. Pre-treatment would increase organic solids solubilization, nutrient release from sewage sludge, resource and energy recovery, and produce biosolid to comply with the regulations [10]. Researchers have studied various sludge pre-treatment technologies including mechanical, thermal, chemical, and biological treatment [11–18]. Among these methods, thermal hydrolysis is one of the most widely used method. During thermal hydrolysis, temperature of sludge is increased to a desired level by applying heat to enhance disintegration and solubilization of sludge cells [7]. Thermal hydrolysis helps to increase sludge dewaterability [19], biogas production [20], biodegradability, pathogen destruction and odour reduction [21–24]. Combination of thermal hydrolysis with chemicals including ozone, hydrogen peroxide, acids or alkali, known as thermo-chemical pre-treatment process, can also be applied to treat sludge. Studies showed that volatile suspended solids solubilization and methane production were higher for thermo-chemical pre-treatment than individual thermal or chemical pre-treatment [25,26].