Anaerobic co-digestion of the process water from waste activated sludge hydrothermally treated with primary sewage sludge. A new approach for sewage sludge management

Abstract

Hydrothermal carbonization (HTC) is a suitable technology for managing wastes with a high moisture content, providing a carbon-rich and high energy density material called hydrochar and a process water (PW) with significant organic matter content. The aim of this work was to develop a new approach to sewage sludge management involving anaerobic digestion (AD) of the PW of dewatered waste activated sludge (DWAS) with primary sewage sludge (PSS). The process was optimized by performing semi-continuous experiments with different feed mixture compositions (10% PW/90% PSS and 5% PW/95% PSS, on a COD basis), organic loading rates (OLR; 1.5 and 2.5 g COD L -1 d -1 ), and temperature regimes (mesophilic and thermophilic). The combination of mesophilic conditions, a 10% PW/ 90% PSS feed mixture and OLR of 1.5 g COD L -1 d -1 provided concentrations of volatile fatty acids < 400 mg COD L -1 in addition to a methane yield (172 ± 11 mL CH4 g -1 CODadded), 1.15 times the value for the control test (100% PSS). Therefore, the energy content of hydrochar from HTC of DWAS followed by AD of the process water with primary sewage sludge enhances the valorization of this renewable residue.

Hydrochar derived from municipal sludge through hydrothermal processing: A critical review on its formation, characterization, and valorization

“…Fig.16Characteristics of aqueous phase from hydrothermal carbonization (HTC) and liquefaction (HTL) of various sludge(Ahmed et al, 2021a;Aragón-Briceño et al, 2017Belete et al, 2019;Chen et al, 2019;Ferrentino et al, 2020b;Gaur et al, 2020;Lu et al, 2017;Maddi et al, 2017;Marin-Batista et al, 2020;Marrone et al, 2018;Merzari et al, 2020;Ovsyannikova et al, 2020;Snowden-Swan et al, 2017;Villamil et al, 2019Villamil et al, , 2020Xu et al, 2020aXu et al, , 2020b. PS = primary sludge; SS = secondary sludge; MPS = mixed PS and SS; DS = digested sludge; COD = chemical oxygen demand; TOC = total organic carbon; TN = total nitrogen; TP = total phosphorus.…”

A Review on Sewage Sludge Valorization via Hydrothermal Carbonization and Applications for Circular Economy

“…The energy recovery rate is 41.5%. Emphasis is made to further modelling and design for large scale HTC plants (Villamil et al 2020b).…”

Effect of Thermal Hydrolysis Pretreatment on Anaerobic Digestion of Protein-Rich Biowaste: Process Performance and Microbial Community Structures Shift

“…Therefore, it is necessary and important to study the response of the AD system to excessive AN as well as the mitigation measures to the possible inhibition. After all, it is necessary for some protein-rich substrates to be subjected to THPT, e.g., for municipal sludge containing protein granule substrate and high protein content EPSs to enhance their biochemical properties (Villamil et al, 2020), and for (several million tons of) antibiotic mycelial residues to eliminate inhibition of antibiotics left in them (Zhang et al, 2015). That is, it is still essential to develop the technology of THPT combined with AD for the specific biowaste potential for biogas production.…”