Abstract
The high moisture content present in sewage sludge hinders the use of sewage sludge in incineration or energy application. This limitation of moisture present in sewage sludge can be obviated by using the hydrothermal carbonization (HTC) process. In sewage sludge management, the HTC process requires less energy compared to other conventional thermo–chemical management processes. The HTC process produces energy-rich hydrochar products and simultaneously enables phosphorus recovery. This study investigates the influence of organic acids, inorganic acid, and alkali as additives on phosphorus transformation, yield, proximate analysis and the heating value of subsequently produced hydrochar. The analysis includes various process temperatures (200 °C, 220 °C, and 240 °C) in the presence of deionized water, acids (0.1 M and 0.25 M; H2SO4, HCOOH, CH3COOH), and alkali (0.1 M and 0.25 M; NaOH) solutions as feed water. The results show that phosphorus leaching into the process-water, hydrochar yield, proximate analysis, and the heating value of produced hydrochar is pH- and temperature-dependent, and particularly significant in the presence of H2SO4. In contrast, utilization of H2SO4 and NaOH as an additive has a negative influence on the heating value of produced hydrochar.
Highlights
Accepted: 29 March 2021The management of sewage sludge produced from wastewater treatment plants is an important global issue due to the presence of high moisture content, harmful pathogens, and poor dewaterability
The results showed that during the hydrothermal carbonization (HTC) of sewage sludge, metal cations and pH played vital roles in the transformation of phosphorus
The analysis demonstrates noticeably lower ash content of 32.83% dry matter (DM) and higher volatile solids (VS) of 61.46% DM, which was inconsistent with the previous investigation ranges [6,23]
Summary
Accepted: 29 March 2021The management of sewage sludge produced from wastewater treatment plants is an important global issue due to the presence of high moisture content, harmful pathogens, and poor dewaterability. Conventional sewage sludge management involves the direct application on farmland as fertilizer. 2018, about 23% of sewage sludge produced in Germany was managed by applying directly on farmland, and about 65% of the produced sewage sludge was incinerated [3]. Since 2017, new regulation was placed by the German sewage sludge ordinance (AbfKlärV) based on enabling principles of the Circular Economy Act [4] on sewage sludge management. This new regulation is making it mandatory to recover phosphorus from sewage sludge in Germany and prohibits the direct use of sewage sludge on farmland [5]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
