The influence of a stepwise pH increase on volatile fatty acids production and phosphorus release during Al-waste activated sludge fermentation

Improvement of Methane Production and Sludge Dewaterability by FeCl3-Assisted Anaerobic Digestion of Aluminum Waste-Activated Sludge

“…In recent years, the conventional biological process has not met China’s strict effluent discharge limits. Tertiary treatments, such as adding aluminum (Al) salt, have been implemented to improve the removal efficiency of phosphorus (P), resulting in excess sludge containing Al . In general, the cost of excess sludge treatment, such as thickening, stabilization, dewatering, and disposal, is as high as 30%–60% of the total operating cost of WWTPs .…”

“…Anaerobic digestion (AD) is an effective method for resource utilization and sludge reduction. , During this process, the sludge is hydrolyzed to biodegrade organic matter, converting it to volatile fatty acids (VFAs) or methane. However, the biodegradability of sludge is adversely affected if Al is present in the sludge because the Al coagulants cause floc aggregation in the sludge, preventing the access of hydrolytic enzymes into the flocs. , Several approaches have been developed to break up the aggregated flocs into small flocs to increase the contact area between the surface of the sludge flocs and enzymes to improve the biodegradability of Al sludge during AD . Lin et al found that an alkali pretreatment effectively disintegrated aggregated flocs in Al sludge and improved the sludge’s biodegradability.…”

“…The activated sludge process effectively treats domestic sewage in wastewater treatment plants (WWTPs) and produces wasteactivated sludge (WAS) as a byproduct. 1 As a result of urbanization in China, the wastewater output has sharply increased, leading to large amounts of WAS. By 2020, the annual production of excess sludge with 80% moisture content in China exceeded 40 million tons.…”

“…Tertiary treatments, such as adding aluminum (Al) salt, have been implemented to improve the removal efficiency of phosphorus (P), resulting in excess sludge containing Al. 1 In general, the cost of excess sludge treatment, such as thickening, stabilization, dewatering, and disposal, is as high as 30%−60% of the total operating cost of WWTPs. 2 Therefore, an appropriate sludge treatment is required.…”

“…8 Lin et al 9 found that an alkali pretreatment effectively disintegrated aggregated flocs in Al sludge and improved the sludge's biodegradability. Yan et al 1 investigated the enhancement of biodegradability of Al sludge using longterm acclimation under alkaline conditions, which enable Al dissolution and breaking up the aggregated flocs.…”