Steam Explosion Pretreatment of Sludge for Pharmaceutical Removal and Heavy Metal Release to Improve Biodegradability and Biogas Production

Abstract

Steam explosion pretreatment was developed and evaluated to remove pharmaceuticals and heavy metals from wastewater sludge and to improve its biodegradability and methane yield. Effects of pressure (5–15 bar) and duration (1–15 min) during the pretreatment were examined, and the pretreatment efficiency was evaluated based on the solubilization degree, the capillary suction time (CST) test and anaerobic digestion. The removal efficiency of ibuprofen, acetaminophen, and amoxicillin was 65%, 69%, and 66% and 70%, 66%, and 70% in primary sludge (PS) and waste-activated sludge (WAS), respectively. The highest percent release efficiency of heavy metals, i.e., lead, cadmium, and silver, for PS and WAS was 78%, 70%, and 79% and 79%, 80%, and 75%, respectively. The highest methane yield was obtained after pretreatment at 10 bar for 15 min and at 15 bar for 10 min, with respective yields of 380 and 358 mL CH4/g volatile solids (VS) for the PS and 315 and 334 mL CH4/g VS for the WAS. The results of methane production indicated that the decreased concentrations of pharmaceuticals and heavy metals resulted in increased biodegradability of PS and WAS.

Sewage sludge pretreatment: current status and future prospects

“…This approach employs high pressure and heat causing break down of sludge structures and contained compounds. The steam explosion eliminates the need for chemical usage; hence, it can be considered as an eco-friendly pretreatment method (Aski et al 2020 ). Aski et al ( 2020 ) confirmed that this method allowed for pharmaceutical and heavy metal removal, such as ibuprofen (in 65 and 69%), acetaminophen (in 66 and 70%), amoxicillin (in 66 and 70%), lead (in 78 and 70%), and cadmium (in 79%) removal from primary sludge and waste-activated sludge by facilitating the leaching them out into the liquid phase.…”

“…The steam explosion eliminates the need for chemical usage; hence, it can be considered as an eco-friendly pretreatment method (Aski et al 2020 ). Aski et al ( 2020 ) confirmed that this method allowed for pharmaceutical and heavy metal removal, such as ibuprofen (in 65 and 69%), acetaminophen (in 66 and 70%), amoxicillin (in 66 and 70%), lead (in 78 and 70%), and cadmium (in 79%) removal from primary sludge and waste-activated sludge by facilitating the leaching them out into the liquid phase. Physical pretreatment methods can be applied to sewage sludge pretreatment, as well as reduction of dangerous impact of pharmaceuticals, antibiotics, and heavy metals.…”

“…Sewage sludges are composed of organic macromolecule compounds, varying in concentration and proportion. Wastewater flowing into WWTP is not only from private households but also from breweries, dairy factories, and paper industries, to name a few (Aski et al 2020 ), which dictate the high concentration of lipids, proteins, cellulose and hemicellulose, and other polysaccharides in wastewater and then in sewage sludge. All sewage sludges are produced during wastewater treatment; hence, the composition of the sewage sludge is directly related to the composition of the wastewater that goes directly into the wastewater treatment plant.…”

Biohythane Production from Domestic Wastewater Sludge and Cow Dung Mixture Using Two-Step Anaerobic Fermentation Process

“…pH is an important factor in bioH 2 production because it affects the activities of enzymes involved in the process [22]. If the pH is too low (acidic), the enzymes responsible for bioH 2 production may become less effective and cause a reduction in bioH 2 production [23]. If the pH is too high (alkaline), the enzymes responsible for bioH 2 production may become inactivated and cause a reduction in bioH 2 production [19].…”

“…Several experimental studies were previously performed on biogas containing bioCH 4 and CO 2 from cow dung with waste sludge where only bioCH 4 , CO 2 or volatile solid content was used [20,21]. On the other hand, some other studies only focused on bioH 2 from cattle wastewater [22] and cattle manure [23]. Based on the yield of these earlier studies, the yield of bioCH 4 with CO 2 is higher than bioH 2 , but the energy content of bioH 2 (~120 MJ/kg) is higher than bioCH 4 (~20-30 MJ/kg).…”