Ferric chloride aiding nitrite pretreatment for the enhancement of the quantity and quality of short-chain fatty acids production in waste activated sludge

Novel Insights into the Mechanisms of Periodate-Based Pretreatment in Enhancing Short-Chain Fatty Acids from Waste Activated Sludge

“…2 Generally, sludge solubilization and hydrolysis can be expressed by the release of SCOD, soluble proteins, and polysaccharides. 5 Figure 3A shows the changes in the SCOD concentrations; analogous to the changes in SCFA generation, SCOD concentrations were higher than those in the control. For instance, the maximal release of SCOD from WAS with 50 mg PI/g TS was 3330 ± 196.5 mg/L, which was enhanced by 57.1% compared to that of the control (2120 ± 106 mg/L).…”

“…During the acidogenic fermentation, the solubilization and hydrolysis of WAS simultaneously occur, while these two steps are viewed as the rate-limiting procedures . Generally, sludge solubilization and hydrolysis can be expressed by the release of SCOD, soluble proteins, and polysaccharides Figure A shows the changes in the SCOD concentrations; analogous to the changes in SCFA generation, SCOD concentrations were higher than those in the control.…”

“…Anaerobic fermentation of WAS for generating short-chain fatty acids (SCFAs) is considered a promising technique for sludge reduction and resource recovery, 2 by which the organics in WAS can be transformed into high-value products for synthesizing biodegradable polymers (such as polyhydroxyalkanoates), alleviating the shortage of carbon sources in MWTP and recovering energy (e.g., biogas and biodiesel). 3,4 However, the generation of SCFAs is generally restricted by the complex structure of the sludge, the rapid consumption of hydrolyzed or acidified products by methanogens, 5 and poor biodegradation of WAS due to the existence of massive recalcitrant organics. 6 Among these recalcitrant materials, humus and lignocellulose were documented as accounting for 30 and 14−44% of the whole organics in raw WAS.…”

“…Sludge disposal gives both an opportunity and challenge for municipal wastewater treatment plants (MWTPs) because WAS possesses the dual attributes of “pollution” and “resource”. Anaerobic fermentation of WAS for generating short-chain fatty acids (SCFAs) is considered a promising technique for sludge reduction and resource recovery, by which the organics in WAS can be transformed into high-value products for synthesizing biodegradable polymers (such as polyhydroxyalkanoates), alleviating the shortage of carbon sources in MWTP and recovering energy (e.g., biogas and biodiesel). , However, the generation of SCFAs is generally restricted by the complex structure of the sludge, the rapid consumption of hydrolyzed or acidified products by methanogens, and poor biodegradation of WAS due to the existence of massive recalcitrant organics . Among these recalcitrant materials, humus and lignocellulose were documented as accounting for 30 and 14–44% of the whole organics in raw WAS. , However, these organics could not be utilized by anaerobes for SCFA production in the traditional fermentation system due to the difficulty in biodegrading the steady polymers or tight condensation of oxygenous groups contained in these materials …”

“…However, the in-depth mechanism of PI-based sludge treatment was a “black box” and further applications of PI on sludge treatment were worth being discovered. Given that the poor fermentation efficiency was generally ascribed to EPS restrictions on the intracellular organics solubilization, , the possibility of enhancing the SCFA yield through PI pretreatment could be expected. Notwithstanding, the effects of PI pretreatment on the performance of SCFA production in anaerobic fermentation are a long-awaited information.…”