Effect Of Peroxymonosulfate Pretreatment On Short-chain Fatty Acids From Waste Activated Sludge And Its Mechanisms

In the past few decades,with the rapid development of industrialization and urbanization,the amount of urban sewage and industrial wastewater has increased dramatically worldwide.As a cost-effective method,activated sludge method has been widely used in various types of wastewater treatment.In recent years,the production of short-chain fatty acids by sludge anaerobic fermentation is considered to be a high-value and promising way to stabilize sludge and recover resources,which can not only solve the problem of excess sludge treatment and disposal but also take into account the development and utilization of energy.However,traditional sludge fermentation has a low yield of short-chain fatty acids,and it is also unstable.Therefore,many experts have studied many sludge pretreatment technologies to improve the production of short-chain fatty acids.Peroxymonosulfate(PMS),is widely used in numerous industrial processes as bleaching agent,disinfectant and oxidant in organic synthesis because of its powerful oxidative capacity and operation simplicity.In the past,great efforts have been made to use the activation of PMS to produce SR for removing organic pollutants from wastewater(e.g.,pesticides,pharmaceuticals,dyes,aromatics,halogenated olefins,and perfluorinated compounds),or improving disintegration and dewaterability of sludge.However,to date,there have been few reports on the effect of PMS on anaerobic fermentation of sludge.This study proposed that PMS pretreatment of sludge greatly improved the production of short-chain fatty acids.Experimental results showed that the addition of an appropriate amount of PMS promoted the production of short-chain fatty acids during the anaerobic fermentation of sludge,and the maximal SCFAs yield increased from 29.69 to 311.67 mg COD/g VSS with PMS level increasing from 0 to 0.09 g/g TSS.No obvious increase in SCFAs yield was observed when PMS further increased.The mechanism explorations revealed that PMS pretreatment enhanced the disintegration of sludge cells and promoted the biodegradability of organics released,thereby providing more biodegradable substrates for subsequent SCFAs production.PMS pretreatment decreased the percentages of fulvic acid-like and humic acid-like substances in the released organics.Moreover,the species and total detection frequency of other recalcitrant organics such as cyclopentasiloxane,ethylene glycol,norepinephrine and benzaldehyde,which were hardly degraded in ordinary anaerobic condition,also decreased remarkably.Although PMS caused harms to some extents to all the microbes in the anaerobic fermentation,its inhibitions to SCFA s consumers were much severer than that to SCFAs producers,probably due to the less tolerance of methanogens.Further analyses exhibited that PMS would produce some major intermediate products such as K⁺?HSO₅^-?SO₄^·-?·OH and ¹O₂ when added to the fermentation system,¹O₂,SO₄^·-and·OH were the major contributors to the increased SCFAs production,and their contributions were in the order of ¹O₂>SO₄^·->·OH.