Solid Waste As Electron Donors Used For Accelerating Biodegradation Of Pyridine,Quinoline And P-nitrophenol

In industrial wastewater,nitrogenous heterocyclic compounds and phenolic compounds,which require electron donors and molecular oxygen in their key reaction steps,are the main toxic and refractory organics.Low-molecular organics and sugar are generally used as effective electron donors,but such electron donors are increasingly inconsistent with the current concept of wastewater treatment since they are all"resource-based substances" and need high cost.Common municipal solid wastes such as fallen leaves and excess sludge contain a variety of organic substances.However,their traditional treatment methods not only occupy land resources but also cause secondary pollution.In the context of China's deepening construction of ecological civilization,harmless treatment and resource recovery of solid waste must be the main development trend.Therefore,it will be of great practical significance to used solid waste as electron donors to accelerate the biodegradation of industrial wastewater containing refractory organics in combination with the concept of "using waste to treat waste".In this study,three typical refractory organics,pyridine,quinoline and p-nitrophenol,were selected as research obj ects,and fallen leaves leachates and ultrasonic treated sludge were respectively used as exogenous electron donors to accelerate pyridine,quinoline and PNP biodegradation.Moreover,we evaluated the effective electron-donor equivalents provided by such two wastes.On this basis,this study explored the reasons for accelerating pyridine and quinoline biodegradation by fallen leaves leachates through the analysis of the microbial community,and explored the synergistic mechanism between treated and untreated sludge for pyridine and PNP biodegradation through the kinetic model.Main research conclusions obtained in this paper include:(1)Aconsiderable part of the organics leached from the leaves were carboxylic acids,which were easily oxidized,and can be used as an electron donor to accelerate the biodegradation of pyridine and quinoline through co-substrate.With addition of the leachates from Platanus orientalis and Ginkgo biloba linn,the removal rates of pyridine were respectively increased by 4.4%and 3.6%,and the removal rates of quinoline were increased by 9.5%and 11%.When the leaves leachates were illuminated with UV light for 1 h,the removal rates were further increased by up to 7.6%and 8.5%for pyridine and 12%for quinoline,indicating that the acceleration effect was further improved.(2)Based on electron-equivalent balances,and by comparing the acceleration effects of succinate and oxalate on pyridine and quinoline biodegradation,we found that 23%to 98%of the COD from leaves leachates was available as an effective electron donor.UV illumination can hydrolyze the macromolecular organics into more readily biodegradable monosaccharides and small molecular organic acids,which promoted the release of available electron donors in leaves leachates and enhanced the co-substrate effect during the biodegradation of pyridine and quinoline.(3)The result of high-throughput sequencing on the acclimated biomass with and without the leaves leachates added show that both pyridine and quinoline sludge acclimated by Platanus orientalis leachates were dominated by a few bacteria,which had good adaptability to the current environment,whereas the microbial community richness and diversity of quinoline sludge acclimated by Ginkgo biloba linn leachates had been significantly improved.The main effect of the biomass acclimated by leaves leachates was to screen and enrich the bacteria that can use some organics as electron donors and carry out nitrogen conversion,so that the initial mono-oxygenation reactions and subsequent mineralization of pyridine and quinoline can be promoted.(4)The organic matter released from the ultrasonic treated sludge can be used as an electron donor to accelerate the biodegradation of pyridine and PNP.The removal rates of pyridine and PNP were respectively increased by 10%and 21%with the addition of supernatants from treated biomass.When the entire ultrasonic treated biomass was added,the removal rates were increased by 63%for both substrates,and the effects were equivalent to the addition of 0.71 mM and 2.91 mM succinate.The soluble electron donors(present in supernatants of treated biomass)and a large number of colloidal electron donors simultaneously present in entire treated biomass provided more biodegradable electron equivalents able to enhance the acceleration effect on pyridine and PNP biodegradation.This result showed that entire treated biomass was a more effective and lower cost electron donor.(5)Adding ultrasonic treated biomass and untreated biomass together produced a synergistic impact on further accelerating the biodegradation of pyridine and PNP.While the treated biomass increased the concentration of effective electron donors and sludge surface area,the untreated biomass maintained active microorganisms offsetting biomass inactivation.The mixed-first-order models fitted for this synergistic effect:r_pyridine=0.17X_u+0.038(?)+0.19X_t?r_PNP=0.13X_u+0.043(?)+0.16X_t,were consistent with the removal rates of the mixed sludge.