Klebsiella Combined With Biochar To Remove Polyacrylamide From Soil

Polyacrylamide(PAM)has a wide range of applications in many industries due to its high molecular weight and high viscosity.In this paper,a strain of PAM degrading bacteria with PAM as the sole carbon source and the sole nitrogen source was screened from sludge.After morphological,physiological,biochemical and molecular biological identification,the strain was identified as genus Klebsiella.The growth and degradation conditions of PCX were studied.Suitable culture conditions of PCX are PAM concentration in the range of 0.6?2.4 g/L,pH in the range of 5.0?7.0,temperature in the range of 20?40 ?,and the metal ions Na+,Mg2+and Ca2+.The degradation rate of PAM reached 43%without adding nitrogen and carbon sources under the conditions of inoculum concentration 5%(v/v),PAM concentration 1.2 g/L,35?,and 7.0 of initial pH.The results of gel permeation chromatography and infrared spectrum analysis of PAM degradation products showed that the molecular weight decreased from 3×106 Da to 619 Da after degradation,and the amide group on the molecular chain hydrolyzed to carboxyl group,and the side chain degraded,and some functional groups changed.Bio-acute toxicity of degradation products was analyzed.The median effect concentration(EC50)was 106 mg/L.According to the classification of chemicals toxicity given by EU Directive 93/67/EEC,degradation products can be considered as nontoxic to aquatic organisms.Using straw,chicken manure,coconut shell,activated sludge and coconut shell,straw and sludge mixed material as raw materials,the biochar was prepared by slow pyrolysis,scanning electron microscopy showed that the surface of biochar had uneven porous structure,and the pore was widely distributed,part of pores showed parallel slit-like pore structure.Coconut shell-sludge biochar was selected as the carrier for PCX due to the high yield(47.5%)and iodine adsorption value(672 mg/g).Scanning electron microscopy of immobilized bacteria showed that PCX was not only distributed on the surface of biochar,but also filled with the pore structure of biochar,and PCX loaded on biochar was 1010 cfu/g.In the experiment of treating PAM-containing soil,after 38 days,the degradation rates of PAM in sterilization,indigenous bacteria,added bacteria,added biochar,added biochar and bacteria separately and added immobilized bacteria,were 8.2%,21%,49.2%,54.5%,64%and 78%respectively.Response Surface Methodology(RSM)was used to optimize the treatment conditions of PAM contaminated soil by immobilized bacteria.Variance analysis and contour plot showed that there was a strong interaction between immobilized bacteria dosage and temperature.Soil pH has a significant impact in the degradation of PAM.According to the second-order model,the optimum conditions for the degradation of PAM in soil by immobilized bacteria were pH 5,immobilized bacteria dosage 0.07 g/g and 38.88?.Under these conditions,the degradation rate of PAM in soil was 74%after treated 30 days.