| Sludge anaerobic digestion can stabilize the sludge and produce clean energy-biogas.Anaerobic digestion is one kind of prefered process for sludge treatment in wastewater treatmentplant, as it can effectively realize the reduction, stabilization, harmlessness and resource reuse ofsludge. However, the H2S generated during the anaerobic digestion will restrain the digestionprocess with affecting the metabolic activity of anaerobic bacteria. The H2S in biogas will reduce theeffective use of the biogas. So it is necessary to adopt some measures to restrain the generation ofH2S.Sludge anaerobic digestion experiments were carried out under the mesophilic conditions. TheFeCl3or PAC was dosed into the digester, to study the effect of FeCl3or PAC dosing on anaerobicdigestion of sludge, and to study the removal efficiency of FeCl3or PAC on the H2S in the biogas.The biogas production, the biogas composition, the hydrogen sulfide （H2S） content of the biogas, aswell as the pH, the total solids （TS） and the volatile solids （VS） were investigated in theseexperiments. The aim was to improve the quality of the biogas, and use the redundant resourse ofcoagulant from the wastewater treatment reasonably.（1） FeCl3had positive impact on sludge anaerobic digestion, while PAC negatively impacted theAD （anaerobic digestion）. The results showed that, when the sludge entered a stable phase, biogasproduction of per gram of VS in blank digester was about249.99mL/gVS, when the concentration ofFeCl3were54mg/L,72mg/L,90mg/L,120mg/L,150mg/L, the biogas production per gram of VSwere1.82%、3.80%、3.25%、6.67%、12.02%higher than non iron-dosed sludge, and the totalbiogas production were6.60%,10.11%,10.11%,13.68%,18.74%higher than non iron-dosedsludge. When the concentration of PAC were90mg/L、150mg/L, the biogas production per gram ofVS were2.08%and23.78%lower than non PAC-dosed sludge, and the total biogas production were12.80%and28.07%lower than non PAC-dosed sludge.The dosing of FeCl3had positively impact on the CH4content of biogas and the calorific value,while the dosing of PAC negatively impacted them. When the concentration of FeCl3was150mg/L,the CH4content of biogas was10.7%higher than non iron-dosed sludge, while6.0%lower in CO2and60.6%lower in H2than non iron-dosed sludge; When the concentration of PAC was150mg/L, the CH4content of biogas was6.25%higher than non PAC-dosed sludge, with a composition17.21%richer in CO2, and4.65%richer in H2than non PAC-dosed sludge.（2） The results of the experiments showed that, the dosing of FeCl3had strong inhibitory on theH2S content of the biogas. The PAC dosing inhibited the H2S content of the biogas too, howeverFeCl3had better effect. When the concentration of FeCl3were90mg/L,150mg/L, the H2S content ofbiogas were210mg/m3and0mg/m3,792mg/m3and1002mg/m3lower than non iron-dosed sludge.When the concentration of PAC were90mg/L,150mg/L, the H2S content of biogas were494mg/m3,467mg/m3,508mg/m3and585mg/m3lower than non PAC-dosed sludge.（3） Both FeCl3and PAC could decrease the pH value of the anaerobic digestion. The resultsshowed that the pH value were0.01,0.04,0.02,0.05,0.04,0.06higher than non iron-dosed sludgewhen the concentration of FeCl3were36,54,72,90,120,150mg/L. The pH value, when the PACconcentration were90mg/L,150mg/L, were0.01,0.38lower than non PAC-dosed sludge.（4） TS, VS and VS/TS increased when the concentration of the FeCl3increased, and decreasedwhen the concentration of PAC increased. When the concentration of FeCl3was150mg/L, TS, VSand VS/TS were2.35%,1.29%,54.72%, and3.41%,7.86%,4.61%lower than non iron-dosedsludge. When the concentration of PAC was150mg/L, TS, VS and VS/TS were2.54%,1.48%,58.27%, and4.94%,5.71%,0.73%higher than non PAC-dosed sludge.Compared to the PAC, FeCl3was more favorable for the anaerobic digestion of sludge. Thedosing of FeCl3will improve the biogas production and the CH4content of the biogas, and inhibitthe generation of H2S. So it will be better to use FeCl3in the chemically enhanced primary treatmentof wastewater plant. |
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