A Study On The Impact Of Adding Trace Elements To Anaerobic Digestion Of Coking Wastew Ater

Coking wastewater is a kind of toxic industrial wastewater which is difficult to degradationby biological methods. The lack of trace elements leads to the low COD removal rate and lowmicrobial activity and it seriously affects the effect of anaerobic reactor process. Trace elementsplay an important role in increasing the anaerobic microbial activity and improving theefficiency of anaerobic biological treatment. The effect of the anaerobic treatment improvedsignificantly after the addition of trace elements.4kinds of trace metals and3kinds of vitaminswere added to anaerobic reactor of actual coking wastewater to improve the treatment effect.The metals are Fe, Co, Ni, Zn, and the vitamins are vitamin B1, B2, B6. The effects of the7traceelements on coking wastewater anaerobic treatment were explored through the assay of CODremoval rate, gas production and residual elements of effluent.According to the experiment, in coking wastewater anaerobic treatment, separate additionsof Fe，Co，Ni，Zn（in the form of A bivalent chloride） can enhance digestion reaction. Theoptimal concentrations in reaction are1.0,2.0,0.7,2.0mg/（L·d）, the COD removal rate reach to250%,549%,285%,261%of the control respectively. The optimal concentrations in reactionare2.0，0.4，0.5，6.0mg/（L· d） when joint dosing4metal elements of Fe, Co, Ni, Zn, the CODremoval rate reach to381%，408%，320%，231%of the control respectively. The UV spectraof inffluent and effluent were determinated and it indicated that the derivatives of benzenehad been degradated effectively.The test also determined residual quantity of Fe²⁺and Ni²⁺in upper effluent. Theminimum residual amount of Fe²⁺is9.18%in upper effluent, most are reserved in the sludge,and the loss proportion is not large along with upper effluent. The minimum residual amount ofNi²⁺is14.17%in upper effluent, it proves that microbes can fix and assimilate Ni2+in solutioneffectively, most didn’t lost with upper effluent.The optimal concentration of vitamin B1，B2，B6are2.0,1.2,1.2mg/（L d.） respectively, theCOD removal rate reach to252%，112.5%，256%of the control, vitamin B6has the best effectand biggest feasibility in economy.The results show that the addition seven kinds of trace elements have a significant impact in anaerobic digestion process：The removal of COD is promoted, a part of poisonous substanceis degraded, and Fe²⁺and Ni²⁺in reaction are not easy lost with effluent, the difficulty ofsubsequent biochemical reaction is reduced.