Study Of Fischer-tropsch Synthesis Wasterwater Treatment Using Anaerobic Technology Enhanced By Dosing Of ZVI

As the rapidly progress of chemical processing of coal, the considerable economic benefit and product were get, but at the same time, the environment problem caused by chemical processing of coal is more outstanding and get more attention especially the water problem. Fischer-Tropsch synthesis as a important step in coal-oil technique produce a large number of wastewater that has high CODCr concentration and nethermore p H. owning to the especial character, Fischer-Tropsch synthesis wastewater is difficult to treatment and there is no more study about it, so this study’s main objective is to explore how to treat Fischer-Tropsch synthesis wastewater according to anaerobic biological treatment. At present, anaerobic biological treatment enhanced by dosing of ZVI get used extensively but it is unwonted to Fischer-Tropsch synthesis wastewater treatment, so in the study two stage experiments were designed to explor the feasibility and how the ZVI works in anaerobic biological treatment. This study will be helpful to Fischer-Tropsch synthesis wastewater treatment in real project.In the first stage experiment, simulate Fischer-Tropsch synthesis wastewater that was compounded according to the real data was used as substrate to investigate the effect of different experiment conditions such as original value of p H in the reactor and the size and concentration of ZVI and optimize the experiment condition. The result indicated that there was best quantitative value in value of p H and concentration of ZVI and smaller the size of ZVI, higher the removal rate of CODCr. After the single factor experiment, study applied response surface methodology based on Box-Behnken experimental design to analyze the data, the result indicated that the optimal conditions were determined as follows: original value of p H 6; grain diameter of ZVI 475 mesh; dosage of ZVI 2.45g/L.Operating two experiments in different conditions, the one was in optimal conditions, the other one applied Fe2+ to replace ZVI, under the optimal conditions, the removal rate of COD was higher and get 74.5%. The influences of ZVI on the system environment parameters（p H/ORP） are prominent: p H get low caused by the neutralization reaction between ZVI with organic acid and the reducibility of ZVI made the ORP of anaerobic system also get low, it was helpful to anaerobic digestion.In the second stage, study applied UASB reactor to treat simulated wastewater and analyzed the effect of ZVI on removal efficiency of organics, methanogenesis efficiency, composition of EPS and the effect of EPS to the formation of anaerobic granular sludge. The result indicated that ZVI in UASB reactor made a positive effect, the average removal rate of experimental group reach 80.6% and the output of CH4 reach 1.65L·L-1·d-1 that higher than that of control groug. In experimental group, anaerobic granular sludge was observed earlier than the control group; the experiment p Henomenon indicated that stability and efficiency of the reactor were promoted with using of ZVI. The rise of contents of the total iron with different morp Hology iron indicated detection that ZVI offered enough Fe to anaerobic methanogensis.In addition, the content of F420 and F430 in the experimental group get 2.86umol/g VSS and 0.92 umol Ni/g VSS, but in the control group that was just 1.84umol/g VSS and 0.76 umol Ni/g VSS. Combining the analysis of FTIR spectroscopic and EPS, study found ZVI can obviously increase the metabolism activity of anaerobic methanogensis. The results of high-throughput sequencing showed that the number of OTU in experimental group was 546 but that was 530 in control group, so the diversity of microorganism coenobium was higher in experimental group. Meanwhile ZVI can cause the change of microbial dominant species and the methanogens abundance, Methanoregula still was the absolute dominant species, the abundance of Methanobacterium 、 Methanolinea and Methanosarcina increased but decrease the content Methanospirillum 、Methanomethylovorans and Methanosaeta.In conclusion, using anaerobic technology enhanced by Dosing of ZVI treat Fischer-Tropsch synthesis wastewater get outstanding effect,during the process, the main way of ZVI promote methanogens is ZVI improved the condition of anaerobic system to promote the stability of reactor and changed the way of methanogenesis, meanwhile ZVI promoted the efficiency of anaerobic reaction by release Fe²⁺.