A Study On Pretreatment Of Shale Oil Wastewater

Shale oil wastewater is a typical organic wastewater with high ammonia nitrogen, high COD, high oil content and a variety of complex components which is hard to be degraded directly using biological treatment. The purpose of the study is to develop economic effective pretreatment process in order to improve the feasibility of subsequent biological treatment. Base on the quality characteristics of shale oil wastewater, in this paper, the pretreatment scheme of blow-off method and electro-coagulation method was adopted.The main research contents include:The shale oil sewage was collected from one of Fushun Shale Oil Companies for the research. The blow-off method was designed with single factor analysis and the removal rate of ammonia nitrogen was used as evaluation index. The optimal conditions for ammonia nitrogen removal rate of 86.38% were obtained:reaction time 90min, gas to liquid ratio 120:1, the initial pH 9.0 and the temperature 70℃. Meanwhile, by means of orthogonal method and experimental data, continuously increasing pH could only raise ammonia nitrogen removal rate in the early stage of the experiment, but has little influence on the final result under the conditions of 70℃ and pH over 9.0. Unifies the actual situations in the field of Shale Oil Company, high ammonia nitrogen removal using blow-off method could have achieved by taking full advantages of inherent qualities of high temperature and high pH value of actual wastewater.The influencing factors of periodical reversal electro-coagulation method including the plate material, the pH value, the voltage, the stirring speed, the plate spacing, the alternating period and the reaction time were examined. The experimental results showed a feasible oil removal but COD. Optimum technological parameters and stability analysis were investigated. The results indicated that oil removal rate was steadily maintained at about 70～80% by electro-coagulation. Furthermore, the power and plate materials consumption were calculated and established using the linear fitting. In comparison of oil removal efficiency using different plate material, it turned out in descending order:Fe/Fe>Fe/Al>Al/Al>Graphite/Graphite. The relationship between influence factors and the oil removal rate was obtained through the orthogonal test.By comparing the sequential order of pretreatment scheme of electro-coagulation and blow-off method, the data displayed that the pretreatment efficiency of a combination by setting air stripping prior to electro-coagulation was better than that of the other way around. Oil substances and ammonia nitrogen were downgraded to 43.54 mg/L and 111.83 mg/L respectively which may contribute to further biological treatment. Refer to the results in previous experiments, the total power consumption was preliminary estimated 28.91 kw-h/m3, and the iron plate material consumption was about 2.55 kg/m3. According to consult price, the total operation cost was 21.10 yuan/m3.