| Dairy cattle wastewater has obvious characteristics,which are high concentration of COD, ammonia nitrogen and suspended solids.It is a typical organic wastewater. If it is discharged directly, it will be harmful to the environment and human health. In this subject, we mainly focus on the research of the dairy cattle wastewater According to the technical route of the project feasibility study report, namely coagulation-electrochemical-anaerobic-aerobic- electrochemical combined process, this paper will carry out a series of experiments to provide design parameters, and measure up to "Agricultural irrigation discharge standard". The paper provides some valuable results for engineering construction, also provides a new idea for the wastewater with high concentration of organic matter, ammonia nitrogen and suspended solids.The plant wastewater was from washing the manure, which had treated by simple solid-liquid separation, and it contained domestic wastewater. The wastewater characteristics were high concentration of COD, ammonia nitrogen and suspended solids.The paper studied the efficiency of coagulation and electrocatalytic oxidation method used for pretreatment. Poly aluminium chloride was selected for pretreatment, when the optimum addition was 0.25 g/L. Results showed COD, SS and total nitrogen removal was 20%, 56%, and 20%, separately. In order to intensify removal rate of the ammonia nitrogen, the electrocatalytic oxidation technical parameters were optimized. Results indicated with the anode material Ti/Sn O2, current density of 25 m A/cm2, and degradation time 2 h, the removal of COD and TN was 60% and 36%, the COD and ammonia nitrogen of effluent was 6875 mg/L and 535 mg/L respectively, which met the requirement of ammonia nitrogen below 550 mg/L.The combined process of anaerobic and aerobic(EGSB-SBR) was used as biological treatment technology. The total EGSB volume was 7.5 L, and the effective volume was 3.5 L. It started with low load and the temperature of 35 degrees, reflux ratio of 20, HRT of 24 h. SBR ran according to 8-hour cycle and worked for three cycles every day. During the stable operation of combined system, the COD removal rate of EGSB reactor was 89%, the removal rate of SBR was 76%, and the COD of SBR effluent was 187±76 mg/L. When the combined system was stable, the sludge biota of EGSB and SBR reactor was observed. The well-adapted microorganisms have been formed under different conditions.The performance of EGSB with electrochemical pretreatment was also studied, and the difference of influent lied in whether it had been treated by electrochemical oxidation. The results showed COD removal was 67%, the methane proportion was 65% in biogas with ammonia nitrogen 745 mg/L and total nitrogen 1200 mg/L(influent), and increased to 89%, the methane proportion was 65% in biogas with ammonia nitrogen 535 mg/L and total nitrogen 770 mg/L, indicating the performance of anaerobic reactor was enhanced by decreasing ammonia nitrogen concentration. The datas verified the high concentration of ammonia nitrogen had inhibited effect to the anaerobic microbes, and explained the necessity of pretreatment.To ensure that the effluent of SBR could meet the requirement even if impact load existed, the electrocatalytic oxidation unit was set up after the SBR reactor. By comparing the effect and energy consumption of the two-dimensional and three-dimensional electrode system for SBR effluent treatment, it is concluded that the three-dimensional system was better. With the maximum COD concentration, particle electrodes of ceramic ring, current density of 10 m A/cm2, the effluent could act the mustard after degradation for 10 min.With the combination of technology unit, we got the whole process for dairy cattle wastewater. By analyzing the wastewater quality of stable stage, we could find When the COD of wastewater was 19750±1750 mg/L, the COD and TOC of SBR effluent was 187±76 mg/L and 106 mg/L. After electrocatalytic oxidation, B/C was increased from 0.41 to 0.65, but decreased to 0.19 after biodegradation. By analyzing different stages of the effluent with the help of GC-MS, we could find organic species were many, and the hardly degradation compounds were left after anaerobic-aerobic process. |
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