Degradation Efficiency Study Of Dyeing Wastewater Treatment By Ozone/Micro Electrolysis Process

As the treatment difficulty of printing and dyeing wastewater improved and the discharge standard is even more strictly, traditional treatment processes based on biological methods are difficult to satisfy the new standard. Effective physical and chemical treatment processes are emergency needed to satisfy the discharge standard. In this regard, ozone/micro electrolysis process was proposed by our group, and it was proved to be effective for deying wastewater treatment. On the basis of preliminary studies the efficiency and application of technology was researched further in this issue. It aims to provide a theoretical basis for treatment of dyeing wastewater and application of ozone/micro electrolysis process. The treatment efficiency and optimum operating parameters was investigated through small pilot study about analog dyeing wastewater with different structures and real dyeing wastewater. On the basis of small scale laboratory studies the pilot application was conducted to identify and solve problems encountered during the pilot intended to provide theoretical basis for technology applications.Eight kinds of dyes were selected according to the application population and soluability to carriy out present study. All these dyes had excellent color, COD, and aniline removal performance when treated by ozone/micro electrolysis process. Furthermore, B/C ratios of simulated dyeing wastewaters were significantly improved after treated by ozone/micro electrolysis process. Color and COD removal efficiencies were as high as 92% and 40~75% respectively when ozone dosage rate was 90mg/L. Moreover, Aniline concentrations in the effluent were lower than 0.03 mg/L. The suitable operational conditions for ozone/micro electrolysis process were as follow: p H=6~10, ozone dosage was 32.5 mg/L with a flow rate of ozone was 1.3 mg/(L·min) and the retention time was 25 min.Real wastewater can be divided into two different types according to B/C ratio. Ozone/micro electrolysis process showed high treatment performances for both types of real wastewatersbut longer reaction time and higher cost were needed to obtain a desired treatment performance. The study indicates that a pre-treatment can effectively shorten the HRT of the ozone/micro electrolysis process. When the real wastewater has lower B/C, propriate process is "ferrous coagulation precipitation-ozone/micro electrolysis-biochemical treatment". While when the real wastewater has higher B/C, biochemical process should be employed as pre-treatment and ozone or ozone/micro electrolysis process for aniline removal.A novel process expressed as "coagulation precipitation- ozone/micro electrolysis- biological aeration filter(BAF)" was established in this research to treat real wastewater and obtained good performance. The pilot experimental results showed the effluent color, COD, and aniline were 10, 60 mg/L and 0.03 mg/L respectively when ozone dosage was 46 mg/L, HRT for BAF was 1 h. And the quality of the treated effluent meets the discharge standard(GB4287-2012). The residual ozone concentration of ozone/micro electrolysis unit was lower than 0.2 mg/L and decomposed rapidly, which will not affect the activities of the biomass in subsequent BAF unit. According to the iron dissolution rate test in pilot process, the usage time of the filer was calculated as 7 years. The filler’s special spherical structure s and regular backwashing can alleviate the passivation of the filler. The cost estimation of present process "coagulation precipitation- ozone/microelectrolysis- BAF" based on pilot experimental results was 1.781yuan/ ton.