The Experimental Study Of Wheat Straw Pulp And Paper Wastewater Secondary Effluent By Ozone Oxidation

This paper mainly investigated the impacts of ozone dosage and ozone contact time on the removal effect of the CODcr, UV254, chromaticity, turbidity and nitrogen content. And this paper also discussed the mechanism of nitrogen oxides generated by air source ozone generator, and briefly introduced the application of ozone oxidation de-colorization pulp and paper wastewater.The pulping and papermaking wastewater secondary biochemical effluent and pretreated papermaking mixed wastewater respectively were treated by ozone oxidation. The treatment effect of ozone oxidation secondary biochemical effluent was better than the papermaking wastewater without biochemical processing. Under appropriate ozone dosage and contact time, ozone oxidation treatment can effectively reduce the CODcr, UV254and chromaticity of pulping and papermaking wastewater secondary biochemical effluent. And the secondary biochemical effluent CODcr removal rate can reach51%, UV254removal rate can reach68%and the removal rate of chromaticity can reach87%.Pulping and papermaking wastewater secondary biochemical effluent was treated by ozone oxidation. When ozone dosage were107.34-137.25mg/L, CODcr, UV254and chromaticity were all relatively good removal effect, and the removal rates of CODcr, UV254and chromaticity respectively were33.39-36.49%,47.91-63.59%and82-86%. When the contact time were1.28-1.74h, CODcr, UV254and chromaticity were all relatively good removal effect, and CODcr, UV254and chromaticity removal rate respectively were32.3-39.29%,39.88-63.93%and80～86.67%.Ozone oxidation had some certain removal effect for wastewater turbidity, and the average removal rate were68%.There were no big impact of ozone dosage and contact time on the turbidity removal rate of wastewater. Because of ozone micro flocculation effect, there was the negative turbidity removal rate phenomenon in the ozone oxidation process.The ozone in this experiment was produced by the air discharge, but the air discharge at the same time would follow the production of nitrogen oxide. Nitrogen oxide came into the ozone oxidizing tower with the ozonized air and dissolved into wastewater which caused the increasing of nitrogen content. The effluent total nitrogen content were larger than that of the influent, the effluent’s total nitrogen content were as1.01～1.38times that of influent. The nitrate nitrogen content continued to accumulate. The concentration of ammonia nitrogen rose slightly but marginally, and the average ammonia nitrogen change rate were1.06times.This paper investigated the impacts of ozone dosage and contact time on changes of the nitrogen content in the wastewater. With the increase of the ozone dosage, the concentration of total nitrogen and ammonia nitrogen in the effluent were larger than in the influent, but there were no obvious linearity correlation between ozone dosage and their change rate. The total nitrogen average change rate were1.08times, and the ammonia nitrogen average change rate were1.07times, and the nitrate nitrogen content continued to accumulate. With the increase of the contact time, the contact time of ozonized air and wastewater increased, and more and more nitrogen oxide dissolved into wastewater. Total nitrogen change rate increased from1.06times to1.38times. Nitrate nitrogen increment increased from1.329mg/L to2.165mg/L. And ammonium change rate was more gentle, and the average change rate were1.05times.The maximum actual nitrogen content added value2.788mg/L in wastewater which is measured in experiment is less than the theoretical calculation nitrogen content added value7.000mg/L which is caused by nitrogen oxide in ozonized air dissolving into biochemical effluent, and its conversion rate is only39.68%.