Experimental Study On The Treatment And Influence Factors Of The Reverse Osmosis Brine From A Refinery By Activated Carbon Catalytic Ozonation

The treatment process of refining effluent generally includes oil separation, gas floatation, biological oxidation and filtration. Enterprises produce water which can meet the needs of production through recycle equipment due to the shortage of water resources. Ultrafiltration and reverse osmosis is widely used in advanced treatment of refinery wastewater owing to its efficient separation. The produced water of UF+RO which influent has been pretreated can be reused as the production water. The reverse osmosis brine with low bioavailability and complicated compositions will pose potential threat to human health and environment if it is discharged directly. Therefore, advanced treatment is necessary to reduce the pollutants and the impact on environment.This paper adopts the technology of activated carbon-ozone to treat the reverse osmosis brine by using the static and dynamic experiments respectively. The experiments studied effects of factors such as types of activated carbon, pH, reaction time and ozone dosage on the removal efficiency of COD.1 Choosing pH, ozone dosage, reaction time, pretreatment method, type of medium design the orthogonal test of thirteen factors at three different levels according to the conditions affecting the experiment. Obtain the important order of factors combined results of variance analysis and range analysis: pretreatment method>reaction time>ozone dosage>type of medium>pH. And in the type of medium, attapulgite clay has low efficiency and activated carbon is the best. Taking activated carbon or modified activated carbon as the next pretreatment or combined process object based on that activated carbon has no interaction with other factors.2 Static experiments studied the treatment of the reverse osmosis brine by ozone oxidation and activated carbon catalytic ozonation respectively. The effects of pH and reaction time on the ozone oxidation experiment were investigated. Different methods of modifying the original activated carbon were carried out to compare with the treatment of ozone oxidation and catalytic ozonation efficiency of modified activated carbon and effect of catalyst dosage were study in order to provide technical guidance and reference for practical engineering application. The results showed that:⑴the removal rate of COD could up to 45% when pH=8.14 and the reaction time was 40min;⑵the catalytic effect of hydrogen peroxide modified activated carbon was best between the three methods of modifying the original activated carbon. Because the products of ozone oxidation are mostly hydrophilic which is difficult to be completely removed, and hydrogen peroxide modified can increase the hydrophilic groups on the surface of the activated carbon which contributing to the adsorption to these hydrophilic substances. Activated carbon which was hydrogen peroxide modified catalytic ozonation accelerated the reaction process and the removal rate of COD. And the catalytic effect was the best when the dosage of hydrogen peroxide modified activated carbon was 2g.⑶The biodegradability of reverse osmosis brine is poor. Ozone can degrade most of refractory organics as small molecules when pH is alkaline, so the biodegradability of reverse osmosis brine was enhanced from 0.01 to 0.62; and the effluent biodegradability of activated carbon catalytic ozonation was 0.45.3 Activated carbon adsorption、ozone oxidation and activated carbon catalytic ozonation were carried out to study the treatment efficiency in dynamic experiments. The effects of different pH and ozone flow on the removals of COD were analyzed. The differences of catalytic ozonation performance between modified activated carbon and unmodified activated carbon、unsaturated activated carbon and adsorption saturated activated carbon were studied. Meanwhile, the stability of the active carbon and the recovery of the catalytic performance after regeneration were investigated and the mechanism of activated carbon catalytic ozonation was discussed by analyzing the infared spectrum of before and after treatment of the reverse osmosis brine. The results showed that:⑴the effect of catalytic ozonation is best when the ozone flow rate was 0.06 L·min-1 and pH=8. The oxidation of pollutants was not sufficient under the low ozone flow. However, the residence time of ozone became shorter and the contact between active carbon surface and ozone was not sufficient when the ozone flow rate was too high. The direct oxidation of ozone came into prominence under acidic condition, so the removal efficiency of COD was poor. There may be a mutual collision quenching under high hydroxyl radical concentration when pH reached very high. In addition, some radical scavenger would appear in a certain degree of alkalinity. ⑵The performance differences between modified catalytic ozonation and unmodified activated carbon 、unsaturated activated carbon and adsorption saturated activated carbon were not obvious which suggested that the original activated carbon catalytic oxidation had been adequate under the experimental conditions and adsorption saturation did not affect the activated carbon catalytic activity. ⑶Activated carbon catalytic ozonation system generated hydroxyl radical with stronger oxidation ability which accelerated the reaction process obviously. Experiment reduced COD to about 75mg/L when at the first cycle, removing 1 g COD consumed 2.5~4.1 g ozone; and the COD was reduced to 40mg/L after six cycles which the removal rate was up to 80%. The good stability of the catalyst which the average COD of first 11 times effluent was 52.5mg/L and the removal rate was 74.2% after regeneration suggested that this process has high efficiency applicability in the treatment of reverse osmosis brine of refinery. ⑷The biodegradability of reverse osmosis brine increased significantly from 0.01 to 0.36 after activated carbon catalytic ozonation.