Study On The Treatment Of Vehicle-Washing Wastewater By Bipolar Three-Dimensional Electrode Reactor

The sustainable use of urban water resources had become the world’s most important resources and environmental problems.With the city motor vehicles increased, the cleaning process caused a lot of waste of water resources.The arbitrary discharge of vehicle-washing wastewater had caused serious water environment pollution,and the effective treatment and recycling use had attracted increasing attention.Based on the introduction of the characteristics and harmfulness of vehicle-washing wasterwater,a new technology—biopolar three-dimensional electrode electrolysis was introduced to treating vehicle-washing wastewater for many advantages.The paper respectively analyzed three-dimensional electrode technology and two-dimensional electrode technology.The mechanism and the influence factors of vehicle-washing wastewater treated by both technologies was studied distinctly and systematically.Meanwhile,the optimization levels were given.So it could provide some new thoughts and pathways for industrialization treatment of vehicle-washing wastewater wastewater.We could draw a conclusion by experimental research as follows:In the bipolar three-dimensional fixed-bed electrolytic cell with aluminum as electrode material,these factors such as cell voltage、reaction time、electrode distance、pH、current density and electrolyte concentration were selected as the facts that effect the COD removal efficiency and turbidity removal efficiency to do orthogonal experiment.The result showed that the order of the affection degree of COD removal efficiency was:reaction time＞cell voltage＞current density＞electrode distance＞electrolyte concentration＞pH;and the order of the affection degree of turbidity removal efficiency was:reaction time＞current density＞cell voltage＞pH＞electrode distance＞electrolyte concentration.The best reaction condition was:active carbon stuffing,cell voltage=30V,electrode distance=3cm,reaction time=30min,pH=6-9,electrolyte concentration=6 mA/cm~2,NaCl as the electrolytes and its density was about 1g/L.Under the condition,the COD and turbidity removal efficiency of vehicle-washing wastewater can reach 91%and 98%.The bipolar three-dimensional fixed-bed electrode reactor was carried out appropriate improvements into bipolar three-dimensional fludized-bed electrode reactor,and then it was applied to degradation of vehicle-washing wastewater.The results showed that:with the amount of activated carbon increased,COD removal efficiency had a significant improvement,and when it increased to 50g(concentration equivalent to 33.3g/L),the COD removal efficiency reached the maximum and then decline slightly.When the cell voltage increased,the activated carbon particle being polarization increased and its effective electrode area enlarged,thus the COD removal efficiency increased.But if the cell voltage was too high,side effects and energy consumption would increase.With the pH value changed,the COD removal efficiency would change corresponding,but did not change significantly.The closer pH approached to neutral,the higher the COD removal efficiency becomed.With the airflow increased,COD removal efficiency growed,especially in the initial reaction stage(5-10min).However,when the air flow was too large,organic compounds could not stay on the particle electrode’s surface and had to leave because there’s not enough time to react with active species generating on the electrode surface,so it’s not conductive for organic compounds to oxidative on the electrode surface,so the airflow was taken 3L/min.By a series of comparative experiments between three-dimensional electrode system and two-dimensional electrode system,we could draw a conclusion that the COD removal rate of three-dimensional electrode system was much higher than two-dimensional electrode system,and the degradation effect dealing with vehicle-washing wastewater of three-dimensional electrode system was better than two-dimensional electrode system;The energy consumption tests showed that:when the COD removal efficiency was below 30%,the energy consumption of three-dimensional electrode reactor was higher than that of two-dimensional electrode reactor.And when the COD removal efficiency was above 30%,the opposite results appeared.At this time,the three-dimensional electrode reactor had obvious superiority on saving energy consumption.In addition,the three-dimensional fludized-bed electrode reactor had smaller energy consumption and better degradation effect comparing to three-dimensional fixed-bed electrode reactor;The study also showed that the reaction of three-dimensional electrode system and two-dimensional electrode system dealing with vehicle-washing wastewater was both in accordance with first order reaction kinetics,.the reaction rate increased with inlet organic concentration growing,and changed with time as exponential relationship.