Stduy On Wastewater Treatment And Process Intensification By Pulsed High-voltage Discharge

The direct discharge of ammonia-nitrogen wastewater always causes environmental pollution,which is very harmful to human health and ecological environment balance.Aniline and phenol industrial wastewaters and landfill leachate are highly concentrated ammonia-nitrogen wastewaters.At present,physicochemical and biochemical treatment technologies are mainly used for the treatment of highly concentrated ammonia-nitrogen wastewater,which is strongly dependent on the stability of sewage source and needs long period of treatment processing,resulting in the limitation of application.Advanced oxidation technology,which has been considered as a popular technology in recent years,is a highly effective treatment method of organic pollutants in wastewater by strong oxidizing active substance.Pulsed high-voltage discharge,as one of advanced oxidation processes for the treatment of wastewater,utilizes low temperature plasma,high-energy electron and UV-radiation generated in the discharge processes of gas and liquid system to degrade wastewater,which is condered as one of effctive treatment methods for the degradation of highly concentrated ammonia-nitrogen wastewater.In this paper,the concept of intensification of discharge by adding packed layers was proposed based on the study of the degradation conditions of simulated aniline and phenol wastewaters and landfill leachate by pulsed high-voltage discharge.Small electric fields are formed around the materials in the packed layer during discharge process.Besides,a strong electric field with synergistic effect is formed by the interaction effect between these small electric fields.More and more active particles are formed by the microdischarge of each small electric field.After 120 min treatment by filling 10-layer 40-mesh stainless steel net in pulsed high-voltage discharge process,the COD of simulated aniline wastewater,simulated phenol wastewater and landfill leachate decreased from 1383 ppm,1587 ppm and 588 ppm to 223 ppm,298 ppm and 52 ppm,and the COD removal efficiencies were up to 83.88%,81.23%and 91.21%,respectively.Structured packing was introduced into pulsed high-voltage discharge reactor to promote the application of packed layers.Single-plate discharge was transformed to multi-plate discharge by the improvement of pulsed high-voltage discharge reactor,leading to the increases of active site number,discharge efficiency and active substance amount.At the same time,the discharge power was improved by changing from single-channel dischage to three-channel discharge,leading to the increase of discharge efficiency,which is beneficial to increasing the degradation efficiency and shortening the degradation time.The COD of landfill leachate decreased from 598 ppm to 57 ppm at 30 min.The COD removal efficiency of landfill leachate was up to 90.52%.The study of degradation of real wastewaters including land leachate,aniline and phenol industrial wastewaters was conducted using pulsed high-voltage discharge in conjunction with flocculation and Fenton processes to verify the improvements repoted previously in this paper.The water quality could be effectively improved and the turbidity and COD of wastewater could be reduced by flocculation process.Then the wastewater could be further degraded by Fenton process.A single cycle of flocculation,Fenton and pulsed high-voltage discharge processes is insufficient for the degradation of real wastewater due to very high COD.Therefore,multiple cycles of degredation processes are needed for achieving complete purification.The COD of landfill leachate decreased from 41766 ppm to 91 ppm and the degradation efficiency reached up to 99.78%after double flocculation,triple Fenton processes and pulsed high-voltage discharge process.The COD of aniline and phenol industrial wastewaters decreased from 2859 and 2627 ppm to 47 and 42 ppm and both COD removal efficiencies reached up to 98.4%after one-time flocculation and two-times Fenton process and pulsed high-voltage discharge process.This work provides technical guidance for industrial treatment process of real wastewaters.