Study On High Voltage Pulse-Ozone-Fenton Combined Oxidation Process For Drilling Fluid Wastewater Treatment

Drilling fluid waste water is an industrial waste water produced during the exploitation of oil and gas fields.Drilling fluid wastewater has the characteristics of high COD_cr,high chroma,high concentration of suspended solids,high salinity,high pH,and complex composition.If it is discharged without treatment,it will cause serious pollution to surrounding soil and water bodies.In this paper,Chuanqing drilled the drilling fluid waste water from a polysulfonated mud system in a well.The chemical coagulation method was used to pretreat it first.The optimal coagulation conditions were determined by single factor and orthogonal experiments;then the high pressure was used.The pulsed discharge system was combined with ozone and Fenton two advanced oxidation methods to perform degradation experiments on the drilling fluid wastewater after pretreatment.The three processes of high-voltage pulse discharge,ozone oxidation,and Fenton oxidation were studied separately.The optimum reaction conditions for wastewater,and finally the combined oxidation process for the treatment of drilling fluid wastewater from a certain oil and gas field in Chongqing Fuling,the conclusions are as follows:?1?Chemical coagulation conditions:PAC dosage 5g/L,PAM dosage 10mg/L,pH value7,stirring rate 300r/min;effluent pH value of 7.64,water golden yellow,COD_cr by14256mg/L dropped to 2367mg/L and BOD₅ dropped from 1205mg/L to 587mg/L.?2?High voltage pulse conditions:discharge voltage 35kV,discharge frequency 80Hz,pulse width 60ns,air flow 2L/min,continuous discharge 120min;effluent COD_cr is446.1mg/L,BOD₅ is 212.6mg/L.?3?Ozone oxidation conditions:The mass flow rate of ozone is 1.8g/h,the initial pH of the wastewater is 9 and the reaction time is 30min.The effluent COD_cr is 741.2mg/L and the BOD₅ is 362.5mg/L.?4?Fenton oxidation conditions:n?H₂O₂?/n(Fe²⁺)was 10:1,initial pH value of wastewater was 3,and reaction time was 90min;effluent COD_cr was 825.9mg/L and BOD₅was 387.3mg/L.?5?Combined oxidation process conditions:The first stage of the process is high voltage pulse-ozone,the ozone dosage is 1.2g/h,the pH of the wastewater is 9 and the reaction is 30min;the second stage is the high voltage pulse-Fenton,H₂O₂ dosage At 6mL/L,the Fe²⁺dosage was 5mmol/L.The pH of the wastewater was 3 and the reaction time was60min.The high voltage pulse reaction conditions of the two-stage process are discharge voltage 35kV,discharge frequency 80Hz,pulse width 60ns.The effluent COD_cr was71.8mg/L,and the BOD₅ was 25.6mg/L,which was lower than relevant the secondary standard limit of the Integrated Wastewater Discharge Standard?GB8978-1996?.By changing the reaction sequence of the two combined oxidation processes and comparing the treatment time and effect,the high voltage pulse-ozone/high voltage pulse-Fenton combined oxidation process is superior to the high voltage pulse-Fenton/high voltage pulse-ozone process.?6?The optimum conditions for combined oxidation were used to treat drilling fluid wastewater from a certain oil and gas field in Fuling,Chongqing.The pH value of the effluent quality was 7.53,COD_cr was 62.3mg/L,BOD₅ was 17.8mg/L,and SS was21.5mg/L.Reached the relevant limits of the first-grade standard of Integrated Wastewater Discharge Standard?GB8978-1996?.