Research On Drilling Wastewater Treatment Technology Coupled Fenton Oxidation And SBR

The drilling wastewater is a special industrial wastewater produced in the process of exploitation of oil and gas.The improper drilling wastewater treatment or its leak will cause serious pollution and do harm to the natural environment.Drilling wastewater display some characteristics,including its complex compositions,containing high concentration of pollutants and a large amount of heavy metals,which lead to its difficult treatment.There still are many problems such as the treatment effectiveness and energy consumption during the treatment.Therefore,development of an economical and feasible drilling wastewater process technology is still of great significance.This work concentrated on combined treatment technology of oil and gas field drilling wastewater based on Fenton oxidation and sequencing batch reactor activated sludge.The main work and experimental results are as followed:(1)It is firstly found that four commercially available coagulants(PFS,PAC,PAS,PAFC)cannot effectively remove COD concentration of drilling wastewater;but PFS can effectively eliminate odor of drilling wastewater.(2)A significant improvement of biodegradability and effective decrease of pollution index,including COD,ammonia nitrogen,total phosphorus and chroma of drilling wastewater via conventional Fenton oxidation were obtained.And quality ratio of H2O2 and COD of 1:1.63 and the mole ratio of H2O2 and Fe2+ of 1.67:1 were acquired.Effects of p H,temperature and reaction time on wastewater COD removal rate were also investigated.The level of primary and secondary sort of pH > time > temperature was obtained and optimized condition were pH of 3,reaction temperature of 30?,reaction time of 50 min.And COD removal rate of 77.83% was acquired under optimized condition.(3)COD concentration of effluent treated with Fenton oxidation was about 200 mg/L after a biological treatment.And the water became transparent and pale yellow.Additionally,brown activated sludge was obtained after a mature domestication and floc was compact with SVI of about 30.In addition to bacteria forming activated sludge granules in biological phase,there also were a lot of vorticella,small swimming ciliates,rotifers and protozoa and metazoan.(4)The aeration time of biological treatment was investigated based on the changes of COD concentration,the dissolved oxygen concentration,the absorbance at wavelength ranging from 200 to 400 nm and the operation of the SBR reactor.Accordingly,the optimal aeration time of 8 hours was obtained.However,water quality deteriorated after incubation in SBR for 2 weeks under optimized aeration time,which can be ascribed to the accumulation of toxic and harmful substances or the inaccurate control of the sludge age.(5)The technology coupled Fenton oxidation with SBR for oil field drilling wastewater treatment was developed.COD removal rate of 98.5% was obtained and ammonia nitrogen,total phosphorus and chroma of drilling wastewater met comprehensive waste water discharging standard ?(GB8978--1996).However,heavy metals(arsenic and lead)didn't meet the emission standards and needed to be further processed.