Bio-Chemical/Physico-Chemical Treatment Of Wastewater Containing Oil And Sludge In Daqing Oilfield

It is well known that plenty of sewage and wastewater contained oil would be produced during the process of oil and natural gas production. For most of the oil sewage, it would be injected back to the oil layer after treatment. However, a certain amount of the oil sewage has to be discharged out due to the increase of oil sewage, which exceeded the requirement for discharge. The sludge containing oil includes sludge fell to earth, sludge in settling-pot, bottom deposit of the sewage treatment structure, sludge from three-phase spectator and sludge spilled with oil in accident. It is obvious that the increasing amount of sludge oil and oil-sewage aggravated the environmental pollution, which is deteriorated along with the exploration and development of oil field. Based on the factual conditions of Daqing Oil-field, biochemical processes and physic-chemical processes were designed for sludge containing oil and oil sewage treatment in this research. In the lab-scale and full-scale tests, a process of hydrolysis acidification/biocontact oxidation was developed for oil sewage, a process of hydrolysis acidification/biocontact oxidation/flocculation for the continuous outfall polymer oil sewage, and a process of micro-eletrolysis-Fenton for the intermittent outfall polymer oil sewage with small flow, which made the oil sewage reach the national discharge standard, gradeâ…¡and the sludge containing oil be reutilized as resource.Bacteria with high efficiency of oil sewage removal were separated from the treatment process system of hydrolysis acidification/biocontact oxidation, and functional bacteria community consisting of strain 5-1, D-1, D-10 and D-8 was established. When the established functional bacteria community was adopted in the process of oil sewage treatment, the average COD and BOD removal rate reached 86.2% and 92.1% respectively.The functional bacteria community consisting of the separated polyacrylamide-degradation bacteria could remove polymer as high as 49.8%. To make COD meet the discharge standards, flocculation should be added into the settlement section when there were large amount of polymer sewage entered the process of hydrolysis acidification/biocontact oxidation. The cost in this process was about 0.90 RMB/m3, which proved that this process could be propitious to continuous and large volume polymer sewage treatment.