Screening and demulsification capability of demulsifying bacterial strain TR-1 for crude oil dehydration

A demulsifying bacterial strain,TR-1,for crude oil dehydration is obtained from oil polluted soils in Karamay by a screening procedure described in some detail.The experimental W/O emulsion is prepared by mixing equal volume of oil and water phases separated at standing of a crude oil and has spontaneous dehydration rate <5% at 35℃ in 50 days.The dosage of TR-1 as whole bacterial culture(WBC) is 100 mL/L emulsion.The cultivation of the strain is performed at 35℃ and an optimal pH ranged 7—9 in 5—6 days.The WBC obtained contains 1.1×10~9 cells per mL and ～8.68 g of dried bacterial flora(DBF) per L and gives a dehydration rate(DR) >90% at 35℃ in 150 min.The DBF aqueous suspension(AS) of concentration 2.0 g/L gives a DR of 80.0% at the same dosage as WBC and a polyether demulsifier presently used—a DR of ～55% at dosage 100 mg/L.The main demulsifying mechanism by bacteria TR-1 is microbial cell's action and the biosurfactants produced by these bacteria play a much less important role.Bacteria TR-1 keeps their demulsifying capability fairly stable: the DR value is of 88.3%,91.7%,and 80.0% for WBC of the 1st,the 5th,and the 25th generation,respectively.For 2 light crude oils containing 50.0% and 66.7% water and taken from the 1st and the 2nd Karamay oil production factories with DBF-AS of 2.0 g/L added at dosage 100 mL/L,the DR at 50℃ in 150 min is of 66.7% and 88.2%,being much higher than that with polyether demulsifiers added however TR-1 is shown to be uneffective for the mixed heavy crude oil from districts Ⅱ and Ⅲ.For the light crude oil containing 50.0% water,introducing 5,20,and 40 mg/L polymer PAM changes its spontaneous DR at 50℃ in 150 min from 16.5% to 2.0%,4.0%,and 43.9%,respectively,and,when DBF-AS introduced additionally at dosage 100 mL/L,a DR of 96.5%,80.5%,and 76.5% is observed,respectively.