Effect of Biocides Blend on Microorganisms in Produced Water

The exploration and production of crude oil lead to the production of a significant quantity of associated gas and produce water. The produce water is either reinjected into the oil well or discharged into the environment. There is therefore a need for the water to be treated before any of the aforestated operations are carried out, as it contains a significant amount of microorganisms that pose a threat to production facilities as well as the environment. This research studies the use of a combination of two types of biocides, quaternary ammonium chloride (QUAT) and tetrakis-hydroxymethyl phosphonium sulfate (THPS), at various ratios in order to determine which is most effective. The pour-plate method for total viable bacterial enumeration was applied. It was discovered that, generally, the blends of biocide proved to be more effective in combating bacterial activities in produce water at lower concentrations and longer reaction times than the individual biocides. Thus, the 75% THPS + 25% QUAT as well as the 50% THPS + 50% QUAT were most effective at a concentration of 1000 ppm and a reaction time of 9 hrs in reducing the microbial population from 1.53 ×108 bacterial cells/ml to 3.3×102 bacterial cells/ml and 3.7×102 bacterial cells/ml, respectively.