Microbial cultures can be used to reduce or eliminate scale formation in water flood injection systems. Several water floods have been treated for over a year with microbial culture products and the effects of the treatment on operating performance has been studied. The injection systems initially showed significant scale problems from calcium sulfate and calcium carbonate. Tracking water flood performance parameters such as injection pressures and volumes over the treatment period showed that, as compared with prior treatment historical data, a variety of positive results of treatment were evident. For example, the flood injection volumes were stabilized or increased, injection pressures were stabilized and oil and gas production was increased. Laboratory studies of injection water showed that filtration times could be significantly reduced by microbial treatment, indicating that near well-bore occlusion could be reduced by such treatments. The microbial treatments were considered more effective than prior alternative treatment technologies. This new technology offers a cost-effective superior alternative to conventional technologies.