AbstractInjection water is commonly treated with chemical biocides, corrosion and scale inhibitors, and oxygen scavengers, to name a few. Without treatment, iron sulfide, hydrogen sulfide, iron oxide, and other impurities will form, precipitate and damage unprotected surface equipment and lines and plug injection wells. In many cases, acid, xylene and even coiled tubing are required to restore injectivity.Although traditional chemical treatments can be effective in many cases they are not "worker friendly". This paper will present the results of an ongoing, worker and environmentally safe, lower- cost alternative-Microbial Water Treatment (MWT). A discussion of treatment mechanics, strategies and evaluation are presented along with past and current results of the successful 310,000 barrel per day MWT program at the Wilmington Oil Field.P. 435