Use of Additives in Bioremediation of Contaminated Groundwater and Soil

Abstract

This chapter reviews the application of additives used in bioremediation of chlorinat-ed solvents and fuels for groundwater and soil remediation. Soluble carbon sub-strates are applicable to most site conditions except aquifers with very high or very low groundwater flow. Slow-release and solid substrates are intended to be long-lasting in supplying carbon for microbial growth thereby minimizing operation and maintenance requirements. Microbes as special additives can be used to enhance bioremedia-tion (bioaugmentation) where such microbes are lacking. Oxygen gas can be added to increase aerobic biodegradation, and nutrients addition may be needed to stimulate and maintain sufficient microbial population. pH modifiers to control acidity for optimal microbial growth and degradation can also be added. Delivery of additives to the subsurface can be accomplished through permanent injection wells, direct-push methods, or permeable reactive barriers (biowall). Potential issues with additive use include biofouling, stalling, short circuiting, displacement, reduced hydraulic conductivity, and secondary water quality deterioration. Methods and techniques to deal with these issues are provided and future research needs are identified.