Performance and microbial community structure of Midwestern groundwater pretreatment reactors

Biological ammonia oxidation has received considerable industry research recently as water utilities seek to minimize chlorine demand and potential disinfection byproduct formation. Many plants are forced to chlorinate before primary filtration in order to meet disinfection requirements, so a pretreatment configuration is the one of the few feasible locations for biological activity. Parallel fixed-bed column reactors were operated in order to investigate the applicability of biological pretreatment for Midwestern groundwater containing dissolved methane, ammonia, and iron. One column was loaded with high-porosity gravel, while the second contained sintered glass pellets. Both media materials were marketed as “biological support” for aquiculture applications, and both columns were operated at a 10 minute empty bed contact time (EBCT) with continuous aeration to maintain aerobic conditions. Complete oxidation of influent ammonia was achieved within 50 days of startup without any nutrient amendment or microbial inoculation. Terminal restriction fragment length polymorphism revealed temporal and depth-related changes in microbial community structure throughout the ripening period in parallel with performance data. This study demonstrates that pretreatment systems could be a viable location for biological ammonia oxidation and a potential treatment choice for infrastructure-confined Midwestern utilities