Operational parameters required for the start-up process of a biofilter to remove Fe, Mn, and NH3-N from low-temperature groundwater

Abstract

Start-up experiments were carried out using a constructed a pilot-scale biofilter in a water supply plant to purify iron (Fe), manganese (Mn), and ammonia (NH3-N) from low-temperature groundwater (3–4°C throughout the year). The results of the biofilter operation indicated that the simultaneous removal of these contaminants could be obtained with a one-stage biofilter, while the operational parameters such as aeration and backwashing strength (BWS) should be optimized during the start-up operation period. Removal of Fe was most likely dominated by chemical oxygen oxidation since the biofilter exhibited high removal efficiency at the initial running period and the start-up time was not required. Higher levels of aeration (that corresponds to higher dissolved oxygen concentration) helped to transform the water redox environment and increase Mn removal. Nitrification effects were irrelevant with the extra aeration. A weaker BWS was helpful in avoiding biomass loss during the initial operation of the biofilter; however, the BWS should be improved to eliminate excess amounts of metal oxide accumulation after a long operation time, since it could enhance the overall removal. Using high-throughput sequencing technology, the functional bacteria genera were identified. It was demonstrated that the corresponding functional oxidizing bacteria could be acclimated sufficiently in low-temperature water.