Sorption of humic substances and microbial activity in the course of artificial recharge of groundwater

Abstract: Sorption of humic subtances and metal-humate complexes on aquifer material taken from basins used for artificial recharge of groundwater was studied in batch scale experiments. Distribution of bacteria attached to the material from uppermost layer and from the horizons below the infiltration basin were measured in the field studies. Sorption of aquifer material was heterogeneous in respect to the different position and depth in the infiltration basin. Sorption depended on the numerous factors including composition of the filter sand and properties of humic matter. The heavy metals retarded during artificial groundwater recharge was in the form of metal-humate complexes, dominantly in anionic form or as particulate matter. Sorption of humic substances on the aquifer material was substantially enhanced due to the forming of complexes with heavy metals. Total bacterial number was greatest on the upper most layer of infiltration basin. Slight decreases of bacterial number was observed down to the depth of two meters. There were no significant differences in ratio among major physiological groups of heterotrophic bacteria between layer investigated. The smallest seasonal variation of bacteria was found in the deeper layer below infiltration basin.