Implications of Microbial Community to the Overall Performance of Tree-Box Filter Treating Parking Lot Runoff

Most of the studies about stormwater low-impact development technologies (LID) used generalized observations without fully understanding the mechanisms affecting the whole performance of the systems from the catchment to the facility itself. At present, these LID technologies have been treated as black box due to fluctuating flow and environmental conditions affecting its operation and treatment performance. As such, the implications of microbial community to the overall performance of the tree-box filter (TBF) were investigated in this study. Based on the results, summer season was found to be the most suitable season for microorganism growth as greater microorganism count was found in TBF during this season compared to other seasons. Least microorganism count was found in spring which might have been affected by the plant growth during this season since plant penology influences the seasonal dynamics of soil microorganisms. Litterfall during fall season might have affected the microorganism count during winter as, during this season, the compositional variety of soil organic matter changes affecting growth of soil microbial communities. Microbial analyses of soil samples collected in TBF revealed that the most dominant microorganism phylum is Proteobacteria in all the seasons in both inlet and outlet comprising 37% to 47% of the total microorganism count. Proteobacteria is of great importance to carbon, sulfur, and nitrogen cycling in soil. Proteobacteria was followed by Acidobacteria, Actinobacteria, and Chloroflexi which comprises 6% to 20%, 9% to 20%, and 2% to 27%, respectively, of the total microorganism count for each season. Each microorganism phylum was found to have varying correlation to different soil chemical parameters implying the effects of these parameters to microorganism survival in LID technologies. Depending on the target biogeochemical cycle, maintaining a good environment for a specific microbial phylum may be decided. These findings were useful in optimizing the design and performance of tree box filters considering physical, chemical, and biological pollutant removal mechanisms.