Congratulations P. Leigh Gilmore Terry on winning first place poster at the ACE16AWWA!
Abstract for the conference:
Understanding the Performance of Extended EBCT Biofilters Based on Biomass Development and Distribution within Small Scale Systems
Leigh Gilmore and R. Scott Summers
Extending the empty bed contact time (EBCT) of a biologically active filter (biofilter) can significantly improve the performance for controlling organic contaminants. For systems with excess plant capacity, like many small systems, this can be done without addition capital investment. However, understanding when this extended EBCT approach is advantageous requires an understanding of the distribution of biomass throughout biofilters and relating it to biofilter performance. Microbial activity in biofilters is important for dissolved organic matter (DOM) removal efficacy and may be influenced by various water quality parameters and filter operations, such as influent DOM, temperature, and backwashing conditions. Adenosine triphosphate (ATP) is the primary energy carrier in all living cells and is used for cell synthesis and maintenance. Quantification of ATP has been used as an indicator of biomass in drinking water biofilters. Research has shown that at shorted EBCTs and colder influent water temperatures, DOM removal in biofilters decreases, but effects on biomass activity are unknown. Investigation of how sample depth affects ATP concentration is needed, taking into consideration influent DOM, temperature, and filter backwashing. In addition, extrapolymeric substances (EPS) will be monitored before and after backwash. The goal of this work is to comprehensively study the development and distribution of biomass in rapid biological filters and develop a ‘healthy’ biomass distribution profile. The overall objectives of the research are to evaluate the effects EBCT, temperature, filter backwashing, and influent DOM have on biomass stratification throughout the filter.
Pilot filters were set up at the City of Boulder’s (CO) Betasso Water Treatment Plant to evaluate the effect of increasing the EBCT for in-plant rapid media filters on biomass activity and controlling surges in particulate matter associated with water and coagulation process perturbations. We modified the influent system and fabricated two new filter columns with taps at depths that represent 5, 15 and 30 minute EBCTs. Filter 1 was packed with ‘fresh’ anthracite and Filter 2 was packed with ‘bioacclimated’ anthracite from Longmont (CO) Nelson Flanders Water Treatment Plant, to compare the development and performance of the fresh anthracite to the bioacclimated anthracite. The filters have been online for 6 months of the winter, spring and summer and are capturing surges in turbidity (2 to 35 NTU) and NOM during spring runoff (2 to 7 mg/L total organic carbon), with temperature fluctuations of 5 to 20 °C. Biomass activity and filter performance are being monitored at each EBCT over the seasonal changes and coagulation doses (3 mg/L and 15 mg/L). Extended biofiltration will improve the sustainability of small drinking water systems by providing additional NOM removal, and a biomass distribution profile will allow utilities to predict DOM removal based on biomass activity.