Extended Biofiltration for the Control of Microbial Contaminants and Disinfection By-Products
Scott Summers, CU (Project Lead)
The overall goal of this project is to reduce the risk associated with surges in particulate matter, an indicator of microbial contaminants, in source water and in settled water using two innovative filter options that also allow for the control of DBP precursors and preformed DBPs. Objectives include a) Activity 1, develop and evaluate more innovative and novel configurations of coarse-media pre-treatment filtration that increase the flexibility of installation and limit the footprint and b) Activity 2, evaluate the increasing the empty bed contact time (EBCT) for in-plant rapid media filters on controlling surges in particulate matter associated with source water and coagulation process perturbations and on controlling DBP precursors and preformed DBPs.
In phase one of Activity 1, more novel roughing filter configurations that could both enhance performance and simplify filter cleaning and maintenance requirements will be evaluated. The first phase will involve the construction of 2-3 upflow vertical filters and 2-3 surface-loaded horizontal filters. Two configurations that are considered more novel will be evaluated side-by-side in pilot and selected field scale comparisons. Performance of the filters will be monitoring for head loss development, particle removals (turbidity and particle counts), organic DBP precursor reductions (TOC/DOC, UV absorbance and DBP formation), and microbial removals (E. coli challenges, total coliforms, fecal coliforms). In Activity 2, innovative filter modifications and operations will be evaluated with the goal of extending the EBCT to control particulate matter surges, DBPs and DBP precursors. In phase one bench scale tests will evaluate the control of DBPs and DBP precursors by extending the EBCTs up to 30 min. In phase two, both DBP removal by the biofilters and surges in particulate matter will be evaluated only at the UC-B pilot plant. After the baseline is established, particle concentration will be varied to simulate perturbations in the source water, the coagulation process and various stop-start operation conditions. Implementation is planned in Puerto Rico.
The completed assessment of the coarse-media roughing filter configurations and the various design variables will be used by consulting and regulatory engineers to size and specify pretreatment filtration systems that can reduce low quality source waters reaching the subsequent treatment processes especially under surge conditions. Understanding in-plant biofiltration performance under a range of EBCTs, and for a range of DBPs and DBP precursors, will allow the robustness of this very sustainable technology to be assessed. The ability of these long EBCT biofilters to control surges in particulate matter will also be studied under a range of conditions that are often associated with small systems.