Removal of disinfection byproduct precursors by granular activated carbon: Hillsborough county water treatment facility case study

To control disinfection by-products (DBPs) formation, removing the organic precursor before the disinfectant application is important. Granular activated carbon (GAC) is widely used in water treatment plants due to its cost-effectiveness. To assist the Hillsborough County Water Treatment Facilities (HCWTFs) to optimize the design of GAC systems, the efficiency of different GACs with different empty bed contact times (EBCTs) was assessed. This study evaluated the performance of GACs for removing organic precursor from groundwater with both batch and column tests. Coconut shell-based (CS) GAC has the highest adsorption capacity (2.83 (mg/g) (L/mg) 1/n ) and the lowest adsorption rate (3.54 × 10 −5 g/mg∙min). Rapid small scale column tests (RSSCTs) were conducted with EBCT of 1 and 1.5 min to evaluate adsorption performance. F400 treated more water at the breakthrough effluent TOC concentration of 1 mg/L than the other two GACs. A preliminary capital cost and operating and maintenance (O&M) cost of the full-scale implementation of the GAC system were estimated and the selection of GAC and EBCT led to the trade-offs between system capital costs and O&M costs. From an economical perspective, F400 with 15 min EBCT is the best option with the lowest total annual cost. Additionally, simulated distribution system (SDS) tests were performed with F400 treated water from the pilot study which indicated a significantly lower chlorine demand (1.95 mg/L) and DBP formation (HAA is 9 μg/L and THM is 11 μg/L) at 96 hours when compared with raw groundwater.