AWWA MTC61113

The City of Abilene, Texas has expanded its water supply and treatment facilities to combat a dwindling fresh water supply. Abilene has begun treating a brackish surface water supply (Lake O.H. Ivie, total dissolved solids (TDS)~ 1,200 mg/L, high barium sulfate scaling potential, color 20-40 CU), which requires the use of an advanced treatment process to achieve acceptable finished water TDS and color levels. Based on the raw water quality, a dual membrane system (microfiltration followed by reverse osmosis) was selected to accomplish the treatment goals. The Phase I capacity of the water treatment facility is 6-mgd with future expansions possible to 18-mgd. This paper describes the development of the overall project, which includes source water quality and removal requirements, treatment process selection, and facility design. It then discusses the plant construction, commissioning, and operation of the facility. Treatment challenges include color removal, salinity reduction, turbidity control, and pathogen removal and/or inactivation from the surface water supply sources. Furthermore, the membrane-treated product water is blended in the distribution system and must be compatible with water from existing supply and treatment facilities. The primary treatment process includes ferric sulfate coagulant addition (color and dissolved organic carbon (DOC) reduction), microfiltration (MF) for suspended solids and pathogen removal, and split stream reverse osmosis (RO) for dissolved solids reduction. Final treatment steps include disinfection (free chlorine for virus removal and chloramines for residual disinfectant), and pH adjustment and corrosion control (sodium hydroxide). Some of the MF product water bypasses the RO treatment and blends with RO permeate which reduces the needed RO capacity and lowers overall costs. Includes tables, figures.