AWWA MTC61134

Given the many reverse osmosis (RO) and nanofiltration (NF) membrane plants in service in the United States and elsewhere, and the continuing rapid growth of the technologies for municipal water supply, one would think that proven, no-risk post-treatment process design and operation after construction and commissioning would be very routine. However, there have been a number of cases where improper product water post-treatment design has resulted in significant water quality problems in the distribution system, such as corrosion (e.g. red water), precipitation (e.g. turbidity), loss of proper disinfectant residual, and other problems. Post-treatment processes can vary widely based on the specific application and location, membrane system permeate water quality, ability for membrane bypass/blending, materials of construction and condition of existing distribution system, water quality from other water supply sources, potential for blending at the treatment facility and in the distribution system, and finished water quality goals. This paper discusses the types of post-treatment process facilities and chemicals commonly being used today and the design approach that should be used for proper evaluation and selection of the post-treatment alternatives. Includes tables, figures.