AWWA ACE56311

Many small- to mid-size utilities are planning to upgrade their water treatment plants both to expand capacity and to meet new regulations. Many of these utilities currently use a conventional treatment scheme, and, as these utilities now consider modifications to their plants, the question often asked is whether to change the treatment scheme to achieve a higher quality water at a more cost-effective price. This paper discusses the advantages and disadvantages that these utilities should consider in evaluating treatment processes, including conventional treatment (both with and without enhanced coagulation), ballasted flocculation, upflow and reactor clarifiers, dissolved air flotation, and membrane treatment. In evaluating these processes, many decision factors were considered, including raw water quality, treatment effectiveness, ability to meet existing and proposed regulations, capital costs, operation and maintenance costs, ease in retrofit, and life-cycle costs. As a model, a decision scheme was set up for an example town whose treatment plant is in the process of expansion. The town's existing plant utilizes conventional treatment, and, due to certain resource limitations and raw water quality parameters, the town would like to evaluate different options for expansion. Includes 3 references, tables, figures.