AWWA WQTC59023

The Tecumseh Water Treatment Plant (WTP), constructed in 1958, is a conventional treatment plant that treats raw water from the Peche Isle Channel in Lake St. Clair near the mouth of the Detroit River. The design capacity of the plant is 27.3 MLD. The treatment train includes coagulation, upflow clarification and granular media filtration. The plant also occasionally uses powdered activated carbon (PAC) to control trace levels of atrazine. In addition, the plant currently discharges its filter backwash to the lake and is therefore required to limit the total suspended solids concentration in its waste discharge to the lake to below 25 mg/L. The raw water is characterized by high turbidity, ranging from less than 1 NTU to greater than 100 NTU, low TOC, with occasional high color and high coliform counts. Lake St. Clair is a popular summer vacation spot and the surrounding water body is used for a number of recreational water activities during the warmer weather which can result in high fecal coliform concentrations in the source water. Due to both the age of the facility, and expected demand increases in the future, the WTP is in need of major upgrades. For instance, the existing upflow solids contact clarifier does not consistently perform well during high turbidity events and can limit the plant capacity to 19.5 MLD. Plant upgrades are also necessary to meet the anticipated disinfection requirements of new regulations. The Town considered several alternatives to improve its finished water quality while meeting anticipated higher demand for water. Implementation of microfiltration (MF)/ultrafiltration (UF) membrane filtration offers several advantages over conventional treatment such as increased finished water quality, smaller foot print, ease of expansion and high-level of automation. Therefore the Town wanted to implement membrane filtration to meet all of its objectives. Due to space constraints dictated by limited land availability and to limit the financial burden to its consumers, the Town investigated the possibility of directly treating the raw water with membrane filtration. To address the occasional color and taste occurrences, several of the existing conventional filters would be maintained downstream of the membrane filtration and be used as granular activated carbon beds. The existing clarifier would be modified to treat backwash water from the membrane filters to meet the allowable suspended solids concentration limit upon discharge. This paper presents the approach the Town of Tecumseh had taken to implement membrane filtration into its existing plant, in particular the results of the pilot study that was conducted to investigate the feasibility of membrane filtration in treating raw water without any pretreatment and the membrane procurement process based on pilot results and their incorporation into the existing plant. Includes tables, figures.