D006 City of Devine WSC

City of Devine Water Treatment Plant, located at the end of LC Martin Drive, has a well pump with a 200-gpm `capacity. Laboratory analysis of the well water showed higher iron and manganese content, exceeding the TCEQ requirements of 0.30 mg/l for iron and 0.05 mg/l for manganese. The well water has an iron content of 4.2 mg/l and a manganese content of 0.114 mg/l.

WETS installed an aeration water treatment unit in 2015 as stand-alone aeration unit was sufficient for manganese and iron removal from water. The well was abandoned for five years and in 2020 Garcia Engineering consulted us to perform a pilot study.

Multiple pilot testing arrangements were performed using pilot aeration and pilot filtration. The pilot filter used dual-media with sand and anthracite and dual-media with Greensand Plus and anthracite. The performance of the dual media with Greensand Plus was more satisfactory, thus WETS recommends the use of Greensand Plus with anthracite in dual-media gravity filters. The use of Greensand Plus requires the use of sodium hypochlorite (liquid chlorine) solution. The liquid chlorine is already being injected into the line to the GST which means the existing system can be reused with the injection point being relocated.

To accommodate the addition of the gravity filtration system, the existing aerator discharge piping would need to be modified to install the gravity filters before the existing

GST. The existing chlorine injection point would be relocated, used to both maintain the oxidation capability of the Greensand Plus and provide the overall system discharge free chlorine residual level. The filter outlet free chlorine residual level of 3 mg/l required for the Greensand Plus oxidation can be used to meet the overall free chlorine residual requirement in the GST. For the City of Devine, WETS designed and manufactured two dual-media gravity filters with Greensand Plus and anthracite for iron and manganese removal. The design was based on the results of a WETS pilot study.