Expansion of the Still Branch Regional Reservoir Treatment Plant 2013-2014
In 2006 the City of Griffin Still Branch WTP was complete as a greenfield project with a capacity of 8 million gallons per day (MGD) with some components, such as the filters, sized for 12 MGD. In the 2013 the Still Branch Regional Reservoir Treatment Plant has start the plant is undergoing construction for expansion to 12 MGD and is expected to be completed in 3 rd quarter of 2014 at a cost of 6.1million dollars.
The expansion is Georgia’s first Dissolved Air Flotation (DAF) system used in the treatment of finished drinking water. The upgrade will give the regional system redundancy of supply to the system and a backup system of a full 12 MGD and allow for future expansion to 24 MGD.
The expansion is part of the City’s water system capital improvement plan and is needed to better service its retail and wholesale customers. The project is engineered to improve water efficiency in the processing of drinking water resulting less cost to produce water delivered to the system.
Raw water from the Flint River is pumped from the river pump station into the 475-acre reservoir from where it is pumped to the Still Branch WTP. Aeration of the reservoir will be evaluated to minimize iron and manganese levels, taste and odor problems and algae blooms. Potassium permanganate will continue to be added as needed at the reservoir pumping station to oxidize iron and manganese. Lime will be added to the raw water as necessary to increase the pH for proper coagulation conditions. Alum or other aluminum salts will then be fed at the rapid mix stage for coagulation with polymer added as needed. Chlorine dioxide will be added before or after rapid mixing for pre-oxidation/disinfection. A minimum CT for 0.5-log inactivation of Giardia cysts with chlorine dioxide is proposed. Next, mechanical flocculation and clarification with DAF is proposed. Powdered activated carbon will be added to the DAF basin effluent for taste and odor control and chlorite reduction. An application point for the addition of a filter aid polymer prior to filtration will be included. A chlorine application point prior to the filters is also proposed. This chlorination point will only be used to chlorinate the filters if biological growth occurs in the filters. Clarification will be followed by high rate, dual media filtration. Chemicals for disinfection, corrosion control, and dental hygiene will be fed after filtration, prior to the clearwell. One clearwell will be added to supplement the existing single clearwell. The two clearwells are proposed to provide storage and contact time for a minimum of 1.5-log inactivation of Giardia cysts with chlorine, which will result in a total of 4-log inactivation of Giardia (2.5-log for clarification/filtration and 1.5-log chlorine). Lime will be added after the clearwell for pH adjustment prior to discharge into the distribution system.