United Water Idaho,
Marden Water Treatment Plant Expansion
- Water treatment plant expansion to 16 mgd.
- New pretreatment facilities.
- Independent treatment optimization of multiple raw water sources.
- Sludge lagoon design.
In 1997, United Water Idaho (UWID) awarded Carollo a contract to design an expansion of the 8-mgd Marden Water Treatment Plant to 16-mgd. The work is a continuation of Carollo's recently completed Expansion Alternatives Study and Predesign Study for UWID.
Members of the Carollo design team previously designed the original Marden plant. The original plant design included high-rate conventional treatment with dual-media granular filters, using Superpulsator® upflow clarifiers. The original design provided for treatment (through a single process) of either surface water from the Boise River or groundwater under the influence of surface water from Ranney collectors.
In expanding the Marden plant, Carollo's design allows for the treatment of either source supply to be optimized independently by providing a second inlet structure with its own metering, flow control, and chemical addition facilities. Pretreated water can be separately applied to the filters or co-mingled prior to filtration, depending on the preference of the operators.
The expansion project also includes the addition of a third sludge lagoon. Carollo designed the lagoon system to dewater Superpulsator® sludge and treat filter waste washwater and filter-to-waste. The engineered sludge lagoons feature a hard bottom and sides (6-inch slabs of fiber reinforced concrete), sloped bottoms, decant structures with adjustable downward opening weir gates, polymer addition, and constant-rate recycle flow control.