Managing Water Resources - On-Site Oxygen Generation

South Central Connecticut Regional Water Authority (SCCRWA) West River System draws water from multiple sources, including Watrous Reservoir. Historically, the Water Treatment Plant had difficulty with raw water manganese (Mn) peaks during summer months. Manganese is released from sediments as an anaerobic respiration byproduct when anoxic conditions occur over the water-sediment interface at depth.

Challenge

The elevated summer manganese concentrations (>1.0 mg/L) have impacted raw water intake water quality and the water treatment process. SCCRWA sought to improve on its existing source water management apparatus (2- Layer Aerators and 1- Hypolimnetic Aerator), to increase oxygen at the intake gate depth.
 

Solution

The GZA team designed and conducted a dissolved oxygen consumption feasibility study to identify peak oxygen consumption rate that caused anaerobic respiration and manganese formation in the raw water source reservoir. The GZA team found that climatic impacts have increased oxygen consumption and designed and installed an on-site oxygen generation system to supplement addition of high purity oxygen into the existing apparatus. The results showed anoxic conditions at the target depth were gone, resulting in an 80% reduction of manganese concentrations in the raw water to the treatment plant.

 

Benefit

The benefits of adding on-site oxygen generation to the existing aeration systems include:

• Increase in dissolved oxygen input to existing apparatus
• Decrease of internal loading of manganese from lake sediments
• Reduced treatment cost and production of treatment residuals.
• Added capability to manage impacts of a warming climate.