About Primary Wastewater & Combined Sewer Overflow Treatment

• Some wastewater treatment plants only utilize a primary treatment process and do not use any form of secondary or tertiary steps

• Primary treatment usually consists of bar screens, grit chambers, and sedimentation tanks – the goal of primary treatment is to remove large objects, particles, and suspended solids

• Combined sewer systems are sewers that are designed to collect rainwater runoff and domestic wastewater in the same pipe – during periods of heavy rainfall or snowmelt, the wastewater volume in a combined sewer system can exceed the capacity of the wastewater treatment plant and overflow directly into nearby streams and rivers

• The treatment of combined sewer overflows (CSOs) is a growing regulatory requirement in many regions

High flow rates and volumes, combined with the inherently high suspended solids concentration, variable temperature, and microorganisms seen in low quality wastewater applications requires a treatment technology with rapid oxidation and powerful microorganism-treatment capabilities.

UV & Chlorine

Traditional treatment, such as chlorine, has rapid oxidation capabilities and is relatively low cost, however, effective treatment can require a lengthy contact time which can necessitate the need for substantial footprint expansion and construction costs. In addition, the high chlorine dosages applied can potentially result in a high level chlorine residual and by-products in receiving waters. This has prompted municipalities to look for more options, notably UV.