As the fifth largest city in Arkansas, Jonesboro’s population growth and industry expansion is quickening in pace. Growth must be met with improved infrastructure, a challenge for which City Water & Light (CWL) turned to Olsson. In this instance, for the expansion and upgrade of the East Side Wastewater Treatment Facility (WWTF).

The project involved hydraulic capacity improvements to mitigate higher projected peak wet weather flows. These improvements include additional influent pumping capacity and additional clarification units. At the projected peak flows, the hydraulic loading rate of the clarifiers would exceed industry standards and risk loss of solids in plant effluent.

The capacity of the existing 13.5 MGD treatment plant was greatly increased. The capacity of the new UV system is 36 MGD, and expandable to a future capacity of 45 MGD, the projected peak wet weather flow at ultimate build-out. Increased capacity at the plant, and other planned sewer improvements, will reduce collection system overflows.

A new UV disinfection facility was designed to replace chlorine disinfection and better address NPDES permit limits for total residual chlorine. Switching to UV disinfection was selected because the new discharge permit limit was so low that it was not practical to use chlorine and still meet permitting requirements.

The benefits of UV disinfection over chlorine disinfection are multiple. In terms of plant efficiency and safety, UV disinfection eliminates the need for chlorine and associated employee safety factors and additional processing steps to remove excess chemicals prior to the release of treated effluent, all of which result in better efficiency and reduced cost.

New clarifiers were constructed with fiber-reinforced plastic (FRP) launder covers to reduce maintenance. Launder covers are used to prevent algae growth and protect the clarifier from debris.

When left unchecked, algae may disrupt clarifier efficiency and could eventually damage the purification system. These covers help control algae growth, leading to cleaner water. Density current baffles were also added to improve removal of total suspended solids (TSS) from effluent.