Overview

Central Wayne Regional Authority (CWRA) operates a 2.2 mgd wastewater treatment plant that serves the Borough of Honesdale and three surrounding townships. Operators noticed that the three Sequencing Batch Reactor (SBR) tanks and one decant/equalization tank, all constructed of concrete, were beginning to show degradation. The cement was wearing away, exposing aggregate and deep pits on the interior walls and floors.

Entech researched a number of long-term solutions. When planning the rehabilitation, careful attention was given to identifying a period of low flow at the plant so tanks could be taken offline for repairs without impacting the treatment processes.

Entech’s evaluation determined that 1/2” to 1” of concrete cement had degraded. In order to prevent additional degradation, exposure of the rebar, and leaking, various coating systems were evaluated for the walls and floors that would ensure long-term protection. Working with several coatings manufacturers and painting contractors, Entech presented several coating options to CRWA, including a thick solidepoxy system, and a high build epoxy-urethane system. The CWRA selected the epoxy-urethane option, as the additional cost was very low considering the added flexibility that the coating system would provide over the wall joints.

Surface preparation and coating followed these steps:

• The tank interiors were hot pressure washed to remove oils and contaminants, then blasted to remove loose concrete and old coatings.
• An epoxy-polymer modified cementitious resurfacer was applied to all surfaces and used to fill in deep pits.
• Transition areas for the coating system (top of walls, corners and edges) were notched.
• All surfaces received an epoxy primer basecoat.
• Wall joints were recaulked and bond-breaker tape applied over them.
• All surfaces received an elastomeric polyurethane finish coat.

Record rainfall in spring and early summer delayed tank draining until July, when the flow through the plant was reduced, and the plant could operate at a diminished capacity. Two tanks were taken offline at a time and rehabilitated, with tarps enclosing the open-top tanks in order to keep the application of the new coatings out of direct sunlight, as required by the manufacturer. The first set were completed in eight weeks. With lessons learned, the remaining two tanks were prepped and coated in just six weeks. A full-time coatings inspector was on site to ensure the project specifications were followed, and manufacturer’s requirements for the surface preparation, atmospheric conditions, and coating process were achieved.

Entech provided the design, an engineer’s opinion of probable cost, bidding services, services during construction and construction observation for the project.

Not only did we help CWRA to evaluate and identify a great long-term coating option for the tanks, we helped them to schedule and complete the project in a manner that did not hinder plant operations. The rehabilitated tanks will serve CWRA for many years to come.