Services · Existing wastewater plants
Wastewater treatment plant rehabilitation
United Linings and Coatings rehabilitates existing wastewater treatment plant structures by preparing deteriorated surfaces, making prep-level repairs and applying protective coatings and industrial linings, working mainly as a subcontractor to general contractors.
Bidding a plant upgrade or repair package? This page covers the problems that bring these structures back into a contract, how the work is sequenced, the structures United coats and lines, and what it takes to work inside a plant that stays in operation.
01 · The problem
What deteriorates in existing wastewater plants
Wastewater treatment plant concrete and steel sit in a harsh mix of moisture, chemistry and flow. Rehabilitation usually starts because one or more of these conditions has reached the point where patching is no longer enough:
- Corrosion above the waterline. Hydrogen sulfide released from wastewater can lead to acid attack on concrete and metal in headspaces and vapour zones.
- Abrasion and erosion at weirs, troughs, launders and flow channels.
- Failed or aged coatings: blistering, cracking, delamination and bare spots.
- Surface loss: spalls, exposed aggregate and rough, porous concrete that needs preparation before any new system can bond.
Background: U.S. EPA, Design Manual: Odor and Corrosion Control in Sanitary Sewerage Systems and Treatment Plants (EPA/625/1-85/018).
02 · The method
How wastewater plant rehabilitation is sequenced
Each structure follows the same basic sequence, with the details set by the project specification:
- Review the structure, the specification and the access plan.
- Take the unit out of service, coordinated with the plant and the general contractor.
- Prepare surfaces by abrasive blasting and cleaning.
- Make prep-level repairs to the concrete surface where needed.
- Apply the specified coating or lining system.
- Inspect and test before the unit returns to service.
- Lining surface The finished face in contact with wastewater or vapour
- Immersion-grade lining Thickness per specification, checked as dry film thickness (DFT)
- Primer or first coat Bonds the system to the prepared surface
- Minor surface repair Prep-level patching where the surface needs it
- Prepared concrete Profile per SSPC-SP 13 / NACE No. 6 and ICRI CSP, as specified
Schematic, not to scale. Actual systems follow the project specification. Tested before service: holiday, adhesion, DFT.
03 · Capabilities
Coatings, linings and surface preparation
Capability 01
Protective coatings & linings
Epoxy coatings and industrial linings for concrete and steel in wastewater service, applied to the project specification.
Capability 02
Surface preparation & abrasive blasting
Abrasive blasting, coating removal and prep-level concrete repairs, the work that decides how long a new system lasts.
04 · Structures
Structures United coats and lines
Clarifiers
Troughs, launders, weirs, walls and floors.
Tanks & basins
Aeration basins and process tanks.
Digesters
Interior coatings in liquid and vapour zones.
Wet wells & lift stations
Linings for below-grade structures.
Digester coating and rehabilitation
Digester coating work has to suit two exposures at once: the liquid zone and the gas-filled vapour space above it, where corrosive conditions are often most severe. Temperature and the digester’s chemistry add to the demands on the system.
Before coating crews can enter, the plant and general contractor empty, clean and clear the digester for confined-space work. United then prepares the interior surfaces, makes prep-level repairs and applies the specified coating system.
Technical background: Sherwin-Williams Protective & Marine, coatings for clarifiers and digesters (manufacturer guidance).
Wet well and lift station linings
Wet wells and lift stations collect wastewater below grade, and the concrete above the operating water level is often where corrosion shows first. Lining these structures means planning bypass pumping, confined-space entry and access through limited openings.
With the structure bypassed and cleaned, United prepares the surfaces, makes prep-level repairs and applies the specified lining system before the station returns to service.
05 · Constraints
Working inside an operating wastewater plant
Treatment plants usually keep operating during rehabilitation, so the coating scope has to fit around the plant’s operation:
- One unit out of service at a time, while parallel units carry the flow
- Flow diversion or bypass pumping arranged with the plant and general contractor
- Confined-space entry and ventilation for tanks, digesters and wet wells
- Containment of blast media and dust
- Cure time before a structure is refilled or returned to service
06 · Project records
How projects are documented
Each project record sets out the asset, its condition, the scope, the method and the constraints. The records currently shown are illustrative samples of that format, not completed United work.
Illustrative sample project — not completed United work
Digester interior coating (sample format)
- Asset
- Anaerobic digester (concrete tank)
- Scope
- Surface preparation · prep-level surface repairs · protective coating of interior surfaces
Illustrative sample project — not completed United work
Aeration basin lining (sample format)
- Asset
- Aeration basin (rectangular, concrete)
- Scope
- Surface preparation · prep-level surface repairs · immersion-grade lining of walls and floor
Illustrative sample project — not completed United work
Secondary clarifier rehabilitation (sample format)
- Asset
- Secondary clarifier (circular, concrete)
- Scope
- Surface preparation · prep-level surface repairs · protective lining of launder and wall surfaces
Questions
Wastewater plant rehabilitation questions
What does wastewater treatment plant rehabilitation include?
Rehabilitation work on existing wastewater structures usually covers surface preparation such as abrasive blasting, prep-level repairs to the concrete surface, and a protective coating or lining system applied and tested to the project specification before the unit returns to service.
Can coating work happen while the plant stays in operation?
Plants typically stay in operation. Work is scheduled one unit at a time, with flows diverted or bypassed by the plant or general contractor, so a clarifier, basin or wet well can be emptied, prepared and lined while the rest of the facility keeps treating wastewater.
Have a wastewater coatings scope out to bid?
Send the bid date and the specification sections, or see how bidding with United works.