Restoring Essential Filtration Infrastructure

After 22 years of operation, two sand filter tanks exhibited severe internal corrosion and pitting do to a microbial induced corrosion attack (MIC), with damages ranging from 0.100 to 0.230 inches in depth. Previous inspection teams recommended complete replacement due to structural liabilities, but this approach would cause significant downtime and operational challenges for the facility’s filtration system.

Experience always overcomes challenges

CFES addressed two critical challenges with an innovative solution:

Severe corrosion and holes in the lower cone and shell courses necessitated comprehensive reinforcement.
Avoiding a full system shutdown required a method to rehabilitate one tank while keeping the other operational.

Inspection and Preparation

CFES carried out detailed inspections and preparations to set the stage for successful repairs:

Damage Assessment:
- Identified serveral holes and widespread pitting in critical areas.

Surface Preparation:
- Cleaned and disinfected the MIC affected surfaces followed by grit blasting to ensure proper bonding for the composite reinforcement.

Innovative Repair Methods

Using Carbon Fiber Reinforced Polymer (CFRP) composites, CFES provided a durable and cost-effective rehabilitation:

CFRP Installation:
- Applied a single layer of CFES Style 1210 Fiber Glass and three layers of CFES Style 1266 carbon fiber fabric to the lower cone and tank walls to restore structural integrity.
- Reinforced damaged areas with two additional carbon fiber layers for added strength.

Protective Liner Application:
- Installed CFES S-Epoxy a 100% solids epoxy liner over the CFRP system and remaining tank surfaces to prevent future corrosion.

Staggered Rehabilitation:
- Rehabilitated one tank at a time to maintain operational capacity and avoid costly shutdowns.

Key Outcomes

Extended Lifespan: Restored structural integrity and corrosion resistance extended the tanks’ service life.
Minimal Downtime: Rehabilitation allowed uninterrupted operation of one tank while the other was repaired.
Cost Efficiency: Avoided the expenses and complexities of full tank replacement.
Improved Durability: The wear-resistant liner provided long-term protection against future damage.