Challenge

Biological slimes (biofilms) which formed throughout the system, the cooling tower basin, and the high efficiency film fill, reduced plant production rates. All previous approaches to control the biofilm were unsuccessful.

Solution

A recommendation was made to feed chlorine dioxide to the cooling tower basin through several stingers, to help dissolve biological slime in the basin. Because of ammonia leaks in the system, chlorine dioxide was fed three times daily.

Results

Four major results were accomplished:

1. Microbiological costs were about 50% of previous treatment
2. Corrosion rates were reduced by greater than 50%
3. Dramatic improvements in heat transfer
4. Measurable improvement in plant production rates

The plant records ‘delta-T’, which is the difference between the cooling water basin temperature and the process temperature out of that exchanger. A lower delta-T indicates an improved exchanger efficiency. After chlorine dioxide feed was implemented, there was an immediate and dramatic trend toward lower temperatures. The delta-T has leveled out at 6–9°F, where it has remained. The increase in production is estimated by plant personnel to be valued around $70,000 per month.