BACKGROUND:

An orange juice concentration plant in Florida experienced severe accumulation of
biofouling in the cooling tower system serving a taste evaporator. The vacuum is provided
by steam ejectors and barometric condensers, and carry-over of nutrients from the
evaporators enters the cooling water system via the barometric condenser. Treatment with
chlorine and bromine had not been effective; treatment with chlorine dioxide had been
somewhat effective, but costs were high due to the high demand of oxygen in the cooling
tower system.

TREATMENT:

The cooling water system has a circulation rate of 4800 gpm and a hold-up of 28,000
gallons. Daily dosage was at a rate of 4 ppm (based on the circulation rate) for 20 minutes,
at which time the system concentration approached 16 ppm based on the total system
volume.

RESULTS:

Within a few hours of the initial treatment, large clumps of biomass had been dislodged from
the tower internals and were floating in the basis. After three weeks of treatment, an
estimated 75% of the biofouling in the cooling tower had been dispersed; at that point, an
equilibrium seemed to be established, where the rate of growth of biofouling was equal to
the rate of dispersion. It was also noted that the remaining deposits had been loosened
such that they were easier to remove by manual cleaning.

CONCLUSIONS:

The use of Mexel 432 will be continued and extended at this facility.