The use of ozone in a high density recirculation system for rotifers

The use of ozone in the effluent treatment of a closed recirculation system for rotifers resulted in a significant improvement of rotifer production a nd water quality. Compared to a control treatment, the rotifer culture expo sed to ozone did not only support a higher rotifer biomass (16000 vs. 8000 rotifers ml (1)), it also allowed a prolongation of the culture period for 4 days. Compared to a control treatment, the ammonium levels were reduced b y 67%, nitrite levels by 85% and nitrate levels by 67%. The supplementation of ozone did not affect pH and dissolved oxygen levels. Besides the positi ve effect of ozone to the nitrification process, a better removal of suspen ded solids was noticed as well. This resulted in a decreased turbidity and a reduction of the number of particles in the culture water. The use of ozo ne also reduced the number of bacteria in the culture water. In general terms. it can be stated that supplementation of ozone in a close d recirculation system for rotifers considerably improves water quality, en sures stable and longer rotifer culture periods and controls bacterial prol iferation. (C) 2001 Elsevier Science B.V. All rights reserved.