Ozonation of a recirculating rainbow trout culture system II. Effects on microscreen filtration and water quality

AbstractOzone was added to water in a recirculating rainbow trout (Oncorhynchus mykiss) culture system just prior to the culture tanks in order to oxidize nitrite and organic material, improve overall water quality, and assist removal of solids across the microscreen filter. Data from four 8-week studies on ozonation and an 8-week no ozone control indicated that adding ozone reduced the mean concentration of TSS by 35%, COD by 36%, DOC by 17%, and color by 82% within the water entering the culture tanks. Additionally, ozone reduced the mean nitrite concentration by 82% within the culture tanks. Adding ozone did not affect turbidity. Changes brought on by ozonation, particularly as it affected the characteristics of the suspended solids, also improved suspended solids removal across the TriangelTM filter by an average of 33%. In addition, adding ozone decreased plugging of the microscreen filter panels, as indicated by an average of 35% fewer filter wash cycles, 53% less filter sludge flow produced, and 79% more settled solids volume in the TriangelTM filter effluents. Comparison of two different ozone dosing rates indicated that adding ozone to our recirculating system at a rate of 0.025 kg ozone per kilogram feed was nearly as effective as adding ozone at a rate of 0.036–0.039 kg ozone per kilogram feed