不同浓度臭氧对循环水养殖系统生物膜活性及其净化效能的影响

Effects of Ozone Concentration on the Activity of Biofilm and Its Effectiveness of Purification in Recirculating Aquaculture Systems

关键词:  臭氧  循环水养殖系统  生物膜  净化效能

Key words:  Ozone  Recirculating aquaculture systems  Biofilm  Purification efficiency

摘要:

本文通过在循环水养殖系统中添加不同浓度的臭氧，研究其对循环水养殖系统生物膜活性及其净化效能的影响。结果显示，当氧化还原电位(ORP)小于450 mV时，氨氮的去除率随着臭氧浓度升高而升高，最高去除率达39.9%，亚硝酸盐氮的平均去除率为28.2%，生物膜菌群的平均存活率为88.1%，生物膜对养殖水体氨氮和亚硝酸盐氮的处理效果良好；当氧化还原电位为500 mV时，经过臭氧24 h处理，氨氮和亚硝酸盐氮的去除率分别由36.5%、28.1%降到12.2%、8.4%，而臭氧4 h处理后，生物膜对氨氮和亚硝酸盐氮的去除率分别由47.5%、32.1%降到5.0%、3.3%，水处理效果明显下降，生物膜菌群存活率由88.1 %降到31.5%。由此可见臭氧添加浓度对生物膜及净化效能有重大影响。综合试验结果和分析评估，建议封闭循环水养殖系统的臭氧添加量以控制生物滤池内的氧化还原电位低于400 mV为宜，可保证循环水系统的安全性和经济性。

Abstract:

Ozone (O3) is a strong oxidizing agent that has been widely used in factory recirculating aquaculture systems. The proper concentration is a key to the utilization of ozone. Ozone at inappropriately high concentration could impair the growth, behavior, and health of farmed fish. Furthermore, ozone at high concentration also affects the biofilm in the biofilter, which could reduce the efficiency of water treatment in the recirculating aquaculture systems (RAS). In this study, ozone was added in RAS at different concentrations, and the subsequent effects on the activity and purification effectiveness of biofilm were tested. It was shown that when the Oxidation-Reduction Potential (ORP) was lower than 450 mV, the efficiency of ammonia nitrogen treatment was increased along with the elevation in ozone concentration. Under this condition the highest removal rates of ammonia nitrogen and nitrite nitrogen reached 39.9% and 28.2% respectively, and the survival rate of bacteria in the biofilm was 88.1%. This suggested that ozone did not affect the efficiency of the biofilter as ORP was below 450 mV. When ORP was 500 mV, after 24-hour treatment with ozone the removal efficiency was decreased from 36.5% to 12.2% for ammonia nitrogen, and from 28.1% to 8.4% for nitrite nitrogen. When ORP was 550 mV, 4-hour ozone treatment reduced the efficiency from 47.5% to 5.0% for ammonia nitrogen, and from 32.1% to 3.3% for nitrite nitrogen. This implied that higher ORP significantly reduced the efficiency of water treatment. The survival rate of bacteria in the biofilm dropped from 88.1% to 31.5%. Our study indicated that the effectiveness of water treatment and the survival rate of bacteria could be greatly affected by ozone. To ensure the safety and cost efficiency of RAS, we recommended that the concentration of ozone added in RAS should be controlled to keep ORP in the biofilter under 400 mV.