Water treatment performance of O3/UV reaction system in recirculating aquaculture systems

Abstract: In order to improve the water treatment performance of ozone in recirculating aquaculture systems, and enhance its application safety in the field of aquaculture, the O3/UV integration reaction system were designed. The reaction system was mainly composed of ozone addition dissolved area, ultraviolet catalytic reaction area, stay reaction area. The system was 1 250 mm of high, 750 mm in diameter, and the ultraviolet catalytic reaction was 400 mm in diameter. The working principle of system was that using static mixer way to add ozone, which could dissolve wastewater high efficiency and low energy consumption in ozone addition dissolved area. The wastewater with not completely dissolved ozone bottom up entered to ultraviolet catalytic reaction area, which could generate two advantages. On one hand, under the ultraviolet catalysis, the stronger oxidizing of hydroxyl was produced in further reaction, accelerated the rate of degradation of organic matter, and enhanced the effect of disinfection sterilization. On the other hand, it could reduce the residual amount of ozone in cultivation water, which improved the safety of the device. After treating in ultraviolet catalytic reaction area, the wastewater enter into the reaction area, which the main purpose was to keep a certain residence time of wastewater, and to improve the purification effect of degradation of organic matter and the ammonia nitrogen removal. The relationship of the suitable ozone dosage and wastewater treatment capacity in the ozone additive dissolved area, the process parameters about the ratio of ultraviolet radiation dose and the influence factors of wastewater purification and disinfection sterilization were studied through the test method. The experimental results showed that: 1) Under the condition of meeting with a certain water of dissolved ozone concentration, it could improve ozone dissolution rate and utilization rate through using low ozone inlet flow rate and low water flow. When the wastewater flow was 5 m3/h and the ozone dosage was 8.17 g/h, the ozone dissolution rate was 82.7%, the concentration of ozone in wastewater was 1.53 mg/L and the ozone utilization rate was up to 97.7%. 2) It could improve the removal rate of ozone residual quantity in wastewater by means of increasing the number of UV and lamp power. The effect of performance improvements was more obvious through increasing the number of UV lamp. When the UV additive amount was 1 996 MJ/cm2 and the residual ozone concentration of 1.36 mg/L of influent wastewater in this system, the removal rate of residual ozone could be up to 83.82%, which achieved low residual ozone in aquaculture water and ensured the safety of breeding biology. 3) Compared with using ozone separately, the removal rate of UV254, total organic carbon, chemical oxygen demand and water colour of this system were increased to 109.95%, 89.77%, 29.25% and 51.44%, respectively, and the sterilization removal rate could be more than 97%. The integration reaction system had the feature of disinfection sterilization of aquaculture wastewater, degradation of organic matter efficient, removing water colour and increasing dissolved oxygen, which showed a better wastewater treatment performance.