| Ozone is widely used in industrial wastewater treatment because of its good oxidation effect and no secondary pollution.In engineering,ozone is generally added by aeration,which has the advantages of simple reactor structure and no limitation of gas-water ratio,but there are still some problems such as large bubble diameter,low ozone utilization efficiency and general oxidation effect.Ozone micro-nano bubble technology can overcome these shortcomings,and the hydroxyl radical produced in the process of bubble bursting has broad-spectrum oxidation ability,which can greatly improve the ozone oxidation efficiency.Limited by the generation principle of micro-nano bubbles,the gas-water ratio of various methods for generating micro-nano bubbles is generally lower than 10%,and the ozone concentration in water is still low,which restricts the application of ozone micro-nano bubble technology in practical engineering.In order to solve this problem,an ozone dissolved oxidation device with high gas-water ratio is developed by using the theory of gas-liquid two-phase annular flow,and the performance test of the device is carried out,and the efficiency of the new device in treating simulated printing and dyeing wastewater(acid red 18)is verified by experiments.The main results are as following:(1)An ozone dissolved oxidation device with high gas-water ratio was developed.The process is divided into three links:efficient gas-water mixing-gas-liquid pressurizationdissolved gas release.Firstly,the technology of upward co-flow of water and gas and generation of gas-liquid two-phase annular flow by shrinking circular tube is adopted to realize high gas-liquid ratio water mixing,and then the gas-liquid is pressurized to dissolved pressure by using diaphragm pump,and then released under reduced pressure after dissolved in the tank to generate ozone micro-nano bubble water,thus realizing ozone high gas-water ratio dissolved.The determination results show that the highest gas-water ratio can reach 70%when in clear water and the dissolved gas pressure is 0.3 MPa.When the initial ozone concentration is 60 mg/L,the concentration in water can reach 23.26 mg/L,the redox potential can reach 1334 mV and the average bubble diameter is 84.7 μm.With the increase of gas-water ratio,system pressure and initial ozone concentration,the ozone concentration in effluent increases accordingly.(2)The efficiency test of one-way wastewater treatment was carried out by using the new device.When the gas-water ratio is 70%,the system pressure is 0.3 MPa,and the ozone concentration of the gas source is 60 mg/L,the decolorization rate and COD removal rate are only 30.2%and 15.8%,indicating that the single-pass treatment of wastewater is not effective.Although the new device can produce high-concentration ozone water in clean water,the absolute dosage of ozone per unit volume is still very low,and the ozone consumption is fast and the hydraulic retention time is short.(3)The experiment of wastewater treatment efficiency was carried out,and the influencing factors of treatment effect were analyzed.The results show that in the comparison scheme,when the circulating flow rate is 8 L/min,and the other operating conditions are the same as the one-way treatment,the decolorization rate and COD removal rate of Acid Red 18 are 99.5%and 63.3%respectively after 30 min of treatment,which achieves good treatment effect.When the circulating flow rate is increased,the decolorization rate and COD removal rate increase accordingly;When other conditions are constant,the concentration of raw water has a great influence on the treatment effect,and the higher the concentration of raw water,the worse the treatment effect;The water temperature has a certain influence on the treatment effect,and the optimum temperature is 25℃.Alkaline conditions are favorable for ozone oxidation,and the treatment effect is the best when the pH is 9.(4)The treatment effects of acid red 18 by ozone oxidation alone,O3/H2O2 coupling process and O3/Fe/AC coupling process were compared under the circulating treatment mode.The results showed that compared with ozone oxidation alone,O3/H2O2 and O3/Fe/AC coupling process could effectively improve the ozone oxidation capacity,and the COD removal rate increased by 12.1%and 15.2%respectively,and the O3/Fe/AC coupling process has the best catalytic oxidation effect. |
PDF Full Text Request