The calculation of ozone dosage for disinfection and sterilization in pure water

Ozone is divided into four application fields according to its use: water treatment, food processing, medical and public health, and each field has achieved a high level of research and development of suitable equipment. From a technical point of view, some basic key technologies have been solved, and it is easy to develop a series of marketable products as long as we expand our thinking. Ozone products have strong functions and are high-tech products, and the market has hardly been developed, with great potential. Therefore, seizing the opportunity will certainly bring huge investment returns.

I. Water Treatment
(1) Production of tap water:
The main factor for using ozone instead of chlorine disinfection * currently is also the main reason why traditional chlorine disinfection countries such as the United States and Japan are rapidly adopting ozone treatment for tap water. This is due to the fact that with the source water being polluted by organic chemical industrial products, chlorination will produce chloroform, bromodichloromethane, carbon tetrachloride and other chlorinated organic compounds (THM). These substances are carcinogenic, while ozone treatment does not produce secondary polluting compounds through oxidation. Domestic companies such as Kunming Tap Water Company, Beijing Tiancun Tap Water Plant, Daqing, Shengli and Yanshan Petrochemical have successively replaced chlorine gas disinfection with ozone.

(2) Disinfection and sterilization of mineral water, pure water and high-quality drinking water:
Ozonated water with a concentration of 0.1-1.5mg/L is used to treat pipelines, containers, bottles and barrels in the production line, which has good sterilization effects on bacteria, coliform bacteria, yeast and Aspergillus niger. Ozone sterilization and purification process is the most common in China's bottled water industry, with about 60% of the more than 1000 mineral water, pure water and clean water plants having adopted ozone sterilization technology. Since the technical supervision and epidemic prevention departments have reached a consensus, bottled water plants without ozone equipment will find it difficult to compete in the market. The key lies in that the dissolved oxygen value of the treated water should reach 0.3~0.5mg/L, which requires that the amount of ozone dosage should meet the condition of 2g ozone per cubic meter of water, and at the same time, the water-gas must be fully contacted and maintained for a certain period of time. According to practical experience, ozone concentration above 8% can easily meet the requirement of solubility.

(3) Swimming pool water:
At present, most of the water treatment in swimming pools in China uses chlorine disinfection and copper sulfate antialgae, which often results in bacteria or virus exceeding standards due to low chlorine content in water or high chlorine content in water stimulating human skin, eyes, hair, etc. It is difficult to meet the water quality standards for swimming competitions set by the International Swimming Federation. In international competition swimming pools or some high-end water parks, they all adopt the world's most advanced ozone disinfection technology to carry out ozone disinfection and purification treatment of recycled water to ensure the water quality standards of swimming pools.

(4) Cooling tower water:
At present, the American Cooling Tower Association recommends ozone treatment technology for cooling recirculating water, which can achieve the purposes of scale inhibition, descaling, sterilization, algal removal, corrosion prevention and stable water quality. The American Ozone Company has a computer-controlled ozone cooling recirculating water system in operation.

II. Case Calculation Method:
1ppm=2.14mg/M3
1mg/L=467PPM
1mg/L=1000mg/M3=1g/m3

CT value is the main design parameter of ozone disinfection system
Where C represents ozone concentration in mg/L; T represents contact time in min; The product CT value represents the effectiveness of disinfection process. For example, when the ozone concentration is 0.4mg/L and the contact time is 4min, the CT value is equal to 1.6.

Ozone generator output (g/h) = Recirculating water flow rate (m3/h) × Ozone dosing concentration (g/m3).

Reaction tank volume is determined by the following formula:
Reaction tank volume (m3) = Recirculating water flow rate (m3/h) × Bypass water percentage (%) × Reaction time (h).

Reaction tank volume = radiusradius3.14*height

40 cubic meters of water * 25% * (5/60) = 0.83 cubic meters

0.83 cubic meters with a diameter of 0.8 meters and a height of 0.4 meters = 0.83 / (0.40.4)/3.14 = 1.65

That is to say, a reaction tank with dimensions of 8001700 is needed.

0.83 cubic meters with a height of 2 meters and a radius = 0.83/3.14/2*(square root of 2 times) radius 0.363 2 diameter = 0.727
That is to say, a reaction tank with dimensions of 7302000 is needed.

The unit of ozone generator output is generally g/h, which means how many grams of ozone are generated in one hour. The selection of ozone generator output can generally be calculated by the following formula:
G=k1·Q·M/[ k2（1-k3]
G: Ozone generation output
Q: Water processing capacity per hour
M: Aqueous ozone concentration
k1: Decay factor of ozone generator output (determined by dew point of gas source, electrode and medium cleanliness, generally taken as 1.2-1.3)
k2: Gas-liquid mixing efficiency (different mixing methods take corresponding values)
k3: Ozone decay factor in water (generally taken as 10% for ultrafiltration or reverse osmosis treated water)

For example, if the processing capacity is 5T/h and the required aqueous ozone concentration is 0.4mg/L, and the mixing efficiency of the oxidation tower is 20%, then calculate the output of the ozone generator: G= k1·Q·M/ [k2·（1-k3]=1.3×5×0.4÷[20%×（1-10%）]≈14.44(g/h)

Therefore, considering various factors affecting both sides, the output of ozone generator is determined to be 15g/h.