Views: 99 Author: Yosun Publish Time: 2024-04-17 Origin: Site
Dissolved Air Flotation (DAF) air flotation water purification technology is a solid-liquid separation technology that has rapidly developed in the past thirty years. Its principle is to dissolve air into water under pressure and then dissolve it under reduced pressure. Release air to produce a large number of tiny bubbles. The interaction between tiny bubbles and particulate matter includes complex processes such as adsorption, flocculation, and hydrodynamics.
Make the bubbles adhere to the suspended particles, forming a mixed body with an overall specific gravity of less than 1. Since the buoyancy is greater than the gravity, the mixed body floats to the water surface to form scum, and the clean water flows downward, collecting the scum and clean water respectively to achieve solid-liquid separation. sewage can be purified. In the field of water treatment, Air flotation water purification technology is widely used at home and abroad.
The earliest air flotation technology dates back to the early 20th century. At that time, bubbles were mainly generated by directly introducing air or other gases into the water. However, the bubbles generated by this method were relatively large and inefficient. In 1930, a paper mill in Sweden used air to be dispersed in water under pressure to treat sewage. The essence was to divide the compressed air into tiny bubbles through microporous plastic plates and scatter them in the water to achieve air flotation. This was the prototype of diffuse air flotation.
The development of air flotation at this stage is prolonged. The main reason is that the technology for manufacturing microbubbles is immature. When using dispersed air flotation, the bubbles produced are not satisfactory enough, the adhesion ability of the particles is inferior, and giant bubbles will also cause severe turbulence. The flow breaks up the floc. At that time, air flotation was not widely used and was mainly used to treat wastewater containing impurities with small specific gravity, such as oil, fat, and fiber.
To solve the problem of microbubbles, people invented electrolytic air flotation (Figure 1). Electrolytic air flotation uses insoluble anodes and cathodes, directly passing the direct current to electrolyze wastewater.
The anodes and cathodes produce hydrogen and oxygen to form microbubbles. The bubbles adhere to the pollutant particles or flocs in the wastewater and float to the water surface. The bubbles created by electrolysis are much smaller than those formed by the diffusion method, but the operating cost is too high and difficult to promote.
Impeller air flotation (Figure 2) uses a motor to drive the impeller to rotate at high speed. The air is crushed into fine bubbles and mixed with water to form a water-air mixture. The bubbles drive impurity particles in the water to float. This air flotation equipment is suitable for treating wastewater with high concentrations of pollutants, but the treatment capacity is not significant.
figure1
figure2
After World War II, with the development of industrialization, the demand for more efficient water treatment methods increased daily, and dissolved air flotation technology was further improved.
It was not until the birth of pressure-dissolved air flotation in the 1950s that air flotation embarked on the fast track to development. The high-pressure dissolved air system injects clean water and compressed air into the dissolved air tank through a water pump and air compressor, and the pressure is 0.3~0.5Mpa.
In the sealed air-dissolving tank, the high-speed movement of the water in the nozzle and mixing tube allows the air to fully dissolve quickly. Then, it is decompressed and released through the releaser under normal pressure, forming a large amount of water with a diameter of 20~50um. The microbubbles and flocs in the water create a stable mixture with a specific gravity of less than 1. Due to the buoyancy, the mixture floats to the water surface and separates from the water.
Progress in scientific research and technological innovation provide higher efficiency and stability for dissolved air flotation equipment. Through the design optimization of critical components such as the gas-liquid mixing chamber, bubble generation system, and slag scraping machinery, as well as the introduction of intelligent control systems, dissolved air flotation technology has become more efficient, energy-saving, and environmentally friendly.
In the late 1960s, pressure-dissolved gas devices were already used in my country to purify salt solutions and treat petroleum wastewater. In the 1970s, air flotation technology developed rapidly, and modern air flotation technology was formed.
Our company entered the field of sewage treatment in 2005 and began to build and manufacture solid-liquid separation equipment in 2011. After years of development, we currently produce high-efficiency dissolved air flotation. The particle size of microbubbles is 10-30μm, and the residence time in water is longer. Gas-water mixing efficiency is higher than 95%. Some new methods have been developed based on the traditional air flotation process, such as the vortex concave air flotation (CAF) process, the Highly Efficient shallow Air Flotation process, etc. (See Figure 3.4.5).
Dissolved Air Flotation
Highly Efficient shallow Air Flotation
vortex concave air flotation
We adopt flexible manufacturing technology in production and use computer-aided design (CAD), computer-aided manufacturing (CAM), and digital intelligent control systems to improve production efficiency and reduce human errors. The continuous iterative upgrade of our company's air flotation products also reflects the development and update process of air flotation technology.
Dissolved air flotation technology has become an indispensable part of sewage and wastewater treatment, especially showing remarkable results in removing floating oil, suspended solids, algae, and some refractory organic matter. With the continuous advancement of science and technology, it can be expected that this technology will continue to improve and contribute more innovative solutions to the water treatment industry.
In the future, dissolved air flotation technology is expected to achieve more extraordinary breakthroughs and innovations in many aspects.
First, researchers may explore new nanobubble generation methods in terms of bubble generation technology. Due to their smaller size and higher specific surface area and activity, nanobubbles are expected to improve the removal efficiency of suspended solids and pollutants by dissolved air flotation technology. In addition, nanobubbles have excellent stability and can exist in water for long periods, extending the processing time window.
Secondly, dissolved air flotation technology may be combined with other water treatment technologies to form a more efficient, comprehensive treatment system. For example, combining dissolved air flotation with advanced oxidation technologies (such as ozone, hydrogen peroxide, etc.) can more effectively degrade refractory organic matter and improve effluent quality. In addition, combining dissolved air flotation with biological treatment technology (such as the activated sludge method, biofilm method, etc.) can make full use of the degradation effect of microorganisms and improve the overall treatment effect.
Thirdly, with the continuous development of artificial intelligence and big data technology, dissolved air flotation equipment may become intelligent and automated. By introducing an innovative control system, water quality, and treatment effects can be monitored in real time, and equipment operating parameters can be automatically adjusted according to conditions to achieve optimized operation. In addition, we can gain an in-depth understanding of water quality changes and pollutant removal mechanisms through extensive data analysis, providing strong support for improving equipment design and treatment effects.
Finally, dissolved air flotation technology may expand to more application areas. In addition to the traditional fields of sewage treatment, industrial wastewater treatment, and drinking water purification, this technology may also be applied to marine pollution control, water eutrophication control, and other aspects. By continuously broadening its application fields, dissolved air flotation technology is expected to contribute more to environmental protection and sustainable development.
In short, with the continuous advancement and innovation of science and technology, dissolved air flotation technology is expected to achieve more extraordinary breakthroughs and development in the future. By continuously optimizing equipment design, introducing new technologies, realizing intelligence, and expanding application fields, this technology is expected to bring more innovative solutions to the water treatment industry and contribute more to environmental protection and sustainable development.
