Theory and application of air floating water purification technology

The gas flotation method uses highly dispersed microbubbles as a carrier to adhere to suspended matter in wastewater, so that its density is less than water and float to the surface to achieve solid-liquid separation process. It can be used for the separation of ions in water solids from solids, solids from liquids, liquids from liquids and even solutes. As an efficient and rapid solid-liquid separation technology, gas flotation began in mineral processing.

Buoyancy advantage

Since the 1970s, the technology has attracted the attention of scholars at home and abroad in the field of water treatment and has been rapidly developed. At present, it has been widely used in water supply, especially in the purification treatment of low temperature, low turbidity and algae-rich water bodies, and the treatment of urban domestic sewage and various industrial wastewater. Compared with the precipitation method, the gas flotation method has four advantages:

(1) Air flotation equipment covers less land and saves infrastructure investment;

(2) The treatment effect is good, and the plankton in the low turbidity algal water and raw water that are difficult to be removed by precipitation can be treated, and the effluent water quality is good;

(3) The dose required is less than that of precipitation;

(4) Can recycle useful substances.

Classification of air flotation techniques

There are many kinds of air flotation separation methods, according to the way of producing fine bubbles can be divided into: electrolysis gas flotation method, dispersed air gas flotation method, dissolved air flotation method.

Dispersed air air flotation using microporous diffusion plate or microporous tube directly into the air float pool compressed air or using hydraulic ejector, high-speed impeller and other water inflation, can

It can be divided into diffused plate air flotation, jet air flotation and impeller air flotation.

Dissolved air floatation makes the air dissolve in water under a certain pressure and reach saturation state, and then the pressure of the wastewater suddenly decreases, then the air dissolved in water is released from the water in the form of micro-bubbles to carry out air floatation wastewater treatment, which can be divided into pressure dissolved air floatation and vacuum dissolved air floatation; Partial return flow pressure dissolved air flotation is the most commonly used process in water treatment, and it can be used as a new technology to replace precipitation in some aspects.

Nevertheless, the design and best operation of the air float plant still rely on pilot tests and experience. Therefore, the mechanism of air flotation, air flotation equipment and process combination need to be further studied. The electrolysis gas float method is to electrolysis the waste water, the cathode produces a large number of hydrogen bubbles, which acts as a flotation agent. The suspended particles in the waste water adhere to the hydrogen bubbles and float up with them to achieve the purpose of purifying the waste water.

Application of air flotation in wastewater treatment

As a fast and efficient solid-liquid separation technology, gas flotation is suitable for both water supply and water purification, and for the treatment of many kinds of wastewater. It can not only replace precipitation and clarification in water treatment, but also be used as pretreatment and sludge concentration for advanced wastewater treatment. For the treatment of raw water which is difficult to obtain good purification effect by precipitation method, the effect of gas flotation method is better. Mainly applicable to the following:

1. Treatment of oily wastewater in petrochemical and machinery manufacturing industries

2. Treatment of papermaking wastewater, recovery of pulp fibers and fillers

3. Treatment of electroplating wastewater and wastewater containing heavy metal ions

4. Treatment of printing and dyeing wastewater and washing wastewater

5. Treatment of tannery wastewater, municipal sewage and eutrophication precursors