dissolved air flotation is divided into two types: vacuum dissolved air flotation and pressurized dissolved air flotation, according to the different pressures at which the bubbles are precipitated. Dissolved air flotation is mainly used for water purification, domestic sewage and industrial wastewater treatment. It can replace precipitation and clarification in feed water or wastewater treatment; it can also be used for pretreatment and concentration treatment of advanced wastewater treatment.

air flotation machine equipment has been very popular in the field of sewage treatment, so what are the key points of the method of dissolved air flotation machine?

The key point of the design scheme of the dissolved air flotation machine equipment is the air flotation method. The air flotation method is based on the design scheme of standard air pressure. The concentration value of suspended solids is designed and manufactured by taking into account the rate of separation of the chamber. This requirement is required. It will be better to work together to solve the actual effect, which is actually described in detail below.

(1) It is necessary to fully study and discuss the water quality of the water to be treated, and analyze the rationality and applicability of the air flotation process;

(2) In the case of conditions, the necessary air flotation small-scale test or model test should be carried out for the wastewater to be treated. And select the appropriate dissolved gas pressure and reflux ratio (referring to the ratio of dissolved gas water volume to water volume to be treated) according to the test results. Usually, the dissolved gas pressure is 0.2~0.4MPa, and the reflux ratio is between 5% and 100%. The determination of the reflux ratio needs to be related to the concentration of suspended solids. The higher the concentration is, the larger the reflux ratio is, and the smaller the concentration is, the smaller the reflux ratio is;

(3) Determine the reaction form and reaction time according to the type of coagulant, dosage, flocculation time, reaction degree, etc. selected during the test. Generally, the precipitation reaction time is short, and 2 to 30 minutes is appropriate;

(4) To determine the pool type of the air flotation tank, it should be comprehensively considered according to the requirements of the water quality to be treated, the connection between the water purification process and the pre- and post-treatment structures, the coordination of the surrounding terrain and structures, the difficulty of construction and the cost of construction. The reaction tank should be built together with the flotation tank. In order to avoid breaking the flocs, attention should be paid to the connection form of the structures. The flow velocity entering the contact chamber of the flotation tank should be controlled within 0.1m/s;

(5) The contact chamber must provide good contact conditions for air bubbles and flocs, and the width should consider the requirements of installation and maintenance. The rising velocity of the water flow is generally 10~20mm/s: the residence time of the water flow in the room should not be less than 60 seconds;

(6) The dissolved gas releaser in the contact room should be selected according to the following table according to the determined return flow, dissolved gas pressure and the scope of action of various types of releasers;

(7) The air flotation separation chamber should be determined according to the difficulty of floating and separation with air flocs and the treatment requirements of water quality. Select the flow rate of the water flow (downward), generally 1.5~3.0mm/s, that is, the surface load rate of the separation chamber is 5.4~10.8m3/(m2.h);

(8) The effective water depth of the air flotation tank is generally 2.0~2.5m, and the residence time of the water flow in the tank is generally 10~20min;

(9) There are no strict requirements for the length-width ratio of the air flotation tank; generally, the width of a single cell should not exceed 10m, and the length of the tank should not exceed 15m;

(10) The slag discharge of the air flotation tank is generally removed regularly by a slag scraper. The slag collecting tank can be set at one end or both ends of the pool. The driving speed of the slag scraper should be controlled within 5m/min;

(11) The water collection in the air flotation tank should be uniform. Generally, perforated water collection pipes are used, and the maximum flow rate of the water collection pipes should be controlled at about 0.5m/s;

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