Overview
The high-efficiency horizontal flow air flotation machine, as a core solid-liquid separation device in the modern wastewater treatment field, achieves highly efficient removal of suspended solids, colloids, and oil pollutants in wastewater through the collaborative innovation of dissolved air flotation (DAF) technology and horizontal flow field design. Its technological core lies in using microbubbles (with a diameter of 10 - 30μm) released from high-pressure dissolved air water to form gas-solid/liquid composite flocs with pollutants, which quickly float to the water surface under the action of buoyancy and then are removed in a centralized manner through the slag scraping system. Compared with the traditional sedimentation method, this equipment increases the solid-liquid separation efficiency by 3 - 5 times and reduces the floor area by 50%. It is especially suitable for the pretreatment and advanced treatment of oily wastewater, emulsions, and wastewater with high concentrations of suspended solids, and is a key device for water purification in municipal sewage, food processing, petrochemical, and other industries.
Core Working Principle and Structural Innovation
I. Analysis of Dissolved Air Flotation Technology
1. Dissolved Air System: High-pressure pumps (with a pressure of 0.3 - 0.5MPa) are used to dissolve air in water to form supersaturated dissolved air water. After the pressure is suddenly reduced by the release device, microbubbles are uniformly precipitated. The bubble density can reach 10⁹ per liter, ensuring sufficient contact with pollutants.
2. Flocculation Reaction Zone: Wastewater is mixed with coagulants (such as PAC and PAM) at the front end to form flocs with a particle size of 50 - 200μm, providing a carrier for bubble adhesion. The horizontal flow design enables the residence time of the water flow in the reaction zone to be controlled within 15 - 20 minutes to ensure the flocculation effect.
3. Separation Zone Flow Field Optimization: A horizontal plug-flow flow field is adopted, and the velocity gradient of the water flow gradually decreases from 0.1m/s at the inlet to 0.01m/s at the outlet. Combined with the inclined tube components (with an inclination angle of 60°), water flow disturbances are reduced, the thickness of the scum layer is stabilized at 30 - 50cm, and the separation efficiency is improved.
II. Structural Design Advantages
1. Anti-Corrosion Treatment of All-Steel Structure: The main body is made of Q235B carbon steel, and the inner and outer walls are subjected to epoxy coal tar anti-corrosion treatment (with a dry film thickness of ≥300μm). It can withstand the corrosive environment with a wastewater pH value ranging from 3 to 11, and has a service life of more than 10 years.
2. Intelligent Slag Scraping System: The chain-type slag scraper adopts frequency conversion control (with a linear speed of 0.5 - 1.0m/min) and can automatically adjust the slag scraping frequency according to the thickness of the scum, avoiding the problem of scum falling back caused by traditional timed slag scraping.
3. Intelligent Adjustment of Dissolved Air Water Recirculation Ratio: Through the PLC system, the SS concentration of the influent water is monitored in real time, and the dissolved air water recirculation ratio (usually 15% - 30%) is automatically adjusted to reduce energy consumption while ensuring the treatment effect.
Analysis of Typical Application Scenarios
1. Petrochemical Wastewater Treatment
After the oily wastewater (with an oil content of 500 - 1000mg/L) from a certain refinery was treated by the high-efficiency horizontal flow air flotation machine, the oil content in the effluent water was reduced to below 10mg/L. The equipment adopted the combined process of "dissolved air flotation + inclined tube separation" and was combined with the pretreatment of coalescing cartridges, so that the oil content in the scum reached 30%, facilitating subsequent resource utilization. Compared with the traditional oil separation tank, this scheme shortened the treatment cycle from 4 hours to 1.5 hours, and the annual value of recovered waste oil exceeded 500,000 yuan.
2. Food Processing Wastewater Treatment
In meat processing wastewater, the high-efficiency horizontal flow air flotation machine can effectively remove blood stains, grease, and proteinaceous suspended solids. A case study of a slaughterhouse showed that the equipment achieved a COD removal rate of 60% - 70% and an SS removal rate of over 90%, creating conditions for subsequent biochemical treatment. The horizontal flow design enables the equipment to maintain stable operation under high loads (with a hydraulic load of 2 - 3m³/(㎡·h)), adapting to the intermittent drainage characteristics of the slaughter industry.
3. Advanced Treatment of Municipal Sewage
A certain urban sewage treatment plant added a high-efficiency horizontal flow air flotation machine as an advanced treatment unit after the secondary biochemical treatment. The equipment achieved a TP removal rate of 80%, and the turbidity was reduced to below 1NTU, meeting the first-class A standard of the "Discharge Standard of Pollutants for Municipal Wastewater Treatment Plants". Compared with traditional sand filtration, the backwashing water consumption of the air flotation process was reduced by 70%, and there was no cost for filter material replacement, saving 300,000 yuan in annual operation and maintenance costs.
4. Pretreatment of Electroplating Wastewater
For electroplating wastewater containing heavy metal ions, the high-efficiency horizontal flow air flotation machine uses the "coagulation flotation + heavy metal scavenger" process to make heavy metal ions such as Cu²⁺ and Ni²⁺ form hydroxide flocs, which are removed by floating with bubbles. In a case study of an electroplating park, the total removal rate of heavy metals by the equipment was over 95%, and the concentration of heavy metals in the effluent water was lower than 0.5mg/L, providing a guarantee for subsequent membrane treatment.
Technical Advantages and Industry Value
1. Dual Breakthroughs in Efficiency and Cost
- High treatment load: The unit area treatment capacity reaches 4 - 6m³/(㎡·h), which is three times that of the traditional sedimentation tank, significantly reducing the floor area;
- Low energy consumption: The power density of the dissolved air system is ≤0.5kW·h/m³. Combined with frequency conversion control, it saves 20% energy compared to traditional air flotation equipment.
2. Adaptability and Reliability
- Strong adaptability to water quality fluctuations: It can handle wastewater with an SS concentration ranging from 50 to 5000mg/L. By adjusting the dosage of coagulants and dissolved air parameters, a stable removal effect can be maintained;
- High degree of automation: Integrated with online water quality monitoring (pH, turbidity, COD) and a fault warning system, it realizes unattended operation and reduces labor costs by 50%.
3. Environmental Protection and Resource Recovery Potential
- Low moisture content of scum: The slag scraping system can control the moisture content of the scum within 90% - 95%, which is 5% - 10% lower than that of traditional air flotation, reducing the amount of subsequent sludge treatment;
- Convenient resource recovery: Oily scum can be directly centrifugally dehydrated, and the waste oil recovery rate reaches 80%, realizing a circular economy model of "treating waste with waste".
Selection and Maintenance Guidelines
I. Key Selection Factors
- Treatment Water Volume Matching: Configure at 1.2 times the maximum design flow. For example, a wastewater treatment station with a flow rate of 1000m³/d should choose equipment with a treatment capacity of 50m³/h, reserving margins for backwashing and load fluctuations;
- Analysis of Pollutant Characteristics: For oily wastewater, priority should be given to models with high dissolved air efficiency (such as a combination of cavitation air flotation and dissolved air flotation). For wastewater with high SS content, focus on the volume design of the flocculation reaction zone;
- Material and Anti-Corrosion Requirements: For chemical wastewater, choose 316L stainless steel components. For municipal sewage, carbon steel + anti-corrosion coating can be selected. In coastal areas, enhanced anti-salt spray treatment is required.
II. Maintenance Optimization Strategies
1. Daily Operation Management:
- Regularly check the pressure of the dissolved air tank (keep it at 0.3 - 0.5MPa) and the blockage of the release device. Use high-pressure water (0.8MPa) to flush the release device weekly;
- Monitor the operating status of the slag scraper to avoid uneven slag scraping caused by loose chains. It is recommended to add grease quarterly.
2. In-depth Maintenance Points:
- Clean the inclined tube components once every six months to prevent the attachment of algae and sludge from affecting the separation effect. Soak and disinfect them with a 10% sodium hypochlorite solution;
- Conduct an efficiency test on the dissolved air pump annually. When the flow attenuation exceeds 15%, replace the impeller and seals.
Industry Development Trends
With the promotion of the "dual carbon" goal and the upgrading of environmental protection standards, the high-efficiency horizontal flow air flotation machine is developing in the directions of intelligence, low carbon, and resource utilization:
- Intelligent Control Technology: Introduce AI algorithms to optimize the dosage of coagulants, dissolved air pressure, and other parameters in real time according to the influent water quality, reducing the consumption of chemicals by 15% - 20%;
- Low-Carbon Process Innovation: Develop a solar-driven dissolved air system to achieve "zero energy consumption" operation in remote areas. Combined with anaerobic digestion technology, convert the scum into biogas energy;
- Modular Integrated Design: Integrate with processes such as MBR and ozone oxidation to form an "air flotation - biochemical - advanced treatment" integrated equipment, which is suitable for decentralized sewage treatment scenarios.
Conclusion
The high-efficiency horizontal flow air flotation machine has become the mainstream choice in the field of industrial wastewater treatment due to its technical characteristics of "rapid separation and energy saving". From petrochemical to municipal environmental protection, its innovative dissolved air flotation technology and horizontal flow structure have solved the pain points of low efficiency and large floor area of traditional solid-liquid separation equipment. In the future, with the deep integration of intelligent control and green processes, this equipment will play a more crucial role in water environment governance and resource recycling, promoting the continuous progress of the water treatment industry towards high efficiency and low carbon.
