Key Precautions for Operating An Air Flotation Machine

As a core solid-liquid separation device in modern water treatment, the air flotation machine is widely used in industrial wastewater treatment across petrochemical, papermaking, printing and dyeing, slaughtering, and food processing industries. However, no matter how advanced the equipment, scientific operation and careful maintenance are essential to truly achieve efficient treatment performance. This article systematically summarizes the key precautions for operating an air flotation machine from four aspects: operational specifications, maintenance, safety and emergency response, and troubleshooting.

1. Pre-startup Inspection and Preparation

Before each startup, operators must complete three basic checks:

- Verify that all valves are in normal working condition.

- Check that the water level in the dissolved air tank is normal.

- Ensure all electrical equipment is functioning properly.

Specifically, confirm that the direction of rotation and oil levels of the feed pump, dissolved air pump, and air compressor are normal. Inspect the scraper drive system, adjust the gearbox oil level, check scraper flexibility and travel speed, and examine pressure gauges and valve seals. Prepare coagulants according to the required formulation and check the dosing metering device.

For new installations or restarting after prolonged shutdown, flush the flotation tank with clean water and check for leaks. The dissolved air pipeline should be flushed alternately with high-pressure water and compressed air several times to ensure no particulate debris remains before installing the dissolved air releaser.

2. Key Points for Startup and Operation

Follow the “air first, then water” startup sequence:

- Start the air compressor, open the inlet valve, and adjust the inlet pressure to 0.2 MPa.

- Start the dissolved air pump to feed water into the dissolved air tank, adjusting the water level to about one-third of the liquid level gauge. At this point, the tank pressure should reach 0.4 MPa.

- Only after the dissolved air pump has run continuously for 3 to 10 minutes can the flotation feed pump be started.

During operation:

- The dissolved air tank pressure should be maintained between 0.35 and 0.5 MPa. Under normal operation, do not let the tank pressure exceed 3.5–4.0 kg/cm² to avoid overpressure hazards.

- The water level in the dissolved air tank should be kept between 0.6 and 1.0 meters – not so high as to submerge the packing and reduce dissolution efficiency, nor so low that the effluent contains many undissolved air bubbles.

- Never run the dissolved air pump dry. During normal operation, the inlet vacuum pressure should be between 0.01 and 0.02 MPa (negative pressure), and the outlet pressure between 0.4 and 0.5 MPa.

When the scum layer accumulates to 5–8 cm, start the scraper. Check that scraping and discharge are normal and that effluent quality is not adversely affected.

3. Daily Maintenance Guidelines

The efficient and stable operation of an air flotation machine relies on frequent inspection, regular cleaning, and stable operating conditions. Core maintenance points include:

Daily inspection:

Observe the water level in the dissolved air tank through the sight glass to ensure it is within design limits. Check the pump and air compressor for ice formation, abnormal noise, or overheating. Inspect the flotation tank surface – if the scum layer in the contact zone is uneven or locally turbulent, it may indicate a blocked or detached releaser, requiring repair or replacement.

Periodic maintenance:

Lubricate the pump, air compressor, and scraper regularly. Generally, add oil to the air compressor every two months and replace the oil every six months. Grease bearings, chains, and gears every 10 days, and perform a full inspection every three months. Clean the flotation tank as needed depending on sediment accumulation, and check the sealing of pipes and valves.

Winter care:

When low water temperatures affect coagulation efficiency, in addition to increasing the chemical dosage, you can increase the recycle flow or raise the dissolved air pressure to generate more microbubbles and improve bubble-floc adhesion, compensating for the reduced rise rate of bubble-attached flocs due to higher water viscosity. Drain all water before shutdown to prevent freezing and pipe blockage.

4. Safety Operation and Emergency Response

Safety is the bottom line of air flotation operation. Operators must follow these safety rules:

Personal protection:

Wear protective gloves and goggles to avoid skin or respiratory contact with chemicals. Store wastewater and chemicals in separate areas with clear warning signs.

Equipment safety:

Do not touch rotating parts. Never open inspection ports while the equipment is running to avoid high-pressure water or gas jets. Shut down immediately if the dissolved air tank pressure is abnormal. Regularly check the insulation of electrical components to prevent short circuits in humid environments. Flush pipelines after shutdown to prevent chemical residue crystallization and blockage.

Emergency response:

In case of a sudden power outage, immediately close the inlet valve, drain the unit, and have an emergency power supply ready. If the dissolved air tank pressure is abnormal, shut down and troubleshoot first – never remove the inspection port under pressure.

5. Quick Troubleshooting of Common Problems

If flotation performance is poor, first check the dissolved air system: whether the dissolved air pump is faulty, the tank pressure is stable, and the releasers are clogged. If the scum surface in the contact zone is uneven or large bubbles appear locally, it indicates a blocked releaser or poor bubble-floc adhesion – adjust the coagulation system parameters.

If effluent quality is substandard, check the chemical dosage, recycle ratio, and scraping frequency. For normal operation, maintain an operating log and dynamically adjust chemical dosage, feed flow, and dissolved air flow based on effluent quality to ensure consistent compliance.

Conclusion

The efficient operation of an air flotation machine depends on standardized procedures, scientific maintenance, and strict safety awareness. Systematic implementation of operational guidelines can effectively extend equipment life, reduce operating costs, and ensure stable effluent quality. We hope the precautions summarized here serve as a practical reference for environmental protection professionals and contribute to the long-term stable operation of air flotation equipment.