When it comes to dissolved air flotation, friends who are familiar with dry wastewater treatment or industrial wastewater treatment may be more familiar with it. Simply put, it means "plugging" many small bubbles into the water, allowing these bubbles to float to the surface with the dirty things in the water, making it easier to clean. Among them, the gas tank is a core role, and its pressure stability is directly related to the amount and size of bubbles, affecting the treatment effect. But sometimes, the pressure of this gas tank inexplicably increases, leaving people confused. Today, let's talk in plain language about why the pressure in the gas tank remains high and what reasons may be hidden behind it.
Let me briefly explain how the gas tank works
Before discussing high pressure, it is necessary to understand the basic operation of the gas tank. Its function, in other words, is to allow air to "dissolve" into water under high pressure. Specifically, it involves injecting pressurized water and air into a tank. Under high pressure, the air acts like a sponge pressed into the water, greatly increasing its solubility. When the water that has dissolved a lot of air suddenly flows into the low-pressure air flotation tank, as soon as the pressure drops, the air will "run" out of the water and become countless tiny bubbles, which can then float up with impurities.
Under normal circumstances, the pressure of the gas tank is stable within a range, such as the common 0.2~0.4 megapascals. If the pressure suddenly rises beyond the normal range, it means there is a "stuck shell" and we need to quickly find the cause.
Is the pressure in the gas tank high? Maybe the exit is blocked
The most common reason often comes from the "outlet" of the dissolved gas tank. Do you think that after the water and air in the dissolved air tank are mixed, they have to be sent to the air flotation tank through pipelines? If this' way out 'is blocked and the contents of the can cannot be emptied, the pressure will only increase.
-There are lumps in the pipeline: impurities such as colloids, suspended solids, and even minerals such as calcium and magnesium ions are inevitable in the water. Over time, these things may slowly accumulate on the inner wall of the outlet pipe, just like how water pipes at home will scale over time. The more blocked the pipeline, the finer it becomes, and the slower the water flow, causing the pressure in the tank to naturally increase. Especially in winter, if the water temperature is low, certain substances in the water are more likely to crystallize and clog faster.
-The valve is not fully opened due to laziness: a control valve is usually installed at the outlet of the dissolved gas tank to regulate the flow rate. Sometimes it may be an operational error where the valve is not fully opened; It may also be a problem with the valve itself, such as the valve core getting stuck and appearing to be open, but in fact it is not fully opened inside. It's like you want to pour out the water from a bottle, but only unscrew half of the cap. The water will flow slowly and the pressure inside the bottle will increase.
-Subsequent equipment "lags behind": The dissolved air water will eventually enter the air flotation tank. If the liquid level in the air flotation tank is too high or the inlet pipe of the tank is blocked, it will cause an increase in resistance when the water in the dissolved air tank is discharged. Just like pouring water into a nearly full cup, it's difficult to pour water into it and instead increases the pressure in the kettle. The principle is the same.
It could also be 'too much air intake' or 'too much air in the tank'
The pressure inside the gas tank is not only related to water, but also to the amount of air. If too much air enters, exceeding the amount required for a normal reaction, the air pressure in the tank will remain high.
-The air compressor works too hard: It is usually the air compressor that supplies air to the dissolved air tank. If the pressure of the air compressor is set too high or the valve controlling the intake is broken and not tightly closed, it will cause a large amount of air to rush into the tank. There is too much air in the can, and the pressure naturally cannot be suppressed. It's like inflating a balloon. If you inflate too much, the balloon will become fuller and the pressure will increase.
-Insufficient flow rate of dissolved air and water: Under normal circumstances, water and air enter the dissolved air tank in a certain proportion. If the amount of water entering the dissolved gas tank suddenly decreases (such as a problem with the previous water pump or a clogged inlet pipe), but the amount of air entering does not change, it is equivalent to "more air and less water". If there is not enough water to dissolve the air, it will accumulate in the tank, leading to an increase in pressure. Just like a cup of water can only dissolve so much sugar, if too much sugar is added, it will sink to the bottom of the cup. The "sugar" here is the excess air, which will increase the pressure inside the can.
Don't forget, the jar may contain dirt and grime
If the gas tank is used for a long time, there may also be internal problems. After all, it comes into contact with sewage and air every day. Over time, the tank walls or internal components may accumulate scale, mud, and even breed some microorganisms, which can affect the normal operation of the tank.
-Scaling or mud accumulation in the tank: If the treated water contains many impurities, such as a large amount of calcium and magnesium ions, or a lot of suspended solids, these things may slowly deposit on the inner wall and baffle of the dissolved gas tank (some dissolved gas tanks have baffles to help mix). Over time, the effective space inside the tank becomes smaller, equivalent to the "room" becoming squeezed. With the same amount of water and air entering, the pressure will be higher than usual.
-Internal component damage: Some gas tanks have water distributors and air distributors inside, which are used to mix water and gas more evenly. If these parts are damaged, such as a clogged or cracked water distributor, the mixture of water and gas will become uneven, and "air masses" may accumulate in local areas, resulting in uneven pressure distribution inside the tank and an overall increase in pressure. Just like a showerhead at home with a few blocked holes, the remaining holes will release water more quickly and the water pressure will increase. The "water pressure" here is similar to the pressure of a dissolved gas tank.
Improper operation or instrument "lying" may also lead to mistakes
Sometimes high pressure is not really a big problem with the equipment, but rather a result of our carelessness during operation or inaccurate pressure monitoring instruments, leading people to mistakenly believe that the pressure is high.
-Incorrect adjustment of operating parameters: for example, at the beginning of operation, the pressure was not slowly increased according to the regulations, but was suddenly set too high; Or when adjusting the operating conditions, the intake and intake volumes may not be adjusted synchronously, resulting in an imbalance in the ratio between the two. These minor operational errors may temporarily increase the pressure.
-Pressure gauge "scam": The pressure gauge is the key to monitoring pressure. If it is broken, such as the pointer getting stuck or the sensor malfunctioning, it may display a higher pressure than the actual value. At this point, the pressure may seem high, but it is actually normal inside the tank. Although this situation is not really high pressure, it can still make people mistakenly think that there is a problem and delay things. So when encountering high pressure, it's best to check the accuracy of the pressure gauge first, such as trying to replace it with a new one.
To summarize, how to troubleshoot when encountering high stress?
In fact, when the pressure of the dissolved gas tank is high, it is essentially an imbalance between "in" and "out". Either the way out is blocked, or there is too much gas or water coming in, or the tank itself has "become smaller". If you really encounter this situation, you can follow these steps to troubleshoot:
1. First, check if the outlet pipeline and valves are blocked or not fully opened;
2. Check the intake and water intake to see if there is a proportional imbalance and if there is any problem with the air compressor;
3. Open the drain outlet at the bottom of the tank and release water to check if there is a large amount of sludge or impurities discharged, and determine if there is mud or scaling inside the tank;
4. Check the accuracy of the pressure gauge and troubleshoot any instrument malfunctions;
If there are no issues with the above, then check if the internal components are damaged.
In short, high pressure in the dissolved gas tank is not a small problem, as it can affect the air flotation effect and make it difficult to remove impurities from the water; In severe cases, it may damage the equipment and even pose a safety hazard. Pay more attention to changes in stress and regularly maintain and clean it in order to ensure its safe and stable operation. After all, this thing is a "good helper" for sewage treatment, so we have to take good care of it, right?
