Today, let's talk about a topic that is quite professional but closely related to practical operation - the influence of suspended solids on the formation of dissolved air water in dissolved air flotation. Some people may get confused when they hear words like "suspended solids" and "dissolved air flotation", thinking they are too academic. In fact, let's put it in a down-to-earth way and talk about it slowly. You will definitely understand.
Let me briefly explain what dissolved air flotation is. Simply put, it is a method of water treatment, with the core idea of dissolving some gases in the water to form dissolved gas water, and then putting the dissolved gas water into the wastewater to be treated. At this point, the gas in the dissolved water will escape and turn into tiny bubbles. These bubbles particularly like to "stick" to impurities in the water, that is, suspended solids, and float to the surface with them, so that the water can be cleaned up.
So the question is, will suspended solids in the water in turn affect the formation of dissolved water? The answer is affirmative. We can look at it from several aspects.
Firstly, the amount of suspended solids will have an impact. If there are too many suspended solids in the water, like too many rice grains in a pot of porridge, the water will become turbid and viscous. At this point, it is not so easy for gas to dissolve into water. Think about it, gas molecules need to find a place to settle down in water, but suspended solids are blocking their way everywhere, so the amount they can dissolve smoothly naturally decreases. For example, if you want to stuff some small items into a box filled with things, it will definitely be much harder than an empty box. So, if the concentration of suspended solids is too high, it will cause a decrease in the amount of dissolved air in the dissolved water, resulting in insufficient subsequent bubbles and a decrease in the treatment effect.
Let's talk about the size and shape of suspended solids. Some suspended particles are large, while others are small; Some are regular circles, while others have strange shapes. Generally speaking, larger suspended particles are more prone to "rampage" in water, as they can interfere with the dissolution process of gas molecules. Just like throwing a big stone on a calm water surface, it will stir up waves and break the original balance. And those irregularly shaped suspended particles may have bumpy surfaces, which can easily adsorb some gas bubbles onto themselves. This may seem helpful, but it's not. Because these bubbles were "snatched away" by suspended solids in advance, they did not truly dissolve into the water to form dissolved gas water, which is equivalent to wasting some gas and instead affecting the quality of dissolved gas water.
The properties of suspended solids are also crucial. Some suspended solids are hydrophilic, meaning they are particularly fond of water and always carry a layer of water molecules on their surface. This layer of water molecules acts as a barrier, preventing gas molecules from approaching and dissolving into the water. Just like a person wearing a raincoat, it's difficult for rainwater to wet their clothes. Some suspended solids are hydrophobic and do not like water very much. They are more likely to combine with gases, but this may also cause the gas to be "pulled" by these suspended solids before dissolution, forming small bubbles instead of uniformly dissolving in water. This makes the dissolved water unstable and the bubble size uneven, affecting the subsequent treatment effect.
In addition, the charged state of suspended solids can also cause disturbances. Many suspended solids in water are charged, some positively and some negatively. And gas molecules may also carry weak charges in water. If the charges of the two are opposite, they will attract each other, and gas molecules may be "sucked" by suspended matter and gather around them instead of uniformly dissolving in water. In this way, the distribution of dissolved gas and water is uneven, with some areas having more gas and others having less. When treating sewage, there will be "dead corners", and some suspended solids cannot be "favored" by bubbles and cannot float up.
Another easily overlooked point is that suspended solids may accumulate in water. They sometimes stick together to form larger flocs. These flocs have a large volume and will occupy more space, making the fluidity of water worse. When dissolved gas and water form, it is necessary for the water to flow smoothly and come into full contact with the gas. If water flows slowly due to the accumulation of suspended solids, the contact efficiency between gas and water will decrease, and the gas dissolution effect will naturally be poor. Moreover, these large flocs may also block the pores of some equipment, such as the dissolved air release device, making it difficult for the dissolved water to be released smoothly, which is even more troublesome.
For example, in the treatment of wastewater from a paper mill, there are many suspended particles such as pulp fibers. These fibers are thin and long, with a high concentration, and many of them are hydrophilic. At this point, it is particularly difficult to allow the gas to dissolve smoothly and form dissolved water. The dissolved air cannot be removed, and bubbles are easily entangled by fibers, resulting in a significant decrease in the processing efficiency of the dissolved air flotation equipment, and the pulp fibers in the water cannot be completely removed.
What should we do when encountering these problems? There are actually some ways. For example, before treating wastewater, pre-treatment should be carried out to minimize the concentration of suspended solids or change their properties. You can add some chemicals to allow small suspended solids to aggregate into larger ones, making it easier to filter out some of them later, or to make hydrophilic suspended solids hydrophobic, reducing obstacles to gas dissolution. In addition, the parameters of the gas dissolution equipment can also be adjusted, such as increasing pressure and extending the gas dissolution time, so that the gas has more opportunities to dissolve into the water, offsetting some of the negative effects caused by suspended solids.
Overall, suspended solids have a significant impact on the formation of dissolved water in air flotation. From concentration, size, shape, properties, charge, to aggregation, every aspect may add some "small troubles" to the formation of dissolved water. So in practical operation, it is necessary to carefully consider the situation of suspended solids in the water and take corresponding measures in order to form more and better dissolved air water, so that the dissolved air flotation equipment can truly function and treat the water cleanly.
