In the big family of sewage treatment, hydrolysis and acidification tanks are quite important members. Today, let's talk about hydrolysis acidification tanks in detail, from their classification, principles, removal efficiency, and precautions during operation, and explain them to everyone in one go.
Classification of hydrolysis acidification tanks
There are several ways to classify hydrolysis acidification tanks, let's first talk about the direction of water flow. There is an upward flow hydrolysis acidification tank, where the water flow rises from the bottom as if it is striving upwards. Wastewater enters from the bottom of the pool and, as it rises, comes into full contact with the microorganisms in the pool, leading to hydrolysis and acidification reactions. There is also a downward flow hydrolysis acidification tank, which is opposite to the upward flow tank. The water flows from the top to the bottom of the tank, completing the reaction all the way. In addition, there is a horizontal hydrolysis acidification tank, where sewage flows horizontally through the tank, like slowly advancing in a large channel while undergoing hydrolysis acidification.
From a structural perspective, it can be divided into integrated hydrolysis acidification tanks and split hydrolysis acidification tanks. Integrated is to integrate the hydrolysis acidification and subsequent treatment parts into one pool, with a compact structure and small footprint, like a multifunctional small box that can hold anything. As for the split type, it means that the hydrolysis and acidification part is separated from other treatment units, each independent. The advantage is that each part can be designed and adjusted separately according to needs, making it more flexible, just like separating rooms with different functions and using whichever one you want.
Principle of hydrolysis acidification tank
To understand the principle of a clear water acidification tank, we need to first know the power of microorganisms. There is a special group of microorganisms living in the hydrolysis and acidification tank, who are great contributors to the treatment of sewage. After the sewage flows into the pool, these microorganisms begin to work.
The first step is the hydrolysis stage. The complex macromolecular organic compounds in sewage, such as proteins, polysaccharides, and fats, are like large "food clusters" that microorganisms cannot directly eat. At this point, hydrolytic bacteria take action first, secreting special enzymes to cut these large organic molecules into small pieces, just like cutting a big cake into small pieces for easy subsequent processing. For example, proteins are hydrolyzed into amino acids, polysaccharides are hydrolyzed into monosaccharides, and fats are hydrolyzed into fatty acids and glycerol.
Next is the acidification stage. The small molecule organic matter that has been hydrolyzed is further transformed under the action of acidifying bacteria. Acidizing bacteria convert these small molecules into simpler substances, mainly volatile fatty acids such as acetic acid and propionic acid, as well as alcohols, carbon dioxide, hydrogen, and so on. This process is like processing a pre cut cake into more easily absorbable nutrients. And at this stage, the pH value of the sewage will also change, becoming more acidic. Through the steps of hydrolysis and acidification, the difficult to treat large molecular organic compounds in the sewage are transformed into small molecular substances that are easily utilized by subsequent treatment units, laying a good foundation for the entire sewage treatment process.
The removal effect of hydrolysis acidification tank
The removal effect of hydrolysis acidification tank in sewage treatment is quite good, with several aspects of performance.
First, let's talk about the removal of organic matter. In general, hydrolysis acidification tanks can remove a portion of organic matter from wastewater. Although it does not have the same high removal rate as the later aerobic treatment unit, it can convert large organic molecules into small molecules, improving the biodegradability of wastewater. For example, sewage with poor biodegradability may have a ratio of BOD5 (biochemical oxygen demand) to COD (chemical oxygen demand) of only about 0.2. After treatment in a hydrolysis and acidification tank, this ratio can be increased to 0.3 or even higher, allowing for more efficient aerobic treatment and overall better removal of organic matter.
Let's talk about the removal of suspended solids. The microorganisms and some fillers in the hydrolysis acidification tank are like small filters. When sewage flows through, suspended solids will be intercepted and adsorbed. Some large suspended particles will settle to the bottom of the pool and be removed with the sludge discharge. Generally speaking, the removal rate of suspended solids in hydrolysis acidification tanks can reach about 30% -50%, which greatly reduces the burden on subsequent treatment units and prevents suspended solids from blocking subsequent equipment and pipelines.
In addition, hydrolysis and acidification tanks also have a certain conversion effect on nutrients such as nitrogen and phosphorus in wastewater. Although it cannot completely remove nitrogen and phosphorus like specialized denitrification and phosphorus removal processes, it can convert some organic nitrogen into ammonia nitrogen, creating conditions for subsequent nitrification denitrification and nitrogen removal. For phosphorus, its form can also be altered through microbial adsorption and other processes, which is beneficial for further processing.
Precautions for the operation of hydrolysis acidification tank
There are many things to pay attention to in order to operate the hydrolysis acidification tank well.
In terms of temperature, microorganisms are very sensitive to temperature. The suitable temperature for hydrolysis acidification tank is between 15-35 ℃. If the temperature is too low, microorganisms will be frozen, their activity will decrease, reaction speed will slow down, and the treatment effect will be greatly reduced. For example, in winter, if insulation measures are not taken properly, the processing efficiency of the pool may decrease by half. On the contrary, too high a temperature is not acceptable. If it exceeds 40 ℃, microorganisms may not be able to tolerate it and may even die. So during operation, it is necessary to always pay attention to the temperature, and if necessary, add a "warm coat" or "cooling device" to the pool.
The pH value is also crucial. The appropriate pH value for the hydrolysis and acidification stage is generally between 6.5-7.5. If the pH value is too low and the acidity is too strong, it will inhibit the growth of microorganisms; A high pH value and strong alkalinity are also unfavorable for microbial work. During operation, it is necessary to regularly check the pH value, and if it deviates from this range, it must be adjusted as soon as possible. It can be adjusted by adding acid or alkali, but be careful not to over adjust the amount.
There is also hydraulic retention time, which refers to the time that wastewater stays in the hydrolysis and acidification tank. This time cannot be too short. If it is too short, the sewage and microorganisms will not have enough time to fully react, and the treatment effect will be poor; But it cannot be too long, as it will waste resources and may also lead to overgrowth of microorganisms, resulting in some adverse effects. Generally speaking, it is more appropriate to control the hydraulic retention time between 4-12 hours, which should be adjusted according to the water quality and quantity of the wastewater. The management of sludge cannot be ignored either. The bottom of the hydrolysis acidification tank will accumulate sludge, which is full of active microorganisms and is a treasure for treating sewage. Regularly discharge the mud, but not too much, otherwise the number of microorganisms will be insufficient, which will affect the treatment effect. At the same time, attention should be paid to the return of sludge, and a portion of activated sludge should be returned to the front of the tank to improve reaction efficiency, just like adding fuel to microorganisms and making them more motivated.
In addition, it is necessary to prevent toxic and harmful substances from entering the hydrolysis and acidification tank. Some heavy metals and toxic chemicals, even in small amounts, can cause fatal harm to microorganisms. So before the sewage enters the hydrolysis and acidification tank, strict testing should be carried out to ensure that there are no "dangerous molecules" mixed in. In short, although the hydrolysis acidification tank may not seem complicated, every detail needs to be taken into account to ensure its stable and efficient operation. Only by implementing these operational precautions can the hydrolysis acidification tank play its maximum role in sewage treatment and help us turn sewage into clean water resources.
