Experience With Tears!
We have all played the game of blowing bubbles, the bubbles are very magical and very fun, but there is a type of people who can't avoid bubbles, and even removing bubbles is part of their job, and this type of people is water treatment Operation and Maintenance Engineer.
Foaming in the aeration tank is a common problem in water treatment operation and maintenance. Once it occurs, it may cause some adverse effects:
1. Affect the normal work of instruments and meters, which will mislead the operation of the system for the process of automatic control and cause the disorder of the process.
2. The foam enters the secondary sedimentation tank and affects the quality of the effluent.
3. For the process of using surface aeration equipment, it will prevent normal aeration and oxygenation, so that the dissolved oxygen in the aerobic pool is insufficient.
4. Being criticized by leaders, especially by leaders who don't know how to do it.
And so on……
Therefore, it is very important to pay attention to, understand and be able to solve the foam problem of the aeration tank.
01 Where Does The Bubble Come From?
It wasn't made by appointment, it was blown out.
To understand the problem of foam in aeration tanks, you must first understand its principle. The first article makes an analogy of "blowing bubbles", and the principle of foaming in the aeration tank is the same as that of "blowing bubbles". There are two similarities: one is blowing air; the other is the water being blown by air Contains surfactants, sugars and other substances.
The ingredients used to configure bubble water usually include detergent (soap), sugar, tea, etc., which vary, but are basically two types of substances. One is surfactants, such as detergents, soaps, etc. Foaming effect, the second is foam stabilizer, such as sugar, tea, etc., can enhance the viscosity of bubbles, easier to shape, more stable.
The above-mentioned bubble water components or similar substances are easy to appear in sewage, such as surface active substances, filamentous microorganisms, organic substances, etc. When these substances appear, they will blow bubbles in the aeration tank.
02 How To Judge The Composition Of Foam?
Different from the foam blown by the bubble machine, the foam blown by the aeration tank has different characteristics because of its complex composition. Therefore, the causes of foam can be analyzed and judged according to the color, shape, size, and viscosity of the mixture, and the common categories are listed:
white, a small amount of foam
Feature description: The color is white, light and thin, scattered around the aeration area, unstable, easy to break, and the maintenance time is short.
Reason judgment: It is easy to occur in the initial stage of aeration tank startup and denitrification occurs in local areas. Such foam problems will not affect the operation of the process and do not require treatment measures.
khaki foam
Feature description: The surface of the foam is turbid and the color is khaki, similar to the color of activated sludge, easy to break and not easy to accumulate.
Judgment of the cause: the sludge is aging or about to be aging, and part of the sludge disintegrates and dissipates in the water, and evenly adheres to the foam in the aeration state, which enhances the stability of the bubbles and causes the phenomenon of foam accumulation.
gray-black foam
Feature description: The foam accumulates around the aeration group, and the water body is gray-black as a whole, and it is not easy to accumulate.
Reason judgment: anaerobic zone appeared in the aeration tank, part of the activated sludge died and disintegrated, and adhered to the bubbles generated by aeration, which led to the extension of the bubble bursting time and the generation of gray-black bubbles.
03 Countermeasures
Faced with the problem of foam in aeration tanks, first of all, we must know that continuous aeration in a pool of water containing activated sludge and pollutants will inevitably generate bubbles, and most of the bubbles in aeration tanks are normal and do not need to be treated. , the individual needs to focus on the treatment of the situation is nothing more than starting from the three aspects of influent water quality, activated sludge and aeration.
The quality of the influent water is nothing more than regulating the acidity and alkalinity, temperature, surface active substances, etc., and the activity of the sludge is nothing more than controlling the ratio of food to microbes, and then controlling the aeration, mainly in the aeration method and aeration amount, which are the fundamental control measures. , Emergency measures include spraying water, adding defoamer and so on.