Yellow? black? Take you to a detailed explanation of the aeration tank foam

Author: Xiao La, sewage operation, text editing, sewage treatment, learning and personal growth, pay attention to and private messages to me

Reply to the number "01" and send you a starter package for beginners.

A better classification method for biochemical foams is by color and viscosity, because confirming the different colors and viscosities of the foam can guide us to determine the current state of activated sludge.

01 brownish yellow bubble

1 Phenomenon description

The foam is produced in small quantities, a small amount of liquid near the aeration mass, gradually dissipates along the direction of radiation, and begins to accumulate when it reaches the surrounding corners, and the foam color is brownish yellow, and the foam color is the same as the color of the activated sludge at that time. During the entire foam formation to accumulation, the foam is fragile, so such foam will not accumulate seriously in a short period of time and lead to a large amount of scum.

2 Cause analysis

Activated sludge is in an aging state, part of the activated sludge disintegrates due to aging, suspended in the activated sludge mixture, and evenly adheres to the foam in the aeration state, resulting in a prolonged time for foam bursting, which creates conditions for foam accumulation.

3 process judgment

This type of foam generation is a manifestation of the sludge being or about to enter a state of activated sludge aging.

1. The sedimentation ratio of activated sludge

The sedimentation ratio observation of activated sludge is one of the important methods to judge whether the activated sludge has aging, through whether the sedimentation ratio is small, whether the settled activated sludge is dark yellow in color, whether the sedimentation rate is too fast, etc., combined with the brown-yellow foam generated by the liquid level, it can be more accurately judged whether the activated sludge has an aging phenomenon.

2. SVI value aspect

The SVI value is used to judge the looseness of the activated sludge, which is indeed a good indicator, but it also has the function of judging whether the activated sludge has aged. When the SVI value is lower than 40, the activated sludge usually ages, and the brownish yellow foam generated by the liquid level can be more accurately judged whether the activated sludge has aged.

3. Microscope observation results

For aging activated sludge, microscopic observation can also be well found. The focus is on the degree of denstriction of the fungal micelle and the proportion of the emergence of the epizoan, if the observed hysteroid is relatively dense, and there are a large number of epizoans, combined with the brownish yellow foam of the liquid surface, it can be judged whether the activated sludge is in the aging stage.

02 gray black bubble

The number of foams, the production process, the accumulation, the fragility are the same as the brown-yellow foam, but its color has a black component, and the accumulated products are also gray-black, and the color of the activated sludge observing the entire biochemical system also has a slight gray-black feeling.

Activated sludge is in a hypoxic state, and the hypoxic state can cause a local anaerobic reaction of the activated sludge, so that the activated sludge that was originally in an aerobic state will die in this process of transformation, and it will also be attached to the bubbles during aeration.

Therefore, if we see that the resulting foam is gray-black, in addition to confirming whether the inlet water contains black dye wastewater, the main thing is to confirm whether the biochemical tank has an anaerobic situation caused by insufficient aeration in the local area.

Most of the gray-black foam is an oxygen-deficient or anaerobic state of the activated sludge system, and the confirmation of the corresponding process control indicators needs to be carried out around this aspect. When gray-black foam is generated, the focus needs to be comprehensively judged on the DO value.

The best way to confirm whether the activated sludge system is in an anaerobic and anaerobic state is to conduct field testing directly through the dissolved oxygen meter, and the mistake that our operators are prone to make in this regard is to detect only one point to judge the overall dissolved oxygen status of the biochemical system, which is one-sided.

In order to avoid this, it is necessary to conduct field testing of the uniform distribution point of the entire biochemical system, only in this way can the local oxygen supply shortage blind spots be found. If dissolved oxygen is monitored at locations below 0.5 ppm, we need to focus on confirming these locations.

03 White bubble

There are many reasons for white foam, but they are mainly often caused by excessive load, excessive aeration, and detergent inflow. When distinguishing what causes white foam, the viscosity of the foam can give us a lot of reference.

Usually, the viscous foam that is not easy to break is commonly found in the activated sludge load is too high, and the foam color at this time is bright white and the accumulation is better, while the viscous and easy to break foam is often over-aerated in the activated sludge, and the foam color at this time is old white, the accumulation is poor, only local accumulation will occur, and the inflow of detergent will also occur white foam, because the presence of detergent increases the surface tension of the water body, which eventually leads to the formation of foam.

2 process judgment

The generation of white foam is basically attributed to the excessive load of activated sludge, excessive aeration, and the inflow of detergent.

1. The relationship between F/M value and white foam

We know that the indicator of judging the load of activated sludge is F/M (that is, the micro ratio of food), if the F/M value is too high (greater than 0.5), and a large amount of white viscous foam is generated, we can think that the activated sludge is indeed in a state of high load operation.

2.DO value in relation to white foam

Excessive aeration will also produce a large number of white foam, although in the case of low foam viscosity, the normal aeration volume will not lead to the generation of biochemical system foam, but the activated sludge under the action of excessive aeration, part of the activated sludge will disintegrate and dissolve, which will then lead to an increase in the organic content of the activated sludge purve, which is a reason for the foam generation in the case of high aeration.

To this end, in the case of ensuring the oxygen supply of activated sludge, the amount of aeration is reduced as much as possible, which can not only reduce foam generation, but also reduce energy consumption and reduce operating costs. Usually the control aeration tank outlet DO value is 1-3mg/l, if you blindly increase the aeration capacity, so that the DO rises to 5.0mg/l, the negative impact on the activated sludge system is larger.

3. The problem of the inflow of foaming substances

In addition to the treatment load is too high, excessive aeration, the flow of foaming material into the biochemical system can also lead to the formation of foam in the activated sludge system, more common is the inflow of detergent or surfactant in the biochemical system, under the action of aeration, a large amount of white foam will soon be produced. By monitoring the DO value and the sludge load of the biochemical system at that time, we can infer whether the influence of the inlet water quality has led to the generation of the activated sludge system foam.

04 color bubble

Colored foam often occurs in the biochemical system into the colored wastewater, usually these colored wastewater has a high concentration of organic matter, under the action of aeration, it is easy to cause similar to the foam produced during high loads. Since the body of water itself has a color, the naturally occurring foam will also have a color.

Another case is that sewage, wastewater is rich in surfactants or detergents, after flowing into the biochemical system, it will naturally lead to foam, in the sunlight, the surface of these foams will produce colorful colors, which is very helpful for judging the cause of such foam.

The production of colored foam is related to the inflow of colored wastewater and the inflow of detergents and surfactants. Therefore, it can be judged by observing whether the water treated in the materialization area still has color. For example, whether some wastewater will also cause color interference to the biochemical system. On the issue of detergents and surfactants, the focus is also on confirming the foam accumulation in the location of the physicochemical zone. From this, the effect of surfactants and detergents on the foam generation of subsequent biochemical systems is judged.

Activated sludge is a dynamic system that means to see more, observe, and think more in daily operation. In addition to the observation of pool surface foam, we must always pay attention to the situation of liquid surface scum, with a number of indicators, such as SV30, dissolved oxygen, food micro ratio, biological phase observation, etc., in order to quickly and accurately make process judgments.

I am a small la, click on the top "follow", every day for you to share sewage treatment thousands of goods, private messages I reply to the number

The word "01" sends you a sewage treatment starter package