In the operation of sewage treatment plants, the phenomenon of activated sludge poisoning is occasionally encountered. Toxic activated sludge exhibits many different forms. The poisoning of activated sludge is usually divided into two types, acute poisoning and chronic poisoning, just like humans and animals. Acute poisoning poses significant challenges to the operation of integrated equipment. However, for chronic poisoning, activated sludge has various forms of manifestations. The operation and maintenance personnel of integrated equipment are like doctors, and there are still many ways to solve chronic poisoning of activated sludge. However, in practice, when operators discover signs of chronic poisoning, they fail to adjust the process in a timely manner, resulting in the death of activated sludge. The rural activated sludge poisoning incidents mainly come from farmers flushing a large amount of pesticides into the sewage treatment system and industrial wastewater containing a large amount of chemical agents overflowing into integrated equipment. The integrated equipment itself is biodegradable, and if the concentration is insufficient, the growth state of activated sludge is poor. In addition, the inflow of toxic sewage can lead to poisoning, which is understandable. What are the key points for judging activated sludge poisoning?
1. Observe through a microscope. The first step is to observe the death of protozoa in activated sludge. Protozoa are represented by nematodes. If all the nematodes disappear, it can be determined whether toxic wastewater has flowed into the integrated equipment. Six hours after the death of the nematode, the body will be hydrolyzed and disappear. So, the disappearance of native organisms is used to determine whether activated sludge is poisoned.
2. Determine by the sedimentation ratio of activated sludge. The first manifestation of poisoned activated sludge is a decrease in the settling ratio of activated sludge and the death of protozoa. In order to preserve the activity of the microbial flocs, activated sludge sacrifices the bacteria on the periphery of the flocs, so the dead bacteria on the periphery will free up and distribute into the wastewater of the equipment. At the same time, the coarse bacterial flocs in activated sludge will also disintegrate and become finer and smaller. At this point, we will notice that there are many small particles in the water that cannot settle. The coagulation of activated sludge deteriorates, and the coagulation time is long.
3. Determine the presence of floating debris on the liquid surface. After activated sludge poisoning, dead bacterial colonies will form liquid surface scum under the action of aeration. The operator needs to observe the characteristics of the floating slag on the liquid surface to determine the situation of activated sludge poisoning. For example, the floating slag on the liquid surface is thin and loose, with a dark color. After being poisoned by active bacteria, there will be no bright color of activated sludge. Dead activated sludge will no longer have the ability to adsorb to each other, so the floating slag is also very loose.
4. Detect the change status of dissolved oxygen (DO). After activated sludge poisoning, as the death of activated sludge bacteria continues to decrease, we will find that the dissolved oxygen (DO) in the mixed liquid of the aeration tank gradually increases under the condition of constant aeration amount. At the same time, the removal rate of organic matter is gradually decreasing. This trend is also the main basis for us to judge activated sludge poisoning.
5. Changes in equipment water output. After activated sludge poisoning, effluent testing will reveal a continuous increase in COD concentration, which is due to the mixing of a large amount of decomposed activated sludge in the water. And the effluent is turbid. The treatment measures for activated sludge poisoning were discussed earlier. I will discuss the treatment strategies for activated sludge poisoning in the following article.
When carrying out rural sewage treatment projects, integrated equipment inevitably encounters the situation of activated sludge poisoning. In the previous article, we analyzed the symptoms of activated sludge poisoning. Now we will share some countermeasures for activated sludge poisoning. This is crucial for quickly restoring the performance of activated sludge and avoiding destructive effects on activated sludge. When we first identify activated sludge poisoning, there are several methods that need to be taken
. 1. Immediately block the further entry of toxic wastewater. This is the most important step in the entire process of treating activated sludge poisoning. The ability of organisms in the activated sludge of integrated equipment to withstand toxins is limited, and long-term high concentrations of toxic substances can easily cause the death of activated sludge in the equipment. To avoid this situation, we need to find the source of the toxin as soon as possible. This is not difficult for small-scale sewage treatment equipment. Cut off the source of toxins.
2. For toxic substances that have already entered the equipment, operators should dilute the mixture of toxic substances as soon as possible. Because activated sludge has some impact resistance to toxins of different concentrations. If detected in a timely manner, the non poisoned end can be refluxed to the first section of the biochemical pool. 3. Use sludge discharge methods to achieve resistance to the impact of toxic substances. The main operation is to discharge damaged or dead sludge and replenish newly generated activated sludge to improve the activity of the current activated sludge. The amount of sludge to be discharged should be determined by the food ratio, with a maximum control of around F/M=0.5 being the most reasonable!
