In the daily operation and management of sewage plants, our front-line operators often like to use the concept of engineering to manage sewage treatment, and like to use parameters such as adjusting aeration volume, adjusting the flow rate and so on to do the management of sewage plants. It is hoped that the management of sewage plants will be summarized into some engineering indicators, relying on these to complete the regulation of a sewage plant. And to talk about microbes only as an observation during microscopy, or just a very vague concept.
Today I would like to explain the operation and management of sewage plants from another perspective, that is, the perspective of microorganisms. Why talk about this from the perspective of microorganisms, let's review what the source of wastewater treatment is.
The concept of sewage treatment plant, that is, the sewage treatment plant comes from the principle of self-purification of water bodies in nature, that is, when our original environmental condition is good, people in the upper reaches of the river are washing things, and people downstream can also use the water of this river. It is not that the people downstream have been polluted so badly, but in the case of environmental capacity, the small pollution in the upstream can be self-purified by the river, and when it reaches the downstream, the water body has been completely cleaned to the standard of reuse, and the sewage plant is the artificial strengthening process of this natural water body self-purification. Through engineering and technical means, the sewage plant has completed the effect that nature needs a long self-purification process in a short period of time and in a small space.
The self-purification ability of natural water bodies comes from various microorganisms in natural water bodies, and under the joint action of these microorganisms, the organic matter in sewage is decomposed and transformed into CO2 and water, nitrogen and so on. But these microbes are scattered sporadically throughout the natural body of water and do not come together. The artificial strengthening principle of the sewage plant is to collect these scattered microorganisms scattered in the natural water body into the designated pool of water, so that the sewage can achieve the effect of treatment through this pool.
Since the core of the sewage treatment plant is a treatment pool with a high density of microorganisms, this treatment pool must have the same characteristics as the natural water body. It can also be said that the sewage treatment plant is also an artificial ecosystem. Although it is an artificial ecosystem, it must meet the various characteristics of the ecosystem, only this ecosystem is a complete system, the core system of sewage treatment will operate stably, and it will be able to meet the daily needs of our sewage treatment.
Let's look at the meaning of the ecosystem, which is actually a natural body composed of organisms and the environment in which they live within a certain spatial range. Organisms undergo a series of energy exchanges in this environment, completing the flow of energy. This is the concept of an ecosystem, in layman's terms, that is, a group of creatures eating, drinking and sleeping in a room, living with wine and meat, and having perfect measures to keep the room environment good. There are all kinds of ecosystems in nature, a pond, a river, a rice field, a mountain, a forest are all an ecosystem, and the whole natural world is composed of such ecosystems. The sewage plant is an artificial ecosystem, an artificially created sewage ecosystem. At this stage, the whole world is shouting eco-friendliness, in fact, for the management of a sewage plant, it is really necessary to carry out from an eco-friendly perspective.
Ecosystems can be easily understood through observable ecosystems, such as ponds. There is a saying that goes like this: big fish eat small fish, small fish eat shrimp, shrimp eat aquatic grass... This is actually talking about the composition of a pond ecosystem, a complete ecosystem will have a complete biological chain, and the stronger the ecosystem, the longer the biological chain, the better the environment, the longer the biological chain. In the process of continuous elevation, the biological chain has completed the transmission and transformation of energy and ensured the ecological balance within an ecosystem, so in the artificial ecosystem of a sewage treatment plant, back under the microscope, how do we understand the biological chain of the ecosystem of the sewage plant?
Since the sewage plant is an ecosystem, it must have all the characteristics of the ecosystem, and the ecosystem can actually be divided into two parts: biome and environmental conditions. For the artificial ecosystem of the sewage treatment plant, it is actually a greatly simplified ecosystem corresponding to the natural ecosystem, and its biome is limited to the microbial form of organisms, and its environmental conditions are only a single environment of domestic sewage or industrial wastewater. From the perspective of the sewage plant to examine the basic composition of the ecosystem, first of all, the inorganic environment, is all the anthropogenic process treatment structures in the sewage plant constitute the aerobic anaerobic and hypoxic inorganic environment of the sewage treatment ecosystem; while the biome part is mainly heterotrophic microbial community, the protozoa microfauna undertake the decomposition and transformation of the polluting substances in the sewage. From the basic composition of this artificial ecosystem, it can be seen that the management of the artificial ecosystem of a sewage treatment plant is carried out around the microbial community.
A synthesis of various microorganisms in the sewage plant and some organic and inorganic particulate matter mixed together to form a flocculent that we call activated sludge. Activated sludge is explained in detail in various textbooks, and it will not be explained in detail. This time focus on the activated sludge from the perspective of the microbial community of activated sludge, for any activated sludge floc, its center is the bacterial gelocellation formed by bacteria, and then on the collection of bacterial gel group, other kinds of microorganisms are grown, such as some fungi, as well as protozoa and some protozoans. These bacteria mainly come from the soil, air and water bodies in nature, and the construction concept of all the treatment structures in the sewage plant is to provide these microorganisms with nutrients, oxygen, temperature and PH value that are most suitable for their growth. (Today's main talk about the activated sludge method, some concepts of biofilms will not be elaborated here, there are certain differences, but the ecological principle is very close.) ）
After understanding the basic composition, let's look at the food chain or an evolutionary system of the artificial ecosystem of the sewage plant. We know that the entire biological world is an evolutionary process from low to high, and the microorganisms at the lowest end are highly adaptable to the environment and are insensitive to changes in environmental factors. Low-end microorganisms are basically at the lowest level of biological forms because of incomplete evolution and no complex organ differentiation, and they will adjust their own changes to adapt to changes in the environment with changes in the environment. However, due to the more perfect evolution of higher animals, they are extremely adaptable to changes in the external environment, and environmental changes are often more sensitive to the impact of these higher organisms.
The evolution of microbial populations in the artificial ecology of a sewage plant, or the food chain, goes like this: bacteria - meat-footed insects (amoeba) - plant-based flagellars - animal flagellars - swimming ciliates - fixed ciliates - rotifers.
For any ecosystem, bacteria must be the lowest biome, they generally come from the sewage pipe network, exist in the sewage outlet, the inlet part of the sewage plant, etc., undertake the most basic biodegradation function of the initial sewage, decompose and transform organic pollutants, organic macromolecular substances. They are microorganisms that are in direct contact with the polluting substances in the sewage, their structure is simple, the nutritional methods are varied, the adaptability is very strong, they are the most basic microorganisms in the sewage treatment plant, their size is between a few microns, and they need oil mirrors and Gram staining methods under the microscope to see, and the general microscopy method cannot be seen, so they are not used as the main microscopic objects of the sewage plant.
In the biological treatment process of sewage, the main role is bacteria, followed by protozoa. The protozoa in the water bodies we are primarily concerned with are the lowest single-celled animals in the animal kingdom. They have some common characteristics, the individual is very small, the length is 100 to 300 microns, has its own independent and perfect physiological organism, can complete nutrition, breathing, excretion, reproduction and other functions. The following is an introduction to several types of protozoa.
Flesh-footed insects, also known as metamorphic insects, they do not have a fixed form, most of them are spherical, common sun worms, amoebas, are widely distributed in nature, and the most widely distributed in the contamination water body. However, in sewage plants, it mainly exists in the early stage of culture, and in the later stage, with the emergence of other types of protozoa, amoeba gradually ceases to dominate.
Flagellar is a protozoa slightly higher than bacteria, divided into plant and animal nature, which means that the flagella still has a lot of bacterial characteristics, because they are closer to lower organisms, they can even change their own nutritional methods back and forth for environmental changes, can have some characteristics of autotrophic and heterotrophic types, can eat other microorganisms for food, can also feed themselves, so it is in the second level of the food chain, the shape of the flagellar is between a few microns and tens of microns, requiring a high multiple microscope to see, It is generally difficult to distinguish, so in practice, flagellar is not used as a microscopic microorganism.
Ciliates are divided into swimming and fixed types, ciliates are the most advanced type of protozoa, with fixed, well-structured feeding cell organelles. Swimming ciliates mainly include grasshoppers, kidney worms, bean worms, roaming worms, shield fibral worms and so on. The fixed type is mainly bell worms, and the bell worms are divided into single bell worms and group clock worms, and the single bell worms have small mouth clock worms, ditch clock worms, collar clock worms and so on. Population bellworms include isophyllus (P. reedia) and capworm. The tail stalks of the bell-shaped bodies of isophyllum are generally interconnected in an isophylloid form. Ciliates can swallow large numbers of bacteria, promote biological flocculation, and are larger and can be observed by low-power microscopy, so ciliates are the main microscopic microorganisms.
Above the protozoa there are also epizoans, and in the activated sludge, the most common probiotic animals are mainly rotifers, nematodes, etc.
The food chain of microorganisms is such a component, in fact, it is easy to distinguish from the body, the larger the microbial level, the higher the level, the more at the top of the food chain. But because they are at the top, the nutritional mode or food material begins to be monolithic, the greater the impact of the impact load, the more sensitive to changes in the external environment, so we do microscopic observation of microorganisms will choose a relatively large, upstream of the food chain of some microorganisms, such as bell worms, tired branches, fibrous worms, etc. as the focus of the observation object, using their changes to investigate changes in the treatment environment, infer the changes in water quality, We put the microscope objective lens between 10 and 40 times to see these microorganisms are collectively referred to as indicative microorganisms, a sewage plant through long-term microscopic observation of these indicative microorganisms, basically can roughly judge the changes in the aeration environment and the changes in the quality of the inlet water, and can predict the change of water quality.
In addition, we often find that some larger volumes of organisms visible to the naked eye appear in the aeration tank or the second sedimentation tank and later in the pool, which is not a microorganism in the strict sense, they belong to aquatic small animals, these small animals are already behemoths relative to the microorganisms in our sewage plant, the emergence of these animals is generally the product of the evolution of the entire sewage plant ecosystem to a very high level, these small animals can not live in the activated sludge, can only float in the water body, Therefore, the appearance of these means that the water body stays in the sewage plant for too long, and the planktonic small animals have a good living space and can reproduce and grow.
In the daily microscopy, we also have some special attention to the emergence of individual microorganisms, in fact, these microorganisms suddenly appear, there is no representative significance, can not take the emergence of individuals as a characteristic of group representation to examine changes in water quality. In particular, some special microorganisms may exist in the sewage pipe network and be brought into the sewage plant, and these microorganisms are not used as the main object of judgment.
Source: Pollution control said fish