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2011 environmental protection engineer comprehensive summary: talking about water treatment knowledge

2011 Environmental Protection Engineer: water treatment knowledge handout

2.1 activated sludge process

2.1.1 basic process flow of activated sludge process

1 The basic concept of activated sludge method

inject air into domestic sewage and aerate it, retain sediment every day, and replace fresh sewage. After this operation and lasting for a period of time, a kind of yellowish brown flocs, namely activated sludge, will be generated in sewage. The biological treatment process of sewage with activated sludge as the main body is called activated sludge process

activated sludge plays a major role in activated sludge process. Microbial communities with strong vitality and the ability to degrade organic matter in water inhabit on activated sludge

2. Basic process flow of activated sludge process

the basic process flow of activated sludge process consists of five parts: aeration tank, secondary sedimentation tank, aeration system, sludge reflux and excess sludge discharge

wastewater and returned activated sludge enter the aeration tank together to form a mixed liquid. The aeration tank is a biological reactor, which is filled with air through the aeration equipment, and the oxygen in the air is dissolved into the mixture to produce an aerobic metabolic state. Then the sludge water mixture in the aeration tank flows into the secondary sedimentation tank for sludge water separation. The activated sludge flocs sink into the bottom of the tank, and the water after sludge water separation is discharged into the secondary sedimentation tank as treated water. Most of the sludge settled in the secondary sedimentation tank is returned to the aeration tank as reflux sludge, which is called reflux sludge, and the rest is discharged from the sedimentation tank, which is called surplus sludge

from the above process, it can be seen that in order to form a practical treatment method for the activated sludge method, the sludge should not only have (9) the ability of building blocks to oxidize and decompose organic matter, but also have good coagulation and sedimentation performance, so that the activated sludge can be separated from the mixed liquid to obtain clarified effluent

2.1.2 morphology and composition of activated sludge

1, morphology of activated sludge

floc morphology and microbial composition, quantity, characteristics of pollutants in sewage and external conditions of activated sludge floc size is generally between 0.02~0.2mm, in an uncertain shape, slightly soil flavor. Activated sludge has a large specific surface area, up to 2000~10000m2/m3

2. The plastic extruder industry in China is moving towards a healthy and sustainable development. The composition of activated sludge

activated sludge is mainly composed of four parts: active microbial population with metabolic function; Residues of endogenous respiration and self oxidation of microorganisms; Refractory organic matter adsorbed by sludge flocs; Inorganic matter adsorbed by sludge flocs

the purification function of activated sludge mainly depends on the microorganisms inhabiting the activated sludge. Activated sludge microorganisms are mainly aerobic bacteria, but also live fungi, protozoa and metazoans. These microbial communities form a relatively stable ecosystem. The bacteria in activated sludge are mainly heterotrophic prokaryotic bacteria. For normal mature activated sludge, the number of bacteria per ml of activated sludge is roughly 107~109. Although bacteria are the main component of microorganisms, which species and genera of bacteria in activated sludge are dominant depends on the components of organic matter contained in sewage and the operating conditions of activated sludge process and other factors

fungal structure is complex and diverse, and it is a multicellular heterotrophic microorganism. Fungi related to activated sludge treatment are mainly molds. Mold is a tiny saprophytic or parasitic filamentous fungus, which can decompose carbohydrates, fats, proteins and other nitrogen-containing compounds. However, the proliferation of fungi will produce sludge bulking, which will seriously affect the normal work of activated sludge system. The appearance of fungi in activated sludge process is often related to water quality

bacteria are the main feeding objects of protozoa. Protozoa in activated sludge mainly include sarcopods, flagellates and ciliates. Protozoa are unicellular organisms, mostly aerobic heterotrophic bacteria. In the application of activated sludge method, it is often judged indirectly that the scope of sewage treatment includes the effects of biological plastics, biological rubber, biological fiber, biological coating, biological adhesive, biological machinery, biological detection and other mechanisms by observing the species and quantity of protozoa. Therefore, protozoa is also called the indicator animal of activated sludge system

metazoans (such as rotifers, nematodes, etc.) that feed on bacteria, protozoa, and activated sludge debris do not often appear in activated sludge, especially rotifers are only more common in systems with low organic content and good water quality (i.e., fully oxidized activated sludge systems). Therefore, rotifers are also known as indicator animals of activated sludge systems, and are a sign of good effluent quality

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