What is activated sludge in industrial sewage treatment?

Activated sludge (activesludge) is a general term for microbial communities and the organic and inorganic substances they attach to, discovered in 1912 by Clark and Gage in the United Kingdom, activated sludge can be divided into aerobic activated sludge and anaerobic granular activated sludge, activated sludge is mainly used to treat wastewater.

Activated sludge method is a kind of aerobic treatment method that uses suspended microbial flocs to treat organic sewage.

The complex microorganisms in activated sludge and the organic nutrients in wastewater form a complex food chain. The first to take on the purification task is the isoxic bacteria and saprophytic fungi, bacteria, especially globular bacteria play the most critical role, and the well-functioning activated sludge is a mycoplasm composed of filamentous bacteria as the skeleton of globular bacteria. Good sedimentation, with the normal operation of activated sludge, bacteria multiply in large numbers and begin to grow protozoa, which is a predator of bacteria.

Common protozoa of activated sludge are flagellates, flesh caterpillars, ciliates and strawworms.

When the activated sludge matures, sessile ciliates and seed worms are dominant; Metazoans are secondary predators of bacteria, such as rotifers, nematodes, etc., which can only appear when the dissolved oxygen is sufficient, so when metazoans appear, it indicates that the treated water quality is improving. Its performance indicators include: Mixed Suspended Solids (MLSS), Sludge Sedimentation Ratio (SV), Sludge Index [Sludge Volume Index (SVI), Sludge Density Index (SDI)].

From a microbiological point of view, the sludge in the biochemical tank is a biological group composed of a variety of biologically active microorganisms. If you look at the sludge particles under a microscope, you can see that there are a variety of microorganisms--- bacteria, molds, protozoa and metazoa (such as rotifers, insect larvae and worms, etc.), which form a food chain, and bacteria and molds can break down complex organic compounds, obtain the energy necessary for their own activities and structure themselves. Protozoa feed on bacteria and molds, which in turn are consumed by metazoans, which can also live directly on bacteria.

This kind of flocculent sludge particles that are full of microorganisms and have the ability to degrade organic matter are called activated sludge.

In addition to being composed of microorganisms, activated sludge also contains some inorganic substances and organic matter adsorbed on activated sludge that can no longer be biodegraded (i.e., metabolic residues of microorganisms). The moisture content of activated sludge is generally 98-99%. Activated sludge, like alum flowers, has a large surface area, so it has a strong adsorption force and the ability to oxidatively decompose organic matter.

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A variety of chemicals can be used for sludge deep dewatering, and the following are the most common chemicals used for ordinary sludge dewatering:

Cationic polyacrylamide: This is a polymer flocculant, which can flocculate small particles in sludge into larger particles through adsorption and bridging, and improve the sedimentation performance and dewatering performance of sludge.

Polyaluminum chloride: This is an inorganic polymer coagulant, which can coagulate with impurities in the sludge to form an insoluble precipitate, so that the water in the sludge is separated.

Lime: Lime can neutralize with the acids in the sludge, adjust the pH value of the sludge, and promote the cohesion and settlement of the sludge.

Diatomaceous earth: Diatomaceous earth has the characteristics of porosity and high specific surface area, which can be used as a filter aid to improve the filtration performance and dewatering performance of sludge.

It should be noted that different kinds of agents are suitable for different sludge properties and treatment requirements, so it is necessary to choose the appropriate agent according to the specific situation in practical applications. For sludge with high organic matter, under the condition that lime is not allowed to be added in the process, it is necessary to customize the organic deep sludge dewatering agent, and adjust the corresponding process parameters to ensure the sludge treatment effect.

Activated sludge treatment wastewater knowledge 02

Answer]: Active brother sludge refers to the flocculent formed by microorganisms such as bacteria and protozoa mixed with suspended matter and colloidal substances, and has a strong ability to adsorb and decompose organic matter. The activated sludge method is the most widely used method for treating municipal domestic sewage.

It removes dissolved and colloidal biodegradable organics, as well as suspended solids and other substances that can be adsorbed by activated sludge from wastewater. Inorganic salts (phosphorus, jujube and nitrogen compounds) can also be partially removed. Industrial wastewater, similar to municipal sewage, can also be treated with activated sludge.

The sewage treatment industry often talks about activated sludge, and domestic sewage treatment equipment is also indispensable when treating sewage.

The key to activated sludge lies in its "activity", it is not mud in the traditional sense, it is particles and flocs with the ability to adsorb and decompose pollutants. It is mainly composed of four parts:

1. Active microorganisms with metabolic functions, such as our common bacteria;

2. Residues of endogenous respiration and self-oxidation of microorganisms, such as bacterial corpses and excrement;

3. Adsorbed refractory organic matter, such as plastics;

4. And adsorbed inorganic substances, such as fine sand.

Activated sludge plays its role in different forms in sewage and wastewater treatment. It can not only help the strains grow better, but also ensure that the strains will not be lost with sewage, and at the same time degrade COD, ammonia nitrogen, adsorption of impurities and other effects.

When the activated sludge method is used in sewage treatment, special attention should be paid to its performance indicators, including: mixed liquid suspended solids (MLSS), sludge sedimentation ratio (SV), sludge volume index (SVI), color, odor, etc.