What do you mean by activated sludge?

By | January 5, 2022

Activated sludge refers to a flocculent culture of organisms developed in aeration tanks under controlled conditions, according to WEF. Activated sludge is typically brown in color. … Activated sludge also contains populations of fungi, protozoa and higher forms of invertebrates.

How is activated sludge formed?

a When the BOD of sewage or waste is reduced significantly the effluent is then passed into a settling tank where the bacterial flocs are allowed to sediment. This sediment is called activated sludge. … The remaining major part of the sludge is pumped into large tanks called anaerobic sludge digesters.

Where is activated sludge?

The mixed liquor then enters the aeration tank. Air is added to the tank to give oxygen to the microbes and then mix them with the settled sewage. The mixed liquor leaves the aeration tank and goes to the secondary clarifier. Here the activated sludge settles to the bottom and the clear effluent goes over the weirs.

What happen to activated sludge?

The microbe concentration is maintained in the tank by returning a certain portion of the sludge that passes through the tank and is settled out in a secondary sedimentation basin. The activated sludge process produces new cell material which will become part of the activated sludge mass.

Why is it called activated sludge?

They aerated the waste-water continuously for about a month and were able to achieve a complete nitrification of the sample material. Believing that the sludge had been activated (in a similar manner to activated carbon) the process was named activated sludge.

Why is activated sludge called activated?

The activated sludge process was developed in England in 1914 and was so named because it involved the production of an activated mass of microorganisms capable of aerobically stabilizing the organic content of a waste.

What is the difference between sludge and activated sludge?

This sediment is called activated sludge. …

Primary sludge Activated sludge
(iii) It does not require aeration Formation of activated sludge requires aeration
(iv) A lot of decomposition occurs during the formation of primary sludge Very little decomposition occurs during the formation of activated sludge

What is the use of activated sludge process?

The activated sludge process uses microorganisms to feed on organic contaminants in wastewater, producing a purified effluent. The basic principle behind all activated sludge processes is that as microorganisms grow within metabolizing soluted organic material.

Which bacteria play important role in activated sludge treatment?

Protozoa play a critical role in the treatment process by removing and digesting free swimming dispersed bacteria and other suspended particles. This improves the clarity of the wastewater effluent.

Is waste activated sludge?

The excess quantity (mg/L) of microorganisms that must be removed from the process to keep the biological system in balance.

How does aeration tank work?

When is Aeration Used? … Aeration in an activated sludge process is based on pumping air into a tank, which promotes the microbial growth in the wastewater. The microbes feed on the organic material, forming flocks which can easily settle out.

What is conventional activated sludge process?

The activated sludge process is a conventional biological process that is used for reduction of organic matter present in the wastewater. It basically involves the oxidation of carbonaceous biological matter, for reduction of the organic pollutants. … This is a proven technology and can remove majority of organic matter.

Which are the three ingredient in activated sludge system?

Which are the three ingredients in activated sludge systems? Explanation: The cells need oxygen for their metabolism, air is injected from the bottom of the aerator. The water is well agitated by the rising bubbles and creates good contact between the three ingredients: cells, sewage and oxygen.

Does activated sludge have aerobic bacteria?

Activated sludge (AS) is composed of aerobic and anaerobic microorganisms such as bacteria, archaea, fungi, and protists. It is capable of degrading organic compounds, including petroleum products, toluene, and benzopyrene (Seviour and Nielsen, 2010).

What are the limitations of activated sludge process?

Disadvantages of Activated Sludge Process

  • Not very flexible method (If there is sudden increase in the volume of sewage or if there is sudden change in the character of sewage, there are adverse effects on the working of the process and consequently the effluent of bad quality is obtained).
  • Operation cost is high.

What is required to keep activated sludge suspended?

What is required to keep the activated sludge suspended? Explanation: To maintain the aerobic conditions and to keep the activated sludge suspended, a continuous and well-timed supply of oxygen is required. Flocs of bacteria, which are suspended and mixed with wastewater is used for the process.

What are the most important features in activated sludge?

There is a large varity of design, however, in principle all AS consist of three main components: an aeration tank, which serves as bio reactor; a settling tank (final clarifier) for seperation of AS solids and treated waste water; a return activated sludge (RAS) equipment to transfer settled AS from the clarifier to …

What happens inside the aeration tank?

Aeration brings water and air in close contact in order to remove dissolved gases (such as carbon dioxide) and oxidizes dissolved metals such as iron, hydrogen sulfide, and volatile organic chemicals (VOCs).

What are the 3 stages of wastewater treatment?

There are three main stages of the wastewater treatment process, aptly known as primary, secondary and tertiary water treatment.

How is activated sludge used to clean sewage?

The activated sludge is aerated to dissolve oxygen which allows the organic matter (BOD) to be utilised by the bacteria. The organic matter, or food, sticks to the activated sludge. The oxygen dissolved in the water allows the bacteria to use the food (BOD) and also to change the ammonia to nitrate.

What is primary sludge activated sludge?

The primar sludge is formed during primary sewage treatment, while activated sludge is a sludge during secondary sewage treatment, little decomposition occurs during primary sludge formation, while lot of decomposition occurs during activated sludge.

What is the difference between activated sludge process and trickling filter?

The key difference between activated sludge and trickling filter is that activated sludge is a suspended culture system in which biomass is mixed with the sewage while trickling filter is an attached culture system in which biomass is grown on media and the sewage is passed over its surface.

What are the main differences between primary sludge and waste activated sludge?

It does not contain floes of decomposer microbes. Floes of decomposer microbes present.
No aeration is required. It requires aeration.
Very little decomposition occurs during the formation of primary sludge. During the formation of activated sludge, a lot of decomposition occurs.

What is MBR process?

‘Membrane bioreactor’ (MBR) is generally a term used to define wastewater treatment processes where a perm-selective membrane, eg microfiltration or ultrafiltration, is integrated with a biological process specifically a suspended growth bioreactor.

Why urea added in aeration tank?

Afterwards it goes to Aeration Tank where complete process of aeration is installed and Urea and DAP (Di ammonium phosphate) is being used for the bacterial colony to activate the sludge reducing the BOD and COD, after about 30 hours retention time in aeration tank the over flow goes to clarifier tank where the sludge …

What microorganisms are used in sewage treatment?

Following group of microorganisms are mainly present in wastewater treatment process.

  • 2.1. Bacteria. …
  • 2.2. Protozoa. …
  • 2.3. Metazoa. …
  • 2.4. Filamentous bacteria. …
  • 2.5. Algae. …
  • 2.6. Fungi.

How many bacteria are in an aeration tank?

In wastewater treatment, there are three types of bacteria used to treat the waste that comes into the treatment plant: aerobic, anaerobic and facultative. Aerobic bacteria are used in most new treatment plants in an aerated environment.