Activated Sludge Process
- Primary Treatment. Screening: The raw-sewage waste goes into the bar rack screening via pipe inlets, in which the coarse solids like rags, debris etc. ...
- Secondary Treatment. It is the most crucial step of the wastewater treatment, which filters out the effluent from the waste activated sludge.
- Tertiary Treatment. ...
Full Answer
What is activated sludge used for in sewage treatment?
In a sewage (or industrial wastewater) treatment plant, the activated sludge process can be used for one or several of the following purposes: oxidizing carbonaceous matter: biological matter. oxidizing nitrogeneous matter: mainly ammonium and nitrogen in biological materials. removing phosphate.
What are the main variables of activated sludge process?
The main variables of activated sludge process are the mixing regime, loading rate, and the flow scheme. Generally two types of mixing regimes are of major interest in activated sludge process: plug flow and complete mixing.
What is the mechanism for mixing of sewage and sludge?
As the sewage rises the oxygen forced into solution by the pressure at the base of the shaft breaks out as molecular oxygen providing a highly efficient source of oxygen for the activated sludge biota. The rising oxygen and injected return sludgeprovide the physical mechanism for mixing of the sewage and sludge.
What is the primary treatment of sewage?
Primary treatment/Physical treatment: It involves the removal of large and small particles from sewage. The floating debris is first removed by sequential filtration through wire mesh screens.
Is activated sludge primary or secondary treatment?
Secondary Treatment From the Primary Clarifiers, the wastewater flows into large, rectangular tanks called Aeration Basins, where a biological treatment called the “activated sludge process” occurs. The wastewater flows slowing through a series of chambers as large volumes of air are bubbled up through the water.
Is activated sludge a primary treatment?
Secondary Treatment The secondary stage of treatment removes about 85 percent of the organic matter in sewage by making use of the bacteria in it. The principal secondary treatment techniques used in secondary treatment are the trickling filter and the activated sludge process.
What is activated sludge with respect to sewage treatment?
The activated sludge process is a means of treating both municipal and industrial wastewater. The activated sludge process is a multi-chamber reactor unit that uses highly concentrated microorganisms to degrade organics and remove nutrients from wastewater, producing quality effluent.
How does activated sludge treatment help in secondary treatment?
Activated sludge is a common suspended-growth method of secondary treatment. Activated sludge plants encompass a variety of mechanisms and processes using dissolved oxygen to promote growth of biological floc that substantially removes organic material.
What is primary and secondary treatment of sewage?
Primary treatment works on sedimentation, where solids separate from the water through several different tanks. In contrast, secondary treatment uses aeration, biofiltration and the interaction of waste throughout its process.
What is secondary treatment of sewage?
Secondary wastewater treatment processes use microorganisms to biologically remove contaminants from wastewater. Secondary biological processes can be aerobic or anaerobic, each process utilizing a different type of bacterial community.
What are the steps of activated sludge process?
Treatment StepsStep 1: Screening and Pumping. ... Step 2: Grit Removal. ... Step 3: Primary Settling. ... Step 4: Aeration / Activated Sludge. ... Step 5: Secondary Settling. ... Step 6: Filtration. ... Step 7: Disinfection. ... Step 8: Oxygen Uptake.
Which process is provided after activated sludge process?
Which is the next reactor after activated sludge reactor in the treatment process? Explanation: Clarifier (settling tank) is the next reactor where the solids (mostly cells, called sludge at this stage) are separated from the water.
Why it is called activated sludge process?
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.
What is sewage sludge used for?
Once treated, sewage sludge is then dried and added to a landfill, applied to agricultural cropland as fertilizer, or bagged with other materials and marketed as “biosolid compost” for use in agriculture and landscaping.
What steps are taken during secondary treatment?
Secondary treatment removes the soluble organic matter that escapes primary treatment. It also removes more of the suspended solids. Removal is usually accomplished by biological processes in which microbes consume the organic impurities as food, converting them into carbon dioxide, water, and energy…
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. In some applications, more advanced treatment is required, known as quaternary water treatment.
What is activated sludge?
Activated sludge (AS) is a process dealing with the treatment of sewage and industrial wastewaters and developed around 1912-1914. 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 ...
What is the mixing regime of activated sludge?
Mixing Regime. Generally two types of mixing regimes are of major interest in activated sludge process: plug flow and complete mixing. In the first one, the regime is characterized by orderly flow of mixed liquor through the aeration tank with no element of mixed liquor overtaking or mixing with any other element.
What is a nitrified liquor pump?
Many sewage treatment plants use axial flow pumps to transfer nitrified mixed liquor from the aeration zone to the anoxic zone for de-nitrification. These pumps are often referred to as Internal Mixed Liquor Recycle pumps (IMLR pumps). The raw sewage, the RAS, and the nitrified mixed liquor are mixed by submersible mixers in the anoxic zones in order to achieve de-nitrification.
How is sewage treated in a short supply area?
Where land is in short supply sewage may be treated by injection of oxygen into a pressured return sludge stream which is injected into the base of a deep columnar tank buried in the ground. Such shafts may be up to 100 m deep and are filled with sewage liquor.
What is a brush aerator?
In some areas, where more land is available, sewage is treated in large round or oval ditches with one or more horizontal aerators typically called brush or disc aerators which drive the mixed liquor around the ditch and provide aeration. These are oxidation ditches, often referred to by manufacturer's trade names such as Pasveer, Orbal, or Carrousel. They have the advantage that they are relatively easy to maintain and are resilient to shock loads that often occur in smaller communities (i.e at breakfast time and in the evening).
What is the name of the mixture of raw sewage and biological mass?
The mixture of raw sewage (or industrial wastewater) and biological mass is commonly known as Mixed Liquor.
How is sewage liquor run into a tank?
Sewage liquor is run into deep tanks with diffuser blocks attached to the floor. These are like the diffuser blocks used in tropical fish tanks but on a much larger scale. Air is pumped through the blocks and the curtain of bubbles formed both oxygenates the liquor and also provide the necessary stirring action.
What is activated sludge?
The bacterial flocs settle down and the sediment is now called activated sludge. A small part of the sludge is used as an inoculum in the aeration tank and the remaining part is passed into large tanks called anaerobic sludge digestors. In the digestors, heterotrophic microbes anaerobically digest bacteria and fungi in the sludge producing ...
What is the primary treatment of sewage?
1. Primary treatment/Physical treatment: It involves the removal of large and small particles from sewage. The floating debris is first removed by sequential filtration through wire mesh screens. Then, soil and smaller particles are removed by sedimentation in the settling tank. The sediment is called primary sludge and the supernatant is called effluent. The effluent is then sent for secondary treatment.
Activated Sludge Process
Purpose
- In a sewage (or industrial wastewater) treatment plant, the activated sludge process can be used for one or several of the following purposes:
- oxidizing carbonaceous matter: biological matter.
- oxidizing nitrogeneous matter: mainly ammonium and nitrogen in biological materials.
- removing phosphate.
Aeration Methods
- Diffused Aeration
Sewage liquor is run into deep tanks with diffuser blocks attached to the floor. These are like the diffuser blocks used in tropical fish tanks but on a much larger scale. Air is pumped through the blocks and the curtain of bubbles formed both oxygenates the liquor and also provide the neces… - Surface aerators
Vertically mounted tubes of up to 1 m diameter extending from just above the base of a deep concrete tank to just below the surface of the sewage liquor. A typical shaft might be 10 m high. At the surface end the tube is formed into a cone with helical vanes attached to the inner surfac…
References
- Beychok, Milton R. (1967). Aqueous Wastes from Petroleum and Petrochemical Plants (1st ed.). John Wiley & Sons Ltd. LCCN 67019834. Code of Practice, Flows and Loads-2, British Water Review of UK and international standards British Standard BS 6297:1983 Tilbury construction Deep Shaft Process Technology Beychok, M.R. (1971). "Performance of surface-aerated basins"…
Further Reading
- IWA Task Group on Good Modelling Practice - Leiv Rieger, Sylvie Gillot, Guenter Langergraber, Takayuki Ohtsuki, Andy Shaw, Imre Takacs, Stefan Winkler (2012) Guidelines for Using Activated Sludge Models, IWA Publishing.