Activated Sludge Treatment
- Content: Activated Sludge Treatment
- Definition of Activated Sludge Treatment. Activated sludge treatment can define as the wastewater treatment plant, which eliminates the particulate matter like sand, unwanted inorganic and organic wastes and harmful microorganisms ...
- Variables used in the Activated Sludge Treatment. ...
- Important Notes. ...
Full Answer
What is the purpose of Return Activated Sludge?
May 15, 2018 · The activated sludge process is an integral process used to treat wastewater. Air or oxygen is blown into raw sewage. It is most effective for large volumes of water. Wastewater is mixed and aerated in a special tank. This step in the process occurs by pumping air or oxygen into the activated sludge tank or using surface aerators.
What is returned activated sludge?
Dec 15, 2021 · The waste activated sludge process is a kind of sewage treatment that blows oxygen (or air) into unsettled, raw sewage, which digests pollutants and organic content to keep the biological system in balance. This process is called aeration and takes place in an aeration tank. There are two types of aeration: pure oxygen aeration and surface aeration.
What is an activated sludge process?
The activated sludge process is one of the most commonly used for secondary wastewater treatment. As a suspended-growth biological treatment process, activated sludge utilizes a dense microbial culture in suspension to biodegrade organic material under aerobic conditions and form a biological floc for solid separation in the settling units.
How does activated sludge work?
Activated sludge is a biological process that utilizes microorganisms to convert organic and certain inorganic matter from wastewater into cell mass. The activated sludge is then separated from the liquid by clarification. The settled sludge is either returned (RAS) or wasted (WAS). Activated sludge is commonly used as a wastewater treatment process
What is activated sludge process in wastewater treatment?
The activated sludge process in the treatment of wastewater involves blowing oxygen or air into raw, unsettled sewage. This process smashes the solids. The sewage is bubbled, and sewage liquor is discharged into an activated sludge chamber.May 15, 2018
What is activated sludge?
The activated sludge is a process with high concentration of microorganisms, basically bacteria, protozoa and fungi, which are present as loose clumped mass of fine particles that are kept in suspension by stirring, with the aim of removing organic matter from wastewater.
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.
What is activated sludge How is it produced?
(a) As the BOD of sewage or waste water is reduced to about 10-15%, the effluent is passed into a settling tank where the bacterial flocs undergo sedimentation. The sediment is called activated sludge.Jun 24, 2014
What is the difference between sludge and activated sludge?
This sediment is called activated sludge....Primary sludgeActivated sludge(iii)It does not require aerationFormation of activated sludge requires aeration(iv)A lot of decomposition occurs during the formation of primary sludgeVery little decomposition occurs during the formation of activated sludge2 more rows
What happens to the activated sludge?
The organic matter, from the sludge is oxidized to carbon dioxide, water and ammonia. The ammonia is further converted to nitrates as the digestion process proceeds.
What are the advantages of activated sludge process?
Advantages of Activated Sludge ProcessLow installation cost.Good quality effluent.Low land requirement.Loss of head is small.Freedom from fly and odor nuisance high degree of treatment.
What is activated sludge?
The activated sludge is a process with high concentration of microorganisms, basically bacteria, protozoa and fungi, which are present as loose clumped mass of fine particles that are kept in suspension by stirring, with the aim of removing organic matter from wastewater. From: Resource-Efficient Technologies, 2016.
Why do activated sludge plants foam?
Foaming in activated sludge plants is caused by high SRTs, warm temperatures, low F:M ratios and high MLSS levels, as well as oil and grease and/or surfactants in the influent. Abundance of actinomycetes such as Nocardia or Microthrix are commonly related to foaming in activated sludge plants, and have been identified in a full-scale MBR plant subject to variable OLRs ( Smith, 2006 ). However, foam in MBR plants has been observed in the absence of actinomycetes. The degree of foaming is reported as being related to the protein EPS concentrations (Nakajima and Mishima, 2005). Foaming sludges also appear to yield lower membrane permeabilities ( Chang and Lee, 1998 ), attributed to the higher hydrophobicity of foaming activated sludge ( Section 2.3.6.4 ). Foaming thus provides an indication of sludge fouling propensity.
What is activated sludge?
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 is also known as waste activated biosolids or waste activated solids.
When was activated sludge first used?
The activated sludge process is designed to speed up the rate of decomposition of waste material in water and was first developed in 1914, according to the International Water Association.
What is a return sludge system?
The return sludge system includes pumps, a timer or variable speed drive, and a flow measurement device. An activated sludge system consists of the same components but in some cases, the waste activated sludge withdrawal is accomplished by adjusting valves on the return system.
What is activated sludge?
Activated Sludge Basics. The activated sludge process is a biological wastewater treatment process. This means that treatment occurs as pollutants are used as a food source by many different types of microorganisms.
What is complete mix activated sludge?
In an ideal complete-mix activated sludge plant, the contents of the tank are completely mixed (the MLSS are uniformly mixed throughout the entire aeration tank). To ensure that this is achieved, special arrangements are often employed to uniformly distribute the influent and withdraw the effluent from the aeration tank. Attention to the tank shape and to intensive mixing is important. There are some means that the operator may use to evaluate the degree to which a particular process operates in the complete-mix mode. First and foremost, the entire contents of the tank should be as uniform as possible. This can be confirmed by measurements of DO and suspended solids. If the tank is thoroughly mixed, these measurements should be nearly uniform. The settleability of the complete-mix sludges is generally well within the accepted range of normal operation. The MLSS in the aeration tank ranges from 2,000 to 5,000 mg/L.
Why does my clarifier have floating solids?
Floating solids on the clarifier surface are an indication of a problem called "rising sludge". This problem occurs whenthe DO concentration in the secondary clarifier drops resulting in an anoxic, or oxygen deficient, condition. Under anoxic conditions, nitrifying bacteria convert nitrate to nitrogen gas. The nitrogen gas bubbles adhere to floc particles, causing them to rise up to the surface.
Why is my activated sludge bulking?
If your activated sludge process is experiencing sludge bulking problems, it may be due to filamentous microorganisms. If you suspect this is the problem, you can look at a sample of your sludge under a microscope. Healthy sludge has filaments in it. Just because your sludge contains filaments does not mean that your bulking problem is being caused by them. Bulking sludge is identified as a sludge that does settle but compacts very slowly. This may be caused by an excessive number of filamentous microbes. The key word is "excessive". In healthy sludge, the filaments act as a framework for the flocs. Filaments can serve to catch and hold small particles, acting somewhat like a net. This will in turn reduce effluent turbidity. In fact, if there are not enough filaments, the flocs may lack the necessary framework to form properly. This may result in pin floc. However, if too many filaments are in the sludge, the framework serves to prevent the sludge from compacting. Sludge bulking has been reported to be the most common operational problem affecting over half of the activated sludge facilities in the U.S.
What are the steps of B iological wastewater treatment?
B iological wastewater treatment is often described as occurring in three steps. In step one, transfer, food from the wastewater is transferred to the bacterial cell. Adequate mixing and detention time are needed to assure that the organism comes into contact with the food source.
How to determine detention time in clarifier?
Final Clarifier Detention Time - The detention time in the final clarifier (in units of hours) is determined by dividing the volume of the final clarifier by the flow to the clarifier. (Return sludge flow is generally not included in the calculation.)
What is flocculation in wastewater treatment?
In the third step of treatment, flocculation and separation, the microorganisms stick together to form large particles that will settle out of the purified wastewater in the secondary clarifier. Flocculation occurs when mixing allows the organisms to contact one another, but does not cause conditions so turbulent that the flocculated material is torn apart. Settleability and compaction of the floc particles depends on the density, size and shape of the particles as well as the efficiency of the clarifier. Settleability is affected by the abundance of filamentous bacteria, thos that form strings as they grow rather than forming floc. An excessive growth rate of these bacteria may cause a bulking condition in which the mixed liquor does not compact well, taking up much more volume in the clarifier. This condition may be caused by many factors, among which are improper Dissolved Oxygen environment and nutrient imbalance, and may result in solids loss in the clarifier effluent.
