During secondary treatment, water flows through a secondary sedimentation tank that allows both solid wastes and microorganisms to form clumps and settle out of the water that is being treated. This step in the process of wastewater treatment uses various types of bacteria to treat water.
What is the second stage of wastewater treatment?
Secondary Wastewater Treatment TREATMENT Secondary Wastewater treatment is the second stage of wastewater treatment. In primary treatment, suspended solids, colloidal particles, oil, and grease are removed. In secondary treatment, biological treatment is done on the wastewater to remove the organic matter present.
What is the difference between primary and secondary wastewater treatment?
During secondary treatment, water flows through a secondary sedimentation tank that allows both solid wastes and microorganisms to form clumps and settle out of the water that is being treated. This step in the process of wastewater treatment uses various types of …
What is the process of wastewater treatment?
Dec 27, 2020 · Secondary treatment of wastewater makes use of oxidation to further purify wastewater. This can be done in one of three ways: This method of secondary treatment of wastewater employs sand filters, contact filters, or trickling filters to ensure that additional sediment is removed from wastewater.
What happens to the water after the secondary treatment process?
SECONDARY TREATMENT Purpose: •The main purpose of secondary treatment is to remove BOD which does not benefit as much as SS from primary settling. •It is a process which is capable of biodegrading the organic matter into non-polluting end products ,e.g. Water,CO 2 and biomass. 3
What is secondary treatment of waste water?
Secondary treatment is the removal of biodegradable organic matter (in solution or suspension) from sewage or similar kinds of wastewater. The aim is to achieve a certain degree of effluent quality in a sewage treatment plant suitable for the intended disposal or reuse option.
What happens during the step of secondary wastewater treatment?
During secondary treatment, water flows through a secondary sedimentation tank that allows both solid wastes and microorganisms to form clumps and settle out of the water that is being treated. This step in the process of wastewater treatment uses various types of bacteria to treat water.Sep 30, 2014
What is the process of secondary treatment?
Secondary treatment is a step in wastewater treatment that involves the use of biological processes in order to capture all the dissolved organic materials that were not caught during the initial treatment. Microbes take these organic substances as food, transforming them to water, energy and carbon dioxide.Oct 29, 2017
What happens in secondary clarifier wastewater treatment?
The Secondary Clarifier Process The biomass of microorganisms settles to the bottom in the form of activated sludge. After settling over a period of time, this biomass of microorganisms is returned to the first aeration tank. This cycle repeats until only clean water is left.Feb 15, 2021
What steps are taken during secondary treatment of waste water Why secondary treatment is called biological treatment?
Secondary treatment of wastewater works on a deeper level than primary level. It is called as biological treatment because it is designed to substantially degrade the biological content of the waste through aerobic biological processes. This step removes the dissolved organic matter by the use of biological agents.
What are the 5 steps of wastewater treatment?
Treatment StepsStep 1: Screening and Pumping. ... Step 2: Grit Removal. ... Step 3: Primary Settling. ... Step 4: Aeration / Activated Sludge. ... Step 5: Secondary Settling. ... Step 8: Oxygen Uptake. ... Sludge Treatment.
What are the major objectives of the secondary wastewater treatment?
The objective of secondary treatment is the further treatment of the effluent from primary treatment to remove the residual organics and suspended solids.
Why are secondary clarifiers needed?
Secondary clarifiers are used to remove the settlable suspended solids created in biological treatment processes such as the activated sludge and trickling filter process.Jul 5, 2007
How do secondary clarifiers work?
The clarifier works by permitting the heavier and larger particles to settle to the bottom of the clarifier. The particles then form a bottom layer of sludge requiring regular removal and disposal. Clarified water then proceeds through several more steps before being sent for storage and use.
What is the difference between primary and secondary sludge?
Primary sludge is generated from chemical precipitation, sedimentation, and other primary processes, whereas secondary sludge is the activated waste biomass resulting from biological treatments. Some sewage plants also receive septage or septic tank solids from household on-site wastewater treatment systems.
What does secondary wastewater treatment remove?
S econdary wastewater treatment processes use microorganisms to biologically remove contaminants from wastewater. In an aerobic system, the organic contaminants are converted to carbon dioxide, water, additional microorganisms, and other end products.
Which impurities are removed from sewage 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…
Which wastes are removed by primary and secondary wastewater treatment?
Wastewater treatment is usually broken down into two sections: primary treatment, which removes grease, dirt, gravel, and floatable waste, and secondary treatment, which removes even more suspended solids and pollutants by using biological processes.
What is removed during the purification of wastewater?
Carbon filtering removes remaining contaminants and impurities by chemical absorption onto activated carbon. Filtration through sand (calcium carbonate) or fabric filters is the most common method used in municipal wastewater treatment.
What is primary and secondary wastewater treatment?
The basic function of wastewater treatment is to speed up the natural processes by which water is purified. In the primary stage, solids are allowed to settle and removed from wastewater. The secondary stage uses biological processes to further purify wastewater. Sometimes, these stages are combined into one operation.
Which is a secondary treatment?
Secondary treatment is a treatment process for wastewater (for example for sewage but also for some types of industrial wastewaters) to achieve a certain degree of effluent quality by using a sewage treatment plant with physical phase separation to remove settleable solids and a biological process to remove dissolved …
How are secondary treatment methods used in wastewater treatment?
Secondary Wastewater Treatment. Secondary treatment of wastewater makes use of oxidation to further purify wastewater. This can be done in one of three ways: This method of secondary treatment of wastewater employs sand filters, contact filters, or trickling filters to ensure that additional sediment is removed from wastewater.
What is secondary treatment in wastewater?
Once wastewater has gone through the Primary treatment stage the Effluent will undergo a secondary treatment in order to remove both small suspended solids and BOD 5 (five day biochemical oxygen demand [2]) that pass through the primary treatment stage. All secondary treatment systems use a biological process to break down organic matter. Microorganisms are introduced to the wastewater and consume the organic matter, oxygen is delivered to the system ensuring microorganism survival. Oxygen delivery differs among the various systems. This biological process occurs naturally in nature, but is accelerated in secondary treatment systems. Typically 85% of BOD and suspended solids are removed during this process. Water exiting secondary treatment will still carry nitrogen, phosphorus, heavy metals, Pathogens, and bacteria. For further removal of pollutants the water is transported to a tertiary treatment [3] system and disinfection. There are a variety of secondary treatment processes; the following are conventional processes used by treatment plants:
What is secondary effluent?
The secondary effluent that settles will either enter a digester or re-enter the trickling system. Secondary effluent that re-enters the trickling filter serves several purposes, the following are examples; 1. further treatment, 2. preventing the microorganism from drying out, and 3. diluting or supplementing primary effluent.
What is the process of trickling filter?
Process: When primary effluent is transported to a trickling filter system the wastewater is dispensed upon a bed of media, such as rocks, stones, plastics, or salts. The most modern trickling filters use a type of rockwool. The effluent flows through the material at slow enough rates to allow microbial growth on the surface of the media (and within the fibres of the media, in the rockwool types) creating a layer of film. The spacing of the media allows air to circulate throughout the trickling system. Once microbial growth takes place additional wastewater flow has contact with microorganisms; this contact ensures that the organic matter in the primary treatment effluent is broken down. The biofilm that falls off the media flows through the bed of material and will be transported to the secondary settling tank to remove excess microorganisms. The secondary effluent that settles will either enter a digester or re-enter the trickling system. Secondary effluent that re-enters the trickling filter serves several purposes, the following are examples; 1. further treatment, 2. preventing the microorganism from drying out, and 3. diluting or supplementing primary effluent. Figure 2 provides a visual layout of a trickling filter system.
How does activated sludge work?
Process: During the activated sludge process primary effluent flows into an aeration tank, where it is mixed with microorganisms. The aeration tank injects a steady supply of oxygen or air into the wastewater, ensuring that the organisms have an adequate supply of oxygen needed to breakdown the organic matter that remains in the effluent. The effluent then flows into secondary settling tanks. At this point the sludge goes in one of two directions; 1. back to the aeration tank, this is because the return sludge contains a large amount of microorganisms that will rapidly breakdown organic matter, or 2. to the sludge digester [4]. The treated water will enter the tertiary treatment stage; here it will go through the final treatment stage before it is released into a natural water system. Figure 1 is an example an active sludge system.
How deep is an oxidation pond?
Process: Oxidation ponds are large and shallow; a typical depth would range from 1-2.5m. The ponds are composed of microorganisms, which feed on the organic matter received from primary effluent. Algae are a key feature in the oxidation pond system. Algae are much like the aeration tank in the activated sludge system; they deliver a steady flow of oxygen to the bacteria. The algae require sunlight to produce oxygen via photosynthesis, reaeration created by wind delivers air flow when sunlight is not available. Overall the process is slow and requires large areas of land. Typically oxidation ponds are used in areas with small populations where land is readily available. Figure 3 shows the basics of an oxidation pond system.
How do algae produce oxygen?
The algae require sunlight to produce oxygen via photosynthesis, reaeration created by wind delivers air flow when sunlight is not available.
What is anaerobic treatment?
Anaerobic treatment is sometimes used, in the form of septic tanks and in biogas digesters. in the case of septic tanks the primary and secondary phases are combined in one unit. If biogas digesters are used for secondary treatment, the primary treatment phase is reduced or emitted (aiming to remove matter such as gravel ...
What is secondary treatment?
The secondary treatment is designed to remove soluble organics from the wastewater. Secondary treatment consists of a biological process and secondary settling is designed to substantially degrade the biological content of the sewage such as are derived from human waste, food waste, soaps and detergent.
What is the purpose of sewage treatment?
The purpose of the sewage treatment is to remove the solids present in the sewage. ROLE OF MICROORGANISMS. Microorganisms are unicellular microscopic living things. They multiply by binary division of cells within 10 to 20 minutes. They require oxygen for their respiration.
What is activated sludge?
The activated sludge process (ASP) is an aerobic biological wastewater treatment process that uses microorganisms, including bacteria, fungi, and protozoa, to speed up decomposition of organic matter requiring oxygen for treatment.
What are the end products of anaerobic and aerobic processes?
Under aerobic conditions, if completely oxidized, organic matter is transformed into non-hazardous products. But an anaerobic process can produce methane (CH 4 ), which is explosive, and ammonia (NH 3) and hydrogen sulfide (H 2 S), which are toxic.
What are the two types of biological processes?
TYPES OF BIOLOGICAL PROCESSES. There are two types of biological treatment process; aerobic and anaerobic. Aerobic process means that oxygen is present for the microbes for respiration. Anaerobic process means that the process proceeds in the absence of DO.
What is the activity of the WSPs?
The activity in the WSPs is a complex symbiosis of bacteria and algae, which stabilizes the waste and reduces pathogens. The algae produce oxygen during photosynthesis by utilizing carbondioxide and solar energy derived from sun light.
What are the two types of solids in sewage?
SOLIDS IN SEWAGE. The solids present in the sewage are of two types viz., Organic solids, and. Inorganic solids. Organic solids are the substances derived from living things like produces from plant and animal. Examples of organic solids are carbohydrate, protein, and fat.
What is the purpose of secondary wastewater treatment quizlet?
The purpose of secondary treatment is to remove the suspended solids that did not settle out in the primary tanks and the dissolved BOD that is unaffected by physical treatment. It is called biological treatment because it involves the use of microbes.
What is the main purpose of secondary wastewater treatment?
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.
How long does it take to treat wastewater?
How long does it take to treat the wastewater? Approximately 24 hours. 9.
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.
What are the 5 stages of wastewater treatment?
Treatment Steps Step 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.
How is BOD removed from wastewater?
Some BOD is removed in the septic tank by anaerobic digestion and by solids which settle to the bottom of the septic tank, but much of the BOD present in sewage (especially detergents and oils) flows to the leaching field. The bacteria in a healthy biomat also digest most of the remaining BOD in the sewage.
What do percolation tests accomplish quizlet?
A percolation test (colloquially called a perc test) is a test to determine the water absorption rate of soil (that is, its capacity for percolation) in preparation for the building of a septic drain field (leach field) or infiltration basin. Climate directly and indirectly effects soil formation.
Brief History
Brief Explanation
- Once wastewater has gone through the Primary treatment stage the Effluent will undergo a secondary treatment in order to remove both small suspended solids and BOD5 (five day biochemical oxygen demand) that pass through the primary treatment stage. All secondary treatment systems use a biological process to break down organic matter. Microorganisms...
Activated Sludge
- Process:During the activated sludge process primary effluent flows into an aeration tank, where it is mixed with microorganisms. The aeration tank injects a steady supply of oxygen or air into the wastewater, ensuring that the organisms have an adequate supply of oxygen needed to breakdown the organic matter that remains in the effluent. The effluent then flows into secondar…
Trickling Filter
- Process:When primary effluent is transported to a trickling filter system the wastewater is dispensed upon a bed of media, such as rocks, stones, plastics, or salts. The most modern trickling filters use a type of rockwool. The effluent flows through the material at slow enough rates to allow microbial growth on the surface of the media (and within the fibres of the media, i…
Oxidation Ponds
- Process:Oxidation ponds are large and shallow; a typical depth would range from 1-2.5m. The ponds are composed of microorganisms, which feed on the organic matter received from primary effluent. Algae are a key feature in the oxidation pond system. Algae are much like the aeration tank in the activated sludge system; they deliver a steady flow of oxygen to the bacteria. The alg…
See Also
External Links
- Wikipedia:Sewage treatment#Secondary treatment
- Clean Water Act- US EPA
- -An Overview of Tertiary Treatment
- [https://www.daviddarling.info/encyclopedia/A/AE_anaerobic_digestion.html-Anaerobic Digestion