Secondary wastewater treatment
- 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 BOD 5 (five ...
- Activated sludge. ...
- Trickling filter. ...
- Oxidation ponds. ...
What is the secondary treatment of waste water?
Read this article to learn about the secondary treatment of waste water. The secondary treatment is also known as biological treatment. It is capable of abating biodegradable dissolved and/or suspended organic substances. By secondary treatment it is also possible to remove dissolved nitrogenous and phosphorous compounds from a waste water stream.
What is the process of wastewater treatment?
The water is transported to local wastewater treatment facilities and undergoes a series of treatments in order to remove pollutants that would otherwise pollute the environment. Secondary treatment of sewage and other wastewater is the stage of wastewater treatment designed to substantially degrade the biological content of the sewage.
What happens to the water after the secondary treatment 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 are the different types of wastewater treatment?
1 Primary Wastewater Treatment. Primary treatment of wastewater involves sedimentation of solid waste within the water. ... 2 Secondary Wastewater Treatment. Secondary treatment of wastewater makes use of oxidation to further purify wastewater. ... 3 Tertiary Wastewater Treatment. ...
What is removed in 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 is removed from waste water at water treatment plants?
The major aim of wastewater treatment is to remove as much of the suspended solids as possible before the remaining water, called effluent, is discharged back to the environment. As solid material decays, it uses up oxygen, which is needed by the plants and animals living in the water.
What is secondary treatment of 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 Cannot be removed from waste water?
Biological stages in wastewater treatment plants are not able to remove substances such as drugs, found in the wastewater of medical centers, or halogenated compounds and cyanides from industrial wastewater.
Aerobic Processes
Aerobic secondary treatment of wastewater occurs when various types of electron acceptors are present in the medium then the bacterial cells will utilize the one that produces the highest quantity of energy. Thus aerobic processes will utilize oxygen first.
Anoxic Processes
If the nitrates are present then the microorganisms which are capable of utilizing nitrogen will prevail. during respiration, they will convert nitrate to nitrogen gas (Denitrification) and the processes are collectively called anoxic processes.
Anaerobic Processes
When nitrates are consumed then anaerobic processes start to prevail and other nutrients such as sulfates are utilized. During this process, the sulfates will be converted to sulfites and Carbon-d i-oxide to methane.
Suspended Growth Process
In this growth process, the microorganism which is responsible for the conversion of waste organic matter is maintained into suspension of the liquid phase. Aerobic suspended growth processes include Activated Sludge Processes, Aerated Lagoons, and Sequential Batch Reactors.
Attached Growth Processes
In attached growth processes the microorganisms are attached to the surfaces (such as stones, inert materials) or are self immobilized on flocs or granules in the system. Aerobic Attached Growth Processes include Trickling Filters, Roughing Filters, Rotating Biological Contractors, and Packed Bed Reactors.
Secondary Treatment Definition
Secondary treatment of wastewater is a process that follows the primary treatment of sewage.
Objectives of Secondary Treatment
The objectives of secondary treatment are to remove the remaining suspended solids, BOD, and COD from the wastewater. It is done to reduce the primary clarifier load and improve the quality of the effluent discharged from the treatment plant.
What are the Stages of Wastewater Treatment?
The stages of wastewater treatment are collection, pre-treatment, primary treatment, secondary treatment, tertiary treatment, disposal, and reuse.
What is The Secondary Treatment of Wastewater?
This article will tell you about the second stage in the wastewater treatment process.
How Does Secondary Treatment Work
Secondary treatment is treating wastewater in a municipal water system that removes most contaminants from wastewater by reducing their levels to acceptably low levels.
What are The Alternative Types of Secondary Biological Processes?
There are a few different types of alternative secondary biological processes, and these include aerobic and anaerobic processes.
Conclusion
The secondary wastewater treatment process is more complicated than the primary wastewater treatment process. It is necessary to remove the remaining pollutants from the wastewater. The method includes various other activities that can remove the remaining impurities.
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 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 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 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.
How is DO supplied in biological treatment?
In the biological treatment processes the DO is supplied either through natural means or by mechanical means by agitation. Anaerobic organisms can multiply in the absence of DO and do the decomposition, but the end products are undesirable fowl smelling gases like H 2 S, CH, etc.
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 material removed from wastewater?
Organic material and nutrients are removed from wastewater flowing past attached growth also known as biofilm. Packing materials used in attached growth processes include rock, gravel, slag, sand, redwood and wide range of plastic and other synthetic materials.
What is the main objective of secondary treatment?
The main objective of secondary treatment: To remove most of the fine suspended and dissolved degradable organic matter that remains after primary treatment, so that the effluent may be rendered suitable for discharge. Conventional secondary treatment can reduce the BOD's to below 20mg/l and Suspended Solids to below 30mg/l which is acceptable in ...
Is dissolved oxygen required in wastewater?
Are those where sufficed amount of dissolved oxygen is required into the wastewater to sustain aerobic action, as one of the major polluting effects of wastewater on streams results form the depletion of dissolved oxygen by the action of aerobic organisms in degrading the organic content of the waste. Practical aerobic biological treatment ...
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.
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 ...
Why is secondary treatment important?
Secondary treatment of sewage and other wastewater is the stage of wastewater treatment designed to substantially degrade the biological content of the sewage.
What is suspended process?
Suspended processes, particularly activated sludge, are most common in medium to large-scale plants; fixed film methods such as roughing filters need less maintenance and control, and are more resilient, and are appropriate where cost and maintenance are major issues. Anaerobic treatment is sometimes used, in the form of septic tanks ...
What is waste water treatment?
For waste water treatment almost always a microbial community having various species of organisms finds its way into a treatment unit. These organisms may enter a treatment unit from the surrounding environment as well as along with the waste water itself. Very often a portion of the biomass (microbes) produced during waste water treatment is recycled to the treatment unit. For abatement of a specified pollutant sometimes some specific organisms are added.
When to add nitrogen bearing compounds to wastewater treatment unit?
For synthesis of proteins and nucleic acids nitrogen bearing compounds are to be added to a wastewater treatment unit if those are not present as a constituent of the pollutants present.
When species present in an ecosystem do not use the same substrate (food) their environmental requirement is different?
When the species present in an ecosystem do not use the same substrate (food) their environmental requirement is different and they do not utilize the metabolic products and by-products of one another then there interaction is said to be neutral. In a community of micro-organisms in any ecosystem such an interaction is very rare.
What is the most effective method of secondary treatment of wastewater?
This method of secondary treatment of wastewater employs sand filters, contact filters, or trickling filters to ensure that additional sediment is removed from wastewater. Of the three filters, trickling filters are typically the most effective for small-batch wastewater treatment.
What is primary treatment of wastewater?
Primary treatment of wastewater involves sedimentation of solid waste within the water. This is done after filtering out larger contaminants within the water. Wastewater is passed through several tanks and filters that separate water from contaminants.
What is the third step in wastewater management?
This third and last step in the basic wastewater management system is mostly comprised of removing phosphates and nitrates from the water supply. Substances like activates carbon and sand are among the most commonly used materials that assist in this process.
How long does it take for a wastewater solution to be aerated?
The resulting mixture is then aerated for up to 30 hours at a time to ensure results.
How is wastewater treated?
The primary treatment of wastewater occurs through sedimentation with filtering out large contaminant particles within the liquid. The contaminants separate as they are passed through several tanks and other filters. Leftover sludge filters through a digester to suspend solids from the wastewater.
What is primary wastewater treatment?
The primary wastewater process utilizes equipment to break up larger particles and then uses sedimentation or a floating process for extraction. Many treatments that use the primary method then proceed to the secondary treatment process.
How to get rid of sediment in sewage?
The first is biofiltration that uses filters with sand, contact filters or trickling filters that remove sediment from the sewage. Aeration is the next step. It mixes the wastewater with a microorganism solution. Then, this treatment uses an oxidation pond to pass the wastewater through a body for up to two or three weeks.
What is the process of removing impurities from water?
The removal in the secondary wastewater treatment process generally occurs through a biological process with consumption of impurities in water by microbes, converting the matter into energy, carbon dioxide gases, and water. AOS can help with municipal wastewater treatment services in both primary and secondary processes.
What is primary treatment?
Through the primary treatment, it is possible to remove materials that float and settle on top of water. Through primary treatment, it is possible to implement screening water treatment, reduce particles to fragments, remove grit and initiate sedimentation. The primary treatment pushes sewage through screens into the comminutor for grip disposal ...
What is the difference between primary and secondary treatment?
The principal difference in primary and secondary treatment is the process that breaks down the sewage in wastewater. In the primary method, the waste processes through a physical procedure with equipment and filtration. While secondary treatment may use similar items, this method uses biological treatment through microbes.
What is the difference between filtration and sedimentation?
Another difference between these processes is how much time they take to complete.