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 wastewater treatment process?
This process is composed of biological treatments that make use of various microorganisms within a strictly controlled environment. In this stage of wastewater treatment, combined microorganisms make use of dissolved organics and colloidal that is found from the effluent of the initial treatment as their major food supply.
What is the EPA definition of secondary treatment?
The United States Environmental Protection Agency (EPA) defined secondary treatment based on the performance observed at late 20th-century bioreactors treating typical United States municipal sewage. Secondary treated sewage is expected to produce effluent with a monthly average of less than 30 mg/l BOD and less than 30 mg/l suspended solids.
What is Stage 2 of the wastewater treatment process?
STAGE TWO: PRIMARY TREATMENT It involves the separation of solid, organic matter (or human waste) from the wastewater. It is done by putting the wastewater into large settlement tanks for the solids to sink to the bottom. The settled solids are called sludge.
What is secondary treatment in wastewater?
Secondary treatment involves the removal of biodegradable organic matter (BOD) and suspended solids (TSS) through the processes of aeration and filtration. Secondary treatment is typically characterized as producing a treated wastewater effluent with a BOD of 25 mg/L or less and TSS of 30 mg/L or less.
What is 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 the secondary treatment for water pollution?
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 is secondary waste?
Secondary waste is waste generated from different sources and of different nature, i.e. waste generated in a process that is known as a waste treatment operation; it includes residual materials originating from recovery and disposal operations, such as incineration and composting residues.
What is primary and secondary treatment?
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 happens in the secondary stage of wastewater treatment class 7?
Secondary treatment is a biological process. The screened water is passed on to sedimentation tanks to obtain clarified water. The water is passed on to aeration tanks to speed up the process of treatment of water by blowing air through it. Biogas is obtained at this stage.
What is the main goal of 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.
What is secondary sewage treatment class 12?
Secondary treatment removes the dissolved organic matter by the use of biological agents and hence, known as biological treatment. This is achieved by microbes which can consume and degrade the organic matter converting it to carbon dioxide, water, and energy for their own growth and reproduction.
What is primary secondary and tertiary water treatment?
Wastewater is treated in 3 phases: primary (solid removal), secondary (bacterial decomposition), and tertiary (extra filtration).
What are primary and secondary waste?
There are two basic stages in the treat- ment of wastes, primary and secondary, which are outlined here. 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.
What steps are taken during secondary treatment of waste water?
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 steps are taken during secondary treatment of wastewater?
Secondary Wastewater Treatment TREATMENTActivated Sludge Process (ASP) / Extended Aeration System (EAS)Sequential Batch Reactor (SBR)Moving Bed Bio Film Reactor (MBBR)Membrane Bioreactor (MBR)
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 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 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 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 ...
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.
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 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.
What is 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.
Is wastewater a solid?
Total solids in wastewater can be categorized as inorganic and organic. When it comes to the size, it can be divided into suspended, colloidal and dissolved solids. The main purpose of the initial or primary treatment is to eliminate the suspended solids as much as possible.
What is primary treatment of sewage?
Primary treatment of sewage by quiescent settling allows separation of floating material and heavy solids from liquid waste. The remaining liquid usually contains less than half of the original solids content and approximately two-thirds of the BOD in the form of colloids and dissolved organic compounds.
What is secondary treatment?
Secondary treatment is designed to substantially degrade the biological content of the sewage which are derived from human waste, food waste, soaps and detergent. The majority of municipal plants use aerobic biological processes as a secondary treatment step. To be effective, the biota require both oxygen and food to live.
How much BOD is in secondary treated sewage?
Secondary treated sewage is expected to produce effluent with a monthly average of less than 30 mg/l BOD and less than 30 mg/l suspended solids. Weekly averages may be up to 50 percent higher.
How is primary clarifier effluent discharged?
Primary clarifier effluent was discharged directly to eutrophic natural wetlands for decades before environmental regulations discouraged the practice. Where adequate land is available, stabilization ponds with constructed wetland ecosystems can be built to perform secondary treatment separated from the natural wetlands receiving secondary treated sewage. Constructed wetlands resemble fixed-film systems more than suspended growth systems, because natural mixing is minimal. Constructed wetland design uses plug flow assumptions to compute the residence time required for treatment. Patterns of vegetation growth and solids deposition in wetland ecosystems, however, can create preferential flow pathways which may reduce average residence time. Measurement of wetland treatment efficiency is complicated because most traditional water quality measurements cannot differentiate between sewage pollutants and biological productivity of the wetland. Demonstration of treatment efficiency may require more expensive analyses.
What happens when biocide concentrations exceed the secondary treatment?
BOD reduction normally accomplished by that species temporarily ceases until other species reach a suitable population to utilize that food source, or the original population recovers as biocide concentrations decline.
What is a cyclic activated sludge system?
One type of system that combines secondary treatment and settlement is the cyclic activated sludge (CASSBR), or sequencing batch reactor (SBR). Typically, activated sludge is mixed with raw incoming sewage, and then mixed and aerated. The settled sludge is run off and re-aerated before a proportion is returned to the headworks.
What is wastewater treatment?
Wastewater treatment is the process of converting wastewater into water that can be discharged back into the environment. According to the U.S. EPA, one of the most common forms of pollution control in the U.S. is wastewater treatment. The purpose of wastewater treatment is to speed up the natural processes by which water is purified.
What is the primary stage of wastewater treatment?
In the primary stage, solids are allowed to settle and be removed from wastewater. The secondary stage uses biological processes to further purify wastewater. Sometimes these stages are combined, and in some cases additional treatment such as tertiary treatment and advanced wastewater treatment are used.
What is activated sludge?
People tend to use the activated sludge process instead of trickling filters, since the activated sludge process speeds up the work of the bacteria. After the sewage leaves the settling tank in the primary stage, it is pumped into an aeration tank.
How is wastewater formed?
Wastewater is formed by a number of activities such as bathing, washing, using the toilet, and rainwater runoff. Wastewater is essentially used water that has been affected by domestic, industrial and commercial use. Some wastewaters are more difficult to treat than others, according to the Safe Drinking Water Foundation.
What is the process of removing chlorine from sedimentation tanks?
Many states now also require the removal of excess chlorine before discharge to surface waters by a process called dechlorination, according to the EPA.
What is primary treatment?
Primary Treatment. Primary treatment removes material that will either float or readily settle out by gravity. This treatment includes the physical processes of screening, comminution—the act of reducing a material to minute particles or fragments—grit removal and sedimentation. As wastewater enters a plant for treatment, it flows through a screen.
What happens if wastewater is not treated?
If wastewater is not properly treated, then the environment and human health can be negatively impacted, reported the United States Geological Survey (USGS). Among the impacts are harm to fish and wildlife populations, oxygen depletion, beach closures and other restrictions on recreational water use. Advertisement.
How is wastewater treated?
It is done by putting the wastewater into large settlement tanks for the solids to sink to the bottom. The settled solids are called sludge. At the bottom of these circular tanks, large scrappers continuously scrape the floor of the tank and push the sludge towards the center, where it is pumped away for further treatment. The rest of the water is moved to Secondary treatment.
What is the first stage of wastewater treatment?
Screening is the first stage of the wastewater treatment process. Screening removes large objects like diapers, nappies, sanitary items, cotton buds, face wipes, and even broken bottles, bottle tops, plastics, and rags that may block or damage equipment.
Where does liquid waste go?
Wastewater (liquid waste) from flushing the toilet, bathing, washing sinks, and general cleaning goes down the drain and into a pipe, which joins a larger sewer pipe under the road. The sewer pipe goes on to connect to a different sewer pipe that leads to the treatment center.
Why is air pumped into sludge scraping water?
These are called aeration lanes. Air is pumped into the water to encourage bacteria to break down the tiny bits of sludge that escaped the sludge scraping process.
What is non-sewage?
Non-sewage comprises mainly storm or surface runoff water. Surface runoff occurs by precipitation that flows to a defined channel. They carry harmful elements and chemicals that form in the atmosphere which gets dissolved in soil and vegetation. They flow to a channel while carrying such harmful substances.
Why is wastewater important?
Wastewater comprises various chemical compositions and it’s important to have an understanding of how the interactions and reactions occur in the organic and inorganic compounds. The biological and organic compounds in wastewater are the result of influent water usage in industrial, agricultural, and domestic activities. After the wastewater is treated, it is disposed of to the main channel stream and is then reused by the public. However, bacteriological, and chemical composition must be monitored as it goes for public usage. To protect users downstream, microbiological, and other releases of pollutants must be minimized.
How does wastewater affect the environment?
Human wastes and other industrial activities contribute to the formation of wastewater. When these wastes reach the main river body streams, it contaminates the river and leads to environmental pollution. Such wastes must be contained before they make their way to the river streams. This leads to the development of wastewater treatment plants.
What is the inorganic load of water?
The inorganic load is formed by the disposal of both treated and untreated wastewater, and impurities left after the process of evaporation. Large quantities of these organic matters are added in both natural and wastewaters as the result of human use. They usually contain pH, alkalinity, chlorides, nitrogen, sulfur, and heavy metals.
What are the pathogens in water?
Pathogens can be viruses, bacteria, or protozoa. Bacteria is normally present in water but if the level increases above safety level, then contamination of water occurs. Microorganisms that are found in water are Salmonella, Norovirus, E. coli, and so on. These are considered to cause widespread diseases. Increased pathogens are the result of inadequate sewage disposal or from on-site sanitation.
Is wastewater a solid?
Wastewater contains organic and inorganic nutrients and suspended solids. These suspended elements are the leading cause of water pollution and should undergo treatment procedures for public use. However, balancing the number of nutrients is the key to effective wastewater treatment. Macronutrients such as phosphorus and nitrogen promote biological health and development. But these nutrients come into imbalance due to excessive wastewater constituents. These excessive nutrients have to be taken out else it causes harm to the water bodies it discharges into.
