Wastewater
Wastewater, also written as waste water, is any water that has been adversely affected in quality by anthropogenic influence. Wastewater can originate from a combination of domestic, industrial, commercial or agricultural activities, surface runoff or stormwater, and from sewer inf…
What are the three stages of wastewater 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 primary treatment of wastewater?
Oct 16, 2009 · 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 secondary waste treatment?
Secondary wastewater treatment may be accomplished by biological or chemical -physical methods. Activated sludge and trickling filters are two of the most common means of secondary treatment. It is accomplished by bringing together waste, bacteria, and oxygen in trickling filters or in the activated sludge process. ...
What is secondary water treatment?
Mar 23, 2017 · 1. Objectives of Secondary Treatment of waste water Main objective 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.
What is the purpose of secondary treatment in wastewater?
The objective of secondary treatment is the further treatment of the effluent from primary treatment to remove the residual organics and suspended solids.
What does secondary treatment target?
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 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.
What is a secondary treatment system?
Secondary treatment systems(STS) are wastewater treatment systems which produce treated effluent of secondary standard, i.e. 20 mg/L of Biochemical Oxygen Demand (BOD), 30 mg/L of Total suspended solids (TSS) and 10 cfu/100 mL of Escherichia (E) coli.Dec 7, 2021
What is the purpose of secondary clarifiers?
secondary clarifiers is to separate biological floc from the treated liquid waste stream. Secondary clarifiers are most often discussed in conjunction with suspended growth biological wastewater treatment systems.
Why is secondary treatment often needed for sewage quizlet?
removes dissolved and suspended biological matter. Secondary treatment is typically performed by indigenous, water-borne micro-organisms in a managed habitat. Secondary treatment may require a separation process to remove the micro-organisms from the treated water prior to discharge or tertiary treatment.
Which of the following occurs during the secondary treatment of wastewater quizlet?
The secondary treatment of the liquid portion of wastewater involves all anaerobic respiration, thus the water is stirred or kept shallow to get rid of the oxygen. Wastewater treatment is entirely a chemical process not involving microbes.
What is the purpose of aeration in wastewater treatment quizlet?
-Simple mechanical aeration devices either splash water into the air or entrain (mix) air into the wastewater so that oxygen can be absorbed into the water.
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 is the only thing to be provided for the respiration of aerobic organisms?
The organic solids present in the wastewater serve as food for the aerobic microorganisms. The only thing to be provided is the DO , which is essential for the respiration of the aerobic organisms.
What is suspended growth?
In suspended growth systems the microorganisms responsible for treatment are maintained in liquid suspension by appropriate mixing methods. Typically, suspended growth systems require smaller footprints than fixed film systems for an equivalent capacity. There are a number of biological processes. The most common is activated sludge process in which microbes, also known as biomass, are allowed to feed on organic matter in the wastewater and remain in suspension. The make-up and dynamics of the microbial population is a function of how the ASP is operated.
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 do aerobic bacteria use for respiration?
Aerobic bacteria use dissolved oxygen (DO) from the water bodies for their respiration. They oxidize organic matter under aerobic conditions. The end products of the decomposition are water, CO 2 and Cell tissues. Anaerobic bacteria use oxygen derived from chemical substances for their respiration.
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 the oxidation of ammonia to nitrate?
This is achieved by oxidation of most of the ammonia to nitrate during treatment (nitrification ). 2. Nitrification: Means the oxidation of ammonia to nitrate. Nitrification is possible with aerobic biological processes.
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.
When was the tricking filter invented?
The first tricking filter was placed in operation in England in 1893. the concept of a tricking filter was grew form the of contact frets which were water tight basins filled with broken stones. The limitation the contact filters included a relatively.
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 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.
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.
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 happens during the amphibolic and anaplerotic cycle?
During this process the intermediates produced by the amphibolic route and the anaplerotic route are subsequently polymerized and finally the different components of the cells are produced. Ultimately it leads to the production of new cells. It should be mentioned here that all of the activities (chemical reactions) occurring inside a cell are enzyme (complex proteinacious compounds) catalyzed.
What are the two stages of catabolic activity?
Generally catabolic activities are carried out in two stages. In the first stage the suspended organic matter present in waste water are solubilized and the larger dissolved organic molecules are hydrolyzed (spitted) into smaller molecules. Extra-cellular enzymes take part in these reactions. The relatively small amount of energy liberated during this step is not available to the cells (microbes) as the reactions occur outside the cells. .
What are the elements in a microbe cell?
Microbial cells contain about 80 per cent water. The remaining portion is made up of C, O 2, H 2, N 2, P and S. Metals like Na, K, Ca, Mg, Fe are also present in microbial cells. The C, O 2, H 2 and N 2 constituents of a cell are often approximated (on ash-free basis) by the formula C 5 H 7 O 2 N. For synthesis (reproduction) of new microbes other than H 2 and O 2 (which may be obtained from water) the major elements required are C and N 2.
How are prokaryotes bounded?
Prokaryotes are unicellular and usually are smaller than 5 μm in diameter. They have very simple structure and are bounded by a membrane. Most of them have rigid cell walls. Inside a cell there is a nucleus and cytoplasm. The nucleus is not separated from cytoplasm by a membrane. The enzymes which take part in respiration and photosynthetic reactions are located in the cell membrane or in its folding. Prokaryotes are not phagotropic, i.e., they cannot intake food.
What is the term for an interaction between organisms that helps another organism?
Such an interaction between the organisms is referred to as benevolent interaction.
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.
What are the three groups of bacteria?
Bacteria are unicellular. Their size ranges between 0.2 to 2 µm. They are classified into three groups: myxobacteria, spirochetes and eubacteria. Depending on their shape they are termed as cocci (spherical), bacilli (rod like), and spirilla (spirals).
What is an MBR system?
Membrane bioreactors (MBR) are activated sludge systems using a membrane liquid-solid phase separation process. The membrane component uses low pressure microfiltration or ultrafiltration membranes and eliminates the need for a secondary clarifier or filtration. The membranes are typically immersed in the aeration tank; however, some applications utilize a separate membrane tank. One of the key benefits of an MBR system is that it effectively overcomes the limitations associated with poor settling of sludge in conventional activated sludge (CAS) processes. The technology permits bioreactor operation with considerably higher mixed liquor suspended solids (MLSS) concentration than CAS systems, which are limited by sludge settling. The process is typically operated at MLSS in the range of 8,000–12,000 mg/L, while CAS are operated in the range of 2,000–3,000 mg/L. The elevated biomass concentration in the MBR process allows for very effective removal of both soluble and particulate biodegradable materials at higher loading rates. Thus increased sludge retention times, usually exceeding 15 days, ensure complete nitrification even in extremely cold weather.
How does an aerated lagoon work?
Aerated lagoons are a low technology suspended-growth method of secondary treatment using motor-driven aerators floating on the water surface to increase atmospheric oxygen transfer to the lagoon and to mix the lagoon contents. The floating surface aerators are typically rated to deliver the amount of air equivalent to 1.8 to 2.7 kg O 2 / kW·h. Aerated lagoons provide less effective mixing than conventional activated sludge systems and do not achieve the same performance level. The basins may range in depth from 1.5 to 5.0 metres. Surface-aerated basins achieve 80 to 90 percent removal of BOD with retention times of 1 to 10 days. Many small municipal sewage systems in the United States (1 million gal./day or less) use aerated lagoons.
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.
What is the advantage of MBR?
One of the key benefits of an MBR system is that it effectively overcomes the limitations associated with poor settling of sludge in conventional activated sludge (CAS) processes.
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 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 process upset?
Process upsets are temporary decreases in treatment plant performance caused by significant population change within the secondary treatment ecosystem. Conditions likely to create upsets include for example toxic chemicals and unusually high or low concentrations of organic waste BOD providing food for the bioreactor ecosystem.