Full Answer
What is chlorine used for in wastewater treatment?
Chlorine and its various forms are powerful oxidants that will kill or inactivate most pathogenic organism that are harmful to human and animal life. Chlorination is the most commonly used disinfection process for wastewater treatment.
What is the recommended chlorine dosage for a wastewater treatment plant?
Problem 2.1: If the flow rate through a wastewater plant is 0.6 mgd and the desired chlorine dosage is 1.0 mg/l, determine the chlorinator setting in lbs/day. Using the Davidson Pie, the top portion is shaded because we are solving for feed rate. The remaining portions of the “pie” are multiplied together.
How is chlorine residue measured at wastewater treatment plants?
• Measurement of chlorine residual is accomplished at wastewater treatment plants by one of four methods: Iodometric, DPD Titrimetric, Amperometric Titration, or the ORP method. • Using the Davidson Pie formula, an operator can determine the setting of a chlorinator in lbs/day.
Why do wastewater treatment plants need to dechlorinate effluent after disinfection?
The effluent from a wastewater treatment plant may need to be dechlorinated after disinfection because of harmful affects the chlorine residual may have on fish, wildlife, and even human health. a. True b. False 2. Common methods of dechlorination include: a.
At which step in wastewater treatment is chlorine added?
The final step in the treatment process is disinfection using chlorine. The Chlorine Contact Basins are long, snake-like channels where chlorine is added to the flowing treated wastewater for disinfection. Disinfection is the process where disease-causing organisms (mostly bacteria) are killed by the chlorine.
Where is chlorine used in water treatment?
The most common use of chlorine in water treatment is to disinfect water. As a disinfectant, it has drawbacks, but it also has advantages. Other methods of disinfection such as ultraviolet and ozonation are effective disinfectants but they do not provide a residual to prevent pathogen regrowth as chlorination does.
What function does chlorine play in wastewater treatment?
Importantly, waste water treatment facilities use chlorine disinfectants to destroy oxygen-robbing contaminants in wastewater, helping to preserve the quality of our nation's rivers and streams into which the treated wastewater is discharged.
What are the 4 stages of wastewater treatment?
4-Step Wastewater Sludge Treatment ProcessStep 1 – Sludge Thickening. The first step in the sewage sludge treatment plan is called thickening. ... Step 2 – Sludge Digestion. After amassing all the solids from the sewage sludge begins the sludge digestion process. ... Step 3 – Dewatering. ... Step 4 – Disposal.
How much chlorine is used in wastewater treatment?
For most municipal and other wastewater systems, a chlorine dioxide residual concentration of up to 5 ppm is sufficient to provide adequate disinfection.
Which of the following is a step of wastewater treatment?
Aeration, coagulation, clariflocculation, filtration, chlorination and storage. Explanation: Aeration is the process in which Oxygen is added to water.
What are the 7 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 6: Filtration. ... Step 7: Disinfection. ... Step 8: Oxygen Uptake.
How is chlorine used?
Its most important use is as a bleach in the manufacture of paper and cloth, but it is also used to make pesticides (insect killers), rubber, and solvents. Chlorine is used in drinking water and swimming pool water to kill harmful bacteria.
What is the process of chlorination called as a treatment process and how does it differ from sterilization?
Answer: Chlorination is the process of sterilization of water by addition of chlorine acts as a treatment against bacterial infection. Chlorination is described as any reaction or process that incorporates chlorine into a molecule.
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. In some applications, more advanced treatment is required, known as quaternary water treatment.
What is the second stage of water treatment?
Secondary Treatment The secondary stage of treatment removes about 85 percent of the organic matter in sewage by making use of the bacteria in it. The principal secondary treatment techniques used in secondary treatment are the trickling filter and the activated sludge process.
What are the 3 steps for wastewater treatment?
The 3 Stages Of Wastewater TreatmentPrimary Treatment. Before wastewater even gets to primary treatment, it is funneled through collection systems and treated with odor-neutralizing chemicals. ... Secondary Treatment. In secondary treatment, the goal is to break down wastewater even further. ... Tertiary Treatment.
Dechlorination: Why It Matters
While chlorination is an effective technique that can be used for wastewater treatment, there are also times when dechlorination should be used. Nearly every wastewater treatment facility uses chlorination to disinfect wastewater before the water is sent back out into the environment.
The Disinfectant in Wastewater: Chlorine
Before you decide to use chlorine to disinfect wastewater, you should better understand the benefits that this treatment method offers. Along with removing any pathogens that can be found in the wastewater, chlorine is also able to:
Safe Handling and Using Chlorine
When you’re preparing to use chlorine for wastewater treatment purposes, it’s important that you understand how to safely handle and use this substance. You can use chlorine for wastewater disinfection as a chlorinated compound or elemental chlorine, the latter of which is in a gaseous state upon use.
Chlorine in Drinking Water
Chlorine is highly effective at treating drinking water and making sure that this water is perfectly safe to consume. Because of how effective chlorine is at getting rid of harmful pathogens in wastewater, chlorination has been the primary disinfection method used for drinking water treatment over the past century.
What is wastewater treatment
Treatment of wastewater is a major step in preventing the pollution of our freshwater resources. The process uses specialized machines to remove pollutants such as metals, debris, microorganisms, and biowaste from the water before it is returned to its source, be it surface water or groundwater.
There are four types of wastewater treatments
This treatment method involves the following steps: infiltration, grit removal, primary sedimentation tank, secondary sedimentation tank, and secondary clarification. This process is used to treat domestic wastewater and commercial waste.
Stages of wastewater treatment
Wastewater treatment is the process of cleaning wastewater before it is discharged back into waterways or utilized as a reclaimed water source. Here are the three stages that help us achieve that.
Why is chlorine used as a disinfectant?
Chlorine and pH. In general terms, the lower the pH of the water, the more effective chlorine is as a disinfectant. Again, speaking generally, a reason for dosing effectively is that chlorination raises the pH of water, so overdosing often raises the pH to levels where chlorine does not work effectively as a disinfectant.
How much chlorine is needed for disinfection?
Residual requirements vary, but typical residual goal would be for 0.2 to 1 mg/L. In addition to disinfection, chlorine can be effectively used to oxidize iron, manganese and hydrogen sulfide to facilitate their removal, to reduce color in water, and to aid in such treatment processes as sedimentation and filtration.
What is the best way to disinfect water?
Other methods of disinfection such as ultraviolet and ozonation are effective disinfectants but they do not provide a residual to prevent pathogen regrowth as chlorination does. When treatment plants are distant from the point of use, chlorination is the best way to provide safe water to the end user. Municipal water providers usually rely on measurements of “chlorine residual”—the amount of chlorine remaining in the water after it reaches its destination—as proof of safety. Residual requirements vary, but typical residual goal would be for 0.2 to 1 mg/L.
What is calcium hypochlorite?
Calcium hypochlorite is manufactured from chlorine gas. It is best known as chlorine pellets and granules in residential water treatment. It is a white solid with a very pungent odor and it can create enough heat to explode, so it must not be stored near wood, cloth or petroleum products. Calcium hypochlorite increases the pH of the water being treated.
What is the best way to provide safe water to the end user?
When treatment plants are distant from the point of use, chlorination is the best way to provide safe water to the end user. Municipal water providers usually rely on measurements of “chlorine residual”—the amount of chlorine remaining in the water after it reaches its destination—as proof of safety. Residual requirements vary, but typical residual ...
Which is more effective for disinfecting: chlorine or hypochlorite?
Chemically, this has to do with the relationship between the two constituents of chlorine that together are often referred to as “free chlorine”—hypochlorus acid and hypochlorite ions. Hypochlorus acid is the more effective disinfectant and it dominates at lower pH levels, so a lower pH is preferred for disinfection.
Which is the least expensive chlorine?
Chlorine gas, which is actually sold as an amber-colored compressed liquid, is the least expensive form of chlorine and is, consequently, the preferred type for municipal water systems.
What is the purpose of chlorination in wastewater treatment?
Chlorination, which follows all other steps of treatment, reduces the population of organisms in the wastewater to levels low enough to ensure that pathogenic organisms will not be present in sufficient quantities to cause disease when the wastewater is discharged.
Why is dechlorination needed in wastewater?
Dechlorination. Chlorine needs to be put into wastewater to treat it and oxidize any contaminants it once held when in the sewage system. The chlorination wastewater treatment procedure creates byproducts in treated water. Dechlorination involves removing any chlorine-based byproducts to ensure the water is truly safe.
What is dechlorination in chemistry?
Dechlorination is the process of removing the free and combined chlorine residuals to reduce residual toxicity after chlorination and before discharge. Sulfur dioxide, sodium bisulfite, and sodium metabisulfite are the commonly used dechlorinating chemicals. Activated carbon has also been used.
What is the term for selective destruction of disease-causing organisms in the water supply or in wastewater effluent
Disinfection refers to selective destruction of disease-causing organisms in the water supply or in wastewater effluent. Wastewater, after secondary treatment to remove BOD and solids, may still contain large numbers of microorganisms.
What are the organisms that are in domestic wastewater?
The organisms of concern in domestic wastewater include enteric bacteria, viruses, and protozoan cysts. In response to these concerns, disinfection has become one of the primary mechanisms for the inactivation/destruction of pathogenic organisms.
What are the chemicals used in dechlorination?
Generally, the most common chemicals used for dechlorination are sulfur dioxide, sodium bisulfate, sodium sulfite, sodium thiosulfate and activated carbon. The chemical equivalents required for dechlorination can be calculated, however, laboratory experiments should be used to help to define the required dose.
What is wastewatr?
Control of Waterborne Diseases. As mentioned, wastewatr contains many types of human enteric organisms that are associated with various waterborne diseases. Typhoid, cholera, paratyphoid, and bacillary dysentery are caused by bacteria and amebic dysentery is caused by protozoa. Disinfection refers to selective destruction ...
Why is chlorine added to water?
Chlorine is added to kill any remaining bacteria in the contact chamber. With the enhanced concentration of bacteria as part of the aeration stage, there is a need to test the outgoing effluent for bacteria presence or absence and to disinfect the water.
Why is wastewater pumped into a secondary clarifier?
Treated wastewater is pumped into a secondary clarifier to allow any remaining organic sediment to settle out of treated water flow. As the influent exits the aeration process, it flows into a secondary clarifier where, like the primary clarifier, any very small solids (or fines) sink to the bottom of the tank.
What is activated sludge?
These small solids are called activated sludge and consist mostly of active bacteria. Part of this activated sludge is returned to the aeration tank to increase the bacterial concentration, help in propagation, and accelerate the breakdown of organic material. The excess is discarded.
What is the process of removing large items from the influent?
Removal of large items from the influent to prevent damage to the facility’s pumps, valves and other equipment .#N#The process of treating and reclaiming water from wastewater (any water that has been used in homes, such as flushing toilets, washing dishes, or bathing, and some water from industrial use and storm sewers) starts with the expectation that after it is treated it will be clean enough to reenter the environment.#N#The quality of the water is dictated by the Environmental Protection Agency (EPA) and the Clean Water Act, and wastewater facilities operate to specified permits by National Pollutant Discharge Elimination System (NPDES). According to the EPA, The Clean Water Act (CWA) establishes the basic structure for regulating discharges of pollutants into the waters of the United States and regulating quality standards for surface waters. Under the CWA, EPA sets wastewater standards for industry. The EPA has also developed national water quality criteria recommendations for pollutants in surface waters. EPA's National Pollutant Discharge Elimination System (NPDES) permit program controls discharges.#N#As an example of expected standards, the Biochemical Oxygen Demand (BOD) of average wastewater effluent is 200 mg/L and the effluent after treatment is expected to be >30 mg/L. It is crucial a wastewater facility meets these expectations or risk stiff penalty.#N#The physical process of wastewater treatment begins with screening out large items that have found their way into the sewer system, and if not removed, can damage pumps and impede water flow. A bar screen is usually used to remove large items from the influent and ultimately taken to a landfill.
What happens if water flows too slow?
If the water flow is too slow, it impacts the process up stream. The solids that fall to the bottom of the clarifier are know as sludge and pumped out regularly to ensure it doesn’t impact the process of separation. The sludge is then discarded after any water is removed and commonly used as fertilizer.
What happens after a wastewater treatment plant meets all permit specifications?
After meeting all permit specifications, clean water is reintroduced into the environment. Although testing is continuous throughout the wastewater treatment process to ensure optimal water flow, clarification and aeration, final testing is done to make sure the effluent leaving the plant meets permit specifications.
What is a bar screen in wastewater treatment?
A bar screen is usually used to remove large items from ...
Why is it important to remove chlorine from water?
It is important to remove chlorine because wastewater effluent is discharged into streams, rivers, and lakes, which provide habitat for wildlife and plant life. Without dechlorination, excess chlorine may kill the wildlife and plant life. Dechlorination of plant effluent flow may be accomplished by various processes.
What is chlorine residual?
It is the component of the applied chlorine that is available for disinfection. The residual is available in three forms:
What is the demand for chlorine?
The demand by inorganic and organic materials is referred to as the chlorine demand. It is the difference between the amount of chlorine applied to the wastewater and the amount of residual chlorine after a given contact time.
What is the most commonly used disinfection process for wastewater treatment?
Chlorine and its various forms are powerful oxidants that will kill or inactivate most pathogenic organism that are harmful to human and animal life. Chlorination is the most commonly used disinfection process for wastewater treatment.
Why do you need to dechlorinate after disinfection?
The effluent from a wastewater treatment plant may need to be dechlorinated after disinfection because of harmful affects the chlorine residual may have on fish, wildlife , and even human health.
How is chlorine dioxide generated?
Due to its instability, chlorine dioxide is generated on site and used within a short period of time after generation. Two systems are used to generate the chemical. In each, the process blends chlorinated water or hydrochloric acid with sodium chlorite in a mixing chamber to produce chlorine dioxide. The reactions are as follows:
How much chlorine is in a cylinder?
Elemental chlorine is provided in liquid form and delivered in 150-pound cylinders and 1-ton containers.
Wastewater Disinfection
- The STP treats the wastewater coming from agriculture, sewage and industrial plants. The treatment process has four stages (pretreatment, primary, secondary and tertiary treatment). Before chlorination, wastewater must be free of all contaminants (inorganic and organic wastes). Theprimary and secondary treatment eliminates 85% of organic matter. Te...
Forms of Chlorine
Disinfection By-Products
Chlorine Monitoring
- The primary concern of wastewater disinfection is the removal of pathogenic microorganisms. Secondarily, wastewater discharge should not contain compounds with environmental health impacts. While a chlorine residual is desirable in drinking water treatment, it is not desirable in wastewater treatment where chlorine discharged to the natural environ...