Full Answer
How does chlorination work in wastewater treatment?
Nearly every wastewater treatment facility uses chlorination to disinfect wastewater before the water is sent back out into the environment. The primary goal of chlorination is to disinfect the wastewater and remove any harmful pathogens that are present in the water.
What are the chlorine requirements for wastewater treatment plants?
CHLORINE REQUIREMENTS Bureau of Safe Drinking Water, Department of Environmental Protection Wastewater Treatment Plant Operator Training 1-8 Chlorine Demand Chlorine will react with wastewater and combine with many of its components. These components react and combine with chlorine prior to its reaction with pathogens.
What is the best method of control for chlorination system?
Compound loop control, as described for the chlorination system, is the preferred method of control. The manual control should only be used when there is a failure of the automatic control system.
What is breakpoint chlorination in wastewater treatment?
Breakpoint chlorinationis related to the chlorine necessary to satisfy the inorganic, ammonia, and organic demands of the wastewater. Once achieved, additional chlorine applied to the wastewater is in the form of free chlorine.
Is chlorination a step in wastewater treatment?
In order for disinfection to be effective wastewater must be adequately treated. Chlorine is the most widely used disinfectant for municipal wastewater because it destroys target organisms by oxidizing cellular material.
Is chlorination a tertiary treatment?
The purpose of tertiary treatment is to provide a final polishing treatment stage prior to discharge or reuse of the wastewater. Chlorination – A water treatment method that destroys harmful bacteria, parasites, and other organisms.
What type of treatment is chlorination?
What is chlorination? Chlorination is the process of adding chlorine to drinking water to kill parasites, bacteria, and viruses. Different processes can be used to achieve safe levels of chlorine in drinking water.
What step is chlorination?
Chlorination may also be done as the final step in the treatment process, which is when it is usually done in most treatment plants. The main objective of this chlorine addition is to disinfect the water and maintain chlorine residuals that will remain in the water as it travels through the distribution system.
What is tertiary treatment of sewage?
Tertiary water treatment is the final stage of the multi-stage wastewater cleaning process. This third stage of treatment removes inorganic compounds, bacteria, viruses, and parasites. Removing these harmful substances makes the treated water safe to reuse, recycle, or release into the environment.
What is primary secondary and tertiary sewage treatment?
Wastewater is treated in 3 phases: primary (solid removal), secondary (bacterial decomposition), and tertiary (extra filtration).
What do you mean by chlorination?
chlorinate. / (ˈklɔːrɪˌneɪt) / verb (tr) to combine or treat (a substance) with chlorine. to disinfect (water) with chlorine.
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 does chlorination work in water treatment?
Chlorination involves adding a measured amount of chlorine to water to produce a residual sufficient to kill bacteria, viruses, and cysts. The killing effect of chlorine depends on the pH of the water, temperature, chlorine level and contact time (i.e., the time the chlorine is in the water before consumption).
What is the fourth step of raw water treatment?
In the fourth step called ozonation, plant workers add a gas called ozone to destroy bacteria and other microorganisms as well as to improve taste. From there, the water is filtered using granular activated carbon to remove any fine particles.
What are the 4 steps of water treatment?
Water treatment stepsCoagulation. Coagulation is often the first step in water treatment. ... Flocculation. Flocculation follows the coagulation step. ... Sedimentation. Sedimentation is one of the steps water treatment plants use to separate out solids from the water. ... Filtration. ... Disinfection.
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.
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.
Primary Wastewater Treatment
In the aspect of water resources pollution, primary treatment is a basic necessity for water resource conservation. The concept and function of primary sewage treatment plant (also called POT (Primary Oxygen Treatment)) will be introduced here briefly:
Secondary Wastewater Treatment
The secondary wastewater treatment is a process that separates the organic solids from the wastewater to form effluent, which is treated and safe to release, and solids that can be used as a fertilizer. It is achieved through the following ways:
Tertiary Wastewater Treatment
The tertiary phase includes chemical treatments to stabilize the water for discharge into waterways or reuse within the industry.
Conclusion
It is essential to select the right technology for a particular application based on the characteristics of the wastewater and the desired results.
What is the final step in chlorine treatment?
Typically, chlorine is added to public drinking water as the final stage of treatment, often following an upstream filtration step which removes sediment that can tie up chlorine and shield organisms from its effect .
What is the process of adding chlorine to water?
Chlorination. Chlorination involves adding a measured amount of chlorine to water to produce a residual sufficient to kill bacteria, viruses, and cysts.
What are the reactions between free chlorine and these acids?
Reactions between free chlorine and these acids may produce a class of compounds called trihalomethanes. Strategies to reduce these in public water supplies include enhanced filtration for better organic removal and use of ammonia together with chlorine to produce chloramines for use in lieu of chlorine.
What is the chemical that is added to water to make trihalomethanes?
Chloramines have longer half-life in the water and are less likely to produce trihalomethanes. Chlorine is typically added to water using chemical feed systems to inject liquid sodium hypochlorite (bleach) solution or added as gaseous chlorine (typical of larger public water treatment plants).
Can chlorine be used in water?
Chlorine cannot be used in most high purity water loops without contaminating the process or interfering with the end use of the water. These systems often rely on ultraviolet disinfection as an alternative to water chlorination.
Does chlorine react with organic compounds?
Unfortunately, chlorine reacts with many organic compounds to form chlorine disinfection by-products that are recognized as potent carcinogens at low levels of concentrations. Such organic compounds include humic and fulvic acids, which derive from rotting vegetation common in surface waters.
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.
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.
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.
What is chlorine residual?
It is the component of the applied chlorine that is available for disinfection. The residual is available in three forms:
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.