Any type of chlorine that is added to water during the treatment process will result in the formation of hypochlorous acid (HOCl) and hypochlorite ions (OCl-), which are the main disinfecting compounds in chlorinated water. More detail is provided later on in this fact sheet. A Form of Chlorine + H 2 O -> HOCl + OCl -
Full Answer
What is wastewater chlorination and why is it important?
For the purpose of greater public health, wastewater chlorination is a necessary procedure that’s practiced in every city. The process of wastewater chlorination achieves one important goal: it disinfects the water and frees it of the harmful pathogens.
What is chlorine used for in disinfection?
Chlorine has been used for over a century as a primary water disinfectant and is largely responsible for elimination of water-borne diseases such as typhoid and dysentery in developed countries.
What are the basic components of a wastewater treatment plant?
The type and order of treatment may vary from one treatment plant to another, but this diagram of the Ottawa-Carleton wastewater treatment plant illustrates the basic components. The primary level of treatment uses screens and settling tanks to remove the majority of solids.
How is chlorine added to public drinking water?
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 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 chlorination needed in wastewater?
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.
Why is wastewater chlorination important?
The process of wastewater chlorination achieves one important goal: it disinfects the water and frees it of the harmful pathogens. This must be done, and it happens before the water runs off naturally into oceans, rivers and streams.
What is the residual of chlorine in water?
For disinfection, chlorine is generally added as a gas or liquid (typically as sodium hypochlorite) to produce a free chlorine residual of 0.5 parts per million (ppm) to 2.0 ppm. Unfortunately, chlorine ...
What is the most commonly used form of activated carbon in water treatment filters?
Free chlorine and chloramines can be removed in several ways which are described below: Adsorption Dechlorination can be performed with many types of activated carbon, but granular activated carbon (often 12 x 40 mesh size), or GAC, is the form most commonly used in large water treatment filters.
How much chlorine is in 1,000,000 gallons of water?
If this is an accurate prediction, then water containing 1 ppm of chlorine will contain 8.3 pounds of chlorine per 1,000,000 gallons and will consume 1.4 pounds of carbon. Keep in mind that the adsorption rate can be reduced if sediment and organic molecules foul the GAC’s minuscule pores.
How much carbon reacts with chlorine?
It has been reported that 1 pound of carbon will react with 6 pounds of chlorine .
What is chemical reduction?
Chemical reduction prevents a bacterial breeding ground from being introduced upstream of the rest of the water treatment system. However, downstream treatments such as deionizers may become burdened by certain ions (e.g. chloride, sodium, sulfate, etc.) that are introduced or produced through chemical reduction.
What is downstream treatment?
Downstream treatments can also be used, such as distillation or ultraviolet disinfection. Chemical Dechlorination – Reduction reactions occurring from sulfites, bisulfites, or metabisulfites can also remove chlorine. Chemical reduction prevents a bacterial breeding ground from being introduced upstream of the rest of the water treatment system.
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.
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.
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 is a bar screen in wastewater treatment?
A bar screen is usually used to remove large items from ...
Where do organics sink in a clarifier?
Solids known as organics/sludge sink to the bottom of the tank and are pumped to a sludge digestor or sludge processing area, dried and hauled away. Proper settling rates are a key indicator for how well the clarifier is operating.
What are the different levels of wastewater treatment?
There are several levels of wastewater treatment; these are primary, secondary and tertiary levels of treatment. Most municipal wastewater treatment facilities use primary and secondary levels of treatment, and some also use tertiary treatments.
What is the process of removing pollutants from water?
Another natural method is called rapid infiltration, which is a process where a basin is filled with wastewater, which has already gone through a pre-treatment. The ground acts as a filter and removes the pollutants from the water. This method is similar to what happens in a septic system.
How to reduce pressure on septic system?
Following some water conservation practices can greatly reduce pressure on your septic system. For more information about conserving water, see the fact sheet about Water Consumption. Here are a few things that you can do to care for your septic system: 1 Do not use your drain or toilet as a garbage disposal; avoid putting dental floss, diapers, coffee grounds and paper towel down the drain, as they can clog up your septic system. 2 Spread your loads of laundry out over the week. When too much water is added to the septic tank, it does not have time to treat wastes, and you could be flooding your drainfield with wastewater. 3 Plant grass on your drainfield, but keep trees and shrubs away from it, because roots can clog the system and cause damage. 4 Do not drive on your drainfield, because this can compact the soil and damage the septic system components.
Why is oxygen important in wastewater treatment?
The oxygen helps the bacteria to digest the pollutants faster. The water is then taken to settling tanks where the sludge again settles, leaving the water 90 to 95 percent free of pollutants. The picture below shows the settling tanks in the Winnipeg Wastewater Treatment Plant.
What is tertiary wastewater treatment?
Tertiary (or advanced) treatment removes dissolved substances, such as colour, metals, organic chemicals and nutrients like phosphorus and nitrogen.
What is the process of tertiary treatment?
One of the biological treatment processes is called Biological Nutrient Removal (BNR). This diagram shows the treatment steps that Saskatoon wastewater goes through. Biological Nutrient Removal Process.
How much oxygen is removed from water?
The primary treatment generally removes up to 50 percent of the Biological Oxygen Demand (BOD; these are substances that use up the oxygen in the water), around 90 percent of suspended solids, and up to 55 percent of fecal coliforms.
Why is wastewater treated?
Patterns of Use. For many years, humans have treated wastewater to protect human and ecological health from waterborne diseases. Since the early 1970s, effluent water quality has been improved at Publicly Owned Treatment Works (POTWs) and other point source discharges through major public and private investments prescribed by the Clean Water Act ...
How does wastewater treatment affect the environment?
Wastewater treatment systems reduce environmental impacts in the receiving water, but create other life cycle impacts, mainly through energy consumption. Greenhouse gas (GHG) emissions are associated with both the energy and chemicals used in wastewater treatment and the degradation of organic materials in the POTW.
When did effluent water quality improve?
Since the early 1970s, effluent water quality has been improved at Publicly Owned Treatment Works (POTWs) and other point source discharges through major public and private investments prescribed by the Clean Water Act (CWA). Despite the improvement in effluent quality, point source discharges continue to be a significant contributor to ...
What are the stages of wastewater treatment?
What Are the Three 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 process of removing sediment from a wastewater system?
1. Biofiltration. Bio filtration uses sand filters, contact filters or trickling filters to ensure that any additional sediment is removed from the wastewater. 2. Aeration. Aeration is a lengthy process which increases oxygen saturation by introducing air to wastewater.
Where is wastewater held?
During primary treatment, wastewater is temporarily held in a settling tank where heavier solids sink to the bottom while lighter solids float to the surface. Once settled, these materials are held back while the remaining liquid is discharged or moved through to the more rigorous secondary phase of wastewater treatment.
What is tertiary treatment?
In the case of water treated by municipalities, tertiary treatment also involves the removal of pathogens, which ensures that water is safe for drinking purposes.