Chemical oxygen demand (COD) is widely used as an organic pollution indicator in wastewater treatment plants. Large amounts of organic matter are removed during treatment processes to meet environmental standards, and consequently, substantial greenhouse gases (GHGs) such as methane (CH4) are released.
What does a high COD indicate?
The higher the COD value, the more serious the pollution of organic matter by water. The most common application of COD is in quantifying the amount of oxidizable pollutants found in surface water (e.g., lakes and rivers) or wastewater (Davidson, 2001; Sara and Goncaloglu, 2008).
What COD means?
COD is defined as the amount of oxygen equivalents consumed in the chemical oxidation of organic matter by strong oxidant (e.g., potassium dichromate).
What does COD mean in wastewater?
Closely related to Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD) is another important water quality parameter that industrial and municipal authorities should be familiar with to determine the best wastewater treatment methods for their needs.
What are the source of COD?
Sources of COD in stormwater are varied. However, soluble organic compounds are most likely to contribute to escalated COD concentrations. Residual food waste from bottles and cans, antifreeze, emulsified oils are all high in COD and are common sources of COD for industrial stormwater.
How do you reduce COD?
One way to reduce COD in water is to use coagulants and flocculants to bind sludge together. Once they are bound into big enough masses that they can be easily filtered out and deposited into a sedimentation tank for removal. This method does however rely on the use of chemicals, and requires high reoccurring cost.
What causes COD to increase?
COD increases as the concentration of organic material increases. It also increases if inorganic compounds susceptible to oxidation by the oxidant (typically dichromate) are present. Water with high COD typically contains high levels of decaying plant matter, human waste, or industrial effluent.
How does COD work?
How Does Cash on Delivery Work? Buyers place an order, for example, on a website, and request delivery. The customer does not make payment while ordering the item and chooses cash on delivery as a payment method. Once the order is placed, an invoice is prepared by the seller, which is attached to the parcel.
What chemicals are used in COD?
COD is measured via a laboratory assay in which a sample is incubated with a strong chemical oxidant for a specified time interval and at constant temperature (usually 2 h at 150°C). The most commonly used oxidant is potassium dichromate, which is used in combination with boiling sulphuric acid.
How do you check for COD?
The most common test method is the colorimetric analysis after oxidizing the COD with acid and using indicator compounds, such as hexavalent dichromate. In some instances, however, there are compounds that will interfere with the colorimetric analysis, and titration is required to determine COD levels.
How do you reduce COD in waste water?
You can reduce COD and BOD by adding hydrogen peroxide to the wastewater solution. The hydrogen peroxide will chemically attack the organics in the wastewater, degrading them and reducing the measured COD and BOD.
How does COD affect water quality?
When treated wastewater is discharged into the environment, it can introduce pollution in the form of organic content to receiving waters. High levels of wastewater COD indicate concentrations of organics that can deplete dissolved oxygen in the water, leading to negative environmental and regulatory consequences.
How does COD affect the environment?
High COD indicates presence of all forms of organic matter, both biodegradable and nonbiodegradable and hence the degree of pollution in waters. This makes COD useful as an indicator of organic pollution in surface waters (Faith, 2006, p.
Why is COD important?
In wastewater treatment, the Chemical Oxygen Demand (COD) is an important measurement for the amount of oxygen that is required to break down pollutants (organic substances) in water. The chemical oxygen demand can be measured using different methods, direct or indirect.
What is COD in water pollution?
The chemical oxygen demand (COD) is a measure of water and wastewater quality. The COD test is often used to monitor water treatment plant efficiency. This test is based on the fact that a strong oxidizing agent, under acidic conditions, can fully oxidize almost any organic compound to carbon dioxide.
What is the limit of COD?
The chemical oxygen demand (COD) concentration in a treated effluent, if observed to be persistently greater than 250 mg/l before disposal to any receiving body (public sewer, land for irrigation, inland surface water and marine coastal areas), such industrial units are required to identify chemicals causing the same.
How do you test COD in wastewater?
To establish the COD:BOD ratio for your wastewater, simply have both COD and BOD run on several wastewater samples. Divide the COD concentration by the BOD concentration for each sample and average the results.
What is COD removal efficiency?
HMBR revealed excellent COD removal efficiency for treatment of ship domestic sewage: the effluent COD concentration, i.e. 48.5 mg/L, was below the IMO discharge standard and the average COD removal rate was 95.13%.
Is COD still a thing?
In some countries COD remains a popular option with internet-based retailers, since it is far easier to set up for small businesses and does not require the purchaser to have a credit card. Many small businesses prefer cash payment to credit card payment, as it avoids credit card processing fees.
What does COD stand for in business?
cash on delivery (C.O.D.), also called collect on delivery, a common business term indicating that goods must be paid for at the time of delivery. The payment is usually due in cash but may be made by check if acceptable to the seller.
Is COD still available?
The Postal Service is planning to end COD mail to home addresses. Under current policy, COD — officially “Collect on Delivery,” aka “cash on delivery” — can be delivered by the carrier to an address (COD per se) or it can be picked up by the customer at the post office, which is officially “Hold For Pick Up” (HFPU).
Lorraine Wade is all about natural food. She loves to cook and bake, and she’s always experimenting with new recipes. Her friends and family are the lucky beneficiaries of her culinary skills! Lorraine also enjoys hiking and exploring nature. She’s a friendly person who loves to chat with others, and she’s always looking for ways to help out in her community.