Why COD is removed?

COD Removal by Microbial Action

Aerobic COD removal introduces microorganisms or bacteria that break down organic compounds present in wastewater into carbon dioxide and water in the presence of air. Aerobic COD removal is ideal for wastewater with COD < 3000 mg/L.

How is BOD and COD removed?

Hydrogen peroxide (H2O2) has been used to reduce the BOD and COD of industrial wastewaters for many years.

What causes COD in wastewater?

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.

What chemical is used to remove 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.

What does COD mean in wastewater treatment?

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.

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What is the effect of COD in wastewater?

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.

What are the limitations of COD?

One of the main limitations of the COD test is its inability to differentiate between biodegradable and biologically inert organic matter on its own. The use of chemicals such as chromium and strong acids produce hazardous liquid waste, which requires careful disposal.

Does aeration remove COD?

Aeration should help reduce the COD in 2 ways. First it may evaporate some volatiles like hexane. Second it will add oxygen to the water speeding up any biological oxidation of the less volatile organics by the bacteria (microbial growth).

What if COD is high in water?

A higher COD in a sample indicates that it contains higher levels of oxidisable material. If this is the case, then the water will have reduced dissolved oxygen levels. Where this happens, the effects can be environmentally damaging to higher aquatic lifeforms.

What will happen if COD level is high in water?

Higher COD levels mean a greater amount of oxidizable organic material in the sample, which will reduce dissolved oxygen (DO) levels. A reduction in DO can lead to anaerobic conditions, which is deleterious to higher aquatic life forms.

What is COD significance?

COD is a measure of the oxygen equivalent of the organic matter in a water sample that is susceptible to oxidation by a strong chemical oxidant. COD is widely used as a measure of the susceptibility to oxidation of the organic and inorganic materials present in water bodies and in the municipal and industrial wastes.

What is the typical COD in domestic wastewater?

Influent COD in normal domestic sewage is therefore generally 600 – 900 mg/l and it is then treated to at least 75 -100 mg/l before discharge to minimise pollution potential.

Is COD better than BOD?

BOD measures the amount of oxygen required by the aerobic organisms to decompose organic matter and COD measures the oxygen required to decompose organic and inorganic constituents present in the wastewater by chemical reaction. Hence, the value of COD is greater than BOD.

Why is COD more important than BOD?

COD is typically greater than BOD because more organic compounds can be chemically oxidized than biologically oxidized. This includes chemicals toxic to biological life, which can make COD tests very useful when testing industrial sewage because BOD testing will not detect them.

Can activated carbon remove COD?

It was found that for dosages of activated carbon in the range of 50–150 mg/l, the removal efficiencies for BOD increased from 27–70% to 76–94% while those for COD increased from 16–64% to 72–92.5% for inlet values of 45–95 mg/l and 110–200 mg/l for BOD and COD respectively.

Does COD affect pH?

Whats the correlation between pH level and COD, temperature and COD? Can high or low pH and temperature affect or contribute to high levels of COD from waste water? A. The answer to your question is not simple, but in general, pH and temperature have no effect or simple direct relationship to COD at all.

Can chlorine reduce COD?

These higher COD values also increased the chlorine dioxide treatment demand, whereby treatment with 100 ppm chlorine dioxide was only able to achieve about a 50 % reduction in the COD. Increasing the chlorine dioxide concentration to 200 ppm was able to achieve a much greater COD reduction.

What is the removal efficiency of COD?

The removal efficiency (R) was calculated using the following equation:(1) R ( % ) = 1 − Y Y 0 × 100 where Y₀ and Y represent are the initial and final values of color and COD, respectively.

Why do you have to remove COD from wastewater?

COD Removal by Microbial Action

Aerobic COD removal introduces microorganisms or bacteria that break down organic compounds present in wastewater into carbon dioxide and water in the presence of air. Aerobic COD removal is ideal for wastewater with COD < 3000 mg/L.

Does activated sludge remove COD?

The results showed that the activated sludge, sand filter and the activated carbon were effective for removal of COD from the wastewater.

How is COD reduced?

The COD reduction is made by oxidation in an acid medium of a large part of the oxidizable substances dissolved in the water to be treated. After the treatment, the reduction of COD can be measured by analysis of the acidified medium is more favorable to continued treatment with a much lower reagent consumption.

Does COD decrease with time?

in your research COD decreases with increasing time because the bacteria in the water will grow and degrade the organic matters in your water sample.

Can COD be zero?

COD cannot be minus even theoretically, it is always more or equal to zero.

What causes high COD in stormwater?

High COD/BOD levels in stormwater runoff are cause by the residual food and beverage waste from cans/bottles, antifreeze, and emulsified oils from industrial food processing and agricultural activities. As most forms of COD are water soluble, this pollutant spreads easily via stormwater to waterways.