Biochemical oxygen demand (BOD) is the amount of oxygen it takes to degrade organic matter. Chemical oxygen demand (COD) is the amount of oxygen required to oxidize organic compounds (>500 milligrams per liter). Total suspended solids (TSS) is the total amount of suspended materials (>250 milligrams per liter).
What is COD & BOD?
Biochemical oxygen demand (BOD) is the amount of oxygen required by the microorganisms to break down the organic materials, whereas chemical oxygen demand (COD) is the amount of oxygen required to break down the organic material via oxidation.
What is the relationship between BOD and TSS?
Biochemical oxygen demand (BOD) and total suspended solids (TSS) are related. A portion of the TSS, the volatile suspended solids, is degradable and exerts an oxygen demand in a facultative lagoon or BOD test. BOD is a measurement of the quantity of oxygen required by bacteria to degrade substrate.
What is a good BOD COD ratio?
Typical values for the ratio of BOD/COD for untreated municipal wastewater are in the range from 0.3 to 0.8 (see in table 3). If the BOD/COD ratio for untreated wastewater is 0.5 or greater, the waste is considered to be easily treatable by biological means.
What is BOD and COD in water pollution?
The biochemical oxygen demand (BOD) represents the amount of dissolved oxygen (DO) consumed by biological organisms when they decompose organic matter in water. The chemical oxygen demand (COD) is the amount of oxygen consumed when the water sample is chemically oxidised.
What is BOD in water quality?
Biochemical oxygen demand (BOD) represents the amount of oxygen consumed by bacteria and other microorganisms while they decompose organic matter under aerobic (oxygen is present) conditions at a specified temperature. When you look at water in a lake the one thing you don’t see is oxygen.
Why is BOD done for 5 days?
BOD occurs in 2 general stages. While calculating the oxygen demand, the carbonaceous stage is taken into account. This stage is almost completed in 5 days, which means that most of the organic content of the sewage is oxidized under aerobic conditions in 5 days. Hence ,BOD for 5 days is calculated.
How do you reduce TSS in water?
The first step, chemical treatment, breaks the solids and liquids apart by automatically adding pretreatment chemicals such as pH adjusters, polymers (coagulants and flocculants) or clay. The second step, mechanical filtration, physically removes the precipitated solid particles from the sludge.
What causes high BOD in wastewater?
Sources: BOD represents the amount of organic matter in a water supply; therefore, it increases when decaying plants, human or animal waste, and other organic compounds are added to water.
What is TSS in wastewater treatment?
TSS stands for Total Suspended Solids, and is the term used to refer to the solid particles suspended in water. It is defined as the total amount of solid material, suspended in water, that is retained by a filter.
How COD is calculated?
There is a formula for calculating COD. Consider the formula for COD calculation: (a – b) X C X 8,000 / the volume of the sample in mL. Let “a” represent the titrant used for your sample expressed in mL. Let “b” represent the titrant used for your blank sample in mL.
How is COD BOD calculated?
Typically, the average BOD result is divided by the average COD result to find a “conversion factor” between the two parameters. One would then multiply their COD results by this factor to estimate BOD.
How do you reduce COD in wastewater?
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.
What happens if COD is high?
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 chemical is used in COD?
potassium dichromate
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.
Why is COD so 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 TSS water?
These particles, or ‘solids’, can be divided into two types by passing the water through a filter. The particles that are large enough to be held back by the filter are called total suspended solids (TSS), while the particles that pass through the filter are called total dissolved solids (TDS).
Is high BOD in water good?
Higher BOD indicates more oxygen is required, which is less for oxygen-demanding species to feed on, and signifies lower water quality. Inversely, low BOD means less oxygen is being removed from water, so water is generally purer.
Why BOD is important?
The BOD is an important parameter for assessing water quality. It deals with the amount of oxygen consumption (mg O2 L− 1) by aerobic biological organisms to oxidize organic compounds. Sewage with high BOD can cause a decrease in oxygen of receiving waters, which in turn can cause the death of some organism.
What is BOD unit?
BOD’s are generally expressed as milligrams of dissolved oxygen per liter, which is equivalent to parts per million, PPM. BOD levels can vary considerably. Pristine water sources may show a BOD of less than 2 mg/L of water.
Does BOD increase with temperature?
The BOD removal rate in the bioreactor increased when the temperature increased from 20 degrees C to 30 degrees C, 40 degrees C, and 50 degrees C, but it decreased when the temperature increased from 50 degrees C to 60 degrees C. Higher temperature enhanced the endogenous respiration of microbes in the bioreactor.
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