what causes high bod in wastewater

What Causes High Bod In Wastewater?

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.Mar 12, 2020

What causes BOD to increase?

High biochemical oxygen demand can be caused by: high levels of organic pollution, caused usually by poorly treated wastewater; high nitrate levels, which trigger high plant growth.

What does high BOD indicate?

BOD indicates the amount of putrescible organic matter present in water. Therefore, a low BOD is an indicator of good quality water, while a high BOD indicates polluted water. Dissolved oxygen (DO) is consumed by bacteria when large amounts of organic matter from sewage or other discharges are present in the water.

How do you reduce BOD levels 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 affects BOD in water?

Biological oxygen demand directly affects the amount of dissolved oxygen in rivers and streams. The rate of oxygen consumption is affected by a number of variables: temperature, pH, the presence of certain kinds of microorganisms, and the type of organic and inorganic material in the water.

Under what conditions BOD is lowered in the river?

When the amount of organic matter decreases and the microbes do not need oxygen for decomposition the BOD decreases.

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.

How can I reduce my BOD?

These are the best practices for reducing BOD and TSS that facility managers should know:
  1. Focus on removing TSS from wastewater first. …
  2. Get a properly sized EQ tank. …
  3. Control the pH of the waste stream. …
  4. Install a modern plate pack DAF made of stainless steel or plastic. …
  5. Use a regenerative turbine air dissolution pump.

How does high BOD influence water quality?

BOD directly affects the amount of dissolved oxygen in rivers and streams. The greater the BOD, the more rapidly oxygen is depleted in the stream. This means less oxygen is available to higher forms of aquatic life.

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Why is BOD important in wastewater treatment?

BOD has traditionally been used to measure of the strength of effluent released from conventional sewage treatment plants to surface waters or streams. This is because sewage high in BOD can deplete oxygen in receiving waters, causing fish kills and ecosystem changes.

Does chlorine reduce BOD?

BOD reduction: Chlorine accomplishes BOD reduction by oxidation of organic compounds present in wastewaters. … Oxidation of metal ions: Metal ions which are in reduced state are oxidized by chlorine (e.g., ferrous to ferric ion and manganous to manganic ions).

What is the permissible limit of BOD in wastewater?

Parameter Unit Maximum permissible limit
Chemical Oxygen Demand (COD) mg/l 120
Biochemical Oxygen Demand (BOD5) mg/l 40
Chloride mg/l 750
Sulphate mg/l 750

What is BOD removal efficiency?

So, coming into the plant is 245 mg per liter of BOD and leaving there’s 22 mg per liter. We have a formula that says efficiency or removal efficiency equals what’s coming in minus what’s coming out then you divide that by what’s coming in and then we multiply by a 100 to convert the decimal to a percent.

Is high BOD 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.

What is meant by BOD and COD?

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 causes high bod in wastewater
what causes high bod in wastewater

What is the Fullform of bod?

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.

What is bod in zoology?

biochemical oxygen demand (BOD), the amount of dissolved oxygen used by microorganisms in the biological process of metabolizing organic matter in water.

How is BOD affected by temperature?

The amount of oxygen that can dissolve in water (DO) depends on temperature. Colder water will have a higher DO level than warmer water. … Therefore, increased water temperatures will speed up bacterial decomposition and result in higher BOD levels. Temperature also influences the survival of aquatic organisms.

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What is the relationship between BOD and DO?

The amount of dissolved oxygen used up by aerobic microorganisms to decompose the organic matters present in a sample of water is termed Biochemical Oxygen Demand or Biological Oxygen Demand (BOD). BOD and DO are inversely proportional to each other i.e a decline in DO levels reflects a high level of BOD.

Why is BOD done for 5 days?

The standard oxidation (or incubation) test period for BOD is 5 days at 20 degrees Celsius (°C) (BOD5). The BOD5 value has been used and reported for many applications, most commonly to indicate the effects of sewage and other organic wastes on dissolved oxygen in surface waters (see TECHNICAL NOTE).

How does BOD measure 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. … The decay of organic matter in water is measured as biochemical or chemical oxygen demand.

What are the limitations of the BOD test?

Limitations Of Test

The method takes five days to perform and uses a discrete sample. The test has poor reproducibility and toxic chemicals can inhibit measurement. Short-term BOD determinations magnify errors and still require relatively long sample periods. The test is not suited for on-line, continuous measurement.

Does chlorine increase bod?

Chlorine dosages above 10 mg l1 resulted in increased BOD and COD levels of the effluent, with chlorine dosages above 30 mg l1 resulted in almost double the original BOD and COD values. … Effects of chlorine on BOD and COD were also confirmed by actual data reported by the treatment plant.

Why must interference of chlorine prevent in BOD determination?


Because chlorine is such a strong oxidizing agent, it will inhibit the growth of living bacteria in the BOD test. Any samples containing residual chlorine must be pretreated to remove chlorine before the test is run. This is done by adding sodium sulfite to the sample.

Does chlorine affect chemical oxygen demand?

The laboratory study results demonstrated that chlorination did not change the particle size distribution, dissolved organic carbon, or chemical oxygen demand of the organic content of the effluent.

What is the BOD value of highly polluted water?

A BOD value of more than 100 ppm suggests that water is highly polluted.

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What is the range of BOD?

BOD values range widely; generally, pristine waters have a value below 1 mg l1, moderately polluted waters 2–8 mg l1, and treated municipal sewage 20 mg l1. Standards for the discharge of effluent from WWTPs have the range 20–30 mg l1 and require a minimum flow in receiving waters to ensure sufficient dilution.

What is the BOD of normal water?

A BOD level of 1-2 ppm is considered very good. There will not be much organic waste present in the water supply. A water supply with a BOD level of 3-5 ppm is considered moderately clean.

What is the expected BOD removal after both primary and secondary treatment?

A sewage treatment plant providing both primary and secondary treatment is expected to remove at least 85 percent of the BOD and suspended solids from domestic sewage.

What is high rate trickling filter?

The high rate trickling filter, single stage or two stage are recommended for medium to relatively high strength domestic and industrial wastewater. The BOD removal efficiency is around 75 to 90% but the effluent is only partially nitrified.

How is BOD level calculated?

The BOD level is determined by comparing the dissolved oxygen levels of a water sample before and after 5 days of incubation in the dark (see the next section for this).

What happen 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 does high COD to BOD ratio of an organic pollutant represents?

A high COD to BOD ratio means that the organic pollutant has very less organic matter which can be oxidized by the pollutant. This ratio is generally greater than 1 but can be equal to 1 if the sample has only biodegradable organics.

BOD (biological oxygen demand) – The water quality indicator

Biochemical Oxygen Demand (BOD): Explained details (Animation)

COD (Chemical oxygen demand) – Indicator for water pollution


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