What Causes High Cod And Bod In Wastewater?

Sources: 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 causes high BOD and COD?

I think that the main causes of the abundance of BOD5 and COD in marine ediments are mainly due to the decomposition of algae that contain a lot of organic matter (BOD5) and fish composed mainly of mineral salts.

What causes high BOD levels?

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.

How do you increase BOD and 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 does high BOD mean in wastewater?

The higher the BOD value, the greater the amount of organic matter or “food” available for oxygen consuming bacteria. If the rate of DO consumption by bacteria exceeds the supply of DO from aquatic plants, algae photosynthesis or diffusing from air, unfavourable conditions occur.

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 is the correlation between BOD and COD?

COD is closely related to BOD or Biochemical Oxygen Demand, the difference being that BOD is a test of the level of organic matter that can be biologically oxidised while COD is a test of the amount of organic matter that can be chemically oxidised.

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.

Does aeration reduce 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).

How do you reduce BOD levels in wastewater?

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 is high COD wastewater treated?

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 is the permissible limit of BOD and COD in wastewater?

According to standards of Central Pollution Control Board, permissible value of BOD is 30 mg/l and COD is 250 mg/l.

Does chlorine reduce BOD?

BOD reduction: Chlorine accomplishes BOD reduction by oxidation of organic compounds present in wastewaters. 4. 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 good COD level in water?

The COD concentrations observed in surface water resources typically range from 20 mg/L or less in unpolluted waters to greater than 200 mg/L in waters receiving effluents.

What is the difference between BOD and COD in wastewater?

BOD measures the oxygen demand for the decomposition of organic material by the microbes in the wastewater. COD measures the oxygen demand for the decomposition of both organic and inorganic materials in wastewater. This is the main difference between BOD and COD.

Is COD always higher than BOD?

COD stands for Chemical Oxygen Demand, and it is the amount of oxygen that will be consumed by the chemical break down of both organic and inorganic compounds. As such, COD will always be higher than BOD.

Does pH affect BOD?

Bacteria that treat waster water to reduce the COD and BOD, are extremely sensitive to pH! So pH can also have a huge effect on activated sludge COD and BOD reduction rates.

What does high BOD mean?

The dissolved oxygen readings are usually in parts per million (ppm). 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 is BOD measured after 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.

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.

Does ammonia contribute to COD?

Results reveal that COD/ammonia ratio has a direct correlation with COD removal efficiency as when COD/ammonia ratio increased from 2 to 10, COD removal efficiency also increased from 80 to 98%.