To remove BOD, the sewage treatment facility needs to aerate the water. This requires a large amount of power, also known as electricity. The higher the BOD, the more sludge you need to dispose of.
Full Answer
How can the BOD of water be reduced?
The BOD of water can be reduced by reducing pollution. The lesser we contaminate the water bodies lesser is its biochemical oxygen demand levels. There are various treatments done to reduce BOD levels in various wastewaters. The secondary effluent treatment is done in the sewage treatment plants to reduce the BOD in the sewage wastewater.
What are the methods of BOD removal in wastewater treatment?
Several techniques are used for BOD removal in wastewater prior to reuse or safe disposal. Three common BOD reduction methods for wastewater treatment are: Wastewater clarification. Wastewater separation (Coagulation & Flocculation) Anaerobic microbial decomposition. Wastewater clarification and separation BOD reduction methods are part ...
Why is the cod/BOD ratio important in wastewater treatment?
This is important because "wastewater with a high COD to BOD ratio indicates that a substantial part of the organic matter will be difficult to degrade biologically" (Henze, et al., 2008). The table and bar graph below will give you an idea of just how variable the COD/BOD ratio can be.
What is BOD test in water treatment?
Wastewater treatment plants use BOD value as an index to ascertain the overall degree of organic pollution in a water source. A BOD test is typically carried out over a standard 5-day incubation period at 20°C (68°F) for the most accurate results. Generally, a higher BOD value indicates a higher level of water pollution, ...
How do you treat high water BOD?
These are the best practices for reducing BOD and TSS that facility managers should know:Focus on removing TSS from wastewater first. ... Get a properly sized EQ tank. ... Control the pH of the waste stream. ... Install a modern plate pack DAF made of stainless steel or plastic. ... Use a regenerative turbine air dissolution pump.More items...•
What happens if BOD levels are to high?
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. The consequences of high BOD are the same as those for low dissolved oxygen: aquatic organisms become stressed, suffocate, and die.
How is most BOD removed in a wastewater treatment plant?
BOD is fairly easy to remove from sewage by providing a supply of oxygen during the treatment process; the oxygen supports bacterial growth which breaks down the organic BOD. Most enhanced treatment units described incorporate some type of unit which actively oxygenates the sewage to reduce BOD.
What would cause a 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 considered high BOD?
At BOD levels of 100 ppm or greater, the water supply is considered very polluted with organic waste. Generally, when BOD levels are high, there is a decline in DO levels. This is because the demand for oxygen by the bacteria is high and they are taking that oxygen from the oxygen dissolved in the water.
What is the permissible limit of BOD in wastewater?
The Significance of BOD in Wastewater Treatment BOD is listed as a conventional pollutant under the U.S. Clean Water Act. Typical maximum values range from 10 mg/L for direct environmental disposal and 300 mg/L for disposal to sewer systems.
Does activated sludge remove BOD?
Aeration is used to operate activated sludge process units and is perhaps the most frequently used process to remove biochemical oxygen demand (BOD) from wastewater.
How can we reduce TDS in wastewater treatment?
Various methods such as physical adsorption, reverse osmosis (RO), distillation, precipitation, membrane filtration, and bacteria-based bioremediation have been developed to reduce/remove TDS from water streams (Pinto et al., 2016). Most of those methods, however, are not cost-effective and/ or environmental friendly.
Why is BOD value important in wastewater treatment?
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 in sewage treatment plant?
BOD is a measure of the amount of oxygen required to remove waste organic matter from water in the process of decomposition by aerobic bacteria (those bacteria that live only in an environment containing oxygen).
Which wastewater treatment process is responsible for removal of most of the BOD in sewage?
4) The purpose of tertiary sewage treatment is to remove all of the phosphorus, nitrogen, and BOD left from secondary treatment.
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 the maximum BOD level for wastewater disposal?
Clean Water Act. Typical maximum values range from 10 mg/L for direct environmental disposal and 300 mg/L for disposal to sewer systems .
How does wastewater clarification work?
Wastewater clarification removes organic solids (primary sludge) from the water by utilizing the force of gravity – in other words, the heavier particles settle to the bottom and are removed first. Wastewater clarification is often followed by a chemical separation process.
What is the name of the agglomerating agent that is added to wastewater to make it clumps
In coagulation, a non-toxic agglomerating agent such as Ferric Chloride (F e Cl) or alum is added to the wastewater causing the suspended particles to come together to form clumps which can easily be removed from the water by filtration.
What is the BOD test?
A BOD test is typically carried out over a standard 5-day incubation period at 20°C (68°F) for the most accurate results.
Why do municipalities use a BOD test?
Municipalities can use a BOD test to detect water contamination in their public supply to ensure that it is safe for human consumption. Industries need to know their BOD value to determine when treated wastewater is safe for reuse or disposal.
Why is groundwater important?
Groundwater is essential in sustaining plant and animal life and as a raw material for many industries . Wastewater is water that has been contaminated from human activity, environmental, or industrial processes and must be treated for reuse or safe disposal. Usually determined alongside chemical oxygen demand (COD) in wastewater treatment, ...
What is flocculation in water?
Flocculation uses a chemical polymer (flocculating agent) to precipitate organic particles out of the water by coalescing to form larger particles or flocs. These larger particles can then be deposited into a sedimentation tank for further treatment prior to disposal.
What is BOD in wastewater?
Industries that discharge wastewater into municipal sanitary sewers or waterways are facing strict regulations on levels of biological or biochemical oxygen demand (BOD). Solid materials in wastewater can consist of organic and/or inorganic materials and organisms.
What are the two types of oxygen demand?
Two major types of Biological Oxygen Demand are: Soluble BOD. Insoluble BOD.
What is the purpose of a biological oxygen demand test?
Biological Oxygen Demand (BOD) is a chemical procedure for determining the amount of dissolved oxygen needed by aerobic biological organisms “bio-bugs” in a body of water to break down organic material present in a given water sample at a certain temperature over a specific time period. It is not a precise quantitative test, although it is widely used as an indication of the quality of water.
Does ALAR water treatment increase BOD?
ALAR Water Treatment provides these industries with cost effective wastewater equipment solutions in order to help achieve BOD discharge compliance.
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A simple change
The trouble started on July 4, when the silicone pump tubing on the effluent sampler split during the night, and a 24-hour composite sample was not pulled. Plant personnel replaced the pump tubing and suction line with new silicone pump tubing and a new vinyl suction line.
Adjusting aeration
Next, the team took the No. 2 aeration basin offline and increased the blower output to the No. 1 aeration basin from 80 percent to 100 percent. The thought was that increased air to the MLSS would allow soluble CBOD to be oxidized more completely, and so the effluent CBOD would decrease. Instead, the weekly average CBOD result rose to 12.5 mg/L.
Digging deeper
As a next step, the operators began profile sampling throughout the plant. They collected grab samples at the chlorine contact chamber, the clarifiers and the final effluent cascade, and set them up for CBOD analysis. Next, they borrowed a portable composite sampler from another treatment plant and set it up at the secondary clarifiers.
About the author
Andrew J. Douglas is a project manager with ClearWater Solutions in Hanceville, Alabama.
What is the BOD of water?
Ans. BOD or Biochemical Oxygen Demand is the measure of the amount of oxygen utilized by aerobic microbes to degrade the organic waste present in water. It is calculated over five days at a specific temperature of 20°C.
What is the importance of BOD in sewage treatment?
These are -. BOD finds its primary importance in sewage treatment plants. It gives the respiration rate of sewage, sludge , soil, garbage. It determines the rate of respiration in living beings. Measuring BOD gives the COD or Chemical Oxygen Demand of inorganic substances. It indicates the polluting potential of water.
Why is it important to reduce the biochemical oxygen demand of water bodies before discharging into water bodies?
It is extremely important to reduce the biochemical oxygen demand of water bodies or wastewater before discharging into water bodies because high BOD of water means more and more oxygen is utilized by the aerobic bacteria for breaking down the organic waste in the water. This significantly reduces the available oxygen for the respiration ...
How does pollution affect the BOD of water?
Sources that increase Biological Oxygen Demand of water are both natural and man-made. Pollution is a major contributor to increasing the BOD of water bodies. A good lifestyle is associated with an ample usage of water on a regular basis which results in a lot of wastewater with organic content in it. With increasing industrialization, pollution is increasing manifold. Factories have enormous wastewater being generated. Few industries that have huge quantities of wastewater are paper mills, food processing plants, jute mills, etc. The environmental factors contributing to increasing BOD include surface runoff, floating debris, dead animal and plants, soil erosion, etc. There are few chemicals that affect the BOD of drinking water. One of these is phosphate, which when present in high amount increases the BOD of water.
How is oxygen demand measured in water?
Biochemical Oxygen Demand of a water sample is measured by a Bioassay procedure which measures the oxygen consumed by the bacteria from the decomposition of the organic matter over a period of five days at an incubation temperature of 20°C. BOD is expressed in milligrams per litre of sample water. Although this is not a precise quantitative test, it is widely used as an indication of the polluting potential of water. This test was given by Sawyer and McCarty in the year 1978.
How can the BOD of water be reduced?
The BOD of water can be reduced by reducing pollution. The lesser we contaminate the water bodies lesser is its biochemical oxygen demand levels. There are various treatments done to reduce BOD levels in various wastewaters.
What happens when the BOD of a water body increases?
When BOD of a water body increases significantly, the aquatic life is adversely affected . The oxygen used by aquatic organisms for respiration and metabolism is significantly reduced by the microbes for breaking down of organic waste.
What is the COD to BOD ratio?
The table below shows that the COD/BOD ratio is commonly referenced as being 2.1 but this is an approximate value that will fit better with municipal wastewater. As the industrial contribution increases to a municipal wastewater plant the COD/BOD ratio is likely to increase. But by how much? For strict industrial wastewater plants the COD/BOD ratio can be highly variable, increasing significantly beyond the oft-used 2.1 ratio value. This is important because "wastewater with a high COD to BOD ratio indicates that a substantial part of the organic matter will be difficult to degrade biologically" (Henze, et al., 2008).
What is the F:M ratio of activated sludge?
For the activated sludge process to operate properly there must be a balance between the food entering the bioreactor and the microorganisms in the bioreactor. A high F:M ratio means there is a greater quantity of food (measured as BOD, COD, or TOC) relative to the quantity of microorganisms available to consume that food. When the F:M ratio is high, the bacteria are active and multiply rapidly but they are also more dispersed in suspended growth bioreactors. Because of that dispersion, a high F:M ratio creates an environment where the bacteria will not form a good, large, dense floc. For that reason, a high F:M ratio will often result in a poor settling sludge in the secondary clarifier and a turbid effluent.
How to calculate F:M ratio?
In order to calculate the F:M ratio two quantities are required: 1) the pounds (kilograms) of organic material entering the bioreactor and 2) the pounds (kilograms) of microorganisms in the bioreactor. The standard equation for calculating the food-to-mass (microorganism) ratio is shown in the equation below.
Why is the F:M ratio high?
Because of that dispersion, a high F:M ratio creates an environment where the bacteria will not form a good, large, dense floc. For that reason, a high F:M ratio will often result in a poor settling sludge in the secondary clarifier and a turbid effluent.
What does low F:M mean?
A low F:M ratio means there are many microorganisms but there is a limited amount of food. Only when the food supply is limited do bacteria begin to develop a thicker slime layer, lose their motility, and begin to clump together to form a dense floc that will settle well in the clarifier.
First, Let's Define Some Terms
Important Measures in Waste Water
- The most important measures for wastewater treatment are total suspended solids (TSS) and biochemical oxygen demand (BOD). You may already know that there are some important reasons why you need to manage TSS and BOD: 1-TSS/BOD values ??should comply with government environmental regulations. 2-High levels of TSS can be seriously harmful to wildlife, making wat…
Water Management
- 1. We will focus on removing TSS from wastewater. Reducing TSS will, in most cases, reduce BOD as well. Mostly, mechanical sieves such as rotary strainers and rod sieves are used to remove large solids. It can also protect downstream dissolved air levitation (DAF) equipment from damage and clogging. 2. Get a big EQ tank. Changes in flow and load fa...
Conclusion
- Netsol Waterand their technologies can support efforts in this area. Most water flows through certain drains before leaving the facility. We are STP/ETP specialists. Our professional fab shop can design and manufacture almost any STP/ETP you need. We work with leading manufacturers around the world to solve your sewage and drainage problems. Look around our website or call …