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Wastewater Treatment

How a business treats wastewater will depend on its Biological Oxygen Demand and Chemical Oxygen Demand. BOD and COD are two similar measurements which very easily confuse people looking to improve how wastewater is handled.

What is BOD in wastewater?

Biological Oxygen Demand (BOD) is one of the primary pollutants that make up the trade effluent which is discharged from your business into the local sewerage system. Businesses need to ensure they keep BOD to a satisfactory level or else it can cause problems for the local water system. The higher the BOD level that is found in your effluent, the more damaging it would be to microorganisms in sewage.

What is COD in wastewater?

Chemical Oxygen Demand (COD) is a measurement of oxygen required to oxidise materials present in water chemically. For example, if you have the likes of ammonia or nitrate in your water, you’d want to show that COD is at a level where water can oxidise efficiently. Essentially, the higher the COD, the lower your dissolved oxygen levels will be.

What’s the difference between BOD and COD?

They may sound like the same thing, and it is easy to get confused, but there are key differences between BOD and COD.

BOD is always looking at the oxygen needed for bacteria to break down biologically/ naturally and help the local water ecosystem. COD is always looking at the overall chemical levels in water and how much oxygen is needed to decompose both organic and inorganic through a chemical reaction to make it safer.

Essentially, they are both measurements to help ensure water is being treated to protect organisms (BOD) and help remove harmful chemicals (COD) to keep oxygen levels healthy.

What determines the limits for BOD and COD?

Location, water quality, discharge amounts and industry limits are what play the biggest part in wastewater management for businesses in the UK.

For example, a company could have two identical facilities operating in the same manner (for argument’s sake, let’s say they’re located in Newcastle and Portsmouth), but could find that satisfactory wastewater levels are completely different based on regional requirements. It’s why coastal properties can get away with higher concentrations in their water.

It can often cause companies headaches, especially when operating multiple locations on a national scale.


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How is BOD treated?

The approach taken to help lower BOD will vary dramatically based on the business. For example, an agriculture type business will have to treat naturally occurring pollutants in a completely different manner to an industrial business which would be creating artificially high BOD sewage.

Such differences are one of the reasons why the government has different BOD restrictions in place. Ensuring a business is compliant within their industry and location is essential.

How would I know if my business is in a “problem” area?

Businesses which need to use water on a larger level and would be located near designated “safe” areas can often find it hardest to treat wastewater efficiently. Examples of this would include areas of freshwater or nitrate sensitive waters, and where the local wholesaler needs to source drinking water.

Typically, the Environmental Agency has the responsibility of letting a business know if they are in a sensitive area and will set out what guidelines need following.

Can Castle Water help with controlling BOD and COD Treatment?

Castle Water has specialist partners which help customers who need wastewater management in place to curb BOD and COD levels. Please call Castle Water today on 01250 718 700 or contact us here to enquire about these services.

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