Sewage Parameters 1: BOD

Before discussing package sewage treatment it is best to explain the parameters used to define sewage both when it comes into a treatment plant (influent) and when it leaves a sewage treatment plant (effluent)  One of the main parameters to consider is BOD or BOD5 which means Biochemical Oxygen Demand (the ’5′ refers to the sewage being tested for BOD over 5 days, which is standard when testing BOD levels)

In essence it measures the amount of oxygen required by microorganisms in the sewage to break down the organic content contained in the sewage.  Sewage with a high BOD has high pollution potential if discharged untreated into a water course because it can result in severe depletion of the oxygen content of the water and thus kill aquatic animals such as fish which need oxygen to breath.

Influent BOD in normal domestic sewage is generally 300 mg/l and it is then treated to at least 25 mg/l (as per European norms) before discharge to minimise pollution potential.  Most package sewage treatment plants or package wastewater treatment plants such as the BMS Blivet are designed to produce 25 mg/l of BOD at a minimum but much stringent more stringent BOD levels down to 5 mg/l can be produced if specified.

Next up will be Suspended Solids (SS)

If you have any questions please do not hesitate to contact me,


A bit about the company;

Butler Manufacturing Services is a family owned specialist manufacturer of package (all in one) products for sewage treatment and surface water treatment established in 1986 with exports to 38+ countries worldwide including the world leading Blivet package sewage treatment plant, a ‘one stop shop’ for all surface water products from design to installation including attenuation, interceptors, holding tanks (incl. chemical resistant), hydrobrakes, rainwater harvesting tanks/filters & vortex silt separators, chlorine contact tanks, fully fitted pumps and sumps and much more. 

If there is a requirement for any of above on any project that you are working on we would welcome the opportunity to work on a solution with you.