Sewage Treatment Terminology Explained A-Z Part 3; C to E; Clarifier to Eutrophication

Week 3 of our series explaining terms/jargon/terminology used in the area of sewage or wastewater treatment sees us concentrating on terms beginning with 'C-E'.  The terms are; Clarifier, COD, Combined System, Denitrification, Dry Weather Flow, Effluent, Effluent Treatment Plant/System & Eutrophication.


15. COD: It is a test of the amount of oxygen required to oxidise organic matter in a SEWAGE sample by chemical oxidation with a powerful oxidising agent such as Potassium Dichromate.  It is usually a multiple of the BOD.

16. COMBINED SYSTEM: A SEWERAGE system in which both FOUL and SURFACE WATERS are conveyed in the same sewer.  Combined systems often deliver large flows to a SEWAGE TREATMENT PLANT in wet conditions.  This should be included in any plant design.

17. DENITRIFICATION: A biological/chemical process whereby NITRATE (NO3) is converted to NITROGEN (N) and Oxygen (O2) gas, which is then given off into the atmosphere, in an ANOXIC zone.  It is the only way to reduce TOTAL NITROGEN.

18. DRY WEATHER FLOW (DWF): The average daily SEWAGE flow entering a plant measured following 7 days without rain (excluding local or Bank holidays etc.) and during which on the preceding 7 days, rainfall did not exceed 25 mm on any day.

19. EFFLUENT: The discharge from a SEWERAGE System into a Treatment Plant (See also Influent) and sometimes the discharge from a SEWAGE Treatment Plant (See also Final Effluent).  Generally, a term used to describe waste and wastewater products from a premises, system, process etc.


21. EUTROPHICATION: Where water becomes organically enriched, leading to increasing domination of aquatic plants, transformation to marsh land and eventually to dry land over time.

More detailed explanations of parameters used to measure final effluent quality can be found by clicking on the links e.g. BOD, SS, NH4, N, COD & P.

The next article will explain terms/jargon used in sewage treatment from F to K; Ferric Sulphate to Kjeldahl Nitrogen.

If you have any questions of would like information on package wastewater treatment products, please do not hesitate to contact me.


Tommy butler BMS

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.