Sewage Treatment Terminology Explained A-Z Part 5; Nitrate to Primary Settlement Tank

Butler Manufacturing Services (BMS) Ltd. series explaining terms/jargon/terminology used in the area of sewage or wastewater treatment continues with terms from N-P. The terms are; Nitrate: (NO3), Nitrite (NO2), Nitrification, Nitrogen (Total Nitrogen), Package, Phosphorous (P/TP), Plug Flow, Population Equivalent (PE) & Primary Settlement Tank (PST).

29. NITRATE (NO3): A form of NITROGEN found in aged sewage or after NITRIFICATION.  Although NO3 cannot be used as easily as AMMONIA by plants to make protein it can still cause EUTROPHICATION if present in excessive amounts in effluent.  It can be removed by DENITRIFICATION.

30. NITRITE (NO2): The more unstable form of NITRATE, which is highly toxic to aquatic species.

31. NITRIFICATION: A biological/chemical process whereby AMMONIA and amino acids are converted to NITRATE under AEROBIC conditions.  It takes place after BOD/SS reduction.  Please note that nitrifying bacteria are quite temperature sensitive and generally a multiple of 4 x the equivalent BOD capacity is required for Nitrification in a temperate climate and 3 x the equivalent BOD capacity in a warm climate.

32. NITROGEN (TOTAL NITROGEN): Nitrogen exists in many forms in nature.  In summary it starts as plant/animal protein, then degrades quickly to AMMONIA, which is then converted to NITRATES (NITRIFICATION), which if an ANOXIC environment is present, will be converted to Nitrogen and Oxygen gas, which is given off into the atmosphere.  The gaseous Nitrogen is then returned to the food chain via nitrogen fixing bacteria/algae and fertiliser etc.

33. PACKAGE: Refers to an ‘all in one’ product.  In relation to a SEWAGE TREATMENT SYSTEM it refers to a system containing primary settlement, biological treatment and final settlement in one self-contained unit that is fully road transportable e.g. the BMS Blivet.

34. PHOSPHORUS (P)/ORTHO PHOSPHORUS (OP): Phosphorus levels are often focused on in SEWAGE EFFLUENT as it is an essential mineral in the growth of algae and other biological organisms along with NITROGEN. Orthophosphates are immediately available for biological metabolism without further breakdown and are therefore the most important polluting form of Phosphorus.  P is also sometimes referred to as Total Phosphorus (TP). 

35. PLUG FLOW: A system where SEWAGE is discharged in the same sequence that it enters.  In relation to the BMS AEROTOR this means that all sewage has to pass through an Aerotor to reach the next stage of treatment and cannot be bypassed.  97% of the surface area of the BMS Aerotor is inside the rotor.  Fluid enters through holes on one side of the Aerotor and after passing through an intense internal spiral surface area emerges from holes on the peripheral side.  This means that sewage receives full treatment even when there are large low/high flow variations, which is a large advantage compared to other systems.  Another example of a plug flow system is an oxidation ditch.

36. POPULATION EQUIVALENT (PE): The equivalent, in terms of a fixed population, of a varying or transient population (e.g. Airport, Office, School or Restaurant) based upon BOD production of 60 g/BOD/person/day and a SEWAGE flow of 200 litres/person/day.

37. PRIMARY SETTLEMENT TANK (PST): A tank in which the majority of settleable solids are removed from crude or RAW SEWAGE.  It needs to achieve an upward flow velocity of 0.9 m/s or less for settlement to take place.

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 R to S; Raw Sewage to Sewage Treatment Plant/System.

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.