Sewage Parameters 2: Suspended Solids (SS)

Sewage Parameters 2: Suspended Solids (SS)

The next topic in our Sewage Treatment Parameters Education Series is Suspended Solids (SS), which are usually stated in conjunction with Biochemical Oxygen Demand (BOD). The normal European discharge standard for SS is 35 mg/l and is usually quoted in short as ’25/35′ effluent  (BOD of 25 mg/l & SS of 35 mg/l)  Therefore, most package sewage treatment plants will be designed to achieve at least ’25/35′ for a given populations  Suspended solids are the solids visible in influent/effluent sewage which do not settle out easily over time.  A more correct definition is; ‘A measurement of the solids in suspension in sewage, influents or effluents normally expressed in mg/l or parts per million (ppm).

Suspended Solids are normally reduced by both physical means such as settlement and also by biological treatment.  A typical SS concentration in normal domestic effluent is 300 mg/l, which then needs to be reduce to 35 mg/l or better.  To obtain very low Suspended Solids concentrations extra treatment such as with a Saran Filter or Package Final Effluent Polishing Filter (FEPF) might be necessary.  A certain amount of BOD is attached to SS, so reducing SS will also lead to a consequent decrease in BOD.  An effluent with a low SS will look clear to the eye, while as the SS concentration begins to rise the effluent will become increasingly more cloudy.

Next up will be Population Equivalent or PE.

If you have any specific queries or there is any topics you would like explored, please do not hesitate to contact us.

A bit about the company:

BMS is a quality manufacturer of package products for wastewater and stormwater treatment. BMS started in 1986 and has exported products to over 50 countries around the world.  It is a third generation family business with huge expertise in wastewater and stormwater.
BMS manufacture a full range of products for surface water and wastewater treatment including our pioneering next generation RBC system the Aerotor, which forms part of our 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 & vortex silt/oil/debris separators, fully fitted pumping stations, our plug & play vehicle wash water recycling system; the Recyclone and much more.  All BMS products manufactured in our ISO 9001 factory are made using solar energy from our own PV system. 

BMS also can provide a Free Design Service for Sewage Treatment, Pump Stations or Surface Water and a full O&M, Repair, Advice and Testing service for existing installations.  We also can do free CPD Presentations on Sewage Treatment/Surface Water Management at any location. 

We would be delighted to discuss any requirements you might have and we are available to meet you at your convenience.  Please do not hesitate to contact us.

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Sewage Parameters 1: BOD

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Sewage Parameters 3: Population Equivalent (PE) Part 1