Sewage Parameters 3: Population Equivalent (PE) Part 2
Continuing on from the last blog on Population Equivalent (PE) here are some further illustrative PE calculations:
A. Housing Development with:
10 No. 2 Bedroom Old Persons Dwellings,
25 No. 3 Bedroom Houses,
10 No. 4 Bedroom Houses.
Relevant Figures: 1 PE = 200 l of flow & 60 g of BOD per day.
As each of the above full occupants are equal to 1 PE calculating the flow & BOD can be bypassed to come straight to the PE Figure:
10 x 2 Persons, 25 x 4 Persons and 10 x 5 persons = 170 PE.
Working backwards this development will produce a flow of:
170 PE x 200 l = 34,000 l per day & 170 PE x 60 g = 10,200 g per day.
A BMS BL2000 Blivet would be ideal to treat the above development and provide some room for expansion. An example of which can be seen below
B. Hotel with:
50 Bedrooms (EPA Flow 250 l & BOD 75 g),
100 extra meals/day (EPA Flow 25 l & BOD 25 g),
300 function room guests (EPA Flow 10 l & BOD 10 g),
50 bar only guests (EPA Flow 10 l & BOD 10 g),
30 non residential staff/day (EPA Flow 60 l & BOD 30 g).
50 Bedrooms x 2 persons = 100 x 250 l = 25,000 l Flow & 100 x 75 g = 7500 g BOD
100 Meals = 100 x 25 = 2500 l Flow & 100 x 25 = 2500 g BOD
300 Function guests = 300 x 10 l = 3000 l flow & 300 x 10 g = 3000 g BOD
50 Bar only guests = 50 x 10 l = 500 l Flow & 50 x 10 g = 500 g BOD
30 non resident staff = 30 x 60 l = 1800 l Flow & 30 x 30 g = 900 g BOD
Total Flow Per Day: 25,000 l + 2500 l + 3000 l + 500 l + 1800 l = 32,800 l
Total BOD Per Day: 7500 g + 2500 g + 3000 g + 500 g + 900 g = 14,400 g
Divide 32,800 l by 200 l = 164 PE Flow
Divide 14,400 g by 60 g = 240 PE of BOD
BOD Concentration = 14,400 g / 32,800 l = 439 mg/l
Sewage treatment plants should always be sized on the basis of BOD as it is the biological load that has to be treated. Flows can be higher or lower that the BOD and this can vary from country to country. A BMS BL3000 Blivet with a balance tank to deal with peak early morning and evening flows typically produced by a hotel would be ideal for the above project. A Balance Tank can also help screen out non-soluble solids and also be used to lower Total Nitrogen by Denitrification.
Next up, Phosphorus.
If you have any specific queries or there is any topics you would like explored, please do not hesitate to contact us.
Below you can see a BMS BL3000 Blivet Package Sewage Treatment System and Balance Tank being installed at a new hotel
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.
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