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.
Relavent 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 flows & 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 would 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.
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 = 3000 l flow & 300 x 10 = 3000 g BOD
50 Bar only guests = 50 x 10 = 500 l flow & 50 x 10 = 500 g BOD
30 non resident staff = 30 x 60 = 1800 l flow & 30 x 30 = 900 g BOD
Total Flow per day = 32,800 l
- Divide 32,800 l by 200 l = 164 PE Flow
- Divide 14,400 g by 60 g = 240 PE of BOD
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.
Next up, Phosphorus.
Any questions about surface water or wastewater treatment please 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.