Sewage Parameters 3: Population Equivalent (PE) Part 2

Introduction

Following up on our previous post on Population Equivalent (PE), this installment provides additional examples and calculations to illustrate how PE is used to size sewage treatment systems for various types of developments.

Example A: Housing Development

Scenario:

• 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/day & 60 g of BOD/day.

• Occupants per house type:

  • 2-bedroom: 2 persons

  • 3-bedroom: 4 persons

  • 4-bedroom: 5 persons

Calculation:
10 × 2 + 25 × 4 + 10 × 5 = 170 PE

Flow and BOD:

• Flow:
  170 PE × 200 liters = 34,000 liters/day

• BOD:
  170 PE × 60 grams = 10,200 grams/day

Solution:
A BMS BL2000 Blivet Package Sewage Treatment Plant is ideal for this development and provides room for expansion.

Example B: Hotel

Scenario:

• 50 Bedrooms (2 persons per room)

• 100 extra meals/day

• 300 function room guests

• 50 bar-only guests

• 30 non-residential staff

Relevant EPA Figures:

Calculation:

1. Bedrooms:

   • Flow:
     50×2×250=25,000 l/day

   • BOD:
     50×2×75=7,500 g/day

2. Extra Meals:

   • Flow:
     100×25=2,500 l/day

   • BOD:
     100×25=2,500 g/day

3. Function Room Guests:

   • Flow:
     300×10=3,000 l/day

   • BOD:
     300×10=3,000 g/day

4. Bar-Only Guests:

   • Flow:
     50×10=500 l/day

Sewage treatment plants should consistently be sized based on BOD as the biological load must be treated.  Flows can be higher or lower than the BOD, varying 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.

Below, you can see a BMS BL3000 Blivet Package Sewage Treatment System and Balance Tank being installed at a new hotel

Next Topic

In the next post, we’ll dive into Phosphorus.

Questions?

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