Population Equivalent Calculator

Population Equivalent (PE) Calculator

60 (Standard EU/International) 54 (Common in UK) 75 (High load regions) 80 (US EPA Average) Standard value is typically 60g/person/day.

Calculated Load

0 PE

Total BOD Load: 0 kg/day

function calculatePE() { var flow = parseFloat(document.getElementById('dailyFlow').value); var bod = parseFloat(document.getElementById('bodConcentration').value); var standard = parseFloat(document.getElementById('peStandard').value); var resultDiv = document.getElementById('peResult'); if (isNaN(flow) || isNaN(bod) || flow <= 0 || bod <= 0) { alert("Please enter valid positive numbers for Flow and BOD concentration."); return; } // Calculation Logic: // 1 mg/L = 1 g/m3 // Total Load (g/day) = Flow (m3/day) * BOD (g/m3) var totalLoadGrams = flow * bod; var totalLoadKg = totalLoadGrams / 1000; // PE = Total Load / Standard Factor var peValue = totalLoadGrams / standard; document.getElementById('peOutput').innerText = Math.round(peValue).toLocaleString() + " PE"; document.getElementById('totalBODOutput').innerText = "Total BOD Load: " + totalLoadKg.toFixed(2) + " kg/day"; resultDiv.style.display = 'block'; }

Understanding Population Equivalent (PE)

In wastewater engineering, the Population Equivalent (PE) is a parameter used to express the ratio of the total pollution load generated by a specific source (like a factory, hotel, or office) compared to the average pollution load produced by one person in a single day.

Why is PE Important?

Designing a sewage treatment plant (STP) based solely on water volume is often insufficient. Industrial wastewater or commercial runoff might have a much higher concentration of organic matter than domestic sewage. By converting these loads into PE, engineers can accurately size biological treatment units, aeration systems, and sludge management facilities.

The Math Behind the Calculation

The standard measurement for organic pollution is the 5-day Biochemical Oxygen Demand (BOD₅). This represents the amount of dissolved oxygen needed by aerobic biological organisms to break down organic material in a water sample at 20°C over five days.

The formula used in this calculator is:

• Total Daily BOD Load (g/day) = Flow (m³/day) × BOD₅ Concentration (mg/L)
• Population Equivalent (PE) = Total Daily BOD Load / BOD Load per Person (Standard)

Standard Values and Variations

The most widely accepted international standard (European Union Urban Waste Water Treatment Directive) defines 1 PE as 60g of BOD₅ per day. However, this can vary by region based on diet and lifestyle:

Region/Standard	Value (g BOD₅/day)
European Union (Standard)	60g
United Kingdom	54g – 60g
United States (EPA Average)	75g – 80g

Practical Example

Imagine a small food processing facility that discharges 50 m³ of wastewater per day with a BOD₅ concentration of 1,200 mg/L. To find the PE (using the 60g standard):

1. Total Load: 50 m³/day × 1,200 g/m³ = 60,000 grams of BOD per day (60 kg/day).
2. PE Calculation: 60,000 g / 60 g/person/day = 1,000 PE.

Even though the facility has a low flow rate, its high organic concentration means it places the same stress on a treatment system as a small town of 1,000 people.