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Water Treatment Plant Sizing Calculator

Size a water treatment plant from population, per-capita demand, and peak factors. Estimate basin, filter, and clearwell dimensions.

Inputs

gpd

Results

Design Capacity

5.85 MGD

Estimated Capital Cost

$15,750,000.00

≈ 38 average U.S. homes

Average Daily Flow2.5 MGD
Peak Daily Flow4.5 MGD
Sedimentation Basin Area6,429 sq ft
Total Filter Area781 sq ft
Number of Filters2
Clearwell Volume188K gallons
Annual Operating Cost$945,000.00
Cost per 1,000 Gallons$1.04
Staff Required6
Site Footprint11.7 acres
How to Use This Calculator
  1. Enter Design Population and Per Capita Demand (gpd) — use projected population served and average daily use per person (US typical: 80-100 gpd).
  2. Set Peak Day Factor to account for seasonal demand spikes (typically 1.5-2.5 for most utilities).
  3. Select Treatment Type — 1 = Conventional, 2 = Direct Filtration, 3 = Membrane, or 4 = Advanced (ozone/GAC).
  4. Choose Source Water Quality (Excellent to Very Poor); poorer source water raises the chemical (alum) feed dose used in the cost estimate.
  5. Review Design Capacity (MGD), Average Daily Flow, and Peak Daily Flow to confirm the plant meets projected demand.
  6. Use Estimated Capital Cost, Annual Operating Cost, and Sedimentation Basin Area to support preliminary engineering estimates.

How the result changes with Design Population

Design PopulationDesign CapacityEstimated Capital Cost
1,000,090234.02 MGD$630,056,700.00
3,500,065819.02 MGD$2,205,040,950.00
6,500,0351,521.01 MGD$4,095,022,050.00
9,000,0102,106 MGD$5,670,006,300.00

What each input means

Design Population
Current and projected population to be served.
Per Capita Demand
Average daily water demand per person. US average: ~80-100 gallons per day.
Peak Day Factor
Ratio of peak day demand to average day demand. Typical: 1.5-2.5.
Treatment Type
1 = Conventional (coag/floc/sed/filt), 2 = Direct Filtration, 3 = Membrane, 4 = Advanced (ozone/GAC).
Source Water Quality
1 = Excellent (protected groundwater), 2 = Good, 3 = Average, 4 = Poor, 5 = Very Poor.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Design Population = 25000, Per Capita Demand = 100, Peak Day Factor = 1.8, Treatment Type = 1 = 5 input(s) provided
  2. Calculate Design Capacity
    Design Capacity
    5.85 = 5.85
  3. Calculate Estimated Capital Cost
    Estimated Capital Cost
    15750000 = $15,750,000
  4. Calculate Average Daily Flow
    Average Daily Flow
    2.5 = 2.5
  5. Calculate Peak Daily Flow
    Peak Daily Flow
    4.5 = 4.5

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.

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