Input Data
Enter values for domestic generation, return rate, added flows, wet-weather uplift, and wastewater strength.
Formula Used
Domestic Flow (m³/day) = Population × Water Demand × Return Factor ÷ 1000
ADWF (m³/day) = Domestic Flow + Industrial / Commercial Flow + Infiltration
PDWF (m³/day) = ADWF × Peak Factor
PWWF (m³/day) = PDWF + Storm Inflow
Average Hourly Flow = ADWF ÷ 24
Peak Hourly Flow = PWWF ÷ 24
BOD Load (kg/day) = ADWF × BOD × 0.001
TSS Load (kg/day) = ADWF × TSS × 0.001
These equations are practical planning formulas. They are useful for sewer sizing, pump checks, preliminary treatment design, infiltration review, and wet-weather capacity screening.
How to Use This Calculator
- Enter the connected population and average water demand.
- Set the return factor to represent water reaching the sewer.
- Add industrial flow for factories, shops, or commercial wastewater.
- Add infiltration to reflect groundwater entry during dry weather.
- Add storm inflow to represent wet-weather pickup.
- Choose a peak factor suitable for the service area.
- Enter BOD and TSS concentrations if process loading is needed.
- Submit the form and review the result summary and graph.
- Download CSV for spreadsheets or PDF for reporting.
Example Data Table
| Item | Example Value | Unit | Notes |
|---|---|---|---|
| Population Served | 18,500 | people | Base service population. |
| Water Demand | 155 | L/person/day | Average supplied water demand. |
| Return Factor | 82 | % | Water converted to wastewater. |
| Industrial / Commercial Flow | 520 | m³/day | Added non-domestic base flow. |
| Groundwater Infiltration | 180 | m³/day | Dry-weather extraneous flow. |
| Storm Inflow | 640 | m³/day | Wet-weather uplift. |
| Peak Factor | 2.70 | - | Used with ADWF. |
| BOD Concentration | 240 | mg/L | Used for organic loading. |
| TSS Concentration | 265 | mg/L | Used for solids loading. |
| Calculated ADWF | 3,051.35 | m³/day | Domestic + industrial + infiltration. |
| Calculated PWWF | 8,878.65 | m³/day | Peak dry flow + storm inflow. |
| Calculated BOD Load | 732.32 | kg/day | Based on ADWF and concentration. |
Frequently Asked Questions
1) What does this wastewater flow calculator estimate?
It estimates domestic wastewater, average dry-weather flow, peak dry-weather flow, peak wet-weather flow, hourly flow rates, annual volume, and basic treatment loads such as BOD and TSS.
2) Why is the return factor important?
The return factor represents the share of supplied water that actually enters the sewer. Irrigation, cooling losses, and product incorporation can reduce the wastewater fraction.
3) What is the difference between infiltration and inflow?
Infiltration usually means groundwater entering through joints or cracks during dry weather. Inflow is rapid wet-weather entry from roof drains, manholes, or illegal cross-connections.
4) How should I choose the peak factor?
Use a factor that matches your design standard, service population, and sewer system type. Smaller systems often have higher peaking because short-term demand variation is more pronounced.
5) Can this tool be used for treatment plant sizing?
Yes, it is useful for preliminary sizing and capacity checks. Final design should still follow local codes, permit conditions, peaking methods, and detailed hydraulic modeling.
6) Why are BOD and TSS loads included?
Flow alone does not describe treatment demand. BOD reflects organic strength, while TSS reflects solids handling needs. Together they help screen process and sludge capacity.
7) What unit system does this page use?
The page uses liters per person per day for water demand, cubic meters per day for flow, milligrams per liter for strength, and kilograms per day for loads.
8) Should I rely only on this calculator for final design?
No. It is best for planning, comparison, and early design reviews. Final designs should be checked with site data, regulations, rainfall analysis, and detailed engineering assumptions.