Wastewater Calculator
Understand pollutant loads. Visualize your treatment target.
Flow & Treatment Inputs
Treatment Summary
Based on 500 m³/day and 120 mg/L
54.0 kg/dayLoad removed
12.0 mg/LEffluent concentrationMass Balance
Influent = removed + effluent
Scenario Assumptions
Equal influent and effluent flow · steady daily averages.
BOD₅ is oxygen demand, not a direct measure of sludge mass.
500 m³/day · 120 mg/L · 90% target removal
Treatment Process Visualizer
90% removal scenarioCalculation & Worked Example
Paired representative flow and concentration are required. Products of separate averages can differ from a flow-weighted load when conditions vary.
Frequently Asked Questions
What does this wastewater calculator calculate?
It estimates a selected parameter's daily influent mass load from flow and concentration, then applies an entered removal target to estimate remaining load. It is not a treatment-kinetics or permit-compliance model.
Which values should I enter?
Enter representative daily flow, matching influent concentration and your removal scenario. Choose the correct parameter and units. BOD₅ and COD express oxygen demand; TN and TP should be reported consistently as N and P.
What formula does this calculator use?
Influent load in kg/day = flow in m³/day × concentration in mg/L ÷ 1000. Removed load = influent load × removal fraction. Effluent load = influent load × (1 − removal fraction). At equal flow, effluent concentration follows the same remaining fraction.
Why might my result differ from another source?
Check US versus Imperial gallons, daily versus instantaneous flow, oxygen-demand versus solids parameters, density assumptions and rounding. Actual plant results also depend on sampling, changing flow and concentration, process performance and the applicable reporting method.
More questions (8)
Does the result update automatically?
Yes. Valid input changes update the summary, mass balance and schematic. Calculate refreshes the same model; Reset restores the 500 m³/day, 120 mg/L BOD₅ and 90% example. Copy exports current valid results.
How are flow units converted?
1 L/s = 86.4 m³/day. US MGD means one million US gallons per day; 1 US MGD = 3785.411784 m³/day. Changing the unit preserves physical flow.
Are ppm and mg/L always interchangeable?
No. ppm here means mg/kg. Concentration in mg/L equals ppm multiplied by liquid density in kg/L. They have the same numeric value only at a density of 1 kg/L, approximately appropriate for dilute water. Density is ignored in mg/L mode.
Do the parameter cards change the concentration?
No. Cards select BOD₅, COD, TSS or nutrients and retain your numeric inputs. The nutrient selector distinguishes TN from TP. Each removal target is user-entered, not an assumed universal treatment efficiency.
Is removed load the same as sludge production?
No. BOD₅ and COD removal is a reduction in measured oxygen-demand load, not necessarily a mass of sludge. Biomass yield, solids capture, gas production and other balances require additional models and data.
Does the diagram predict stage-by-stage treatment?
No. The equipment is a conceptual treatment train, not a design for every pollutant or facility. Only overall influent, removed and effluent quantities are calculated. Equipment water colors are illustrative and do not measure clarity, toxicity or pathogens.
What if influent and effluent flows differ?
This model assumes equal flow. If actual effluent flow differs, effluent concentration requires that separate flow and a justified mass-removal assumption. Rainfall, evaporation, sludge withdrawals and side streams can change a real balance.
Can this establish discharge compliance or safe water?
No. Compare correctly sampled and reported results with the actual permit and applicable limits. Pollutant removal alone does not establish disinfection, toxicity reduction or drinking-water safety. A 100% scenario is arithmetic, not a guarantee of detection-free effluent.
Sources & References
US Environmental Protection AgencyECHO · Pollutant loading calculations
Water Environment FederationWastewater Treatment Fundamentals · Operator education
Educational mass-balance scenario · No institutional endorsement or compliance certification
Calculate daily pollutant mass load from flow and concentration, and explore a user-entered removal scenario with a live treatment schematic.