Hydraulic Retention Time Calculator
Calculate HRT for wastewater treatment and reactor design optimization
HRT Calculator
🏭 Hydraulic Retention Time Results
Formula: HRT = Volume / Flow Rate
Calculation: 3000.0 m³ ÷ 416.7 m³/h
Status: Suitable for High-Rate Treatment
BOD Removal: 71%
Recommendations
- • Good for BOD removal
- • Consider SRT management
📋 Design Recommendations
Maintain SRT between 1-2 days for optimal performance
🏭 Common Reactor Types & HRT Ranges
Aeration Tank (ASP)
1.5-24 hoursActivated Sludge Process for BOD removal
Anaerobic Digester
15-30 daysAnaerobic treatment for organic matter
Trickling Filter
1-6 hoursFixed-film biological treatment
UASB Reactor
6-24 hoursUpflow Anaerobic Sludge Blanket
SBR (Sequencing Batch)
4-24 hoursSequential batch reactor system
MBR (Membrane Bioreactor)
4-12 hoursMembrane-based biological treatment
Example: Aeration Tank HRT
Given Parameters
Tank Volume: 3,000 m³
Influent Flow: 10,000 m³/d (417 m³/h)
Process: Activated Sludge Treatment
Calculation
Formula: HRT = Volume ÷ Flow Rate
Substitution: HRT = 3,000 m³ ÷ 417 m³/h
Result: HRT = 7.2 hours
Assessment: Suitable for BOD removal (within 1.5-24h range)
HRT Guidelines
< 1.5 hours
Risk of washout
1.5-8 hours
High-rate treatment
8-24 hours
Extended aeration
> 24 hours
May be over-designed
SRT Requirements
Times vary with temperature - higher temperatures reduce required times
Key Formulas
HRT Formula
HRT = V / Q
V = Volume, Q = Flow rate
Temperature Effect
Factor = 1.08^(T-20)
T = Temperature (°C)
SRT/HRT Ratio
Typical: 3-8
Higher for nutrient removal
Optimization Tips
Monitor F/M ratio along with HRT
Consider seasonal flow variations
Balance HRT with energy costs
Maintain minimum SRT for biomass retention
Adjust for temperature effects