1. What is Detention Time?

Detention time (DT) is the theoretical time required for wastewater to flow through a tank at a given flow rate. It's a key parameter in wastewater treatment design and operation in the UK.

2. How Does the Calculator Work?

The calculator uses the detention time formula:

Where:

• \( DT \) — Detention time (hours)
• \( Volume \) — Tank volume (cubic meters)
• \( Flow\ Rate \) — Wastewater flow rate (cubic meters per hour)

Explanation: The equation calculates how long wastewater remains in a treatment tank based on the tank's volume and the flow rate through it.

3. Importance of Detention Time Calculation

Details: Proper detention time ensures adequate treatment in processes like sedimentation, biological treatment, and disinfection. UK regulations often specify minimum detention times for different treatment processes.

4. Using the Calculator

Tips: Enter volume in cubic meters (m³) and flow rate in cubic meters per hour (m³/h). Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What are typical detention times in UK wastewater treatment?
A: Primary sedimentation typically 1.5-2.5 hours, activated sludge 4-8 hours, and secondary clarifiers 2-3 hours.

Q2: How does detention time affect treatment efficiency?
A: Longer detention times generally improve treatment but require larger tanks. Too short DT may reduce treatment effectiveness.

Q3: Is this the same as hydraulic retention time (HRT)?
A: Yes, detention time is essentially the same as HRT in most wastewater treatment contexts.

Q4: What flow rate should I use for variable flows?
A: For design purposes, use peak flow rates. For operational monitoring, use actual measured flow rates.

Q5: How does temperature affect detention time requirements?
A: Biological processes may require longer detention times in colder UK weather conditions.