Tank volume and HRT.
Hydraulic residence times, solids retention time and the volume formula that turns a process train into tank sizes.
Basis
GB 50014-2021 and HJ 576-2010 give the tank parameters. HJ 577 and HJ 579 are still pending: [to be confirmed with factory]. The extended-aeration range is from the Saudi MEWA guide.
Tank volume and HRT
HRT is the hydraulic residence time; SRT is the solids retention time. V is tank volume, Q is flow and HRT is the residence time.
| Parameter | Value | Source | Evidence level |
|---|---|---|---|
| Anaerobic tank HRT | 1–2 h | GB 50014-2021 | National standard clause |
| Anoxic tank HRT | 0.5–3.0 h | HJ 576-2010 | National standard clause |
| Solids retention time, phosphorus removal as the main objective | 3.5–7.0 d | GB 50014-2021 | National standard clause |
| Anoxic tank and aerobic tank | The standard gives no unified value; the split is balanced against the nitrogen and phosphorus removal targets | GB 50014-2021 | National standard clause, explicitly not given |
| Extended aeration, Middle East | Aeration 18–36 h; MLSS 3,000–6,000 mg/L; SRT 10–30 d | Saudi MEWA guide | Official guide |
| Tank volume formula | V = Q × HRT | General | — |
The tank volume formula is general; the parameter values above carry the evidence levels shown.
How to use and notes
- Use V = Q × HRT to turn a chosen residence time into a tank volume; Q is the flow at the point being sized.
- Size the tank on the peak flow where the tank has to pass the peak, and on the average flow where the process is a biological one designed on load.
- The anoxic and aerobic tank split is not fixed by the standard; it is balanced against the nitrogen and phosphorus removal targets.
- The extended-aeration range is a Middle East convention from the Saudi MEWA guide, not a national-standard figure.
- Parameters for A/O, MBBR, MBR and SBR — HRT, sludge load, carrier fill ratio and membrane flux — have not been verified beyond the national-standard anaerobic and anoxic tank figures.
- Factory confirmation pending: HRT, sludge load, carrier fill ratio and membrane flux for each process, so the chart can be rewritten to the supplied configuration: [to be confirmed with factory].