A free, curated reference of the design envelopes our engineers actually use — surface-loading rates, RO pressure and energy figures, sludge cake dryness, and process-selection rules of thumb. Drawn from recognised standards and Reynolds & Bauhm project practice, gathered onto one citable page.
These are typical design envelopes for budgeting and concept design — the starting points a process engineer brackets against the real water analysis, the manufacturer’s curve and the project specification. They are not a substitute for detailed design, but they are the numbers worth knowing before you start. Free to reference; a citation or link back is appreciated.
Choose by particle density, footprint and sludge target
| Parameter | Dissolved Air Flotation (DAF) | Lamella (inclined plate) | Gravity settling |
|---|---|---|---|
| Best for | Low-density solids, oil/FOG, algae | Dense settleable solids, compact footprint | Dense solids, large flows, low cost |
| Surface loading rate | 5–15 m/h | 2–3 m/h (on projected area) | 0.5–1.5 m/h |
| Footprint vs settling | 3–5× smaller | 3–5× smaller (plate multiplier) | Baseline (largest) |
| Typical TSS removal | 80–95% | 85–95% | 50–70% |
| Float / sludge solids | 2–5% (floated) | 1–3% (settled) | 1–3% (settled) |
DAF sizing calculator → · Lamella design calculator → · Full comparison →
| Parameter | Typical value |
|---|---|
| Surface (hydraulic) loading rate | 5–15 m/h |
| Air-to-solids ratio (A:S) | 0.005–0.06 mg air / mg solids |
| Saturator pressure | 4–6 bar |
| Recycle ratio | 6–30% of feed |
| Micro-bubble size | 30–50 micron |
| Dissolved air at 5.5 bar (Henry’s law) | ~90–110 mg/L |
| Expected O&G removal | 85–95% |
Feed salinity sets the whole equipment class
| Parameter | Seawater RO (SWRO) | Brackish RO (BWRO) |
|---|---|---|
| Feed TDS | ~35,000 mg/L | 1,000–10,000 mg/L |
| Operating pressure | ~55–70 bar | ~10–18 bar |
| Recovery | 40–50% | 65–80% |
| Specific energy | ~3–4 kWh/m³ (with energy recovery) | ~0.5–1 kWh/m³ |
| Energy recovery device | Essential (PX exchanger ~95% eff.) | Not required |
| Salt rejection | 99.5–99.8% | 97–99% |
| Design flux | 12–17 L/m²/h | 20–30 L/m²/h |
Containerised DAF/RO configurations → · RO energy recovery →
| Method | Typical cake dryness (% DS) | Notes |
|---|---|---|
| Gravity thickening | 3–6% | Pre-thickening stage, not a cake |
| Belt filter press | 15–25% | Continuous, moderate energy |
| Decanter centrifuge | 20–30% | Continuous, higher energy, enclosed |
| Screw press | 18–25% | Low speed, low energy, low noise |
| Plate-and-frame filter press | 30–40% | Driest cake; batch process |
| Parameter | Typical value |
|---|---|
| Pump suction velocity | 0.6–1.5 m/s |
| Pump discharge velocity | 1.5–3 m/s |
| Erosional velocity (API RP 14E, water) | ~3.9 m/s (C = 122) |
| NPSH margin (available over required) | ≥ 0.5–1 m (or 10–30%) |
| Positive-displacement use | Viscous, shear-sensitive, metering, constant flow |
Free to reference — a link back is appreciated
Reynolds & Bauhm. “Water-Treatment Design Benchmarks & Reference Data.” reynoldsbauhm.co.uk/water-treatment-design-benchmarks
These figures are typical design envelopes compiled from recognised standards (e.g. ASME, EN, API RP 14E, the Hydraulic Institute) and Reynolds & Bauhm project experience, for early-stage design and estimating. Always confirm against your specific water analysis, the manufacturer’s performance data and the relevant code before procurement.
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