From duty point to model number, in five steps
Sizing is not complicated. It is a translation exercise: turn "we need to fix this" into a flow, a gas source, a material and an installation point. Most quotation errors come from skipping step one.
The five steps
Fix the three numbers
Flow (m³/h) or water-body volume (m³); water quality (current DO, hardness, COD or oil content, salinity); and temperature. For a cooling loop, size the slipstream at 3–5% of circulating flow — higher hardness pushes it up. For an open water body, size from volume and turnover, not from flow.
Pick the duty, then the series
Aeration duty is sized from oxygen demand. Separation duty is sized from hydraulic flow. These two framings get confused in quotations constantly — always ask which one a supplier is quoting.
Choose the gas source
Air is enough for aeration and for most flotation. Oxygen buys retention time in high-load water. Ozone is for oxidation and disinfection and needs a different seal and off-gas package — see the ozone page.
Fix material and installation
SUS304 is fine on the two smallest CRP models with clean water. Anything with chlorides — seawater, high-salinity effluent, some mine water — starts at 316L regardless of flow. Then confirm the power supply (220 V or 380 V), the available footprint and whether remote monitoring is required.
Write the acceptance test
Target parameter, measurement method, sampling point, duration, and what happens if the result lands between pass and fail. This is the step that protects both sides, and the one most often left out.
One or two models, not a range
If a supplier sends you a table of eleven options, the sizing was not done. The output of this process is a model number, a specific energy figure and a list of assumptions that would change it.
Series quick reference
| Series | Flow | Head | Typical duty | Notes |
|---|---|---|---|---|
| CLW | 0.5–20 m³/h | 18 m | Water-body restoration, lakes, wetlands | Starts at 220 V; 100–300 nm |
| LOT | 1–20 m³/h | 20 m | Ponds, cages, RAS | 220 V up to 5 m³/h; 316L throughout |
| NEO | ≈2–50 m³/h | varies | Multi-gas processes, ozone | Air / O₂ / O₃, online DO, quoted as a range |
| CRP | 5–200 m³/h | 18 m | Industrial wastewater, digesters, municipal | 304 on the two smallest, 316L above |
| FRY | 10–70 m³/h | 30 m | Deep water, reservoirs, ports | Delivers below the thermocline |
| ARFU | 5–200 m³/h | — | Flotation, oil–water separation, DAF retrofit | 94% TSS, 0.18 kWh/m³ |
| OWS | 5–200 m³/h | — | Produced water to <10 mg/L oil | Packaged per project water analysis |
| SiC | per element | — | Filtration after flotation or before RO | 20/50 nm, 300–600 LMH |
Payback, with the formula visible
Annual energy cost = kW × hours/day × 365 × tariff
Payback (years) = installed cost ÷ annual net benefit
Net benefit has four components, and most quotations only count the first:
- Energy saved. Matters most when replacing an old blower or an oxygen supply. Rostein measured 86% oxygen transfer efficiency against 41% — roughly half the energy for the same dissolved oxygen. Measure your existing consumption before you enter a saving percentage.
- Chemicals and cleaning. The main benefit in descaling and flotation projects. Use the last twelve months of purchase orders, not an estimate.
- Capacity avoided. If the alternative was a new basin, the capital you did not spend belongs in the calculation. Meister Cheese avoided a $10 million expansion.
- Compliance value. A consent limit met without a fine is a real benefit, but it is site-specific and we will not put a number on it for you.
What we do not do
- No "payback in three months" claim. With capital equipment and honest baselines, most industrial cases land between 18 and 48 months, and some never close.
- No benefit stacking that double-counts energy saved and capacity gained from the same kilowatt-hour.
- No unverifiable yield multipliers. Where we quote 10–43% yield gains from oxygenated irrigation, the source is the supplier's published agricultural data, and we label it as such.
Price basis: we quote by configuration. Gas source, material and instrumentation move the number more than the model does. For budget planning, give us flow, water analysis and target and you get a bounded range plus the operating cost estimate. Comparable imported systems typically run 1.5–2× the price of Chinese-manufactured equivalents.
Send three numbers, get a duty point
Flow, target parameter, water analysis. That is enough for a model, a specific energy figure and a payback range with the assumptions written down.
Request sizing → Browse the models first