Analyse the constituents that may precipitate
Include calcium, alkalinity, sulphate, barium, strontium, silica, pH and temperature, together with the ions needed to check analytical balance. Reuse applications may also require phosphate and process-specific constituents. State whether results are expressed as ions or equivalents and whether sampling occurred before or after chemical additions.
Request relevant cold-water, alternative-well and seasonal scenarios. A single favourable sample may conceal the limiting condition. Every projection needs an explicit recovery and temperature: otherwise two chemical quotations may be addressing different risks while appearing to offer the same service.
Separate deposit-control efficacy from compatibility
Ask which salts the product controls, under which conditions and using which calculation method. Membrane compatibility is a separate check: a compatible chemical may still fail to control the precipitation limiting the plant. Hydranautics explicitly assigns compatibility responsibility for proprietary chemicals to their supplier.
Review interactions with coagulants and iron or aluminium carried over from pretreatment. Increasing dose does not necessarily solve colloidal fouling and may introduce other interactions. Establish commercial concentration, formulation information, traceability and restrictions associated with the intended use of the treated water.
| Check | Useful evidence | Question |
|---|---|---|
| Efficacy | Scaling projection | Which species limits recovery? |
| Compatibility | Applicable supplier statement | Which membranes and conditions? |
| Dosing | Calculation and pump range | Is the intended dose delivered? |
Translate the proposed dose into a dosing system
For an arithmetic example rather than a recommendation, 20 m³/h of feed at 3 mg/L of commercial product requires 60 g/h. If a prepared solution contains 100 g of product per litre, its theoretical dosing flow is 0.60 L/h.
Actual selection needs concentration, density when dosing by volume, dilution stability and the pump’s controllable range. Link dosing to treated flow and detect chemical depletion. Define how the RO responds when the dosing system fails to deliver the required quantity, including low-flow and start-up conditions.
Compare quotations against the same design case
Request the analysis used, allowed recovery, temperature, dose, injection point and unresolved conditions in writing. Compare annual consumption using real operating hours, delivery, preparation and maintenance alongside price per kilogram. Do not attribute greater recovery to a chemical without checking the plant’s other hydraulic and pressure limits.
After implementation, follow normalised performance trends and analyse concentrate where appropriate. If deposits develop, preserve evidence and investigate with the supplier. Switching products without recording conditions makes it difficult to determine whether the cause was chemistry, dosing delivery or an incorrect design scenario.
Common questions
Does antiscalant reduce conductivity?
That is not its function. Dissolved salts remain present and concentrate during separation; the chemical aims to control their precipitation under defined conditions.
Can more chemical allow any recovery?
No. Pressure, concentration, hydraulics and chemical efficacy still impose limits. A higher recovery requires a revised projection and explicitly confirmed operating conditions.