What Must Be Confirmed Before Adding Chemicals to an RO System| Insights by AQUALITEK

Why Pre-Confirmation Is Critical

RO membranes are chemically sensitive.
Incorrect chemical selection, concentration, or dosing location can result in:

•Permanent membrane oxidation

•Loss of salt rejection

•Accelerated fouling

•Safety and compliance risks

Therefore, chemical addition must never be done blindly.

Mandatory Confirmations Before Adding Any Chemicals

1. Confirm Membrane Chemical Compatibility

Must Verify

•Membrane material (polyamide, CTA, etc.)

•Maximum allowable oxidant exposure

•Acceptable pH range (continuous vs. CIP)

•Temperature limits

Why It Matters

Many membranes:

•Cannot tolerate chlorine or oxidants

•Have strict pH and temperature constraints

Always check the membrane manufacturer’s chemical compatibility chart.

2. Confirm the Purpose of Chemical Dosing

Clearly Define the Goal

•Scale inhibition?

•Biofouling control?

•Iron or silica stabilization?

•Cleaning support?

Why It Matters

Using:

•Biocide when scaling is the problem

•Antiscalant when biological fouling dominates

…will not solve the issue and may worsen fouling.

3. Confirm Actual Water Quality Data (Not Assumptions)

Required Data

•Hardness (Ca²⁺, Mg²⁺)

•Alkalinity

•TDS and conductivity

•pH and temperature

•Iron, manganese, silica

•SDI / turbidity

Why It Matters

Chemical dosing rates are calculated, not guessed.

Outdated or incorrect water analysis leads to:

•Under-dosing → scaling

•Over-dosing → fouling and membrane damage

4. Confirm Correct Chemical Type and Grade

Verify

•Chemical is RO-compatible

•Free of oxidizing agents

•Approved for potable or industrial use (as required)

•Shelf life and storage condition

Common Mistake

Using:

•Cooling tower chemicals

•Boiler treatment chemicals

•Unknown generic biocides

These are often not membrane-safe.

5. Confirm Proper Dosing Location

Best Practices

•Dose upstream of cartridge filters, not directly before the membrane

•Ensure adequate mixing time

•Avoid dead zones

Why It Matters

Poor dosing location causes:

•Local overdosing

•Chemical shock to membranes

•Uneven protection

6. Confirm Dosing Equipment Functionality

Check

•Dosing pump calibration

•Flow-paced vs. time-based dosing

•Injection quill condition

•Check valves and backflow prevention

A perfectly selected chemical can still fail if dosing equipment is faulty.

7. Confirm No Incompatible Chemicals Are Present

Examples of Dangerous Combinations

•Biocide + reducing agent

•Oxidant + antiscalant

•Chlorine + polyamide membranes

Mixing incompatible chemicals can:

•Generate heat or gas

•Destroy membranes instantly

•Create safety hazards

8. Confirm Emergency Shutdown and Monitoring Are Active

Before Dosing

Ensure:

•Conductivity alarms are active

•Flow and pressure monitoring is operational

•Operators are present or notified

This allows immediate response if abnormal behavior occurs.

9. Confirm Manufacturer and Supplier Documentation

Required Documents

•MSDS / SDS

•Technical Data Sheet (TDS)

•Application guidelines

•Recommended dosage range

Never rely solely on verbal recommendations.

What Should Never Be Done

❌ Never add chemicals without compatibility confirmation
❌ Never increase dosage to “see if it works”
❌ Never mix chemicals in the feed line
❌ Never dose upstream of membranes without mixing verification

Best Practice Summary

✔ Confirm membrane compatibility
✔ Verify real-time water quality
✔ Choose the correct chemical type
✔ Verify dosing location and equipment
✔ Ensure monitoring and safety interlocks

Conclusion

Before adding any chemical—whether scale inhibitors, bactericides, or specialty treatments—operators must confirm compatibility, purpose, dosage, location, and monitoring readiness. Chemical dosing is a precision task, not a trial-and-error process.

Correct pre-confirmation protects membranes, stabilizes performance, and prevents irreversible system damage.