Industry
Instrument selection for boiler feed, cooling water, process water and effluent in industrial plants.
In short
Industrial water control is a titration and electrochemistry problem before it is a spectroscopy problem: hardness, alkalinity, chloride, pH, conductivity and dissolved oxygen cover most operating limits. Ion chromatography and atomic absorption are added when the programme tracks individual ions or corrosion metals, and a laboratory COD analyser covers the discharge permit.
The routine tasks behind a typical quality programme, the parameters involved and the instrument group that covers them.
| Measurement task | Parameters / range | Typical method | Instrument group |
|---|---|---|---|
| Total and calcium hardness | 1–500 mg/L as CaCO₃ | Complexometric titration | Potentiometric titrator |
| Alkalinity (P and M) | 10–500 mg/L | Acid titration to fixed endpoints | Potentiometric titrator |
| Chloride | 5–500 mg/L | Argentometric titration | Potentiometric titrator |
| pH and conductivity | pH 0–14 · 0–200 mS/cm | Direct immersion | pH / conductivity meters |
| Dissolved oxygen | 0–20 mg/L | Electrochemical or optical | DO meter |
| Turbidity / suspended solids indicator | 0–1000 NTU | Nephelometry | Turbidity meter |
| Phosphate and silica for treatment control | 0.01–20 mg/L | Colorimetric | Spectrophotometer |
| Iron and copper as corrosion indicators | 0.01–5 mg/L | Colorimetric or flame AAS | Spectrophotometer / AAS |
| Anions in make-up water | 0.01–100 mg/L | Ion chromatography | Ion chromatograph |
| Effluent COD | 10–1500 mg/L | Digestion and colorimetry | Digestion block + colorimeter |
Workflow
Most results are decided before the instrument is switched on. These are the steps where laboratories usually lose accuracy.
The treatment programme, not the catalogue, defines the ranges and the alarm levels.
A sample taken downstream of dosing answers a different question from one taken at the feed.
A 5 mg/L chloride limit and a 500 mg/L limit rarely need the same technique.
A single result is a data point. The trend is what the plant acts on.
Laboratory and online values diverge for reasons worth understanding, not for reasons worth hiding.
Start from a complete configuration rather than a single instrument: the supporting units decide whether the workflow runs without interruption.
Primary configuration
Hardness, alkalinity and chloride by titration with an electrochemical endpoint, which takes the colour judgement away from the operator.
Batch titration suits a rounds schedule; a fully automated configuration is a separate decision.
Primary configuration
pH, conductivity and dissolved oxygen for the daily control rounds at the bench.
Field readings need the portable M9 or MIS1000 instead.
Primary configuration
Turbidity checks on clarified water and final effluent.
Not a suspended-solids method on its own; gravimetry still decides the reported value.
Supporting
Anion tracking in make-up and boiler water where several ions must be separated.
Overkill if the programme only needs chloride by titration.
Supporting
Iron, copper and other corrosion indicators at mg/L levels.
Trace work below flame limits needs the graphite furnace version.
Supporting
Effluent COD for the discharge permit, using the same digestion workflow as a municipal laboratory.
Chloride-rich effluent needs the appropriate reagent set and dilution.
Entry / alternative
Portable pH and conductivity for plant rounds and cooling towers.
Benchtop calibration is still required for the meters to agree with each other.
Method detail, common errors and configuration choices, written for this workflow.
Application note
How to split water-treatment measurements between titration, electrochemistry and the plant, and why laboratory values and online readings…
Application note
Why online process readings and laboratory results answer different questions, and how to build a verification schedule that…
Application note
A sampling and measurement framework for cooling and boiler systems: control limits, the parameter set, sampling points, and…
Industrial water laboratories are judged by uptime, not by detection limits. The measurements that protect a boiler or a cooling circuit are the ones taken every shift, by an operator who has other duties — and that fact should drive the instrument choice more than the specification table does.
Titration with an electrochemical endpoint is the workhorse. Hardness, alkalinity and chloride are all volumetric methods, and moving the endpoint decision from a colour change to an electrode removes both the eyesight variable and the argument about the last drop. One titrator with stored methods usually covers a plant that also measures pH and conductivity.
Where the laboratory and the plant disagree, the useful question is not which number is right but what the two measurements represent. Online conductivity tracks a flowing stream at temperature; the laboratory sample is a cooled, transported aliquot. Documenting that difference in the method is worth more than another decimal place on the certificate.
Industrial water laboratories support a control loop, so online readings and laboratory verification should be designed together. Define sampling points, temperature, preservation, target parameters, reporting limits and the time from sample collection to result.
The quotation should show how electrochemistry, titration, spectroscopy, ion chromatography and elemental analysis fit the plant workload. It should also state the local installation, training and maintenance route.
Short answers; send the details of your method for a definite reply.
Online sensors sit in flowing water at plant temperature; laboratory samples cool, degas and can pick up contamination on the way. Compare at the same temperature and with the same cell constant before treating either value as the reference.
Yes. All three are volumetric methods; what changes is the reagent, the electrode and the calculation. A potentiometric titrator stores each one as a program.
Only if the programme separates several anions. For chloride and alkalinity alone, titration is faster and needs less infrastructure.
Follow the plant procedure or the method you report against. In practice, a daily check with fresh buffers costs minutes and catches the failures that cost days.
Both are colorimetric and belong on a spectrophotometer. They are treatment-control measurements, so the reading frequency follows the dosing schedule.
Let’s talk about your application
Send your matrix, target parameters and reference method for a configuration review.
