APHA- Colour

The red dots show measurement locations for colour-, oil- or TOC in condensate.

The American Public Health Association (APHA) compiled a summary of examination procedures for water, wastewater and chemical industry. The APHA- or platinum/cobalt colour is a known procedure for colour measurement in liquids. The measurement unit of the APHA colour is Hazen. A cobalt- platinum- solvent is used as calibration liquid according to ISO 6271. Therefore the range is specified sometimes in mg/l Pt instead of Hazen.

A change in colour is often a good indicator for the final product quality. Therefore it is very important to detect a change in colour immediately. The observation of mixing ratios, dilution factors, decolourisation filters and distillation columns are typical applications. A constant colour value helps to increase plant efficiency and product quality.

Typical applications for measuring the APHA- colour value:

  • Observation of separation in comparative distillation processes

  • Quality control of potable- or wastewater

  • Quality control during cyanide production

  • Iron removal in  hydrochloric acid

  • Monitoring of condensate to possible product leakage

Dual channel single beam absorption measurement

This principle of measurement is perfectly suited to monitor the APHA- colour values.
The photometer model MoniSpec-AD / Messenger operates according to this dual channel principle.
Each MoniSpec-AD colour Sensor is produced to customer specification, optimized for the requested application. Different optical path lengths (OPL), allow realizing the required measurement ranges. Interference factors such as coating of measurement windows, lamp aging, turbidity, etc. are compensated for by the single beam dual channel method. This will reduce maintenance and raise the long term stability of the measurement system.

The transmitter Model Messenger allows the operation of up to 2 sensors at the same time. The Messenger evaluates the absorption turbidity in addition to the colour values. Colour and turbidity can be monitored in parallel
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