Monitoring of dissolved reactive phosphorus in wastewaters by flow injection analysis. Part 2. On-line monitoring system

An automated-flow injection (FI) analyser for the determination of dissolved reactive phosphorus (DRP) in wastewaters is described. The analytical method is based on the formation of molybdenum blue. The limits of detection using a solid-state photometric detector (LED-photodiode) were 0.05 mg P l−1 and the linear range was 0–20 mg P l−1. Details of construction, field-testing (including sample filtration) and validation are given. The analyser proved very reliable during an unattended operational period of seven days. Operational costs were minimised, with low reagent consumption and minimal operator intervention. Data retrieval and analyser status were remotely interrogated by means of a cellular telephone-based communications link. The real-time results from the analyser showed good correlation with those generated by a validated laboratory method.