on line monitors

A variety of instruments are available for water and wastewater monitoring providing a real-time indication of contamination or specific parameter.

In essence, these devices offer massive advantages over spot-testing (as carried out using test kits etc..) because they can offer good trending data over a period of time. On line analysers provide continuous measurement right through peaks and troughs of the daily and weekly cycle. This can help to identify the best methods for controlling contamination in all sorts of municipal and industrial applications. They can also send alarm signals if contamination thresholds are breached.

Online wastewater monitoring instrumentation can be split into two categories, ‘probes’ and ‘sample systems’. Probes can be deployed straight into the effluent or sample stream. Sample systems usually operate a batch measurement routine and require a sample to be pumped up to an analyser/monitor. The measurement takes place and the used sample discharged back into the sample stream. The advantages of the pump sample system are that ‘wet-chemical’ measurements can take place which are often based directly on standard analytical methods used in laboratories – the advantages of the probe system is that results may be instantaneous (via an optical system or ISE ion-selective electrode).

Either type of instrument requires a cleaning regime of some sort for wastewater monitoring. Probe instruments are immersed in the sample and therefore directly exposed to the waste water. The sample system approach requires that the pump works as needed and that the delivery tubing, and measurement system are kept clean. Pumps are usually worth checking as they are often the weakest link in the measurement system. Effective means of keeping both types of instrument running well are available – it is worth saying that what is effective at one point in a waste water treatment plant cannot be guaranteed to work at any other point with even the same plant.


Waste Water resource centre