New Technologies for Drinking Water Protection

Water quality monitoring is an important part of drinking water protection. Early identification of changes in quality and possible contamination is the prerequisite for an effective response that reduces or entirely prevents the potential adverse impacts to public health.

Furthermore, the monitoring of drinking water, either at the source or in the distribution system, allows optimisation of operational processes.

Online monitoring of the actual water quality provides valuable information for the timely recognition of changes. Furthermore, online monitoring can provide a wealth of data on the real dynamics of water systems that would ordinarily be impossible to obtain using grab sampling; it provides (near-) continuous information and will miss no quality changes, whereas grab samples provide only snapshots of the water composition on a limited number of points in time.

In drinking water network monitoring, the traditionally measured parameters are Chlorine (free and/or total), Turbidity, pH, Colour and Conductivity. Chlorine is typically to be reported, while the others are to give an overall picture of water quality and eventual problems. With the i::scan, the much more interesting TOC can be added at a small additional cost, and the value of the additional information is enormous.

Online measurement of Turbidity, Organics, Colour and UV254 

The i::scan is a miniature spectrophotometer that is not much more expensive than a good turbidity meter, but can measure up to four parameters online in real-time, all within a single instrument. Parameters that can be measured include Turbidity, Organics (e.g. TOC or COD), Colour and UV254. The i::scan uses a new light source technology which leads to reduced costs and only needs minimal maintenance.

Advanced optics allow the combination of a 180° spectral absorption measurement with a 90° light scatter measurement in a single instrument. This means that turbidity can be measured according to the ISO 7027 - 860nm - and EPA 180.1 - white light – standard (see figure 1).

Vitens is the largest water utility company in the Netherlands, and well known for their innovation culture. They have successfully tested the i::scan, and are going to install a grid of these instruments as a part of an EU funded demonstration project. “The installation of a grid of water quality sensors will allow us to actively manage our water supply distribution networks based on real time status data” says Erik Driessen, innovation manager of Vitens.

There are three different installation options for the i::scan: The i::scan can be mounted submersed in the water, or in a flow cell (bypass installation), or even directly in a pipeline of almost any diameter. 

Monitoring water quality directly in the pipe

To prove that the quality of the water remains pristine all over the drinking water network, because contamination can also occur during distribution for example due to bacterial regrowth or leakage.

s::can offers a simple way to install the i::scan directly in drinking water pipes. There are two different in-pipe fixtures available: A simple version (figure 2 left) for smaller diameters, and a “hot-tappable” version (figure 2 right) for large mains pipes. The hot-tap fixture has been developed in close cooperation with Hawle – a company that has more than 50 years of experience with pipes, fittings and valves. Hawle’s proven technology allows drilling of all kinds of water pipes under pressure, so it is possible to mount the i::scan sensor without any interruption of the water supply.

The hot-tap fixture also contains a shut off valve, which enables to remove the sensor for maintenance without interfering with the pipe flow, and a drainage pipe that can also be used to connect an acoustic “spy” for leak detection.

The nano::station – compact and very cost-effective

The nano::station combines the i::scan with up to three additional sensors for pH, Chlorine (free or total) and Conductivity. All sensors come in one 4-channel flow cell, mounted on a compact panel with all the necessary pipes and fittings. The installation and start-up is plug-and-measure. Also included is a terminal for data visualisation and station management. 

The freely customisable combination of sensors makes the nano::station a very versatile system that can easily be adapted to the needs of specific applications. 

Monitoring at a groundwater protection area

At a ground water protection area North West of the city of Vienna, the i::scan was used to monitor the effects of a construction site on a nearby drinking water well. By using the i::scan, time-consuming and expensive sample collection and laboratory analyses could be minimised. 

Figure 4 shows the measurement results. The turbidity readings ware very stable over time and all the peeks in turbidity could be attributed to one of the following three factors: (i) manual sample collections (a sampling pump was used to gather groundwater for laboratory analyses), (ii) construction activities or (iii) maintenance activities. During the whole measurement period, the turbidity values stayed below the predefined threshold and alarm values. Due to the availability of the water quality data almost in real time, timely countermeasures could have been undertaken if the quality of the drinking water would have been compromised.

The monitored groundwater sometimes had very low oxygen content and conventional grab sampling can be difficult in these situations. With the i::scan the low oxygen did not affect the measurements and no special arrangements had to be taken.

Grab samples were analysed in the laboratory for comparison and a very strong correlation of the laboratory and i::scan values could be observed.