Detecting oil, hydrocarbons and pollution in river water

Introduction

In this study, we examine how the MS1200 Oil in Water/VOC/Hydrocarbon analyser has been deployed by water companies across the UK. Specifically, we will show how the instrument has been used to monitor spillages and contamination events at source water points and how this detection has proven beneficial to water suppliers.

We will also include graphs illustrating the responses observed during different events, alongside a discussion of subsequent measures water companies can implement, plus technical details relevant to this application.

Case Study – Protecting a Water Intake from a Kerosene Spill

The water intake supplies a treatment works located 300 metres away.

It is situated in a rural area affected by high ammonia levels from surface water run-off (fertilisers and livestock). The water exhibits wide-ranging turbidity levels depending on rainfall, while ambient temperature and flow rates also vary considerably due to local geography.

The river flows through a steep valley, with a major road running parallel, increasing the likelihood of accidental pollution incidents.

The absence of a mains gas supply means many farms and homes store kerosene for heating and diesel fuel for agricultural vehicles. Environmental contamination from these sources is frequent, often unreported.

The intake is also vulnerable to illegal dumping of petroleum-based products.

This site is critical to the water company because of the local geography and the lack of alternative water sources should a pollution incident impact the works.

In 2013, the water company installed a VOC Analyser supplied by Multisensor Systems to protect the intake. Previous successful deployments of Multisensor’s technology during a major kerosene spill elsewhere in the region influenced this choice.

The lack of sensitivity to turbidity fluctuations was a key factor in selecting Multisensor’s system over optically based instruments, which are prone to false readings and failure in turbid waters.

After a few months, the analyser detected an event that necessitated site closure. This incident, a kerosene heating oil spill, is shown in the plot below. Concentration rose until pumps were switched off to prevent damage. Normal operation resumed once the incident cleared.

Installation was smooth, and integration with the customer’s SCADA system via the 4–20 mA connection was straightforward after correct scaling.

The only operational challenge has been cleaning the sample tank once a month. This was resolved by increasing feed pressure, removing redundant components, and updating internal cleaning procedures.

The analyser has functioned continuously since the incident, with only planned service interruptions.

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Case Study – Monitoring in a Borehole

The borehole is located in an urban area in the South of England, supplying local residents.

The water has high iron content due to local strata, increasing turbidity. Additionally, contamination from hydrocarbon spills, notably from a local fuel retailer, was a concern. VOC monitoring was therefore specified.

The MS1200 was ideal due to its non-contact measurement method and immunity to water condition variations.

Previously, a UV fluorescence VOC system had been used but could not cope with high iron content, which fouled optics and caused rapid failure despite repeated recalibration.

In early 2015, the Multisensor MS1200 was installed and successfully tested with Diesel concentrations up to 20 ppb.

The MS1200 has operated continuously since, with service only required every six months. Its immunity to turbidity and reliable “e-nose” technology make it highly dependable for controlling pumps when VOC levels rise.

The water company has since expanded MS1200 use across other ground and surface water sites.

Case Study – River Intake Protection

This intake is in the East Midlands, supplying a treatment works 1 km away and licensed to abstract 60 million litres annually.

The river has variable turbidity and is used by small leisure vessels, with roads crossing it. It is also vulnerable to illegal petroleum dumping.

Two VOC Analysers were installed in 2011 following exhaustive testing. Multisensor’s technology was chosen due to its reliability in turbid waters.

Few significant events have been recorded, with hydrocarbon levels up to 5 ppb. Monthly cleaning of the sample tank is required. A 2016 event shows a clear peak in VOCs – below automatic shutdown levels but demonstrating sensitivity.

What to do in case of an alarm?

The Multisensor VOC Analyser is designed to alert water companies to contamination events. Options following an alarm include:

  1. Protect the water treatment works
    Automatically stop abstraction pumps and/or divert water to a retention tank or back to the river if necessary.
  2. Investigate the event
    Rapidly determine the source of pollution, whether accidental or deliberate.
  3. Clean-up operations
    For major spills, remediation may include excavating contaminated soil or installing barriers.
  4. Risk assessment
    Analyse the likelihood of similar future events at the same or other sites.
  5. Risk management and reduction
    Introduce exclusion zones, additional monitoring points upstream/downstream, or other mitigation strategies.

Risk assessment should be ongoing as part of continual improvement programmes.

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Unexpected Results with a VOC Analyser

Customers often assume their source water is relatively clean. However, experience across hundreds of sites shows that some abstraction points already have significant background contamination.

Some contaminants may be exotic and not detected in routine analysis, which typically covers VOCs like benzene, toluene, total xylene, trichloroethylene, with tests costing hundreds of pounds. Full chemical analysis, required for complete detection, costs £1,000–£2,000.

Conclusions

Our MS1200 Total VOC monitor is a wide-spectrum detection system enabling water companies to detect pollution events and gain better insight into their abstraction points.

Monitoring mitigates risk; while not every point is spill-prone, many are, and costs can be high.

Using this technology with risk assessment and management plans helps protect water reserves, avoid supply interruptions, asset contamination, fines, and reputational damage.

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