Case Study – Protecting a Water Intake from a Kerosene Spill
The water intake feeds a water treatment plant which is located 300m away.
It is located in a rural area with issues of high Ammonia levels from surface water run off (fertiliser and livestock). The water has wide ranging levels of turbidity dependent upon rainfall. Ambient temperature and flow levels also vary widely due to the geography.
The river is in a steep valley and a major road runs parallel to the river for a long distance, with a high probability that accidents will cause a pollution incident.
The lack of mains supply of gas also means that there are many farms and houses using and storing kerosene for heating, as well as diesel fuel for agricultural vehicles. Environmental contamination from these sources is frequent and usually goes unreported.
The intake is also vulnerable to illegal dumping of petroleum based products.
Unfortunately, the water supply from this site is key to the water company due to the geography of the local area and the lack of an alternative water supply in the event that the treatment works be affected by a pollution incident.
The water company installed a VOC Analyser supplied by Multisensor Systems in 2013 as part of a suite of instruments to protect the intake. It had previously used Multisensor’s products successfully as part of a response to a major spill of kerosene, which threatened the aquifer elsewhere in their region.
The lack of sensitivity to changes in the turbidity of the river water was a key factor in selecting Multisensor’s technology against others, such as optically based systems which are inherently susceptible to false readings and to equipment failure in turbid water.
After a number of months the analyser saw an event which closed the site. The plot from this can be seen below. This event was slow to clear and was due to a spill of kerosene heating oil. The rise in concentration can be seen to the point where the pumps were turned off to prevent damage to the plant. Once the incident had passed the pumps were turned back on and normal operation resumed.
Installation of the instrument was completed without any issues and integration to the customer’s SCADA system via the 4-20mA connection was trouble free once correctly scaled.
The only issue which has been experienced at the site was the cleanliness of the feed to the sample tank, which is required to be cleaned once a month in this application. This was cured by increasing the pressure of the feed to the sample tank, the removal of redundant ancillary components and updating of internal procedures to include the cleaning process.
The instrument has continued to work without interruption since the event and its subsequent planned service.
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