Borehole Treatment for Potable Supply

[Pearse29]

I am an environmental engineer currently carrying out an investigation at a Radar Tower in Cork, Ireland. The site has its own borehole and is currently using this borehole to feed the site with a municipal water supply. Monthly testing of the Potable water supply has presented levels of T0C 50.5 mg/litre and VOC of 8.1 mg/litre. We have stopped the use of this water supply until the borehole has been remediated and water levels re-tested. Previously I have used simple treatment systems comprising of sand and activated carbon to remove hydrocarbon (TPH, PAH)contamination from ground and surface water. Given that this is the only water supply on site (5 miles to the mains connection) I was wondering if there was a filtration system or unit on the market that could be purchased that would remove the TOC AND VOC contaminants and allow the water to be used on site (without expensive pump and treat remediation). We are basically looking at an alternative low cost option to the exepensive remediation process. The site is an extension of Cork Airport and has frequent fire drills etc on site. I think the contamination is coming from the fire water entering the groundwater and causing these high levels. I was just wondering if anybody had used an alternative filter/treatment option.
Any help suggestions greatly appreciated.

 

[bimr]

Yes, there are available treatments to clean up the water.

In order to treat the water, you need a chemical analysis of the water to determine the contaminants. The need to know what contaminant is present in order to select the water treatment equipment.

No, the contamination is probably not from the fire water. Fire water should not contain organic contamination.

If in fact the fire water is draining into the aquifer, then you will need to filter and chlorinate the well water.

 

[Pearse29]

Yes I have asked the lab for a full breakdown of contaminants to identify the source contaminants. Given the high levels of VOC's I have linked this to the fire drill exercises carried out on site (i.e. they set fire to old buses and use these as fire drill exercises/simulation for the airport fire service). I linked this to the contaminantion due to the fact that petrol/diesel maybe be contaminating firewater and entering the sub surface acquifer from which the water supply is drawn. This is not to say that there is not an alternative source of contamination on or surrounding the site, but at this early stage the firewater would seem the most likely option.

There is a 9 cubic metre holding tank on site which retains extracted groundwater for use on site (toilets/showers etc). I was thinking of connecting a treatment system (Cyclesorb - containing GAC) before the holding tank and then testing the water again from the holding tank after treatment.

 

[ekolog16]

bimr - This may be a good post for the "soil/groundwater environmental engineering" forum. This is a common problem.

GAC should be able to remove most VOCs from your wells, your vendor should be able to assist you with sizing the carbon vessels and also sizing the carbon to figure out the necessary flow rate.

I've worked with a similar issue with VOCs (BTEX) contamination into a potable groundwater well due to a poorly installed seal causing mixing of the contaminated upper unconfined aquifer with the clean confined aquifer below. GAC filters were installed and worked well at first. After running into various "challenges" associated with the filters, a new well was finally installed and sealed according to the regulations. This well water was non-detect for all VOCs including BTEX.

From a remediation standpoint, this is where it would be beneficial to get a better understanding of the groundwater contamination and hydrogeology which is a substantial investment in itself but could tell you where to put a new well.