Coliforms in Groundwater supply 1

[Pearse29]

Hey guys. Looking help with a problem I have. I am an Environmental Engineer installing a potable water supply for a meat processing plant in N.Ireland. We have drilled a borhole and are testing the water for use in cleaning and washing of plant equipment. The water quality standards for potable water (UK&Ireland) recommend that no coliforms be present in the water supply. However when tested, the water is giving results 7 cfu/1000ml for the 1st test and 11 cfu/1000ml for the 2nd test. The owner has went to considerable expense installing the borehole to a depth of 80m through the underlying limestone bedrock. I have suggested that they maybe create a holding tank facility for the grounwater and treat the grounwater with UV/Chlorine, but again this will lead to considerable expense on the clients behalf. I was wondering if anybody had experienced similar problems, and if so how it was overcome. Any help would be appreciated.

 

[semo]

Have you already disinfected the well, pump, and discharge piping?

It is highly probable that the drilling process contaminated the well with coliform. Shocking the well by injecting chlorine into the aquafer then pumping it out through the well pump can bring it back into compliance. It is also possible that it might take more than one disinfection procedure to adequately eliminate the contamination.

It is also possible that the aquafer does contain a contaminated source in which case you have no choice but to install a disinfection system with UV or chlorine/detention prior to using the water.

 

[cvg]

depending on how the well was drilled and cased, it may allow contaminated surface water back into the well, causing the problems. A sanitary seal at the surface plus proper grading and drainage around the well head and a check valve in the piping may take care of some of the problems (in addition to the shocking)

 

[bimr]

Recommend that you try to disinfect the well.

It is not easy to get a clean well. Add chlorine to the well and let it disinfect. There are standard protocols to do the disinfection.

Then you need to run the well to waste until it cleans up. It may take as long as a week to clear the well. You will have to run the well at maximum flow capacity to clear it.

I have seen where people run the well intermittently and it never clears out.

 

[waterequipments]

If we are talking here of coliform issue, the fastest and cheapest way is to use UV or in line ozone.

However if ozone will be used, it is important to determine the quality of raw water so that we may know if there are presence of elements that might oxidize and thus affecting the quality of water once discharge to the system.

It will be very practical to use the UV, just determine the flow rate and and multiply it by 1.5 so that you will use a unit higher than the flow rate for purposes of having a dose higher than 30,000 micro watts seconds per squared centimeter.

With that, we can be assured than no coliform will survive in the water.

 

[cvg]

waterequip
treating the pumped water is not really the solution to the problem, it is sanitizing the well and keeping it that way. You can't UV the well.

 

[waterequipments]

Yup,I understand your point,what I am trying to discuss is that, you use the UV at the discharge point of the pump just to be sure that micro organism is eliminated.

If you disinfect the well, that is really perfect, however there are cases wherein the well itself are always contaminated due to its poor location.

Sometimes well is near the septic tank, sometimes there are inadequate drainage for human and animal waste and as a result said well is always contaminated even though you have conducted a disinfection process.

Just want to share with you an incident here in the Philippines, in the province of Batangas wherein the piggery is situated at the top of the mountain and just below is a water reservoir being used by the local water district to supply water within the town.

When found contaminated, they used strong dose of chlorine but the continuous flow of animal waste from the top were using up all the chlorine dose thus resulting to the breakthrough of contaminants.

As for your info, that particular town in Batangas was not that progressive and the water district can't afford to sustain large amount of chlorine since it will just add up to the water bills of the town people.

To practically solve the problem, what the water district did was to use the regular dose of chlorine and used a UV to solve the problem and it was successful.

Sometimes, we have to be versatile in dealing with different problems, at the end of the day, what matters most is you were able to deal with that problem.

There are times, especially here in the Philippines wherein you will be forced to deviate from the technical designs due to some financial considerations, politics and other situational problems.

We Filpinos are always creative in order to deal with different problems coming our way.

 

[bimr]

Interesting story. Would not the moral of the story be that people should be following recognized industry standards, law, and regulations? And the word "creative" in that mix of words.

I have been to Batangas City several times and my understanding is that while the laws and regulations are in place, the laws and regulations may not be properly enforced until a problem occurs. Then the hammer will fall.

In the story that you describe, the chlorination should be considered as only an emergency measure until the problem was resolved.

If a well is contaminated and can not be disinfected, then the source of the water is considered to be equivalent to surface water. That is what the ground water rule is all about.

The recognized standard treatment for surface water at the present time is filtration and disinfection, not just disinfection.

With all due respect, I would not want to be involved in a situation where someone's health may be compromised by inadequate facilities.

 

[waterexpert]

Hi Pearse,

I think you will find that the NI Environment Agency will get very upset if you start putting chlorine into their aquifers. It might be different overseas, but in the UK this is highly unlikely to be allowed. Putting anything into the water environment is very tightly regulated.

Assuming that your sampler understands how to avoid contaminating the sample, any coliform contamination from the well drilling operation is likely to be quite shortlived, as coliforms will not live for that long under groundwater conditions.

Of course meat processing operations can produce wastewater rich in coliforms, the source of the coliforms in the aquifer could be leaking sewage pipes. If the contamination has got to 80 m down, it would seem quite serious!

I'd suggest making sure that there is no sample contamination, and if contamination is proved, tracing and eliminating the cause as a priority. Contamination of the aquifer with coliforms is a criminal offence(as is injecting it with chlorine).

Regards
Seán Moran

http://www.expertise-limited.co.uk

 

[Pearse29]

Thanks Sean.

Yes I was aware of the constrainits of chlorination. I have recently had problems with desposing of chlorinated water from a pipeline on another job, and am aware of the NIEA regulations surrounding surface and groundwater. Dont worry, wasnt considering this as an option.What i thought initially was to pump GW to the surface and treat the water in a small holding tank/facility (similar to the pump and treat remediation used in GW/land contamination projects)

However, I do think that the contamination might be from the leakage of the fowl sewer, or altenatively there has been slurry recently sprayed on nearby agricultural land above the acquifer, which may be the source of the coliform contamination.I was going to suggest leaving the well for a couple of weeks to rule out intial contamination from the drilling of the borehole and the addition of slurry. After that time we could conduct another test for coliforms. If contamination still exists, it might be an idea to start investigating the cause of the contamination via a drainage survey (dye test,CCTV)

 

[bimr]

waterexpert,

As you will see from the links below, disinfection of wells with chlorine is common on both sides of the big lake:

http://www.sepa.org.uk/water/ground...205f21-15d1-46ad-8e5f-d081123c1e9a&version=-1

http://www.herefordshire.gov.uk/docs/ehts_cleansing_disinfection__of_private_water.pdf

"The method of disinfection should be in accordance with BS6700 and the following is a typical method acceptable to Northumbrian Water."

http://www.nwl.co.uk/Guidance_note_05_-_disinfection_of_existing_spring_supplies.pdf

The chlorinated water ia flushed out of the well and disposed safely to drain (not to a watercourse) until the
background of the chlorine reaches that of wholesome water.

Not sure where you are getting your information on disinfection.

 

[waterexpert]

Just to be clear, I am saying that putting chlorinated water into any aquifer, whether that be groundwater or surface will be frowned upon.

I have been engaged for eight years to give advice on these matters by the UK government, but things do change, so I have spoken to the NIEA this morning. They have confirmed that my understanding is correct. Basically discharging anything to groundwater without the local EA's sayso anywhere in the UK is a no-no. Call them on 028 92623100 for confirmation.


The legal situation in the UK water field is fast-moving, and differs between autonomous regions. The SEPA document linked to is out of date, and in any case only covers Scotland, which has different laws to Northern Ireland. The other documents are from private water companies and local councils, rather than regulators, and in any case make no mention of putting hypochlorite into the aquifer. Neither of these bodies are in any case responsible for protection of water resources.

Regards
Seán Moran

http://www.expertise-limited.co.uk

 

[bimr]

Chlorinating a well to achieve disinfection is not the same thing as discharging into an aquifer. Typically, a few gallons of bleach are dumped into the well and allowed to sit for a day. Then the well is pumped to waste until the well clears.

Look in up in Groundwater and Wells by Fletcher G. Driscoll.

My understanding is that 95% of the population in the UK is on public water supplies and so you may not be familiar with wells. Maybe you call them boreholes. Suggest you talk to a local borehole driller to clarify the matter.

Did not know that you are in Ireland, so I will give you some links there as well:

http://www.waterfordcoco.ie/en/serv...rinarypublications/How Well is Your Water.pdf

1. All new wells should be disinfected after drilling.

http://www.briodydrilling.com/pollution2.html

http://www.gsi.ie/Programmes/Groundwater/FAQ.htm#gw8

 

[waterexpert]

This is why I clarified what I was talking about in my previous post, as confusion seems to have arisen. I was replying to the person who suggested "shocking the well by injecting chlorine into the aquifer", rather than you, Bimr.

This is why I said "the NI Environment Agency will get very upset if you start putting chlorine into their aquifers". Of course new abstraction systems for potable use should be disinfected, but chlorinating the aquifer as suggested previously is not permissible.

Abstraction of more than 10m3/d of water from an aquifer for any purpose will require an abstraction licence to be obtained from EANI. If they are agreeable to granting such a licence, they will advise you on what they consider to be acceptable in this area. They have groundwater vulnerability maps, and consequently apply different degrees of caution in different areas. In some areas they will not be likely to allow you to even drill the hole.

Incidentally and perhaps confusingly to those far away, Ireland is not part of the UK, and Northern Ireland is. They consequently have different laws, so Irish references are irrelevant.

Regards
Seán

http://www.expertise-limited.co.uk

 

[bimr]

I am sure that most readers assumed that "shocking the well by injecting chlorine into the aquifer" was a "figure of speech", not a literal meaning of the words. Semo is one of the experts on this forum.

 

[cvg]

bimr - agreed - "shocking the aquifer" didn't occur to me to be a literal expression. it would be difficult to "inject" anything into the aquifer - this would require an injection pump and special well design. It really is not an off the shelf item...