Hello all
I've faced a problem related to microbial pollution. There are four wells which are dogged in suburbs of a small town (as you can see in satellite pic). Now the well no. 4 is polluted with two types of bacteria: 1- Heterotroph (HCP=1000) & 2- clostridium per fringing (around 50).
According to the investigations, there are some septic wells which are depicted in the photo. The distance between wells is written on the photo. And also there is a septic well in the site for personnel which is quite sealed. According to locals, up to 10 meters deep is a sandy soil.
The question is that how could we find the source of bacterial pollution.
Thanks in advance
Is there livestock? Looks like farming/agricultural area - which typically have many sources of bacteria - wildfowl, other birds, as well as rodents. Is the well head protected? How are you getting sample - may have contaminated sampling supplies? Rule out those factors which are common place.
Thanks peter for your points
As far as I know there no livestock.
The wells are located in a protected fence.
The samples usually take by experts.
Finding sources of groundwater pollution can be very difficult. If you know of possible sources, you may try using fluorescent dye added to suspected source, and using fluorometer and regular sampling to detect for dye trace or increase. It can be a diffult problem that a geologist or groundwater hydrologist may help define a more specific sampling scheme. Pumping from the contaminated well may draw in more contaminant, or may show reduced concentration if contaminant was a spill or possible not continuing source. These can be very difficult to define though.
Clostiridium bacteria are usually anaerob and dead in presence of oxygen. I think that it is better to find another wastewater around the well.
Grid sample if slightly lithified and amenable to auger, at water table if present at reasonable depth, otherwise nominal mid depth in the first instance. U50 undisturbed sample tool, seal aseptic, Lab analyse and krig the result. Usually the spatial dimension, or "pattern" overcomes statistical and other inconsistencies. If that yields result, tighten with a depth dimension on each hole to water table and beyond as its always possible the contaminates comes from further afield and vector.
Dear Bernhard Hochwimmer
Your answer is a little complicated for an amateur. Would you please describe much more.
And also I would be thanks if you refer me to a manual or something like that.
the presence of germs is always linked to the presence of organic matter (the rest of the corpse's food, even by living beings or by their waste). so if you ensure the proper fencing of wells and that of these elements can not access them you think of a water source including discharges or groundwater contaminated by wastewater
I'm wondering if you have shocked the well with bleach to kill bacteria, purge the well then re-test to see if the bacteria is present in the groundwater or is coming from the well itself. Someone more knowledgeable in shocking drinking water wells might be able to help you with this.
Look at the attached link for handbook - it has recommended set-backs and information on well construction. If the well has a crack or is not constructed properly - or is located near any of the listed sources it could be those sources that are contaminating. Look closely at the well head. You can also have a professional with a down-hole video camera scope the well to determine it's condition, and see it there are cracks where groundwater can infiltrate.
Also it could also be something that got into the well like a snake or rodent that is decomposing down in the well. Video camera scoping would identify that possibility also.
http://www.health.state.mn.us/divs/eh/wells/construction/handbook.pdf
Mehrda, apologies delay. My suggestion is based on standard hydro geochemical vectoring we use in mineral exploration to find a source. Any book on that will be ok Kriging is a statistical technique, and can be done on cheap software such as surfer to make contour maps of the results. The surfet maual is great on this, and the company Golden Softwar is also very helpfull with using it. GIS software can also be used eg QGIS is free. Or just contour results by hand on paper is an option. The U50 tube is standard 50mm tube used at the end of a drill rod or directly in an excavation to take an undisturbed sample of soil or soft sediment. A plastic pipe cut in smal lengths will be ok if it can be fixed to a retreive rod of sorts. Finall genetic testing to amplify the bacteria before diagnostic sequence determination may amplify the signal and provide good vectors at distance, but maybe point to multiple sources to unfathom further. GOOD LUCK!
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