Borewell Water Filter

Karan:

I take it you have multiple users of the same well and pumping system. The water in the well is likely getting drawn down to deep depths on occasion.

It may be that there is a mud seam or some fault in well construction allowing debris in the well.

However, a suspicion I have about the black deposits is a release of material from a biofilm that has built up on the sides of the bore hole and the plumbing. Groundwater contains a lot of microorganism not necessarily of any health concern. Iron bacteria, for example, is common in many wells. Many times these consortium of bacteria form a film that then can create a micro-environment underlying the film and against the casing, open hole, and plumbing. When the well is pumped down these biofilms are exposed and may slough off. The underlying environment of the biofilm is ideal for creating a reduced zone within the well where other microorganisms can thrive. My guess is that sulfate reducing bacteria (SRB) are forming sulfides that then form with a metal like iron to form iron sulfide. This metal sulfide is a black deposit and can be very fine as to pass coarse filtration. Other metals like copper will also form black deposits with sulfide.

The real cure is to control the well itself so that the biofilm does not become a problem and reduced environments do not form within the well. Shocking the well with hydrogen peroxide on some sort of scheduled bases is suggested. Cartridge filtration down to 5 micron may solve your problem. Whole building treatment may also be required.

The owners of the well should have the raw or untreated water from the well tested at an accredited lab for general chemistry, pH, color, turbidity, metal scan (include iron and manganese both soluble and total ), Nutrients like total organic carbon, NH3, NO3, NO2, TKN, total phosphorous. The testing of bacteria to include total coliform, fecal coliform, E. coli, background, and heterotrophic bacteria. I can provide better specifics for testing and sampling if requested.

A well is a complicated water source that requires routine maintenance. It is usually the lack of routines that can lead to problems. View the well as a bio-amplifier of what is happening naturally in the area around the well. The well provides the space for microbial activity to expand and the pumping assures that the microbes are constantly provided with a food supply. If ignored it will eventually reach a point where a problem can appear. Sometimes these problems can be dangerous because biofilms can harbour lots of adverse metals (barium, arsenic, lead, for example). So my best advice is first to sample the well (accredited lab please) and then to shock the well with peroxide to a level of about 700 mg/L.

Hope this helps somewhat.