Biofouling of a Well

Poor Water Quality,  Reduced Well Yield, Slime Coatings or Microbiologically Induced Corrosion

Biofouling of a well is a form of biochemical incrustation that involves the creation of a continuous or discontinuous biofilms.  A biofilm is defined as a “microbial growth occurring over a surface in which the individual cells are bound within a common extra cellular matrix of polymeric molecules” (Dullimore, 1987).  Biofouling is one of the five major causes for decreasing well yields and the development of poor well water quality, see Table 1. 



Table1. Bacteria in Groundwater And Influence on Water Quality

Metabolite Process

Result

Anaerobic

 
Fe (III) reducing   Increased Dissolved Iron
Mn (IV) reducing  Increase Dissolved Manganese
SO4 reducing Produces S-2, hydrogen sulfide odors and FeS compounds

 Aerobic

 

Fe (II) Oxidizing

Convert soluble iron to iron oxides (precipitate or colloid)
Fe Precipitate Deposits Fe(III) into biofilm
Mn (IV) Deposit Mn into the biofilm
S-2 oxidizing Form sulfurous slimes
Heterotrophs Transform Carbon to CO2 - Increase Corrosion
  Got a Good Case - Maybe we will Profile On Case Study Page
 

 (Source: Method for Monitoring Fe and Mn, Biofouling in Water Wells, AWWA, 1992.)

 



With respect to well yield, the “biofouling” creates a reduction of well yield, well efficiency, and poorer system performance.  Just like chemical incrustation, the biofouling creates a “thick” discontinuous irregular layer of slimes and biofilms along the wellbore, well screen, piping/equipment, bedrock fractures, gravel pack, and within the aquifer.  These films consist of a combination of amorphous polymeric chains containing metal oxides of iron, manganese, aluminum and other trace metals.  These biofilms may also house or protect pathogenic bacteria, viruses, and protozoan.


Biofouling can cause the following to occur:

1)      Decrease well yield and pump efficiency and ultimately pump failure;

2)      Sudden changes in water quality that adversely impacts the taste, appearance, odor and chemical composition of the water;

3)      Accelerated chemical and electrochemical corrosion that can result in increased metal content, aesthetic and taste problems, and failure of pumps and piping due to corrosion; and

4)      Reduction in the strength of metal casings, well screens, and piping causing leaks and pipe failures.
 

Biofouling can influence the rate of chemical corrosion by producing organic/inorganic metabolites that can lower the pH, increase the concentration of hydrogen sulfide, and increase the ability of the fluid to carry a charge, and create differential “aeration” cells.  The formation of these cells provides the mechanism for electrochemical corrosion or microbiologically induced corrosion (MIC) to occur.

Two conditions are needed for electrochemical corrosion to occur.  These conditions include a difference in the electrical potential of the metal surfaces and a fluid that connects the materials that has a capacity to carry a charge.  Electrochemical corrosion is more commonly associated with galvanic corrosion associated with the use of dissimilar metals, such as the corrosion associated with the connection of a copper pipe to a cast iron pipe.  At the connection between the copper and cast iron pipe, a galvanic or electrical cell is formed.  The copper pipe acts like a cathode and the cast iron acts like the anode.  The cathode area is identified by the buildup or gain of ions and the anode area or pitted area is the loss of ions.

Tuberculation is the most typical form of corrosion.  Tuberculations are knob like mounds of corrosion byproducts that are found scattered over the surface of a corroding material.  Microbiologically Induced Corrosion (MIC) has been recognized to be responsible for 10 to 30% of pipe corrosion and a major cause of tuberculation.

With respect to the health effects associated with biofilms, these films are normally considered non-pathogenic (i.e., not disease causing).  For individuals that are immunocompromised these organisms may act as an “opportunistic pathogen”.  In addition, these biofilms may accumulate trace metals (Fe, Mn, Al, Co, Ni, Cu, Zn, Cd, Sn) and provide a protected environment for pathogenic organisms to flourish.  The slimy biofilms also provide a protective coating that limits the effectiveness of conventional disinfection practices. 


If the odor is stronger in the hot water, we recommend the following:

a. Turn off the system and drain.
b. Allow the tank to refill, but raise the temperature to a level above 140 F.
c. Allow the tank to be set at this level for at least 6 hours
d. Turn off the system and reduce to normal temperature.
e. Allow the tank to refill.


B.F. Environmental Consultants Inc. has completed multiple evaluations and developed remediation systems for problems associated sulfur, iron/manganese, and slime related bacteria and other biofilm management.  First Step - Visual Inspection and Getting the Water Tested - It may be necessary to test for "Nuisance Bacteria and Standard Plate Count" or you can try a shock well and distribution flush using Well Safe Sanitizer.
 

Staining in Dishwasher and Selecting a Detergent
How to Shock Disinfect a Well
Odor Problems, Cause, and Action
Odors in Hotwater and Sulfur (Rotten Egg Odors)
 


 

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