Town of Qu'Appelle: Well 5 Enzyme-Based Well Treatment Evaluation

Executive Summary

A field evaluation of an enzyme-based well treatment process was conducted by the Prairie Farm Rehabilitation Administration (PFRA) in partnership with the Town of Qu'Appelle. This applied research project was initiated as part of PFRA's Sustainable Water Well Initiative (SWWI), to investigate new and innovative treatment approaches for biofouled water wells.

Traditional well treatment techniques, previously performed by the Town of Qu'Appelle, had failed to prevent the decline in yield at Well 5. Therefore, the Town expressed an interest in investigating alternate treatment and preventative maintenance methods for sustaining their water well supplies. In 1999, PFRA and the Town of Qu'Appelle field tested a heat-activated treatment process at Well 5 (PFRA, 1999). Prior to applying this treatment process, diagnostic testing indicated that Well 5 was biofouled and had experienced an 84% decline in specific capacity since its installation in 1989. After treatment, the specific capacity of Well 5 increased from 2.5 to 6.5 igpm/ft (imperial gallons per minute per foot) of drawdown, restoring the well to about 42% of its original specific capacity. Although this treatment process was more effective at removing the plugging material than previous well rehabilitation efforts, it was still not able to restore the well to its original specific capacity.

Subsequent laboratory experimentation conducted at the PFRA Technology Adaptation Facility in Regina, revealed that an enzyme-based treatment process also showed promise in improving the permeability of biofouled aquifer material. Therefore, in June, 2002, the Town of Qu'Appelle agreed to collaborate with PFRA to evaluate this alternative treatment method at Well 5. After this treatment was applied, the specific capacity of Well 5 improved from 6.4 to 7.5 igpm/ft of drawdown. However, by December, 2002, the specific capacity had declined slightly and stabilized at about 6.7 igpm/ft of drawdown. These results suggest that there was probably only a limited removal of biofilms and that this treatment was unable to remove the remaining biological material that was plugging the void spaces of the aquifer. A significant amount of biofouling material still appears to be present, restricting the permeability of the aquifer material around the well. Also, microbiological analyses conducted after treatment indicated that there is still a high level of bacterial activity in and around the well.

Well treatment results from Well 5 and other similar treatment evaluation projects indicate that when a biofouled well has experienced a decline in its original specific capacity of more than 40 percent, it becomes increasingly difficult to restore this well to its original condition (PFRA, 1999; PFRA, 2000). Although some of the biofilm and accumulates that plug the void spaces of the aquifer can be removed and additional pathways opened for water to more effectively enter the well, experience has shown that the potential for bacterial regrowth is high. The results of these studies emphasize the need to implement an ongoing monitoring program, along with preventative maintenance procedures, to reduce the risk of premature well failure.

Based on the current study results at Well 5, it is recommended that any future well treatments be designed to deal with the biofouled condition that exists around this well. Also, periodic pump tests should be conducted to monitor any changes in the specific capacity, and regular water chemistry and biological analysis should be performed. These diagnostic procedures will determine if further biological plugging is occurring around Well 5 and will indicate if additional treatments are required to prevent a decline in the specific capacity.