Bacteria was present at lower populations in most of the other wells tested, suggesting that biofouling may be at an earlier stage in those wells. Although biofouling occurs at varying rates in different wells, evidence to date suggests that biofouling is progressive and will eventually occur in most of the wells in the study area. Sulfate reducing bacteria is the dominant bacteria type in the study area, although iron related bacteria and total aerobic bacteria are also present. All of these bacteria cause clogging, corrosion, odours, and other problems. Well replacement due to performance deterioration becomes increasingly likely after 15 years.
Most wells appear to show very few symptoms of biofouling for the first five years.
A reduction in yield is likely occurring in all of the biofouled wells located within the study area. Owners of low yielding wells are likely the first to notice a reduction in yield. Owners whose usage is much less than the well's capacity would likely not notice a gradual decline in yield, unless they are carefully monitoring the well. The adjacent figure summarizes observations in one well. All seven of the wells were biofouled by very aggressive sulfate reducing bacteria.