10.1016/j.watres.2018.03.0432018
bacteria levels are heavily shaped by how we purify and distribute water. Bacteria released from biofilms in the distribution system are especially a big worry for drinking water safety. This study, the first of its kind on a full scale, actually captured and figured out how much each source, like the original water, treated water, and the distribution system, contributes to the bacteria in tap water. We did this by looking at their microbial community “fingerprints” using the Bayesian “SourceTracker” method.
The bacterial community profiles and diversity analyses showed that the water purification process really changes the communities of free-floating bacteria and those attached to suspended particles in treated water. The bacterial communities linked to suspended particles, loose deposits, and biofilm were pretty similar to each other. But, the community of free-floating bacteria in tap water changed depending on where you were in the distribution system. Our microbial source tracking results didn’t find any noticeable contribution from the original source water to the bacterial community in tap water or the distribution system.
Instead, the free-floating bacteria in the treated water were the main contributor to the free-floating bacteria in tap water, making up 17.7–54.1%. The particle-associated bacterial community in the treated water then “seeded” the bacterial community linked to loose deposits, 24.9–32.7%, and biofilm, 37.8–43.8%, in the distribution system. In turn, these loose deposits and biofilms really affected the free-floating and particle-associated bacteria in tap water. This influence varied by location and was affected by changes in water flow. For example, when there were hydraulic disturbances from closer to further regions, the contribution of loose deposits to tap water’s free-floating bacteria jumped from 2.5% to 38.0%, and biofilm’s contribution to particle-associated bacteria increased from 5.9% to 19.7%. So, what does this tell us? We can probably manage tap water bacteria better by picking the right purification process and running it well, plus by cleaning the distribution system effectively.