Nematodes as a source of total coliforms in a distribution system

Area of Science:

• Environmental microbiology
• Water quality management
• Public health

Background:

• Recurring detection of total coliforms and atypical coliforms at water distribution system pumps.
• Coliform presence correlated with pump operation and water temperatures above 18°C.
• Co-occurrence of significant nematode concentrations at the same sampling points.

Purpose of the Study:

• To investigate the hypothesis that coliform bacteria are released from nematodes.
• To determine the relationship between nematodes and coliform presence in drinking water.
• To identify the source of nematodes in the water distribution system.

Main Methods:

• Sampling at distribution pump exit points in a North American city.
• Quantification of total coliforms, atypical coliforms, and nematodes.
• Laboratory analysis to recover and quantify bacteria associated with nematodes.
• Tracing nematode origin to water treatment plant sand filters.

Main Results:

• Total and atypical coliform concentrations ranged from 0 to 93.5 colony forming units (cfu)/100 mL.
• Nematode concentrations averaged 12.0/L in 2001 and 17.4/L in 2002.
• Laboratory tests confirmed coliforms (0–27 cfu/nematode) and heterotrophic bacteria (0–643 cfu/nematode) associated with nematodes.
• Nematodes were traced back to sand filters in water treatment plants.

Conclusions:

• Nematodes can harbor coliform and heterotrophic bacteria.
• Invertebrates in water distribution systems may play a role in bacterial contamination.
• Further assessment of potential health risks associated with invertebrates in drinking water is warranted.