Microbial Source Tracking in Two Southern Maine Watersheds: Executive Summary for Merriland River, Branch Brook and Little River (MBLR) Watersheds

摘要

This document is a research project designed to identify more accurately the sources of fecal contamination in areas that have experienced persistent and elevated levels of bacteria. Various types of bacteria have long been used as indicators for assessing the quality and safety of water for its many uses. Bacteria provide convenient measures of water pollution because they are often associated with nonpoint and sewage pollution sources, and they are generally easy to count. Depending on the water body and its intended use, bacterial indicators have been selected and standards developed that are used to assess the risk of human illness as a result of ingestion or contact with the water body. For example, drinking water standards call for no detectable levels of coliform bacteria, which are indicators for the possible presence of disease-causing organisms. These bacteria originate from the intestinal tracts of mammals (including humans) and birds, and can also be found in soil. Fresh water swimming beach standards, on the other hand, allow for up to 235 organisms per 100 mL of water sample for the indicator organism E. coli. Similar standards have been developed for marine waters for both swimming and for shellfish growing area classification. While the use of these bacterial indicators provides a basis for evaluating water quality, conventional test methods are not specific enough to make conclusions about the sources of the pollution.