A comparative study on methods to detect urban pollution

Polluted urban creeks can affect the aquatic ecosystem and the human health of the community. Raw sewage entering a water system, either directly or via a leaking pipe, can spread pathogens such as Vibrio cholerae and Escherichia coli. Monitoring by regulatory agencies may be inadequate, so testing for sewage leaks by community organizations can be beneficial for locating systems that are in need of repair. Various methods were tested to compare their effectiveness in detecting sewage pollution and feasibility for a community group to use the methods for regular monitoring. Sausal Creek provided a good urban model because a sewage leak in the mid-stretch of the creek has degraded the water quality downstream. Two sites were chosen upstream from the leak and two downstream. At each site ammonia, dissolved oxygen, pH, conductivity, temperature, flow rate, total coliforms, E. coli, and insect abundance were measured. E. coli levels increased from a geometric mean of 1500 MPN at site 2 upstream from the point source to 22,000 MPN at site 3, creating an environment 50 times above the EPA objective. Ammonia and dissolved oxygen were also found to be effective on-site indicators of the sewage pollution, but may not be exclusively caused by sewage pollution. The bacterial analysis is an excellent indicator, but due to the necessity of laboratory facilities would probably not be suitable for most community groups. A cross-referencing plan of measuring ammonia, dissolved oxygen, and insect abundance is recommended to efficiently monitor an urban creek for sewage pollution. The observed recovery distance indicates that monitoring sites should be one kilometer or less in spacing to ensure that point source pollution is detected