Student Research: Jeff Stewart

An Evaluation of Occupational Exposures to Biological Hazards at Three Wastewater Treatment Plants in Western Washington State


Prior work by the Tulalip Natural Resource Department has documented on going fecal coliform counts in the Tulalip Bay that fluctuated during the wet and dry seasons. The contributing sources of fecal contamination have been unclear over the years; however many suspects have been identified. Among them are human, wildlife, waterfowl, and domestic animals.

Human feces contaminating the Bay may be a result of leaking septic tank, faulty sewer pumping stations or sewer lines. Surrounding the Bay are 6 sewer-pumping stations that are maintained by the Tulalip Utilities. On occasion, these pumps have been found inoperable which presented concerns about overflow of untreated human waste into the surrounding area. Also outlining the Bay are numerous houses, some of which may depend on septic systems. Not surprisingly some of these septic systems may be decades old and require maintenance or replacement to stop undesired contamination issues. One additional source of human fecal contamination for the Tulalip is the sewer treatment outfall located in Possession Sound. The outfall is located outside of the Tulalip Bay; however due to water currents that may be carrying treated effluent into the Bay it is a targeted source. Because of the number of alleged sources, the Tulalip are interested in verifying if human fecal contamination presents a problem in the Bay, and if so, which of the potential sources of human waste necessitate maintenance.

Other potential sources of fecal waste into the Bay are domestic animals such as dogs, cattle, horses and buffalo. Dogs are commonly seen unleashed around the Bay or live relatively near beaches. Currently there are no regulations that demand pet owners to leash and clean after their dogs, thus dogs are allowed to roam freely. As a result domestic dogs may also be inadvertently expelling waste into the Bay Additionally, cattle, horse and buffalo faRMS are located upstream of Tulalip Creek. The extent of this problem is currently unclear.

The Tulalip Tribes' hatchery and fishery department has been raising Chinook, Coho, and Chum salmon over the past decade in order to revitalize salmon populations and runs in the region. O'Neal et al. [1] hypothesized that many wildlife and waterfowl are attracted to the Bay resulting in unusually high fecal coliform loads.

As a result of these fecal contamination issues and subsequent high fecal coliform counts in the Bay, the Tulalip's Natural Resource Department would like to understand the sources of the problem. Identifying the source(s) is necessary to aid in remediation strategies, and therefore; the long-term health of the Tulalip Bay.

The aim of this project was to utilize two microbial source tracking tools to determine the species source of fecal contamination at 17 sites in or near the Tulalip Bay. We used Bacteroides 16s rRNA gene markers and F+ RNA coliphage markers to differentiate between human, ruminant, dog, and animal fecal pollution. This work was conducted with the cooperation of the Tulalip Tribes' Natural Resource department and the University of Washington's Environmental Health Microbiology Lab.