Development and assessment of a fecal bacterial monitoring program to determine the impact of ocean sewage outfall on shoreline water quality
Fujioka, R., C. Fujioka, and R. Oshiro
An innovative monitoring study, based on analyzing water samples at sampling stations near the Sand Island Ocean Outfall for three fecal indicator bacteria (E. coli, enterococci, and C. perfringens), was completed. Monitoring for these bacteria was useful because each is present in wastewater at different concentrations and survives in ocean water environments at different rates. The wastewater being discharged into the ocean via the ocean outfall pipe was documented to contain high concentrations of the three fecal bacteria. The monitoring data were used to assess the movement of fecal bacteria from the ocean outfall to shoreline stations where most people use the water for recreational purposes. Data were obtained to show that the wastewater from the ocean outfall did not surface but remained submerged to be transported away by ocean currents and be further diluted by ocean water. Since the concentrations of fecal bacteria at the Nearshore Stations and at the Shoreline Stations met the current recreational water quality standards, it was concluded that the wastewater discharged from the Sand Island Ocean Outfall was not being transported to the Shoreline Stations to measurably impact on the microbial quality of water there. Nonpoint sources of fecal bacteria can affect shoreline water quality. Instances of elevated fecal bacterial counts at the Nearshore Stations were observed, indicating that the wastewater from the ocean outfall was occasionally being transported to the Nearshore Stations. The difficulty of interpreting a single day of elevated counts and the many complications involved in interpreting monitoring data near ocean sewage outfalls were reviewed.