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Dilution of sewage pollution in the coastal waters of Hilo, Hawaiʻi, USA; an area with high river and groundwater inputs.

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Title:Dilution of sewage pollution in the coastal waters of Hilo, Hawaiʻi, USA; an area with high river and groundwater inputs.
Authors:Nakoa III, Joseph William Paʻakaula
Contributors:Wiegner, Tracy N. (advisor)
Tropical Conservation Biology & Environmental Science (department)
Keywords:Water resources management
Natural resource management
Public health
show 4 moreOn-site Sewage Disposal Systems
Sewage Indicators
Sewage Outfall
Sewage Vectors
show less
Date Issued:Aug 2022
Publisher:University of Hawaii at Hilo
Abstract:Sewage pollution threatens human and ecosystem health, and its presence can be masked by dilution from freshwater inputs or ocean mixing. This project assessed sewage pollution in the coastal waters of Hilo, Hawaiʻi, an area with high freshwater inputs impacted by on-site sewage disposal systems (OSDS) and an offshore sewage treatment plant (STP) outfall. Twenty shoreline stations were sampled from July 2020 to October 2021 for multiple sewage indicators: fecal indicator bacteria (FIB), nutrients, and stable isotopes in macroalgae and nitrate in water, many of which were incorporated into a sewage pollution scoring tool. Rivers and groundwater were assessed as vectors of sewage pollution and sewage indicator values were compared to water quality standards. Nutrient standards were exceeded in all waters, while FIB standards were exceeded in river-influenced areas. River areas had the highest FIB, NH4+, Chl a, turbidity values, and the highest probability of having stations with a medium-level sewage impact. Groundwater areas had the highest nutrient concentrations and groundwater was the dominant source of NO3- to all freshwater-influence groups as indicated by the stable isotope mixing model. Low sewage indicator values and pollution scores at stations with recently confirmed connectivity to OSDS suggest that freshwater is diluting sewage along the shoreline. This study emphasizes the importance of including a variety of sewage indicators to account for variability influenced by area-specific environmental factors, such as high freshwater input or differing hydrogeology, when assessing the influence of sewage pollution on water quality.
Pages/Duration:59 pages
Rights:All UHH dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections: TCBES Theses
Tropical Conservation Biology and Environmental Science

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