Algal bioassays detect modeled loading of wastewater-derived nitrogen in coastal waters of O'AHU, HAWAI'I

Daniel W Amato; Robert B Whittier; Henrietta Dulai; Celia M Smith

doi:10.1016/j.marpolbul.2019.110668

Algal bioassays detect modeled loading of wastewater-derived nitrogen in coastal waters of O'AHU, HAWAI'I

Mar Pollut Bull. 2020 Jan:150:110668. doi: 10.1016/j.marpolbul.2019.110668. Epub 2019 Nov 30.

Authors

Daniel W Amato¹, Robert B Whittier², Henrietta Dulai³, Celia M Smith⁴

Affiliations

¹ Department of Botany, University of Hawai'i at Mānoa, 3190 Maile Way, Honolulu, Hawai'i, 96822, USA. Electronic address: dwamato@hawaii.edu.
² Hawai'i Department of Health, Safe Drinking Water Branch, Uluakupu Bldg. 4, 2385 Waimano Home Road, Suite 110, Pearl City, Hi, 96782-1400, USA. Electronic address: robert.whittier@doh.hawaii.gov.
³ Department of Earth Sciences, 1680 East-West Rd, School of Ocean Earth Science and Technology, University of Hawai'i at Mānoa, Honolulu, Hawai'i, 96822, USA. Electronic address: hdulaiov@hawaii.edu.
⁴ Department of Botany, University of Hawai'i at Mānoa, 3190 Maile Way, Honolulu, Hawai'i, 96822, USA. Electronic address: celia@hawaii.edu.

PMID: 31796237
DOI: 10.1016/j.marpolbul.2019.110668

Abstract

Previous studies indicate coastlines are at risk of wastewater contamination from injection wells, cesspools, and septic systems. In this study, common marine algae were used to ground-truth modeled loading of wastewater-derived N to coastlines of O'ahu, Hawai'i. Macroalgae were collected and/or deployed at 118 sites and analyzed for tissue δ¹⁵N and N %. Wastewater source locations were used to estimate wastewater-derived N in groundwater with the modeling software MT3DMS/MODFLOW. Algal bioassays identified six coastal regions subjected to elevated wastewater-derived N loading. In a case study, submarine groundwater discharge (estimated by ²²²Rn mass balance) was related to wastewater loading from onsite sewage disposal systems (OSDS) and municipal wastewater injection wells in Waimānalo. The highest ²²²Rn-derived SGD rate and N flux were 21.4 m³/m/d and 62.6 g/m/d, respectively. The results of this study suggest that OSDS and injection wells discharge substantial volumes of wastewater and N across broad regions of coastal O'ahu.

Keywords: Cesspool; Hawaii; Nitrogen; Ocean; Ulva; Wastewater.

MeSH terms

Biological Assay
Environmental Monitoring / methods*
Groundwater*
Hawaii
Nitrogen / analysis*
Wastewater*
Water Pollution / statistics & numerical data*

Substances

Waste Water
Nitrogen