Algal bioassays detect modeled loading of wastewater-derived nitrogen in coastal waters of OʻAHU, HAWAIʻI. (January 2020)

• Record Type: Journal Article
• Authors: Amato, Daniel W.; Whittier, Robert B.; Dulai, Henrietta; Smith, Celia M.
• Is Part Of: Marine pollution bulletin. Volume 150(2020)
• Publication Date: 2020-01
• Subjects: Cesspool -- Wastewater -- Ulva -- Ocean -- Nitrogen -- Hawaii; Marine pollution -- Periodicals; Marine Biology -- Periodicals; Water Pollution -- Periodicals; Mer -- Pollution -- Périodiques; Publications périodiques; Pollution des mers; Lutte antipollution; Electronic journals; 363.7394
• DOI: 10.1016/j.marpolbul.2019.110668
• Languages: English
• ISSNs: 0025-326X

Abstract

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 Oʻahu, Hawaiʻi. Macroalgae were collected and/or deployed at 118 sites and analyzed for tissue δ 15 N 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 222 Rn mass balance) was related to wastewater loading from onsite sewage disposal systems (OSDS) and municipal wastewater injection wells in Waimānalo. The highest 222 Rn-derived SGD rate and N flux were 21.4 m 3 /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 Oʻahu. Highlights: Onsite sewage systems are sources of wastewater to Hawaiʻi's coastal waters. Marine algae are useful indicators of land-based nitrogen loading in coastal waters. Algal δ 15 N values were positively related to estimates of coastal groundwater N. Groundwater models accurately identified coastal areas impacted by wastewater. Submarine groundwater discharge is a vector for wastewater to coastal ecosystems.