title: Wastewater injection, aquifer biogeochemical reactions, and resultant groundwater N fluxes to coastal waters: Kā'anapali, Maui, Hawai'i.
abstract: We utilize N and C species concentration data along with δ(15)N values of NO3(-) and δ(13)C values of dissolved inorganic C to evaluate the stoichiometry of biogeochemical reactions (mineralization, nitrification, anammox, and denitrification) occurring within a subsurface wastewater plume that originates as treated wastewater injection and enters the coastal waters of Maui as submarine groundwater discharge. Additionally, we compare wastewater effluent time-series data, injection rates, and treatment history with submarine spring discharge time-series data. We find that heterotrophic denitrification is the primary mechanism of N loss within the groundwater plume and that chlorination for pathogen disinfection suppresses microbial activity in the aquifer responsible for N loss, resulting in increased coastal ocean N loading. Replacement of chlorination with UV disinfection may restore biogeochemical reactions responsible for N loss within the aquifer and return N-attenuating conditions in the effluent plume, reducing N loading to coastal waters.
authors.affiliation: University of Hawai'i at Mānoa, Department of Geology and Geophysics, 1680 East West Road, POST 701, Honolulu, HI 96822, USA. Electronic address: fackrell@hawaii.edu.
authors.forename: Joseph K
authors.initials: JK
authors.lastname: Fackrell
authors.affiliation: University of Hawai'i at Mānoa, Department of Geology and Geophysics, 1680 East West Road, POST 701, Honolulu, HI 96822, USA. Electronic address: glenn@soest.hawaii.edu.
authors.forename: Craig R
authors.initials: CR
authors.lastname: Glenn
authors.affiliation: University of Hawai'i at Mānoa, Department of Geology and Geophysics, 1680 East West Road, POST 701, Honolulu, HI 96822, USA.
authors.forename: Brian N
authors.initials: BN
authors.lastname: Popp
authors.affiliation: Hawai'i Department of Health, Safe Drinking Water Branch, 919 Ala Moana Boulevard, Honolulu, HI 96814, USA.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Whittier
authors.affiliation: University of Hawai'i at Mānoa, Department of Geology and Geophysics, 1680 East West Road, POST 701, Honolulu, HI 96822, USA.
authors.forename: Henrietta
authors.initials: H
authors.lastname: Dulai
mesh_terms: D002247:Carbon Isotopes / Q000032:analysis; D058440:Denitrification; D004784:Environmental Monitoring / Q000379:methods; D060587:Groundwater / Q000032:analysis / Q000737:chemistry* / Q000382:microbiology; D054879:Halogenation; D006254:Hawaii; D065186:Interrupted Time Series Analysis; D009566:Nitrates / Q000032:analysis; D009587:Nitrogen Isotopes / Q000032:analysis*; D062065:Wastewater
chemical_list: D002247:Carbon Isotopes; D009566:Nitrates; D009587:Nitrogen Isotopes; D062065:Wastewater
keywords: Anammox; Denitrification; Nitrogen cycle; Submarine groundwater discharge; Underground injection; Wastewater treatment