2021-10-27 EMC Agenda item 5-b(i) Identifying wastewater management tradeoffs ... in Kona, Hawaii (RG)

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PLOS ONE Identifying wastewater management tradeoffs in Kona, Hawai'i Funding: Funding forth is project came from the by more than the targeted cesspool conversion option at a fraction of the cost. However, National Science Foundation's Research potential improvements in marine habitat quality only occurred in the immediate vicinity of Infrastructure Improvement Award (RII) Track-1: 'Ike Infrastructure Wai: Securing ovemHawain water Future Award the WWTP, whereas the benefits under targeted cesspool conversion were more evenly #OIA-1557349 and USGS Water Resources distributed along the coast. Research Institute Program grant number G16AP00049 BY5 "Linking watershed and groundwater management to groundwater dependent ecosystems and their linked ecological, cultural, and socio-economic values." The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the 1. Introduction manuscript. Competing interests: The authors have declared Sufficient and targeted wastewater management is a key component in supporting and pro - that no competing interests exist. tecting groundwater dependent ecosystems such as wetlands and spring -fed agricultural sys- tems, and nearshore marine environments around the world [1-3]. Wastewater is a significant threat to groundwater dependent and other coastal ecosystems, including coral reefs [4-5], yet the impacts of wastewater on valued marine ecosystems is rarely accounted for in decision making [7]. An increasing number of jurisdictions have introduced legislation to mandate upgrades of older cesspool technologies to newer, more advanced systems in order to reduce the delivery of nutrients to nearby groundwater aquifers and connected groundwater depen- dent ecosystems [6]. Implementing and operationalizing such legislation requires understand- ing both the benefits of various wastewater management strategies and technologies as well as the differing costs associated with these options. Ecologically, unpolluted submarine groundwater discharge (SGD) is a natural component of many nearshore coral reef ecosystems, and supports native and endemic nearshore species which rely on SGD-influenced habitat for survival. Healthy coral reefs provide a suite of socie- tal benefits to important income and livelihood sectors including by supporting fisheries and food security, and by enhancing recreation and tourism value [8— ]10]. Coral reefs also provide important coastal protection services, which enhances resilience to climate change [11, 12]. SGD delivers cool, fresh, nutrient rich groundwater to nearshore reefs, which drives produc- tivity when taken up by macro and micro algal species, and creates areas of estuarine habitat on which marine plant, animal, and invertebrate species rely in various capacities [8, ]13]. Declines in SGD have been shown to have negative effects on nearshore biota [4]. Worldwide, anthropogenic nutrient loading of SGD has been linked to macroalgal blooms, shifts from coral to macroalgal dominated ecosystems, harmful phytoplankton blooms and eutrophication [5]. Such threats to coral reefs can have devastating impacts on coral reef ecology and the array of ecosystem services provided by these systems [8, 14:]. Hawaii has become an important focal point for wastewater management within the United States due to increasing concern about threats to coral reef ecosystems of high value for tourism, recreation, fisheries, and cultural connection to place [15, 15]. Moreover, the connec- tion between existing wastewater technologies and nutrient loading to the nearshore has also been extensively studied in Hawaii [ 17-23]. There are approximately 88,000 cesspools across the state, releasing over 200,000 in of wastewater per day to the environment [24]. Much of that wastewater percolates into underlying groundwater systems and eventually enters near - shore marine ecosystems via SGD. In response to concerns that cesspools pose a potential environmental and public health risk, the Hawaii State Legislature passed Act 125 in 2017, which states that all cesspools in the State, unless granted exemption, must be upgraded to a septic or aerobic treatment unit (ATU), or connected to a sewer system by January 1, 2050. A Cesspool Conversion Working Group (CCWG) was established in the following year under Act 132 to assist in facilitation of Act 125 [6]. The management scenarios presented in the PLOSONE IIhuttlps://doaa.oirg/n0.t:171/joauirirualll,lpoine,0257125 September8,2021 2/26