Life cycle environmental and economic impacts of nutrient management in small community lagoon wastewater systems.

Excess nitrogen and phosphorus discharges from wastewater lagoons pose persistent challenges for small communities, potentially contributing to eutrophication, and regulatory non-compliance. While lagoons remain popular due to operational simplicity and cost effectiveness, they often achieve limited nutrient removal relative to some alternative technologies. This study evaluated nine nutrient management scenarios for small community lagoons in the U.S. using life cycle assessment and life cycle cost analysis. Scenarios included a baseline clay-lined facultative lagoon, a membrane-lined facultative lagoon, an aerated lagoon with maturation pond, and six aerated lagoon-maturation pond configurations with either biodomes, iron-dosed upflow reactor, packed-bed biofilm reactor, moving bed biofilm reactor, constructed wetland, or an algal pond. Environmental impacts were assessed as global warming potential (GWP) and freshwater and marine eutrophication potential (FEP and MEP, respectively), while economic performance was measured as present worth of costs (PWC) over a 20-year system lifetime. Baseline lagoons were cost effective ($0.20-$0.30/m3) but exhibited the highest GWP (~3 kg CO2 eq/m3), FEP (~0.015 kg P/m3), and MEP (~0.009 kg N/m3). Packed-bed reactor and iron-dosed upflow reactor scenarios achieved 70% reductions in both FEP and MEP, with moderate GWP (0.8-1.0 kg CO2 eq/m3), though at high costs ($0.86-$1.19/m3). Sensitivity and uncertainty analyses identified effluent nutrient concentrations, design flow, and capital costs as dominant factors influencing outcomes. Overall, this study offers a robust framework for comparing treatment alternatives beyond upfront costs alone, guiding the selection of environmentally responsible, economically viable, and locally appropriate nutrient management solutions for small communities.