Lagoon wastewater systems are widely used in small communities because of their low cost and operational simplicity but often fail to meet limits for ammonia, total nitrogen, and total phosphorus, causing eutrophication, greenhouse gas emissions, and regulatory challenges. This research advances sustainable nutrient management for lagoon systems through three integrated studies. A systematic review of 1,003 peer-reviewed papers (1968–2024) assessed nutrient management technologies suitable for lagoons. These were classified by process type, nutrient target, installation location, and development phase. Biological processes dominated (79%), while hybrid systems showed strong potential. A Suitability Index (1-100) integrating nine weighted factors identified the most applicable technologies for small-community lagoons and highlighted barriers to advanced implementation. Life cycle assessment quantified environmental and economic trade-offs across nine scenarios, from baseline facultative lagoons to upgrades with biodomes, iron-dosed upflow anaerobic reactors, aerated gravel-bed reactors, wetlands, and algal systems. Baseline lagoons were most cost-effective ($0.20–$0.30/m³) but had the highest impacts (3 kg CO₂ eq/m³; 0.015 kg P/m³). Upgrades such as aerated gravel-bed and iron-dosed systems reduced eutrophication by 70% with moderate carbon footprint (0.8–1.0 kg CO₂ eq/m³) and higher costs ($0.86–$1.19/m³). An Excel-based multi-criteria decision-support tool was developed to integrate environmental, economic, technical, and social factors through analytical hierarchy process weighting, sensitivity, and uncertainty analyses. Addressing nutrient management in small community lagoons is essential for protecting Gulf ecosystems. Many rural communities that rely on lagoon systems discharge nutrients into tributaries flowing into the Gulf, yet their cumulative impacts remain underrecognized in regional nutrient budgets. By enhancing nutrient removal and recovery at the source, this research provides actionable pathways to reduce nutrient loading from small coastal communities, improve water quality, and strengthen the ecological resilience and long-term sustainability of the Gulf ecosystem.