Performance Modeling of Decentralized Wastewater Treatment in Rural Azerbaijan: Environmental Impacts and Sustainable Solutions from Shamakhi-Gobustan Region

Access to safe sanitation remains a persistent global challenge, particularly in rural and semi-urban areas where centralized wastewater infrastructure is lacking. This study assesses the environmental impacts of uncontrolled domestic wastewater discharge and proposes a sustainable decentralized treatment model for the Shamakhi-Gobustan region in Azerbaijan. Field investigations revealed elevated levels of biochemical oxygen demand (BOD), chemical oxygen demand (COD), nitrates, and coliform bacteria in groundwater, exceeding WHO standards. To strengthen analytical rigor, a mass balance-based performance modeling framework was employed to quantify pollutant removal efficiencies across treatment stages. A pilot system – comprising a sedimentation tank, anaerobic baffled reactor, constructed wetlands, and solar-powered pumps—was implemented in Padar village. The system achieved average reductions of 85% in BOD and 70% in COD, with significant improvements in nitrate removal and microbial safety. Model predictions closely aligned with observed results, confirming the reliability and scalability of the approach. The proposed model demonstrates strong potential for replication in similarly water-scarce, infrastructure-limited regions. This work contributes to global efforts toward Sustainable Development Goals (SDGs) 6 (Clean Water and Sanitation) and 11 (Sustainable Cities and Communities). Future research is recommended to assess long-term performance, enhance system design, and explore cost-effective innovations using modeling tools.