Life cycle assessment, a decision-making tool in wastewater treatment systems: a case study wastewater treatment plant of Ahvaz, Iran

The evaluation of environmental implications associated with wastewater treatment plants and developing strategies for reusing wastewater with minimal harm to the environment and human communities is critical. This study investigates the environmental impacts of Ahvaz’s wastewater treatment plant using life cycle assessment, employing SimaPro®9.0.0 software for two scenarios. The first scenario represents the current state of the plant, while the second considers reusing treated effluent in farms. This examination can lead to modifications within existing systems or selection of the best alternative treatment option, ultimately reducing potential environmental impacts. The CML2001 method identified human toxicity and global warming (4.29 × 1013 and 3.67 × 1013, respectively), while the EcoIndicator99 method indicated ecotoxicity and carcinogens (5.2 × 10−13 and 2.82 × 10−13, respectively) as the highest contributors to negative environmental impact per 1 m3 treated effluent. The results demonstrate that although using treated sludge and effluent in agriculture conserves a significant amount of water, phosphorus, and nitrogen, it caused significant adverse impacts due to heavy metals present in the effluent and sludge. Additionally, the methane produced by sludge treatment, digestion, and disposal processes had the most harmful impact on global warming (0.577 (65%) in the CML2001 method). Comparing the two scenarios demonstrates that reusing effluent in farm irrigation is a more environmentally friendly technique, particularly in terms of eutrophication.