Environmental tradeoffs in coking wastewater treatment plant upgrade: a life cycle perspective

• Anaerobic digestion with biogas utilization is the optimal technology for domestic coking wastewater treatment in this study. • Effective leaching toxicity control in incineration residues justifies sludge incineration for coking wastewater management. • Non-GHG emissions significantly contribute to WWTPs’ environmental impact. • Midpoint normalization with uncertainty analysis provides stable probabilistic results across LCIA methods. In the iron and steel industry, treating coking wastewater necessitates a combination of pretreatment, biological treatment, and advanced treatment processes to meet stringent standards for high-quality effluent discharge or reuse. However, the massive consumption of resources during the processing contradicts the current goals of industrial enterprises to pursue energy conservation, emission reduction, and sustainable development. This study employs a life cycle assessment (LCA) methodology to evaluate and compare various treatment alternatives, ultimately ranking them according to the principles of sustainable wastewater treatment development. The aim is to reconcile the above-mentioned contradictions as much as possible. Contribution analysis reveals that, alongside well-recognized factors like energy consumption, chemical usage, and sludge disposal, non-greenhouse gas treatment and emissions significantly influence wastewater treatment plant (WWTP) environmental impacts - contributing 10-20% to Acidification Potential (AP), Eutrophication Potential (EP), and Global Warming Potential (GWP). The normalized results based on midpoint indicators combined with uncertainty analysis indicate that, due to higher consumption of non-renewable energy, the environmental performance of the advanced treatment and reuse scheme for coking wastewater has only a 44.2% probability of outperforming the standard discharge scheme. However, integrating sludge anaerobic digestion improves environmental performance, with a 65.6% probability of superiority. In contrast, sludge incineration offers negligible benefits, as toxicity-related uncertainties in its LCA offset potential gains. Notably, the aforementioned normalization method ensures consistent results across different LCIA methods.