Environmental and economic assessment of gasification wastewater treatment by life cycle assessment and life cycle costing approach

This study compared the sustainability of six alternatives for the treatment of industrial wastewater from a gasifier, considering both environmental and economic aspects by the approaches of: uses Life Cycle Assessment (LCA) and Life Cycle Cost (LCC). The processes have been developed under the zero liquid discharge approach and included a chemical removal of pollutants by using Fenton and neutralization, evaporation and crystallization to concentrate salts and stripping for the removal of ammonia from distillate of evaporation step and recover water useful for industrial reuses. The scenarios differed for the type of utilities used for the operation (steam and hot water from thermal waste) and from an optimization of the crystallization that provided a reduction of the amount of waste and an energy recovery from distillate. LCA indicated that the six scenarios produced comparable results, since the common chemical treatment (raw material and waste disposal) causes the highest contribution. The optimal scheme used hot water as utilities and had an optimization of the crystallization section (scenario B2), this options allowed a decrease of emission to air of 25% and reduction of 15% of deposited goods. Scenario B2 is much more financially attractive than the other proposed treatment, having a total cost of 123 €/t, with a reduction of 17% respect to the current disposal of 150 €/t. LCA and LCC results prove the effectiveness of thermal waste use as utilities for the wastewater treatment operations and the optimization of crystallization unit is the most environmentally and economically favourable alternative.