An improved life cycle impact assessment (LCIA) approach for assessing aquatic eco-toxic impact of brine disposal from seawater desalination plants

Most Life Cycle Assessment (LCA) studies did not quantify the aquatic eco-toxic potential (aquatic ETP) of the brine disposal mainly due to the limitation of current life cycle impact assessment (LCIA) approaches. The purpose of this study is to develop an improved approach for assessing the aquatic ETP of brine disposal from seawater desalination plants. The proposed approach, named group-by-group approach, calculates the average aquatic ETP as the sum of the impacts generated by acknowledged groups of influential chemicals. This approach firstly identifies the influential chemicals. According to the chemical property and the impact pathway to the aquatic ecosystem, the important chemicals are then categorized into groups under three categories. Depending on the characteristics of the defined groups, different strategies are applied to determine the impact of each group. The group-by-group approach takes the merits of two most commonly-used approaches, chemical specific approach and whole effluent approach. The results from the case study indicated that this approach reduces the reliance on the comprehensive chemical composition analysis and temporal ecotoxicology test of the complex desalination brine. It also provides a more comprehensive coverage, not only considering the impact of organic chemicals and metals, but also including the contribution of inorganic chemicals. © 2012 Elsevier B.V. All rights reserved.

Many researchers conducted the LCA on desalination without considering the aquatic eco-toxic impact of brine disposal in their studies mainly due to the limitation of current LCIA approaches. This study provides a good critic review of two approaches that are commonly used in the LCA practice for assessing aquatic eco-toxic impact of brine disposal, namely the chemical specific approach and the whole effluent approach. The chemical specific approach has limited application because it is not practical to carry out comprehensive composition analysis of the complex desalination effluent. The whole effluent approach does not need to characterize the effluent, but it only provides a temporal estimation. Significant uncertainty probably occurs due to the variation of brine composition and intrinsic water quality. This study developed an improved approach, named the group-by-group approach, to quantify the impact of complex and Table 5 Sensitivity analysis results. Chemical specific approach Eco-toxic impact of discharging 1 m3 of brine from RO plant “Baseline” Ave (PAF.m3.day/m3 1.22 scenario effluent) 100% “What if” Reduce Cu by 10% −7% scenarios Reduce Ni by 10% Negligiblea Reduce Cr by 10% −3% Reduce salinity by 10% 0b Reduce all metals by10% −10% Eco-toxic impact of discharging 1 m3 of brine from MSF plant “Baseline” Ave (PAF.m3.day/m3 5.75 scenario effluent) 100% “What if” Reduce Cu by 10% −10% scenarios Reduce Ni by 10% Negligible Reduce CHBr3 by 10% Negligible Reduce salinity by 10% Reduce free chlorine by 10% 0 Reduce halogenated Negligible hydrocarbons by 10% Reduce all metals by 10% −10% a b Group-by-group approach 37.8 100% Negligible Negligible Negligible −10% Negligible 30.4 100% −2% Negligible Negligible −8% −1% Negligible −2% “Negligible” means the “what if” scenario has minor effect on the final result. “0” means the “what if” scenario has no effect on the final result.