Abstract
Seawater represents a potential resource to ensure sustainable availability of water for population and irrigation purposes, especially in some areas of the world. Desalination processes allow the production of fresh water, but they generate also brine as waste product. Sustainable brine management should be identified to ensure proper disposal and potentially resource recovery. This experimental study showed that emerging technologies such as Microbial Desalination Cells (MDCs) may provide a valuable contribution to the sustainability of the seawater desalination sector. In this paper, we report results on lab-scale desalination brine treatments applying MDCs, which allow energy savings, resource recovery, environmental impact minimization, and reduction of the organic load in municipal wastewater. Our results showed that MDCs’ treatment allows the removal of approximately 33 g of salts (62% of the total)—including chlorides, bromides, and sulphates—from 20 mL of brine within 96 h. The MDCs, according to the source of energy and the presence of mature biofilm at the anode, spent 7.2 J, 7.9 J, and 9.6 J in the desalination process, with the higher amount of energy required by the abiotic system and the lesser by the MDCs fed with just wastewater. Our approach also showed environmental and energy reductions because of potential metal recovery instead of returning them into marine environment. We quantified the avoided life cycle of human and marine eco-toxicity impacts as well as the reduction of cumulative energy demand of recovered metals. The main benefit in terms of avoided toxicity would arise from the mercury and copper recovery, while potential economic advantages would derive from the recovered cobalt that represents a strategic resource for many products such as battery storage systems.
Highlights
Brine is the hypersaline concentrate produced as the main by-product of a seawater desalination process, which is a viable option for freshwater recovery, removing salts, and meeting the quality requirements for human uses [1,2]
MDC_2s and MDC_3s showed a proper polarization about 24 h after the setup, while no significant polarization behavior was observed in the abiotic control (MDC_cntr)
Less stability and PD were observed in MDC_3, with 0.38 ± 0.21 mW/m2 and 8.83 ± 6.7 mA/m2 maximum values on average. These results showed that the application of the external voltage did not improve the performance of Microbial Desalination Cells (MDCs) in terms of polarization and power outputs (Figure 3a,b)
Summary
Brine is the hypersaline concentrate produced as the main by-product of a seawater desalination process, which is a viable option for freshwater recovery, removing salts, and meeting the quality requirements for human uses [1,2]. Brine production from desalination represents a critical environmental issue because of residual organic chemicals and heavy metals (such as copper, nickel, iron, chromium, zinc), high salinity, and relatively high temperature [3,4,5], which affect water ecosystems, soil, and groundwater [6]. The potential damages to the environment include eutrophication, pH fluctuations, and heavy metals and chemicals discharge in marine environments [4,5,6,7]. Recent estimates showed that for each m3 of freshwater water produced, approximately 1 12 m3 of brine may be discharged [2]. Desalinated water production is estimated to be 95.4 million m3 /day, while associated generation of brine is 141.5 million m3 /day [2]
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