Abstract
An aircathode microbial desalination cell (AMDC) was successfully started by inoculating anaerobic sludge into the anode of a microbial desalination cell and then used to study the effects of salinity on performance of AMDC and effect of treatment of coastal saline-alkaline soil-washing water. The results showed that the desalination cycle and rate gradually shorten, but salt removal gradually increased when the salinity was decreased, and the highest salt removal was 98.00 ± 0.12% at a salinity of 5 g/L. COD removal efficiency was increased with the extension of operation cycle and largest removal efficiency difference was not significant, but the average coulomb efficiency had significant differences under the condition of each salinity. This indicates that salinity conditions have significant influence on salt removal and coulomb efficiency under the combined action of osmotic pressure, electric field action, running time and microbial activity, etc. On the contrary, COD removal effect has no significant differences under the condition of inoculation of the same substrate in the anode chamber. The salt removal reached 99.13 ± 2.1% when the AMDC experiment ended under the condition of washing water of coastal saline-alkaline soil was inserted in the desalination chamber. Under the action of osmotic pressure, ion migration, nitrification and denitrification, NH4+-N and NO3−-N in the washing water of the desalination chamber were removed, and this indicates that the microbial desalination cell can be used to treatment the washing water of coastal saline-alkaline soil. The microbial community and function of the anode electrode biofilm and desalination chamber were analyzed through high-throughput sequencing, and the power generation characteristics, organics degradation and migration and transformation pathways of nitrogen of the aircathode microbial desalination cell were further explained.
Highlights
Soil nutrients usually include Cl−, SO4 2−, CO3 2−, HCO3 −, Na+, K+, Ca2+, Mg2+ and other ions, which can promote the growth of plants and soil microorganisms
After successful start-up, high-salinity solution, medium-salinity solution, low-salinity solution and fresh coastal saline-alkaline soil-washing water were successively injected into the middle desalination chamber to carry out a complete desalination cycle
The cell was operated in fed-batch mode at a temperature of 25 ± 1 ◦ C, and the desalination chamber was filled with 30 g/L of NaCl solution
Summary
Soil nutrients usually include Cl− , SO4 2− , CO3 2− , HCO3 − , Na+ , K+ , Ca2+ , Mg2+ and other ions, which can promote the growth of plants and soil microorganisms. There is no study involving simultaneous desalination, pollutants removal from coastal saline-alkaline soil-washing water. Most studies have so far have only investigated this with lab-scale designs, more importantly, for coastal saline-alkaline soil-washing water and its influence on desalination has never been explored. For further study on scale-up device and broadening the practical application of MDC, it is worth investigating its performance and efficiency in saline-alkaline soil-washing water treatment. In the present study, a novel aircathode microbial desalination cell (AMDC) was constructed It was to analyze the influence of different salinity concentration of high salinity at 30 g/L, medium salinity at 15 g/L, and low salinity at 5 g/L. Salt and pollutants degradation practicability of the AMDC was evaluated with coastal saline-alkaline soil-washing water treatment. The long-term operation stability of AMDC was examined in terms of current output, power generation, columbic efficiency (CE), internal resistance and cell polarization to further evaluate its practicability
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