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Trace ammonium removal by liquid–liquid membrane contactors as water polishing step of water electrolysis for hydrogen production from a wastewater treatment plant effluent

Licon Bernal, Edxon E, Alcaraz, Aurora, Casas, Sandra, Valderrama, César, Cortina, José L
Journal of chemical technology and biotechnology 2016 v.91 no.12 pp. 2983-2993
algorithms, ammonia, ammonium, bicarbonates, buffering capacity, distillation, electrolysis, hydrogen production, models, pH, wastewater treatment
BACKGROUND: This work evaluates hollow fiber liquid–liquid membrane contactors (HFMC) as a polishing step for the removal of low levels of ammonium from water purified by (or being supplied to) a membrane distillation unit in order to fulfil the conductivity requirements of hydrogen production by water electrolysis. RESULTS: The influence of the operating conditions (flow, pH, ammonium concentration, buffer capacity) were evaluated under a closed‐loop setup in order to achieve a reduction of total ammonia concentration in water, from 15 to 1 mg L⁻¹ to assure the production of water in the membrane distillation with a conductivity lower than 1 µS cm⁻¹. These values were used to validate a numerical algorithm describing the system performance. In order to reach the ammonia concentration requirements and considering the low concentration of bicarbonate (low pH buffer capacity) in the treated water a buffer agent was added to the working solution. CONCLUSIONS: HFMC technology is a suitable solution to remove low levels of ammonium from water to values as low as 1 mg L⁻ ¹NH₃ through appropriate control of pH. The ammonium removal efficiency of the HFMC was improved by raising the pH or the flow rate. Finally, the model proposed provides a good description of the membrane contactor performance with minimal deviations when compared with experimental results. © 2016 Society of Chemical Industry