Nitrogen recovery from low-strength wastewater by combined membrane capacitive deionization (MCDI) and ion exchange (IE) process

Nitrogen exists in municipal wastewater in the form of ammonia/ammonium which is a recoverable resource. Recovering nitrogen to improve nitrogen-use efficiency should be carefully considered to promote global environmental sustainability. However, ammonia ammonium is always not well recovered but removed as one of the main pathways for nitrogen release into the environment, which is due to ineffective ammonia capture. In this study, a new method of ion-exchange resin ammonium recovery combined with membrane capacitive deionization (MCDI + IE process) pretreatment is proposed. Selective ion removal by MCDI is demonstrated and ammonium ratio to the total prior ion (K+, Ca2+ and me) in outflow of MCDI cell is respectively increased from similar to 1.5% to over 30% and 45% after 3 and 5 MCDI cycles. The MCDI + IE process could deal with 2.48 and 3.89 times of inflow, respectively, compared with the single IE process after 3 and 5 MCDI charge-discharge cycles and recover more than 65% of ammonium in a resin regeneration cycle after 3 MCDI cycles. It ascribes to MCDI desalination eliminating the negative effects of divalent cations, such as Ca2+ and Me2+, on the IE absorb-desorb process. (C) 2017 Elsevier B.V. All rights reserved.