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Desorption of nitrogen from drinking water treatment residue: Implications for environmental recycling

Wang, Changhui, Liu, Xin, Wang, Mengjiao, Shen, Xiaoxiao, Bai, Leilei, Yuan, Ande, Xu, Huacheng, Jiang, Helong
Journal of cleaner production 2019 v.226 pp. 96-105
adsorption, ammonium nitrogen, desorption, drinking water treatment, electrochemistry, eutrophication, nitrate nitrogen, nitrogen, nutrients, pollution, recycling, remediation, soil washing, surface water, washing, Australia, China, Ireland
This study proposed a scheme for drinking water treatment residue (DWTR) pretreatment to eliminate concerns about potential unfavorable effects caused by excessive release of nutrients (typically N) during recycling in restoration of a water environment with relatively low pollution (e.g., eutrophic surface water). Inspired by soil washing, the pretreatment scheme was based on washing processes; correspondingly, the N desorption characteristics, possibility of recycling solutions for subsequent desorption, and variations in DWTR adsorption capabilities were investigated. The results showed that N, mainly as ammonia N (NH4+-N), was quickly desorbed from DWTR; the concentrations of desorbed NH4+-N were an order of magnitude higher than those of nitrate N (NO3−-N). After six rounds of desorption, most ion-exchangeable NH4+-N was desorbed, and NH4+-N released from the DWTR (after the desorption test) declined markedly from 11.1 to <0.70 mg L−1 in initial column tests for surface water treatment. The same desorption characteristics of NH4+-N were observed for six DWTR collected from Australia, Ireland, and China, respectively; after N desorption, the adsorption capability of the six DWTR changed negligibly. Furthermore, electrochemical treatment was found to be effective in removing desorbed NH4+-N in solutions from DWTR; the treated solutions can be recycled for subsequent desorption without weakening NH4+-N desorption efficiencies, although NH4+-N removal efficiencies by electrochemical treatment tended to decline as the recycling of solutions increased to five rounds. Overall, the pretreatment scheme is scientifically feasible and can be applied and optimized based on remediation requirements in practical scenarios.