Ammonia recovery from real biogas slurry in the up-scaled Donnan Dialysis-Osmotic Distillation membrane-based system: Performance and potentials

Abstract

Recovering ammonia from wastewater is crucial for building a circular economy and achieving carbon neutrality. Some innovative ammonia recovery technologies have shown great potential yet lacking theoretical guidance for up-scaling from laboratory to practical applications. Herein, upon our previously-proposed Donnan dialysis-osmotic distillation (DD-OD) hybrid process for selective ammonia recovery at nearly zero energy input, two challenges as process modelling/prediction and product application were solved in this study. Under the guide of the tailor-made mass transfer model, a reasonable design of the reactor and operating parameters was fixed, whose performance in recovering ammonia from real biogas slurry and the feasibility of the recovered product as irrigation water was then investigated. The up-scaled DD-OD reactor achieved efficient and stable ammonia removal and recovery (∼75 % and ∼ 65 %, respectively) and excellent impurity retention efficiency (∼95 %) in 360 h continuous run. Impurities deposited on the cation-exchange membrane did not affect ammonium transfer and were effectively removed by water washing, and no fouling was found for the hydrophobic membrane, highlighting its long-term capability for ammonia recovery. Moreover, the cost-effectiveness of the process was analyzed, which could be greatly improved given the future improved membrane materials. A proper dilution of the recovered product for irrigating cabbage and radish promoted plant growth, and recycled product containing a moderate ammonia concentration (136 mg/L) was highlighted, with a well-rounded, multi-element nutrient profile recommended. The above results provide theoretical guidance for the scaling-up of ammonia recovery module and a potential pathway for the application of recycled products in agricultural irrigation.