Wang Zhiwei, Zheng Junjian, Tang Jixu, Wang Xinhua, Wu Zhichao
State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai, 200092, P.R. China.
School of Environmental and Civil Engineering, Jiangnan University, Wuxi 214122, P.R. China.
Sci Rep. 2016 Feb 22;6:21653. doi: 10.1038/srep21653.
Recovery of nutrients and energy from municipal wastewater has attracted much attention in recent years; however, its efficiency is significantly limited by the low-strength properties of municipal wastewater. Herein, we report a pilot-scale forward osmosis (FO) system using a spiral-wound membrane module to concentrate real municipal wastewater. Under active layer facing feed solution mode, the critical concentration factor (CCF) of this FO system was determined to be 8 with 0.5 M NaCl as draw solution. During long-term operation at a concentration factor of 5, (99.8 ± 0.6)% of chemical oxygen demand and (99.7 ± 0.5)% of total phosphorus rejection rates could be achieved at a flux of 6 L/(m(2) h) on average. In comparison, only (48.1 ± 10.5)% and (67.8 ± 7.3)% rejection of ammonium and total nitrogen were observed. Cake enhanced concentration polarization is a major contributor to the decrease of water fluxes. The fouling also led to the occurrence of a cake reduced concentration polarization effect, improving ammonium rejection rate with the increase of operation time in each cycle. This work demonstrates the applicability of using FO process for wastewater concentrating and also limitations in ammonium recovery that need further improvement in future.
近年来，从城市废水中回收营养物质和能量备受关注；然而，城市废水的低强度特性严重限制了其回收效率。在此，我们报道了一种使用螺旋卷式膜组件浓缩实际城市废水的中试规模的正向渗透（FO）系统。在活性层面对进料溶液模式下，以0.5 M NaCl作为汲取溶液时，该FO系统的临界浓缩因子（CCF）被确定为8。在浓缩因子为5的长期运行过程中，平均通量为6 L/(m²·h)时，化学需氧量的截留率可达(99.8 ± 0.6)%，总磷的截留率可达(99.7 ± 0.5)%。相比之下，铵和总氮的截留率仅分别为(48.1 ± 10.5)%和(67.8 ± 7.3)%。滤饼增强的浓差极化是水通量下降的主要原因。污垢还导致了滤饼减少浓差极化效应的出现，随着每个循环运行时间的增加，铵截留率提高。这项工作证明了使用FO工艺进行废水浓缩的适用性，同时也表明了铵回收方面存在的局限性，未来需要进一步改进。
