Pal Parimal, Chakrabortty Sankha, Nayak Jayato, Senapati Suman
Environment & Membrane Technology Laboratory, Department of Chemical Engineering, National Institute of Technology Durgapur, Durgapur, 713209, India.
Environ Sci Pollut Res Int. 2017 Jun;24(18):15768-15780. doi: 10.1007/s11356-017-9206-z. Epub 2017 May 20.
Effective treatment of tannery wastewater prior to discharge to the environment as per environmental regulations remains a big challenge despite efforts to bring down the concentrations of the pollutants which are often quite high as measured in terms of chemical oxygen demand (7800 mg/L), total dissolved solids (5400 mg/L), chloride (4260 mg/L), sulphides (250 mg/L) and chromium. A pilot-scale forward osmosis and nanofiltration integrated closed loop system was developed for continuous reclamation of clean water from tannery wastewater at a rate of 52-55 L/m/h at 1.6 bar pressure. The low-cost draw solution was 0.8 M NaCl solution. Continuous recovery for recycling the draw solute was done by nanofiltration of diluted draw solution at an operating pressure of 12 bar and volumetric cross-flow rate of 700 L/h. Fouling study revealed that the specific flat-sheet design of cross-flow forward osmosis module with counter current flow of feed and draw solution prevents the build-up of concentration polarization, thus enabling long-term filtration in continuous mode of operation without significant membrane fouling. This study culminates in the development of a compact, efficient and low-cost industrial wastewater treatment and reclamation technology.
尽管人们努力降低制革废水污染物浓度（以化学需氧量计，污染物浓度通常相当高，达7800毫克/升；总溶解固体为5400毫克/升；氯化物为4260毫克/升；硫化物为250毫克/升，还有铬），但按照环境法规要求，在制革废水排放到环境之前进行有效处理仍是一项巨大挑战。开发了一种中试规模的正向渗透和纳滤集成闭环系统，用于以1.6巴压力、52 - 55升/平方米/小时的速率从制革废水中连续回收清水。低成本的汲取液为0.8摩尔/升的氯化钠溶液。通过在12巴的操作压力和700升/小时的体积错流速率下对稀释后的汲取液进行纳滤，实现了汲取溶质的连续回收以循环利用。污垢研究表明，采用进料和汲取液逆流的错流正向渗透模块的特定平板设计可防止浓差极化的形成，从而能够在连续操作模式下进行长期过滤，且不会出现明显的膜污染。这项研究最终开发出了一种紧凑、高效且低成本的工业废水处理及回收技术。
