强化混凝-平板折转错流超滤工艺处理脱墨废水

采用强化混凝-平板折转错流膜分离技术对脱墨废水的二级生化出水进行了深度处理中试研究，从运行方式、超滤膜种类、清洗方式、长期运行稳定性等方面评估了工艺适用性。结果表明，间歇运行方式可有效降低滤饼层阻力(R_c)和浓差极化阻力(R_g)，缓解膜污染，提高水通量和出水水质。亲水性强、截留分子质量(30 kDa)较大的聚偏氟乙烯(PVDF)超滤膜可以延缓膜污染，提高产水率和出水水质；比截留分子质量(8 kDa)较小的PES膜更适宜脱墨废水二级生化出水的处理。正反同步冲洗可有效清洗膜表面及膜孔内部，显著降低滤饼层阻力(R_c)、孔堵阻力(R_f)、浓差极化阻力(R_g)，且可避免反冲洗损伤膜表面功能层。在跨膜压差为0.025 MPa、聚合氯化铝投加量为2 g·L⁻¹条件下，采用停歇2 min、运行8 min操作方式，PVDF超滤膜可在膜通量为80 L·(m²·h)⁻¹以上连续运行50 h，COD、浊度、色度的平均去除率分别可达79.1%、99.9%和99.4%，满足我国《工业用水水质标准》(GB/T 19923-2005)中循环冷却水系统补水要求，且清洗后水通量可恢复95%以上，表明该技术具有深度处理脱墨废水的应用潜力。

Deinking wastewater treatment by a hybrid process of enhanced coagulation and flat-plate ultrafiltration in turn-around cross-flow mode

A pilot study on advanced treatment of the deinking wastewater from the secondary sedimentation tank in a paper mill was conducted using a hybrid process of enhanced coagulation at a high dosage of polyaluminum chloride (PACl) and flat-plate ultrafiltration in turn-around cross-flow mode. The applicability of the process was evaluated from some aspects including the operation mode, the membrane type, the cleaning mode, and the stability of long-term operation. The experimental results showed that an intermittent operation could effectively reduce the cake layer resistance (Rc) and the concentration polarization resistance (Rg), alleviate membrane fouling, and improve water flux and effluent quality. The PVDF membrane with hydrophilicity and higher molecular weight cut-off (30 kD) could alleviate membrane fouling and improve water yield and effluent quality, and consequently be more suitable for treating the deinking wastewater than the PES membrane with a MWCO of 8 kD. The simultaneous flushing along membrane surface and backwashing could effectively remove the foulants on membrane surface or in membrane pore, and significantly reduced Rc, Rg, and the pore blocking resistance (Rf). Furthermore, backwashing could avoid the damage to the active layer of membrane. The PVDF membrane could continuously run for 50 h at the PACl dosage of 2 g·L−1, with a flux of 80 L·m−2·h−1 or more under the TMP of 0.025 MPa. The average removal rates of COD, turbidity, and chroma could reach 79.1%, 99.9% and 99.4%, respectively, which can meet the requirements of The reuse of urban recycling water – Water quality standard for industrial use (GB/T 19923-2005). Moreover, the flux recovery rate could reach over 95% after cleaning. All these indicate the hybrid process is feasible for advanced treatment of the deinking wastewater.