Effect of a hydrodynamic cleaning of a cross-flow membrane system with a novel automated approach

The effect of different hydraulic cleaning methods was investigated in terms of flux decline and resistance using the cross-flow UF unit. The use of varied production intervals, varied ratios of periodic relaxation and the use of a periodic high-rate crossflow were investigated. This cleaning method of relaxation followed by high-rate crossflow mainly removed the resistances of the concentration polarization and gel layer compared with weak adsorption resistance. The cleaning protocol utilizing a periodic relaxation step and/or a periodic increased cross-flow rate at a decreased pressure can lead to productivity improvements and an increase in the operational lifetime of the membrane. If the optimal frequency and duration of the cleaning step (1 h production–60 s relaxation–60 s crossflow) is used, a net productivity increase of 14.8% is achievable and a significant extension to the membrane’s life results. However, a critical point of different cleaning intervals did exist. Utilizing the optimized periodic cleaning techniques developed in this study allows higher recovery rates for ultrafiltration to be achieved, without the problems of increased flux decline normally experienced when operating with high recovery rates.

In this study, the effect of different hydraulic cleaning methods was investigated with the cross-flow UF unit. The cleaning methods in the SCADA system consisted of relaxation, highrate crossflow and relaxation and high-rate crossflow. The optimum cleaning conditions were associated with different pretreatment (flocculation and adsorption). The results led to the following conclusions: (1) Membrane fouling in a cross-flow UF unit can be minimized by the periodic relaxation and high-rate cross-flow cleaning method. This cleaning method mostly removed the resistances of the concentration polarization and gel layer compared with weak adsorption resistance (Raw). (2) A cleaning protocol utilizing a periodic relaxation step and/or a periodic increased cross-flow rate at a decreased pressure can lead to productivity improvements and an increase in the operational lifetime of the membrane. If the optimal frequency and duration of the cleaning step is used, a net productivity increase of 14.8% is achievable and a significant extension to the membrane’s life results. (3) In this study, the cleaning interval of 1 h production–60 s relaxation–60 s crossflow indicated the best result. However, a critical point of different cleaning intervals did exist.