Single and Multi-Stage Membrane Separation for Dairy Wastewater Purification

Kertész, Sz. and Bor, P. and Beszédes, S. and Hodúr, C. (2017) Single and Multi-Stage Membrane Separation for Dairy Wastewater Purification. In: 9th Eastern European Young Water Professionals Conference, 2017.05.24-2017.05.27, Budapest.

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Abstract

Before discharging into sewerage or living waters, dairy effluents need to be effectively treated to meet the requirements defined by the strict environmental protection regulations. In addition to the commonly used technologies such as sedimentation or oxidation, membrane separation can offer a novel solution to the problem. Although the advantages of membrane separations are remarkable, membrane fouling still often limits its industrial scale application. Module vibration can reduce membrane fouling by altering the cake layer on the surface of the membrane. In the first part of the experiment our aim was to investigate the effect of the increased membrane surface shear rate on the membrane flux, rejection and specific energy demand. The shear rate was increased by using a laboratory mode Vibratory Shear Enhanced Processing (VSEP). Furthermore, single ultrafiltration (UF) and nanofiltration (NF) with different membrane molecular weight cut offs (MWCO) were tested and the permeates were analyzed and compared. These tests revealed that vibration has a positive effect on flux, specific energy demand and rejections. In the second part of the project multi-stage separation experiments were carried out. During the multi-stage UF/NF tests, when NF of the UF permeates were done, the UF was practically a prefiltration process. By comparing these multi-stage experiments with the single NF ones, the effect of the pre-filtration was investigated. Furthermore, when NF of the UF concentrates were carried out, the aim was to process the concentrates until a much higher volume reduction ratio (VRR). These experiments showed that multi-stage separations can be successfully applied for achieving a higher VRR, thus, resulting in a concentrate with higher chemical oxygen demand (COD) in a smaller volume, which may increase the efficiency of post-treatments such as biogas production. Furthermore, these two-stage processes succeeded in producing a permeate with a lower COD value than single-step filtrations did.

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