Wroclaw University of Science and Technology, Faculty of Environmental Engineering, Department of Environment Protection Engineering, Wroclaw, Poland
Due to the increasing water scarcity in agriculture, digestate is not only considered as an alternative fertilizer, but also as a potential water source. Unfortunately, it requires treatment to such an extent that the contaminants from the fermented biomass do not return to the environment. The aim of this study was to extend the characteristics of the flat ceramic membranes provided by manufacturers and to evaluate their applicability to the treatment of the municipal digestate liquid fraction. The digestate liquid fraction from a biogas plant processing municipal waste organic fraction located in the Lower Silesia province (Poland) was tested. A Sterlitech laboratory plant operating in the dead-end mode at a TMP of 0.1 - 0.4 MPa was used to carry out the pressure membrane filtration process. The tested digestate was subjected to 72 h of sedimentation before testing. Six micro- and ultrafiltration flat ceramic membranes from Tami Industries were used in the experiments. The membranes used in this study were hydrophilic (a wetting angle of less than 59.6°) and the average pore radius ranged from 0.035 to 0.29 µm, depending on the membrane type. The performed experiments confirmed the applicability of the tested membranes for municipal digestate purification, although a deterioration in permeate quality was observed as the pore size of the membranes increased. The best separation was observed for the 1 kDa membrane, the average pore diameter of which was 35.53 nm.