Designing turbulence promoters with optimal geometry and using them for ultrafiltration systems has been a key challenge in mitigating membrane fouling. In this study, six different turbulence promoters were created using three-dimensional printing technology and applied in dead-end ultrafiltration. Three-dimensional-printed (3DP) turbulence promoter configurations were integrated into a classical batch ultrafiltration cell. The effects of these configurations and the stirring speeds on the permeate filtration flux, organic rejections, and membrane resistances were investigated. The fouling control efficiency of the 3DP promoters was evaluated using two polyethersulfone membranes in a stirred ultrafiltration cell with model dairy wastewater. The Hermia and resistance-in-series models were studied to further investigate the membrane fouling mechanism. Of the Hermia models, the cake layer model best described the fouling in this membrane filtration system. It can be concluded that the 3DP turbulence promoters, combined with intense mechanical stirring, show great promise in terms of permeate flux enhancement and membrane fouling mitigation. Using a well-designed 3DP turbulence promoter improves the hydrodynamic flow conditions on the surface of the stirred membrane separation cells based on computational fluid dynamics modeling. Therefore, the factors effecting the fabrication of 3DP turbulence promoters are important, and further research should be devoted to revealing them.

In this work the effects of oxidation pre-treatments (ozonation and Fenton reaction) on membrane filtration of dairy wastewater were investigated, together with the further utilization possibilities of residual wastes. The oxidation pre-treatments enhanced the membrane filtration efficiency, from which the short-term ozone treatment was found to be the most effective method both in terms of increasing the flux and the pollutant removal efficiency. After ozone pre-treatment the phosphate and ammonium content of the wastewater migrated to the permeate, while after Fenton pre-treatment the phosphate content remained in the concentrate, and the ammonium content in the permeate decreased. The concentrate was utilized as biogas resource and it was found that both pretreatments increased the biogas production and its methane content as well. Based on our results it can be concluded that ozone pretreatment combined with membrane separation have improved the efficiency of dairy wastewater treatment and may suit the requirements of circular economy.

This study aimed to investigate the effect of ozone and Fenton-reaction as a pre-treatment before ultrafiltration of model dairy waste waters containing sodium caseinate. Filtration resistances and pollutant retentions were determined and compared. It was found, that both pre-treatment increased the retention, achieving almost 100 % pollutant elimination efficiency after short term pre-oxidation. The effect of Fe-ion concentration on Fenton pretreatment efficiency also was examined, and it was found that higher concentration resulted in decreased filtration resistances, revealing that coagulation-flocculation effect of reactants has dominant role in the protein separation efficiency. The presence of lactose also affects the pollutant removal efficiency, it promotes fouling in presence of Fenton reagents.