Minimization of Fouling for Treatment of Municipal Wastewater with Membrane Filtration

In this thesis project, treatment of municipal wastewater using ultrafiltration is evaluated to investigate ways to prevent or minimize fouling from occurring. The aim of this project is to examine which factors play a significant role in causing different types of fouling, in order to minimize the resulting effect and thereby increase the efficiency and lifetime of the membrane. The project started with a broad literature study, which researched which methods are currently used to treat wastewater on an industrial level and other state-of-the-art solutions that are available. This was then used to form an experimental plan where two membranes were tested using a pilot plant constructed at IVL’s research facility Hammarby Sjöstadsverk. Firstly, a polymeric membrane was tested using different pressures to see the influence on the membrane flux. The results indicated that although a higher pressure lead to higher flux, there is an upper limit for the flux that was achieved at 5 bar, since similar flux values were found at 5 bar, 7 bar and 9 bar. Also, though a higher flux did lead to a more rapid decrease in flux initially, all curves plateaued after approximately 40 minutes. An average recovery of the membrane flux capacity was 88.7%, where the highest one was achieved with a pressure of 7 bar. Secondly, a ceramic membrane was tested using a factorial design with three parameters, each having a low and high setting. The parameters that were tested were the total operating time, the pressure and the cleaning time of the membrane, with the aim to investigate how each parameter influenced the fouling and the removal of organic compounds from the wastewater. The fouling was analyzed by measuring the flux across the membrane and showed mixed results. Fouling could be removed and the flux often had a recovery of 100% or more, however, no clear conclusion could be drawn to which parameter was the most influential for this high removal percentage. As for the removal of organic compounds, an average removal of 66.9% was achieved and it was determined that the cleaning time was the most influential parameter, and the interaction between running time and pressure being the second most influential