Application of a pulsed crossflow to improve chemical cleaning efficiency in hollow fibre membranes following skim milk microfiltration

As the efficient cleaning of membrane systems used for milk protein fractionation remains a challenge, more efficient concepts are required to reduce cleaning times and chemicals consumption. This study examined the so far not commonly applied concept of pulsed flow, characterised by a cyclic transition between high/low flow rates and high/low-pressure phases. To determine its effects on protein fouled polymeric microfiltration membranes, pulsed crossflow conditions were varied in frequency and amplitude during a cleaning step with NaOH as a chemical cleaning agent. The cleaning efficiency was characterised by protein removal and flux recovery. It could be shown that both increasing frequency and flow velocity amplitude can increase protein removal and flux recovery, provided extreme transmembrane pressures are avoided. With pulsed flow, the protein removal could be increased by up to 32% and the flux recovery by 11% compared to a conventionally used steady flow cleaning, thus confirming an increased mechanical cleaning effect when applying pulsed flow. Furthermore, the application of pulsed flow poses a more efficient way to enhance mechanical cleaning power than by increasing the flow velocity under steady flow. Hence, it allows a reduction of energy consumption and thus improves sustainability of the cleaning process. The results indicate a mode of action involving a combination of pulsation induced turbulence and fluctuating relaxation and compaction of the deposit, altogether weakening forces stabilising deposited layer material.