Reconsidering clean-in-place criterion for low pressure membrane filtration systems using a model verified by long-term pilot plant operation data

In low pressure membrane filtration (LPMF) operations, clean-in-place (CIP) is carried out when transmembrane pressure (TMP) reaches a CIP criterion, which can be chosen up to the maximum allowable TMP suggested by membrane manufacturers. This work suggests how to select a good CIP criterion to decrease the CIP frequency and specific energy consumption (SEC) during the lifetime of membrane. A constant flux LPMF model was developed based on Hermia's blocking model and verified by two years' operation data from a pilot plant with real-size membrane modules. The model exactly expects the fouling mechanism in the real LPMF operation, and the TMP reproduced by the model matches real TMP from the pilot plant very well. The long-term simulation results using the LPMF model reveal: high CIP criteria near the maximum allowable TMP is not necessary to increase the CIP interval; the CIP efficiency as good as 95% could be not sufficient to operate LPMF systems for more than 3 years; and a low value (e.g., 50 kPa) of the temperature corrected TMP at 25 °C as variable CIP criteria can decrease SEC and the CIP frequency during the whole operation period.