The third cleaning process used in water filtration is CIP (Cleaning-in-place). Until the 1950s, closed industrial applications were dismantled completely to conduct manual cleaning demanding many working hours and extended operational downtime. However, we can clean filtration systems without utilizing time to dismantle them with chemical cleaning-in-place. CIP includes the combination of chemicals, heat, and water, which will cause targeted fouling to be dissolved due to the exploited chemicals. Even so, a membrane needs high chemical resistance to withstand periodic chemical cleaning. As ceramic membranes possess high chemical resistance, CIP is a very efficient method to clean ceramic membranes of a liquid filtration application while maintaining high hygiene standards, which is essential in most fluid purification processes.
Often, a water filtration system has two attached CIP tanks, ensuring the targeted fouling can be removed. One tank holds a chemical alkaline, which removes objects such as grease and other organic compounds. The other tank contains a chemical acid used to remove objects such as minerals. Thus, the membranes can be cleaned in a wide range of pH.
During the CIP process, the filtration system shuts down, and the required chemicals are dosed into the system. The substances will then be circulated in the ceramic membranes with a crossflow pump to secure sufficient cleaning of all surfaces. The circulation time can be installed based on specific requirements. The temperature is increased to approximately 40-60 °C to boost the effectiveness of the chemicals. Depending on the water filtration system, the utilized CIP process, and the cleaning requirements, CIP typically takes 60-90 minutes. When the CIP process is done, the system is emptied using a substantial cleaning dissolution, and everything is led back to the water system’s process tank. CIP does not produce any chemical waste which is not filtered.
Once a CIP is performed, the TMP and the permeability are restored.