Biofouling Cleaning and Sanitization: Cleaning Procedure for Specific Situations The following cleaning procedure is designed specifically for a system that has been fouled with biological matter. Cleaning Procedure There are seven steps in cleaning elements with biofouling. 1. Make up the cleaning solution listed from Table 6.8. 2. Introduction of the cleaning solution. 3. Recycle. 4. Soak. 5. High-flow pumping. 6. Flush out. 7. Restart.
Cleaning chemical formula in order used: NaOH is sodium hydroxide; Na-DDS is sodium salt of dodecylsulfate (sodium lauryl sulfate); Na4EDTA is the tetrasodium salt of ethylene diamine tetraacetic acid and is available from The Dow Chemical Company under the trademark MS™ 100 and MS 220 crystals. Additional Information By experience, the cleaning solution of Na4EDTA with caustic has been found to be slightly less effective than a standard caustic solution or a solution of caustic and Na-DDS. For any solution, contact time is critical. Several overnight soaks may be necessary to restore the system performance. After the elements are clean it is very beneficial to clean one additional time to clean off the last remaining biofilm layer on the surface of the membrane. Any remaining biofilm will tend to attract and trap dirt, so an extra cleaning will increase the time between cleanings. In the event of severe biofouling, slug dosing of a biocide may be required to enhance the results of the cleaning procedure.