What are the symptoms of RO contamination? After contamination occurs in a reverse osmosis system, the general symptoms are as follows: an increase in the pressure drop between the system feed water and the concentrate, changes in the feed pressure of the reverse osmosis system, variations in the normalized product water flow rate, and changes in the normalized salt passage rate. How to reduce failures and decrease the frequency of reverse osmosis cleaning? To reduce failures and lower the frequency of reverse osmosis cleaning, the following measures should be taken: design the reverse osmosis system based on a complete analysis of water quality, determine the SDI value of the RO feed water before proceeding with the design, make corresponding design adjustments if the feed water quality changes, ensure adequate pretreatment, select the correct membrane elements, choose a relatively conservative water flux, adopt a reasonable water recovery rate, design sufficient cross-flow velocity and concentrate flow rate, and normalize the operational data. When is chemical cleaning needed? The removal of contaminants can be achieved through chemical cleaning and physical flushing, and sometimes by altering operating conditions, as a general principle. Cleaning should be performed under the following circumstances: when the product water flow rate drops to 85%–90% of the normal value under normal pressure; when the temperature-corrected feed water pressure increases by 10%–15% to maintain normal product water flow; when the product water quality decreases by 10%–15%, and the salt passage rate increases by 10%–15%; when the operating pressure increases by 10%–15%; and when the pressure difference between various stages of the RO system increases significantly.