For the past few years, reverse osmosis (RO) systems had been the standard for effective water purification from any water sources, and had even been beneficial for wastewater and reuse applications essential for industrial processes. Among the system’s most essential parts is its membrane element, which could last for between three and seven years, depending on its use and maintenance.
Like most systems, reverse osmosis systems also require regular maintenance and cleaning to ensure that these would remain at their top shape. Even quality RO membrane components require cleaning to keep producing potable drinking water for everyone, which would be impossible if these systems are teeming with accumulations of foreign material.
Fouling and Pretreatment
Numerous RO systems require pre-treatment to ensure that their membrane elements wouldn’t be subject to fouling and chemical degradation. Usually, the type of pre-treatment needed will depend on the composition of the water source. For example, surface water usually has a high concentration of colloids that have high turbidity or high silt density index levels. Ideally, RO elements could function well with turbidity levels reaching less than 1 nephelometric turbidity units or less than 5 SCI units, something that could be achieved with the help of multimedia filtration, microfiltration, and ultrafiltration.
Determining the components of the water source is often an indication of what type of fouling that could be expected in the system’s membrane elements. Again, with surface water, contamination like colloidal fouling, biofouling, and organic fouling can be expected in the membrane elements, while well water could typically cause iron oxide or iron hydroxide fouling.
When to Clean?
Once these RO membranes get contaminated by microorganisms, suspended solids, and mineral scale, these deposits can cause loss in water input or salt rejection, and at times even both. Thus, it’s recommended to clean membrane elements once the normalized water output rate drops by as much as 15 percent. However, successful cleaning of RO membrane components will depend if a correctly designed cleaning skid is used, and the membrane elements can withstand acid cleaning at around pH levels of 1 and alkaline cleaning of pH 12 at minimum.
Cleaning membrane elements can be summarized in these processes, which should be strictly followed for successful cleaning. Acid cleaning should first be done, followed by alkaline cleaning and sanitizing, with thorough flushing done in between these steps. A quality reverse osmosis membrane, like those from AXEON Water Technologies, can help provide safe drinking water for everyone, and these would work even better once their elements have been cleaned and maintained properly.
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