Do you understand the pollutants in reverse osmosis equipment?

These pollutants are also commonly found in surface water or wastewater. When treating such water sources, pollution often first manifests in the membrane elements at the front end of the reverse osmosis equipment. When this occurs, the pressure at the front end of the reverse osmosis equipment increases rapidly. Initially, the desalination rate of the reverse osmosis equipment may improve, but as the membrane system continues to operate, biological pollution will gradually spread throughout the reverse osmosis equipment, resulting in widespread membrane fouling. When biological fouling occurs in the membrane system, it ultimately leads to a significant increase in system operating pressure and a decrease in water production. These pollutants are typically bacteria, biofilms, algae, and fungi. Generally, when designing a reverse osmosis process system, it is important to control the activity of the raw water. When the raw water bacterial content exceeds 1000 cfu/100mg, removal measures must be considered in the design.

Suspended Solids

These pollutants are commonly found in surface water and wastewater sources, with particle diameters often greater than 1 micron. When the water is undisturbed, these impurities can settle completely. They are easily filtered out by the fine sand filters and multi-media filters installed in the reverse osmosis equipment. When flocculants or coagulants are used in the reverse osmosis pretreatment system, these impurities can also be adsorbed by the flocs formed by the flocculants and then filtered out by the multi-media filters or sand filters.

Organic Pollutants

The composition of organic matter in raw water is extremely complex, and its pollution and impact on reverse osmosis membrane elements are difficult to predict. However, this indicator is a major pollutant that needs to be carefully considered for protection when designing reverse osmosis equipment. Organic pollutants generally come from two sources: one is natural humic organic matter formed by the decay of plants and animals, and the other is organic matter formed by industrial waste pollution. When organic matter pollutes the reverse osmosis membrane, it is often firmly adsorbed onto the membrane surface, making it difficult to clean. Generally speaking, the consequences of organic matter pollution on membrane systems are the most difficult to predict: some organic matter in water has almost no damaging effect on reverse osmosis membranes, but some trace organic matter, once adsorbed onto the membrane surface, can not only pollute the reverse osmosis membrane but also cause membrane degradation and deterioration. Therefore, we must pay close attention to the organic matter present in the raw water. Therefore, in principle, when designing a reverse osmosis device, if the raw water TOC content reaches 3 mg/l, corresponding removal measures must be considered in the system. Generally speaking, in the reverse osmosis pretreatment system for treating surface water and wastewater, most organic pollutants should be removed or decomposed and converted during the pretreatment processes of flocculation, clarification, and oxidation. If the above treatment still cannot meet the influent requirements, the use of activated carbon adsorption filters, organic matter scavengers, or ultrafiltration equipment can be considered to further remove them to ultimately meet the influent requirements of the reverse osmosis equipment.

Colloidal Pollutants

These pollutants are also commonly found in surface water and wastewater sources, with particle diameters often less than 1 micron. These impurities do not settle freely even when the water is undisturbed and remain suspended. These impurities may be monomeric compounds of organic or inorganic composition, or composite compounds composed of multiple compounds, such as silica compounds, iron and aluminum oxides, sulfides, tannic acid, and humic substances.