Reverse Osmosis Systems – Performance Considerations and Pretreatment Solutions

The backbone of the water treatment industry, Reverse Osmosis (RO) removes contaminants, salts, and other impurities from unfiltered or feed water through a pressure force of the semipermeable membrane. This membrane blocks contaminants and lets the water molecules to pass. In osmosis, the water coming from the semipermeable membrane becomes more concentrated. In Reverse osmosis, the membrane blocks contaminants and other impurities from entering the less concentrated side. The clean drinking water or the freshwater produced after reverse osmosis is called the permeate and the leftover concentrate is waste or the brine.

For industrial and commercial use, benefits of reverse osmosis can be understood in water treatment for power generation which results in low operating and maintenance costs. Also, RO systems remove large concentration, i.e. up to 99% of impurities and dissolved salts from water from almost all sources. Becoming a zero-liquid discharge (ZLD) facility has added advantages for political and regulatory compliance.

For design considerations and also to judge the performance of an RO system, there is the instrumentation that displays characteristics including but not limited to the quality, flow, pressure, temperature, or the number of hours of operation. The following parameters could be inspected: Feed pressure, Permeate conductivity, temperature, concentration pressure and so on.

Pretreatment is critical to prevent fouling, scaling, and premature RO failure. Some common RO system problems due to lack of pretreatment include

Fouling – When contaminants accumulate on the surface of the membrane. Can be caused by organics, microorganisms, particulates, and so on.

Scaling – Inorganic or dissolved concentrated compounds which when exceed their solubility limits, surfaces on the membrane.

Chemical Attack – Thin film of oxidisers, chlorine or chloramines which can cause irreparable damage.

Mechanical damage – Plumbing and controls need to be checked which otherwise are capable of causing mechanical damage to the membranes.

Below are a few solutions for the pretreatment which can help minimize the issues effectively.

Multi-Media Filtration (MMF) – is used to prevent fouling of the system and is suggested when the Silt Density Index (SDI) is more than 3.

Microfiltration (MF) – Aids in getting rid of colloidal and bacteria matter which also facilitates in reducing the fouling potential.

Scale Inhibitors – To help reduce scaling potential by adding chemicals to feed water before an RO unit. Essentially, increasing solubility limits of inorganic compounds.

Water Softening – Using ION exchange, a water softener can aid in preventing scaling in the system.

Granular Activated Carbon (GAC) – removing residual chlorine, chloramines (disinfectants), and organic constituents.

Inevitably, RO membranes, systems require periodic cleaning which depends on the feed water. The cleaning could be 1 to 4 times a year. PDFL, the best-in-class service company can service your reverse osmosis systems and membranes, giving it a new-like performance capacity, i.e. make the cleaning effective to provide high-purity water. RO membrane cleaning involves treating biofouling, colloidal with high pH cleaners, and Scaling with lower pH cleaners.  It is not just about removing contaminants but involves cleaning taking into consideration appropriate chemicals.

The lifespan of the Reverse Osmosis system is anywhere between 10-15 years while the RO membrane and filters need to be replaced periodically for proper functioning. The RO membrane is usually changed every 2-4 years and the filters, every 6-12 months.

At, PDFL, our superior products and trust of our clients for decades have strengthened our bond. Our Reverse Osmosis Systems achieve the required results because the treatment components are designed, operated, and maintained by experts.

At PDFL, we manufacture full-fledged Reverse Osmosis Systems designed for multiple water applications for heavy and/or consistent use for various industries. We also offer service and maintenance for the smooth running of your RO systems. We prioritise quality, reliability, and performance and combine it with your specifications.

Our engineers and RO specialists work closely with you while ensuring all standards are followed and safety and health are taken care of.