Using Water Testing to Monitor Reverse Osmosis Plant Efficiency and Lifespan

Water testing is important to Reverse Osmosis (RO) as it helps identify and/or diagnose health of existing RO systems in place to ensure the effectiveness of RO systems.

Among the various tests that can be conducted, chlorine testing, silt density index (SDI) testing and conductivity/pH testing are the most critical.

Chlorine/Hardness Testing

While chlorine can act as a disinfectant in water treatment processes, with excessive levels of chlorine, RO membranes can be easily damaged. This is especially the case for polyamide membranes. 

Chlorine testing in RO systems involves measuring the concentration of chlorine present in the feed water. This is typically done using colorimetric methods or electronic chlorine sensors.

Water hardness refers to the concentration of dissolved minerals, primarily calcium and magnesium ions. High hardness levels result in scale buildup on RO membranes, reducing their efficiency and lifespan. 

SSS can offer curated chlorine/hardness test kits for quick analysis of free & residual chlorine and hardness levels.

Conductivity/pH Testing:

Conductivity and pH are critical parameters that directly influence RO membrane performance. High conductivity levels signify the abundance of dissolved ions in water. The higher the concentration of dissolved ions, the more scaling and fouling occurs on RO membrane. For reference seawater has a typical conductivity of around 50,000 uS/cm while tap water is usually below 800 uS/cm.

pH measures the acidity or alkalinity of the water. At extreme levels, pH can affect membrane integrity and other down stream processes following RO.

SSS can offer curated conductivity/pH test kits for quick analysis of conductivity and pH levels.

SDI Testing

Silt Density Index, or SDI, measures the suspended solids content in water. High SDI values indicate the presence of particulate and colloidal matter that can clog RO membranes and reduce system efficiency. 

Feed water to RO must have an SDI of between 3 and 5 or lower. SDI testing involves passing water sample through a 0.45 µm filter membrane and measuring the pressure drop across the filter. Higher pressure drops correspond to higher SDI values.

Monitoring SDI levels helps assess pretreatment effectiveness and the need for additional filtration or maintenance.

SSS can offer curated SDI testing kit for quick convenient testing of SDI levels.