How to Choose an Industrial RO Plant: TDS, Recovery, Membranes and Sizing

Divide your daily treated water requirement by the hours the plant will run, then add a margin. For example, 40,000 litres a day over 20 hours needs 2,000 LPH, so a 2,500 LPH plant allows for growth and cleaning downtime. Remember feed and reject flows are higher than permeate, so your raw water source and drainage must cope too.

For brackish water, recovery is typically somewhere between 50% and 75%, set by feed hardness, silica and other scaling ions rather than by preference. Higher recovery saves water but increases scaling risk and cleaning frequency. A membrane projection using your actual water analysis is the right way to set it, and antiscalant dosing helps reach the upper end safely.

The most common causes are scaling from inadequate antiscalant dosing or excessive recovery, fouling from poor pre-treatment, chlorine damage when carbon filters or SMBS dosing are neglected, and iron or organic fouling. Irregular cleaning and running the plant outside design pressure also shorten life. Good pre-treatment, logged readings and timely CIP typically keep membranes working for several years.

Often, partly. Depending on its TDS, reject can be used for floor washing, toilet flushing, dust suppression or blended for gardening where soil and plants tolerate it. In industries with zero liquid discharge conditions, reject goes to a second RO stage and then evaporators or crystallisers. The best option depends on volume, quality and your consent conditions.

Antiscalant is a chemical dosed in small quantities before the RO to stop dissolved salts such as calcium carbonate, calcium sulphate and silica from crystallising on the membranes as they concentrate. For almost all borewell and brackish sources it is necessary. The product and dose should be selected using the water analysis and projection software, then checked periodically.

Smaller plants, roughly up to a few thousand LPH, often use 4-inch elements because they suit lower flows and are easy to handle. Larger industrial plants typically use 8-inch elements, which offer more membrane area per vessel and lower cost per litre. The choice is made during design based on flow, number of stages and flux limits.

Yes. BJC Global offers AMC for RO plants it builds and, after inspection, for many existing plants. AMC typically includes scheduled visits, performance checks, membrane cleaning, cartridge replacement, dosing pump servicing and guidance on chemicals and spares. We can also train your operator to log daily readings so problems are caught early.