Key Questions
What is a membrane water treatment system?
A membrane system forces water through semipermeable membranes that reject salts, bacteria and particles. Navbharat Water combines RO, UF, NF and MF membranes in systems from 1 KLD to 5 MLD, and reverse osmosis alone rejects more than 98% of dissolved TDS.
Each membrane type works at a different scale. Reverse osmosis operates at high pressure, 15–80 bar, rejecting dissolved salts, organics and 99% or more of bacteria, with recovery of 65–85%. It is used for desalination, DM water production and ZLD brine concentration. Ultrafiltration runs at low pressure, 1–4 bar, with pore sizes of 0.01–0.1 micron, removing bacteria, viruses and colloids at 90–95% recovery; it protects RO membranes as pre-treatment and forms the core of MBR sewage plants. Nanofiltration softens water and removes divalent ions and colour, while microfiltration pre-filters turbid feeds, both suited to food and beverage, textile and pharmaceutical duties where full desalination is not required. RO membranes are polyamide thin-film composite, and UF and MF membranes are PVDF, with automated clean-in-place tolerating pH 2–12. Membranes are deployed selectively, often in combination, to hit the exact quality the process needs.
How pure can RO and EDI make water for pharmaceutical use?
Double-pass RO followed by Electrodeionisation (EDI) brings conductivity below 0.1 µS/cm, well inside the 1.3 µS/cm USP limit for purified water in pharmaceutical manufacturing. A 50 KLD pharmaceutical system Navbharat Water built in Hyderabad delivers 0.06 µS/cm with TOC consistently below 100 ppb, validated to USFDA requirements.
Municipal or groundwater supply typically carries 500–3,000 mg/L TDS, far above what pharmaceutical purified water, water for injection or data centre cooling can tolerate. Single-pass RO produces permeate at 10–500 µS/cm depending on feed quality; the second RO pass and EDI polishing stage close the gap. Pharmaceutical systems must also be proven, not just built. Navbharat Water provides full Design, Installation, Operational and Performance Qualification (DQ/IQ/OQ/PQ) documentation packages and designs against USP <1231> Water for Pharmaceutical Purposes and USFDA 21 CFR Part 211 good manufacturing practice. The Hyderabad system was validated to USFDA 21 CFR Part 11 requirements and has run for three years with zero out-of-specification incidents. Data centre membrane systems follow ASHRAE Guideline 12 and BSRIA BG 50, and food-grade process water is designed against FSSAI Regulations, 2011.
How long do RO membranes last and how much water do they reject?
With proper pre-treatment and automated clean-in-place, RO membranes typically last 3–5 years. Standard single-pass RO recovers 65–80% of the feed, so 20–35% becomes reject concentrate; for water-stressed sites, a second pass or reject-treatment stage can push overall recovery above 90%.
Membrane life is decided upstream. Navbharat Water systems include SDI monitoring, antiscalant dosing and automated clean-in-place, and ultrafiltration pre-treatment at a flux of 20–80 LMH protects RO membranes from particulate fouling. A membrane replacement programme is available within AMC packages. Reject volume is the other operating cost to plan for. For water-stressed sites, Navbharat Water adds a second pass or an RO-reject treatment stage, such as additional concentration or the HERO process, to recover more water from the concentrate. Feed salinity drives the equipment choice: Navbharat Water has commissioned RO systems on brackish groundwater of up to 12,000 mg/L TDS and seawater of up to 40,000 mg/L TDS, using high-pressure pumps and 8-inch seawater RO elements. RO also differs from a DM plant, which removes ions chemically with resins; the two are often paired, with DM polishing RO permeate where higher purity is needed.
