How to Design 1TPH / 2TPH / 5TPH RO Plant for Drinking Water

Introduction

Small to medium reverse osmosis drinking water plants (1TPH, 2TPH, 5TPH) are widely used for bottled water factories, community drinking stations, hotels, schools, and rural water supply projects worldwide. Many integrators and end-users make costly mistakes: under-sizing pretreatment, wrong membrane selection, improper recovery setting, or insufficient high-pressure pump head. These errors shorten RO membrane life, cause frequent fouling, unstable water quality and higher running cost.

This practical design guide walks you step-by-step through designing 1 ton, 2 ton and 5 ton per hour drinking water RO systems for brackish raw water (municipal tap water / borehole groundwater, feed TDS <2000 ppm), following standard industrial RO design principles.

Step 1: Define Core Design Inputs Before Sizing

Before selecting any components, confirm these 4 critical parameters:

1. Permeate capacity: Target production rate (1TPH / 2TPH /5TPH, measured at 25°C reference temperature). Always add 10–15% safety margin for aging, temperature variation and flux decline over years.
2. Raw water analysis report: TDS, hardness, iron, manganese, residual chlorine, SDI15, pH, turbidity. This determines pretreatment configuration.
3. Target product water quality: For drinking water, permeate TDS generally 50–300 ppm, meets WHO drinking water standards, salt rejection ≥99%.
4. System recovery rate: Single stage brackish RO for drinking water: 65%–75%. Avoid pushing recovery over 75% for groundwater, it triggers calcium carbonate scaling rapidly.

Formula: Recovery = Permeate Flow / Feed Flow ×100% Concentrate flow = Feed flow – Permeate flow

Step 2: Standard Process Flow for Drinking Water RO Plant

Raw Water Tank → Raw Water Booster Pump → Multi-media Filter (Quartz Sand) → Activated Carbon Filter → Water Softener → 5μm Cartridge Precision Filter → High Pressure Pump → RO Membrane Array → Permeate Water Tank → Post Treatment (UV sterilizer / Ozone / Remineralization)

Component function overview:

• Multi-media filter: Remove suspended solids, turbidity, sediment. Prevent large particles scratching RO membranes.
• Granular activated carbon filter: Adsorb free chlorine and organics. Free chlorine will permanently damage polyamide RO membrane.
• Water softener: Reduce calcium & magnesium hardness, eliminate scaling risk on membrane surface. Mandatory if raw water hardness is high.
• 5 micron precision filter (security filter): Final safety barrier, capture fine carbon fines and particles before entering high pressure pump and membrane housing.
• High-pressure pump: Supply driving pressure for RO separation, typical operating pressure: 10–16 bar for brackish drinking RO.
• RO membrane elements: Core part to separate dissolved salts, heavy metals, bacteria and viruses.
• Post disinfection: UV or ozone for finished drinking water to inhibit microorganism growth in pure water tank.

Step3: Sizing & Membrane Configuration for 1TPH / 2TPH /5TPH RO

For drinking water RO with feed TDS <2000ppm, we select ULP / LP low pressure 4040 RO membranes (Vontron / HID / Hydranautics), widely adopted for small commercial drinking RO systems.

表格

Design flux recommendation for drinking water RO: 14–18 LMH (liter/m²·h). Do not use excessive high flux; high flux accelerates colloidal fouling and shortens membrane service life.

Step4: Instrument & Control Configuration (Critical for Stable Operation)

A qualified drinking RO plant must include monitoring and protection instruments:

• Pressure gauges: Feed pressure, pre-filter differential pressure, RO inlet pressure, concentrate pressure, permeate pressure
• Flow meters: Permeate flow meter, concentrate flow meter
• Conductivity / TDS meter: Monitor product water quality continuously
• Low-pressure protection switch: Stop high-pressure pump automatically if feed water shortage, avoid pump dry running
• High-pressure protection: Shut down pump in case of overpressure
• Automatic flush valve: Auto flush membranes at startup & shutdown to reduce salt accumulation on membrane surface
• Optional: pH / ORP transmitter for raw water monitoring

Note: pH or ORP electrode cannot directly connect to PLC; pH/ORP transmitter (controller head) is required to convert sensor signal into standard 4-20mA output.

Step5: Common Design Mistakes to Avoid

1. Ignore raw water test report, use universal configuration blindly. Groundwater with high iron/manganese needs extra iron removal filter.
2. Cancel softener to save cost. High hardness raw water will scale membrane within months.
3. Too high recovery rate. Concentrate scaling risk increases exponentially.
4. Skip activated carbon filter. Residual chlorine causes irreversible membrane oxidation damage.
5. Under-size high pressure pump without pressure margin. Water production drops sharply in cold seasons.
6. Neglect auto flushing function. Static salt concentration on membrane surface leads to fouling quickly.

Step6: Operation & Maintenance Expectation

• Pre-treatment filter media (quartz sand, activated carbon): Replacement every 1–2 years
• 5μm PP cartridge filter: Replace every 1–3 months
• RO membranes: Service life 2–3 years with proper pretreatment and regular maintenance
• CIP chemical cleaning: Perform cleaning when flux drops 10–15% or conductivity rises obviously

FAQ

Q1: What water source is suitable for these 1TPH/2TPH/5TPH RO drinking plants?

A: Municipal tap water, borehole groundwater, low-TDS surface water (TDS below 2000ppm). For brackish water with TDS >3000ppm, higher pressure design and special BW membrane will be required.

Q2: Do I need remineralization for RO drinking water?

A: RO removes almost all minerals. Some countries require adding trace minerals back for drinking water taste and local regulation. Remineralization filter can be added after RO.

Q3: Can I run the RO system 24 hours continuously?

A: Yes. Our automatic RO plants support continuous 24h running for commercial drinking water production. Daily inspection on pressure, flow and TDS is required.

Q4: What voltage options are available?

A: Customizable for global power supply: 220V single phase / 380V three phase, 50Hz or 60Hz to match local electrical standards.

CTA

If you need a customized 1TPH, 2TPH or 5TPH drinking water RO plant design, send your raw water analysis report and site requirements to our engineering team. We provide complete P&ID drawing, component list and quotation for your project. Contact us for your RO solution today.