2 t/h Ultra-Pure Water (UPW) System

Technical Specification · Equipment Selection and Process Overview

Water resistivity ≥ 18.0 MΩ·cm (25°C) | Designed for the production of nanofiltration materials and high-purity rinsing water applications

catalogue

1. Overview

1.1 Equipment Overview

This equipment is a continuous ultra-pure water (UPW) preparation system with a water production rate of 2 tons per hour (at 25°C). It employs a mainstream process route comprising "pre-treatment + dual-stage reverse osmosis (RO) + electrodeionization (EDI)", ensuring that the final product water maintains a stable resistivity of ≥ 18.0 MΩ·cm (at 25°C). This meets the stringent water quality requirements for ultra-pure water required during the synthesis, dispersion, coating, modification, and final rinsing stages of nanofiltration membrane (NF) materials.

The system features a modular integrated design, comprising a pre-treatment unit, a reverse osmosis unit, an EDI fine-treatment unit, a post-treatment sterilization unit, a pure water storage and distribution unit, a PLC automatic control cabinet, and online instrumentation. It boasts a compact structure, high degree of automation, stable operation, and easy maintenance.

1.2 Application Context and Water Usage Characteristics

Nanofiltration materials and their membrane elements are highly sensitive to impurities introduced during manufacturing. Even trace amounts of ions, particles, organic compounds, microorganisms, or residual active chlorine in water can alter the surface charge of the materials, clog nanoscale pores, or induce irreversible fouling, thereby affecting their separation efficiency, flux, and service life. Therefore, the water used in the production of nanofiltration materials must meet the following requirements:

• Ultra-low ion content – prevents the deposition of metal ions (e.g., Na⁺, Ca²⁺, Fe³⁺) on the material surface or their coordination with active functional groups;

• Ultra-low total organic carbon (TOC) – prevents the adsorption of organic matter within the membrane pores, thereby avoiding flux decay;

• Ultra-low particle and microbial content – prevents nanopore clogging and biological contamination;

• No residual chlorine and oxidizing agents – protects organic polymer materials from oxidative degradation;

• Highly stable water quality – ensures consistent product performance across batches.

This equipment is designed specifically to meet the aforementioned requirements by maintaining the water resistivity at ≥ 18.0 MΩ·cm and simultaneously controlling parameters such as TOC, particulates, bacteria, and silicon dioxide, thereby ensuring the production quality of nano-scale materials.

1.3 Design Objectives and Technical Specifications

1.4 Main Features

• Mature and reliable technology: The two-stage RO process removes over 99% of ions and organic compounds, while the EDI system provides continuous deep desalination without the need for acid-alkali regeneration; the effluent conductivity remains stable at 18 MΩ·cm.

• High and stable water quality: End-of-pipe configuration featuring dual-wavelength UV disinfection at 185/254 nm combined with 0.22 μm terminal filtration, effectively degrading TOC while retaining particulates and microorganisms;

• Green Operation: EDI replaces traditional mixed-bed systems, eliminating acid and alkali discharge and complying with environmental protection requirements;

• High automation: Centralized control via PLC + touchscreen – automatic start/stop, flushing, protection, and alarm functions – reducing reliance on manual operation;

• Online monitoring: real-time display and interlocking for resistivity (conductivity), flow rate, pressure, and liquid level;

• Material Safety: Areas in contact with pure water are constructed from SUS304/316L stainless steel or sanitary-grade plastic to prevent secondary contamination.

2. Design Basis and Implementation Standards

The process design, manufacturing, inspection, and water quality classification of this equipment are primarily based on and refer to the following national and industry standards and specifications:

Note: The water quality parameters are strictly controlled in accordance with the requirements specified in the "Electronic Grade Water" (EW-Ⅰ) and "Semiconductor Grade Ultra-Pure Water" standards, ensuring compliance with the rigorous specifications applicable to the production of nanofiltration materials.

3. Raw water conditions and treated water quality

3.1 Raw water quality assumption

The system uses municipal tap water as its water source; the design has been verified against the following water quality requirements (for actual projects, refer to the on-site water quality report):

If the raw water quality is poor (e.g., high hardness, high silicon content, or high organic matter content), chemical dosing (anti-scaling/Reduction/PH adjustment) can be added during the pretreatment stage, or an ultrafiltration (UF) unit can be installed to ensure the long-term stable operation of the RO system.

3.2 Water product quality indicators (nanometer-level requirements)

The system effluent must simultaneously meet the following criteria; the core parameter – resistivity – must remain stable at ≥ 18.0 MΩ·cm at 25°C:

3.3 Key Performance Indicators (KPIs) Explanation

• Resistivity ≥ 18.0 MΩ·cm: This indicates an extremely low total ion concentration in the water and serves as the core criterion for ultra-pure water;

• TOC ≤ 30 ppb: Controls organic matter to prevent adsorption-related contamination in nanopores; safeguarded by a combination of activated carbon and 185 nm ultraviolet light;

• Bacteria ≤ 0.1 CFU/mL: Dual control via 254 nm UV sterilization + 0.22 μm terminal filtration;

• Particulate content ≤ 1 particle/mL (≥0.22 μm): Terminal microporous filtration ensures no particulate introduction during nanomaterial coating or rinsing;

• SiO₂ ≤ 2 μg/L: The high-efficiency silicon rejection capability of the two-stage RO system prevents silicon scale contamination of the nanomaterial surface.

4. Process Plan and Workflow

4.1 Process Route Selection

To meet the requirement of "resistivity ≥ 18 MΩ·cm + control of nanomaterial-grade impurities," this equipment employs a mainstream combination of "two-stage reverse osmosis + EDI," as explained below:

Note: For applications requiring a higher resistivity margin (e.g., a long-term requirement of ≥ 18.2 MΩ·cm) or where the raw water quality fluctuates significantly, an additional polishing mixed-bed unit (with nuclear-grade resins) can be installed after the EDI system as a final safeguard; this can be optionally configured as needed.

4.2 Process Flow Diagram

The complete system process flow is illustrated in the figure below; the entire process—from raw water intake to the point of use—is divided into three major functional sections: pretreatment, reverse osmosis, and final treatment.

4.3 Process Description

① Preprocessing Section

The raw water is first buffered in a raw water storage tank and then pressurized by a raw water pump before being sequentially passed through a multi-media filter (to remove suspended solids, colloids, and turbidity), an activated carbon filter (to adsorb residual chlorine, organic compounds, and odors), a water softener or a scale inhibition dosing unit (to prevent the formation of CaCO₃, MgCO₃, or silica scale on the RO membrane surface), and finally through a 5 μm safety filter to remove fine particles, thereby protecting the high-pressure pump and the RO membrane.

② Reverse Osmosis Section (Double Stage RO)

The filtered water is pressurized by a primary high-pressure pump and fed into the primary reverse osmosis (RO) unit, which retains 98%–99% of ions, organic compounds, and microorganisms; the primary RO product water is then conveyed by a secondary high-pressure pump to the secondary RO unit for further purification, after which it is stored in the RO product water tank. This two-stage RO process reduces the conductivity to below approximately 1–2 μS/cm, providing an excellent feed water source for EDI systems.

③ Advanced Treatment Section (EDI + Post-Treatment)

The RO treated water is fed into the EDI module, where continuous deep demineralization occurs under the synergistic action of an electric field and ion exchange resin; the electrical resistivity of the outlet water then rises to the range of 15–18 MΩ·cm. The water is subsequently transferred to a pure water storage tank, subjected to sterilization using an 185/254 nm dual-wavelength UV sterilizer (to degrade TOC and eliminate microorganisms), and then passed through a 0.22 μm final filtration system to remove any particulate matter before being ultimately delivered to the water supply point for nano-material production and rinsing processes.

4.4 Key Process Parameters

5. Detailed Specifications for Each Unit Equipment

5.1 Raw water storage and pressurization

The raw water tank (PE material, 2.0 m³) is equipped with a level sensor to prevent the pump from running idle; the raw water pump (SUS304, Q ≈ 3.5 m³/h, H ≈ 0.30 MPa) provides a stable flow rate and pressure for the pretreatment process, and is accompanied by a pressure gauge and inlet/outlet valves.

5.2 Pre-treatment System

The pre-treatment configuration includes an automatic backwash (multi-media/activated carbon) and regeneration (softening) sequence, which can be triggered by the PLC based on time or pressure differential settings, ensuring simple operation and maintenance.

5.3 Reverse Osmosis System (RO)

An anti-fouling aromatic polyamide composite membrane module (8040) is used. The primary RO system comprises four membrane elements (two pressure vessels, each containing two membranes arranged in a 2:2 configuration), while the secondary RO system comprises two membrane elements (one pressure vessel containing two membranes). All high-pressure pumps are vertical multi-stage centrifugal pumps (SUS304/316L), equipped with a variable frequency drive or constant pressure control system, and feature high/low-pressure protection, concentrate discharge, and flushing valves.

5.4 Electrodeionization (EDI)

Select one large-scale EDI module (with a rated treatment capacity ≥ 2.3 m³/h, e.g., the IP-LXM series or E-Cell MK series) powered by a dedicated DC power supply; after precise control of inlet water parameters (flow rate, pressure, and resistivity), the residual ions are continuously removed under the influence of an electric field, resulting in an outlet water resistivity ranging from 15 to 18 MΩ·cm. EDI requires neither acid-alkali regeneration nor chemical discharge.

5.5 Purified Water Storage

Both the RO water storage tank (PE, 1.0 m³) and the pure water storage tank (PE or SUS316L,1.0 m³) are equipped with a liquid level interlock: the water production system is activated at low liquid level and stopped at high liquid level; the water is then delivered to the end-users under constant pressure (optional: pure water booster pump + variable frequency constant pressure system).

5.6 Post-treatment and Sterilization

The ultraviolet sterilizer employs dual-wavelength lamps at 185 nm (for TOC degradation and generation of hydroxyl radicals) and 254 nm (for bacterial elimination), with an SUS304 housing; the terminal filter features a 0.22 μm sanitary-grade filter element (SUS316L housing), effectively capturing particles and microorganisms to ensure nanometer-level cleanliness at the final water usage point.

5.7 Polishing Mixed Bed (Optional)

If it is required that the resistivity be maintained at ≥ 18.2 MΩ·cm over an extended period or if the raw water quality exhibits significant fluctuations, an additional polishing mixed-bed unit (using nuclear-grade mixed-bed resin) can be installed after the EDI system as a safeguard for final deep desalination. This unit is an optional component and should be configured as needed.

6. Control and Automation System

6.1 Control System Architecture

The system adopts a "PLC + Touchscreen (HMI)" architecture, complemented by an on-site control cabinet. The PLC handles logical control, interlock protection, and data acquisition; the touchscreen provides real-time operational status, parameter settings, alarm logging, and trend display, supporting both local and remote operation and maintenance.

6.2 Automatic Operation Logic

• One-click start/stop: Automatically starts all pumps and valves in sequential order, with automatic flushing upon shutdown;

• Level Interlock: The raw water tank or purified water tank level sensor controls the start/stop operation of the water treatment unit to prevent idling and overflow;

• Automatic backwashing/regeneration: Multi-media, activated carbon, and water softening are automatically executed based on time or pressure differential;

• RO Automatic Rinse: Automatic low-pressure rinsing upon startup/stoppage to delay membrane fouling;

• Constant pressure water supply: The pure water section supports variable frequency constant pressure control, ensuring stable pressure at all water usage points.

6.3 Online Monitoring Instrument

6.4 Safety Interlocking and Alarm Systems

• High-pressure pump low-pressure protection (automatic shutdown upon insufficient water intake), high-pressure protection (overpressure relief/shutdown);

• When the water resistivity falls below the set value, an automatic alarm is triggered and the discharge mode is switched (water does not enter the pure water tank);

• Electrical protection features include: high/low water tank level detection, motor overload protection, and phase sequence or phase loss detection;

• Fault self-diagnosis and historical alarm logging facilitate operations and maintenance traceability.

7. Pipeline, Valve and Material Selection

7.1 Material Selection Principles

Adhering to the principle of "gradual purification and prevention of secondary contamination," materials contacting water of different quality grades shall be selected and used in a tiered manner:

7.2 Pipelines and Valves

The piping system utilizes sanitary clamps or heat fusion connections to minimize dead zones; the valve configuration primarily consists of pneumatic/electrical ball valves and diaphragm valves to facilitate automated control; the pure water section is designed with an appropriate slope and discharge outlet to facilitate cleaning (CIP) and drainage.

8. Main Equipment Configuration List (BOM)

The table below shows the configuration of the system's primary equipment (typical configuration; the actual setup is subject to final design confirmation):

9. Plant Facilities and Public Utilities Conditions

10. Installation, Commissioning and Acceptance

10.1 Installation

• Position, level, and secure the equipment; connect the raw water, treated water, concentrated water, drainage, and power supply according to the drawings;

• Piping hydrostatic test and flushing; electrical wiring and grounding inspection;

• Instrument calibration and PLC program downloading.

10.2 Debugging

• Step-by-step standalone system commissioning (pumps, valves, instruments) → Integrated trial operation → Verification of water quality compliance;

• Optimize the RO recovery rate, EDI current/flow rate, and UV operating parameters to their optimal levels;

• Run continuously for 24–48 h to verify the stability of water production volume and water quality.

10.3 Acceptance Criteria

Upon continuous and stable operation of the equipment, if the water production rate is ≥ 2.0 m³/h and the water resistivity is ≥ 18.0 MΩ·cm (at 25°C), and all other water quality parameters comply with the requirements specified in Section 3.2, the equipment shall be deemed to have passed acceptance inspection.

11. Operational Maintenance and Consumables

11.1 Daily Operation

• Daily inspection records of operating pressure, flow rate, resistivity, and alarms;

• Maintain the water tank level and enable automatic system operation to avoid frequent start-stop cycles;

• Regular sampling for offline parameter monitoring, including TOC, bacteria, and particulates.

11.2 Maintenance and Consumables Replacement Cycle

12. Quality Assurance and After-Sales Service

• Manufacturing shall be carried out in accordance with standards such as JB/T 2932 and GB/T 19249; hydrostatic and functional tests shall be completed prior to shipment.

• Provide documentation such as equipment qualification certificates, material certification, electrical schematic diagrams, and operation and maintenance manuals;

• Equipment main unit warranty: 12 months (from the date of successful acceptance), with lifetime technical support;

• Provide installation guidance, commissioning training, and remote/field fault response services;

• Long-term supply of consumables and spare parts, including filter elements, membrane components, and resins.

13. Technical Specifications Summary Table