| Pretreatment and Multimedia Filtration | Removes suspended solids, turbidity, iron, manganese, and larger particulate matter before membrane treatment. | Can reduce turbidity to approximately <1 NTU when properly designed; protects downstream membranes from rapid fouling. | Usually requires periodic backwashing. Feed-water pressure commonly ranges from approximately 2 to 6 bar, depending on the system design. | Municipal water, well water, industrial utility water, and surface-water sources. | Review raw-water analysis, turbidity variation, iron and manganese levels, backwash-water availability, and media replacement intervals. |
| Activated-Carbon Filtration | Reduces chlorine, chloramine, taste-and-odor compounds, and selected dissolved organic contaminants. | Protects polyamide reverse-osmosis membranes from oxidative damage. Chlorine at the RO inlet is generally required to be effectively removed. | Requires adequate empty-bed contact time, routine backwashing, and monitoring for bacterial growth or carbon exhaustion. | Feed water containing disinfectant residuals or organic compounds. | Confirm whether the local water supply uses free chlorine or chloramine; chloramine may require specialized carbon capacity or an additional removal step. |
| Cartridge or Microfiltration | Captures fine particles and protects high-pressure pumps, RO membranes, and downstream ion-removal modules. | Common nominal ratings include approximately 1 to 5 micrometres; finer absolute-rated filters may be selected for sensitive systems. | Pressure-drop monitoring is essential. Cartridges are replaced when differential pressure or contamination reaches the specified limit. | Laboratories, semiconductor support systems, pharmaceutical utilities, and precision manufacturing. | Check filter rating, housing material, flow capacity, seal compatibility, and availability of replacement cartridges in the destination market. |
| Reverse Osmosis (RO) | Removes most dissolved salts, microorganisms, colloids, and many organic contaminants through a semipermeable membrane. | Typical single-pass salt rejection is approximately 95% to 99% or higher, depending on membrane type, feed quality, temperature, and recovery. | Often operates at approximately 8 to 20 bar for municipal feed water. Recovery commonly ranges from about 50% to 85%, depending on design and scaling risk. | Core purification stage for laboratory, healthcare, industrial, and pharmaceutical water systems. | Evaluate feed-water conductivity, hardness, silica, temperature, recovery rate, concentrate disposal, membrane-cleaning provisions, and energy use. |
| Ultrafiltration (UF) | Removes suspended solids, colloids, bacteria, endotoxins, and high-molecular-weight organic matter by size exclusion. | Typical membrane pore-equivalent molecular-weight cutoffs are approximately 10,000 to 200,000 daltons; microbial and endotoxin reduction depends on membrane integrity and operating conditions. | Usually operates at lower pressure than RO and may use cross-flow, backwash, air scour, or chemical cleaning. | High-purity process water, biotechnology, pharmaceutical water preparation, and final particulate or endotoxin control. | Confirm endotoxin-performance data, integrity-testing method, cleaning compatibility, flux, and the effect of feed-water temperature. |
| Electrodeionization (EDI) | Continuously removes ionized impurities using ion-exchange resins, selective membranes, and an electric field. | Product-water resistivity commonly reaches approximately 5 to 18 megohm-centimetres at 25°C when supplied with suitable RO permeate. | Requires low-hardness RO permeate, stable flow, suitable conductivity, and continuous electrical power. Chemical regeneration is generally not required during normal operation. | Continuous production of high-purity water for laboratories, electronics, power generation, and pharmaceutical utilities. | EDI is not a substitute for RO pretreatment. Check carbon dioxide, silica, hardness, boron, feed conductivity, and manufacturer feed-water limits. |
| Mixed-Bed Ion-Exchange Polishing | Removes residual cations and anions after RO or EDI to achieve very low ionic contamination. | Can produce water approaching 18.2 megohm-centimetres at 25°C when resin condition, flow, and feed quality are properly controlled. | Resin capacity is finite. Cartridges or tanks require replacement or off-site regeneration when resistivity declines. | Analytical laboratories, trace-element analysis, chromatography, molecular biology, and precision rinsing. | Consider resin type, exchange capacity, cartridge changeout logistics, pressure drop, and the cost of certified replacement media. |
| Ultraviolet Oxidation | Uses ultraviolet energy to reduce microorganisms and photo-oxidize trace organic compounds, especially at approximately 185 nm and 254 nm wavelengths. | UV systems may support microbial control and help reduce total organic carbon to low-ppb levels when water quality, dose, and lamp condition are suitable. | Requires adequate UV transmittance, lamp monitoring, quartz-sleeve cleaning, and periodic lamp replacement. UV does not remove dissolved ions. | Final polishing for laboratory water, semiconductor processes, analytical chemistry, and sensitive rinsing operations. | Specify UV wavelength, validated dose, sensor type, lamp-life expectation, replacement cost, and expected TOC reduction under actual flow conditions. |
| Final Point-of-Use Filter | Provides final removal of particles and microorganisms immediately before dispensing or process use. | Common membrane ratings range from approximately 0.1 to 0.22 micrometres for microbial control, subject to validated integrity and operating conditions. | Requires regular replacement, hygienic installation, low-dead-volume design, and protection against secondary contamination. | Cell culture, microbiology, analytical instruments, pharmaceutical preparation, and critical rinsing. | Check membrane material, extractables, sterilization method, flow rate, connection type, and compatibility with the intended application. |
| Storage Tank and Recirculation Loop | Stores purified water while limiting microbial growth, particulate ingress, and quality deterioration during distribution. | Maintains water quality only when the tank, piping, circulation velocity, sanitization, and environmental controls are properly managed. | Common design features include sanitary fittings, smooth internal surfaces, vent filtration, continuous recirculation, and periodic thermal or chemical sanitization. | Centralized laboratory systems, healthcare facilities, pharmaceutical utilities, and multi-point industrial distribution. | Review tank volume, residence time, loop velocity, dead legs, material compatibility, drainability, vent-filter protection, and sanitization validation. |
| Online Monitoring and Control | Measures conductivity or resistivity, temperature, total organic carbon, flow, pressure, tank level, and selected microbial indicators. | For Type I laboratory water, a common target is approximately 18.2 megohm-centimetres at 25°C; TOC targets are often in the low-ppb range, depending on the application. | Requires calibrated sensors, temperature compensation, alarm limits, data logging, and preventive maintenance. | All systems where consistent quality, traceability, and rapid fault detection are important. | Confirm calibration procedures, sensor accuracy, alarm history, remote access, audit trails, language support, and local electrical compatibility. |