Double Pass RO System For EDI Pretreatment

This double pass reverse osmosis unit is engineered to reduce total dissolved solids, silica, and conductivity to ultra-low thresholds required for stable electrodeionization operation. By routing single-pass permeate through an intermediate tank into a second high-pressure pump and membrane array, the configuration eliminates residual ions to protect downstream electrodeionization modules from scaling and voltage spikes.

First-Pass Pressurization: Raw pretreated water enters the primary high-pressure pump to overcome osmotic pressure across spiral-wound polyamide elements.

Permeate Isolation: Initial permeate collects in an intermediate stainless steel tank while concentrated reject discharges to drain.

Second-Pass Polishing: An interstage booster pump feeds collected permeate into the secondary membrane array without anti-scalant replenishment.

Quality Monitoring: Polished permeate flows through inline resistivity sensors before reaching downstream electrodeionization systems.

Interstage pH Adjustment: Optional caustic soda injection converts carbon dioxide into bicarbonate ions for enhanced silica and boron rejection.

Interstage Degasification: Membrane contactor integration strips dissolved carbon dioxide gas prior to final membrane polishing.

Instrumentation Interlocks: Automated conductivity diversion valves reject off-spec permeate before reaching sensitive modules.

Recirculation Loops: Integrated flush circuits and automated clean-in-place connections support periodic membrane sanitation.

Silt Density Index: Less than 3.0 measured over 15 minutes to protect membrane channels from particulate blockage.

Free Chlorine: Less than 0.1 mg/L maintained via activated carbon or sodium bisulfite dosing to prevent polymer oxidation.

Suspended Solids: Less than 1.0 mg/L verified through upstream multimedia or ultrafiltration pretreatment steps.

Temperature Range: Operational capability between 10 and 35 degrees Celsius, optimized at 20 degrees Celsius.

Silica Concentration: Maintained below 20 ug/L to prevent fouling of ion-exchange resins inside chambers.

Sodium Levels: Reduced below 50 ug/L to minimize ionic load on direct current regeneration fields.

Total Organic Carbon: Kept below 500 ppb to prevent biological film accumulation on resin beds.

Hardness Levels: Calcium and magnesium reduced to undetectable limits, eliminating cathode scaling.

Voltage Stabilization: Lower feed conductivity prevents excessive electrical resistance, reducing power consumption during continuous regeneration.

Extended Lifespan: Eliminating trace hardness and silica spikes prevents irreversible scaling, extending stack lifespans beyond five years.

Resin Protection: Minimizes chemical cleaning frequency of mixed-bed ion exchange resins, reducing maintenance downtime.

Effluent Consistency: Provides stable, low-conductivity water regardless of seasonal raw water mineral fluctuations.

Power Generation Boilers: Produces demineralized water for high-pressure utility boilers to prevent turbine blade scaling.

Pharmaceutical Production: Generates feedwater meeting pharmacopeia standards for distillation without hazardous acid regeneration.

Microelectronics Manufacturing: Supplies ultra-low conductivity rinse water for semiconductor wafer fabrication lines.

Chemical Processing: Delivers high-purity water utilized as a solvent or reaction medium in specialty synthesis.

Capacity Sizing: Calculate total daily volume requirements including peak hourly demand and continuous feed flow rates.

Feedwater Mapping: Match membrane polymer chemistry against specific ion concentrations and organic loading in water analysis reports.

Energy Evaluation: Balance high-flux membrane selection against pump horsepower requirements to minimize long-term electrical expenses.

Footprint Assessment: Measure mechanical room dimensions to select between vertical multi-stage pumps and compact horizontal skids.

Frame Materials: Available in 304 stainless steel, 316L stainless steel, or epoxy-coated carbon structural steel skids.

Membrane Selection: Configurable with fouling-resistant elements for wastewater reuse or high-rejection elements for well water.

Pumping Variations: Integration of variable frequency drives on high-pressure pumps to match variable flow demands.

Automation Platform: Programmable logic controllers paired with touch screen interfaces compatible with standard communication protocols.

Pressure Testing: All pressure vessels, high-pressure tubing, and welded manifolds undergo testing at 1.5 times design pressure.

Traceability: Membrane elements, pressure vessels, and instrumentation sensors are sourced from verified manufacturers with test reports.

Factory Acceptance Testing: Complete skids undergo wet testing using simulated feedwater to verify pump performance and sequence logic.

Electrical Inspection: Control panels are built according to industrial standards, verifying proper grounding and circuit protection.

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