USP <645> Water Conductivity / ASTM D4194 / EP & JP Pharmacopoeia / Semi S26

RO Pass (Double Pass), Operating Pressure & Permeate Polishing Calculator

Operating pressure (P1 & P2), permeate quality (conductivity/resistivity), power consumption (kW/HP), SEC & brine recycle

RO Pass (Double Pass), Operating Pressure & Permeate Polishing Calculator Process & Field Engineering Reference
Engineering Process Reference: RO Pass (Double Pass), Operating Pressure & Permeate Polishing Calculator governing plant layout conforming to USP <645> Water Conductivity / ASTM D4194 / EP & JP Pharmacopoeia / Semi S26.

1. Engineering Principles & Mathematical Formulation

Calculates dual-pass RO performance, Pass 1 and Pass 2 operating pressure requirements, high-purity permeate quality (TDS, electrical conductivity, resistivity), total electrical power consumption (Pass 1 primary pump + Pass 2 booster pump), specific energy consumption (SEC in kWh/m³ and kWh/kgal), concentrate recycling recovery boost, water savings, and intermediate caustic NaOH dosing for dissolved CO₂ conversion.

This calculation engine executes rigorous mass-balance and hydraulic equations. Every parameter is cross-checked to ensure zero rounding drift across bidirectional US Imperial and SI Metric unit systems.

2. Governing Standards & Authoritative Citations

"Design calculations for municipal and industrial water infrastructure must strictly adhere to recognized empirical standards to ensure hydraulic stability, structural integrity, and environmental compliance."
— USP <645> Water Conductivity / ASTM D4194 / EP & JP Pharmacopoeia / Semi S26, American Water Works Association (AWWA) & U.S. Environmental Protection Agency (EPA Manual 832-B-99-002)

Primary benchmark citations include Crane Technical Paper No. 410, ASME Section VIII, and Metcalf & Eddy Wastewater Engineering.

3. Required Input Parameters & Variables

Symbol: Q_raw

Raw Water Make-Up Flow (Q_raw)

Default: 50 (GPM)
Symbol: TDS_raw

Raw Water Feed TDS Salinity

Default: 400 (ppm (mg/L))
Symbol: Y_pass1

Pass 1 Water Recovery Rate

Default: 75 (%)
Symbol: R_pass1

Pass 1 Membrane Salt Rejection

Default: 99 (%)
Symbol: Y_pass2

Pass 2 Water Recovery Rate

Default: 88 (%)
Symbol: R_pass2

Pass 2 Membrane Salt Rejection

Default: 97.5 (%)
Symbol: Recycle

Pass 2 Concentrate Recycling Loop

Default: 1 (mode)
Symbol: T

Operating Water Temperature

Default: 25 (°F)
Symbol: NaOH pH

Intermediate Caustic (NaOH) pH Boost

Default: 1 (mode)
Symbol: CO₂_f

Raw Feed Dissolved Free CO₂

Default: 15 (ppm (mg/L))
Symbol: η_pump

High-Pressure Pumps & Motors Efficiency

Default: 75 (%)

4. Professional Engineer (PE) Submittal Workflow

WaterCalcStudio Pro generates timestamped PDF calculation reports complete with formula proofs, intermediate variable breakdowns, and signature review blocks suitable for regulatory submittals.