Pharmaceutical Water Systems: WPU, Purified Water, WFI, GMP & Validation

Pharmaceutical Water Systems: WPU, Purified Water, WFI, GMP & Validation

🎯 Objectives

  • Understand the available specifications for water for pharmaceutical use (WPU).
  • Select the appropriate water quality for specific applications (APIs, dosage forms, sterile vs. non‑sterile).
  • Apply GMP principles to the design, installation, and operation of water systems.

excluded Water for administration to patients in formulated state & small‑scale pharmacy compounding.

📌 Background

Control of water quality is critical across production, storage, and distribution. Water is drawn on demand and is not batch‑released before use – microbiological tests lag behind usage. Hence, microbial control is a high priority.

  • Microorganisms can proliferate in treatment components, storage, and distribution.
  • Minimise contamination through: proper design, periodic sanitization, and preventive measures.
  • Different grades of water are required depending on the route of administration.

⚙️ General principles

Design & qualification

Systems must be designed, installed, commissioned, qualified, and maintained to ensure reliable quantity and quality. Validation is essential; capacity must consider current and future demands.

Recirculation & monitoring

All systems should enable appropriate recirculation and turnover. Regular monitoring of chemical, microbiological, and endotoxin parameters is required, with trend analysis and records.
  • Use of systems after initial qualification (IQ, OQ, PQ) and any modification must be approved by QA via change control.
  • Sanitisation procedures must be validated, and removal of sanitising agents verified.

💦 Types of water

🚰 Drinking water

Supplied under continuous positive pressure, from natural or stored sources. Typical treatment: desalinisation, softening, ion removal, particle reduction, antimicrobial treatment. May come from public supply or on‑site processing.

🧪 Bulk purified water (BPW)

Prepared from drinking water. Meets pharmacopoeial chemical & microbiological purity. Protected from recontamination. Produced by RO, RO/EDI, vapour compression, etc. Alert levels determined from system knowledge.

💉 Bulk water for injections (BWFI)

Prepared from purified water. Highest quality pharmacopoeial WPU. Not sterile, but an intermediate bulk product. Must meet chemical, microbiological & endotoxin specifications. Some pharmacopoeias constrain permitted purification techniques.

USP categories

  • Bulk monographed: purified water, water for injection, water for hemodialysis, pure steam.
  • Sterile monographed: sterile purified water, sterile WFI, bacteriostatic WFI, sterile water for irrigation, sterile water for inhalation.
  • Non‑monographed: drinking water, ammonia‑free, CO₂‑free, distilled, de‑ionized, filtered, high‑purity, de‑aerated, oxygen‑free, etc.

🧬 Quality of water for pharmaceutical use

WFI (sterile products)

Biologics (vaccines, ATMP), parenterals, haemofiltration, haemodiafiltration, peritoneal dialysis, irrigation solutions.

Purified water (non‑sterile)

Vaccines for non‑parenteral use, oral, nasal/ear, rectal/vaginal preparations.

Purified water (sterile)

Ophthalmic (excluding ATMP), cutaneous preparations.

Purified water (manufacturing)

Granulation, tablet coating, formulations prior to non‑sterile lyophilisation. WFI is used prior to sterile lyophilisation.

🔬 Water purification systems

Selection factors: final water quality, quantity, feed‑water quality & seasonal variation, support facilities, sanitization strategy, equipment reliability, yield, life‑cycle costs.

  • Design considerations: plant room location, temperature extremes, leachates, corrosion resistance, hygienic design, system configuration to avoid microbial proliferation, tolerance to cleaning/sanitizing agents.
  • Production of drinking water: no prescribed methods; typical processes: desalinisation, filtration, softening, disinfection, iron removal, precipitation.
  • Storage & distribution: closed tanks with protected vents, visual inspection, drainable and sanitizable. Pipework must be drainable/flushable.
⚠️ Microbiological control: sand filters, carbon beds, softeners are susceptible. Use back‑flushing, chemical/thermal sanitization, frequent regeneration.

🧰 Materials, storage & distribution

  • Material compatibility: non‑leaching, corrosion‑resistant (PW, BHPW, BWFI are highly corrosive), smooth internal finish (avoid crevices), weldable (operator qualification, weld logs).
  • Suitable materials: SS 316L, polypropylene, perfluoroalkoxy. uPVC for less pure water (ion exchangers).
  • Storage vessel: capacity based on generation rate and demand; short‑term reserve for failure/sanitisation events. Spray‑ball devices, bacteria‑retentive hydrophobic filters, bursting discs with rupture indicators.
  • Distribution: continuously circulating pipework loop. Filtration in loops is not recommended (may conceal contamination).
  • Heat exchangers: double tube plate or double plate‑and‑frame; utility at lower pressure than WPU (not typical for BWFI).
  • Circulation pumps: sanitary design, seals to prevent contamination; standby pumps should avoid dead zones.

🦠 Bio‑contamination control techniques

  • Continuous turbulent flow circulation; minimise pipe length; avoid dead legs; hygienic diaphragm valves; sloped and drainable pipework for steam‑sanitised systems.
  • Inhibition by: UV radiation, system heat (>65 °C), periodic hot water sanitisation (>70 °C), superheated water/clean steam, chemical sanitization (ozone, hydrogen peroxide, peracetic acid).

📋 Start‑up, commissioning & validation

Three‑phase approach (proves reliability and robustness):

Phase I (2 weeks) – intensive monitoring; system operates without failure; water not used for FPP. Develop SOPs, alert levels, test‑failure procedures.
Phase II (2 weeks) – continued intensive monitoring; refined SOPs; water may be used for FPP; demonstrate consistent operation within ranges.
Phase III (1 year) – routine monitoring; evaluate seasonal variations; water used for FPP; confirm reliable performance.

Continuous monitoring: online (flow, pressure, temperature, conductivity, TOC) + offline (physical, chemical, microbiological). Trend analysis within two sigma; set alert/action levels.

Maintenance and system reviews

  • Maintenance program: defined frequencies, calibration, SOPs, approved spares, clear plans, review after completion.
  • System reviews (regular): team from Engineering, QA, Microbiology, Operations, Maintenance. Review changes, performance, quality trends, failures, OOS results, logbooks, SOP status.
  • Inspection/audit: current P&ID, sampling plan, training, alert/action levels, trend evaluation, change control, deviations, system condition, calibration.

📚 References

  • ✓ WHO guideline for drinking water quality
  • ✓ ISPE Water and Steam Systems
  • ✓ ASME — BPE 2000 Bioprocessing Equipment Standard
  • ✓ European Pharmacopoeia · United States Pharmacopoeia · International Pharmacopoeia
  • ✓ PIC/S Inspection of Utilities