Lecture 24 Flashcards
What are the methods of water system sanitisation?
chemicals: Uses oxidising agents such as halogenated compounds (chlorine gas) UV Light: Uses UV light at 254nm to disinfect water continuously.
Filtration: Removes microorganisms by passing water through a filter.
Ultrafiltration: Filters particles as small as 0.01 μm in diameter.
Thermal Methods: Uses heat or steam to kill microorganisms.
What chemicals are used for water sanitisation and how are they validated?
Chemicals used: Halogenated compounds (e.g., sodium hypochlorite, chlorine gas), hydrogen peroxide.
Validation: Requires demonstration of adequate chemical concentrations throughout the system and effective removal of chemical residues from the equipment after sanitisation.
How effective is UV sanitisation and what are its advantages and disadvantages?
Effectiveness: UV light is effective in controlling microbial load in clear water and can destroy all known species of waterborne microorganisms. It is particularly effective against Pseudomonas aeruginosa.
Advantages: Does not affect the physical or chemical properties of water, does not introduce foreign flavours or residues, and requires little maintenance.
Disadvantages: UV light has weak penetration powers and water downstream of the UV unit is not protected.
How is UV sanitisation validated?
UV sanitisation is validated by performing total viable counts (TVCs) on water before and after treatment.
What types of water filtration are used and how is their effectiveness validated?
Filtration: Reduces the bioburden in water using filters with a maximum pore size of 0.22 μm for sterilisation.
Validation: Microbiological monitoring of the water, regular sterilisation or replacement of filters, and testing filter integrity.
What is ultrafiltration and its role in water treatment?
Ultrafiltration (UF): Filters particles down to 0.01 μm in diameter.
Use: Controls endotoxin levels and can be used in the production of Water for Injection (WFI), but offers no residual effect and does not protect downstream water.
What are thermal methods of water treatment and their validation?
Thermal Methods: Includes heating, circulating hot water, and using steam to kill microorganisms.
Validation: Includes a heat distribution study to ensure sanitisation temperatures are reached throughout the system, and total viable counts.
What are the recommendations to minimise biofilm growth on water treatment systems?
Minimise nutrient concentration in the water.
Use smooth materials to prevent microorganism adhesion.
Regular cleaning and biofilm removal at short intervals.
Dry the system completely when possible.
What is biofilm disinfection and sterilisation?
Biofilm Disinfection: Microorganisms in biofilms are difficult to penetrate, requiring high disinfectant concentrations.
Sterilisation: Kills bacteria but does not remove the biofilm entirely.
Effective Disinfectants: Hydrogen peroxide and ozone are effective sterilisation mechanisms.
What is the frequency of sanitisation, validation, and preventative maintenance for water treatment systems?
Frequency of Sanitisation: Based on system monitoring to maintain microbiological control.
Validation: Demonstrates the system’s ability to reduce microbial numbers to acceptable levels.
Preventative Maintenance: Ensures the water system remains in control, with trend analysis of microbiological data serving as an alert mechanism for maintenance.
