Ultrapure Water Polishing SystemIt is the core equipment that ensures the quality of experimental water (resistivity ≥ 18.2 M Ω· cm, TOC ≤ 5 ppb), and its maintenance quality directly affects water quality stability and equipment life. The following provides standardized maintenance procedures and practical skills from four dimensions: daily cleaning, consumables replacement, pipeline disinfection, and UV lamp maintenance.
Step 1: Daily cleaning - prevent particle contamination and microbial growth
Purpose: To remove dust, scale, and microorganisms from the surface of the equipment and the inner wall of the water tank, in order to avoid secondary pollution.
Operation steps:
External cleaning:
Frequency: After daily use.
Tools: Soft cloth (such as dust-free cloth), neutral cleaner (chlorine or strong acid solutions are prohibited).
Method:
Wipe the equipment casing, operation panel, and water intake, with a focus on cleaning up splashing water stains and dust.
Disinfect high-frequency contact areas such as water intake buttons and touch screens with 75% alcohol swabs.
Water tank cleaning:
Frequency: Once a week (high usage laboratory can be shortened to 3 days).
Tools: specialized water tank brush (to avoid scratching the inner wall), deionized water, pH test paper.
Method:
Drain the residual water from the water tank and rinse it three times with deionized water.
Prepare a 1% citric acid solution (pH ≈ 2-3), brush the sediment on the inner wall and bottom of the water tank with a soft brush, let it stand for 30 minutes, and then drain it.
After the last rinse, use pH test strips to check the pH value of the drainage to ensure consistency with the incoming water (usually 5.5-7.0).
Pre treatment filter cleaning:
Frequency: Once a month (in areas with poor water quality, the cycle needs to be shortened).
Tools: wrench, soft bristle brush, compressed air (0.2-0.3 MPa).
Method:
Close the inlet valve, remove the PP cotton filter element, and use a soft bristled brush to remove surface particles.
For the activated carbon filter cartridge, use compressed air to blow back from the outlet to remove adsorbed organic matter.
Case: A university laboratory failed to regularly clean the water tank, resulting in a TOC value increasing from 5 ppb to 20 ppb, which affected the HPLC experimental results. Restore to standard value after cleaning.
Step 2: Consumables replacement - Ensure filtration and purification efficiency
Purpose: To replace aging consumables in a timely manner to prevent water quality deterioration or equipment failure.
Key consumables and replacement cycle:
| consumable type | replacement cycle | criteria for judgment |
| PP cotton filter element | 3-6 months | Import and export pressure difference ≥ 0.1 MPa or surface yellowing |
| Activated carbon filter cartridge | 6-12 months | The residual chlorine test strip shows positive (>0.05 mg/L) |
| Reverse osmosis membrane (RO membrane) | 2-3 years | The conductivity of the produced water is ≥ 10 μ S/cm or the desalination rate is<95% |
| Purification column (UP column) | When the resistivity is less than 15 M Ω· cm | TOC value ≥ 10 ppb or water production decreases by 30%
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Shutdown and pressure relief: Close the inlet valve and power supply, open the pure water discharge valve to release pipeline pressure. Replacement process (taking RO membrane as an example):
Dismantling old membrane: Use a wrench to loosen the membrane housing end cover and remove the RO membrane (pay attention to the direction, with the inlet end facing upwards).
Install new film:
Apply silicone grease to lubricate the O-ring of the membrane housing, install the new membrane into the membrane housing, and tighten the end cap.
After connecting the pipeline, rinse the new membrane with pure water for 30 minutes (excluding the protective solution).
Test verification: Check the conductivity of the produced water to ensure it is ≤ 5 μ S/cm (the initial value may be higher, but it stabilizes after 2 hours of operation).
Case: A pharmaceutical company failed to replace the RO membrane in a timely manner, resulting in an increase in the conductivity of the produced water to 20 μ S/cm, contaminating the cell culture medium and causing the experimental batch to be scrapped.
Step 3: Disinfection of pipelines - Inhibiting microbial growth
Purpose: To eliminate biofilm on the inner wall of the pipeline and prevent bacterial release from causing water quality to exceed the standard.
Operation steps:
Preparation before disinfection:
Turn off the device power, drain the remaining water in the water tank and pipeline.
Prepare disinfectant:
Hydrogen peroxide (H ₂ O ₂): 0.1% concentration (suitable for plastic pipelines, non corrosive).
Sodium hypochlorite (NaClO): 0.05% concentration (diluted with deionized water, thoroughly rinsed after disinfection).
Circular disinfection:
Inject disinfectant into the water tank and run the circulation pump for 2 hours (flow rate ≥ 1 L/min).
Key disinfection areas: reverse osmosis membrane pipeline, purification column inlet, and water intake terminal.
Rinse and validation:
Rinse the pipeline with deionized water until the residual chlorine in the drainage is less than 0.01 mg/L (during sodium hypochlorite disinfection) or hydrogen peroxide is less than 1 ppm.
Sampling and testing:
Microbial count: Cultivate in R2A medium at 35 ℃ for 7 days, with a colony count of ≤ 50 CFU/mL.
Endotoxin: detected by horseshoe crab reagent method, result ≤ 0.25 EU/mL (applicable to cell experiment water).
Case: A certain biological laboratory exceeded the endotoxin limit (1.2 EU/mL) due to unsterilized pipelines, contaminating the stem cell culture environment. After repair, the standard was restored through thermal disinfection (cycling at 80 ℃ for 1 hour).
Step 4: UV Lamp Maintenance - Maintain Organic Degradation Ability
Purpose: To ensure that ultraviolet lamps (UV) effectively kill microorganisms and degrade organic matter, ensuring stable TOC values.
Maintenance points:
Replacement cycle:
Low pressure mercury lamp: 8000-10000 hours (usually replaced every year).
LED UV lamp: 30000 hours (longer lifespan, but light intensity attenuation needs to be monitored).
Light intensity detection:
Measure the surface light intensity of the lamp tube using a UV radiometer (wavelength 254 nm):
New lamp tube: ≥ 80 μ W/cm ²;
When the critical value is less than 60 μ W/cm ², it needs to be replaced.
Quartz casing cleaning:
Frequency: Once every quarter (once a month in areas with poor water quality).
Method:
Dip a cotton swab in isopropanol and wipe the outer wall of the quartz sleeve to remove scale and fingerprints.
Test transmittance: If it decreases by 10% (such as from 90% to 80%), the sleeve needs to be removed and soaked in 10% hydrochloric acid for cleaning.
Heat dissipation maintenance:
Ensure good ventilation in the UV lamp compartment and avoid excessive temperature (recommended ≤ 40 ℃) that may shorten the lifespan of the lamp tube.
Case: A chemical plant failed to replace its ultraviolet lamp due to aging, resulting in a TOC value increasing from 5 ppb to 15 ppb, which affected the GC-MS analysis results. Restore standard after replacement.
Summary: Maintenance cycle and tool list
| maintenance project | period | Key tools/consumables |
| Daily cleaning | Daily/Weekly | Soft cloth, citric acid, pH test paper |
| Consumables replacement | According to the periodic table | PP cotton, RO membrane, purification column |
| Pipeline disinfection | quarterly | Hydrogen peroxide, residual chlorine test paper, R2A culture medium |
| UV lamp maintenance | every year | UV radiometer, isopropanol, cotton swab
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Through standardized four step maintenance, the lifespan of the ultrapure water machine can be extended by more than 50%, while stabilizing the water quality at 18.2 M Ω· cm (resistivity) TOC≤5 ppb、 Microbial count ≤ 50 CFU/mL, meeting the requirements of ISO 3696 Grade 1 and ASTM D1193 Type I standards