RO Water Quality in the Chamber of the WD
A. Microbiological & Chemical Quality
| Chemical Disinfection Dilution rate & Disinfection time | Sampling Before/After Disinfection | Colony Counts (CFU/100mL) | Endotoxin (EU/mL) | pH* | Water Hardness (ppm CaCO3) | Conductivity (μS/cm)* | Chloride (mg/L) | Iron (mg/L) | Maintenance of Expendable Parts | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| R2A (20 or 30 °C, 7 days) | SCDA (35 °C, 48 h) | AC Filter | RO | IE Resins | UF | MF | UV Lamp | |||||||||
| 2006 Dec | Installation of washer-disinfector (WD) & reverse osmosis (RO) plant. | ✓ | ✓ | ✓ | ||||||||||||
| n.d. (not done) | 59 | n.d. | 8.77 | 0 | 23.9 | 1.9 | <0.01 | |||||||||
| 2007 Jan | n.d. | 2.5 × 103 | n.d. | 7.77 | 0 | 22.5 | 2.6 | <0.01 | ||||||||
| 2007 Feb | Significant contamination of and replacement of the water storage tank. Installation of additional filters and UV treatment lamps. | ✓ | ✓ | ✓ | ||||||||||||
| n.d. | 2.3 × 103 | n.d. | 9.45 | 0 | 18.8 | 1.3 | <0.01 | |||||||||
| Significant contamination persisted in the WD chamber. RO water manufacturer offered to disinfect the whole water system using peracetic acid (PAA)-based compound. | ||||||||||||||||
| 2008 Aug | Whole system disinfection started twice a year from August 2008 after the material compatibility of PAA-based compound was confirmed in the WD. | |||||||||||||||
| 1:200, 1 h | Before | n.d. | 6.0 × 103 | n.d. | 7.31 | 0 | 8.65 | n.d. | n.d. | ✓ | ✓ | |||||
| After | n.d. (30 °C from 2009 Mar) | 188 | n.d. | 6.50 | 0 | 7.4 | n.d. | n.d. | ||||||||
| 2009 Mar | Water engineer failed to evaluate chemical water quality before disinfection. | |||||||||||||||
| 1:200, 1 h | Before | 2.9 × 103 | 3 | 1.121 | n.d. | n.d. | n.d. | n.d. | n.d. | ✓ | ✓ | ✓ | ✓ | |||
| After | 21 | 0 | 0.685 | 7.80 | 0 | 9.8 | n.d. | n.d. | ||||||||
| 2009 Jul | 1:66, 2 h | Before | 1.1 × 104 | 0 | 0.315 | 6.40 | 0 | 11.0 | 0.6 | <0.01 | ✓ | ✓ | ✓ | |||
| After | 1.3 × 103 | 0 | 1.060 | 6.80 | 0 | 1.0 | 0.5 | <0.01 | ||||||||
| 2010 Feb | 1:200, 2 h | Before | 490 | 0 | 0.180 | 7.74 | 0 | 1.8 | 0.6 | <0.01 | ✓ | ✓ | ✓ | ✓ | ||
| After | 217 | 0 | 0.327 | 7.46 | 0 | 1.33 | 0.6 | <0.01 | ||||||||
| 2010 Aug | 1:200, 2 h | Before | n.d. | 0 | 0.423 | 6.90 | 0 | 3.9 | 0.5 | <0.01 | ✓ | ✓ | ||||
| After | n.d. | 0 | 0.364 | 6.95 | 0 | 1.1 | 0.2 | <0.01 | ||||||||
| 2011 Mar | New water engineer took over the duty from his predecessor in March 2011, and numerous operator errors occurred in the system maintenance. (20 °C from Mar 2011) | |||||||||||||||
| 1:200, 2 h | Before | 886 | 0 | 0.170 | 8.30 | 0 | 54.7 | 1.1 | <0.01 | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | |
| After | 21 | 0 | 0.220 | 7.13 | 0 | 10.15 | 0.7 | <0.01 | ||||||||
| 2011 Jul | 1:200, 2 h | Before | 1.9 × 103 | 0 | 0.282 | 6.58 | 0 | 9.35 | 0.2 | <0.01 | ✓ | ✓ | ||||
| After | 252 | 15 | 0.170 | 7.02 | 0 | 8.52 | 0.5 | <0.01 | ||||||||
| 2012 Mar | 1:100, 2 h | Before | 56 | 0 | 0.268 | 6.57 | 0 | 9.34 | 0.6 | <0.01 | ✓ | ✓ | ✓ | ✓ | ||
| After | 47 | 0 | 0.199 | 7.10 | 0 | 9.7 | 0.6 | <0.01 | ||||||||
| 2012 Jul | 1:200, 2 h | Before | 1.1 × 103 | 0 | 0.324 | 7.05 | 0 | 20.0 | 1.2 | <0.01 | ✓ | ✓ | ✓ | ✓ | ||
| The microfilter (MF) was replaced with a new one to prevent bacterial contamination arising from the contaminaed filter. | ||||||||||||||||
| After | 570 | 0 | 0.116 | 6.10 | 0 | 9.56 | 0.8 | <0.01 | ||||||||
The values in bold failed to satisfy AMMI TIR34:2007.
↵* Temperature correction was performed at 25 °C. AC, activated charcoal; RO, reverse osmosis; IE, ion exchange; UF, ultrafilter; MF, microfilter; UV, ultraviolet.