RO Water Quality in the Storage Tank
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) | 27 | n.d. | 8.80 | 0 | 1.29 | 0.6 | <0.01 | |||||||||
| 2007 Jan | n.d. | 2.5 × 103 | n.d. | 8.53 | 0 | 1.63 | 0 | <0.01 | ||||||||
| 2007 Feb | Significant contamination of and replacement of the water storage tank. Installation of additional filters and UV treatment lamps. | ✓ | ✓ | ✓ | ||||||||||||
| The new storage tank was equipped with a sampling port and water drainage system. | ||||||||||||||||
| n.d. | 6 | n.d. | 9.23 | 0 | 1.17 | 0.2 | <0.01 | |||||||||
| 2008 Aug | Whole system disinfection started twice a year from August 2008 after the material compatibility of peracetic acid (PAA)-based compound was confirmed in the WD. | |||||||||||||||
| 1:200, 1 h | Before | n.d. | 188 | n.d. | 5.70 | 0 | 1.28 | n.d. | n.d. | ✓ | ✓ | |||||
| After | n.d. (30 °C from 2009 Mar) | 0 | n.d. | 6.93 | 0 | 0.54 | n.d. | n.d. | ||||||||
| 2009 Mar | Water engineer failed to evaluate chemical water quality before disinfection. | |||||||||||||||
| 1:200, 1 h | Before | 127 | 1 | 0.083 | n.d. | n.d. | n.d. | n.d. | n.d. | ✓ | ✓ | ✓ | ✓ | |||
| After | 5 | 0 | 0.191 | 6.50 | 0 | 5.0 | n.d. | n.d. | ||||||||
| 2009 Jul | 1:66, 2 h | Before | 142 | 0 | 0.063 | 6.40 | 0 | 11.0 | 0.2 | <0.01 | ✓ | ✓ | ✓ | |||
| After | 301 | 0 | 0.063 | 6.80 | 0 | 0.67 | 0.2 | <0.01 | ||||||||
| 2010 Feb | 1:200, 2 h | Before | 54 | 2 | 0.052 | 7.85 | 0 | 1.65 | 0.2 | <0.01 | ✓ | ✓ | ✓ | ✓ | ||
| After | 15 | 0 | 0.083 | 7.34 | 0 | 1.16 | 0.2 | <0.01 | ||||||||
| 2010 Aug | 1:200, 2 h | Before | n.d. | 0 | 0.041 | 6.80 | 0 | 3.7 | 0.2 | <0.01 | ✓ | ✓ | ||||
| After | n.d. (20 °C from Mar 2011) | 0 | 0.020 | 6.90 | 0 | 1.08 | 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. | |||||||||||||||
| 1:200, 2 h | Before | 94 | 16 | 0.022 | n.d. | n.d. | n.d. | n.d. | n.d. | ✓ | ✓ | ✓ | ✓ | ✓ | ✓ | |
| After | 93 | 21 | 0.066 | 7.95 | 0 | 0.84 | 0.3 | <0.01 | ||||||||
| 2011 Jul | 1:200, 2 h | Before | 393 | 2 | 0.015 | 6.92 | 0 | 1.26 | 0.2 | <0.01 | ✓ | ✓ | ||||
| After | 294 | 18 | 0.022 | 7.04 | 0 | 0.73 | 0.5 | <0.01 | ||||||||
| 2012 Mar | 1:100, 2 h | Before | 117 | 10 | 0.013 | 6.64 | 0 | 1.59 | 0.2 | <0.01 | ✓ | ✓ | ✓ | ✓ | ||
| Sampling port was removed from the storage tank. Water was not sampled from the storage tank after the removal of sampling port. | ||||||||||||||||
| 2012 Jul | 1:200, 2 h | Before | 3.6 × 103 | 1 | 0.071 | 6.63 | 0 | 2.38 | 0.1 | <0.01 | ✓ | ✓ | ✓ | ✓ | ||
| It came to light that the new water engineer failed to disinfect the water drainage system after taking over the duty. Water was not sampled from the storage tank after chemical disinfection. | ||||||||||||||||
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.