Legionella growth potential of drinking water produced by reverse osm osis

Transcription

1 7 September Legionella growth potential of drinking water produced by reverse osm osis Paul van der Wielen, Kim berly Learbuch, M aart en Lut & Willem-Jan Knibbe

2 2 Legionella pneumophila in the Netherlands - ± 350 cases per year outbreak flower exhibition

3 3 Distribution/ premises plum bing system No chlorine used in the Netherlands BDOC Bacteria Protozoa Legionella pneumophila B D O C = biodegradable organic carbon

4 Groundwater treatment plant Oasen Bridging science to practice 4 - RO with remineralisation - Remove all contaminants - Reduce BDOC (AOC) <1 µg/l - Produce drinking water that limits growth of L. pneumophila

5 5 Objectives - Legionella growth potential of water Determine the Legionella growth potential of RO-water and remineralised RO water, that is produced by the pilot plant and compare to conventional drinking water, at the same location. - Legionella growth potential of materials - Determine whether different pipe materials can cause growth of Legionella pneumophila in a static batch test (BPP-test) with remineralised RO-water, produced by the pilot plant.

6 6 Legionella growth potential of water - Boiler biofilm monitor (BBM) - RO-water - Remineralised RO-water - Convential treated water - Boiler flushes 3x per hour for 20 seconds the biofilm monitor (glass rings) - Mixture cold and hot water, final temperature of 38 C - After 24 days inoculate with Legionella pneumophila serogroup 1, sequencetype 1 - Measure periodically (every two weeks) - ATP - Legionella pneumophila

7 R esults BBM s Biofilm formation Bridging science to practice 7 ATP (pg cm -2 ) RO-water Remineralised RO-water Conventional treated water Time (days)

8 8 Growth of Legionella pneumophila L. pneumophila (CFU cm -2 ) RO-water Remineralised RO-water Conventional treated water Time (days) Inoculation with L. pneumophila Legionella growth potential = 90percentile CFU biofilm (CFU cm -2 ) RO 35 Remin RO 23 Convent. 16,601

9 Comparison with other water types LGP-BBM (CFU cm -2 ) Different water types Remineralised RO-water Log (y) = 2.3 Log (x) 3.1 R² = 0.77 Bridging science to practice RO-water Conventional treated water BFP-BBM (pg ATP cm -2 )

10 Conclusion first objective Bridging science to practice 10 - The conventional produced drinking water has a relatively high Legionella growth potential - RO-water and remineralised RO-water have a very low Legionella growth potential - Due to the low BDOC-concentration in RO-water and remineralised ROwater growth of Legionella pneumophila is almost completely prevented in these water types

11 Materials Bridging science to practice 11 B D O C = biodegradable organic carbon

12 12 Legionella growth potential of materials With remineralised RO-water - Material test - Glass (negative control) - PVC-P (positive control) - Copper - PE-Xb - PE-Xc - PVC-C - PE Incubation at 37 C - Weekly water replacement - Remineralised RO-water - After 16 weeks inoculation with Legionella pneumophila serogroup 1, sequencetype 1

13 13 R esults material test Biomass Production Potention (BPP) Comparable to earlier results, with conventional treated groundwater (van der Kooij et al. 2006, van der Kooij & Veenendaal, 2007). BPP (pg ATP cm -2 ) St. dev. Negative control (Glass) Positive control (PVC-P) 14,885 3,300 Copper PE-Xb PE-Xc PVC-C PE-100 2,

14 14 Legionella pneumophila In biofilm In water L. pneumophila (CFU cm -2 ) Glass PVC-P Copper PE-Xb PE-Xc PVC-C PE-100 L. pneumophila (CFU ml -1 ) Glass PVC-P Copper PE-Xb PE-Xc PVC-C PE Time (weeks) Time (weeks)

15 15 Legionella growth potential (LGP) Negative control (Glass) Positive control (PVC-P) BPP (pg ATP cm -2 ) LGP (CFU cm -2 ) , Copper PE-Xb PE-Xc PVC-C PE-100 2, R 2 =0.81 Y=1.7x - 1.0

16 Conclusions Bridging science to practice - Conventional produced drinking water has a relatively high Legionella growth potential - In a premises plumbing system this drinking water can lead to growth of Legionella pneumophila, regardless of pipe material used 16 - RO-water and remineralised RO-water have a very low Legionella growth potential - In a premises plumbing this drinking water does not or barely leads to growth of Legionella pneumophila - The remineralised RO-water does not prevent growth of L. pneumophila on materials that release high concentrations of growth promoting compounds (PVC-P, PE, PEX)

17 17 R ecommendations - Usage of remineralised RO-water for drinking water, to prevent growth of Legionella pneumophila, as long as no growth promoting materials are used. - Be careful with the use of PE(X) materials in the premises plumbing system to limit growth of L. pneumophila - Implement a strict pass/fail criterium for the enhanced growth properties of materials

18 18 Legionella pneumophila in the Netherlands - Legionnaires disease not under control in the Netherlands - Need for effective measures that helps controlling L. pneumophila - Ban materials with high growth potential (BPP > 800 pg ATP cm -2 ) from (drinking) water systems

19 19 Bridging science to practice Thanks to: Microbial Water Quality and Health, KW R Laboratory of Microbiology, KWR paul.van.der.wielen@kwrwater.nl KW R Watercycle R esearch Institute