Remedial actions to prevent adverse effects of re-growth in networks at higher temperatures

Transcription

1 Remedial actions to prevent adverse effects of re-growth in networks at higher temperatures Susanne Grobe, Janine Wagner, Gabriela Schaule - IWW Centrum Water - Prepared enabling change 1

2 Background on Climate Change Clear signs of climate change Intergovernmental Panel on Climate Change (IPCC) synthesis report (2007) dpa, 2008 Increasing air and water temperatures Widespread snow and ice melts as well the rise of the sea-level Possible increase of medium global temperature by 0.6 C within the next 100 years Other climate projections predict an increase of 1.8 to 4 C for other scenarios Universität Duisburg-Essen, AGAK

3 Climate Change Challenge for the Water industry? Klimawandel in NRW Influence of climate change on the water industry More rapid and severe Hochwasserschutz Flood prevention Niederschlag Rain fall Verdunstung Oberflächenwasser Talsperrenbewirtschaftung Dam management raw water quality depreciation events more water-borne outbreaks Wasserversorgung Water supply Abfluss Ground Grundwasser water Gewässerbewirtschaftung Water resources management Siedlungsentwässerung Sewage water management Higher temperatures and severe droughts, followed by heavy rainfalls more flushing to the water reservoir

4 Climate Change Challenge for the water industry? Wasserversorgung Water supply Abfluss Ground Grundwasser water Klimawandel in NRW Significantly change of Influence of climate change on the water industry raw water quality with To counteract a possible climate-related negative negative impact on the Talsperrenbewirtschaftung Dam Hochwasserschutz prevention Flood water treatment plants management impact on the quality of drinking water, Niederschlag Rain fall Verdunstung and adaptation water supply Oberflächenwasser possible at different levels. networks strategies are therefore Adaption water treatment technology Water treatment technology necessary?! Siedlungsentwässerung Sewage water management Planning/management of the DWDS Gewässerbewirtschaftung Water resources climate-induced management Microbiological-hygienic monitoring of DW heating and DW-biofilms of the drinking water distribution network

5 Drinking water German drinking water ordinance General Requirements (1) The drinking water must be such, that through its consumption or use an impairment of the human health especially due to pathogens is prevented. It has to be pure and consumable. Does this have an influence on the drinking water? + 3,0-3,3 C Increase of the average annual temperatures in the distant future ( ) compared to Increase in the number of hot days (> 30 C) in Germany in the distant future ( ) compared to

6 Bacterial growth Growth of bacteria Minimum, optimum and maximum temperature of a bacterial species Optimum Organisms Survival Minimum Optimum Maximum possible ( C) ( C) ( C) Fakultative pathogenic Minimum Maximum environmental bacteria Pseudomonas aeruginosa Surrounding temperature Legionella pneumophila Survival possible J. Wingender Biofilm Centre

7 Objectives Objectives of Task were to develop technologies and practices for climate change proof water supply systems Partners: LNEC (Laura Monteiro, José Menaia) SINTEF (Bjornar Eikebrokk, Lars Hem) IWW (Susanne Grobe, Janine Wagner, Gabriela Schaule) IWW-Part: Evaluation of the influence of temperature, biodegradable organic compounds and disinfection on the biofilm formation and the influence on the water phase incorporation, persistence and re-growth of Pseudomonas aeruginosa and Legionella spp. in drinking water biofilm Prepared enabling change 7

8 Experimental approach Warming of the drinking water in the distribution systems due to the climate change? Determination/Evaluation of temperature changes and possible microbiological changes of the drinking water (Sprouting, proliferation of hygienically relevant microorganisms) Field testing drinking water, UV-disinfected, low nutrient level, C:N:P-ratio 100:45.000:380 (significant C-limitation) Biofilm reactors with surface-coupons Varying water temperatures Climatope (e. g. open land, city centre) Surface-coupons made of material relevant for distribution systems Ethylene propylene diene monomer (EPDM), Polyethylene (PE),stainless steel Management of networks Nominal diameter, flowthrough etc. Nutrient content of drinking water 5 µg/l Acetate-Equivalent Question Approach Mikrobiological characterization of the water as well as the biofilms Cultural parameters according to TrinkwV, molecular-biological parameter 8

9 Drinking water temperature ( C) Drinking water temperature Influenced by the climate? Summer > Autumn> Winter Highly sealed > less sealed Low flow rate > high flow rate 9

10 What about the microbiological drinking water quality? drinking water under nutrient poor conditions was not affected by temperature minimum and maximum values of total cell count increased significantly in the water with addition of nutrients with increasing temperature and incubation time in nutrient poor drinking water the total cell count on PE and EPDM increased with higher temperature higher temperature led to a higher distribution of total cells 10

11 What about the micrbiological drinking water quality? Temperature increase Colony count 20 C Colony count 36 C Total cell number E. coli Coliform Bakterien P. aeruginosa Legionella spec. negativ Befunde E. coli P. aeruginosa L. spec coliforme Bakterien Aeromonaden Enterokokken Very good microbiol. drinking water quality > no temperaute influence No increase of hygienically relevant microorganisms 11

12 Bacteria Where do they live? Risk of a water contamination by hygienically relevant microorganisms is possible! 12

13 What about the micrbiological drinking water biofilm quality? Colony count 20 C Colony count 36 C Total cell number E. coli Coliformic Bakterien P. aeruginosa Legionella spec. Temperature increase E. coli P. aeruginosa L. spec coliforme Bakterien Aeromonaden Enterokokken ohne Befund E. coli P. aeruginosa L. spec coliforme Bakterien Aeromonaden Enterokokken ohne Befund Sporadic presence of hygienically relevant microorganisms E. coli P. aeruginosa L. spec Temperature-dependent effect only detectable for coliformic bacteriea coliforme Bakterien Aeromonaden Enterokokken Frequency of colonization is material dependent (EPDM > PE > stainless steel) ohne Befund No complete exclusion of contamination risk possible 13

14 Experimental approach Warming of the drinking water in the distribution systems due to the climate change? Determination/Evaluation of temperature changes and possible microbiological changes of the drinking water (Incorporation, persitence and proliferation of hygienically relevant microorganisms) Laboratory experiments contamination of DW with P. aeruginosa and L. pneumophila Temperature controlled biofilm reactors with surface-coupons Varying water temperatures smallstep temperature ranges: 8 29 C Surface-coupons made of material relevant for distribution systems Ethylene propylene diene monomer (EPDM), Polyethylene (PE),stainless steel Nutrient content of drinking water 5 µg 150 µg/l Acetate-Equivalent, Question Approach Mikrobiological characterization of the water as well as the biofilms Cultural parameters, molecular-biological parameter 14

15 Pseudomonas aeruginosa Category Naturally occuring environmental bacterium (soil, water) Medical relevance Facultative pathogenic Cause of systemic and local, acute or chronic infection e.g. infections of wounds, urinary tract, skin, eyes, ears, Pneumonia Frequent source of nosocomial infections Presence in drinking water In public drinking water networks: e.g. in the context of reconstructions, repair work In drinking water installations of buildings Proliferation at conditions with high and limited nutritients in the water and in biofilms. 15

16 Legionella pneumophila Category Naturally occuring environmental bacterium (soil, water) Medical relevance Facultative pathogenic Cause of water associated infections with varying progressions Legionnaire s disease (Pneumonia, possibly with the involvement of other organs), Pontiac fever (condition similar to flu) sporadic and infrequent epidemic outcomes Presence in drinking water In public water networks: present, but no proliferation In drinking water installation of buildings: in cold and warm water Proliferation only in warmed areas, especially in biofilms 16

17 Laboratory experiments Biofilm reactor Surface-Coupons Establishment of DW-Biofilms with/without nutrients-addition, With/without continous disinfection (0,3 mg/l free chlorine) Duration: 14 days, Temperatures: C Characterization of the DW-Biofilm before colonization Colonization of hygienically rel. bacteria in DW-Biofilms by P. aeruginosa/l. pneumophila Duration: Over night, stagnating conditions Quantification of microbiol. parameters for d Influent, effluent, PE and EPDM Cultural parameter, TCC, HPC, FISH, qpcr Drinking water biofilm Temperature controlled Biofilm reactor 17

18 Log total cell count per ml What about the microbiological drinking water quality? additional biodegradable nutrients and increased temperature led to a higher total cell numbers (1.2 log decades) drinking water under nutrient poor conditions was not affected by temperature minimum and maximum values of total cell count increased significantly in the water with addition of nutrients with increasing temperature and incubation time Temperature C Incubation 14 d Incubation 42 d Prepared enabling change 18

19 What about the microbiological drinking water quality? Log total cell count per cm 2 PE in nutrient poor and nutrient rich drinking water the total cell count on PE increased with higher temperature higher temperature led to a higher Temperature Temperature ( C) distribution of total C cells Prepared enabling change 19

20 What about the microbiological drinking water quality? Log total cell count per cm 2 in nutrient poor and nutrient rich drinking water the total cell count on EPDM increased with higher temperature up to 19 C higher temperatures resulted in a decrease EPDM of total cells (> protozoa grazing) Temperature C Prepared enabling change 20

21 Incorporation in DW-biofilm P. aeruginosa - incorporation efficiency (up to nearly 100 %) is higher if: - temperature increases L.pneumophila incorporation efficiency is significantly lower than for P. aeruginosa (up tp 0.1 %) - efficiency is slightly higher if: - temperature increases

22 Incorporation in drinking water biofilm - incorporation efficiency is higher if nutrients are available (nutrients from the water phase or nutrients from the material itself, (e.g. EPDM) Prepared enabling change 22

23 Incorporation in DW-biofilm continuous chlorine disinfection without disinfection P. aeruginosa cfu/cm 2 GU/cm 2 CFU/GU median standard deviation median standard deviation 8 C, EPDM 2,03E+02 2,40E+02 7,29E+06 7,94E+06 0, C, EPDM 3,60E+04 3,38E+04 2,97E+06 2,97E+06 1,21 with disinfection 8 C, EPDM 1,21E+02 1,07E+02 1,75E+06 1,76E+06 0, C, EPDM 5,18E+04 2,22E+04 2,29E+06 1,16E+06 2,26 Legionella spp. cfu/cm 2 GU/cm 2 CFU/GU - No significant difference between incorporation efficiency with and without chlorine - Independent of temperature and used method (cultural, cultural independent) without disinfection median standard deviation Median standard deviation 8 C, EPDM 1,61E+02 1,67E+03 3,24E+06 5,51E+06 0, C, EPDM 2,84E+03 2,56E+04 2,97E+09 5,15E+09 0,0001 with disinfection 8 C, EPDM 1,10E+02 5,03E+01 2,48E+03 4,30E+02 4,41 29 C, EPDM 1,94E+03 1,83E+04 1,43E+05 2,47E+05 1,35 Prepared enabling change 23

24 Persistence in DW-biofilm Persistence of Legionella pneumophila Detection by cultivation max d after contamination Detection by FISH until the end of the experiment Detection is independent of temperature, material and nutrient No regrowth were detected. Persistence of P. aeruginosa Detection by cultivation max d after contamination Detection by FISH until the end of the experiment Detection is independent of temperature but dependent of material and nutrient Prepared enabling change 24

25 Persistence in DW-biofilm persistance in days P. aeruginosa Legionella spp cultural method qpcr cultural method qpcr 8 C- without disinfection C - with disinfection C- without disinfection C - with disinfection Persistence in presence of continuous disinfection Detection by cultivation d after contamination in low concentration near detection limit Detection by qpcr d after contamination in constant high concentrations Length of persistence is not influenced by continuous disinfection! Prepared enabling change 25

26 Superchlorination - 50 mg/l, 24 h Superchlorination Superchlorination 8 C 29 C - Superchlorination led to an inactivation of P. aeruginosa at both temperatures, as detected by cultural standard methods. - The concentration declined 4 5 log decades. At 8 C no culturable cells could be found until the end of the experiment (28 days), although with real time-pcr, constant levels of P. eruginosa could be detected. - In contrast, at 29 C, two days after superchlorination P. aeruginosa was detected with cultural methods again and up to the end of the experiment with slightly increasing concentrations. real time-pcr showed constant concentrations. This indicates that the organism was still present, possibly in the VBNC state. Prepared enabling change 26

27 Superchlorination - 50 mg/l, 24 h 8 C 29 C - Compared to P. aeruginosa, Legionella spp. was totally inactivated temperature independently after superchlorination; 8 days after disinfection no cultural signal could be detected. - After desinfection, slowly growing bacteria like Legionella spp. may have a disadvantage in growth in comparison to faster growing microorganisms such as P.aeruginosa. Prepared enabling change 27

28 Conclusions German Drinking water ordinance (TrinkwV) General Requirements (1) The drinking water must be such, that through its consumption or use an impairment of the human health especially due to pathogens is prevented. It has to be pure and consumable. Does this have an influence on the drinking water hygiene? + 3,0-3,3 C Increase of the average annual temperatures in the distant future ( ) compared to Increase in the number of hot days (> 30 C) in Northrine-Westphalia in the distant future ( ) compared to

29 Conclusions A climate-induced temperature increase of drinking water installation systems is expected during summery long heat-waves and in highly sealed areas with a low flow rate in the pipes increased also by higher temperatures of the raw water Increased temperatures as well as the nutrient content at unfavorable conditions have an effect on the microbiological-hygienic quality of the drinking water. Non depot-disinfected and nutrient limited drinking water (biological stable DW) met the limit values of the German drinking water directive even with stagnation and a clear increase in temperature up to 29 C.

30 Conclusions Laboratory experiments demonstrated, that the incorporation of P. aeruginosa and Legionella occur in drinking water biofilms e.g. during contamination events. The effectiveness of incorporation was increased with an increase in temperature and nutrient; it was not effected A potential for a contamination of by constant chlorine disinfection. the water phase can then be not The persistence of the investigated microorganisms was to some part strongly completely determined excluded by the nutrient level and not effected by constant chlorine disinfection. However these results suggest that P. aeruginosa and Legionella pneumophila are more frequently detected in biofilms at increased temperatures.

31 Prevention and remedial actions To counteract against a possible climate dependent negative influence on DW quality adaptation strategies at different levels are thus supposable. Water treatment production of biological stable drinking water e.g. optimized precipitation/flocculation, rapid filtration, activated carbon filtration and slow sand filtration lead to a quality which is less sensitive to temperature-induced biofilm formation, incorporation efficiency in DW biofilm (P. aeruginosa, L. pneumophila), persistence in DW biofilm use of chemical disinfection methods with depot effects might also lead to an improvement in the hygienic quality of DW, but it does not effect incorporation and persistence at contamination events

32 Prevention and remedial actions Management of drinking water distribution systems To avoid increased presence of hygienically relevant microorganisms in DWDS, the operators need to assure that the water does not be further warmed in the pipe network control of permitted temperature ranges of the soil and the water need to be performed, in order to identify temperature ranges at risk prevention respectively reduction of an incorrect dimensioning of the DW pipes during new and/or renovation work > sufficient water change deep relocation of drinking water pipes to noncritical areas as well as the relocation outside of pavements to shaded areas would be favorable