Key Messages from a decade of applied research into the quality of roof collected rainwater supplies. Dr Peter Coombes

Transcription

1 Key Messages from a decade of applied research into the quality of roof collected rainwater supplies Dr Peter Coombes

2 Introduction Over 2.3 million Australians rely on rainwater tanks for drinking water supplies Over 6.3 million Australians use rainwater supplies No evidence of wide spread health impacts or epidemics Rainwater tanks used for non drinking uses in urban areas can significantly improve the security of regional water supplies However, ongoing speculation about the quality or potential of rainwater supplies since the 1800s This presentation provides key insights from a decade of research into rainwater supplies

3 Introduction Information in the presentation from multiple field and laboratory studies Brisbane City field trial (30 sites) over 2 years South East Australia (300 + sites) over 3 years Newcastle field trials 6 PhD research programs

4 Recent health surveys Heyworth et al. The risk of attaining highly credible gastrointestinal symptoms (HCG) in 4-6 year old children was significantly less among children drinking rainwater alone Compared with drinking chlorinated & filtered public mains water Rodrigo et al. The risk of HCG was not appreciable for households drinking untreated rainwater Compared to treated rainwater

5 RAINWATER TANK Soil and leaves enter damaged stormwater tank when ever it rains

6 Roof Water Quality Results Item Roof Tank surface Tank supply HWS Fecal Coliforms (CFUs/100 ml) Total Coliforms (CFUs/100 ml) HPC (CFUs/ml) Pseudomonas (CFUs/100 ml) 49,825 6,768 4,433 0 Ammonia (mg/l) Nitrate (mg/l) <0.05 <0.05 Lead (mg/l) <0.01 <0.01 <0.01 Zinc (mg/l) Treatment Train!

7 Inner city house at Maryville

8 Average water quality results at Maryville Parameter Unit Roof Point of supply Hot water Guideline Fecal Coliforms CFU/100 ml 135 <1 0 0 Total Coliforms CFU/100 ml Heterotrophic plate count CFU/ml 1, NA Pseudomonas Sp. CFU/100 ml 59,600 1,673 0 NA Dissolved solids mg/l Suspended solids mg/l Nitrite mg/l Ammonia mg/l Lead mg/l 0.01 <0.01 < Zinc mg/l

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10 Location or Criteria Average water quality results at various locations FC (CFU/ 100 ml) TC (CFU/ 100 ml) Pseudomonas Spp. (CFU/ 100 ml) Heterotrophic plate count (CFU/ml) Surface 108 1,050 3,100 1,050 Mid depth Bottom ,060 1,252 Cold tap < Hot tap 0 2 <1 <1 Guideline 0 0 NA 200* A natural rainwater treatment is evident PCR analysis revealed that majority of Coliform bacteria were Bacillus Spp. Metal and chemical parameters within guidelines

11 The Treatment Train: Roof Inoculation Roof Survival Loss of organisms Entry to Tank Loss of organisms Available Supply Pump Loss of organisms Loss of organisms Hotwater system Loss or organisms Ingestion/Inhalation Loss of organisms Above M.I.D. Below M.I.D. Mild Illness Severe Illness

12 A bio-reactor Key processes are activated in rainwater storages: Settlement Flocculation Bio-reaction Competitive exclusions Biofilms A rainwater stormwater exhibits different behaviours at various locations Water surface Rainwater Tank Biofilms Water surface micro-layer Bio-reactor Sludge

13 Biofilms Growth of Biofilms a) Initial colonisation by single type of bacterium b) Development of more complex layers with multiple bacteria c) Mature biofilm with cell aggregates, interstitial pores and conduits

14 Biofilms Key concept At low nutrient concentrations there are advantages for microbes to form attachments to containment surfaces. Develop in complexity Become efficient in the removal of dissolved organics and inorganics Key findings Biofilms form in rainwater tanks Significant removal of bacteria and metals from the water column Bacteria in biofilm 1280 to times bacteria in water column Lead in biofilm 250 to times lead in water column The sludge is also a biofilm Deposition rates 0.6 to 7.8 mm/year ecoli in sludge times water column Lead in sludge times water column

15 BCC Hotwater HWS Temp Parameter <50 C C >60 C No. Samples Mean Min Max Coliforms E. coli HPC Coliforms E. coli HPC Coliforms E. coli HPC

16 D-value Table 55 C (SE) 60 C (SE) 65 C (SE) Enterococcus faecalis (environmental) 906 (±15) s 131 (± 12) s 19 (± 1) s E. coli O157:H7 (Pathogenic) 337 (± 21) s 69 (± 4) s 3 (± <1) s E. coli O3:H6 (non-pathogenic) 314 (± 20) s 41 (± 1) s 3 (± <1) s Shigella sonnei 305 (± 18) s 39 (± 5) s 4 (± <1) s Pseudomonas aeruginosa 116 (± 9) s 45 (± 3) s 3 (± <1) s Serratia marcescens 71 (± 3) s 10 (± <1) s <2 s Salmonella typhimurium 34 (± 3) s 6 (± <1) s <2 s Klebsiella pneumoniae 19 (± 2) s <2 s <2 s Aeromonas hydrophila 50 C =16 (<1) s 55 C =3 (<1) s 60 C = <2 s Legionella pneumophila <1620 mins (54 C) s 9 s (66 C)

17 Survivors (%) Survivors (%) Enriched Sample TDA (PCR Identified Survivors) C Time (seconds) C 65 C Time (seconds) Surviving Species Class Initial Mid Lat e Flavobacterium Env. + Pantoea agglomers. Env. + Pseudomonas fulva Env + Acinetobacter Env. + Serratia marcescens Env/ent + Enterobacter horm. Env/ent + Aeromonas hydrophila Env/ent + Kurthia gibsonii Env. + + Kleb pneumoniae Env/ent + + Enterococcus hirae Enter. + + Escherichia coli Enter. + + Enterococcus faecalis Enter. + + Stenotrophomonas maltophilia Env Bacillus cereus Spore Bacillus thuringiensis Spore Bacillus sphaericus Spore Bacillus sp. B Spore + + +

18 Rainwater ecosystem A range of analysis methods were utilised including PCR sequencing > 200 species and > 80 genera identified The microflora in rainwater tanks is consistent with natural ecologies Dominated by core environmental and soil bacteria (Bacillus sp. and other ubiquitous species) This is the resident ecosystem Coliforms and other species associated with faecal material < 15% of species, < 1.5% of abundance Neither persistent or abundant Demonstrated mechanism of competitive exclusion

19 Elements in rainwater Analysis of rainwater samples for over a two year period for the South East of Australia using ICP-MS 88% of rainwater and 93% of mains water samples complaint with guidelines Infrequent exceedance of guidelines for Iron 2% Lead 7% Nickel 2% Zinc 2%

20 Concluding observations Applied research into the performance of carefully monitored demonstration sites is important Has exposed many myths and assumptions about quality of rainwater supplies Led to the discovery of the rainwater treatment train Processes in the rainwater treatment train include: flocculation of organic, metallic and chemical contaminants Settlement Formation of biofilms Competitive exclusion of bacteria

21 Concluding observations Biofilms were found in rainwater tanks Consist of a core group of environmental bacteria such as Bacillus Sp. Field studies shows that bacteria is eliminated by domestic hot water systems with temperatures >52 C Laboratory studies show that pathogens were rapidly removed from rainwater at temperatures >55 C Rainwater tanks function as ecosystems with self-regulatory processes First flush of about 20 Litres, leaf diverters and location of water supply from mm about the base of tank was beneficial.