4/15/215 BACTERIAL CONTAMINATION OF WATER WELLS AND SPRINGS Bryan Swistock Water Resources Specialist Penn State Extension Department of Ecosystem Science and Management Microbiological Parameters Standard Plate Count Heterotrophic Plate Count total count, plate count, bacterial count, water plate count, total bacterial count High SPC interferes with TC test Total Coliform (many environmental sources) Viruses (rotovirus, hepatitis, etc.) Protozoa Giardia, Cryptosporidium, Non-coliform pathogens H. pylori, Salmonella, Pseudomonas, S. typhi, Legionellae, Chlostridium, etc. Opportunistic pathogens Staphlyococcus aureus, Aeromonas hydrophila 1
4/15/215 Coliform Bacteria Aerobic and facultative anaerobic gram negative, non-spore forming, rod shaped bacteria that ferment lactose broth with gas formation within 48 hours at 35 C. Many sources! indicator organisms Total Coliform (many environmental sources) Fecal Coliform (mostly E. coli) Other Pathogenic Coliform (Enterobacter, Klebsiella, etc.) E. coli (good fecal indicator) Pathogenic E. coli Why Worry About Microbes in Water? 1971-94 data 57, waterborne illnesses reported Most of bacterial origin 8% linked to viral agent 47% undetermined Most illnesses are probably unreported 2
Percent Contaminated 4/15/215 Sources of Microbial Contamination Barnyard, yards Septic system Well Head Contamination Insects Small mammals Surface water Aquifer Contamination Groundwater Flow 6 5 4 3 2 1 Aquifer Contamination Coliform Bacteria E. coli Bacteria All New Wells (n=24) Carbonate (n=6) Non-carbonate (n=18) Swistock et al., 25 Journal of Environmental Health 3
4/15/215 PREVENTING PROBLEMS WITH PROPER WATER WELL CONSTRUCTION 5 sanitary well cap Fewer than 2% of home and farm wells in PA have this sanitary construction 12 above ground 1 4 sloping ground casing to bedrock 2 grout seal 3 bedrock BUT: there are no statewide standards or requirements for private water well construction in Pennsylvania! 4
Percent Contaminated 4/15/215 Effect of Well Construction on Bacterial Contamination 6 Coliform Bacteria 5 E. coli Bacteria 4 3 2 1 1 2 3 4 5 (3%) (1%) (41%) (3%) (12%) (4%) Number of Well Construction Features Swistock et al., 213 Journal of Environmental Health Important Factors Related to Bacterial Contamination Identified in Various Studies Soil and bedrock types Condition of septic system Construction and depth of well # of home residents Density of animals and septic systems near water supply Recent weather conditions Distance to source - setbacks 5
4/15/215 Setback Examples (highly susceptible sites) Ford et al., 198 164 wells Rapidly developing portion of Colorado 2 foot setback, 2-acre lots size recommended Pang et al., 23 New Zealand, sandy soils Virus removal 55% filtration, 45% Die off Bacteria removal 88% filtration, 12% die off Necessary setback for drinking water supply ~ 15 feet Longevity of Bacterial Contamination Die off proportional to nutrient and carbon source in well Biofilms can protect bacteria Most bacteria attached to surfaces as biological slimes or as floating biocolloids (may be 6-3 species of bacteria) Slimes attract metals and slough off thus changing water quality characteristics Shock chlorination of a well may not kill the entire accumulation on surfaces E. coli (Conboy and Goss, 21) 99.9998% reduction in 2 days 2-3 months for reduction below pathogenic dose Some lived as long as 5.5 months 6
4/15/215 Water Testing Total coliform, fecal coliform, E. coli Inexpensive, easy Many labs offer this testing E. coli on EMB agar Methods Multiple-Tube Fermentation (MPN) statistical method with five tubes Presence/Absence method Membrane Filtration (MF) All based on collection of 1 ml samples in sterile containers Run water, remove aerator, sterilize faucet, etc. Non-coliform bacteria testing is more difficult to find Issues with Bacteria Testing Availability of testing labs Season, climatic conditions Homeowner versus trained technician Sample location, volume, holding times Differing methodology Presence/absence vs numeric 7
% Aware of Problem in Their Water 4/15/215 Testing is Critical Low Homeowner Awareness Swistock et al., 213 Journal of Environmental Health 6 5 4 3 31 2 18 2 1 11 8 Coliform Bacteria E. coli Bacteria ph Nitrate Lead Arsenic Pesticides Determining Sources of Bacteria FC/FS Ratio > 4. = human source.6 to 4. = undetermined <.6 = animal (~.5 = wild animals, ~.1 = cattle) Only valid for recent pollution (24 h) because FS die more quickly E. coli warm blooded animal source F-RNA bacteriophages (coliphages) Viruses that attack E. coli, similar to most enteric viruses, persistent, poorly sorbed, conservative estimate Clostridium perfringens occurs in animal waste, useful in combination with other tests Coprostanol produced from cholesterol in intestines by microbes, often found in water contaminated by wastes DNA Source tracking techniques 8
Percent of Isolates or Private Wells 4/15/215 Source Determination Example: Berks County, PA 1 wells from farms or rural homes 34% contained TC, 18% contained FC Source of bacteria in wells (FC/FS ratio) 1% human 4% animal 5% undetermined Statistically significant correlations between Septic system age and fecal coliform Septic tank size and fecal coliform Number of household residents and fecal coliform Well depth and fecal coliform 5 Sources of E. coli Bacteria 4 3 Individual Isolates (n=213) Wells (n=79) 2 1 Likely Animal Probably Animal Inconclusive Probably Human Likely Human n/a Mixed Sources Source of E. coli Bacteria 9
% Contaminated Cornell 1979 Sharpe 1985 Ohio USGS 1988 Berks Co., 1989 PA USGS 1994 PDA, 1996-98 Wyoming Co., 23 Swistock 28 4/15/215 Frequency of Occurrence Research Results 1 8 6 Occurrence of Coliforms in Private Wells Total Coliform Fecal Coliform E. coli 4 2 1
4/15/215 Example Overall of Land = 33% Use exceed Impact MCL Important Variables Explaining Occurrence of Bacteria Geology Well Construction Moisture Conditions 11
% with Bacteria 4/15/215 Bacterial Contamination of Water Sources 1 9 8 7 6 5 4 3 2 1 7 private water supplies - 212 Coliform Bacteria E. coli Bacteria Springs Hand-Dug Wells Drilled Wells Type of Water Supply Occurrence of Pathogens 1 8 6 Sample of 4 wells February May 22 5 4 2 % with total coliform % with known pathogens 5 Swistock et al., 25 Journal of Environmental Health 12
% Detected 4/15/215 Variability and Testing Issues Research Results Problems with Microbial Water Testing Temporal Variability! 1 Total Coliform 8 E. coli 6 Individual wells varied from > 2 to zero within months 4 2 Fall 21 Feb-2 May-2 Swistock et al., 25 Journal of Environmental Health 13
E. coli (colonies per 1 ml) 4/15/215 25 2 Moisture Increases Bacteria in Wells 15 1 5 16% 84% -3-2 -1 1 2 3 Palmer Z Index (Soil Moisture) Swistock et al., 213 Journal of Environmental Health Bacteria Methods Issues Sample Volume Total coliform bacteria 12 samples during 22 from private wells Membrane filtration of 1 and 2 ml 71 produced negative results for both 39 positive for both, no significant difference in numbers 1 (8%) produced negative result at 1 ml but positive at 2 ml (< 5 colonies per 1 ml) 14
4/15/215 Bacteria Methods Issues Bias from sample method/location 49 wells that routinely tested positive were re-tested in 27 with and without sterilization of faucet No difference in results (p value =.62) Sample location Bacterial contamination = 33% from faucets, 36% from pressure tank Research Results Solving Microbial Contamination 15
4/15/215 shock chlorination May work for small numbers of coliform bacteria Canadian Study (Oliphant et al., 22) Study area High density of septic systems, sandy soil, shallow wells 4% contamination from total coliform 15% contamination from fecal coliform Shocked wells TC returned to all in 3 to 21 weeks Returned more quickly in those with high count Very rapid return of SPC indicated biofilm 16
% Contaminated 4/15/215 Effect of Shock Disinfection & Sanitary Well Cap 1 9 8 7 6 5 4 3 2 1 15% success all on wells with small # of bacteria Coliform Bacteria E. coli Bacteria pre-shock one month one year Swistock et al., 25 Journal of Environmental Health What About Treatment? Bacterial treatment relatively easy Requires clear water Methods Boiling Iodination Continuous chlorination UV light Ozonation 17
Percent of Survey Respondents 4/15/215 4 3 2 Water Treatment 53% report some water treatment Average cost = $1,127 Some unnecessary 48% from obvious stains, tastes 32% from water test results 2% inherited from previous owner 1 Softener Sediment Carbon Oxidizing Filter UV Faucet RO Chlorine Aeration Acid Neut. Distillation Anion Exchange Chlorination Required for public water supplies Effective for bacteria and viruses at low concentrations Protozoans require superchlorination that is normally not recommended (need filtration) On private water supplies, chlorination is most often chosen when other oxidation treatment is needed Mechanism = oxidation of cell protein cell wall rupture Chlorine demand = inorganic and organic materials in water that oxidize Several chlorine carriers Sodium hypochlorite liquid Calcium hypochlorite pellet 18
4/15/215 Chlorination Simple feed pump can deliver liquid Trying to achieve.3 to.5 mg/l for 3 minutes of contact time Advantage = residual Water must be pre-filtered Chlorine carriers produce hypochlorous acid (HOCl) and hypochlorite (OCl) depending on ph HOCl about 1X more effective, favored at low ph Ultraviolet Light Usually preferred to chlorine Shown to be effective on: Bacteria, viruses Cryptosporidium oocysts H. pylori NSF Certification Class A vs. Class B (supplemental) U-V Sterilizer Disadvantage no residual water must be clear U-V Tube 19
4/15/215 Ultraviolet Light Important factors Irradiance = light intensity Turbidity UV absorbance = expressed as fraction UV dose = irradiance x time x area Flow rate Systems sized for various flows (i.e. 24 gpm) to meet dose requirements Penn State Cooperative Extension Resources 2