Nitrate in Private Water Supplies Bryan Swistock, Penn State Extension Penn State College of Agricultural Sciences research and extension programs are funded in part by Pennsylvania counties, the Commonwealth of Pennsylvania, and the U.S. Department of Agriculture.
Nitrate Sources in Groundwater Naturally occurring nitrate in groundwater is typically below detectable levels
Groundwater Contamination Barnyard, yards, dumps, mines, septic systems, etc. Surface water Well Head Contamination Soil Bedrock Aquifer Aquifer Contamination Groundwater Moves!
From U.S. Geological Survey
Nitrate Drinking Water Standards Primary MCL = 10 mg/l as NO 3 -N 45 mg/l as NO 3 3.0 mg/l often cited as human influenced
Nitrate One of the most controversial standards! Argument to relax standard o Lack of methemoglobinemia cases o Costs of treatment for public water supplies Arguments to tighten standard o Possible links to bladder cancer o Prevalence of the problem
Data Sources Statewide Survey 1989-1991 o o Penn State (Swistock, Sharpe and Robillard) 1,600 wells, springs and cisterns across PA Spruce Creek Watershed Study 2005 o o Penn State University (Swistock and Sherwin) 50 water wells intensively studied in a central PA watershed Center for Rural PA Statewide Project o Penn State (Swistock et al. 2007) o 701 samples across PA Penn State Ag Analytical Laboratory o 2,040 samples across PA from 2007 through 2016 o Samples submitted by homeowners and farmers
% Above Concentration 100 80 60 NO 3 -N in Private Water Systems (1989-1991) Sample of 1,600 systems > 3 mg/l > 10 mg/l 80 40 32 42 40 20 0 9 12 7 9 6 1 1 2 5 1 State NW SW NC SC NE SE
Mean NO3-N 5 4 3 NO 3 -N by Water Supply Type Hand-Dug Springs Drilled Well Cistern 2 1 0
Average NO3-N (mg/l) NO 3 -N and Distance to Active Field 10 8 6 4 2 0 0-100 100-500 500-1000 >1000 Distance to Active Field (ft)
Average Well Depth (ft) NO 3 -N by Well Depth 200 150 100 > 10 mg/l < 10 mg/l 50 0
Spruce Creek Well Sampling Project Penn State Center for Watershed Stewardship
Spruce Creek Well Sampling 50 private water supplies o Sampled February 22 - April 7, 2005 o 48 drilled wells, 2 springs o Drilled between 1950 and 2002 Well depths o o Average depth = 220 feet Range 35 to 725 feet Well construction o o o o 44 of 48 had casing above ground, 4 were in buried pits 13 of 48 had a sanitary well cap 5 of 48 had been grouted Only three wells had both a sanitary cap and grout seal
% above the drinking water standard Summary of Testing Results 80 60 68 60 40 20 0 10 6 6 6 0 Overall Coliform E. coli Nitrate ph TDS Arsenic
Nitrate Results 10% exceeded drinking water standard Maximum concentration 13.3 mg/l None of the 5 homes with high nitrate had treatment equipment Weak correlation with distance to cornfield and barnyard o o Farm well average NO 3 -N = 3.98 mg/l Rural home well average NO 3 -N = 2.80 mg/l No correlation with distance to septic
Average Nitrate-N concentration (mg/l) Nitrate Correlations 6 4 Cornfield Barnyard Septic 2 0 <100 ft 100-500 ft 500-1000 ft >1000 ft Distance to Activity
2006-2007 Study Funded by The Center for Rural Pennsylvania and the Pennsylvania Water Resources Research Center MWON volunteers and Penn State Staff collected samples
Methods 701 private wells throughout PA Wells had to be at least one mile apart Raw water samples collected by trained Master Well Owner volunteers and Extension personnel Analyzed for coliform bacteria, E. coli ph, lead, arsenic, nitrate, triazine pesticides and hardness Homeowner survey and volunteer survey were used to collect information about the well and management
Location of 701 Private Wells 172 volunteers collected samples, Of the 701 well samples, 79 were from MWON volunteer Wells and 622 were homeowner Wells
Wastewater Characteristics o 89% have on-lot wastewater systems 72% traditional septic system 14% sand mound 2% alternative system 1% don t know what happens to their wastewater o Septic tank pumping 28% never pumped 33% pumped > every four years 39% at least every three years
% Failing Drinking Water Standards Prevalence of Health-Related Pollutants in Rural Drinking Water Supplies 60 50 40 30 33 39 Current Study Past Studies 20 10 0 14 2 9 12 19 2 6 0.50.1
Overall = 2% exceed MCL Important Variables Explaining Nitrate Occurrence Geology Distance to cornfield Distance to other crop fields Well depth
NO3- Concentration (mg/l) Nitrate Correlation to Cornfields 5 4 3 2 1 0 <50' 50-100' 100-500' 500-1000' >1000' Distance to Cornfield
% Aware of Problem in Their Water Awareness of Nitrate Issues in Drinking Water 60 50 40 30 31 20 18 10 11 8 0 0 0
Does Awareness Translate to Action? 76% of homeowners with wells that failed standards took some action within six months to solve the problem Actions included removing source of pollution, improving well construction, buying bottled water, installing treatment
Education to Avoid Nitrate in Water Contaminant % avoiding contaminant before this study % avoiding contaminant 6-12 months after testing Coliform bacteria 33 % 50 % E. coli bacteria 42 % 71 % Nitrate 12 % 62 % Lead 0 % 75 % Arsenic 20 % 80 %
Nitrate in Private Water Supplies % Above 10 mg/l (for counties with at least 20 samples) 0% <1% 0% 3% 8% 0% 0% 0% 0% 0% 0% 3% 0% 3% 0% 0% 0% 0% 0% 0% 3% 8% 4% 4% 6% 9% 9% 3% 11% 2% 4% 23% 6% 0% 9% 20% 9% 30% 9% 3.8% of 2,040 samples > 10 mg/l
Nitrate Water Treatment Can be Point-of-Entry or Point-of-Use since it is only a drinking water issue Avoidance give young children and pregnant women alternate water Reverse Osmosis Bottled water Anion Exchange
Anion Exchange
Point of Use Treatment e.g., treat only kitchen tap Process Carbon filter Reverse Osmosis (RO) Distillation Treats Chlorine, organics Most solutes Not bacteria Many except light organics
Percent of Survey Respondents 40 How common is Water Treatment? 30 53% have some water treatment Systems capable of nitrate removal are not common 20 10 0
Summary and Conclusions Nitrate occurs in about 5% of private water supplies Much more common in southeastern and southcentral counties More common in shallow wells or springs Correlated to nearby agricultural use Relatively easy to treat or avoid