Understanding the Role of Water
Overview Water Quality Concerns Surface Waters Ground Water Preharvest Concerns Postharvest Concerns Water Treatment Types of Treatment Wash Water and Produce Sanitation GAP Water Testing Protocols
Water Quantity Concerns Increasing Population Decreasing Supply Increasing Demand
Universal solvent Transports contaminants Habitat for pathogens Water Quality Concerns Rainfall is mostly harmless until comes into contact with soil
Water Quality Concerns Contaminants bacteria, nutrients, toxic substances. Risks vary based on source water Surface water, groundwater, municipal water Dissolved solids Dissolved O2 Toxicity ph Nitrate
Water Quality Concerns Site analysis Know your watershed Point source pollution Non-point source pollution Best management practices Proposed Harmonized GAPs Standard Water System Description maps, photographs, drawing (hand drawings acceptable) or other means to communicate the location of water source(s),. Source: http://www.crowevalley.com/4/4_4/images/watershed_labeled_hor.jpg
Surface Water Surface water impairments from agricultural urban wildlife sources (Nutrients, sediment, bacteria, pesticides, ) Lawns, ranches, farms, construction/development, wildlife
Groundwater Water wells Potential for contamination Manage surface runoff Co-mingling of groundwater Septic systems Chemical storage Well head protection Abandoned wells Capping/plugging wells When is a well abandoned? When should a well be capped?
3 Major Areas Addressed by California GAPs Metrics Water sampling all sources with metrics established Soil amendments manure based amendments and non-synthetic crop treatment certification Animal encroachment and adjacent land metrics
Water Treatment Testing frequency depends on source Water quality tests vary based on what you are testing for Some are expensive Use indicator tests to identify if more testing is warranted generic E. coli
Types of Treatment Treatment varies based on constituents that must be removed Basic methods Filtration Adsorption Disinfection Ozonation Ultraviolet Light Chlorination
Filtration Physical removal of suspended solids Microfiltration, Ultrafiltration, Nanofiltration, Reverse osmosis Size dependent Filtration maintenance Source water quality Type of filtration
Adsorption Material is attracted to the surface of the adsorptive material Activated carbon ANSI/NSF certified
Disinfection Intended to destroy or inactivate harmful organisms in the water Primary methods Ozone Ultraviolet (UV) light Chlorine
Disinfection Ozonation Disinfects by introducing ozone gas (O 3 ) in to the water Oxidizes organic materials Formed when O 2 is exposed to electrical voltages Very toxic
Disinfection Ultraviolet Light Functions by altering DNA of organisms ANSI/NSF Standard 55 Class A (40 mj/cm 2 ) May be used as primary disinfection device Class B (16 mj/cm 2 ) Provides additional protection for water that already meets EPA standards
Disinfection Chlorination Provides a residual treatment Effectiveness is influenced by: Water ph, temperature, and concentration level Available in various forms Dry, liquid, and (gas - not recommended) ANSI/NSF Standard 60 Calcium hypochlorite dry solid form Sodium hypochlorite liquid form (no fragrances) Most bleach products for pools contain cyanide (not recommended)
Ozonation disinfects by introducing ozone gas into the water? 1. True 2. False 0% 0% 1 2
Postharvest Water must be potable (<2 generic E. coli/100mls, drinking quality) for all post-harvest uses: Hygiene of workers Washing produce Transporting Cooling Processing Temperature Difference - Not greater than 10 degree F
Clean Greens Study Looked at microbiological quality of produce (arugula, cilantro, parsley, spinach, mustard greens, collards, dill, and cantaloupe) from field to loading on truck. Johnston et. al 2005. Journal of Food Protection 68:1840-47 Also, looked at the microbiological quality of the different water sources (irrigation, wash, rinse, ice) and workers hands. Not yet published
Water and Produce Sampling Scheme Field Crop Distribution Produce manually removed from field bins Wash Tank Produce packed into boxes and top-iced Packaging Rinse Conveyor belt Produce rinsed with water (Antimicrobial agent may be added) Produce sample collected Water sample collected
10 Total Aerobic Bacteria 7 Total Enterococcus 8 6 5 Log CFU/g 6 4 Log CFU/g 4 3 2 2 1 0 Field Wash Rinse Box 0 Field Wash Rinse Box Sample Location Sample Location Parsley Coliforms Levels from Field to Box E. coli Levels from Field to Box 8 Total Coliforms 6 E. coli 5 6 4 Log CFU/g 4 Log CFU/g 3 2 2 1 0 Field Wash Rinse Box 0 Field Wash Rinse Box Sample Location Sample Location
10 Total Aerobic Bacteria 7 Total Enterococcus 8 6 5 Log 10 CFU/g 6 4 Log 10 CFU/g 4 3 2 2 1 0 Field Wash/Rinse Conveyor Belt Box 0 Field Wash/Rinse Conveyor Belt Box Sample Location Sample Location Cantaloupe 6 Total Coliforms 6 E. coli 5 5 4 4 Log 10 CFU/g 3 2 Log 10 CFU/g 3 2 1 1 0 Field Wash/Rinse Conveyor Belt Box 0 Field Wash/Rinse Conveyor Belt Box Sample Location Sample Location
What does potable water mean? 1. Well water 2. Surface water 3. Water from a pot 4. Water of drinking quality 0% 0% 0% 0% 1 2 3 4
Other Studies using 200 PPM Chlorine vs. Commodity Water Rinse Pathogen Water Log reduction 200 ppm chlorine Cilantro E. coli O157:H7 1.1 1.2 Cantaloupe Salmonella 0.5 1.9 Cantaloupe E. coli O157:H7 0.0 0.5 Cantaloupe Salmonella 0.7 1.8 Brussels sprouts Listeria monocytogenes 2.3 1.3 Tomatoes Salmonella 0.0 1.2
Texas A&M Spinach Study Treatment Log Reduction E. Coli O157:H7 Salmonella Water Wash 0.7de 0.7de Ozonated Water 30 min. Chlorine dioxide gas 30 min. Chlorine dioxide gas 1 hr. Ozonated Water 15 min. Calcium Hypochlorite 200ppm, free chlorine 0.6cde 1.0cde 0.7e 0.3e 0.7de 0.6de 1.1c 0.9c 1.0cde 0.7cde Peroxyacetic Acid 1.1cd 0.8cd Lactic Acid 2.7a 2.3a
Irrigation source type: Preharvest Surface: greatest chance of contamination Groundwater: less Municipal: least Methods: Drip: least Furrow: less Overhead spray: greatest chance of contamination
Most Calif. GAPs Relate to Water Preharvest foliar (contact) <126 E. coli per 100 mls (rolling geometric mean of 5 numbers) single sample <235 E. coli per 100 mls Preharvest non-foliar (non-contact) <126 E. coli per 100 mls (rolling geometric mean of 5 numbers) single sample <575 E. coli per 100 mls Post harvest (contact) < 2 E. coli per 100 mls single sample
Range of generic E. coli Levels Number of CFU s or MPN s per 100 ml (single sample value) for LGMA California LGMA Irrigation Water Criteria for generic E. coli Recommended Water Use <1 to 234 Water would be acceptable for all types of irrigation. 235 to 574 Water should not contact edible portion of plant. Ex. drip irrigation. > 575 < 126 rolling geometric mean from 5 samples. Water is unacceptable for any type of irrigation purpose. These values are currently utilized by the California Leafy Greens Marketing Agreement. These values are under the clean water act for ambient water quality criteria for bacteria in recreational fresh water, CFR 131.41
Under current guidelines, which method of irrigation poses the least risk for contamination? 1. Center pivot 2. Flood 3. Drip 4. All pose equal risks 0% 0% 0% 0% 1 2 3 4
Water Study on Microbial Content of Irrigation Water Prior to Application on Crops in Texas
# of samples # of exceeds Minimum value Maximum value Geo. mean of sample values Fronton 43 10 6 1119.85 51.86 Rio Grande City 51 19 2 2420 84.88 Hidalgo 30 11 15 1300 114.29 Las Milpas 9 1 32.3 2419 61.63 Pharr 28 10 2 2419.2 95.24 Progreso 17 3 4 420 37.07 San Benito 12 4 9 >2400 54.44 Brownsville 2 0 21 68.7 37.98 El Jardin 33 22 12 2419.2 263.66
Results from Rio Grande River Total samples 225 Years August 2001 through March 2006 Number of exceedances with rolling geometric mean of <126 MPN of generic E. coli per 100 mls was 80 or 35.6% of the time Number of exceedances with a single sample value (<394 MPN) was 40 or 17.7% of the time Source: Rio Grande Water Master
Number of Samples Distribution of generic E. coli Test Results for Various Texas Counties 2008-09 45 40 35 30 Drip 39 37 Irrigation <====================================== = 25 20 15 10 5 Furrow or sprinkle irrigation <============================ 9 = Unacceptable irrigation water =======> 3 2 0 <1 1-100 101-234 235-574 575-2400 generic E. coli CFU/ 100 mls
Number of Samples Distribution of generic E. coli Test Results for Hidalgo County 2008-09 25 20 15 10 5 0 22 Furrow or sprinkle irrigation <======================== 6 Drip Irrigation <================================ = 2 2 <1 1-100 101-234 235-574 575-2400 generic E. coli CFU/100 mls Unacceptable irrigation water ========> 1
Number of Samples Distribution of generic E. coli Test Results for Frio County 2008-09 9 8 7 6 5 4 3 2 1 0 8 Drip Irrigation <========================================== Furrow or sprinkle irrigation <================================= = 3 2 0 0 <1 1-100 101-234 235-574 575-2400 generic E. coli CFU/ 100 mls = Unacceptable irrigation water ========>
Number of Samples Distribution of generic E. coli Test Results for Starr County 2008-09 9 8 7 6 5 4 3 2 1 0 8 Drip Irrigation <====================================== == Furrow or sprinkle irrigation <============================ 2 = 1 <1 1-100 101-234 235-574 575-2400 generic E. coli CFU / 100 mls 0 Unacceptable irrigation water ========> 1
Where did the California/Arizona Leafy greens Marketing Agreement get their current water criteria guidelines from? 1. Current scientific research on irrigation water quality 2. Standards from the Environmental Protection Agency 3. A table for recreational water use based on levels of generic E. coli from the U.S. Fresh Water Act 4. None of the above 0% 0% 0% 0% 1 2 3 4
GAPs Water Testing Protocol Preferred method: Use sterile sample container (some labs want their own containers) but wash hands thoroughly with soap and use disposable gloves to collect at least 100 mls. Keep sample cool and do not hold for more than 2 to 3 hours. Ship overnight and follow lab recommendations but most labs want to test at 24 hours after collection. Recommend Coli-lert method with upper limit of 2,400 MPN of generic E. coli per 100 mls (not presence/abs Coli-lert). Other EPA methods: mtec, mod mtec (1603), mcoliblue Not EPA approved: petri film, SimPlate