Jun 7 2016
Microscopic Particulate Analysis ( MPA ) for Ground Water Under Direct Influence ( GWUDI ) Guide
Microscopic Particulate Analysis (MPA) For Evaluation of Ground Water
I. What is “a ground water source under direct influence of surface water”?
The EPA Guidance Manual defines a ground water source under direct influence of surface water as water in which there is either:
“significant occurrence of insects or macroorganisms, algae, organic debris, or large-diameter pathogens such as Giardia lamblia.”
or
“significant and relatively rapid shifts in water characteristics such as turbidity, temperature, conductivity, or pH which closely correlate to climatological or surface water condition.”
II. What information is useful in classification?
Historical water quality records
- At least three years of Total Coliform and/or Fecal Coliform
- Turbidity and temperature records including those of nearby surface water
- No history of a known or suspected outbreak of Giardia, Cryptosporidium or other pathogenic organisms associated with surface water that has been attributed to the
- No evidence of particulate matter associated with surface
On site inspection
- No evidence for surface water
- Sufficient distances from surface water
III. What is MPA and how can it be used to differentiate ground water under surface influence?
The premise behind the use of microscopic particulate analysis (MPA) is that surface waters are subject to contamination by pathogens such as Giardia and that there are other organisms whose natural habitat is limited to surface waters. If these surface water organisms are found in ground water, then the water is subject to contamination with Giardia cysts and other pathogens. Indicators of surface water contamination of ground waters include: Giardia, coccidia including Cryptosporidium, diatoms and certain other algae, rotifers, green plant material, and insect parts.
Cryptosporidium
Cymbella (Diatom)
Naviculla (Diatom)
IV. How is test conducted?
Samples are collected in accordance with the EPA “Consensus Method for Determining Groundwaters Under the Direct Influence of Surface Water Using Microscopic Particulate Analysis (MPA).” Two sampling events are recommended, one during a dry period and a second during a wet period. Turbidity, temperature, rainfall and stream flow records, and conductivity etc. may be used for guidance for when to test.
V. How are results interpreted?
When organisms such as Giardia , coccidian, such as Cryptosporidium, insect parts including nymphs, larvae and eggs, rotifers, diatoms and other algae are detected in groundwater, they are useful as indicators of surface contamination. The process of scoring microscopic results with relative risk factors is beneficial in classifying questionable supplies.
Primary Indicators
Giardia – A protozoan parasite. Occurrence in water sample must be confirmed by identification of two or more morphological characteristics, nuclei, axoneme and/or median body.
Coccidia (Cryptosporidium and other coccidia) – Coccidia are protozoan parasites of vertebrates. Cryptosporidium, a pathogen of concern to human health is small in size (approximately 4-7 µm diameter). Cryptosporidium is very difficult to identify without IFA staining, and its occurrence is confirmed by identification of sporozoites within the oocyst.
Diatoms – Diatoms are prevalent in creeks and streams, and they require sunlight for photosynthesis and continued survival. It is important that the diatoms contain normal internal morphology including pigment in order to be significant for the purposes of this analysis.
Other Algae – Includes several groups of algae including the green and blue-green algae (Cyanobacteria). These algae are abundant in surface water and do not generally persist in the absence of sunlight.
Insects/Larvae – This category includes insects and their larvae and eggs. Insect parts are not as significant as intact organisms since insects molt and the external skeleton could persist in water for long periods of time.
Golenkinia (Green Alga) & Cyclotella (Diatom)
Coelastrum (Green Alga)
Tribonema (Golden Alga)
Anabaena (Blue-Green Alga)
Insect Wing Scale
Rotifers – Organisms ranging in size 70-500 µm that are medium to good indicators of surface water influence, particularly when supported by the presence of other indicators.
Plant Debris – This category, in our opinion, is significant only when it relates to chlorophyll containing fragments of plant tissue, since the plant debris could persist in water for extended periods of time much beyond the viability of Giardia or other pathogen cysts.
Secondary Indicators
Nematodes – Nematodes and or their eggs are common in surface water and in ground waters with detritus and organic debris.
Crustaceans – Many species occur in surface waters.
Amoebae – Free living amoebae. Large numbers of amoebae in groundwater may indicate substantial bacterial populations or organic detritus in the water.
Non-photosynthetic flagellates and ciliates – Free-living protozoa are extremely common in healthy surface sources. Like amoebae, they feed on bacteria, algae, small metazoans, other protozoa and extraneous debris. Although many flagellates are photosynthetic, there are a number of species that grow in the absence of light providing sufficient dissolved nutrients are available.
Photosynthetic flagellates – Includes species such as Euglena. While these organisms are photosynthetic, many can persist in the dark for months and because they are motile, their presence may not be indicative of surface water contamination.
Other: Other organisms frequently seen in MPA samples include the iron bacteria. The presence of iron bacteria does not have significance for surface infiltration, but large numbers of iron bacteria can produce biofouling of the well.
The EPA risk factor tables are used to weight the results of MPA analyses. The greatest weight is given to the primary indicators.
Table 1 assigns a rating (Not Significant through Extremely Heavy).
Table 2 uses the ratings assigned by Table 1 to determine the Relative Risk Factor.
Table 1: Numerical range of each primary bio-indicator (particulate) counted per 100 gallons water.
| Indicators of surface water1 | EH3 | H | M | R | NS |
| Giardia2 | >30 | 16 to 30 | 6 to 15 | 1 to 5 | <1 |
| Coccidia2 | >30 | 16 to 30 | 6 to 15 | 1 to 5 | <1 |
| Diatoms4 | >150 | 41 to 149 | 11 to 40 | 1 to 10 | <1 |
| Other Algae4 | >300 | 96 to 299 | 21 to 95 | 1 to 20 | <1 |
| Insects/Larvae | >100 | 31 to 99 | 16 to 30 | 1 to 15 | <1 |
| Rotifers | >150 | 61 to 149 | 21 to 60 | 1 to 20 | <1 |
| Plant Debris4 | >200 | 71 to 200 | 26 to 70 | 1 to 25 | <1 |
- According to EPA “Guidance Manual for Compliance with the Filtration and Disinfection Requirements for Public Water Systems Using Surface Water Sources”, March, 1991
- If Giardia cysts or coccidian are found in any sample, irrespective of volume, score as
- Key: EH-Extremely High, H-Heavy, M-Moderate, R-Rare, NS-Not Significant
- Chlorophyll Containing
Table 2: Relative surface water risk factors associated with scoring or primary bio-indicators (particulate) present during MPA of subsurface water sources.
| Indicators of surface water1 | Relative Risk Factor3 | ||||
| EH2 | H | M | R | NS | |
| Giardia | 40 | 30 | 25 | 20 | 0 |
| Coccidia | 35 | 30 | 25 | 20 | 0 |
| Diatoms | 16 | 13 | 11 | 6 | 0 |
| Other Algae | 14 | 12 | 9 | 4 | 0 |
| Insects/Larvae | 9 | 7 | 5 | 3 | 0 |
| Rotifers | 4 | 3 | 2 | 1 | 0 |
| Plant Debris | 3 | 2 | 1 | 0 | 0 |
- According to EPA “Guidance Manual for Compliance with the Filtration and Disinfection Requirements for Public Water Systems Using Surface Water Sources”, March, 1991
- Key: EH – Extremely High, H – Heavy, M – Moderate, R – Rare, NS – Not Significant
- Risk of surface water contamination:
>20 – High risk, 10-19 – Moderate risk, <9 – Low Risk
*Note: Any finding of Giardia or Cryptosporidium results in a minimum risk factor of 20.
*Appendix 1. Tables 1 & 2 from Vasconcelos, J. 1992 Consensus Method for Determining Groundwaters Under the Direct Influence of Surface Water Using Microscopic Particulates Analysis (MPA). U.S. Environmental Protection Agency, Region 10 Oct. p. 30-31.
Jun 29 2016
LT2ESWTR Source Water Monitoring for Systems Serving At Least 10,000 People Factsheet
WHAT IS THE LT2ESWTR?
The U.S. Environmental Protection Agency (EPA) published the Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR) on January 5, 2006. The LT2ESWTR improves control of microbial pathogens. The LT2ESWTR requires source water monitoring at public water systems (PWSs) that use surface water or ground water under the direct influence of surface water (GWUDI) (i.e., Subpart H PWSs). Based on system size and filtration type, systems need to monitor for Cryptosporidium, E. coli, and turbidity.
WHAT IS THE PURPOSE OF SOURCE WATER MONITORING?
Source water monitoring data will be used to categorize the source water Cryptosporidium concentration into one of four “bin” classifications that have associated treatment requirements. The LT2ESWTR provides other options for systems to comply with the initial source water monitoring requirements:
Submit data from Cryptosporidium samples collected before the system must begin source water monitoring (i.e., Grandfathered), and the data must meets certain requirements.
Filtered systems may skip source water monitoring and commit to provide a total of at least 5.5- log of treatment for Cryptosporidium, equivalent to meeting the treatment requirement of Bin 4. Unfiltered systems skip source water monitoring and commit to provide a total of at least 3-log Cryptosporidium inactivation, which is equal to meeting the treatment requirements for unfiltered systems with a mean Cryptosporidium concentration of greater than 0.01 oocysts/L. Systems that decide to skip monitoring and provide maximum treatment must notify the state in writing.
A second round of source water monitoring will follow 6 years after the system makes its initial bin determination. Grandfathering is not available for the second round of source water monitoring.
Note: E. coli and turbidity data may not be grandfathered unless the system is also grandfathering corresponding Cryptosporidium data.
WHAT ARE THE INITIAL SOURCE WATER MONITORING REQUIREMENTS?
The source water monitoring requirements of the LT2ESWTR apply to all Subpart H PWSs. You are subject to initial source water monitoring requirements if you do not have existing monitoring data that meets grandfathering requirements. For more information on source water monitoring requirements, see EPA’s Source Water Monitoring Guidance Manual for Public Water Systems for the Final Long Term 2 Enhanced Surface Water Treatment Rule (EPA 815-R06-005 February 2006), available at www.epa.gov/safewater/disinfection/lt2/compliance.html.
Prior to beginning initial source water monitoring, you must submit a sampling schedule that specifies the calendar dates when you will collect the required source water samples. The samples must be evenly spaced throughout the monitoring period (e.g., monthly on the 15th of each month). However, the schedule may be altered to take into account holidays, weekends, or other events. All the samples must be taken within a 5-day window (i.e., you can take the sample up to 2 days before or 2 days after
the date indicated in the schedule). In addition, you must submit a description of the intended sampling location in relation to the source and any treatment processes, as well as a description of any points of chemical addition, and filter backwash recycle.
FILTERED SYSTEMS SERVING AT LEAST 10,000 PEOPLE – You must collect Cryptosporidium,
UNFILTERED SYSTEMS SERVING AT LEAST 10,000 PEOPLE – You must sample for Cryptosporidium
at least monthly for 24 months.
Alternately, you may notify the EPA or the state that you elect not to conduct source water monitoring and commit to providing the maximum treatment of 5.5 log removal or inactivation for filtered systems or 3-log inactivation for unfiltered systems.
WHEN MUST I COMPLY WITH THE MONITORING REQUIREMENTS?
The system compliance schedule is based on the population served by your system. A PWS must conduct monitoring based on the requirements of the largest system in the combined distribution system. The interconnected wholesale/consecutive systems relationships have been determined by the state.
(Schedule 1) 1
people (Schedule 2) 1
people (Schedule 3) 1
1 Your schedule is defined by the largest system in your combined distribution system.
2 State may allow up to an additional 2 years for capital improvements to comply with the treatment technique.
WHAT IS A BIN CLASSIFICATION?
FILTERED SYSTEMS SERVING AT LEAST 10,000 PEOPLE – You will be classified into a “bin” based on the results of your source water monitoring. Your bin classification determines whether further treatment for Cryptosporidium is required. A second round of source water monitoring is required 6 years after your initial bin classification and may affect your bin classification.
For systems that are:
Concentration1
Bin Classification
1 Samples must be analyzed by an approved laboratory and use EPA method 1622 or 1623.
ADDITIONAL TREATMENT REQUIREMENTS FOR FILTERED SYSTEMS – Additional treatment is required if the bin classification is a 2, 3, or 4. Refer to the table below for the additional Cryptosporidium treatment requirements.
Direct filtration
For information on the toolbox options that can be used to achieve additional log removal requirements, see the Long Term 2 Enhanced Surface Water Treatment Rule Toolbox Guidance Manual (draft version anticipated late 2006).
UNFILTERED SYSTEMS SERVING AT LEAST 10,000 PEOPLE – You must calculate an arithmetic mean of all Cryptosporidium samples concentrations required. Following completion of the second round of source water monitoring, you must provide a level of inactivation for Cryptosporidium based on the arithmetic mean of your Cryptosporidium sample concentrations.
For systems that are:
Concentration1
Cryptosporidium inactivation
1 Samples must be analyzed by an approved laboratory and use EPA method 1622 or 1623.
ARE YOU CONSIDERING MAKING A CHANGE TO YOUR DISINFECTION PRACTICES?
After completing the initial round of source water monitoring, systems that plan to make a significant change to their disinfection practice must notify the state, develop disinfection profiles, and calculate disinfection benchmarks for Giardia lamblia and viruses. To develop a profile and benchmark, PWSs must monitor at least weekly for a period of 12 consecutive months to determine the total log inactivation for Giardia lamblia and viruses. The disinfection benchmark is an indicator of disinfection effectiveness and depends upon the inactivation of Giardia lamblia or viruses. The benchmark is determined by calculating the average daily inactivation value for each of 12 consecutive months. The lowest monthly average becomes the disinfection benchmark. If the PWS has data from more than 1 year, the benchmark is the average of the lowest monthly average value for each of the years. A PWS may use grandfathered data that is substantially equivalent to develop the disinfection profiles for Giardia lamblia and viruses. The Long Term 1 Enhanced Surface Water Treatment Rule (LT1ESWTR) Disinfection Profiling and Benchmarking Technical Guidance Manual (EPA 816-R-03-004, May 2003), provides guidance for developing a disinfection profile and benchmark. EPA has developed two tools for systems to determine their disinfection profile and calculate the benchmark at the following website: http://www.epa.gov/safewater/mdbp/lt1eswtr.html.
ADDITIONAL GUIDANCE MATERIALS
The following guidance document addresses the source water monitoring requirements for the LT2ESWTR:
Source Water Monitoring Guidance Manual for Public Water Systems for the Final Long Term 2 Enhanced Surface Water Treatment Rule (EPA 815-R06-005 February 2006) – Provides surface water systems, laboratories, states, and Tribes with a review of the source water monitoring provisions. The source water monitoring guidance manual provides direction to the systems on how, where and when to monitor, how to report the data, how to submit “grandfathered” data (e.g., previously collected data), and how the data can be evaluated and used to determine risk bin classification.
For additional guidance on implementing the LT2ESWTR, you may refer to the following existing and future EPA materials:
LT2ESWTR Quick Reference Guides (Schedules 1 – 3) On-line Microscopy Training Module
On-line Sample Collection Module
Microbial Laboratory Guidance Manual for the Final Long Term 2 Enhanced Surface Water Treatment Rule (EPA 815-R06-006 February 2006)
Membrane Filtration Guidance Manual (EPA 815-R-06-009 November 2005)
Membrane Filtration Guidance Manual: Overview and Summary Factsheet (www.epa.gov/safewater/disinfection/lt2/pdfs/guide_lt2_membranefiltration_fs_final.pdf)
Ultraviolet Disinfection Guidance Manual and Workbook (final version anticipated mid-2006)
Simultaneous Compliance Guidance Manual for Stage 2 Rules (draft version anticipated mid-2006)
Long Term 2 Enhanced Surface Water Treatment Rule Toolbox Guidance Manual (draft version anticipated late 2006)
For additional information, please contact the Safe Drinking Water Hotline at 1-800-426-4791, send an email to stage2mdbp@epa.gov, or visit www.epa.gov/safewater/disinfection/lt2.
Office of Water (4606) EPA 816-F-06-017 www.epa.gov/safewater/disinfection/lt2 June 2006
By Ed Boutros • EAL News, FAQs, LT2 Cryptosporidium •