La Manzanilla salt water beach, Mexico's west coast (C) Daniel Friedman Water Tests for Swimming Safety
Water test options & standards for swimming safety at lakes & at salt water beaches

  • SWIMMING WATER TESTS - CONTENTS: options for testing swimming water for coliform level for swimming safety at lakes, rivers & ocean or salt water beaches. Marine water or seawater sanitation tests, testing standards, test procedures, & contaminants.
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Water safety testing for coliform levels: water test options, procedures & standards for checking the safety of water at swimming areas for lakes, ponds, streams, rivers, and ocean beaches. Water test options & recommendations for fresh water & salt water beaches.

This article describes useful methods for testing swimming beach water for safety at fresh water and salt water beaches. We discuss the common water contamination concerns, the telltale or most common markers or tests such as testing for coliform or E-coli bacteria in swimming water, and we'll discuss special measures appropriate when testing for coliform in salt water. The article includes research citations, water testing standards citations, and sources for water testing materials.

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Ocean & Fresh Water Beach Swimming Water Safety & Sanitation Tests

Alligator at an estuary emptying into the ocean along a publich beach in La Manzanilla, Mexico (C) Daniel FriedmanOur associate Steve Vermilye (d. 2001) worked as a teenager rowing a River Keeper about in New York's lower Hudson River where they spotted and reported industrial and sewage pipes spilling directly into the river.

[Click to enlarge any image]

Some similar contaminant sources continue around the world today. However according to the U.S. NRDC every U.S. coastal state has at least one beach with pollution problems. (NRDC 2014)

While most sources blame storm water for beach pollution (heavy rains overwhelm local sewage processing plants causing discharge of sewage into the ocean), there may be other pollution sources that have not been detected.

Watch out: when considering swimming beach safety, don't worry so much about water pollution that you fail to observe other serious and immediate hazards such as riptides, lightning hazards, cuts from stepping on debris, or alligators such as this one waiting patiently for us to step into her water at an estuary spilling into the ocean after a storm at La Manzanilla on the west coast of Mexico.

Storm waters wash not only contaminants but also alligators out into the ocean. Preferring inland waters these alligators make their way back upstream following the storm.

Water test kit providers for swimming water, lake water, ocean water testing for sewage contaminants - Marine Water Testing Kits & Procedures

La Manzanilla salt water beach, Mexico's west coast (C) Daniel Friedman

  • Ammonia test kits for sea water: Hanna Instruments provides the HI 3826 Ammonia Test Kit for Sea Water, a colorimetric test for ammonia in seawater, typically operating in the 0.0 - 2.5 mg/L range using the Nessler chemical method are sold for measuring the concentration of ammonia in rivers and drinking water reservoirs.

    Ammonia in turn may be an indicator of other types of contaminants. This is not a direct test for pathogens such as Total coliform or E. coli.
  • elAgua Water Test Kits, DelAgua Water Testing Limited Unit 2 The Old Dairy Church Lane Lower Fyfield Marlborough SN8 1PX United Kingdom, Tel: +44-0-1672-861-198, Email: [Pending company response - Ed.]
  • Enterolert by IDEXX, distributing water test materials world wide, IDEXX Laboratories, Inc. One IDEXX Drive Westbrook, Maine 04092 USA Tel: 1-207-556-4496 or Tel: 1-800-321-0207 Fax: 1-207-556-4630 , Email: Website:

    The Enteroalert® test is a 24-hour test for the detection of Enterococci using ASTM MEthod #D6503-99. This test for enterococci in water is the "gold standard" for testing beaches. The tests are simple and inexpensive; unfortunately the lab needs a $4000 machine plus an incubator, UV light and some other gear in order to process the test samples - equipment that most small water testing labs around the world simply don't have installed and probably cannot afford.
    • Less than 1 minute of hands-on time. Results in 24 hours rather than 48 to 72 hours.
    • Sensitive to 1 enterococci/100 mL. Enumerates up to 2,419 enterococci per 100 mL without dilutions (with Quanti-Tray®/2000). Less subjective interpretation.
      50% fewer false positives and 95% fewer false negatives than the standard membrane filtration (MF) method.1
    • Up to 12-month shelf life minimizes waste. 24-hour test saves incubator space.
  • Parker Kittiwake, Marine Water & Sewage Effluent TEst Kits, Website:, Tel: USA: 1-713-255-7255, UK +44 1 903 731 470 The company provides other marine test kits as well, such as a Marine Hygiene Test Kit for Legionella bacteria used at offshore installations. Quoting the company's description of their Marine Water test kit:
    This is a legislation driven requirement under the ILO Maritime Labour Convention 2006. Suitable control schemes with adequate marine water testing and monitoring will aid with the compliance of the current IHR (2005), ILO 178 (2009) and ILO MLC (2006), which enters into force from January 2012. These products provide real time analysis and simple to perform tests needing no specialist training.
    Included among the company's test are : Biological - Coliform, E.Coli, Pseudomonas Aeruginosa, Enterococci, HPC (Total viable count).
  • Simpltek Water Testing, Simpltek, 8 Byron Road. Commack, NY 11725, Tel: 1-631-864-0099, Email:, or, Website: Alex Astachovsky at Simpltek offered this advice for beach water sanitation safety testing:

    We recommend a professional Micro Tester Pro box 30 or 8 tests for multiple testing. If the user needs to do a few tests, they can use single stand alone Micro Inspector consumer test. We also offering a variety of chemical tests: Ammonia Nitrogen, Chlorine DPD, Hardness, Iron, Phosphate Ortho and Zinc in professional and consumer format.

    Coliform testing in fresh water or marine waters: the company informs us that the following two coliform test kits will perform adequately in marine waters (seawater or ocean beach water). Product instructions are given here:
    • Micro Inspector Coliform - a consumer water test kit using a self-filling ampoule & syringe.
    • Micro Tester Pro Coliform - Professional water test kit for users needing to perform multiple tests. The Coliform test will perform "as is" (no dilution or other requirements) in fresh or sea water.

      Simpltek also suggests these other biological tests:
    • E-coli test, no specific requirements for fresh water testing. To eliminate false positive results for marine water dilution 1:10 - 1:100 required. - Needed: a Black (UV) Light to view a test results (BLACK LIGHT & UV LIGHT USES).

  • Total Microbe test, from Simpltek will detect any/all aerobic and facultative bacteria, non specifically (Coliform, E-coli, Giardia, etc, it's a huge list). Simpltek points out that this test is very important for this simple reason - when you are testing for specific bacteria, you missing others. It will perform "as is" (no dilution or other requirements) in fresh or sea water.

    [However as we explain at WATER TEST PROCEDURE, testing for Coliform or E-Coli is recommended by the US EPA and other expert sources as a most useful general screen for biological water contaminants - Ed.]

Watch out: testing recommendations for swimming water safety vary between fresh water and salt water. At "Clean Beach Water Testing Guides" in this article (below) see our US EPA excerpts pointing out the importance of testing marine waters (salt water) for enterococci rather than relying on E-coli tests (which are fine for fresh water).

Watch out: also that testing methodology is as important as using a recommended test method for swimming or recreational water sanitation- safety. For example the frequency and response of water sample collection after events (e.g. storms) will be as critical as using a recommended water testing method. In short, exactly how, where, and how often water samples are collected are important in forming reliable beach safety or sanitation test data.

Watch out finally for confusing precision (precise counts of E-coli or Enterococci) versus accuracy. Water sampling in large bodies of water is vulnerable to more variation among individual samples than you might guess, even when samples are collected at the same time and very nearly at the same location. - Boehm (2003) & Santoro, Boehm et als (2008).

And Wheeler et als (2003) report that these bacteria may be present even in wet beach sand (you don't have to go into the water) while others report the bacteria may be reintroduced into water even from temporary residence in dry beach sand - Abdelzaher (2010). . Also see ACCURACY vs PRECISION of MEASUREMENTS

Slanetz Barteley culture media for enterococci showing example growth - adapted from Biokar Diagnostics
  • Slanetz & Bartley MF Media is a dehydrated agar-based culture media (recipe includes about 8 ingredients) used to test for enterococci. This test was originally intended for water supplies (that is, not swimming beaches) and is described as follows, quoting from Oxoid,

    Technique: The Environment Agency ’Microbiology of Drinking Water 2002’6 recommend the use of Slanetz and Bartley medium for the enumeration of enterococci in water supplies, as do ISO in the standard for water quality7. The water is filtered through a membrane filter which is then placed on the surface of a well dried plate of the medium.

    Plates are incubated at 35°C for 4 hours and then at 44-45°C for 44 hours. Membranes are examined, with a hand lens in a good light, and all red or maroon colonies counted as enterococci.
    Slanetz & Bartley1 originally devised this medium to detect and enumerate enterococci by the technique of membrane filtration, but it has also proved useful as a direct plating medium2,3.

    The medium is very selective for enterococci and, when it is incubated at elevated temperatures (44-45°C), all red or maroon colonies may be accepted as presumptive enterococci4,5. Burkwall and Hartman showed that the addition of 0.5ml of `Tween 80’ and 20ml of a 10% solution of sodium carbonate or bicarbonate to each litre of medium of a modified formulation of Slanetz and Bartley Medium was of value when examining frozen foods for enterococci;

    the original article (Burkwall M. K. and Hartman P. A. (1964) Appl. Microbiol. 12. 18-23.) should be consulted for procedural details.

    Slanetz & Bartley MF Media and Quanti-Tray® have been studied (by IDEXX) and compared to these methods for testing for Enterococci in recreational waters. IDEXX reports that both methods produced comparable results and that Enteroalert had a 25% lower false positive result rate (4.2% vs 6.2% in absolute numbers) than the Slanetz & Bartley Media approach. - retrieved 8/22/14, original source:

    Slanetz & Bartley MF Media is available as a dehydrated culture media from various sources including
    • Biokar Diagnostics – Rue des Quarante Mines – ZAC de Ther – Allonne – B.P. 10245 – F60002 Beauvais Cedex – France Tél : + 33 (0)3 44 14 33 33 – Fax : + 33 (0)3 44 14 33 34 – www.biokar-di, website:

Other Sea Water Tests & Testing Instruments Not Suitable for Ocean Beach Water Sanitation Testing

  • Hanna Instruments sells a very wide range of testing instruments and kits world wide. Contact: HANNA instruments, Rhode Island 584 Park East Drive Woonsocket, RI 02895 Phone: 800.426.6287 • 401.765.7500 Fax: 401.765.7575 Customer Service: Technical Support: General Sales:
    This company does not, however, provide test kits for bacterial contamination.
    To consult with or purchase testing instruments from Hanna Instruments in Mexico see
  • Hydrometers, Refractometers and Salinity monitors are use for saltwater reef and marine aquarium testing but not for ocean swimming beach sanitation tests.
  • Photometer tests for use in Sea Water: a photometer such as the YSI Photometer can be used to test for certain sea water parameters of interest such as alkalinity, ammonia, calcium(hardness), chlorine, nitrates, nitrites, phosphate, permanganate, potassium, sulphates and sulfides.

    This test is not suitable for checking directly for bacterial pathogens such as coliform or E. coli. - YSI Corp., 1725 Brannum Lane, Yellow Springs OH 45387, USA, TEl: 1-937-767-7241, TEl: 001-800-765-4974, Website:, Email: - retrieved 8/22/14, original source:
  • Watch out: salt water aquarium test kits are not suitable for testing ocean beach swimming water. Salt water aquarium test kits are intended to focus on salt water quality as it must be maintained for saltwater and reef aquarium keepers, addressing concentrations of ammonia, nitrite, nitrate, phosphate, pH, alkalilnity, calcium and copper.

Beach Water Testing Agencies & Associations

La Manzanilla salt water beach, Mexico's west coast (C) Daniel Friedman

  • "Testing the Waters 2014" A Guide to Water Quality at Vacation Beaches [In the U.S.], Natural Resources Defense Council, NRDC,
    Website: This agency offers beach water testing advice and provides beach pollution information for beaches in many U.S. states. - retrieved 8/21/2014, original source: NRDC at

    The NRDC also offers this beach sanitation-safety advice

    Whenever possible, swim at beaches that your research shows have the cleanest water, are carefully monitored, and have strict closure and advisory procedures. If your beach is not monitored regularly, there are some things you can do to avoid swimming in polluted water:
    • If possible, choose beaches that are on open waters and away from urban areas. They frequently have cleaner water than beaches in developed areas or in enclosed bays and harbors with little water circulation.
    • Look for pipes along the beach that drain stormwater runoff from the streets, and don't swim near them. Avoid swimming in beach water that is cloudy or smells bad.
    • Keep your head out of the water.
    • Avoid swimming for at least 24 hours after it rains and 72 hours after heavy rains.
    • Contact local health officials if you suspect beach water contamination so that others can be protected from exposure.
  • WATERKEEPERS Baja Calfornias and its partners monitor water quality at beaches in this region all year long in the following communities: Tijuana, Loreto, Magdalena Bay, La Paz, Cabo San Lucas, San José del Cabo, Cabo Pulmo, and La Ribera.

    WKBC utilizes a standardized region-wide protocol (see for collecting and analyzing water samples, which is based on the Mexican government standard utilized for recreational beaches (see Comisión Federal para la Protección de Riesgos Sanitarios (COFEPRIS)).

    Se recogen y analizan muestras de agua una vez al mes y los resultados se publican en Swim Guide México dentro de las 6 primeras horas de la obtención de resultados.
    • VERDE: Se marca una playa en color VERDE cuando en los resultados de una muestra se presenta un valor bajo del máximo permisible, 200 NMP (número más probable) de colonias de Enterococos por 100 ml de agua.
    • ROJO: Se marca una playa en color ROJO cuando en los resultados de una muestra se presenta un valor por encima del máximo permisible, 200 NMP (número más probable) de colonias de Enterococos por 100 ml de agua. Esa playa se mantiene marcada en ROJO por 72 horas después del resultado y se convierte a color GRIS si no hay más monitoreo. En caso de presentarse un valor por encima del máximo permisible (200 NMP), el programa local de WKBC notifica a las autoridades correspondientes: Comisión Nacional del Agua (CNA) a través de la Comisión Federal para la Protección de Riesgos Sanitarios (COFEPRIS).
    • GRIS: Se marca una playa en color GRIS cuando no hay resultados actualizados o no hay información disponible.

      Esta información es producto de un programa ciudadano de monitoreo de calidad del agua. La información oficial (cuando sea disponible) se encuentra aquí: de-calidad-de-agua-de-mar.

      Water samples are collected once a month and results are posted on Swim Guide Mexico within 6 hours of obtaining results.
    • GREEN: A beach is marked GREEN when the results are under 200 NMP of Enterococus / 100 ML water
    • RED: A beach is marked RED when the results are above (and including) 200 NMP / 100 ML water. A beach will remain RED for 72 hours and will convert to Grey until follow-up sampling occurs. WKBC will alert the Mexican authorities: Comisión Nacional del Agua (CNA) y COFEPRIS.
    • GREY: A beach is marked GREY when there are no current results or there is no available information.

This information is the product of a citizen-monitoring program by members of WATERKEEPERS Baja Californias and its partner organizations. Official government results (when available) can be found here: de-calidad-de-agua-de-mar.

  • Privately-conducted Water testing at beaches in Mexico - [under research]. Also see (see Comisión Federal para la Protección de Riesgos Sanitarios (COFEPRIS)).

  • Last Best Beach, Playa Blanca,Mexico, Website: [Beach water sanitation testing procuedure is under development]

Sea Water & Fresh Water Contaminant Testing Reference Standards

Here are two key water testing standards appropriate to tests used for swimming beaches where either fresh water or saltwater (marine beaches) are involved:

  • ASTM D5392-93 (2006) Standard Test Method for Isolation and Enumeration of Escherichia Coli in Water by the Two-Step Membrane Filter Procedure, Quoting ASTM:
    • Abstract
    • 1.1 This test method describes a membrane filter (MF) procedure for the detection and enumeration of Escherichia coli, a bacterium found exclusively in the feces of humans and other warm-blooded animals. The presence of these microorganisms in water is an indication of fecal pollution and the possible presence of enteric pathogens. These bacteria are found in water and wastewater in a wide range of densities. The detection limit of this procedure is one colony forming unit (CFU) per volume filtered.
    • 1.2 This test method has been used successfully with temperate fresh and marine ambient waters, and wastewaters. It is the user"s responsibility to ensure the validity of this test method for waters of other types.
    • This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Section 9.
  • ASTM D6503 - 99(2009) Standard Test Method for Enterococci in Water Using Enterolert, Quoting:
    This test provides an easy and reliable method for the detection of enterococci in water within 24 h. For recreational water (fresh and marine) testing is performed to insure areas are safe for swimming. Enterolert also can be used for testing bottled water and drinking water.
    • 1.1 This test method covers a simple procedure for the detection of enterococci in water and wastewater. It is based on IDEXX's patented Defined Substrate Technology (DST). This product, Enterolert, utilizes a nutrient indicator that fluoresces when metabolized. It can detect these bacteria at one colony forming unit (CFU)/100 mL within 24 h. The presence of this microorganism in water is an indication of fecal contamination and the possible presence of enteric pathogens.
    • 1.2 This test method can be used successfully with drinking water, source water, recreational (fresh and marine) water, and bottled water. It is the user's responsibility to ensure the validity of this test method for waters of untested matrices.
    • 1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
    • 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
  • Our complete list of relevant standards for water testing and marine water testing for contaminants are located at REFERENCES at the end of this article. See the "Click to Show or Hide Citations & References" link.

Clean Beach Water Testing Guides, Research, Information Sources for fresh water & salt water beaches

  • "Fecal Bacteria: what are fecal bacteria and why are they important?", U.S. EPA, Water Monitoring and Assessment, - retrieved 8/22/14, original source Excerpts:
    Members of two bacteria groups, coliforms and fecal streptococci, are used as indicators of possible sewage contamination because they are commonly found in human and animal feces. Although they are generally not harmful themselves, they indicate the possible presence of pathogenic (disease-causing) bacteria, viruses, and protozoans that also live in human and animal digestive systems. Therefore, their presence in streams suggests that pathogenic microorganisms might also be present and that swimming and eating shellfish might be a health risk. Since it is difficult, time-consuming, and expensive to test directly for the presence of a large variety of pathogens, water is usually tested for coliforms and fecal streptococci instead.
    The most commonly tested fecal bacteria indicators are total coliforms, fecal coliforms, Escherichia coli, fecal streptococci, and enterococci. All but E. coli are composed of a number of species of bacteria that share common characteristics such as shape, habitat, or behavior; E. coli is a single species in the fecal coliform group.
    EPA recommends E. coli as the best indicator of health risk from water contact in recreational waters; some states have changed their water quality standards and are monitoring accordingly.
    Enterococci are a subgroup within the fecal streptococcus group. Enterococci are distinguished by their ability to survive in salt water, and in this respect they more closely mimic many pathogens than do the other indicators. Enterococci are typically more human-specific than the larger fecal streptococcus group. EPA recommends enterococci as the best indicator of health risk in salt water used for recreation and as a useful indicator in fresh water as well.

  • "What Microorganisims could be in recreational water", U.S. EPA, Region 1: EPA New England, - retrieved 8/22/2014, original source , Excerpts:
    What levels of indicator bacteria are considered acceptable:
    Based on studies conducted in the 1980s, EPA has determined that a geometric mean (a measure of an overall average) in samples from recreational waters of less than 126 E. coli per 100 milliliters (ml) of fresh water or 35 enterococci per 100 ml of salt water is acceptable for protection of swimming. The geometric mean should be calculated from more than five samples within the previous 30 days. If a single sample exceeds 235 E. coli per 100 ml in freshwater and 104 enterococci per 100 ml in salt water, EPA recommends that the beach be closed, or posted, for swimming until levels are lower. (Some states, such as New Hampshire and Vermont, recommend that advisories be posted at more protective levels of indicator bacteria.) Because elevated fecal indicator bacteria are often associated with storm water runoff, some agencies post beaches preemptively if rainfall exceeds a set amount, based on site-specific studies.

    What laboratory methods are recommended for indicator bacteria for recreational waters?
    There are several EPA-approved laboratory methods for measuring the abundance of E. coli or enterococci in recreational waters. These methods generally take 24 or 48 hours before a result is known. EPA recommends that 24 hour methods be used to minimize the time between sample collection and swimmer exposure. EPA approved 24 hour membrane filtration methods are available at the Analytical Methods web site. Alternative popular 24 hour tests, such as the multiple-well fermentation tests for enterococci and E. coli (Enterolert® and Colilert®, respectively) manufactured by IDEXX Laboratories (Westbrook, ME) are also approved for recreational waters.

  • Our complete list of relevant standards for Water Testing Guides, Research, Information about sanitation and other contaminant testing at fresh water sources & beaches & salt water or marine beaches and testing are located at REFERENCES at the end of this article. See the "Click to Show or Hide Citations & References" link.


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