Coliform Bacteria Testing of Lake Chapala Shores

 

Dr. Todd D. Stong (USA)

Engineer María Aparicio Cid

María Andrea Leal Pérez, TPCCA

 Mtra. Lucia Elena Tolentino

Chemist Norma Huerta Garcia, QSB

Sergio Ortega Garcia, M.S.

 

March 2008

 

Purpose: Given much local conjecture, for many years, that the lake is too polluted to permit recreational uses, the focus of this testing effort is to offer a preliminary evaluation of the biological safety of the water for full-body immersion recreation.

 

Procedure: The program has been under the direction of Dr. Todd D. Stong, Licensed Professional Engineer (USA) who serves as a volunteer advisor for infrastructure to lakeside governments. Water samples were collected at points beyond the lake edge where the water depth was one meter. The water samples were taken at a point 30 cm beneath the water’s surface. Testing of water samples was accomplished by Andrea Leal Perez, TPCCA, Chief of the Center for Technical Studies of Continental Waters (CETAC) laboratory in Jocotepec, in conjunction with Engineer María Aparicio Cid, Director of the Jocotepec wastewater treatment plant laboratory, as per Mexican standard NMX-AA-42-1987.

 

Criteria: Evaluation of water quality was as per Mexican standard NOM-003-ECOL-1997, which specifies a maximum count of 240 fecal coliform bacteria units/100ml water samples. This is for full-body immersion water recreation. The standard is set at 1000 if the recreation is via indirect contact (as with water skiing, boating or wading). The EPA-USA guide for fecal coliform counts is 200. For total coliform it is 1000, and for E. coli it is 126. The selection by international groups of a bacteria criterion for beaches is because, in contrast to swimming pools, there is no chlorination.

 

Testing Locations: As of 26 Feb. 2008, 19 tests have been conducted at 16 sites along the north and west shores of Lake Chapala. The locations include next to the Guadalajara water pumping station at San Nicolás de Ibarra, Chapala, Ajijíc, Piedra Barrenada, San Juan Cosalá, El Chante, Jocotepec and San Pedro Tesistán.

 

Summary Test Results: As of 26 Feb. 20008, the water at 15 of the 16 sites, 94%, contained less fecal coliform bacteria than the Mexican limit of 240 units/100ml water sample. The location that exceeded the limit was San Pedro Tesistán (290).

 

Test locations that had fecal coliform counts that were less than 120 (50% of the 240 limit 240) included: (1) near the Guadalajara water pumping station, (2) Chapala’s Cristiania Park, (3) the malecón at Chapala, (4) a site at the foot of Calle Donato Guerra in Ajijíc, (5) in front of the park west of the Ajijíc pier, (6) Piedra Barrenada, (7) the malecón at San Juan Cosalá, (8) El Chante and (9) the malecón at Jocotepec. Thus, each of these sites very well meets the criteria for a public swimming location.

 

Water Safety Testing: How pure must water be? Depending on the intended use of water, there are varying criteria for acceptability. While the focus of this study is for full-body immersion, recreational water safety, note below how the fecal coliform criteria (USA) vary depending on the intended use of the water--from the most demanding purity to lower levels.

 

Intended use for water	Fecal Coliform Criterion
Municipal drinking water	0 per 100 ml water sample
Bottled water	Lower standards (1-3 /100ml) than for municipal drinking water supply
Recreational use, full contact (e.g., swimming)	200
Recreational use, low contact (e.g., wading, water skiing)	1000
Raising of fish (aquaculture)	1000
Restricted irrigation (e.g., for crops that may be consumed by people)	1000
Unrestricted irrigation (e.g., for trees, animal feed crops)	2000
Public water supply to be processed via a conventional treatment plant	2000
For return to a river after being processed at a wastewater treatment plant	200 Dissolved solids – 30 PPM pH – 6.0 to 9.0 If properly chlorinated, nitrogen and phosphorous are more of a challenge.

 

For reference, note that human solid waste typically has 50,000,000 coliform bacteria per gram, with perhaps 10,000,000 of that being fecal coliform. Thus, a 99% reduction of these bacteria in human waste would leave perhaps 500,000 total coliform bacteria in each gram. This is the key reason for much hand washing! The good news is that the very high dissolved oxygen content of the lake water, due to the wave action on shallow water, accelerates the digestion of organics in the water. In turn, the very high pH of the water, more basic than acid, makes it difficult for most chemicals to react and thus become available for consumption.

 

While water of drinking quality is routinely used in the USA to wash autos and to water the lawn, that luxury is not possible in most nations. Water usage in the USA is about 150 gal/person/day versus perhaps 20-30 gal./person/day for rural towns in Mexico. In the USA, the top 100 beaches for recreation (swimming) exceed the recreational full-body immersion criteria 25% of the time. For beaches on the Great Lakes in the USA, 10% of swimmers report gastroenteritis (diarrhea). Often, bacteria limits at beaches are exceeded because several days are required for a coliform test. In the USA there are over 26,000 beach-closed days due to high bacteria. Most areas tested along the north shore of Lake Chapala reflect a fecal coliform count of less than 50, which is quite a bit less than the Mexican 240 or the USA 200 limit. Further, the fecal coliform limits of 240 or 200 colonies per 100 ml water sample is 50% of the 400 colonies/100 ml level where studies show the onset of sickness is believed to occur while swimming.

 

Most of us have heard people say the lake is badly contaminated. The fact is, however, that these comments have been made without any supporting data. The levels of pesticides, herbicides, and heavy metals in the lake, while of concern because of bio-accumulation in some fish, are at such low levels that they do not negate the use of lake water for processing into drinking water for Guadalajara, nor do they present any hazard for recreational use of the water. Indeed, much more testing of lake water (quite expensive) is needed for these chemicals which are often measured in parts per billion. The real concern is for people who eat the fish. In general, if the fish come from Mezcala and westward, consumption, even daily, poses a very low hazard, if you do not eat the gills, heart, liver and kidneys.

 

Other Beach Use Considerations: Of course, where a person chooses to swim is based on more than biological and chemical tests. People look for: clean areas free of trash, signs that declare the water is biologically safe, lifeguards, buoys to denote water depth, availability of life vests or belts, beach and lake bottom free of hazards (glass, barbed wire, big rocks, pipes, etc.), a sandy lake bottom, and water clarity. Hopefully, as the government and private businesses act to develop inviting swimming areas along the lake, they will address these possible user concerns. It is expected that it will be the government which conducts the biological water testing needed to declare areas safe for swimming. As of now, look first to the beach facilities being constructed at Chapala, San Juan Cosalá, and Jocotepec. It is expected that soon an effort will begin to develop a beach facility at Ajijíc.

 

Recommended Beach Areas: While each area noted below has lake water that meets biological quality for swimming, most of these areas need of some further work to make them aesthetically appealing, easy to wade into with a good bottom of firm silt or sand, and with some area prepared for children where the water is shallower. In time, one might consider adding life guards, rest room facilities, a shower stand, beach sand cleaning service, and monthly testing of the water quality.

 

Chapala Malecón - This lakeside area is becoming quite nice due to recent government efforts to rebuild the malecón, to add sand and to clean the beach. Need to define best areas with sandy bottom via floats on a rope line so as to keep people out of deep mud areas. May wish to move the pelican eating stands further out since this offensive cut up fish debris is washing onto the shore. This beach is the closest at this time (Feb. 08) to making it ready for swimming. 

 

Ajijíc - A good beach could easily be created at the end of Calle Donato Guerra where the lake bottom is quite nice. Need to remove some lake edge vegetation and debris and install floats on a rope line to define water depth of 50 cm to guide children's use.  This may be the best and easiest beach area to prepare at this time for the public along the north shore of the lake.

 

Ajijíc - A beach could be created in front of the park, to the west of the pier, if the bottom was cleared of rocks and a sloped sand area added so there would be some area with water depth of 50cm and less for children to enter.

 

San Juan Cosala Malecón - Under construction. Lake bottom is already pretty good. Need to remove rocks from some area to make wading easier. Need to add sloped sand area to permit children's use.

 

El Chante - There is no facility at this time ready for recreation. The best site for development may be that where the public football field exists. There is potential for easy entry into slowly-deepening water with a good lake bed bottom. Presently, rocks need to be removed from that area which might be planned for entry and wading.

 

Jocotepec Malecón - Phase I malecón is quite attractive and ready for lakeside viewing. An excellent parking and picnic area is also nearby. This may presently be the best overall area from which to enjoy the lake, without entering the water. It is hoped that the Phase II effort to create grassy recreational areas will also include a sandy beach. As of now (Feb. 08), it is not possible to wade into the water due to a muddy and/or rocky bottom and depths over 2 meters at the edge of the current construction. 

 

Dr. Todd D. Stong

Ingeniero Licenciado y Profesional,

Consejero Voluntario Sobre la Infraestructura

Email: tdstong@juno.com

 

 

Test Sites/Results - Sample Collection

 

Test Site	Date of Test	Fecal Coliform Bacteria NMP/100ml	Location of test and notes
1	29/1/08	<30	Piedra Barrenada, 80 meters from the Canoe Restaurant
2	29/1/08	<30	New malecón under construction in San Juan Cosalá, sandy floor
3	29/1/08	73	East of treatment plant at San Juan Cosalá, clearer water
4	29/1/08	36	West of treatment plant at San Juan Cosalá, clearer water
5	29/1/08	36	East of treatment plant at El Chante; muddy, swampy football field
6	29/1/08	91	West 200 meters from treatment plant at El Chante, relatively clear water, a great recreational site next to an existing football field
7	29/1/08	<30	East 100 meters from east end of the Jocotepec malecón, muddy, a place for tied-up boats
8	29/1/08	<30	Directly in front of Jocotepec malecón; water depth near to 2 meters of edge of recently placed rocks
8	12/2/08	230	Repeat of site #8; at middle of malecón, more algae in water than at last test, construction in water disturbing mud
8	21/2/08	36	Repeat of site #8, center of malecón. Much algae in water
9	29/1/08	<30	700 meters south of the Jocotepec treatment plant; clay/sand floor, marshy land near
10	29/1/08	290	San Pedro Tesistán, end of a recent rock fill jetty/pier
14	12/2/08	36	San Nicolás, 500m east of pump station for water line to Guadalajara; muddy bottom, site for fishermen, much lirio and algae in adjacent inlet
15	12/2/08	230	Chapala, 300m east of treatment plant, 10m west of outlet of San Marcos arroyo, muddy bottom, shallow water, much algae, due south of the former railroad station now a museum
16	12/2/08	73	Chapala, 150m west of treatment plant, 50m west of edge of Cristiania Park, over stone wall, moderate mud, shallow
17	12/2/08	91	Chapala, center of malecón, deep muddy bottom after 10 meters into water at 1m depth, many pelicans, algae. Repeat test to confirm data set from earlier test data.
17	21/2/08	91
18	12/2/08	<30	Ajijíc, at end of Calle Donato Guerra, in front of Nueva Posada, very good sandy bottom
19	12/2/08	<30	Ajijíc, middle of park to the west of the pier, hard bottom with some rock