Zach Estella lab technician at Ajusco Labs
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Location Mexico City, Mexico
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The following is a list of parameters for testing rainwater quality at The Laboratory of Community Alternative Technologies at Ajusco in conjunction with Isla Urbana. Both groups are non profits located in Mexico City. Isla Urbana is a group providing rainwater catchment systems around Mexico City and other areas of Mexico, Ajusco Labs is a laboratory testing center for appropriate technology projects and outcomes. Ajusco Labs will be testing rainwater quality outcomes from Isla Urbanas systems set up around Mexico City. This is one part in a series of rainwater testing at Isla Urbana and Ajusco Labs. Click here to connect to the main page on Rainwater quality testing.

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Expected Parameter Concentrations for Rain Water[edit | edit source]

The World Health Organizations suggest studying the amount of coliforms as well as the lead, zinc, and other heavy metals in rainwater. Also WHO suggests checking the physical quality of rainwater including the turbidity, colour and smell. In cases where new concrete, ferrocement or masonry storage tanks have been put in place levels of pH should also be monitored.[1]

Differential susceptibility to different toxins based on Location[edit | edit source]

  • Industrial areas have higher concentrations of lead, turbidity, suspended solids, and zinc.
  • Urban areas have detectable levels of lead, but at lower concentrations.
  • Rural areas have higher concentrations of nitrate and a slightly higher pH value.[2]

Differential susceptibility to different toxins based on Roofing Material[edit | edit source]

  • Galvanized iron roofs have higher zinc concentrations
  • Concrete roofs have higher pH value, turbidity, and conductivity[3] The conductivity of water is affected by inorganic dissolved solids like sulfate, nitrate, chloride,and phosphate anions (ions that carry a negative charge) or calcium, sodium, iron,magnesium, and aluminum cations (ions that carry a positive charge).[4]

Parameters of Testing Rainwater Quality

Parameters locations with increased concentrations system material that can increase concentration concentration upper limit in drinking water
Coliforms all all 10 -60 CFU per 100ml / none in a 100 ml of water
Lead industrial & urban lead plumbing,flashing, and nails 0.015 mg/L
Zinc industrial galvanized iron roof 5mg/L
pH rural concrete roofs close to 7
Nitrate rural 10 mg/L
Nitrite 1 mg/L
Total Petroleum Hydrocarbons 300-900 micrograms/L
Phthalate esters 0.006 mg/L
Sulphates 250 mg/L
Total Chlorine < 1.0 mg/L
Hardness (mg/l of CaCO3) 0-75 soft
75- 100 moderately hard
150 -300 hard
300 and up extremely hard


Further Indicators of overall Water Quality

Indicator Standard Concentrations for different water bodies
Chemical Oxygen Demand, COD max 250mg/L for industrial discharge into surface waters*****
Total Organic Carbons, TOC .05mg/L for purified water for drinking****
Dissolved Organic Carbon, DOC 3.6 mg/L in clouds **
Total Particulate Carbon, TPC 1.05 mg/L in clouds **
Total Suspended Solids, TSS max at 70 mg/L for rivers, streams, and lakes
Total Dissolved Solids max at 500 mg/L for drinking
Conductivity 0.5 to 3 µmhos/cm *** in distilled water
50 to 1500 µmhos/cm in rivers

* The U.S. Environmental Protection Agency (EPA) does not have a standard for COD, TOC, DOC, TPC, TSS, or Conductivity in drinking water. This might be because none presents a health problem alone, but all can serve as an indication of the level of other organic or inorganic materials in the water.


*** µmhos/cm = micromhos per centimeter[7]

**** No limit on TOC is set by EPA standards for drinking water, however the USP (United States Pharmacopeia) does set a limit at.05 mg/L. The USP is a private, not-for-profit organization that sets standards for drugs, devices and diagnostics. Standards listed in the "monograph" section of the USP's published US Pharmacopeia are legally enforceable by the Food and Drug Administration, FDA.[8]


Description of Parameter Toxins[edit | edit source]

Coliforms[edit | edit source]

In studies conducted by the World Health Organization microbial contamination in collected rainwater, as indicated by E. coli, is quite common, especially in those samples collected just after rainfall. Also pathogens including:Cryptosporidium, Giardia, Campylobacter, Vibrio,Salmonella, Shigella and Pseudomonas have also been found in samples of rainwater. Higher microbial concentrations are usually found within the first flush and decreases over the time period of the rain.[10][11]

Lead[edit | edit source]

A study in Australia found that 10-20% of tanks at any one time have lead above the Australian Drinking Water Guidelines of.01mg/L. Often this form of contamination enters through corrosion of plumbing, rooftop sources such as lead flashing and leaded roofing nails, as well as occurring more often in urban or industrial areas from atmospheric fallout.[12] For children, high concentrations of lead can result in delayed physical and mental development, slight deficits in attention span and learning abilities. For adults, high concentrations of lead can result in high blood pressure or kidney problems.[13] The EPA recommended limit for lead is 0.015 mg/L or 15 ppb for drinking water.[14]

Zinc[edit | edit source]

Zinc has been found in rainwater in concentrations of 9.8 mg/L, double that of recommended levels for drinking water, in studies in France. These elevated levels were related to zinc gutters and roofing as well as galvanized iron roofing.[15] This corrosion of zinc is accelerated by the presence of atmospheric sulphur dioxide, SO2, and sulphur gas emissions which increase in large cities. Increased levels of zinc above 500mg/L have been associated with vomiting, fever, nausea, stomach cramps, and diarrhea, and for those consuming 150–405 mg/day for zinc therapy a resulting deficiency in copper has been found.[16] EPA recommended limit is 5 mg/L for drinking water.

pH[edit | edit source]

Rainwater is slightly acidic and can dissolve heavy metals and other impurities within your catchment system. There has been high levels of lead and zinc reported in catchment systems and this may either be due to the leaching from metallic roofs and tanks or due to atmospheric pollutants.[17] close to 7 as possible.

DO Dissolved Oxygen[edit | edit source]

Low dissolved oxygen levels usually indicate serious pollution for aquatic plants and organisms like fish, however if using water for domestic purposes too much dissolved oxygen is not a health hazard, but has been found to be corrosive to pipes.

Nitrates[edit | edit source]

Common sources of increased nitrate levels come from runoff fertilizer use and leaching from septic tanks and sewage.[18] Animals and humans cannot use inorganic forms of nitrogen and if nitrate does exceed 10 milligrams per liter in drinking water, it can cause interfere with blood-oxygen levels and lead to methemoglobinemia (or blue baby syndrome) in infants and gastric cancer.[19][20] The EPA recommended limit for nitrates is 10 mg/L and for nitrites is 1 mg/L.[21]

Sulfates[edit | edit source]

Sulfates have been found in rainwater at concentrations between 1.0-3.8 mg/L in Canada and at a mean value of 6mg/L in Europe. These sulfate levels have been found to correlate with the emissions of sulfur dioxide produced from human sources. Elevated levels of sulfates are associated with dehydration and at concentrations above 500 mg/L it is associated with purging, or execution of the bowels, in adult men. The total intake of sulfates from drinking water, air, and food on average come to 500mg/day, with food as the major source, however this may be exceeded by water in areas with high levels of sulfate in the drinking water.[22] The EPA recommended limit on sulfate is 250 mg/L for drinking water.[23]

Phthalate esters[edit | edit source]

Phthalate esters are substances added to plastics to increase their flexibility, transparency, durability, and longevity and used in many PVC's. In the US concentrations of more than 0.1 percent of DEHP, DBP, or BBP are not allowed in children's toys, since these toys may be taken into the mouth.[24] Phthalates have been found to exceed recommended levels in rainwater catchments with mortar roofs, cement courtyards, and compacted soil surfaces.[25] Since the phthalate plasticizers are not chemically bound to PVC, it is easy for them to leach into food or water or evaporate into the atmosphere to be distributed far from the source of contamination. Adverse health effects found from phtalates include increased wheezing from people with asthma, increased incidence of allergies, asthma, and autism, problems with the liver, increased incidence of cancer, as well as changing hormone levels and birth defects.[26][27][28][29] The maximum contaminant level set by the EPA on di(2-ethylhexyl) phthalates is 0.006 mg/L.[30]

Chlorine[edit | edit source]

Chlorine has a denaturing effect on plant and animal tissues. Chlorine in the free available form readily reacts with nitrogenous organic materials to form chloramines, which are toxic to fish.[31] A minimum free chlorine residual of 0.2 mg/L should be sufficient to maintain disinfection, while a chlorine concentration above 1.0 mg/L is to high and can have adverse health effects.

Hardness[edit | edit source]

The U.S. Environmental Protection Agency, EPA, does not have a legal limit or standard for water hardness. This is primarily because the contributing factors to hardness (including calcium and magnesium ions) are not toxic to human health.[32] Hardness is commonly reported in the concentration calcium carbonate (CaCO3). However hardness can cause scale formation in boilers, water heaters, and feed lines, has a low sudsing characteristic, and can aggravate dry skin conditions.[33]

System Designs for Reducing Toxicity[edit | edit source]

Roofing Material[edit | edit source]

  • Concrete roofs have the most reduced levels of those contaminants listed above in Table....
  • Aluminum and stainless steel gutters and roofing have shown lower heavy metal emission levels in rainwater in comparison to their zinc and copper counterparts.[34]

First Flush[edit | edit source]

Effects of First Flush[edit | edit source]

  • For the entire roof surface for each 1mm depth of rainwater flushed out, the contaminant load will halve.
  • Contaminant reduction is less during strong storms[35]

Designs[edit | edit source]

Go to... for Isla Urbana's two different first flush designs

Filters[edit | edit source]

Go to.. for Isla Urbana's different filter applications.

Heating Water before use[edit | edit source]

  • Hot water systems purify the water by removing coliforms.
  • Rainwater used in hot water systems set at >52°C has been found to be compliant with Australia drinking water standards.[36]
  • Heating elements can include passive solar heating systems, solar water heaters, biogas heaters, or [electrical water heaters]] for purifying water

References[edit | edit source]

  1. World Health Organization. Water Sanitation and Hygiene: 6.11 Rainwater harvesting.
  2. Thomas, P R and Greene, G R. Rainwater quality from different roof catchments. Water Science & Technology. Vol. 28, no. 3/5, pp. 291-299. 1993
  3. Thomas, P R and Greene, G R. Rainwater quality from different roof catchments. Water Science & Technology. Vol. 28, no. 3/5, pp. 291-299. 1993
  4. US Environmental Protection Agency. 5.9 Conductivity: What is conductivity and why is it important?
  5. U.S. Environmental Protection Agency.Basic Information about Di(2-ethylhexyl) phthalate in Drinking Water.
  6. Hadi DA, Crossley A, Cape JN. Particulate and dissolved organic carbon in cloud water in southern Scotland.Environ Pollut. 1995;88(3):299-306.
  7. U.S. Environmental Protection Agency. Monitoring & Assessment: 5.9 Conductivity.
  9. B.V. Babu1, H.T. Rana, V. Rama Krishna, and Mahesh Sharma C.O.D REDUCTION OF REACTIVE DYEING EFFLUENT. Department of Chemical Engineering, Birla Institute of Technology & Science, India.
  10. World Health Organization. Water Sanitation and Hygiene: 6.11 Rainwater harvesting.
  11. International Water and Sanitation Centre. Effects of first flush on rainwater quality. 19 June 2006.
  12. Chapman, H., Huston, R., Gardner, T., Chan, A. & Shaw, G.: Chemical water quality and health risk assessment of urban rainwater tanks. In the 7th International conference on urban modelling and the 4th International conference on water sensitive urban design (eds. Deletic, A. & Fletcher, T.) (Grand Hyatt, Melbourne, 2006).
  13. US Environmental Protection Agency. Lead in Drinking Water.
  14. US Environmental Protection Agency. Lead and Copper Rule.
  15. M.C. Gromaire, G. Chebbo and A. Constant. Impact of zinc roofing on urban runoff pollutant loads: the case of Paris. Water Science & Technology Vol 45 No 7 pp 113–122.
  16. UN World Health Organization. Zinc in Drinking-water: Background document for development of WHO Guidelines for Drinking-water Quality. 1996.
  17. World Health Organization. Water Sanitation and Hygiene: 6.11 Rainwater harvesting.
  18. US Environmental Protection Agency. Drinking Water Contaminants.
  19. U.S. Geological Survey. USGS Water Quality Information.
  20. C Kameswara Rao. Toxicity of Nitrates and Nitrites in Plants. Foundation for Biotechnology Awareness and Education. Bangalore, India. July, 2007.
  21. Water Test, Inc. Louisiana.
  22. World Health Organization. Sulfate in Drinking-water: Background document for development of WHO Guidelines for Drinking-water Quality.
  23. Water Test, Inc. Louisiana.
  24. US Consumer Product Safety Commission. Section 108: Products Containing Certain Phthalates.
  25. Kun Zhu, Linus Zhang, William Hart, Mancang Liu, and Hui Chen. Quality issues in harvested rainwater in arid and semi-arid Loess Plateau of northern China. Journal of Arid Environments. Volume 57, Issue 4, June 2004, Pages 487-505.
  26. Environmental Protection Agency, EPA. Basic Information about Di(2-ethylhexyl) phthalate in Drinking Water.
  27. Kolarik B, Bornehag C, Naydenov K, Sundell J, Stavova P, Nielsen O.The concentration of phthalates in settled dust in Bulgarian homes in relation to building characteristic and cleaning habits in the family. Atmospheric Environment. December 2008. Vol. 42 (37): 8553–9.
  28. Cone, Marla. Scientists Find 'Baffling' Link between Autism and Vinyl Flooring: Swedish children who live in homes with vinyl floors are more likely to have autism, according to a new study, but what's behind the link is unclear. Scientific American Environmental Health News. March 31, 2009.
  29. U.S. Center for Disease Control and Prevention. Third National Report on Human Exposure to Environmental Chemicals, July 2005.
  30. U.S. Environmental Protection Agency.Basic Information about Di(2-ethylhexyl) phthalate in Drinking Water.
  31. U.S. EPA. Quality Criteria for Water. July, 1976.
  32. U.S. Geological Survey. USGS Water Quality Information.
  33. Water Test, Inc. Louisiana.
  34. P. Robert-Sainte, M. C. Gromaire, B. de Gouvello, M. Saad† and G. Chebbo. Annual Metallic Flows in Roof Runoff from Different Materials: Test-Bed Scale in Paris Conurbation. Environmental Science Technology, 2009, 43 (15), pp 5612–5618.
  35. International Water and Sanitation Centre. Effects of first flush on rainwater quality. 19 June 2006.
  36. International Water and Sanitation Centre. Effects of first flush on rainwater quality. 19 June 2006.
FA info icon.svg Angle down icon.svg Page data
Part of Rainwater quality testing with Isla Urbana
Keywords rainwater, water quality, project testing
SDG SDG06 Clean water and sanitation
Authors Carrie Schaden
License CC-BY-SA-3.0
Language English (en)
Related 0 subpages, 10 pages link here
Impact 1,779 page views
Created October 17, 2010 by Carrie Schaden
Modified June 1, 2024 by Kathy Nativi
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