Environmental Health Laboratory - Volusia County Health Department, Florida

Why do we test drinking water?

A host of human diseases, particularly those of the gastro-intestinal tract are spread through fecally contaminated water. The isolation and identification of specific disease-producing bacteria, parasites and viruses that may exist in water is time consuming and possibly hazardous. Therefore, appropriate indicator organisms are used to detect the presence of these enteric pathogens (disease causing bacteria). These indicators belong to the coliform group of bacteria. They were selected because they are usually present in water containing pathogenic organisms; survive longer in the aquatic environment; are relatively harmless; and are easily grown, isolated and identified.

Current regulations in the U.S. as well as most other countries require that potable (drinking) water be tested for the presence of total coliform organisms.

The term "total coliform organisms" refers to a group of gram-negative aerobic to facultative anaerobic, non-spore forming, rod shaped bacteria which ferment lactose at 35^o C in 24-48 hours. Or, as applied to the membrane filtration technique, the term applies to a group of gram-negative, non spore-forming, rod shaped bacteria that develop a red colony with a green metallic sheen w/i 24 hours at 35^o C on endo-type medium containing lactose. These organisms are widely distributed in nature and many are native to the gut of warm blooded animals, including man. They are considered to be non-pathogenic under normal conditions and are able to exist as free living saprophytes (an organism which lives on dead organic material) as well as in the intestinal tract.

The absence of total coliforms in a water supply is used as a basis for considering the water safe to drink.

Call your local Environmental Health Office to arrange for sample collection and/or analysis.

The surface water system in Volusia County host a wide variety of both recreational and commercial events. This precisous commodity is subjected to many influencing factors which potentially carry negative results on the health of our aquatic systems such as on lakes, rivers, and lagoons. With incroaching urban development and increased number of marinas and boats, the health of our surface water must be monitored to ensure our environments survival. As a result of this concern, we monitor sixteen parameters to follow and pinpoint pollution sources.

You were looking at a petri dish showing the "golden-green sheen" colonies typical of total coliform colonies. These colonies were grown on m-endo agar containing lactose, protein digest, vitamins, selective chemicals and Schiff’s Reagent. Coliform bacteria produce an acid aldehyde (among other by products) that combines with the Schiff’s Reagent to form an irridescent green coating over the growing colonies thus giving the "golden-green sheen " appearance.

A 100 ml sample of water is drawn through a membrane filter (45m pore size) with the help of a vacuum pump. The plate is placed in an incubator inverted in a moist container for 24 hours at 35^o C.

The blue colonies you were looking at were fecal coliform bacteria. They were grown on M-FC agar which contains lactose, protein digest, vitamins, bile salts, selective chemicals, and an aniline blue dye.

A 100-ml of a water sample is drawn through a membrane filter (45m pore size) through the use of a vacuum pump. The filter is placed on a petri dish containing the M-FC agar and incubated for 24 hours at 44.50^o C. This elevated temperature heat shocks non-fecal bacteria and suppresses their growth. As the fecal coliform colonies grow they produce an acid (through fermenting lactose) which reacts with the aniline dye in the agar thus giving the colonies their blue color.

The red colonies you were looking at on this plate were enterococcus bacteria. They were cultured on mE agar for 48 hours @ 35^oC.

Enterococcus bacteria are a valuable indicator for determining the extent of fecal contamination of recreational surface waters. Studies have shown that swimming associated gastroenteritis is related directly to the quality of the bathing water and that enterococci are the most efficient bacterial indicator of water quality. Water quality guidelines have been proposed based on enterococcal density.

Recreational fresh waters should have less than 33 enterococci/100 ml and marine waters should have less than 35 enterococci/100 ml.

The recommended state standard for chlorides for public water is 250 parts per million (PPM). Water with readings greater than 250 PPM is not recommended for drinking. Most waters contain some chloride in solution. The amount present can be caused by leaching of marine sedimentary deposits, pollution from sea water, brine or industrial and domestic waste. Chloride concentrations in excess of 250 PPM usually produce a noticeable taste in drinking water. Chlorides can be removed by distillation, demineralization or reverse osmosis.

The recommended state standard for public water for iron is 0.3 PPM. Iron is an aesthetic problem only. Iron may impart reddish-brown staining to laundry and plumbing fixtures. It can impart a bitter or astringent taste to water and can affect the taste of beverages at concentrations in excess of 1.0 PPM. The amount of iron causing objectionable taste or staining is only a small fraction of the amount consumed in the daily diet. Iron can be removed by water filtration treatment processes such as ion exchange or oxidation followed by filtering. Iron is naturally occurring but can also be caused by corrosion of iron or steel piping or iron-producing bacteria. Concentrations of 1-5 PPM in groundwater is common.

The Environmental Protection Agency has established a Maximum Contaminant Level Goal (MCLG) of zero for lead; and an action level of 15 ppb.

Lead is a common metal found throughout the environment in lead-based paints, air, soil, household dust, food, certain types of pottery, porcelain and pewter, and water.

Lead can pose a significant risk to your health if too much of it enters your body.

Lead builds up in the body over many years and can cause damage to the brain, red blood cells and kidneys. The greatest risk is to young children and pregnant women. Lead in drinking water, although rarely the sole cause of lead poisoning, can significantly increase a person’s total exposure, particularly infants who drink baby formulas and concentrated fruit juices that are mixed with water. Lead is found in drinking water primarily as a result of the corrosion, or wearing away, of materials containing lead in the water distribution system and household plumbing.

The maximum contaminant level (MCL) for nitrate for public water is 10.0 parts per million (PPM). Serious and occasionally fatal poisonings in infants have occurred following ingestion of well waters with nitrate nitrogen concentrations greater than 10.0 PPM. The major health concern involves infants 6 months or younger since their digestive system is too immature to break down nitrates. Methemoglobinemia or "blue baby syndrome" results when high nitrate levels are present. Methemoglobinemia causes the hemoglobin iron in the blood to not transport oxygen throughout the body thus creating a "blue" skin color. Constant exposure to nitrates (even at marginal levels) results in an oxygen shortage which could cause brain damage. Since a high level of nitrates in water does not impart taste, color or odor, the only way to determine it’s level is to have the water analyzed. The average citizen takes in 75 to 100 mg of nitrates each day, mostly from vegetables such as beets, lettuce and spinach. Nitrate is an essential nutrient and hence, a major component of animal wastes and decomposing organic matter. Chemical fertilizers are another source of nitrogen. Nitrates can build up in the soil and leach into groundwater.

Phosphorus (P) is an essential nutrient for all life forms. It does not exist in a gaseous state and natural inorganic phosphorus deposits occur primarily as phosphate in the mineral apatite. Phosphate is usually not readily available for uptake in soils. Most of the phosphorus in soils is absorbed to soil particles or incorporated into organic matter (Smith, 1990; Craig et al., 1998; Holtan et al., 1998). In freshwater systems phosphorus (as orthophosphate) is generally the limiting nutrient. Thus, if sufficient phosphorus is available, elevated concentrations of nitrates will lead to algal blooms and perhaps fish kills. Long-term eutrophication will usually be prevented if total phosphorus levels and orthophosphate levels are below 0.5 mg/l and 0.05 mg/l, respectively (Dunne and Leopold, 1978). Nitrogen is generally the primary limiting nutrient in the seaward portions of estuarine systems (Paerl, 1993). Systems may be phosphorus limited, however, or become so when nitrogen concentrations are high and N:P<16:1 (Jaworski, 1981). The State of Florida regulation of phosphorus in surface waters is based on whether nutrient enchrichment results in violations of other standards in any of the surface water classes (I-V), and whether nutrient concentrations result in "an imbalance in natural populations of aquatic flora or fauna" for classes I-III (62-302.530, F.A.C., Criteria for Surface Water Quality Classification.

Clarity of water is important in producing products destined for human consumption and in many manufacturing operations. The major concern with turbid water is the fact that it greatly decreases the effectiveness of chlorination and disenfection. The clarity of a natural body of water is an important determinant of its condition and productivity. Turbidity in water is caused by suspended and colloidal matter such as clay, silt, finely divided organic and inorganic matter, and plankton and other microscopic organisms. Turbidity is an expression of the optical property that causes light to be scattered and absorbed rather than transmitted with no change in direction or flux level through the sample. The MCL (maximum contaminant level) for turbidity for public potable water is 1 NTU (nephelometers turbidity units).

**Information supplied by the 19th Edition 1995 Standard Methods for the Examination of Water and Wastewater.