ENVIRONMENTAL SCIENCE 5.3 Before You Drink the Water

Leading Up to Regulations 1900 – 27,000 Americans died of typhoid fever carried in water contaminated w/ human waste 1.1 billion people in the world don’t have access to safe drinking water

Safe Drinking Water Act Safe Drinking Water Act (SDWA) was passed in 1974 EPA regulates certain substances that may be present in the water supply and may threaten human health Maximum Contaminant Level Goals (MCLG) are based on health effects  Known carcinogens and lead = 0 Maximum Contaminant Levels (MCL) are based on MCLGs

MCLGs and MCLs for 80 contaminants found in drinking water  Inorganic contaminants include cadmium, fluoride, lead, mercury, and nitrates  Organic contaminants include pesticides, industrial chemicals, and THMs

Organisms in the Water MCLGs are set to zero for the following contaminants; difficult to identify so required Treatment Techniques are in place of setting MCLs  Legionella pneumophila, a bacteria that causes pneumonia if inhaled  Giardia, a parasitic protozoan  Viruses Effectiveness of filtration is determined by measuring turbidity EPA requires continuous disinfection – addition of disinfectant that remains in the water and is detectable at the consumer’s tap

Coliform bacteria are indicator organisms b/c their presence indicates water quality  Coliform bacteria are found in human and animal intestines MCLG for total Coliforms = zero 1993 – during a period of heavy rainfall and runoff the filtration process in Milwaukee was not effective  Protozoan caused cryptosporidiosis,  >400,000 people became ill; 50 died Most commonly identified cause of water-related disease in U.S. is giardiasis (beaver fever)  Abdominal cramps, nausea, gas, diarrhea

Is Your Water Safe? Potable water – water that is suitable for drinking Action Level for lead is 15 ppb EPA recommends that well owners have their water tested annually for nitrates and Coliform bacteria

Making the Water Safe Chlorination  Certain chemicals in the water affect the chlorine demand  Hydrogen sulfide, iron  EPA recommends contact time of 30 minutes  Easy to measure chlorine residual – the amount of free chlorine remaining in the water Ultraviolet light  Bacteria exposed to UV light are destroyed  More expensive than chlorination  No residual chemicals that can easily be measured to see if water is safe  May not be effective against spores or cysts

Heat  Boil water alert is issued when microorganisms are in the water or there is a break or repair of a water main Filtration  Activated carbon filters are designed to remove organic chemicals that cause color, taste, or odor  Adsorption – organic chemicals stick (adhere) to the surface of the carbon particles  Sediment filters do not remove chemicals dissolved in water

Water Conditioners (Softeners) Ion-exchange system (water softener) – removes calcium and magnesium and may remove iron Mineral deposits cause scale build-up in water heaters, pipes, etc. Water softener is filled w/ resin; Ca and Mg ions are exchanged for Na ions Ion-exchange system similar to a water softener can remove nitrates

In an Emergency Bring water to rolling boil for 1 min Add 10 drops of bleach per quart (30 min contact time) Add 5 drops of tincture of iodine per quart (30 min contact time) Add 1 iodine tablet per quart