Safe Drinking Water

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The majority of people in the US get their water from public water systems that have to meet state or federal requirements for safety Almost 20% of the world’s population does not have regular access to clean drinking water

Common water-borne diseases Cholera Transmitted by Vibrio cholera and causes gastrointestinal issues Giardiasis Transmitted by Giardia lamblia parasite and causes GI issues Legionellosis Caused by Legionella pneumophila bacteria and leads to flu like symptoms

Cholera Giardia lamblia Legionellosis

Organisms in the Water Maximum Contaminant Level Goals (MCLG) are in place to prevent water borne illnesses Zero tolerance for Giardia, Legionella and viruses Indicator organisms like fecal coliform bacteria are used for water quality testing

Making Water Safe If surface water or well water is contaminated there are a few methods that can clean it Chlorination- chlorine can disinfect (kill) most microbes UV Light- kills bacteria; more expensive than chlorination Heat- water heated to a rolling boil for at least one minute can kill bacteria and protozoan cysts Filtration- activated carbon filters remove organic chemicals from water

The Treatment Process

Waste Water Treatment Most of the wastewater from residential areas is biodegradable Industrial water and storm runoffs contain toxic chemicals that can interfere with treatments

Treatment Process 1. Screening: Wastewater entering the treatment plant includes items like wood, rocks, trash and even dead animals. The water is run through a screen to catch these solids Most of these materials are sent to a landfill.

2. Pumping: The wastewater system relies on the force of gravity to move sewage from your home to the treatment plant. (So wastewater-treatment plants are located on low ground, often near a river into which treated water can be released). If the plant is built above the ground level, the wastewater has to be pumped up to the aeration tanks

3. Aerating: The wastewater is sent to a tank where it is exposed to oxygen to allow decomposition to begin

4. Removing sludge Wastewater then enters the sedimentation tanks Large particles (AKA the sludge) settles out of the wastewater and is pumped out of the tanks Some of the water is removed in a step called thickening and then the sludge is processed in large tanks called digesters.

Lighter materials float to the surface 5. Removing scum: Lighter materials float to the surface This 'scum' includes grease, oils, plastics, and soap. Slow-moving rakes skim the scum off the surface of the wastewater. Scum is thickened and pumped to the digesters along with the sludge.

6. Killing bacteria: Wastewater flows into a 'chlorine contact' tank, where the chemical chlorine is added to kill bacteria, The chlorine is mostly eliminated as the bacteria are destroyed, but sometimes it must be neutralized by adding other chemicals The treated water (called effluent) is then discharged to a local river, wetland or the ocean

The Sludge Another part of treating wastewater is dealing with the solid-waste material These solids are kept for 20 to 30 days in large, heated and enclosed tanks called 'digesters.' Here, bacteria break down (digest) the material, reducing its volume, odors, and getting rid of organisms that can cause disease The finished product is mainly sent to landfills, but sometimes can be used as fertilizer.

Wastewater Treatment Video

Summarizing Questions:10 points Why is chlorine added to water during the treatment process? Expand: Why is there more chlorination and filtration of water during summer months?