water treatment processes. why do we need to treat our drinking water? industrial runoff ...

Water Treatment Processes

Why do we need to treat our drinking water?

Industrial runoff

Agricultural runoff

Road runoff

Residential runoff

Industrial Runoff

Some industrial facilities generate ordinary domestic sewage that can run off into sewage drains.

Industries that generate wastewater with high concentrations of conventional pollutants (e.g. oil and grease), toxic pollutants (e.g. heavy metals, volatile organic compounds) or other nonconventional pollutants such as ammonia, need specialized treatment systems.

Agricultural Runoff

Nutrients (nitrogen and phosphorus) are typically applied to farmland as commercial fertilizer; animal manure; or spraying of municipal or industrial wastewater (effluent) or sludge.

Nitrates and phosphates derived from these can pose health risks to humans if they end up in the drinking water.

Sediment (loose soil) washed off fields is the largest source of agricultural pollution in the United States

Road Runoff

Sediments from construction sites and discharge of toxic chemicals such as motor fuels and concrete washout into the storm drains.

Residential/urban runoff

is surface runoff of rainwater created by urbanization. This runoff is a major source of urban flooding and water pollution in urban communities worldwide.

Water Treatment Process

http://www.youtube.com/watch?v=9z14l51ISwg&list=PL44OxmUx6A8pCBZRvLEg_fLf7WlWvwKod&index=2

Step 1: Raw Water Intake and Screens

Intake structure - delivers water to the water treatment plant Lake or Reservoir

Stream or River

Groundwater

Screens – prevent trash, logs, or fish from entering the treatment plant

Step 2: Coagulation and Flocculation In coagulation, coagulants like lime

and alum are added to the water, which causes particulates to clump together.

Next, the water is shaken into larger clumps, called flocs.

Coagulation and Flocculation

Step 3: Sedimentation

The sedimentation process requires that the water stand for 24 hours, which allows the clumps to settle to the bottom.

Settling Basin

Step 4: Second Filtration

The water is then filtered, 

disinfected (usually with chlorine) and aerated.

Aeration helps to remove certain contaminants like radon.

Disinfection

Disinfection – process designed to kill or deactivate most microorganisms in water, including disease causing bacteria

Types of disinfection: Physical

Ultraviolet (UV) rays

Heat

Chemical Chlorine

Ozone

Giardia lamblia

Fecal Coliforms

Storage and Distribution

Storage – keeping water for later use Elevated tanks Ground storage

tanks Distribution system

– network of pipes and pump stations that transports finished water from the treatment plant to the user