WATER TREATMENT

Point Source of Polluted Water in Gargas, France

Is Bottled Water the Answer?

• U.S.: some of the cleanest drinking water

• Bottled water– Some from tap water– 40% bacterial contamination– Fuel cost to manufacture the plastic bottles– Recycling of the plastic

• Growing back-to-the-tap movement

Trash Truck Disposing of Garbage into a River in Peru

Natural Capital Degradation: Highly Polluted River in China

Girl Sits on the Edge of a Road beside a Stream Loaded with Raw Sewage in Iraq

Sewage Treatment Reduces Water Pollution (1)

• STRATEGY IS TO REDUCE POINT SOURCE POLLUTION

• Septic tank system

• Wastewater or sewage treatment plants

• SETTLING TANK- where grease and oil rise to the top and sludge settles. Solids are decomposed by bacteria. This is why, in theory, you should not use chlorinated cleaning products.

• DRAIN FIELD- liquid waste drain from pipes and percolate downward filtering and allowing bacteria to biodegrade materials

Solutions: Septic Tank System

Process of wastewater treatment

– Primary sewage treatment• Physical process-uses large screens and a grit tank to

remove large objects and grease and allow organic solids to settle out in the form of sludge.

Top view of Forest City Wastewater treatment plant

• 1. Headworks BuildingThis houses a mechanical bar screen and grit/grease removal system which removes the larger solids and readies the flow for entry into the First-Stage Aeration Basins

• 2. First-Stage Aeration BasinsThese two basins provide an optimum oxygen supply for decomposition of the sewage by bacteria. The flow is regularly checked for nutrients, pH, solids, pathogens, metals and organic chemicals. The flow then enters the large Second-Stage Aeration Basin.

• 3. Second-Stage Aeration BasinHere further oxygenation and decomposition occur. A complex group of micro-organisms break down (feed on) on the suspended or dissolved organic impurities remaining in the water. No chemicals are used throughout this decomposition process, only the natural action of many bacterial species.

• 4. ClarifiersFrom the big basin flow gravitates to two clarifiers, the round settling tanks. Remaining solids settle, and most are returned back to the aeration basins at a rate of 1.3 MGD. The clear top layer in the clarifiers is then chlorinated to destroy pathogens, then de-chlorinated with sulfur dioxide prior to release to Second Broad River. This effluent meets or exceeds all EPA requirements for biological oxygen demand rates.

• Secondary sewage treatment-employs aerobic bacteria to degrade organic waste. Here further oxygenation and decomposition occur. A complex group of micro-organisms break down (feed on) on the suspended or dissolved organic impurities remaining in the water. No chemicals are used throughout this decomposition process, only the natural action of many bacterial species.

• Aeration- used to introduce additional oxygen

Aeration of sewage to encourage the aerobic bacteria for decomposition

Ignaz Semmelweis

– Tertiary or advance sewage treatment

The clear top layer in the clarifiers is then chlorinated to destroy pathogens, • Bleaching, chlorination kills microorganisms such as

chlolera. then de-chlorinated with sulfur dioxide prior to release to Second Broad River• The use of filters to remove phosphates and nitrates

Sewage sludge or biosolids

Solutions: Primary and Secondary Sewage Treatment