Waste Treatment

Waste Water Treatment

• Wastewater treatment aims to return treated water to the environment, minimizing pollutants.
• This process involves primary, secondary, and tertiary treatment stages.
• Primary treatment physically separates large solids and sediments.
• Secondary treatment uses bacteria to decompose organic matter.
• Tertiary treatment utilizes methods like percolation, ozone, or UV light to remove phosphates and nitrates.

Sources of Wastewater Nitrogen

• A modeling study suggests wastewater adds 6.2 million tonnes of nitrogen to coastal waters globally.
• The top contributors to this nitrogen pollution include China (1,890,000 tonnes), India (659,000 tonnes), and the United States (358,000 tonnes).

Water Recycling

• Recycling wastewater is possible and can be used as a source of nutrients.
• Nutrients found in wastewater include potassium, phosphorus, and nitrogen, which can replace some agricultural fertilizer demand, potentially saving US$13.6 billion annually.

Sewer Systems

• Wastewater from households travels through sewer service laterals, sanitary sewer pipes, and intercepting sewer systems to treatment facilities.

Stormwater vs. Wastewater

• Stormwater runoff and wastewater are distinct.
• Wastewater comes from sinks, toilets, and other household fixtures, while stormwater is rain or snowmelt runoff.
• Stormwater is typically directed to separate storm drains and catch basins.

Types of Waste Disposal

• Sanitary landfills use compacted layers of earth to contain garbage and prevent leachate from reaching groundwater
• Clay liners help contain leachate, and methane gas is collected and used to generate electricity.

Hazardous Waste Disposal

• Secure landfills are specially designed to isolate hazardous waste from the environment to prevent pollution outside of the facility.

Fuel Combustion as Pollutant Source

• The burning of fossil fuels like coal, oil, and natural gas releases pollutants including carbon dioxide, sulfur dioxide, nitrogen oxides, mercury, and lead into the atmosphere.

Industrial Processes as Pollutant Source

• Industrial processes, including electrical energy generation, mineral processing, and fertilizer production, release harmful chemicals, like sulfur dioxide and nitrogen oxides, into the air, or into water.
• Sour gas, containing hydrogen sulfide, is processed to remove it , then sulfur dioxide is released.

Septic Tanks

• Septic tanks, common in rural areas, collect household wastewater and separate solids from liquids.
• The liquid waste then percolates through the soil, and bacteria decompose the organic matter.