Wastewater Treatment: Activated Sludge Process

Wastewater Treatment

Activated Sludge

• A biological wastewater treatment process that uses microorganisms to break down organic matter
• Involves mixing wastewater with a suspension of microorganisms (activated sludge) and oxygen
• The microorganisms feed on the organic matter, converting it into carbon dioxide, water, and energy
• The activated sludge is then separated from the treated water through sedimentation or filtration
• Advantages: effective for removing organic matter, nutrients, and pathogens; flexible in design and operation

Biological Nutrient Removal (BNR)

• A process that removes nitrogen and phosphorus from wastewater
• Involves creating an environment that promotes the growth of microorganisms that can convert nitrogen and phosphorus into harmless forms
• BNR can be combined with activated sludge treatment
• Nitrogen removal: nitrification (conversion of ammonia to nitrate) and denitrification (conversion of nitrate to nitrogen gas)
• Phosphorus removal: through biological uptake or chemical precipitation
• Importance: prevents eutrophication in water bodies, protects aquatic life

Disinfection

• A process that kills or inactivates pathogens in treated wastewater
• Methods: chlorination, ozone treatment, UV light, and filtration
• Goals: reduce risk of waterborne diseases, meet regulatory requirements
• Factors affecting disinfection: type and concentration of disinfectant, contact time, pH, temperature

Sedimentation

• A physical process that removes suspended solids from wastewater
• Involves allowing particles to settle to the bottom of a tank or basin
• Types: primary sedimentation (removes heavy solids), secondary sedimentation (removes biological solids)
• Factors affecting sedimentation: particle size and density, flow rate, tank design

Biochemical Oxygen Demand (BOD)

• A measure of the amount of oxygen required by microorganisms to break down organic matter in water
• Units: milligrams per liter (mg/L)
• Importance: indicator of water pollution, affects aquatic life and ecosystem balance
• Factors affecting BOD: type and amount of organic matter, temperature, pH, oxygen availability

Wastewater Treatment

Activated Sludge

• Uses microorganisms to break down organic matter in wastewater
• Involves mixing wastewater with microorganisms and oxygen
• Microorganisms convert organic matter into carbon dioxide, water, and energy
• Separation of activated sludge from treated water through sedimentation or filtration
• Effective in removing organic matter, nutrients, and pathogens
• Flexible in design and operation

Biological Nutrient Removal (BNR)

• Removes nitrogen and phosphorus from wastewater through microorganisms
• Creates an environment for microorganisms to convert nitrogen and phosphorus into harmless forms
• Can be combined with activated sludge treatment
• Nitrogen removal: nitrification (ammonia to nitrate) and denitrification (nitrate to nitrogen gas)
• Phosphorus removal: biological uptake or chemical precipitation
• Prevents eutrophication in water bodies and protects aquatic life

Disinfection

• Kills or inactivates pathogens in treated wastewater
• Methods: chlorination, ozone treatment, UV light, and filtration
• Goals: reduce risk of waterborne diseases and meet regulatory requirements
• Factors affecting disinfection: type and concentration of disinfectant, contact time, pH, and temperature

Sedimentation

• Removes suspended solids from wastewater through physical settling
• Allows particles to settle to the bottom of a tank or basin
• Types: primary sedimentation (removes heavy solids) and secondary sedimentation (removes biological solids)
• Factors affecting sedimentation: particle size and density, flow rate, and tank design

Biochemical Oxygen Demand (BOD)

• Measures the amount of oxygen required by microorganisms to break down organic matter
• Units: milligrams per liter (mg/L)
• Importance: indicator of water pollution, affects aquatic life and ecosystem balance
• Factors affecting BOD: type and amount of organic matter, temperature, pH, and oxygen availability

Wastewater Treatment

Activated Sludge

• Biological process used to remove organic matter and nutrients from wastewater
• Microorganisms break down organic matter into carbon dioxide, water, and energy
• Process occurs in aeration tanks with microorganisms, wastewater, and oxygen
• Microorganisms form a floc, trapping and removing suspended solids and pollutants

Biological Nutrient Removal (BNR)

Nitrogen Removal

• Microorganisms convert ammonia (NH3) to nitrite (NO2-) and then to nitrate (NO3-)
• Nitrate is then converted to nitrogen gas (N2)

Phosphorus Removal

• Phosphorus is converted into a form that can be removed through sedimentation

Disinfection

• Process used to kill or inactivate pathogens in wastewater
• Common disinfection methods: Chlorination, Ozone treatment, UV light treatment, Chlorine dioxide treatment
• Prevents the spread of waterborne diseases and protects public health and the environment

Biochemical Oxygen Demand (BOD)

• Measures the amount of organic matter in wastewater
• Measures the amount of oxygen required by microorganisms to break down organic matter
• BOD is typically measured over a 5-day period (BOD5)
• High BOD levels indicate high levels of organic matter, insufficient treatment, and potential for water pollution