WASTE MANAGEMENT

Wastewater

• Definition: Wastewater is any water negatively affected by anthropogenic influence.

• Sources:

  • Domestic activities

  • Industrial activities

  • Agricultural activities

  • Surface runoff

Municipal Wastewater Management

• Conveyance: Municipal wastewater is conveyed through either a combined sewer or a sanitary sewer.

• Treatment: Treated at a wastewater treatment plant.

Wastewater Treatment

• Purpose: To convert wastewater into an effluent suitable for discharge or reuse without adverse environmental impact.

Wastewater Contaminants

• Common contaminants in wastewater include:

  • Suspended solids

  • Biodegradable organics

  • Pathogenic bacteria

  • Nutrients

Advanced Wastewater Treatment (AWT)

• Definition: AWT refers to processes applied after conventional treatments to further purify wastewater. Often synonymous with tertiary treatment.

• Purpose: Reduces remaining suspended solids and biochemical oxygen demand (BOD) from wastewater after primary and secondary treatments.

• Focus: Removes soluble pollutants not effectively addressed by conventional biological methods.

• Cost: AWT is significantly more expensive, costing twice as much as secondary treatment.

Types of Advanced Wastewater Treatment Methods

For Suspended Solids:

• Methods:

  • Microscreening

  • Ultrafiltration

  • Chemical coagulation

For Dissolved Organic Matter:

• Methods:

  • Adsorption using activated carbon

  • Biological oxidation

Nutrient Removal:

• Phosphorus:

  • Precipitation and coagulation methods

• Ammonia:

  • Air-stripping and biological nitrification

• Inorganic Nitrogen:

  • Denitrification

Microscreening

• Definition: An advanced solid-liquid separation device in wastewater treatment that continuously removes debris.

• Mechanism: Utilizes a rotating drum with plastic or metallic mesh openings (20-60 micrometers).

Ultrafiltration (UF)

• Process: A membrane filtration process utilizing pressure gradients to separate contaminants through a semipermeable membrane.

• Application: Primarily for removing residual suspended solids and microorganisms.

• Membrane: Consists of thin membranes of organic polymers, about 0.005 to 0.01 inches thick.

Chemical Coagulation

• Process: Involves adding a coagulant to destabilize pollutants, forming larger particles (floc) that settle out as sludge.

• Common Coagulants: Natural/synthetic organic polymers and metal salts (e.g., alum, ferric sulfate).

Biological Oxidation

• Definition: Microbial process where microorganisms degrade organic matter contaminants present in wastewater.

• Mechanism: Microorganisms metabolize organic matter in the presence of oxygen and nutrients, aided by bacteria or fungi.

Types of Oxidation Ponds

Aerobic Ponds:

• Activity: High-rate algal ponds maintain dissolved oxygen (DO) due to algal photosynthesis.

• Depth: 30-45 cm.

Anaerobic Ponds:

• Conditions: Operate without DO; major products are CO2 and CH4; can remove 60% BOD.

• Depth: 2-5 m; optimum pH < 6.2.

Facultative Ponds:

• Process: Combine aerobic (surface) and anaerobic (bottom) conditions; can remove 95% BOD.

• Depth: 1-2 m.

Maturation Ponds:

• Function: Use algae to remove coliform, pathogens, and nutrients.

• Depth: 1 to 1.15 m, making them shallower than other pond types.

Adsorption Using Activated Carbon

• Definition: Activated carbon has porous structures, increasing surface area for adsorption.

• Uses: Effective in removing organics, chlorine, and fluorine from wastewater.

Chemical Precipitation

• Process: Used to remove inorganic phosphates by adding coagulants to wastewater.

• Result: Forms products like aluminum phosphate that precipitate from the solution.

Air Stripping

• Definition: A process that transfers volatile components from liquid to gas phase by allowing ammonia to escape into the air.

• Condition: Requires pH greater than 11 for complete conversion of ammonium.

Ion Exchange

• Description: Utilizes zeolites as molecular filters to remove ammonium from wastewater (90-97% efficiency).

Chlorination

• Process: Adding chlorine leads to the conversion of ammonium into nitrogen gas through several stepwise reactions.

Nitrification

• Definition: A microbial process that converts ammonia to nitrite and then nitrate through nitrifying bacteria.

• Steps:

  • Ammonia (NH3) to Nitrite (NO2) via Nitrosomonas

  • Nitrite (NO2) to Nitrate (NO3) via Nitrobacter

Denitrification

• Definition: The process of removing nitrogen from water, reducing nitrates to inert nitrogen gas under anaerobic conditions.

• Chemical Reaction Sequence:

  • NO3 → NO2 → NO → N2O → N2

Ozonation

• Use: Employs ozone gas (O3) as a disinfectant despite no residual effect in treated water.

Ultraviolet Radiation

• Definition: Involves exposing wastewater to UV light for disinfection.

Thank You!

• Acknowledgment to participants or audience.