Water and Wastewater Treatment Process

Introduction

• Water and waste from homes, businesses, and industrial facilities flow through a collection system network.
• The U.S. has approximately 800,000 miles of collection systems and 500,000 miles of private laterals.
• Wastewater is typically moved via gravity, with pumps or lift stations used when pipes get too deep.
• Older cities may have combined sewers for stormwater and sewage.
• Wastewater travels to 16,000 publicly owned Water Resource Recovery Facilities.

Headworks

• Purpose: Remove inorganic matter from wastewater.
• Process:
  • Influent screens filter out large debris like rags and cans.
  • Debris is collected and disposed of in a landfill.
• Grit Removal Chamber:
  • Separates heavy particles like sand; grit is abrasive and can erode equipment.
  • Heavier grit settles at the bottom, scraped away by a rake.

Primary Treatment

• Goal: Separate water from solids known as organic matter.
• Process:
  • Fine screens remove smaller debris, collected and taken to landfills.
  • Primary clarification allows solids to settle; oil/grease skimmed off.
  • Solids are sent to biosolids treatment.

Secondary Treatment

• Purpose: Remove nutrients like phosphorus and nitrogen.
• Process:
  • Aeration Basin: Uses biological action, not physical separation.
    • Oxygen is added to support bacteria that feed on solids/nutrients.
  • Secondary Clarification: Similar to primary clarification.
    • Solids transform into activated sludge, part returned to aeration basin.

Advanced Treatment and Disinfection

• Advanced Treatment: Produces ultra-clean water for reuse.
  • Membrane Filter: Forces water through small pores, removing fine particles.
• Disinfection: Removes remaining bacteria/microorganisms.
  • Methods include chlorine, ultraviolet, and ozonation.

Solids Treatment Process

• Goal: Convert solids into biosolids for beneficial reuse.
• Thickening and Dewatering: Concentrates solids, removes water.
  • Centrifuge: Separates water from solids.
  • Anaerobic Digester:
    • Reduces pathogens and volatile solids.
    • Produces biogas (methane and CO2) for energy.
  • Dewatering: Final step using a belt press.

Biosolids and Energy Production

• Biosolids: Used in agriculture as fertilizer after disinfection.
• Energy: Some plants self-sustain or sell electricity back to the grid.

Challenges and Importance

• Water sector faces challenges like urbanization and aging infrastructure.
• Investments in infrastructure create jobs and ensure clean water for future generations.
• Water is a crucial resource: "Water's worth it."