Wastewater Treatment and Reuse Project

Introduction

Presenter: David William Graber

• Regional advisor and consultant
• The session is being recorded
• Participants who attend at least 5 out of 6 sessions will be eligible for a certificate of participation
• CREW+ Academy: Platform for water and sanitation solutions in the Caribbean

Project Overview

CREW+ Project

• Funded by the Global Environment Facility
• Co-implemented by IDB and UNEP in 18 countries
• Executed by GIZ, OAS, and the Secretariat of the Cartagena Convention

Goals:

• Mitigate effects of untreated wastewater on the environment and public health

Surveys

• Two surveys: Registration and Evaluation
• Participation in surveys counts towards the certificate

Introduction to Facilitator

Gustavo Adenis

• Water and sanitation specialist with over 15 years of experience
• Consultant to the World Bank in sanitation projects

Presentation Overview

• Divided into three parts
  1. Strategies for treating wastewater
  2. Review of treatment processes and technologies
  3. Key aspects for a reuse project

Strategies for Treating Wastewater

Main Goal:

• Provide universal access to sanitation
• Ensure all wastewater is treated

Technological Solutions:

• Centralized systems (single treatment plant for a city)
• Decentralized systems (smaller localized plants)
• On-site systems (treatment within households)
• Combination of different strategies

Conceptualizing a Wastewater Treatment System

• Start at the end (discharge/reuse point) to determine treatment requirements
• Evaluate technological alternatives, footprint, and costs
• Use a combination of taxes, transfers, and tariffs to cover costs
• Prioritize building systems that balance cost and effectiveness

Treatment Processes and Technologies

Pollutant Types:

• Inorganic solids (sand, metals, salts)
• Organic solids (carbohydrates, proteins, fats, pathogens)

Treatment Steps:

1. Pre-treatment: Removal of coarse and fine solids
   • Methods: Bar screens, sieves, grit chambers
2. Primary Treatment: Sedimentation and anaerobic digestion
   • Technologies: Settlers, anaerobic baffle reactors (ABRs), UASB reactors
3. Secondary Treatment: Reduce organic load through aerobic processes
   • Technologies: Aerated tanks, constructed wetlands, stabilization ponds, trickling filters
4. Tertiary Treatment: Further removal of nutrients and pathogens
   • Methods: Nitrification, denitrification, disinfection (UV, chlorine, ozone)

Selection Criteria and Efficiency

Technology Examples:

• Septic tanks: ~30% BOD removal
• Stabilization ponds: ~80% BOD removal
• Constructed wetlands, anaerobic reactors: ~90% BOD removal
• Activated sludge: >90% BOD removal

Advanced Treatments: Phosphorus removal via chemical precipitation

Key Aspects for Reuse Projects

Reuse Opportunities

• Crop irrigation: Conserves water, closes nutrient cycles, contributes to food safety
• City-wide: Parks, forests, landscapes
• Industrial: Process or cooling water
• Aquifer recharge: Treated wastewater injected into sand dunes

Key Considerations

1. Quantity and Quality of Wastewater

   • Consistent flow based on population or usage
   • Quality defined by standards and treatment technologies

2. Type of Crop and Soil

   • Crop type: Different crops have varying tolerance to water quality
   • Soil type: Permeability affects risk of groundwater contamination
   • Irrigation practices: Amount and frequency of irrigation

3. Health Risks

   • Product contamination, air transmission, direct contact
   • Avoidance of toxic elements and heavy metals

Guidelines and Standards

• Management guidelines for risks and health
• Sensitivity of groundwater linked to soil type and aquifer depth
• Application practices for effective reuse

Conclusion

• CREW+ Academy resources
• Emphasis on sustainable treatment and reuse to protect water resources

Upcoming Sessions:

• Governance, standards, and regulations in wastewater treatment and reuse