7.1 Design considerations for tertiary treatment

Tertiary treatment is the final stage in wastewater processing, targeting specific contaminants. It's crucial for meeting strict water quality standards and enabling water reuse. The choice of treatment methods depends on effluent goals, influent characteristics, and regulatory requirements.

Design considerations for tertiary treatment involve balancing effectiveness, cost, and sustainability. Factors like influent quality, available space, and emerging contaminants shape technology selection. Filtration, disinfection, and advanced oxidation are common tertiary processes, each with unique design criteria.

Tertiary Treatment Design Considerations

Factors in tertiary treatment selection

Top images from around the web for Factors in tertiary treatment selection

• 

  A scenario-based multiple attribute decision-making approach for site selection of a wastewater ... View original

  Is this image relevant?

• 

  A Preliminary Comparative Analysis of MBR and CAS Wastewater Treatment Systems View original

  Is this image relevant?

• 

  Frontiers | Valorization of Wastewater Resources Into Biofuel and Value-Added Products Using ... View original

  Is this image relevant?

• 

  A scenario-based multiple attribute decision-making approach for site selection of a wastewater ... View original

  Is this image relevant?

• 

  A Preliminary Comparative Analysis of MBR and CAS Wastewater Treatment Systems View original

  Is this image relevant?

1 of 3

Top images from around the web for Factors in tertiary treatment selection

• 

  A scenario-based multiple attribute decision-making approach for site selection of a wastewater ... View original

  Is this image relevant?

• 

  A Preliminary Comparative Analysis of MBR and CAS Wastewater Treatment Systems View original

  Is this image relevant?

• 

  Frontiers | Valorization of Wastewater Resources Into Biofuel and Value-Added Products Using ... View original

  Is this image relevant?

• 

  A scenario-based multiple attribute decision-making approach for site selection of a wastewater ... View original

  Is this image relevant?

• 

  A Preliminary Comparative Analysis of MBR and CAS Wastewater Treatment Systems View original

  Is this image relevant?

1 of 3

• Effluent quality goals drive treatment technology choices based on intended reuse applications (irrigation, industrial, potable) and discharge requirements (nutrient limits, toxicity)
• Influent water characteristics, including contaminants of concern (nutrients, pathogens, micropollutants) and variability in flow and composition, influence the selection of appropriate treatment processes
• Available footprint and site constraints, such as land area requirements for different technologies and compatibility with existing infrastructure, impact the feasibility of tertiary treatment options
• Capital and operating costs, including initial investment and construction costs, energy consumption and chemical usage, and maintenance and replacement requirements, are critical factors in the decision-making process
• Sustainability considerations, such as greenhouse gas emissions, resource recovery potential (water, nutrients, energy), and life cycle assessment of treatment alternatives, are increasingly important in tertiary treatment design

Impact of influent water quality

• Upstream treatment processes, including the efficiency of primary and secondary treatment, determine the residual contaminants entering the tertiary stage and influence the required level of additional treatment
• Seasonal variations and extreme events, such as temperature effects on biological and chemical processes and stormwater inflows and combined sewer overflows, can significantly impact tertiary treatment performance
• Emerging contaminants, including pharmaceuticals, personal care products, and endocrine disruptors, pose unique challenges for removal mechanisms and efficiency of different technologies
• Fouling and scaling potential, caused by mineral precipitation and organic matter accumulation, may necessitate pretreatment requirements (filtration, softening) to maintain the effectiveness of tertiary treatment processes

Design criteria for tertiary technologies

• Filtration systems
  • Media type and configuration (sand, activated carbon, membranes) are selected based on target contaminants and desired removal efficiency
  • Hydraulic loading rates and backwash frequency are designed to optimize particle removal and minimize head loss
  • Particle removal efficiency and effluent turbidity targets are established to meet reuse or discharge standards
• Disinfection processes
  • Chlorination, UV irradiation, and ozonation are common disinfection methods with varying effectiveness against different pathogens
  • Dose requirements and contact time are determined based on influent water quality and desired level of inactivation
  • Disinfection byproduct formation and control strategies are considered to minimize potential health risks
• Advanced oxidation processes (AOPs)
  • Combination of oxidants and catalysts ($H_2O_2$/UV, $O_3$/UV) are selected based on target contaminants and required oxidation capacity
  • Reaction kinetics and oxidation capacity are optimized to achieve desired removal efficiency
  • Energy consumption and operational complexity are evaluated to ensure cost-effectiveness and ease of operation
• Adsorption and ion exchange
  1. Adsorbent properties and regeneration methods are chosen based on target contaminants and system performance requirements
  2. Empty bed contact time and breakthrough curves are used to design the system and determine the frequency of media replacement or regeneration
  3. Selectivity for target contaminants and competing ions is considered to ensure effective removal and minimize interference

Role of regulatory requirements

• Water quality standards and discharge permits, including maximum contaminant levels (MCLs) and water quality criteria, dictate the required level of treatment and guide the selection of tertiary technologies
• Reuse guidelines and regulations, such as fit-for-purpose treatment requirements and pathogen and chemical contaminant limits for different reuse categories, influence the design of tertiary treatment systems
• Emerging contaminant regulations, including state and federal initiatives for monitoring and control and anticipated future regulatory developments, drive the need for advanced treatment technologies capable of removing these pollutants
• Operator certification and training requirements, including minimum qualifications and continuing education, ensure the proper operation and maintenance of tertiary treatment systems, while standard operating procedures and emergency response plans help maintain consistent performance and address potential issues