Resource recovery in wastewater treatment is a game-changer. It turns waste into valuable resources like nutrients, energy, and water. This approach reduces environmental impact and promotes sustainability by extracting and reusing these materials.

Methods for recovery include struvite precipitation for phosphorus, ammonia stripping for nitrogen, and anaerobic digestion for energy. These practices offer economic benefits, like cost reduction and potential revenue, while also helping the environment by reducing emissions and water stress.

Resource Recovery in Wastewater Treatment

Principles of resource recovery

• Views wastewater as a valuable resource containing nutrients, energy, and water that can be extracted and reused
• Extracts valuable materials (nutrients, energy, water) from wastewater to reduce the environmental impact and promote sustainability
• Reduces environmental impact by recovering resources and minimizing waste disposal
• Promotes sustainability and circular economy principles by reusing recovered resources and reducing reliance on finite resources

Methods for nutrient and energy recovery

• Nutrient recovery
  • Phosphorus recovery
    1. Struvite precipitation: Controlled precipitation of struvite ($MgNH_4PO_4 \cdot 6H_2O$) from wastewater to recover phosphorus as a valuable fertilizer
    2. Adsorption and desorption: Uses adsorbents (zeolites, activated carbon) to capture and release phosphorus for reuse
  • Nitrogen recovery
    1. Ammonia stripping: Removes ammonia from wastewater through volatilization and absorption, producing an ammonia-rich solution for fertilizer use
    2. Ion exchange: Uses ion exchange resins to selectively remove ammonium ions from wastewater, which can be regenerated and reused
• Energy recovery
  • Anaerobic digestion: Converts organic matter in wastewater into biogas (methane and carbon dioxide) that can be used for heat and power generation
  • Microbial fuel cells: Generates electricity from the oxidation of organic matter by microorganisms, treating wastewater while producing renewable energy
  • Heat recovery: Captures heat from wastewater using heat exchangers or heat pumps, which can be used for space heating or preheating incoming wastewater
• Water recovery
  • Membrane filtration: Uses membranes (ultrafiltration, nanofiltration, reverse osmosis) to remove contaminants and produce high-quality reclaimed water for various applications (irrigation, industrial use)
  • Advanced oxidation processes: Applies oxidizing agents (ozone, hydrogen peroxide) and UV light to degrade pollutants and improve water quality for reuse purposes

Benefits of recovery practices

• Economic benefits
  • Reduces costs by recovering resources (fertilizers, energy) instead of purchasing them externally
  • Generates potential revenue by selling recovered resources (struvite, biogas)
  • Improves energy efficiency and reduces operational costs through on-site energy production and heat recovery
  • Extends the lifespan of wastewater treatment infrastructure by reducing scaling and fouling issues (struvite precipitation)
• Environmental benefits
  • Reduces greenhouse gas emissions by offsetting fossil fuel use with recovered biogas and reducing energy consumption
  • Decreases eutrophication potential by removing excess nutrients (phosphorus, nitrogen) from wastewater and preventing their discharge into water bodies
  • Reduces water stress by providing an alternative source of water (reclaimed water) for non-potable applications (irrigation, industrial use)
  • Promotes a circular economy and reduces reliance on finite resources by recovering and reusing valuable materials from wastewater

Case studies in wastewater treatment

• Struvite recovery at the Ostara Pearl® process (installed in wastewater treatment plants worldwide)
  • Recovers phosphorus as struvite pellets, which can be used as a slow-release fertilizer, reducing the need for mined phosphorus
  • Reduces maintenance costs by preventing struvite scaling in pipes and equipment, extending the lifespan of the infrastructure
• Biogas production and cogeneration at the Davyhulme Wastewater Treatment Works (Manchester, UK)
  • Produces biogas through anaerobic digestion of sewage sludge, which is used in combined heat and power (CHP) engines to generate electricity and heat
  • Reduces the plant's carbon footprint and energy costs by using renewable biogas for on-site energy production
• Water reuse at the NEWater facilities (Singapore)
  • Produces high-grade reclaimed water using advanced membrane filtration (reverse osmosis) and UV disinfection
  • Supplies reclaimed water for industrial use and indirect potable use (blending with reservoir water), enhancing water security in a water-scarce region