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Impact of Mainstream Low DO Conditions at a Full-scale MBR Water Reuse Plant

Project: 13-08
Program: Tailored Collaboration
Funding Partner: American Water
Total Budget: $365,777 (Cash: $100,000, In-Kind cash and service: $265,777)

Principal Investigator: Dr. Yunjie Tu, Ph.D., American Water

Background

Increasing world populations and water scarcity issues have increased reliance on water reclamation. Presently the membrane based treatment processes are expensive and energy intensive. Enhancing operational conditions to promote growth of novel organisms may help overcome some of these challenges and simultaneously may provide benefits for remediation of emerging contaminants (e.g. nitrosamines and/or pharmaceutical and personal care products).

Goals and Objectives

The project will:

  • Explore the use of novel organisms (i.e. low DO nitrifiers such as ammonia oxidizing bacteria (AOB)/ammonia oxidizing archaea (AOA), nitrite oxidizing bacteria (NOB) and/or anoxic ammonium oxidation- ANAMMOX bacteria) in a main stream MBR plant to reduce energy consumption and O&M costs associated with reclaimed water production.
  • Characterize the organism populations under various operational pressures (e.g. low DO and low substrate) in an existing full scale MBR system to avoid the need for side stream bioaugmentation.
  • Enhance nitrogen and phosphorus removal to reduce the discharge of nutrient and precursor for disinfection by products (e.g. nitrosamines) in reclaimed water.
  • Assess removal of recalcitrant dissolved organic nitrogen (RDON) and emerging contaminants (e.g. pharmaceutical or disinfection by products) by AOB/AOA cluster as well as the combination of anaerobic/aerobic activity in a stratified oxygen biofilm.
  • Evaluate the impact of greenhouse gas emissions under low DO conditions for reuse systems.

Research Approach

The project team will:

  • Install online instruments, such as NH4-N, NO2/NO3, COD, DO, pH sensors in different reactor zones to define existing operational conditions (i.e. nitrogen and carbon profiles for AOB/AOA) ANAMMOX bacteria growth). Determine the relevance of each parameter in future cost reduction for MBR systems.
  • Control the C to NO2- ratio, DO and SRT to allow AOB/AOA, NOB and ANAMMOX to reach optimal growth and coexist in a low DO and low substrate environment.
    • Implement automatic aeration control by nutrient parameters and DO setting to minimize energy consumption and maximize performance.
    • Install media with ANAMMOX seeded from our existing Membrane tank and ANAMOX obtained from the Beijing Drainage Group in a post anoxic zone and membrane tank.
    • Measure AOB/AOA, NOB, ANAMMOX activities at a full scale MBR plant by batch test. Conduct molecular analysis by qPCR, pyrosequencing and 16S rRNA sequence with a specially designed primer to capture functional genes of AOB/AOA, NOB and ANAMMOX.
  • Conduct an algal or bacterial bioassay with an existing ANAMMOX thick film or enriched AOB/AOA cluster to see if RDON or various emerging contaminants (e.g. antibiotics, triclosan, and benzotriazole) become biodegradable in a stratified anaerobic/aerobic biofilm.
  • Measure N2O and NO2- in anoxic and low DO zones to see if NO2- accumulation contributes to N2O emission by using N2O analyzer and lab analysis.

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