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Study of Innovative Treatments for Reclaimed Water

Project: 02-09
Type: White Paper
Year Released: 2012

Program: Principal
Funding Partners: Bureau of Reclamation, Southwest Florida Water Management District, Phoenix, Los Angeles County Sanitation District, Dublin San Ramos Services District
Total Investment: $535,000 (Cash)

Principal Investigators: Andrew Salveson, Carollo Engineers, and Karl Linden, University of Colorado Boulder

Background

Tertiary treatment of wastewater includes a wide variety of treatment targets and applicable technologies. Although several are considered common practice (e.g., chlorination, UV disinfection), many less-established technologies are available to utilities alongside the proven treatment options. A study was conducted on current and emerging tertiary and advanced treatment technologies for reclaimed water disinfection and chemical constituent destruction in an effort to relate capital and operational costs to performance.

Goals and Objectives

The project investigates current and emerging tertiary and advanced treatment technologies for reclaimed water disinfection and chemical constituent destruction. The primary goal of the research was to identify and determine the relatively low-cost technology (or technologies) that is capable of the simultaneous destruction of both pathogens and chemical constituents.

Research Approach

By using rigorous selection criteria, candidate treatment technologies were selected and tested at bench scale at Duke University and at four pilot sites in Florida, North Carolina, and California.

The initial process involved the review of 22 established and emerging wastewater treatment technologies, including emerging technologies such as electron beam radiation, ultrasound, and electrodialysis reversal. After detailed review and a kickoff workshop with the Foundation’s Project Advisory Committee and project stakeholders, the research team selected several market-ready technologies for detailed bench-scale evaluations, including:

  • UV, low-pressure (LPUV) and medium-pressure (MPUV)
  • Ozone (O3)
  • Chlorine (free and preformed monochloramines)
  • Peracetic acid (PAA)
  • Advanced oxidation processes (AOP, including LPUV/H2O2, LPUV/PAA, O3/H2O2)
  • Ultrafiltration (UF)

Findings and Conclusions

All of the aforementioned technologies, with the exceptions of PAA and chloramines, substantially reduced the concentrations of both pathogens and chemical constituents; however, free chlorine showed mixed results in comparison. In the case of UV-based AOPs, UV alone provides a robust disinfection barrier. The addition of PAA, H2O2, and TiO2 promotes the formation of free radical species (such as hydroxyl radicals), enhancing oxidation rates of target organic compounds, particularly in the case of recalcitrant compounds. In contrast to UV-based technologies, ozone also readily destroys many targeted chemical constituents, but higher doses are required for equivalent pathogen disinfection, especially in the cases of (oo)cysts and spores. A clear link between the removal of particulates and the reduction in pathogens and chemical constituents was observed, demonstrating the importance of well-designed filtration as a component of a multiple barrier approach to advanced wastewater treatment.

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