Home\Educate\Water Reuse 101\Research Projects\Year\2009\The Effects of Salinity on the Removal of Contaminants of Concern during Biological Water Reclamation

The Effects of Salinity on the Removal of Contaminants of Concern during Biological Water Reclamation

Project: 05-08
Type: Report
Year Released: 2009

Program: Principal
Funding Partner: Bureau of Reclamation, California State Water Resources Control Board
Total Investment: $99,675 (Cash)

Principal Investigator: Peter Fox, Arizona State University


Conventional wastewater treatment operations are dependent on the settleability of biosolids. Past research has shown that biosolid flocculation is dependent on the monovalent-to-divalent-cation ratio (M/D ratio). In other words, bioflocculation (aggregation of biological solids) is enhanced by the presence or absence of divalent cations such as calcium and/or magnesium ions and deteriorates with high concentrations of monovalent cations such as sodium, potassium, and ammonium ions.

Goals and Objectives

The project examines the effect of cation composition on the removal of hydrophobic contaminants of concern during wastewater treatment. This will be done by operating three sequencing batch reactors to evaluate the impact of cation composition on the removal of model compounds during wastewater treatment. A secondary objective will be to develop a fundamental understanding of removal mechanisms that can be used to improve the performance of wastewater systems. A third objective will be to relate laboratory observations to real world data where systematic changes in cation composition do not occur.

Research Approach

Some hydrophobic contaminants of concern are primarily removed during wastewater treatment by sorption into biosolids. Most estrogenic compounds are hydrophobic, and they were used as model compounds for this study. There were three tasks performed:

Task 1: Operation of the Bench-Scale Sequencing Batch Reactors to Evaluate the Effects of Cation Composition

Task 2: Collection of Field Data

Task 3: Data Analysis and Preparation of Final Report

Findings and Conclusions

Water softeners have a clear impact on reclaimed water quality by increasing the concentration of monovalent cations. This impact has become most pronounced when reclaimed water is used for irrigation, and the high salt content has a negative impact on plants and soil properties. This research demonstrates that water softeners may also be affecting the ability of water reclamation plants to remove hydrophobic compounds that are difficult to biodegrade. Many known estrogenic compounds are in this category, and estrogenic compounds were used as model compounds in this study.

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