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Title: Evaluation of Ferrate(VI) as an Conditioner for Dewatering Wastewater Biosolids

item McConnell, Laura
item Rice, Clifford
item Millner, Patricia

Submitted to: American Chemical Society Symposium Series
Publication Type: Book / Chapter
Publication Acceptance Date: 9/1/2007
Publication Date: 7/25/2008
Citation: Kim, H., Kim, Y., Sharma, V., Mcconnell, L.L., Torrents, A., Rice, C., Millner, P.D., Ramirez, M. 2008. Evaluation of Ferrate(VI) as an Conditioner for Dewatering Wastewater Biosolids. American Chemical Society Symposium Series. 19:326-338.

Interpretive Summary: Biosolids are generated from wastewater treatment. These solids are sometimes used as soil amendments on agricultural lands and in remediation projects. In order to protect public safety, biosolids materials must be stabilized prior to application to mitigate pathogens and odors. Ferrate is a highly reactive oxidant which degrades quickly into harmless components. It has been shown to reduce odors, pathogens and certain pollutant concentrations in biosolids. In this report, this chemical is being tested as a conditioner to enhance dewatering of biosolids. Dewatering efficiency is critical to reduce the overall mass of biosolids produced from the wastewater plant. Tests with three different dewatering approaches reveal that ferrate is not effective at enhancing dewatering processes compared to traditional polymer treatment as the biosolids acquire a gel-like consistency after treatment. The potential for ferrate to stabilize biosolids with respect to pathogens, odors and organic pollutants warrants further experimentation to optimize the current formulation to reduce gel formation.

Technical Abstract: Land application of sludge/biosolids is a commonly used practice for final utilization. Therefore, adequate conditioning and stabilization of wastewater solids is very critical for safe land application. The addition of ferrate (FeO42-) has the potential to improve the dewaterbility of solids, destroy pathogenic organisms and reduce certain endocrine disrupters. In this study, the dewaterbility and stabilization of thickened sludge treated with ferrate was evaluated under controlled laboratory conditions. To evaluate dewaterbility, three different techniques; belt-press, centrifugation, and vacuum filtration, were applied to dewater a mixture of solids. In addition, once biosoilds are generated, their safety and quality especially in terms of reduced endocrine disrupting compounds (EDCs) as well as pathogens become an important issue to the public. Therefore, the effectiveness of ferrate (FeO42-) in disinfecting microorganisms and in oxidizing EDCs, i.e., nonylphenols and polybrominated diphenyl ethers, is briefly discussed.