title: Nitrite addition to acidified sludge significantly improves digestibility, toxic metal removal, dewaterability and pathogen reduction.
abstract: Sludge management is a major issue for water utilities globally. Poor digestibility and dewaterability are the main factors determining the cost for sludge management, whereas pathogen and toxic metal concentrations limit beneficial reuse. In this study, the effects of low level nitrite addition to acidified sludge to simultaneously enhance digestibility, toxic metal removal, dewaterability and pathogen reduction were investigated. Waste activated sludge (WAS) from a full-scale waste water treatment plant was treated at pH 2 with 10 mg NO2--N/L for 5 h. Biochemical methane potential tests showed an increase in the methane production of 28%, corresponding to an improvement from 247 ± 8 L CH4/kg VS to 317 ± 1 L CH4/kg VS. The enhanced removal of toxic metals further increased the methane production by another 18% to 360 ± 6 L CH4/kg VS (a total increase of 46%). The solids content of dewatered sludge increased from 14.6 ± 1.4% in the control to 18.2 ± 0.8%. A 4-log reduction for both total coliforms and E. coli was achieved. Overall, this study highlights the potential of acidification with low level nitrite addition as an effective and simple method achieving multiple improvements in terms of sludge management.
authors.affiliation: The University of Queensland, Advanced Water Management Centre (AWMC), QLD 4072, Australia.
authors.forename: Fangzhou
authors.initials: F
authors.lastname: Du
authors.affiliation: The University of Queensland, Advanced Water Management Centre (AWMC), QLD 4072, Australia.
authors.forename: Jürg
authors.initials: J
authors.lastname: Keller
authors.affiliation: The University of Queensland, Advanced Water Management Centre (AWMC), QLD 4072, Australia.
authors.forename: Zhiguo
authors.initials: Z
authors.lastname: Yuan
authors.affiliation: The University of Queensland, Advanced Water Management Centre (AWMC), QLD 4072, Australia.
authors.forename: Damien J
authors.initials: DJ
authors.lastname: Batstone
authors.affiliation: The University of Queensland, Advanced Water Management Centre (AWMC), QLD 4072, Australia.
authors.forename: Stefano
authors.initials: S
authors.lastname: Freguia
authors.affiliation: The University of Queensland, Advanced Water Management Centre (AWMC), QLD 4072, Australia.|The University of Queensland, The School of Civil Engineering, QLD 4072, Australia.
authors.forename: Ilje
authors.initials: I
authors.lastname: Pikaar
mesh_terms: D019216:Metals, Heavy / Q000378:metabolism*; D009573:Nitrites / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D012722:Sewage; D062065:Wastewater / Q000737:chemistry / Q000382:microbiology; D014871:Water Microbiology; D018508:Water Purification
chemical_list: D019216:Metals, Heavy; D009573:Nitrites; D012722:Sewage; D062065:Wastewater