Fate of malathion and a phosphonic acid in activated sludge with varying solids retention times.
This study examined the ability of activated sludge (AS) to sorb and biodegrade ethylmethylphosphonic acid (EMPA) and malathion, a degradation product and surrogate, respectively, for an organophosphate chemical warfare agent. Sorption equilibrium isotherm experiments indicate that sorption of EMPA and malathion to AS is negligible. EMPA at a concentration of 1 mg L(-1) degraded by approximately 30% with apparent first-order kinetics, possibly via co-metabolism from nitrification. Heterotrophic bacteria and abiotic mechanisms, however, are largely responsible for malathion degradation also with apparent first-order kinetics. EMPA did not inhibit chemical oxygen demand (COD) oxidation or nitrification activity, although malathion did appear to induce a stress response resulting in inhibition of COD oxidation. The study also included a 30-day experiment in which malathion, at a concentration of 5 mg L(-1), was repeatedly fed to AS in bench-scale sequencing batch reactors (SBRs) operating at different solids retention times (SRTs). Peak malathion concentrations occurred at day 4.5, with the longer SRTs yielding greater peak malathion concentrations. The AS reduced the malathion concentrations to nearly zero by day 10 for all SRTs, even when the malathion concentration in the influent increased to 20.8 mg L(-1). The data suggest a biodegradation pathway for malathion involving an oxygenase. Phylogenetic analyses revealed that all samples had an abundance of Zoogloea, though there was greater bacterial diversity in the SBR with the SRT of 50 days. The SBR with an SRT of 9.5 days had an apparent reduction in the diversity of the bacterial community.
Air Force Institute of Technology, Department of Systems Engineering and Management, 2950 Hobson Way, Wright-Patterson AFB, OH 45433, USA. Electronic address: allen.janeczko.1@us.af.mil.
Allen K
AK
Janeczko
Air Force Institute of Technology, Department of Systems Engineering and Management, 2950 Hobson Way, Wright-Patterson AFB, OH 45433, USA. Electronic address: edward.walters@us.af.mil.
Edward B
EB
Walters
Air Force Institute of Technology, Department of Systems Engineering and Management, 2950 Hobson Way, Wright-Patterson AFB, OH 45433, USA. Electronic address: steven.schuldt@us.af.mil.
Steven J
SJ
Schuldt
US Environmental Protection Agency, National Homeland Security Research Center, 26 W. Martin Luther King Drive, Mailstop NG-16, Cincinnati, OH 45268, USA. Electronic address: magnuson.matthew@epa.gov.
Matthew L
ML
Magnuson
US Environmental Protection Agency, National Homeland Security Research Center, 26 W. Martin Luther King Drive, Mailstop NG-16, Cincinnati, OH 45268, USA. Electronic address: willison.stuart@epa.gov.
Stuart A
SA
Willison
University of Dayton Research Institute, 300 College Park, Dayton, OH 45469, USA. Electronic address: lisa.brown@udri.udayton.edu.
Lisa M
LM
Brown
Air Force Research Laboratory, Aerospace Systems Directorate, Fuels and Energy Branch, Wright-Patterson AFB, OH 45433, USA. Electronic address: oscar.ruiz@us.af.mil.
Oscar N
ON
Ruiz
Air Force Institute of Technology, Department of Systems Engineering and Management, 2950 Hobson Way, Wright-Patterson AFB, OH 45433, USA. Electronic address: daniel.felker@us.af.mil.
Daniel L
DL
Felker
Air Force Institute of Technology, Department of Systems Engineering and Management, 2950 Hobson Way, Wright-Patterson AFB, OH 45433, USA. Electronic address: leeann.racz@us.af.mil.
LeeAnn
L
Racz
D065966:Absorption, Physicochemical; D001419:Bacteria / Q000145:classification / Q000378:metabolism*; D001673:Biodegradation, Environmental; D019149:Bioreactors / Q000382:microbiology; D002851:Chromatography, High Pressure Liquid; D004784:Environmental Monitoring; D007306:Insecticides / Q000378:metabolism; D008294:Malathion / Q000378:metabolism*; D064307:Microbiota; D063065:Organophosphonates / Q000378:metabolism*; D012722:Sewage / Q000382:microbiology*; D053719:Tandem Mass Spectrometry; D014874:Water Pollutants, Chemical / Q000378:metabolism*
D007306:Insecticides; D063065:Organophosphonates; D012722:Sewage; D014874:Water Pollutants, Chemical; C108318:ethyl methylphosphonic acid; D008294:Malathion
Activated sludge; Ethylmethylphosphonic acid; Malathion; Organophosphate; Solids retention time