w a t e r r e s e a r c h 5 6 ( 2 0 1 4 ) 1 4 8 e1 5 5
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.elsevier.com/locate/watres
Hydroxyl radical (OH) scavenging in young and mature landfill leachates Niloufar M. Ghazi a, Andres A. Lastra b, Michael J. Watts c,* a
Department of Civil & Environmental Engineering, Florida State University, 2525 Pottsdamer Street, Tallahassee, FL 32310, USA b Florida Department of Environmental Protection, Domestic Wastewater Section, 2600 Blair Stone Rd., Tallahassee, FL 32399, USA c Garver, 2049 E Joyce Blvd., Suite 400, Fayetteville, AR 72703, USA
article info
abstract
Article history:
The final discharge point for collected landfill leachates is frequently the local municipal
Received 19 September 2013
wastewater treatment facility. The salinity, color, nutrient, and anthropogenic organics
Received in revised form
contamination of leachates often necessitate some form of pre-treatment. When advanced
18 February 2014
oxidation processes (AOPs) are considered for pre-treatment, the unique composition of
Accepted 3 March 2014
dissolved organic matter (DOM) and the relatively high concentrations of some inorganic
Available online 13 March 2014
solutes in leachate will inhibit treatment efficiency. The most important benchmark for design of AOPs is the expected steady-state production of free radical (OH). Without a
Keywords:
quantitative assessment of total OH consumption in high-strength waste water, like a
Landfill
landfill leachate, efficient AOP treatment is uncertain. For this reason, two landfill leach-
Leachate
ates, distinct in color, DOM, and age of landfill, were characterized for OH-scavenging
Ozone
using an established competition kinetics method. After stripping the samples of inorganic
Hydrogen peroxide
carbon, the DOM in leachate from mature (stabilized) landfill was found to react with OH
Hydroxyl radical
at a rate of 9.76 108 M1s1. However, DOM in leachate from newer landfill was observed
Dissolved organic matter
to scavenge available OH at a faster rate (8.28 109 M1s1). The combination of fast rate of reaction with OH and abundance of DOM in the sampled leachate severely limited the contribution of OH to degradation of an O3- and OH-labile organic probe compound (bisphenol-a) in oxidized mature leachate (fOH ¼ 0.03). Substantial dosing of both O3 and H2O2 (>70 mg/L and >24 mg/L, respectively) may be required to see at least 1-log-removal (>90%) of an OH-selective leachate contaminant (i.e., parachlorobenzoic acid) in a mature landfill leachate. ª 2014 Elsevier Ltd. All rights reserved.
Abbreviations: AOP, Advanced Oxidation Process; DOM, Dissolved Organic Matter; POTW, Publicly-Owned Treatment Works; MSW, Municipal Solid Waste; COD, Chemical Oxygen Demand; BOD, Biochemical Oxygen Demand; LDOM, Leachate Dissolved Organic Matter; pCBA, parachlorobenzoic acid; TOC, Total Organic Carbon; BPA, bisphenol-a. * Corresponding author. Tel.: þ1 479 527 9100; fax: þ1 479 527 9101. E-mail addresses: [email protected] (N.M. Ghazi), [email protected] (A.A. Lastra), [email protected] (M.J. Watts). http://dx.doi.org/10.1016/j.watres.2014.03.001 0043-1354/ª 2014 Elsevier Ltd. All rights reserved.
149
w a t e r r e s e a r c h 5 6 ( 2 0 1 4 ) 1 4 8 e1 5 5
1.
Introduction
In 2010, approximately 54% of the municipal solid waste (MSW) generated in the U.S. was disposed in landfills (USEPA, 2011). When water (precipitation, ‘wetting’ water, and water in waste) infiltrates the layers of a landfill, it is contaminated by a variety of organic and inorganic pollutants. Previous studies have demonstrated that 1 ton of MSW disposed in landfill will produce 0.2 m3 of leachate (Kurniawan and Lo, 2009). A leachate collection system often consists of impermeable liners, pipes, pumps, and centralized storage. Leachate characteristics are dependent on the type of waste buried in the landfill, location, and local climate. In general, landfill leachates are characterized by high COD, low biodegradability, high turbidity, and poor UV transmittance. Often the age of landfill plays an important role in the quality of collected leachate. The pH of young (or ‘recent’ landfill; generally,
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.elsevier.com/locate/watres
Hydroxyl radical (OH) scavenging in young and mature landfill leachates Niloufar M. Ghazi a, Andres A. Lastra b, Michael J. Watts c,* a
Department of Civil & Environmental Engineering, Florida State University, 2525 Pottsdamer Street, Tallahassee, FL 32310, USA b Florida Department of Environmental Protection, Domestic Wastewater Section, 2600 Blair Stone Rd., Tallahassee, FL 32399, USA c Garver, 2049 E Joyce Blvd., Suite 400, Fayetteville, AR 72703, USA
article info
abstract
Article history:
The final discharge point for collected landfill leachates is frequently the local municipal
Received 19 September 2013
wastewater treatment facility. The salinity, color, nutrient, and anthropogenic organics
Received in revised form
contamination of leachates often necessitate some form of pre-treatment. When advanced
18 February 2014
oxidation processes (AOPs) are considered for pre-treatment, the unique composition of
Accepted 3 March 2014
dissolved organic matter (DOM) and the relatively high concentrations of some inorganic
Available online 13 March 2014
solutes in leachate will inhibit treatment efficiency. The most important benchmark for design of AOPs is the expected steady-state production of free radical (OH). Without a
Keywords:
quantitative assessment of total OH consumption in high-strength waste water, like a
Landfill
landfill leachate, efficient AOP treatment is uncertain. For this reason, two landfill leach-
Leachate
ates, distinct in color, DOM, and age of landfill, were characterized for OH-scavenging
Ozone
using an established competition kinetics method. After stripping the samples of inorganic
Hydrogen peroxide
carbon, the DOM in leachate from mature (stabilized) landfill was found to react with OH
Hydroxyl radical
at a rate of 9.76 108 M1s1. However, DOM in leachate from newer landfill was observed
Dissolved organic matter
to scavenge available OH at a faster rate (8.28 109 M1s1). The combination of fast rate of reaction with OH and abundance of DOM in the sampled leachate severely limited the contribution of OH to degradation of an O3- and OH-labile organic probe compound (bisphenol-a) in oxidized mature leachate (fOH ¼ 0.03). Substantial dosing of both O3 and H2O2 (>70 mg/L and >24 mg/L, respectively) may be required to see at least 1-log-removal (>90%) of an OH-selective leachate contaminant (i.e., parachlorobenzoic acid) in a mature landfill leachate. ª 2014 Elsevier Ltd. All rights reserved.
Abbreviations: AOP, Advanced Oxidation Process; DOM, Dissolved Organic Matter; POTW, Publicly-Owned Treatment Works; MSW, Municipal Solid Waste; COD, Chemical Oxygen Demand; BOD, Biochemical Oxygen Demand; LDOM, Leachate Dissolved Organic Matter; pCBA, parachlorobenzoic acid; TOC, Total Organic Carbon; BPA, bisphenol-a. * Corresponding author. Tel.: þ1 479 527 9100; fax: þ1 479 527 9101. E-mail addresses: [email protected] (N.M. Ghazi), [email protected] (A.A. Lastra), [email protected] (M.J. Watts). http://dx.doi.org/10.1016/j.watres.2014.03.001 0043-1354/ª 2014 Elsevier Ltd. All rights reserved.
149
w a t e r r e s e a r c h 5 6 ( 2 0 1 4 ) 1 4 8 e1 5 5
1.
Introduction
In 2010, approximately 54% of the municipal solid waste (MSW) generated in the U.S. was disposed in landfills (USEPA, 2011). When water (precipitation, ‘wetting’ water, and water in waste) infiltrates the layers of a landfill, it is contaminated by a variety of organic and inorganic pollutants. Previous studies have demonstrated that 1 ton of MSW disposed in landfill will produce 0.2 m3 of leachate (Kurniawan and Lo, 2009). A leachate collection system often consists of impermeable liners, pipes, pumps, and centralized storage. Leachate characteristics are dependent on the type of waste buried in the landfill, location, and local climate. In general, landfill leachates are characterized by high COD, low biodegradability, high turbidity, and poor UV transmittance. Often the age of landfill plays an important role in the quality of collected leachate. The pH of young (or ‘recent’ landfill; generally,
