Journal of Environmental Treatment Techniques
2020, Volume 8, Issue 3, Pages: 861-869
J. Environ. Treat. Tech.
ISSN: 2309-1185
Journal web link: http://www.jett.dormaj.com
Application of Box-Behnken Design (BBD) to
Optimizing COD Removal from Fresh Leachate
using Combination of Ultrasound and Ultraviolet
1
2*
3
Neamatollah Jaafarzadeh , Mohammad Hasan Zarghi , Mobina Salehin , Aliakbar
4
2
Roudbari , Amir Zahedi
1Toxicology Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
2
Student Research Committee, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
3
Department of Environmental Health Engineering, Semnan University of Medical Sciences, Semnan, Iran
4
Center for Social and Behavioral Sciences Research, Shahroud University of Medical Sciences, Shahroud, Iran
Received: 16/04/2020 Accepted: 03/05/2020 Published: 20/09/2020
Abstract
Municipal Solid Waste (MSW) landfill leachate contains highly concentrated organic substances which must be treated before
discharged into aqueous environments. This study was done to optimize the removal of COD from fresh landfill leachate using
combination of ultrasound and ultraviolet. The sample of fresh landfill leachate was obtained from a municipal landfill, and its COD
was measured. Box-Behnken design was applied to analyze and optimize the removal of COD by different variables, including pH,
contact time, ultrasound frequency and UV intensity. Based on this, 29 samples and three replications were tested. The analysis of
variance indicated quadratic model was significant for removal of COD. According to the model, the removal efficiency of COD was
obtained 92.1 % at optimal conditions (pH at 9.2, contact time of 54min, ultrasound frequency of 54 kHz and UV intensity of 45w). The
removal efficiency of COD was 91.8 % in these conditions which agrees well with the predicted response value. The BOD5/COD ratio
increased to 0.38 after treatment. Also, the values of average oxidation state (AOS) and carbon oxidation state (COS) increased to +1.9
and 3.49, respectively. This means that the treated leachate was much easier to biodegrade than the initial leachate.
Keywords: COD, Leachate, Ultrasound, Ultraviolet, BBD
1
Introduction1
Lifestyle changes and commercial and industrial growth
soil and mutagenic effect of human being as well as affecting
the ecology balance, etc [61].
The removal of organic matter based on COD (chemical
oxygen demand) is a common precondition before leachate
discharge into natural water bodies [8]. The concentration of
COD in young leachate is 36 times higher than in domestic raw
sewage. The pollutant potential of leachate is mainly related to
its organic load [62]. Most recently, a variety of physical,
biological and chemical processes have been widely used to
remove COD from landfill leachate [9, 10]. Advanced
oxidation processes (AOPs) as an innovative technique are
extremely promising, owing to their unique potential for the
generation of hydroxyl radicals (OH) that are highly reactive in
chemical solutions [9, 11, 12]. The produced hydroxyl radicals
in this process degrade the organic matter present in the
leachate of the landfill site [11]. AOPs include numerous
combinations of ultraviolet (UV) radiation, ultrasound (US),
photocatalysts, catalysts, fenton and strong oxidants [9, 13, 14].
Ultrasonic can degrade pollutants by applying thermal
dissociation (pyrolysis) and shear forces in addition to
producing hydroxyl radicals [15, 16]. The strong cavitations
and hot spots produced by ultrasound in an aqueous solution,
that causing shock waves (physical effect) and reactive free
radicals (chemical effect) by the violent collapse of the
capitation bubbles [17]. These effects accelerate the
decomposition of toxic chemicals [18]. Another method used
in many countries over the past years have led to a rapid
increase in the production of solid industrial and municipal
waste [1, 2]. The method of hygienic landfill for the final
disposal of solid waste material continues to be widely avowed
and used due to its economic benefits [3, 4]. The production of
leachate remains an unavoidable result of the waste disposal
[2]. The aqueous effluent produced as a result of the infiltration
of rainwater into the waste, together with biochemical
processes in the waste cells and the intrinsic water content of
the waste, constitute the leachate [5]. Leachate includes many
amounts of organic matter, which its humic constituents are
ammonia nitrogen, chlorinated organic, inorganic salts and
heavy metals [6, 7]. When leachate leaks out of them due to the
decomposition of waste materials, it carries all the biological
and chemical substances in the waste materials. The leachate of
the landfill is one of the most polluted types of sewage, which
has caused many health and environmental concerns due to the
extensive use of urban landfills for the final disposal of waste
[59]. Due to percolation of leachate through the soil and
migration of leachate by surface runoff contaminates the soil,
groundwater and surface water bodies in and around the landfill
site [60]. Discharge of landfill leachate to the environment
causes detrimental effect to the aquatic life, infertility of the
Corresponding author: Mohammad Hasan Zarghi, Student Research Committee, Ahvaz Jundishapur University of Medical Sciences,
Ahvaz, Iran. E-mail: mohandesmhz@gmail.com, zarghi.mh@ajums.ac.ir, phone: +989101107810.
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