Journal of Environmental Treatment Techniques  
2020, Volume 8, Issue 3, Pages: 861-869  
J. Environ. Treat. Tech.  
ISSN: 2309-1185  
Journal web link:  
Application of Box-Behnken Design (BBD) to  
Optimizing COD Removal from Fresh Leachate  
using Combination of Ultrasound and Ultraviolet  
Neamatollah Jaafarzadeh , Mohammad Hasan Zarghi , Mobina Salehin , Aliakbar  
Roudbari , Amir Zahedi  
1Toxicology Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran  
Student Research Committee, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran  
Department of Environmental Health Engineering, Semnan University of Medical Sciences, Semnan, Iran  
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  
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  
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:,, phone: +989101107810.