2020, Volume 8, Issue 2, Pages: 567-572  
J. Environ. Treat. Tech.  
ISSN: 2309-1185  
Journal web link: http://www.jett.dormaj.com  
Treatment of Landfill Leachate using Granular  
Multi-Stage Anaerobic Reactor: Optimisation  
through Response Surface Methodology  
1
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2
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Aida Batrisyia Jasni , Shreeshivadasan Chelliapan , Mohd Fadhil Md Din and Nithiya  
Arumugam2  
1
School of Civil Engineering, Faculty of Engineering, Universiti Teknologi Malaysia, Skudai, 81310, Johor, Malaysia  
2
Department of Engineering, Razak Faculty of Technology and Informatics, Universiti Teknologi Malaysia, Jalan Sultan Yahya Petra, 54100 Kuala Lumpur,  
Malaysia  
Centre for Environmental Sustainability and Water Security (IPASA), Research Institute for Sustainable Environment, Universiti Teknologi Malaysia,  
3
Skudai, 81310, Johor, Malaysia  
Received: 16/09/2019  
Accepted: 11/02/2020  
Published: 20/05/2020  
Abstract  
One of the most hazardous sources of pollution these days is landfill leachate. This harmful wastewater is not only affecting the  
environment, but also the health of beings surrounding the landfills. Numerous treatments have been used to treat this recalcitrant wastewater;  
however, anaerobic treatment has been in focus in recent years. In this study, we investigated the interactive effects of chemical oxygen  
demand (COD), leachate percentage and pH on the performance of a granular multi-stage anaerobic reactor (GMSAR) treating landfill  
leachate. Response surface methodology (RSM) was utilised to project the interaction effects of the operating conditions of the treatment  
system in terms of COD removal and biogas yield. The optimum region of the GMSAR was acquired at influent COD of 1239 mg/L, a  
leachate percentage of 14.2% and a pH of 7.3. These variables resulted in a 71.9% COD removal and 65.9mL/d of biogas yield. The  
percentage of leachate and COD influent resulted respectively in the most effective parameters on the COD removal and biogas yield of  
GMSAR.  
Keywords: Landfill leachate, Anaerobic treatment, Multi-stage anaerobic reactor, Response surface methodology, Biogas yield  
(
3). Leachate formed from water runoff at landfill often causes  
1
Introduction1  
pollution to the soil, groundwater and surface water (4). Leachate  
enters the surroundings from the bottom of the landfill through  
unsaturated soil stratum and flows to the groundwater and  
eventually to surface water via hydraulic connections. The  
discharge of treated or raw leachate from the treatment facility  
may also taint the environment and affect public health (5).  
1
.1 Landfill leachate  
Most of the developing countries are facing a major problem  
in terms of waste disposal. The disposal of municipal solid waste  
MSW) by dumping or burying it in a designated site is called  
(
landfilling. This, however, does not solve the problem as it  
basically transfers the MSW from urban areas to landfills (1). The  
disposal and improper management of MSW in landfills provide  
the opportunity for toxic substances in MSW to degrade into a  
liquid form called landfill leachate. Generally, landfills can be  
classified into five levels which are levels 0, I, II, III and IV. Table  
Table 1: Classes of landfill sites in Malaysia (6, 7).  
Level  
0
I
Type of Landfill  
Open Dumping  
Controlled tipping  
1
1
shows the classifications of landfill sites in Malaysia. Out of  
58 landfills nationwide, only 17 sites are categorised as sanitary  
II  
III  
IV  
Sanitary landfill with bund and daily cover  
Sanitary landfill with leachate recirculation system  
Sanitary landfill with leachate treatment facilities  
landfills whereas the rest of the sites are classified as unsanitary  
landfills. Level II is regarded as a semi-sanitary landfill due to the  
absence of leachate treatment facilities (2). The first two levels of  
landfills are the most worrisome as the numbers of these type of  
landfills are the highest in the country. These landfills are todays  
main cause of groundwater pollution as they do not have any layer  
of protection to keep the leachate from seeping into the ground  
Leachate is liquid rich in organic matter which can be  
distinguished by its colour, mainly brownish or viscous black.  
The quality of the leachate is influenced by several determinants  
such as age, precipitation, weather variation, waste type and  
Corresponding author: Aida Batrisyia Jasni, School of Civil Engineering, Faculty of Engineering, Universiti Teknologi Malaysia, Skudai,  
1310, Johor, Malaysia; E-mail: aida@civil.my.  
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Journal of Environmental Treatment Techniques  
2020, Volume 8, Issue 2, Pages: 567-572  
composition, depending on the lifestyle of the surrounding  
population and tip structure. Kurniawan et al. (8) mentioned that  
the composition of the landfill leachate depends greatly on the age  
of the leachate. As the harmful chemical substances found in  
leachate vary, they resulted in the increment of COD value,  
making them difficult to treat. The high COD value which not  
only contains organic matter but also inorganic matter requires a  
very intricate treatment system to treat the landfill leachate.  
and statistical tool, is applied for process modelling and  
optimisation studies (19). RSM has been extensively used in  
various studies as the design of experiment (DOE) and  
optimisation tools in anaerobic digestion (1822). There is no  
information available on literature to the extent of the author’s  
knowledge, on the treatment of landfill leachate using a stage  
granular anaerobic reactor. Therefore, this study used a unique  
four-stage granular multi-stage anaerobic reactor (GMSAR) for  
the treatment of landfill leachate, focusing on the COD removal  
and biogas yield. RSM was applied as a statistically based DOE  
to study the effects of COD influent, percentage of leachate and  
pH on the removal of COD and biogas yield. The optimal  
operating parameters for the COD removal and biogas yield were  
determined.  
1
.2 Stage anaerobic treatment  
Various landfill leachate treatment methods have been studied  
such as physical, chemical and biological which consist of aerobic  
and anaerobic treatments. Recent years have shown a grown  
interest in the area of anaerobic treatments (911). Anaerobic  
digestion is a process carried out by microorganisms that are able  
to live in an oxygen-deprived environment. The disintegration of  
organic substance happens in four stages: hydrolysis,  
acidogenesis, acetogenesis, and methanogenesis.  
2
Materials and Methods  
2
.1 Wastewater characteristics  
In terms of the feed substrate, this study used a mixture of meat  
In pursuance of optimising the environment in the reactor for  
the anaerobic bacteria and to boost the specific conversion  
reactions, physical separation is added in the sludge bed of a  
staged anaerobic treatment reactor. According to Lier et al. (12),  
studies have been conducted for the treatment of carbohydrate  
wastewater under mesophilic conditions by segregating the  
anaerobes involved in anaerobic digestion. The convenience of  
staging in this study is accredited to the high sludge yield of the  
carbohydrate fermenting bacteria. As the carbohydrate is  
fermented or pre-acidified in the first stage, a high volumetric  
fraction is passed on to the next stage for the methanogens to  
increase the methane yield of the anaerobic treatment system (12).  
The advantage of a staged anaerobic treatment system is also  
supported by Zhao et al. (13) who agreed that the anaerobic  
treatment is enhanced and needed only half of the amount of  
biomass in the conventional treatment system to double the  
activity of the anaerobes in the staged treatment system.  
Intanoo et al. (14) mentioned that the arrangement of a stage  
anaerobic reactor provides an ideal surrounding for the  
breakdown of intermediates such as propionate, which is  
beneficial both in mesophilic and thermophilic treatment  
conditions. However, the type and sequence of stages should be  
thoroughly studied in the preliminary stage to select the optimum  
arrangement for a specific application. Nasr et al. (15) applied a  
staged process in an up-flow anaerobic sludge bed (UASB)  
reactor which resulted in a more stable thermophilic treatment  
system. Very low volatile fatty acids concentration and low  
hydrogen partial pressure were obtained in the last compartments.  
The simplest arrangement of a staged anaerobic reactor can be  
achieved by arranging two or more up-flow reactor in series. In  
recent years, an integrated staged reactor comprising of vertically  
and horizontally oriented reactor has been introduced in order to  
enhance the plug flow pattern and spatial biomass separation  
and yeast extract for a start-up. In anaerobic treatment, the start-  
up of the reactor is an important phase for the stabilisation of the  
reactor. The substrate used for the reactor stabilisation is crucial  
in determining a successful start-up process. Various substrates  
have been used by researchers in order to smoothen and reduce  
the time taken for the start-up process. Most of the researchers  
used glucose as their substrate during the acclimatisation period.  
Though the glucose initially showed a good result in removing  
COD, the performance of the reactor deteriorated as the pH levels  
of glucose decreased abruptly (2325). There are several  
researchers who used a different substrate for the start-up process  
such as meat extract (26). The characteristics of the meat extract  
are suitable for the start-up process as it contains vitamins, fats,  
carbohydrates, and protein. However, the COD removal was only  
7
2% which was quite low (27). A study conducted by Zupancic  
et al. (28) revealed that yeast extract is a good co-substrate which  
enhances the biomethane production of wastewater. Therefore,  
this study used a mixture of meat and yeast extracts as substrates  
during the start-up and acclimatisation period. This combination  
of both meat and yeast extracts is theoretically able to increase the  
performance of the reactor during the start-up process in terms of  
COD removal and biogas yield. The feed used in this study is a  
matured landfill leachate supplied by Worldwide Landfill Sdn  
Bhd, Jeram, Selangor. The characteristics of the leachate are  
given in Table 2. The start-up of the GMSAR was accomplished  
using a mixture dilution of Bovril soup stock and yeast extract and  
the ingredients are shown in Table 3.  
Table 2: Characteristics of matured leachate  
Results  
8.0  
Units  
-
pH  
Temperature  
COD  
26.0  
2500  
486  
°C  
mg L-1  
(16,17).  
mg L-1  
mg L-1  
The efficiency of anaerobic treatment is further increased by  
5
BOD @ 20°C  
providing the optimal conditions for wastewater treatment.  
Nonetheless, the optimisation process is conducted in an obsolete  
way where a parameter is changed while the others are kept  
constant, which is too resource-consuming (18). To overcome this  
problem, response surface methodology (RSM), a mathematical  
Total Suspended Solids  
Ammoniacal Nitrogen  
220  
7
17  
mg L-1  
(AN)  
5
68