Leachate generation is a major problem for municipal solid waste (MSW) landfills. Leachate can be defined as a liquid that passes through a landfill and has extracted dissolved and suspended matter from it.
Leachate generated in municipal landfill contains large amounts of organic including some hazardous organic chemicals and inorganic contaminants. It causes significant threat to surface water and groundwater if not properly treat. The removal of the contaminants from leachate is the prerequisite before discharging the leachates into natural waters.
Generally, leachate is characterized by high values of COD, pH, ammonia nitrogen and heavy metals, as well as strong colour and bad odour. At the same time, the characteristics of the leachate also vary about its composition and volume, and biodegradable matter present in the leachate against time. All these factors make leachate treatment difficult and complicated and compulsory to treat before being discharge into water stream.
Malaysia Discharge Standard
The discharge standard of treated leachate shall comply with the regulation established by the department of environment in the Environmental Quality (Control of Pollution from Solid Waste Transfer Station and Landfill) Regulations 2009.
Characteristics of Leachate
The quality and quantity of leachate is highly variable and is directly related to fluctuations of rainfall amount, composition/ characteristics of the waste, age, and landfill operational patterns. Landfill leachate composition varies greatly depending on the season, leachate collection system and landfill age.
A site visit has been conducted to observe the existing treatment process of the leachate as the picture below:
Figure 1: Observation of treated leachate
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Figure 2: Jar Test on-site by using BIO-FDA
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The existing treatment system using chemical treatment where Ferric Chloride is used as coagulant and polymer is used as the flocculant for the pre-treatment process. The problem arising with the existing treatment is that the BOD content and ammoniacal nitrogen content cannot be treated up to discharge standard. Figure 2: Jar Test on-site by using BIO-DFA Figure 1: Observation of treated leachate Sample of leachate collected which is the pure, raw and undiluted leachate. The sample has been tested to undergo treatment by using BIO-DFA. After being treated by using BIO-DFA, the sample was then going through ammonia stripping process before the sample is ready to be analysed. The picture shows the jar test done on the concentrated leachate:
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Figure 3: Test Conducted on the Concentrated Leachate
a. Raw Concentrated Leachate
b. BIO-DFA Treated – Concentrated Leachate
Treatment explanation conclusion:
Based on jar test conducted on the sample and the results obtained, it shows that BIO-DFA are capable in treating the leachate at higher efficiency compared to chemical conventional method. The raw leachate results analysed shows high concentration of COD which is 5,200 ppm and the ammoniacal nitrogen at the concentration of 1,295 ppm. This is due to the long storage time which caused the leachate to be worse and contain high concentration of ammoniacal nitrogen. If the fresh leachate is directly treated without any storage time, the leachate will be easier to be treated and the concentration of ammoniacal nitrogen will be much less.
By incorporating proper treatment system, it is believed that BIO-DFA are capable in treating the leachate generated. Slight modification is required on the existing treatment system in order to use BIO-DFA as the treatment agent.
Proposed Treatment Technology
In view to solve the problem arising from the treatment process, the solution proposed is by replacing the existing current chemical to BIO-DFA. As BIO-DFA treatment shows faster treatment reaction, it is capable in treating the leachate by using the existing treatment system. A brief introduction of BIO-DFA is explained in this section.
Introduction To BIO-DFA
Since BIO-DFA is a new coagulant-flocculant used to replaced alum/pac/polymer function. BIODFA is composed of mineral-based ingredients and functioning as the coagulant and flocculant in the wastewater treatment. BIO-DFA is a product of research where the aim is to improve the current usage of chemical used in the wastewater treatment industry and it is successfully achieved throughout the effective composition, improving inventions of the same field of technology to reduce treatment costs, reduce pH adjustment, minimize the amount of sludge, increase contact and binding efficiency, and reduce side-effects from the use of chemicals to both workers and consumers. This composition differs from the existing chemicals used in that the composition is of natural minerals freely available from nature and is organic in nature.
BIO-DFA shows no problem in treating high temperature wastewater as well as high salt content of wastewater which differ from the existing chemicals used for wastewater treatment. BIO-DFA easily encapsulates various contaminants inside the wastewater. BIO-DFA removes more oil, grease and heavy metals compared to other chemicals, separates the contaminants quickly from the waste effluent, simplifies the operation by using just one product, and reduces overall operating costs. In short, BIO-DFA is 3E – Efficient, Effective, Economic.
Figure 4: Physical Form of BIO-DFA
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Proposed Modification:
Based on the discussion with LTP operator person-in-charge, the system aimed to treat the raw concentrated leachate. The treatment will be involved two stage of BIO-DFA treatment system. The first treatment stage will be using the existing system while a set of new system will be needed for the second treatment. The modification proposed for the treatment system are as follow:
- Equalization Tank
Leachate from the collection pond will first pumped into the Equalization Tank. The modification involved here is that the equalization tank will also serve as pH Adjustment
Tank. Addition of acid and alkali will be done here before pumped into Pre-treatment tank 1 which will now serve as Reaction Tank. A set of pH Controller will be installed to monitor the pH of the leachate. One set of motor completed with mixer will be installed here to ensure thorough mixing between the leachate and chemical.
- Pre-Treatment Tank 1
The existing pre-treatment tank will now be used as ‘Reaction Tank’. The modification involved here us addition of motor completed with stirrer. Another set of pH controller will be installed to monitor the complete treatment reaction. A set of powder dosing equipment will installed on top of the treatment reaction to dose BIO-DFA for treatment purpose.
- Pre-Treatment Tank 2
In the pre-treatment tank 2 which is now called as Flocculation Tank and the modification involved only the addition of motor completed with stirrer and the framework. The partial treated leachate will flow into the flocculation tank and slow speed mixing is provided to form larger and bigger flocs. The flocs formed will be sedimented at the bottom of the tank whereas the treated water will flow out on top of the tank into the Secondary BIO-DFA Treatment stage.
Secondary BIO-DFA Treatment Stage
The second stage of BIO-DFA treatment will consists of 3 sequence tank, pH adjustment tank,reaction tank with BIO-DFA dosing system and flocculation tank. The treated water from the flocculation tank will flow into the existing treatment process.
Conclusion
BIO-DFA application in the treatment of leachate is not only capable in reducing COD, BOD, aluminium, colour, BIO-DFA is also capable in remove heavy metal concentration inside the wastewater. The treatment on the laboratory scale indicates that BIO-DFA are capable in treating the leachate.
The technology proposed shows the solution towards the treatment of variety of wastewater including leachate. Proper design of treatment system will improve the treatment efficiency and will produce treated water that can comply with the discharge standard as stipulated in Environmental Quality Act (EQA) 1974.
