Water and Environmental Engineering, Department of Chemical Engineering, Lund University

Transcription

1 New leachate treatment methods Jude Ifeanyichukwu Madu Water and Environmental Engineering, Department of Chemical Engineering, Lund University P.O. Box 4, SE00, Lund, Sweden, Phone: , Abstract Leachate, an ecosystem pollutant has the potential to cause harm to human, plant and animal population. This work searched for and compared leachate treatment methods in terms of efficiency in the treatment of young, medium and old leachate as well as in term of space utilisation, skill personnel requirement, installation and operational cost. It looked out for some full scale leachate treatment plants around the world and presented them together with when they started operation, their capacity, country of location, removed substances from treated leachate and treatment processes applied. Twenty different principle techniques for treatment of landfill leachate and twentyseven full scale operational leachate treatment plants using one, two or three of the techniques was found. It was uncovered that there are tested, reliable and consistent conventional and new technologies for leachate treatment and that the sequencing batch reactor () technology for primary biological treatment of landfill leachate is the most reliable and robust strategy. Keywords: Landfill, leachate, physicochemical, chemical oxygen demand, ammoniumn, Introduction full scale installation, discharge consent. The generation of solid waste is inevitable in the day to day activity of humans and animals. As humans strive to keep the environment clean to avoid infectious diseases from bacteria and viruses by dumping solid waste in landfills, they create yet another environmental problem. Decomposing waste within the landfills generates greenhouse gases (methane and carbon dioxide) as well as the production of a liquid known as leachate when precipitation infiltrates. Leachate is highly polluted due to high content of ammonium ions and organic compounds (Ulrika Welander, 998). When leachate move downwards from landfill into groundwater table as a result of infiltrated precipitation, groundwater gets contaminated likewise if the waste is buried below the water table; groundwater becomes contaminated after leaching compounds from it (C.W Fetter, 00). Since ground water and surface water are the source of our potable water, they should be protected from such pollutants otherwise the cost of treating drinking water will rise and the life of biodiversity in surface water bodies will be endangered. Since landfills and leachate production cannot be completely avoided, the only thing to do is to as much as possible reduce leachate production and treat the generated ones to eliminate or reduce the level of contamination in them to discharge consent levels before releasing to the environment (receiving water bodies). Leachate are often discharged to local wastewater treatment plant in order to obtain sufficient treatment though it may be advantageous from an economic point of view to have final treatment of

2 leachate on site. During the recent years many new methods physicochemical, biological and combine biological with physicochemical have been proposed and tested. Materials and method Articles, journals and books were studied to extract information on leachate treatment methods and operational full scale installation. The leachate treatment methods were compared in terms of treatment efficiency, space utilization, installation and operational cost. Some details of the full scale treatment plants such as year operation began, capacity of plant, country of location, substances removed and treatment processes applied were also searched for and listed. Table is a comparison of the techniques in terms of treatment efficiency, space utilization, installation and operational cost while Table is the full scale leachate treatment plants, year when they started operation, their capacity, country of location, removed substances from treated leachate and treatment processes applied. Table : Comparison base on treatment efficiency, space utilization, installation and operational cost. Treatment process Biological Young leachate Medium leachate Old leachate Space utilization Installation and operational cost Requiring less skilled personnel Activated sludge RBC Reed beds BAF Lagoons UASB AF MBBR MBR Physicochemical Coag. & flocculation Precipitation Adsorption Flotation Chem. Oxidation Ammonia stripping Membrane process Microfiltration Ultrafiltration Nanofiltration Reverse Osmosis

3 Table : The leachate treatment plants, year operation began, capacity, country of location, removed substances from treated leachate and treatment processes applied. Name of plant Fågelmyran LTP Gärstad LTP Izola LTP Niemark LTP Mechernich LTP Sonzay LTP Tondela LTP Rebat LTP Arthurstown LTP Bryn posteg LTP Compton bassett LTP Buckden LTP Greengairs LTP Summerston LTP Efford LTP Llanddulas LTP Arpley LTP Pitsea LTP Harewood whin LTP Hempsted LTP Year operation began Capacity 350 m 3 /d 65 m 3 /d 7 m 3 /d 40 m 3 /d 0 m 3 /d 300 m 3 /d 50 m3/d 00 m 3 /d 00 m 3 /d 00 m 3 /d 50 m 3 /d 50 m 3 /d 450 m 3 /d 00 m 3 /d 80 m 3 /d Country Of location Sweden Sweden Slovania Germany Germany France Portugal Portugal Ireland Substances removed BOD, COD, nitrogen, phosphorus BOD,COD,, metals and soluble salts COD, BOD, AOX, and Cl BOD,COD,, metals and salts BOD,COD,, metals and soluble salts BOD,COD,, metals and soluble salts, iron, manganese, zinc SS, BOD,COD, iron, calcium, and zinc BOD,COD,, chloride BOD,COD,, iron, sodium and chloride. TOC, BOD, COD and iron COD, BOD, TOC,, chloride, sodium, magnesium, potassium, calcium and iron BOD,COD,, Treatment Process applied Lagoons Lagoon and reed bed, RO Activated sludge, BC and RO MBR, RO Lagoon and RO Lagoon and RO Lagoon Lagoon, Ozonation, Reed bed Lagoon, reed bed Lagoon, reed bed, DAF and Reed bed RBC Lagoon and lagoon 3

4 Fiskerton LTP Gairloch LTP Brookhill LTP Mariannhill LTP Vissershok LTP Guangzhou xingfeng LTP Bukit tagar LTP m 3 /d 40 m 3 /d 50 m 3 /d 30 m 3 /d 80 m 3 /d 000 m 3 /d S. Africa S. Africa Hong Kong Malaysia and iron COD, BOD, TOC sodium, magnesium, potassium, calcium, iron and zinc. COD, TOC, NH 4 N, chloride, sodium, magnesium, calcium and iron, and spraying effluent over area of peat, reed bed, reed bed UASB,, CMF, RO Lagoon, DAF, Reed bed Results and discussion Finding out number of techniques that can be good for treatment of young, medium and old leachate as well as number of techniques that do not occupy much space, are less expensive in installation and operational cost and requiring less skilled personnel. Figure is a graph of number of treatment techniques that are good against leachate treatment factors of leachate being young, medium and old as well as a leachate treatment technique requiring little space, less installation, operational cost and skilled personnel.. of good techniques Young leachate Medium leachate Old leachate Space utilization Cost Less of skill personnel. Treatment factors Figure : A graph of number of treatment techniques that are good against leachate treatment factors of leachate being young, medium and old as well as a leachate treatment technique requiring little space, less installation, operational cost and skilled personnel. From the figure it is observed that there is wide range of choice to make in terms of treatment technique if the leachate to be treated is a young one. The figure shows that up to eleven different 4

5 techniques are good for treatment of young leachate. It also shows that eleven different techniques can be applied in sites where there is insufficient space. Finally, it reveals that up to ten of the techniques can run under the watchful eyes of less skill personnel. The plant distribution Figure is a pie chart representation of country of location of the treatment plants. Fourteen of the plants which accounts for over 50% of the number found are in the United Kingdom. Sweden Slovania Germany France Portugal Ireland South Africa 4 Hong kong Malaysia Figure : Pie chart representing the number of treatment plants found in different countries Most applied technique The most applied treatment technique or rather the most popular technique can be seen in figure 3 which is a graph of number of plants using specific treatment technique against the treatment techniques.. of plant using method Treatment method Figure 3: A graph of number of plants using specific treatment technique 5

6 From the graph it is seen that the treatment technique is the most applied. Fifteen out of the twentyseven treatment plants found made use of the process. This represents 55.5% of the plants found. It must be as a result of the advantages which it has over other techniques that made it to be more popular. In s energy is optimised through control of aeration rate and duration. There is no secondary clarifier, so its cost is eliminated. There is flexibility in adjusting reaction time and tank volume to meet variable loading and it do not occupy as much space as the activated sludge reactor. Again, a study by Dorota K. Et al, 006 on BOD 5 and COD removal and sludge production in working with or without anoxic phase showed high efficiency of s in the removal of organics from leachate. BOD 5 removal was over 98% with or without the anoxic phase while COD removal varied from 83.% to 76.7% on shortening the hydraulic retention time (HRT) from to days with an anoxic phase of 3hrs and 79.6% to 75.7% without an anoxic phase. Figure 3 also showed wide application of the lagoon, reed bed and reverse osmosis technique after the technique. Lagoon processes are technically and economically viable at full scale while the reed bed and the reverse osmosis are very good secondary polishing processes for the biological pretreatments. Conclusion From the results the following conclusion can be drawn: There are tested, reliable and consistent conventional and new technologies for leachate treatment There are up to eleven different techniques that are good for treatment of young leachate. Also there are eleven different techniques that can be manned by less skill personnel during operation The use of the sequencing batch reactor () technology for primary biological treatment of landfill leachate has proved to be a reliable and robust strategy. Leachate treatment plants are most abundant in the United Kingdom. List of abbreviations BODBiochemical oxygen demand COD Chemical oxygen demand TOC Total organic carbon Ammonium nitrogen RBC Rotating biological contactor Sequencing batch reactor BAF Biological aerated filter UASBUp flow anaerobic sludge blanket AF Anaerobic filter MBBR Moving bed bio film reactor MBR Membrane bioreactor 6

7 Acknowledgement I would like to thank the Swedish Government for the tuition free master programme which I did. I also want to thank my supervisor, Professor Jes la Cour Jansen and my examiner Associate Professor Karin Jönsson at Lund University for their support and good advises during this research work. References. Welander U. Characterization and treatment of Municipal landfill leachate. 998, page 7.. Fetter C. W. Applied Hydrogeology. 00, 4 th Edition, page Dorata K, Klimiuk E and Drzewicki A. BOD5 and COD removal and sludge production in working with or without anoxic phase. Bioresources technology, volume 98, issue 7, pages 46 43, 006 7

8 8