The Characteristics and Impacts of Landfill Leachate from Horotiu
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The characteristics and impacts of landfill leachate from Horotiu, New Zealand and Maseru, Lesotho: A comparative study A thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Environmental Science at The University of Waikato by Thabiso Mohobane 2008 Abstract Landfills are a potential pollution threat to both ground and surface water resources. This study focuses on two landfills, the Horotiu municipal waste landfill, near Hamilton, New Zealand, and the Maseru landfill in Lesotho. The Horotiu landfill is located less than 50 metres from the Waikato River and also sits on a shallow (< lm to water table) aquifer. In Lesotho, the Maseru landfill is 4 km from a river and 2 km from a water reservoir and rests on a huge aquifer. Over 5000 people depend on groundwater in the area between the landfill and the river. The objectives of my study were to: 1. compare and contrast conditions, management, and potential environmental impacts of the Horotiu and Maseru landfills; 2. evaluate the potential for groundwater contamination as the result of leachate migration; and 3. investigate the chemical characteristics of the landfill leachates and the impacts of the landfills on groundwater quality. The Horotiu study was based on the leachate and groundwater quality monitoring data obtained from the Hamilton City Council. Samples were collected every three months from 1991-2006 and analysed for about 30 chemical parameters. The data for the Maseru landfill consisted of groundwater quality collected by the author during July-September 2007 and borehole pumping data obtained from the Department of Water Affairs, in Lesotho. At Horotiu results indicate that the leachate had high concentrations of: NH4-N (630 mg/l), TOC (405 mg/l), BOD (126 mg/l), and COD (1289 mg/l), while heavy metals were in low concentrations (<0.1mg/l). Leachate quality was found to change with time and with rainfall. Groundwater samples obtained from the landfill boreholes indicated that the Horotiu landfill had an influence in the quality of groundwater. Groundwater at the down-slope side of the landfill had higher -2 concentrations of all chemical parameters, except for NO3-N, SO4 and Reactive P, than the groundwater on the upstream side. The mean groundwater quality at Horotiu was within New Zealand drinking water standards though some standards were exceeded by some individual samples. In the Maseru landfill, the borehole water had high concentrations of chemical parameters such as EC (1580 μS/cm) and Chloride (190 mg/l), compared to the national average of 250 μS/cm and 28 mg/l. The Maseru landfill groundwater quality was within the WHO drinking water standard for all analysed chemical constituents, except lead. Groundwater beneath both landfills was influenced by leachate but the impacts are currently not at an alarming stage, for analysed chemical parameters. At Maseru introduction of landfill linings has potential to reduce the effect of leachate on groundwater. ii Acknowledgments I would like to express my deepest gratitude to my principal supervisor Dr. Megan Balks for her wise and patient guidance from the beginning to the completion of this research. I would also like to thank Dr. David Campbell for his valuable contribution to this work. Thank you guys and God bless. My gratitude is also due to the following institutes: Hamilton City Council and Environment Waikato in New Zealand for providing information, opinion and reports for the Horotiu landfill; The Department of Water Affairs in Lesotho for the information and data on Maseru landfill; CRL Ltd, New Zealand for the educative trip around the Horotiu landfill and for the interview on leachate and groundwater monitoring. I give thanks also to my sponsor, NZAID and my employer, Lesotho Government for giving me the opportunity to undertake this study. Last but not least, heaps of thanks to my graceful wife, ‘Matobatsi and my magnificent son, Tobatsi for being part of my life and for supporting me during this nerve-racking period. iii TABLE OF CONTENTS Title page i Abstract ii Acknowledgments iii Table of Contents iv List of Figures viii List of Tables xi Chapter 1: Introduction 1.1 Background.............................................................................................. 1 1.2 Objectives ................................................................................................ 3 Chapter 2 Literature Review 2.1 Landfill location selection criterion...................................................... 4 2.2 Sanitary landfill design ............................................................................ 5 2.2.1 Landfill Liners ........................................................................ ……..5 2.2.2 Landfill Capping ............................................................................... 7 2.3 Landfill Leachate ................................................................................... 8 2.3.1 Leachate generation .......................................................................... 8 2.3.2 Leachate Plumes ............................................................................... 9 2.3.3 Leachate chemical characteristics................................................... 12 2.3.4 Factors affecting leachate composition........................................... 17 2.3.5 Attenuation of leachate concentration in groundwater systems ..... 22 2.3.6 Movement of leachate..................................................................... 24 2.4 Impacts of leachate ................................................................................ 27 2.4.1 Environmental impacts ................................................................... 27 2.4.2 Impacts on human health ................................................................ 29 2.4.3 Drinking water standards ................................................................ 30 2.4.4 Summary......................................................................................... 32 iv Chapter 3: Site Descriptions and Methods 3.1 Horotiu Landfill ..................................................................................... 35 3.1.1 Site history and operation ............................................................... 35 3.1.2 Geology and Hydrogeology............................................................ 39 3.1.3 Characteristics of Leachate at Horotiu............................................ 40 3.2 Maseru Landfill...................................................................................... 41 3.2.1 Landfill location and history........................................................... 41 3.2.2 Geology and hydrogeology............................................................. 42 3.3 Methods.................................................................................................. 44 3.3.1 Groundwater and leachate sampling at Horotiu landfill................. 44 3.3.2 Groundwater Sampling at Maseru landfill...................................... 49 3.3.3 Borehole pumping test .................................................................... 50 3.3.4 Chemical data presentation............................................................. 52 3.3.5 Statistical analyses .......................................................................... 53 Chapter 4: Horotiu landfill leachate quality 4.1Leachate Chemistry ................................................................................ 55 4.1.1 Introduction..................................................................................... 55 4.1.2 Leachate Composition .................................................................... 58 4.2 Temporal variations of leachate quality................................................. 60 4.2.1 Leachate pH .................................................................................... 60 4.2.2 Electrical conductivity and alkalinity ............................................. 63 4.2.3 Major Anions .................................................................................. 66 4.2.4 Major Cations.................................................................................. 66 4.2.5 Organic Content.............................................................................. 72 4.2.6 Heavy Metals .................................................................................. 75 4.3 Variation of leachate with amounts of rainfall ...................................... 79 4.3.1 Introduction..................................................................................... 79 4.3.2 Rainfall amounts and leachate quality ............................................ 79 4.4 Discussion.............................................................................................