1 Kwame Nkrumah University of Science and Technology, Kumasi College of Science Faculty of Biosciences Department of Theoretical
Total Page：16
File Type：pdf, Size：1020Kb
KWAME NKRUMAH UNIVERSITY OF SCIENCE AND TECHNOLOGY, KUMASI COLLEGE OF SCIENCE FACULTY OF BIOSCIENCES DEPARTMENT OF THEORETICAL AND APPLIED BIOLOGY BACTERIAL CONTAMINATION OF LETTUCE AND ASSOCIATED RISK FACTORS AT PRODUCTION SITES, MARKETS, AND STREET FOOD RESTAURANTS IN URBAN AND PERI-URBAN KUMASI. A THESIS PRESENTED TO THE DEPARTMENT OF THEORETICAL AND APPLIED BIOLOGY, COLLEGE OF SCIENCE, KWAME NKRUMAH UNIVERSITY OF SCIENCE AND TECHNOLOGY, IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE (ENVIRONMENTAL SCIENCE) BY FREDRICK AMPONSAH-DOKU SEPTEMBER 2006 1 DECLARATION I hereby declare that this thesis presented to the Department of Theoretical and Applied Biology in partial fulfillment for the award of MSc. Degree, is a true account of my own work except for the references that have been duly acknowledged. Signature…………………………… Date…………………………. NAME: AMPONSAH-DOKU FREDRICK (STUDENT) Signature…………………………….. Date…………………………… NAME: DR. OBIRI-DANSO K. (SUPERVISOR) 2 DEDICATION To my late father Mr. J. C. Atta-Doku 3 ACKNOWLEDGEMENT I wish to acknowledge the time, energy and resources sacrificed by my supervisor, Dr. K. Obiri- Danso of the Department of theoretical and Applied Biology. My gratitude also goes to Prof. R. C. Abaido of the Department of theoretical and Applied Biology and all the Lecturers of the Department, not forgetting Mr. Osei-Tutu, Auntie Anita, Auntie Eunice and Jimmy. I am also grateful to the Challenge Program for Water and Food (CPWF) for sponsoring this project and all staff of IWMI, Kumasi office. My sincere and profound gratitude also goes to my family, Miss Betty Agyenim-Boateng and family, and Mr. Affum-Baffoe of Forestry Commission for their motivation, pieces of advice, patience and sacrifices in making this study a reality. To my friends and course mates especially Mr. Maxwell Akple, Mr Amo Sarpong and Miss Linda Andoh for their special assistance. Finally, to the Almighty God for seeing me through this study and for His abundant grace upon us. 4 TABLE OF CONTENT Declaration ii Dedication iii Acknowledgement iv List of Tables ix List of Figures ix List of Plates x Abstract xi CHAPTER ONE 1.0 INTRODUCTION 9 1.1 Background 1 1.2 Problem Statement 2 1.3 Research Questions 4 1.4 Objectives of Study 4 1.4.1 General Objectives 4 1.4.2 Specific Objectives 4 CHAPTER TWO 2.0 LITRETURE REVIEW 6 2.1 CONCEPTS AND DEFINITIONS 6 2.1.1 Urban and Peri-Urban Agriculture 6 2.1.2 Wastewater 6 2.1.3 Marginal Quality Water 7 2.1.4 Typology of Wastewater use for Urban and Peri-Urban Agriculture 7 2.1.5 Wastewater Treatments 8 2.1.6 Microbial Indicators 9 2.2 Wastewater Use for Urban and Peri-Urban Agriculture 10 2.2.1 Wastewater Irrigation in Kumasi 11 2.3 Pathogenic Micro organisms in Waste Water 12 2.4 Contamination of Vegetables 13 2.4.1 Pre-harvest 14 2.4.2 Harvest 16 2.4.3 Post Harvest Sources 16 2.5 Washing and Decontamination 17 2.6 Effects of Wastewater Irrigation 18 2.6.1 Health Risk 19 2.7 Coliform Identification Schemes 25 CHAPTER THREE 3.0 STUDY AREA AND METHODOLOGY 32 3.1 Study Area 29 3.2 Research Methods 31 3.2.1 Sampling Sites 31 3.2.2.1 Production sites 32 3.2.2.2 Market sites 35 3.2.2.3 Street food vendors 35 3.2.3 Sampling 36 3.2.3.1 Production site 36 3.2.3.2 Market site 37 3.2.3.3 Street food vendors 38 5 3.2.4 Enumeration of Thermotolerant Coliforms 38 3.2.5 Enumeration of Enterococci 39 3.2.6 Enumeration of Salmonella 39 3.2.7 Health Risk Surveys 40 3.3 Statistical Analysis 41 CHAPTER FOUR 4.0 RESULTS 42 4.1 Bacterial Indicator Numbers at Production Site 42 4.2 Bacterial Indicator Numbers at Market Site 46 4.3 Bacterial Indicator Numbers at Street Food Vendor Sites 49 4.4 Bacterial Indicator Numbers along the Producer-Consumers Chain 49 4.5 Health Risk Assessment 50 4.5.1 Production Site 50 4.5.2 Market Site 52 4.5.3 Street Food Vendor Sites 52 CHAPTER FIVE 5.0 DICUSSION, CONCLUSION AND RECOMMENDATION 54 5.1 Discussion 54 5.1.1 Contamination at Production (Farm) Sites 54 5.1.2 Contamination at Market Sites 56 5.1.3 Contamination at Street Food Vendor Sites 57 5.1.4 Health Risk 58 5.2 Conclusion 59 5.3 Recommendations 60 REFERENCES 61 APPENDICES 73 LIST OF TABLES Table 2.1 Definitions for indicator and index micro-organisms of public health concern. 9 Table 2.2: Possible Levels of Pathogens in Wastewater. 12 Table. 2.3: Sources of pathogenic microorganisms on fresh fruits and vegetables. 14 Table 2.4: Health risk from use of wastewater in agriculture. 20 Table 2.5: Recommended microbiological quality guidelines for treated wastewater used for crop irrigation. 21 Table 2.6: Summary of health risks to exposed groups associated with the use of wastewater in irrigation. 22 Table 4.1: Bacterial counts (geometric means and ranges) on lettuce leaves and in irrigation water on vegetable production (farm) sites within urban and peri urban Kumasi. 42 Table 4.2: Bacterial counts (geometric means and ranges) in lettuce and refreshing water from three selected market sites within urban Kumasi. 46 Table 4.3: Bacterial counts (geometric means and ranges) from selected Street Food Vendor sites in Urban Kumasi. 49 6 LIST OF FIGURES Figure 3.2 Map showing Urban Farm sites in Kumasi and the selected farms for the study. 30 Figure 3.1 Map showing Kumasi in relation to the rest of Ghana. 31 Figure 4.1: Thermotolerant coliform Numbers in Lettuce and Irrigation Water on the three Farm sites. 45 Figure 4.2: Enterococci Numbers in Lettuce and Irrigation water on Farm. 45 Figure 4.3: Thermotolerant coliform Numbers in Lettuce Leaves and Refreshing Water at Three Market sites in Urban Kumasi. 48 Figure 4.4: Enterococci Numbers in Lettuce Leaves and Refreshing Water at three Market sites in Urban Kumasi. 48 Figure 4.5: Contamination Levels on Lettuce leaves along the Production-Consumer Chain. 50 Figure 4.6: Types of Disinfectants Used By Street Food Vendors for Washing Lettuce 53 LIST OF PLATES Plate 1: A section of the Gyenyase farm site 32 Plate 2: A portion of the Kakari site with some areas developed for residential use 33 Plate 3: A section of the Deduako farm site 35 Plate 4: Sampling of lettuce from a Bed at Gyenyase Farm (Site 1) 37 Plate 5: A Section of Farmers during the Focus Group Discussion 40 Plate 6: A barefooted Farmer drawing water from a Shallow Well 51 7 ABSTRACT There is increasing evidence that developing countries urban grown vegetables can be contaminated with pathogenic microorganisms. This is particularly true when wastewater is used in irrigation. The microbiological quality of wastewater grown lettuce on farms, markets and at street food vendor sites were evaluated for thermotolerant coliforms, enterococci and Salmonella using standard methods. Farm irrigation water and market refreshing water samples were also analysed. Thermotolerant coliforms on lettuce varied from 3.9×103 to 9.3×108 on farm, 4.0×103 to 2.3×108 on market and 2.30 x 106 to 2.40 x 109 on street foods. Bacterial numbers on farm lettuce were higher compared to the irrigation water (1.5×103 to 4.3×106) used on the farms. However, bacterial numbers in market refreshing water (5.0×104 to 4.3×1010) were higher compared to the market lettuce leaves. Enterococci numbers on lettuce were lower ranging from 3.9×101 to 2.4×108 on farm, 6.0×101 to 9.0×104 on market and 1.80 x 105 to 2.50 x 106 on street foods. Salmonella numbers in street foods ranged from 1.5×104 to 9.3×105. In general, bacterial numbers increased by more than 6% from the farms to the street foods. Bacterial counts on farm lettuce and irrigation water, market lettuce and refreshing water and street foods all exceeded the recommended WHO and ICMSF standards of 103. Wastewater use on farms and refreshing water in markets could be the main contributors to lettuce contamination and that education on use of salt, vinegar and potassium permanganate use in washing before use could help reduce the risk. 8 CHAPTER ONE 1.0 INTRODUCTION 1.1 Background The growing demand for fresh and perishable agricultural produce like lettuce in the major urban centres is driving the development of peri-urban agriculture. This demand is not seasonal, necessitating year-round production, which is heavily dependent on irrigation with the main source of water being wastewater. Although wastewater dominated open-space urban farming does not contribute significantly to food security in Ghanaian cities, it makes very significant contributions to the supply of specific food items particularly perishable vegetables like lettuce, which have now become an important part of urban diet. In Kumasi, 90% of all lettuce and spring onions consumed are produced from open-space vegetable farming in the city (Cofie et al., 2001). Population growth coupled with urbanization in many cities in developing countries has resulted in increased demand for resources such as land and water. In assessing water for irrigation, urban farmers have tapped into wastewater, which is a readily available resource in cities, has few costs associated with its use and can actually increase harvests and production, thus increasing income (Kilelu, 2004). Using treated wastewater for Urban Agriculture (UA), provides a means through which wastewater can safely be reused and managed.