KWAME NKRUMAH UNIVERSITY OF SCIENCE AND TECHNOLOGY, …

[Pages:93]KWAME NKRUMAH UNIVERSITY OF SCIENCE AND TECHNOLOGY, KUMASI, GHANA

Performance Assessment of a Two Stage Aerobic Rotating Biological Contactor (RBC) in the Treatment of Cocoa Processing Wastewater: A Case Study of Cargill Cocoa Processing Company-Ghana By Michael Dornu Amewuda (BSc. Civil Engineering)

A Thesis Submitted to the Department of Civil Engineering, College of Engineering

In partial fulfillment of the requirements for the degree of MASTER OF SCIENCE In

Water Supply and Environmental Sanitation

July 2015

i

CERTIFICATION I hereby declare that this thesis is my own work towards the Master of Science (MSc) degree in Water Supply and Environmental Sanitation and that, to the best of my knowledge, it contains no material previously published by another person nor material which has been accepted for the award of any other degree of the University, except where due acknowledgement has been made in the text.

Amewuda Michael Dornu (PG 9727313)

Certified by: Dr. Richard Buamah (Principal Supervisor)

.......................... Signature

.............................. Date

............................. Signature

................................ Date

Prof. Y.A. Tuffuor (Head of Department)

...................... ..... Signature

.................... ......... Date

ii

ACKNOWLEDGEMENTS I am grateful to the Almighty God for his constant blessings, guidance, protection and strength during my entire MSc. studies. My greatest appreciation goes to my supervisor Dr. Richard Buamah for his constant support, direction and guidance through my research.

I would like to extend my gratitude to the Bill & Melinda Gates Foundation (BMGF) for making this project possible and providing full financial support throughout my 2 years of study. I would also like to thank everyone in the Water Resources and Environmental Sanitation Programme of the Civil Engineering Department of the Kwame Nkrumah University of Science and Technology for all of their assistance.

Special appreciation to UNESCO-IHE, Institute for Water Education, for offering an exceptional opportunity to experience world class post graduate education. I would like to extend my special thanks to the technical team of Cargill, especially to Mr. Richard Nkrumah, Mr. Seth Awudi and Mr. Solomon Ackummey for their time and support.

I am thankful to the Heads of the Environmental Chemistry and the Bacteriological Departments of Water Research Institute (WRI), CSIR for permitting me to use their laboratories. I am particularly grateful to Mr. Emmanuel Adu Ofori and his team of Laboratory workers for assisting me in performing the laboratory tests of the parameters for this research.

Hearty cheers to all my course mates. Through all the late nights, stressful examinations and research, we finally made it to the end. To my entire family and friends, thank you for the never ending supply of prayers, faith, love, and moral support. Finally, thank you simply does not express my appreciation to my wife, Mrs. Barbara Mensah-Amewuda for her constant love and support throughout the entire duration of my studies. I love you.

iii

ABSTRACT In Ghana, more than 70% of the industries discharge their effluents into receiving water bodies untreated or partially treated. In view of this development, an assessment of the performance of Cargill Cocoa's two-stage aerobic Rotating Biological Contactor (RBC) for the secondary treatment of its process wastewater was performed. The study examined the effects of the disc rotational speed and the hydraulic retention time (HRT) on the performance of the RBC. Results from the study revealed that the influent wastewater to the RBC was of high strength with a mean COD/BOD5 ratio of 5:1. Changing of the disc rotational speeds of the RBC from 2rpm to 6rpm resulted in maximum COD removal of 69% at 4rpm. The maximum TSS removal achieved was 40% at 4rpm disc speed. The results of varying the HRT from 6hrs to 24hrs at the optimum disc speed of 4rpm resulted in a maximum COD removal of 27% at 12hrs HRT. This was same for the BOD5 removal. The maximum TSS removal of 80% was achieved at 12hrs HRT. The results from the study showed that none of the RBC disc speeds and HRT's was able to attenuate defined parameters to the approved Ghana EPA guidelines. The study concluded that a tertiary treatment step be introduced to the wastewater treatment scheme if the Ghana EPA effluent guidelines for discharge is to be met. It was recommended that further studies be carried out on the optimum organic loading rate at which the RBC should be operated.

iv

TABLE OF CONTENTS

CERTIFICATION............................................................................................................. ii ACKNOWLEDGEMENTS ............................................................................................. iii ABSTRACT ..................................................................................................................... iv LIST OF TABLES .......................................................................................................... vii LIST OF FIGURES......................................................................................................... vii LIST OF PLATES.......................................................................................................... viii LIST OF ACRONYMS AND ABBREVIATIONS......................................................... ix CHAPTER 1: INTRODUCTION ..................................................................................... 1

1.1 Background ..................................................................................................... 1 1.2 Problem Statement ................................................................................................. 3 1.3 Research Questions ................................................................................................ 4

1.4 Research Aim and Objectives ......................................................................... 4 1.4.1 Goal of Research............................................................................................. 4

1.4.2 Research Objectives .................................................................................... 5 1.5 Justification ..................................................................................................... 5 1.6 Scope of Study ................................................................................................ 6 1.7 Limitations of the Study.................................................................................. 6 1.8 Ethical Considerations .................................................................................... 7 1.9 Organisation of the Study ............................................................................... 7 CHAPTER 2: LITERATURE REVIEW .......................................................................... 8 2.1 Theory of Wastewater..................................................................................... 8

2.1.1 Municipal Wastewater................................................................................. 8 2.1.2 Storm Water ................................................................................................ 8 2.1.3 Domestic Wastewater.................................................................................. 8 2.2 Industrial Wastewater ..................................................................................... 9 2.3 Industrial Wastewater Quality Characteristics.............................................. 11 2.3.1 Physical Parameters........................................................................................ 11 2.3.2 Chemical Characteristics................................................................................ 14 2.3.3 Biological Characteristics .............................................................................. 18 2.4 Treatment of Wastewater .............................................................................. 18 2.5 Wastewater Management Procedures ........................................................... 19 2.5.1 Equalization............................................................................................... 19

v

2.5.2 Neutralization (pH Correction) ................................................................. 20 2.6 Methods for Treating Industrial Wastewater ................................................ 21 2.7 Development of the RBC Concept ............................................................... 23 2.8 National Effluent Quality Guidelines ........................................................... 26 CHAPTER 3: RESEARCH METHODOLOGY ............................................................ 27 3.1 Study Site Description .................................................................................. 27

3.1.2 The Unit Processes of the ETP....................................................................... 28 3.2 Experimental Setup Description ................................................................... 30 3.3 Procedures for Laboratory Analysis ............................................................. 32 3.4 Data Quality Assuarance and Ethical Considerations .................................. 34 CHAPTER 4: RESULTS AND DISCUSSION .............................................................. 35 4.1 Characterization of Influent Wastewater ...................................................... 35

4.1.1 Characteristics of Influent Wastewater to the ETP ........................................ 35 4.1.2 Characteristics of Influent Wastewater to the RBC .................................. 37 4.2 Performance of the RBC at Varying Disc Rotational Speeds....................... 39 4.2.1 COD ............................................................................................................... 39 4.2.2 BOD5 ......................................................................................................... 41 4.2.3 TSS ................................................................................................................. 43 4.3 Performance of the RBC at Varying Hydraulic Retention Times ................ 45 4.3.1 COD .......................................................................................................... 45 4.3.2 BOD5 ......................................................................................................... 47 4.3.3 TSS ............................................................................................................ 49 CHAPTER 5: CONCLUSIONS AND RECOMMENDATIONS .................................. 51 5.1 Conclusions................................................................................................... 51 5.2 Recommendations......................................................................................... 53 APPENDIX ..................................................................................................................... 62 Appendix I: Dimensions of the ETP Unit Processes..........................................62

Appendix II: Results from sampling procedure............................................63-67

Appendix III: Experimental procedure......................................................68-79

Appendix IV: Some pictures of the ETP at Cargill during the sampling process.....80-83

vi

LIST OF TABLES Table 2.1: Contaminants present in Industrial effluents....................................9-10 Table 2.2: Ghana EPA guideline values for the discharge into receiving water bodies................................................................................................26 Table 3.1: Sampling and analytical schedule...................................................32 Table 3.2: Summary of materials, reagents and analytical methods........................33 Table 4.1: Influent characteristics of the cocoa processing wastewater....................35

LIST OF FIGURES Figure 2.1: Online and offline flow equalization................................................20 Figure 2.2: Biological wastewater treatment methods........................................22 Figure 3.1: General wastewater treatment scheme.............................................27 Figure 3.2: Process flow diagram showing sampling points..................................30 Figure 4.1: Graph of COD concentration against disc rotational speed.....................39 Figure 4.2: Graph of percentage COD removal against disc rotational speed..............40 Figure 4.3: Graph of BOD5 concentration against disc rotational speed....................41 Figure 4.4: Graph of percentage BOD5 removal against disc rotational speed............42 Figure 4.5: Graph of TSS concentration against disc rotational speed......................43 Figure 4.6: Graph of percentage TSS removal against disc rotational speed..............44 Figure 4.7: Graph of COD concentration against HRT........................................46 Figure 4.8: Graph of percentage COD removal against HRT.................................47 Figure 4.9: Graph of BOD5 concentration against HRT......................................48 Figure 4.10: Graph of percentage BOD5 removal against HRT..............................49

vii

Figure 4.11: Graph of TSS concentration against HRT.......................................50 Figure 4.12: Graph of percentage TSS removal against HRT...............................50

LIST OF PLATES Plate 1: Floatation tank............................................................................80 Plate 2: Mixing tank with stirrer.................................................................80 Plate 3: Primary settler with effluent weir......................................................81 Plate 4: Two stage aerobic RBC.................................................................81 Plate 5: RBC with lamella settler................................................................82 Plate 6: RBC with biofilm on disc...............................................................82 Plate 7: Sampling point for influent to RBC...................................................83 Plate 8: Sampling point of influent to RBC....................................................83

viii

 ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download