REMOVAL OF PHOSPHORUS FROM AQUEOUS SOLUTIONS

Transcription

1 e-ý ;.. ý ý ý,. iý, t+urllat A1akstirttat AkaQelrilx. UNIVERSITI MALAYSIA SARAWAK ()4; 0O Kola Samarahan P. KHIDMAT MAKLUMAT AKADEMIK UNIMAS REMOVAL OF PHOSPHORUS FROM AQUEOUS SOLUTIONS USING SELECTED MATERIALS TIONG PEI JEN A thesis in fulfillment of the requirements submitted for the degree of Master of Science Institute of Biodiversity and Environmental Conservation UNIVERSITI MALAYSIA SARAWAK 2007

2 Acknowledgements I would like to sincerely express my utmost gratitude and appreciation to my research supervisor, Prof. Dr. Lau Seng from Faculty of Resource Science and Technology, Universiti Malaysia Sarawak, for his sustained interest, constructive criticisms, guidance and invaluable support throughout my undertaking of this project. I would also like to thank my parents, my brother and my sisters for their unrelenting support, understanding, confidence, care and inspiration. Besides that, my warmest thanks to all my friends, laboratory assistants, and all staff from Institute of Biodiversity and Environmental Conservation (IBEC), Universiti Malaysia Sarawak for their kind assistance through the course of my study. I gratefully acknowledge the scholarship award by Kuok Foundation Berhad during the course of my study. Last but not least, I would like to convey my heartiest gratitude and appreciation to anyone who has in one way or another contribute towards the success of this project. i

3 Abstract In Malaysia, eutrophication induced by excess phosphorus in water sources is one of the major causes of water pollution. The sources of phosphorus include grey water and the inefficiently treated effluents from septic tanks. The high concentration of phosphorus in our grey water is due to the extensive usage of phosphate-based detergents for laundering and other cleaning purposes. Conventional phosphorus removal methods (e. g. chemical precipitation, reverse osmosis, ion exchange and electrodialysis) are either energy and cost intensive or not environmentally sustainable. Biological phosphorus removal has limited phosphate removal capacity. Thus, an efficient, energy and costsaving, as well as environmentally sustainable phosphorus removal process should be established. In this study, the physical and chemical characteristics of three locally available materials (limestone, red bricks, and degraded shale) were determined, and their phosphorus (P) adsorption performance were examined using both batch and column experiments. Desorption studies were carried out to determine the P adsorption strength of the materials. The main objective of the study was to determine the efficiency of three selected materials in removing phosphorus from aqueous solutions, and their potential to be used as substrate in constructed wetland of an ecological sanitation (ecosan) system. The physical characteristics determined include specific gravity and particle density, bulk density and porosity, bed porosity, and ph values. For chemical characterizations, P content, calcium carbonate, and metal contents (Ca, Mg, Fe and Al) of the materials were determined. Batch experiments were carried out to ascertain the adsorption of the various materials for phosphorus under different experimental conditions (agitation time, ph, grain size, initial phosphorus concentration, mixture of materials). Column experiments were carried out for the same factors as in batch 11

4 experiments in order to enable the comparison between results obtained from both experiments. The phosphate-p adsorbed was determined using colorimetric method by UV/VIS spectrometer. The results obtained show that among the three materials tested, red bricks seemed to be the most porous, followed by limestone and degraded shale, with porosity of 0.32, 0.29, and 0.17, respectively. Red brick was the most acidic (ph 4.26). Degraded shale was almost neutral (ph 7.51), whereas limestone was the most alkaline (ph 8.12). Both red bricks and degraded shale were found to fit into the pseudo-second order kinetic models (R2>0.981). Limestone however, seemed to give the best fit into pseudo-first order kinetic model. The Freundlich equation was observed to model the phosphorus adsorption data better than Langmuir equation when considering all the adsorbents investigated. Overall results from batch experiments show that when 10 mg P/L of phosphate solution was applied to materials with 4-10 mm grain size, both red bricks and limestone exhibit relatively high phosphorus adsorption percentage (>80%). Meanwhile, degraded shale had very low phosphorus adsorption performance (<10%). The mixture of materials exhibited lower phosphorus removal efficiencies than unmixed materials except for degraded shale. Limestone used was found to accumulate up to mg P/kg material upon saturation while red bricks were found to accumulate only mg P/kg material when saturated. The studies on performance of materials under repeated cycles show that limestone gave the best result under long run when compared to red bricks and degraded shale. Low phosphorus desorbability was observed for limestone and red bricks. Both materials exhibited desorbability of <10% at all ph tested. Degraded shale was observed to have a high desorbability of about 32-50%, except for ph 3 (about 15%). From the results obtained, it can be concluded that among the materials tested, limestone has the greatest potential for phosphorus removal in aqueous solution. 111

5 PENGASINGAN FOSFOR US DARI LAR UTAN AKUEUS MENGG UNAKAN BAHAN TERPILIH Abstrak Di Malaysia, eutrofikasi yang disebabkan oleh kehadiran fosforus yang berlebihan di sumber air merupakan salah satu faktor utama berlakunya pencemaran air. Sumber fosforus tersebut adalah dart air buangan domestik dan air kumbahan tangki septik yang tidak dirawat dengan sempurna. Kandungan fosforus yang tinggi dalam air kumbahan domestik kita berpunca daripada penggunaan detergen berfosfat secara berleluasa untuk pelbagai aktiviti pencucian. Cara konvensyen untuk pengeluaran fosforus (contohnya: pemendakan kimia, osmosis pembalikan, penukaran ion, dan elektrodialisis) sama ada memakan kos dan bekalan tenaga yang tinggi, atau tidak mesra alam. Pengasingan fosforus dengan cara biologi pula didapati menipunyai kapasiti pengeluaran fosforus yang terhad. Oleh itu, satu proses pengasingan fosforus yang bukan sahaja menjimatkan kos dan bekalan tenaga tetapi juga mesra alam perlu dicari. Dalam kajian ini, ciri-ciri fizikal dan kimia bagi tiga jenis bahan (batu kapur, bata merah, dan batu `degraded shale) ditentukan. Keputusan penjerapa. n fosforus telah diuji menggunakan eksperimen `batch' dan eksperimen turus. Eksperimen pendejerapan juga dijalankan untuk menentukan kekuatan penjerapan fosforus bagi bahan kajian. Tujuan utama kajian ini adalah untuk menentukan efisiensi bahan terpilih untuk mengasingkan fosforus dart laru, tan akueus, dan potensi mereka untuk dijadikan sebagai substrat bagi paya buatan dalam sistem `sanitasi ekologi : Ciri-ciri fizikal yang ditentukan termasuk graviti tentu dan ketumpatan partikel, ketumpatan pukal dan porositi, porositi dasar, dan nilai ph. Bagi ciri-ciri kimia, kandungan fosforus, kalsium karbonat, dan unsur (Ca, Mg, Fe, dan Al) dalam bahan kajian tela. h ditentukan. iv

6 Eksperimen `batch' telah dijalankan untuk menentukan penjerapan fosforus pada bahan kajian di bawah keadaan eksperimen yang berbeza (Masa tindak balas, ph, saiz bahan, kepekatan fosforus dalam larutan, campuran bahan). Eksperimen turus telah dijalankan untuk mengkaji faktor-faktor yang sama dengan eksperimen `batch' agar perbandingan dapat dibuat antara keputusan yang diperoleh daripada kedua-dua jenis eksperimen. Fosforus yang terjerap ditentukan dengan kaedah kolorimetri menggunakan UV/VIS spektrometer. Keputusan yang diperoleh menunjukkan antara tiga jenis bahan kajian yang digunakan, bata merah adalah paling poros, diikuti dengan batu kapur dan akhirnya batu `degraded shale; dengan porositi 0.32, 0.29, dan 0.17 masing-masing. Bata merah adalah paling berasid (ph 4.26). Batu `degraded shale' adalah hampir neutral (ph 7.51), manakala batu kapur adalah paling beralkali (ph 8.12). Kedu, a-dua bata merah dan batu `degraded shale' adalah berpadanan dengan model kinetik pseudosecond (R9>0.981). Batu kapur pula lebih sesuai untuk dipadankan dengan model kinetik pseudo-first order: Persamaan Freundlich didapati dapat menggambarkan penjerapan fosforus dengan lebih baik untuk semua bahan kajian berbandingpersamaan Langmu, ir. Keputusan keseluruhan dart eksperimen `batch' menunjukkan bahawa apabila larutan fosforus 10 mg P/L dan bahan kajian dengan saiz 4-10 mm digunakan, kedua-dua bata merah dan batu kappur memberikan peratus penjerapan fosforus yang agak tinggi (? 80%). Sementara itu, batu 'degraded shale' memberikan peratus penjerapan fosforus yang rendah (<10%). Campuran bahan kajian memberikan kecekapan pengasingan fosforus yang lebih rendah daripada bahan kajian yang tidak dicampur, kecuali batu `degraded shale'. Batu kapur didapati mencapai takat tepu dengan mg P/kg bahan, m, anakala bata merah mempunyai takat tepu pada mg P/kg bahan. Keputusan untuk persembahan bahan-bahan kajian dalam kitaran berulang menunjukkan bahawa batu kapur memperlihatkan pengasingan fosforus yang paling baik untu. k jangka masa V

7 panjang berbanding bata merah dan batu `degraded shale' Pendejerapan fosforus yang rendah diperhatikan untuk kedua-dua batu kapur dan bata merah, di mana kedua-dua bahan mempamerkan pendejerapan <10% pada sebarang ph yang dikaji. Batu `degraded shale' diperhatikan mempunyai peratus pendejerapan yang tinggi, ia. itu lebih kurang 32-50%, kecuali pada ph 3 (lebih kurang 15%). Kesimpulannya, antara ketiga-tiga bahan yang dikaji, batu kapur mempunyai potensi yang paling tinggi untuk pengasingan fosforus dari larutan akueus. vi

8 rusat htlidnlat Milklumat UNIVERSITI Akaaemºw MALAYSIA SARAWAK u41(1() Kota Samarahaa Table of Contents Page Title Acknowledgements Abstract Abstrak Table of Contents List of Tables List of Figures List of Abbreviations List of Symbols 1 11 IV vii X1V xvii xxi xxiii Chapter 1 INTRODUCTION 1.1 The State of Water Pollution in Malaysia and Worldwide Main Pollutants in Malaysia and Worldwide Non Compliance of Discharges from Conventional 7 Treatment System to the Malaysian Water Quality Standard 1.4 Problem Statement and Potential Solution Objectives of Study Scope of Study 15 vii

9 Chapter 2 LITERATURE REVIEW 2.1 Wastewater Composition of Wastewaters Typical Composition of Grey Water Nutrients in the Wastewater Nitrogen Phosphorus Chemical Properties of Phosphorus 28 (a) Aqueous Chemistry 28 (b) Solid Phase/ Adsorption 31 (i) Kinetics of Phosphorus Adsorption 34 (ii) Phosphorus Adsorption Isotherms Environmental Impacts of Phosphorus Usage Impacts on Water Body Impacts from Agriculture Depletion of Phosphorus Resource Wastewater Treatment Conventional Treatment System Phosphorus Removal Processes in 45 viii

10 Conventional Treatment System (a) Biological Phosphorus Removal 45 (b) Chemical Precipitation 46 (i) Phosphate Precipitation with Calcium 47 (ii) Phosphate Precipitation with Aluminium 48 and Iron Ecological Sanitation System Constructed Wetland as Component in an 52 Ecological Sanitation System (a) Surface Flow Constructed Wetland 54 (b) Subsurface Flow Constructed Wetland Phosphorus Removal Mechanisms in 56 Constructed Wetland (a) Removal of Phosphorus through 59 Adsorption and Precipitation (b) Phosphorus Uptake by Plants 62 (c) Phosphorus Removal by Microorganisms Strength and Weaknesses of Ecological 63 Sanitation System (a) Strength of Ecological Sanitation System 63 (i) Economical and Affordable for All 63 (ii) Increasing Health and Dignity 64 (iii)recycling and Reuse of Resources 64 (b) Weaknesses of Ecological Sanitation System Media Materials Studied by Other Researchers 66 ix

11 Chapter 3 MATERIALS AND METHODS 3.1 Materials Methodology Experiment 1 (Characterizations of Media Materials) Physical Characterizations 69 (a) Specific Gravity and Particle Density 69 (b) Bulk Density and Porosity 71 (c) Bed Porosity 74 (d) ph Values Chemical Characterizations 76 (a) Calcium Carbonate Content in Media 76 Materials (b) Metal (Fe, Ca, Mg, Al) and P Content 77 in Media Materials Experiment 2 (Evaluation of the Performance of 77 Materials in Phosphorus Adsorption) Batch Adsorption Experiments 78 (a) Studies on Adsorption Kinetics 80 (b) Studies on Adsorption Isotherm 81 (c) Effect of Initial Phosphorus Concentration 82 (d) Effect of ph 82 (e) Effect of Grain Size 83 (f) Effect of Mixture of Materials Experiment 3 (Determination of P Accumulated 85 onto Materials) Experiment 4 (Desorption Studies) 87 X

12 3.2.5 Experiment 5 (Column Adsorption Experiments) 88 (a) Studies on Retention Time 89 (b) Effect of Initial Phosphorus Concentration 90 (c) Effect of ph 91 (d) Effect of Grain Size 92 (e) Effect of Mixture of Materials Experiment 6 (Studies on Performance of Materials under 93 Repeated Cycles) 3.3 Analytical Procedures 94 (a) Vanadomolybdophosphoric Acid 95 Colorimetric Method (b) Ascorbic Acid Method Statistical Analysis 98 Chapter 4 RESULTS AND DISCUSSION 4.1 Characteristics of Media Materials Physical Characteristics of Media Materials Chemical Characteristics of Media Materials Batch Adsorption Experiments Adsorption Kinetics Adsorption Isotherms Effect of Initial Phosphorus Concentration 115 X1

13 4.2.4 Effect of ph Effect of Grain Size Effect of Mixture of Materials Determination of P Accumulated onto Materials Desorption Studies Column Adsorption Experiments Effect of Retention Time Effect of Initial Phosphorus Concentration Effect of ph Effect of Grain Size Effect of Mixture of Materials Studies on Performance of Materials under 135 Repeated Cycles Chapter 5 CONCLUSION AND RECOMMENDATION 5.1 Conclusions Recommendations for Further Research 140 xii

14 REFERENCES 141 APPENDICES Appendix A 165 Appendix B 168 Appendix C 174 Appendix D 178 Appendix E 179 X111

15 List of Tables Table 1.1 National Water Quality Standard for Malaysia. Page 8-10 Table 2.1 Average daily production and nutrient content of urine and 18 faeces. Table 2.2 Typical composition of grey water. 21 Table 2.3 Percentage of nutrients emission from grey water to the 22 environment. Table 2.4 Typical Phosphorus Concentrations in Raw Domestic 24 Wastewater. Table 2.5 Forms of phosphates depending on ph. 29 Table 2.6 Approximate nutrient composition of average sanitary 46 wastewater (mg/l) based on 120 gal per capita per day (gpcd) (450 L/person. d). Table 2.7 The possible calcium-phosphate minerals that might form 60 and their Ca/P molar ratio. Table 4.1 Physical characteristics of different materials tested for 99 P-adsorption properties. Table 4.2 Chemical characteristics of different materials tested for 101 P-adsorption properties. Table 4.3 Values of adsorption rate constants, calculated qe and coefficient 107 of determination (R2) obtained from different kinetic models. xiv

16 Table 4.4 Langmuir and Freundlich models regression constants. 112 Table 4.5 Desorbability of the adsorbed phosphate-p on selected 127 materials in DI water with different ph. Table 4.6 Performance of mixture of materials for phosphorus adsorption. 134 Table Al Phosphorus adsorption with different agitation time. 165 Table A2 Phosphorus adsorption with different initial phosphorus 166 concentration. Table A3 Phosphorus adsorption with different ph. 166 Table A4 Phosphorus adsorption with different grain size. 167 Table A5 Phosphorus adsorption by mixture of materials under 167 different ph. Table Cl The calculated values of dimensionless separation factor (r) 177 called equilibrium parameter using Langmuir constant (b). Table D 1 Phosphorus accumulated on limestone and red bricks under 178 repeated cycles of batch experiments using initial phosphorus concentration of 200 mg/l. Table El Phosphorus adsorption with different retention time. 179 Table E2 Phosphorus adsorption with different initial phosphorus 180 concentration. Table E3 Phosphorus adsorption with different ph. 180 Table E4 Phosphorus adsorption with different grain size. 181 xv

17 Table E5 Phosphorus adsorption performance under repeated cycles. 182 xvi

18 List of Figures Figure 2.1 Combined Wastewater. Page 19 Figure 2.2 Several Forms of Phosphate. 25 Figure 2.3 Linear flows in a conventional sanitation system. 44 Figure 2.4 Circular flows in an Ecosan system. 51 Figure 2.5 Effect of ph on phosphate precipitation with different metal ions. 60 Figure 2.6 Effect of redox potential on phosphate precipitation with 61 different metal ions. Figure 3.1 Conical flasks with materials in phosphate solution. 79 Figure 3.2 Experimental setup for batch experiments. 79 Figure 3.3 Perkin-Elmer Lambda 25 UV/VIS Spectrometer. 80 Figure 3.4 Experimental setup for column experiments. 89 Figure 4.1 Phosphorus adsorption kinetic data for selected materials. 103 Figure 4.2 Application of the intraparticle diffusion model to the 110 measured kinetic data for the studied materials. Figure 4.3 P adsorption with respect to initial phosphorus concentration 116 (a) mg P adsorbed/ kg material in 4 different P concentrations (b) percentage P removal in solutions of different initial P concentration. xvii

19 Figure 4.4 Adsorption of P with respect to ph. 117 Figure 4.5 P adsorption with respect to grain size. 120 Figure 4.6 Adsorption of P with respect to mixture of materials. 121 Figure 4.7 Accumulated P (mg/kg) adsorbed by materials under 123 repeated cycles. Figure 4.8 Limestone before phosphorus adsorption. 125 Figure 4.9 Limestone after phosphorus adsorption under repeated cycles. 125 Figure 4.10 Adsorption of P with respect to retention time. 129 Figure 4.11 Adsorption of P with respect to initial phosphorus concentration. 130 Figure 4.12 Adsorption of P with respect to ph. 131 Figure 4.13 Adsorption of P with respect to grain size. 133 Figure 4.14 Adsorption of P under repeated cycles. 136 Figure B1 Linearized form of pseudo-first order adsorption kinetics of 168 red bricks for phosphate-p. qe = P adsorbed by red bricks at equilibrium; qt = P adsorbed by red bricks at time t Figure B2 Linearized form of pseudo-second order adsorption kinetics of 168 red bricks for phosphate-p. t = time t; [Pit = P adsorbed by red bricks at time t Figure B3 Linearized form of Elovich adsorption kinetics of red bricks for 169 phosphate-p. q = amount of P adsorbed; t = adsorption time xviii

20 Figure B4 Linearized form of power function adsorption kinetics of red 169 bricks for phosphate-p. t = time t; [P] = P adsorbed by red bricks at time t Figure B5 Linearized form of pseudo-first order adsorption kinetics of 170 limestone for phosphate-p. qe = P adsorbed by limestone at equilibrium; qt = P adsorbed by limestone at time t Figure B6 Linearized form of pseudo-second order adsorption kinetics of 170 limestone for phosphate-p. t = time t; [P]t = P adsorbed by limestone at time t Figure B7 Linearized form of Elovich adsorption kinetics of limestone for 171 phosphate-p. q = amount of P adsorbed; t = adsorption time Figure B8 Linearized form of power function adsorption kinetics of 171 limestone for phosphate-p. t = time t; [P] = P adsorbed by limestone at time t Figure B9 Linearized form of pseudo-first order adsorption kinetics of 172 degraded shale for phosphate-p. qe = P adsorbed by degraded shale at equilibrium; qt = P adsorbed by degraded shale at time t Figure B10 Linearized form of pseudo-second order adsorption kinetics of 172 degraded shale for phosphate-p. t = time t; [P]t = P adsorbed by degraded shale at time t Figure B11 Linearized form of Elovich adsorption kinetics of degraded shale 173 for phosphate-p. q = amount of P adsorbed; t = adsorption time Figure B12 Linearized form of power function adsorption kinetics of 173 degraded shale for phosphate-p. t = time t; [P] = P adsorbed by degraded shale at time t xix

21 Figure C1 Adsorption data for red bricks according to Langmuir (a) 174 and Freundlich (b) isotherms. qe = P adsorbed by red bricks; C. = equilibrium P concentration in the solution Figure C2 Adsorption data for limestone according to Langmuir (a) 175 and Freundlich (b) isotherms. qe = P adsorbed by limestone; Ce = equilibrium P concentration in the solution Figure C3 Adsorption data for degraded shale according to Langmuir (a) 176 and Freundlich (b) isotherms. qe = P adsorbed by degraded shale; Ce = equilibrium P concentration in the solution xx

22 List of Abbreviations ADP adenosine diphosphate AES atomic emission spectroscopy/spectrometry AGI acute gastrointestinal illness AMP adenosine monophosphate APHA American Public Health Association ATP adenosine triphosphate BOD biochemical oxygen demand COD chemical oxygen demand CWS constructed wetland systems DI deionized DNA deoxyribonucleic acid DO dissolved oxygen DOE Department of Environment Ecosan ecological sanitation EPA Environmental Protection Agency FWS free-water-surface GTZ Gesellschaft für Technische Zusammenarbeit HSFCW horizontal subsurface flow constructed wetland ICP inductively coupled plasma IHP International Hydrological Programme LECA light-weight expanded clay aggregates LWA light weight aggregates NREB Natural Resource and Environment Board PVC polyvinyl chloride RNA ribonucleic acid SEPA State Environmental Protection Administration SF subsurface flow SS suspended solids TSS total suspended solids UK United Kingdom UNESCO United Nations Educational, Scientific and Cultural Organization U. S United States xxi

23 USEPA United States Environmental Protection Agency UV ultra violet VIS WHO visible World Health Organization xxii

24 List of Symbols < less than > more than < less than or equal to 2-D two dimensional 3-D three dimensional µg microgram C degree Celsius or Centigrade cm centimetre cm3 centimetre cube conc. d Eq ft g gal ha hr in. kg km L lb m M concentration day equation feet gram gallon hectare hour inch kilogram kilometre litre pound metre Molar m2 metre square mg min ml mm pe ppd ppm milligram minute millilitre millimetre redox potential person per day part per million xxiii