Design and development of two novel constructed wetlands : the duplex-constructed wetland and the constructed wetroof

Constructed Wetlands (CWs) are among the few natural treatment systems that can guarantee an efficient wastewater treatment and an appealing green space at the same time. However, they require large areas for their construction, which is not available in many cases. In this thesis, two domestic wastewater treatment options were designed and studied with the purpose of having a low space requirement: the Duplex-CW and the Constructed Wetoof (CWR). The Duplex-CW is a hybrid CW composed of a vertical flow CW on top of a horizontal flow filter. The stacked arrangement is the key for reducing the CW footprint. The CWR is a shallow HF CW placed on the roof of a building, thus it does not occupy any land. Several modifications and improvements have been tested, in addition to the study of the treatment performance, in order to select the most appropriate Duplex-CW and CWR design. Overall, this thesis contributes to the development of two efficient domestic wastewater treatment technologies. The Duplex-CW area requirement is still higher than many CWs and therefore further improvements are necessary. The CWR is the foremost option to save land areas since it requires 0 m 2 of land per person equivalent. Constructed wetlands (CWs) can guarantee an efficient wastewater treatment and an appealing green space at the same time. However, they require large areas for their construction that in many cases is not available. Two domestic wastewater treatment options were designed and studied with the purpose of having a low space requirement: the Duplex-CW and the constructed wetroof (CWR). Several modifications and improvements have been tested in order to select the most appropriate Duplex-CW and CWR design. Overall, this thesis contributes to the development of two efficient domestic wastewater treatment technologies. The CWR is the foremost option to save land areas since it requires 0 m2 of land per person equivalent. CHAPTER 1. GENERAL INTRODUCTION 20 1.1. NEED OF NATURAL WASTEWATER TREATMENT SYSTEMS 21 1.2. CONSTRUCTED WETLANDS: GENERAL OVERVIEW 23 1.3. SCOPE AND OBJECTIVES OF THIS THESIS 24 1.4. THESIS OUTLINE/ STRUCTURE 25 CHAPTER 2. LITERATURE REVIEW 26 2.1. Introduction 27 2.2. BOOSTING THE TREATMENT EFFICIENCY 28 2.2.1. Recirculation 29 2.2.2. Passive and active aeration 33 2.2.3. Fill and drain, tidal or reciprocating 36 2.2.4. No pre-treatment 38 2.2.5. Enhancing phosphorus removal 39 2.3. stackING up extra treatment stages 40 2.4. placING the constructed wetland at unused spaces 42 2.4.1. Roofs 42 2.4.2. Walls 43 2.5. EVOLUTION OF THE Constructed wetland footprint OVER TIME 44 2.6. CONCLUSION 46 CHAPTER 3. USE OF MARINE AND ENGINEERED MATERIALS FOR THE REMOVAL OF PHOSPHORUS FROM SECONDARY EFFLUENT 48 3.1. INTRODUCTION 49 3.2. MATERIALS AND METHODS 50 3.2.1. Tested material and phosphorus source 50 3.2.2. Batch experiments 50 3.2.3. Column experiments 51 3.2.4. Tests for pyrolyzed material phosphorus removal mechanism 52 3.2.5. Analytical methods 53 3.3. RESULTS 53 3.3.1. Batch experiments 53 3.3.1.1. Marine materials 53 3.3.1.2. Engineered material 55 3.3.2. Column experiments 56 3.3.3. Phosphorus removal mechanism of the pyrolyzed material 57 3.4. DISCUSSION 58 3.4.1. Pyrolyzed marine materials 58 3.4.2. Raw marine materials 59 3.4.3. Engineered material 59 3.4.4. Effect of sand 60 3.4.5. Engineered vs. pyrolyzed marine material: comparison and practical use 61 3.5. CONCLUSION 62 CHAPTER 4. EFFECT OF AERATION ON POLLUTANTS REMOVAL, BIOFILM ACTIVITY AND PROTOZOAN ABUNDANCE IN CONVENTIONAL AND HYBRID HORIZONTAL SUBSURFACE-FLOW CONSTRUCTED WETLANDS 64 4.1. INTRODUCTION 65 4.2. MATERIALS AND METHODS 66 4.2.1. Experimental set-up 66 4.2.2. Operating mode 67 4.2.3. Sampling and analytical techniques 67 4.2.4. Data analysis 69 4.3. RESULTS 69 4.3.1. Treatment performance 69 4.3.1.1. Organic matter and solids 69 4.3.1.2. Nutrients 72 4.3.2. Microbial characterization of the biofilm 73 4.4. DISCUSSION 74 4.4.1. Effect of aeration on organic matter, solids and nutrients removal 74 4.4.2. Effect of aeration on microbial community interactions 75 4.4.3. Footprint of constructed wetlands 76 4.5. CONCLUSIONS 76 CHAPTER 5. AERATION AND RECIRCULATION IN A STACK ARRANGED HYBRID CONSTRUCTED WETLAND FOR TREATMENT OF PRIMARY DOMESTIC WASTEWATER 78 5.1. Introduction 79 5.2. Materials and methods 79 5.2.1. Experimental setup 79 5.2.2. Experimental design and sample collection 81 5.2.2.1. Regular operation 81 5.2.2.2. Operation with the addition of a carbon source to the HFF to stimulate denitrification 81 5.2.3. Analytical methods 82 5.2.3.1. Water 82 5.2.3.2. Sand and roots 82 5.2.3.3. Batch experiment for protozoa and metazoa grazing on E. coli 83 5.2.4. Data analysis 83 5.3. Results 84 5.3.1. Removal of organic matter and solids 84 5.3.2. Nitrogen 84 5.3.3. Carbon source as electron donor for denitrification 86 5.3.4. Pathogens, protozoa and metazoa 89 5.3.5. Microbial activity 91 5.4. Discussion 91 5.4.1. Role of recirculation and aeration in the Duplex-CW design 91 5.4.2. Organic matter and nitrogen removal 95 5.4.3. Filtered influent as carbon source to enhance denitrification in the HFF 96 5.4.4. Role of the Duplex-CW compartments in nitrogen removal 96 5.4.5. Bacteria and protozoa 98 5.4.6. Microbial activity 99 5.5. Conclusions 99 CHAPTER 6. EVALUATION OF THE PERFORMANCE AND SPACE REQUIREMENT BY THREE DIFFERENT HYBRID CONSTRUCTED WETLANDS IN A STACK ARRANGEMENT 100 6.1. INTRODUCTION 101 6.2. MATERIALS AND METHODS 101 6.2.1. Experimental setup 101 6.2.2. Experimental design 104 6.2.3. Sample collection and analytical methods 105 6.2.4. Data analysis 106 6.3. RESULTS 107 6.3.1. Influence of different domestic wastewater strengths on the performance of the VF CW and HFF compartments 107 6.3.2. Effect of artificial aeration on the treatment of WW++ 113 6.3.3. Solids accumulation on the sand, plant biomass and nutrient uptake 114 6.3.4. VF CW oxygen diffusion experiment 116 6.4. DISCUSSION 116 6.4.1. Wastewater strength 116 6.4.2. Contribution of the VF CW and HFF compartments to pollutant removal 118 6.4.3. Aeration 119 6.4.4. Solids accumulation on the sand 120 6.4.5. Plant biomass and nutrient uptake 121 6.4.6. Duplex-CW footprint reduction and design selection 121 6.5. CONCLUSION 122 CHAPTER 7. MATERIAL SELECTION FOR A CONSTRUCTED WETROOF RECEIVING PRE-TREATED HIGH STRENGTH DOMESTIC WASTEWATER 124 7.1. Introduction 125 7.1.1. Roofs as wastewater treatment systems 125 7.2. Materials and methods 126 7.2.1. Material selection: experimental set up and design 127 7.2.2. Wastewater in the full-scale constructed wetroof 129 7.3. Results and discussion 129 7.3.1. Substrata characteristics and testing-table tests 129 7.3.2. Wastewater treatment 131 7.3.3. Practical design considerations 132 7.4. Conclusions 132 CHAPTER 8. CONSTRUCTED WETROOFS: A NOVEL APPROACH FOR THE TREATMENT AND REUSE OF DOMESTIC WASTEWATER AT HOUSEHOLD LEVEL 134 8.1. Introduction 135 8.2. Materials and methods 136 8.2.1. Constructed wetroof description 136 8.2.2. Experiments and sampling 137 8.2.3. Analytical methods 139 8.3. Results 139 8.3.1. Water path along the bed length and water balance 139 8.3.2. Wastewater treatment 142 8.3.3. Activity of the media 142 8.3.4. Nutrient content and balance 145 8.3.5. Material quantities 147 8.4. Discussion 147 8.4.1. Water movement and retention 147 8.4.2. Aerobic characteristics of the CWR 148 8.4.3. CWR performance 148 8.4.4. Media nutrient retention capacity 152 8.4.5. Media contribution to the treatment 152 8.4.6. Area and volume requirements by the constructed wetroof 153 8.5. Conclusions 154 CHAPTER 9. GENERAL DISCUSSION AND CONCLUSIONS 156 9.1. INTRODUCTION 157 9.2. design areas of CONSTRUCTED WETLANDs 157 9.3. approaches IN THIS THESIS to select the required constructed wetland area 158 9.4. OPTIMIZATION OF THE PERFORMANCE AND AREA REQUIREMENT OF The Duplex-CW 159 9.4.1. Type of constructed wetland and arrangement 159 9.4.2. Water flow operation and configurations 159 9.4.3. Intensification 160 9.4.4. Carbon as electron donor for denitrification 160 9.4.5. Post-treatment for phosphorus removal 161 9.4.6. Area requirement 161 9.4.7. Duplex-CW area design in the literature context 164 9.4.8. Recommended Duplex-CW design 164 9.5. development of The constructed wetroof 165 9.5.1. Filter material selection and arrangement 165 9.5.2. Aerobic conditions and effluent quality 165 9.5.3. Operation under different climate conditions: effect of temperature and rain 166 9.5.4. Constructed wetroof in the literature context 167 9.5.5. Recommended constructed wetroof design 168 9.6. CONCLUSIONS 168 REFERENCES 170 APPENDICES 182 SENSE Diploma-Zapater-Final 210 Area,(footprint),requirement;,artificial,aeration;,constructed,wetlands;,domestic,wastewater;,green,roof,for,wastewater,treatment;,natural,wastewater,treatment,systems;,nitrogen;,organic,matter;,phosphorus;,recirculation. Area (footprint) requirement,artificial aeration,constructed wetlands,domestic wastewater,green roof for wastewater treatment,natural wastewater treatment systems,nitrogen,organic matter,phosphorus,recirculation.