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

Description

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 m2 of land per person equivalent. Content: 1 GENERAL INTRODUCTION 1.1. NEED OF NATURAL WASTEWATER TREATMENT SYSTEMS 1.2. CONSTRUCTED WETLANDS: GENERAL OVERVIEW 1.3. SCOPE AND OBJECTIVES OF THIS THESIS 1.4. THESIS OUTLINE/ STRUCTURE 2 LITERATURE REVIEW 2.1. INTRODUCTION 2.2. BOOSTING THE TREATMENT EFFICIENCY 2.2.1. Recirculation 2.2.2. Passive and active aeration 2.2.3. Fill and drain, tidal or reciprocating 2.2.4. No pre-treatment 2.2.5. Enhancing phosphorus removal 2.3. STACKING UP EXTRA TREATMENT STAGES 2.4. PLACING THE CONSTRUCTED WETLAND AT UNUSED SPACES 2.4.1. Roofs 2.4.2. Walls 2.5. EVOLUTION OF THE CONSTRUCTED WETLAND FOOTPRINT OVER TIME 2.6. CONCLUSION 3 USE OF MARINE AND ENGINEERED MATERIALS FOR THE REMOVAL OF PHOSPHORUS FROM SECONDARY EFFLUENT 3.1. INTRODUCTION 3.2. MATERIALS AND METHODS 3.2.1. Tested material and phosphorus source 3.2.2. Batch experiments 3.2.3. Column experiments 3.2.4. Tests for pyrolyzed material phosphorus removal mechanism 3.2.5. Analytical methods 3.3. RESULTS 3.3.1. Batch experiments 3.3.2. Column experiments 3.3.3. Phosphorus removal mechanism of the pyrolyzed material 3.4. DISCUSSION 3.4.1. Pyrolyzed marine materials 3.4.2. Raw marine materials 3.4.3. Engineered material 3.4.4. Effect of sand 3.4.5. Engineered vs. pyrolyzed marine material: comparison and practical use 3.5. CONCLUSION 4 EFFECT OF AERATION ON POLLUTANTS REMOVAL, BIOFILM ACTIVITY AND PROTOZOAN ABUNDANCE IN CONVENTIONAL AND HYBRID HORIZONTAL SUBSURFACE-FLOW CONSTRUCTED WETLANDS 4.1. INTRODUCTION 4.2. MATERIALS AND METHODS 4.2.1. Experimental set-up 4.2.2. Operating mode 4.2.3. Sampling and analytical techniques 4.2.4. Data analysis 4.3. RESULTS 4.3.1. Treatment performance 4.3.2. Microbial characterization of the biofilm 4.4. DISCUSSION 4.4.1. Effect of aeration on organic matter, solids and nutrients removal 4.4.2. Effect of aeration on microbial community interactions 4.4.3. Footprint of constructed wetlands 4.5. CONCLUSIONS 5 AERATION AND RECIRCULATION IN A STACK ARRANGED HYBRID CONSTRUCTED WETLAND FOR TREATMENT OF PRIMARY DOMESTIC WASTEWATER 5.1. INTRODUCTION 5.2. MATERIALS AND METHODS 5.2.1. Experimental setup 5.2.2. Experimental design and sample collection 5.2.3. Analytical methods 5.2.4. Data analysis 5.3. RESULTS 5.3.1. Removal of organic matter and solids 5.3.2. Nitrogen 5.3.3. Carbon source as electron donor for denitrification 5.3.4. Pathogens, protozoa and metazoa 5.3.5. Microbial activity 5.4. DISCUSSION 5.4.1. Role of recirculation and aeration in the Duplex-CW design 5.4.2. Organic matter and nitrogen removal 5.4.3. Filtered influent as carbon source to enhance denitrification in the HFF 5.4.4. Role of the Duplex-CW compartments in nitrogen removal 5.4.5. Bacteria and protozoa 5.4.6. Microbial activity 5.5. CONCLUSIONS 6 EVALUATION OF THE PERFORMANCE AND SPACE REQUIREMENT BY THREE DIFFERENT HYBRID CONSTRUCTED WETLANDS IN A STACK ARRANGEMENT 6.1. INTRODUCTION 6.2. MATERIALS AND METHODS 6.2.1. Experimental setup 6.2.2. Experimental design 6.2.3. Sample collection and analytical methods 6.2.4. Data analysis 6.3. RESULTS 6.3.1. Influence of different domestic wastewater strengths on the performance of the VF CW and HFF compartments 6.3.2. Effect of artificial aeration on the treatment of WW++ 6.3.3. Solids accumulation on the sand, plant biomass and nutrient uptake 6.3.4. VF CW oxygen diffusion experiment 6.4. DISCUSSION 6.4.1. Wastewater strength 6.4.2. Contribution of the VF CW and HFF compartments to pollutant removal 6.4.3. Aeration 6.4.4. Solids accumulation on the sand 6.4.5. Plant biomass and nutrient uptake 6.4.6. Duplex-CW footprint reduction and design selection 6.5. CONCLUSION 7 MATERIAL SELECTION FOR A CONSTRUCTED WETROOF RECEIVING PRE-TREATED HIGH STRENGTH DOMESTIC WASTEWATER 7.1. INTRODUCTION 7.1.1. Roofs as wastewater treatment systems 7.2. MATERIALS AND METHODS 7.2.1. Material selection: experimental set up and design 7.2.2. Wastewater in the full-scale constructed wetroof 7.3. RESULTS AND DISCUSSION 7.3.1. Substrata characteristics and testing-table tests 7.3.2. Wastewater treatment 7.3.3. Practical design considerations 7.4. CONCLUSIONS 8 CONSTRUCTED WETROOFS: A NOVEL APPROACH FOR THE TREATMENT AND REUSE OF DOMESTIC WASTEWATER AT HOUSEHOLD LEVEL 8.1. INTRODUCTION 8.2. MATERIALS AND METHODS 8.2.1. Constructed wetroof description 8.2.2. Experiments and sampling 8.2.3. Analytical methods 8.3. RESULTS 8.3.1. Water path along the bed length and water balance 8.3.2. Wastewater treatment 8.3.3. Activity of the media 8.3.4. Nutrient content and balance 8.3.5. Material quantities 8.4. DISCUSSION 8.4.1. Water movement and retention 8.4.2. Aerobic characteristics of the CWR 8.4.3. CWR performance 8.4.4. Media nutrient retention capacity 8.4.5. Media contribution to the treatment 8.4.6. Area and volume requirements by the constructed wetroof 8.5. CONCLUSIONS 9 GENERAL DISCUSSION AND CONCLUSIONS 9.1. INTRODUCTION 9.2. DESIGN AREAS OF CONSTRUCTED WETLANDS 9.3. APPROACHES IN THIS THESIS TO SELECT THE REQUIRED CONSTRUCTED WETLAND AREA 9.4. OPTIMIZATION OF THE PERFORMANCE AND AREA REQUIREMENT OF THE DUPLEX-CW 9.4.1. Type of constructed wetland and arrangement 9.4.2. Water flow operation and configurations 9.4.3. Intensification 9.4.4. Carbon as electron donor for denitrification 9.4.5. Post-treatment for phosphorus removal 9.4.6. Area requirement 9.4.7. Duplex-CW area design in the literature context 9.4.8. Recommended Duplex-CW design 9.5. DEVELOPMENT OF THE CONSTRUCTED WETROOF 9.5.1. Filter material selection and arrangement 9.5.2. Aerobic conditions and effluent quality 9.5.3. Operation under different climate conditions: effect of temperature and rain 9.5.4. Constructed wetroof in the literature context 9.5.5. Recommended constructed wetroof design 9.6. CONCLUSIONS REFERENCES APPENDICES