CONSTRUCTED WETLANDS FOR NITRIFICATION AND DENITRIFICATION Joan García and Catiane Pelissari Jornada Tècnica InSiTrate Els nitrats a l aigua subterrània. Noves solucions per a un problema pendent 7 th, April, 2016
www.gemma.upc.edu
CONTENT 1. General concept 2. Classification 3. Active elements in the treatment 4. Removal of nitrogen 5. Limits 6. Possibilities
Concept 1. Constructed Wetlands - CW Plants Design Water Applied load Microorganisms Performance Wetlands Constructed Wetlands
Concept Constructed Wetlands - CW Consolidated Technology; Different types of wastewater; Low cost; Primary, secondary and tertiary treatment;
Classification 2. Constructed Wetlands - Classification Free Flow CW Subsurface Flow
Classification Free Flow Construced Wetlands - FWS Source: ucnfanews.ucanr.edu/
Classification Horizontal Flow Constructed Wetlands - HF 1- Influent, 2- Macrophytes, 3- Liner, 4- Inlet zone, 5- Feeding system, 6 -Filling media, 7- Flow, 8 -Outlet zone, 9 Collection system, 10 -Level controller.
HF - Construction Classification
Classification Vertical Flow Constructed Wetlands - VF 1- Influent, 2- Macrophytes, 3- Filling media, 4- Feeding system, 5- Flow, 6- Collection system, 7- Liner, 8-Level controller, 9 - Effluent.
VF - Construction Classification
Verdú, Spain Horizontal subsurface flow wetlands (secondary treatment) Urban wastewater, 2000 PE
Fenny Compton, UK Horizontal subsurface flow wetland (tertiary treatment) Urban wastewater, 208 m 3 /d
Bouletèrnere, France Vertical subsurface flow wetland (secondary treatment) Urban wastewater, 1500 PE
Granollers, Spain Free water surface wetland (tertiary treatment)
Elements 3. Active elements in the treatment Macrophytes Uptake nutrients Transfer of oxygen Microorganisms Microorganisms Transformation processes Filling media Adsortion Filtration Biofilm development
Source:MOEHDANO, 2015 Elements
Nitrogen removal 4. Nitrogen removal in constructed wetlands Macrophytes uptake ~5 to 10 % of N load influent, NH 3 -N or NO 3 - N Low Biochemical transformations by microorganisms High Adsorption Microbial assimilation Low Low 18
Macrophytes uptake Nitrogen removal Adsorption Biochemical transformations Microbial assimilation Nitrification: O 2 C Denitrification: C O 2 C/N Ratio: C/N Nitrification Denitrification : C/N ratio exceeding 6 to achieve complete denitrification Saed and Sun (2012)
Limits 5. Limits of nitrogen removal in CW Nitrification Denitrification Denitrification Nitrification Nitrification Denitrification
Possibilities 6. Possibilities for nitrogen removal in CW 1- Hybrid systems VF- HF HF- VF VF- HF - FWS
1- Hybrid systems Possibilities Vymazal (2013) 60 hybrid constructed wetlands from 24 countries on Europe, America and in Asia VF-HF systems HF-VF systems VF-HF-FWS Multistage hybrid systems consisting of VF and HF beds in various combinations Load Removal: 2.31 ± 2.10 g TN m -2 d -1 2.74 ± 1.86 g TN m -2 d -1 4.24 ± 5.12 g TN m -2 d -1 3.48 ± 3.93 g TN m -2 d -1
Rural lodging Southern Brazil ~ 70 people/day BOD 5 : 289 mg L -1 TN : 68 mg L -1 NH 4 -N : 42 mg L -1 P: 18 mg L -1 VF - 56 m 2 BOD 5 : 20 mg L -1 TN : 12 mg L -1 NH 4 -N : 2 mg L -1 P: 6 mg L -1 HF - 20 m 2
2 - Recirculation Possibilities
3 - Tidal Flow Possibilities Influent Aggregate cation exchange capacity CEC = 4.0 meq/100 g AIR AIR Effluent Adsorption of ammonium cations (NH 4+ ) in bulk water to aggregate Tanner et al, 1999 Austin, 2006 Rapid oxygen saturation of biofilms in the drained phase Rapid bacterial nitrification of adsorbed NH 4 + cations Desorption of NO 3 - & NO 2 - anions Denitrification of NO 3 - & NO 2 -
Austin, 2006 3 - Tidal Flow Possibilities Pilot: 5 cells (6 12 cycles per cell per day) ~ 2.0 m 3 d -1 (dried cheese whey, urea prills, horse manure, and well water) OLR = ~ 81 g BOD 5 m -3 d -1 Removal: 13 g TKN m -3 d -1 15 g TN m -3 d -1 Effluent concentration: ~ 1 mg L -1 of NH 3 -N ~ 15 mg L -1 of TN
4 - Partially saturated vertical flow Possibilities Nitrification Nitrification + Denitrification
Urban wastewater Southern Brazil VF 7 m 2 0.75 m unsaturated VF Saturated 7 m 2 0.35 m unsaturated 0.40 m - saturated Source : GESAD GROUP
4 - Partially saturated vertical flow - Urban Wastewater - Surface: 3140 m 2 - Operation: 30 days feed and 30 days rest - Filling media: Sand 30 cm free 20 cm saturated Source : GESAD GROUP
4 - Partially saturated vertical flow Bacterial identification through Fluorescence and in situ Hybridization technique Influente 0.10 m gravel 0.50 m sand 0.10 m gravel Effluent 0.20 m saturation Upper Layer (0.0 to 0.17 m) Intermediate Layer (0.17 to 0.34 m) Semi-saturated Layer (0.34 to 0.51 m) Saturated Layer (0.51 to 0.68 m)
joan.garcia@upc.edu