ELECTRODIALYTIC VALORISATION OF SEWAGE SLUDGE AND ITS ASHES – POTENTIAL OF PHOSPHORUS RECOVERY P. GUEDES 1,2 , N. COUTO 1,2 , E. MATEUS 2 , L.M. OTTOSEN 2 , ALEXANDRA B. RIBEIRO 1 1 CENSE, Departamento de Ciências e Engenharia do Ambiente, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829 ‐ 516 Caparica, Portugal. 2 Department of Civil Engineering, Technical University of Denmark, DK ‐ 2800, Lyngby, Denmark CYPRUS 2016 - 4th International Conference on Sustainable Solid Waste Management, Limassol, 23–25 June 2016
PROBLEMATIC Phosphorus (P) is a macronutrient indispensable for plant growth. EU is almost entirely dependent upon imports, from China, Jordan, Morocco, South Africa and USA controlling 85% of global phosphate reserves1. 1 Smit, A.L., et al., 2009, Plant Research International B.V., Wageningen, Report 282. Image credits: Jen Christiansen (map and graphs); Source: U.S. Geological Survey, Mineral Commodity Summaries, January 2009.
WASTEWATER TREATMENT PLANTS destroys organic contaminants, Sewage Incineration pathogens while promoting mass sludge reduction 90 ‐ 95% P Organic contaminants Sewage Heavy metals Sludge P not bioavailable Ash P bioavailable rich in P Heavy metals Dioxins
TECHNOLOGY ELECTRODIALYTIC PROCESS Aims to remove contaminants (e.g. heavy metals) from fine porous matrices under the influence of an applied low level direct current Anode (eq.) Cathode (eq.) 2H 2 O ‐ 4e ‐ → O 2 + 4H + 2H 2 O + 2e ‐ → H 2 + 2OH ‐ Patent PCT/DK95/00209
AIM Electrodialytic process (ED) 1 sewage sludge Contaminants removal 2 sewage sludge ashes P-recovery
SEWAGE SLUDGE ASHES HEAVY METALS & PHOSPHORUS ‐ Guedes P, Couto N, Ottosen LM, Kirkelund GM, Mateus EP, Ribeiro AB (2016) Valorization of ferric sewage sludge ashes: potential as a phosphorus source, Waste Management, 52, pp. 193 ‐ 201, DOI: 10.1016/j.wasman.2016.03.040 ‐ Guedes P, Couto N, Ottosen LM, Ribeiro AB (2014), Phosphorus recovery from sewage sludge ash through an electrodialytic process, Waste Management, 34(5), pp. 886 ‐ 892, DOI: 10.1016/j.wasman.2014.02.021
SSA SAMPLING Denmark, Lynetten incinerator, Copenhagen : fresh SSA ‐ immediately after the incineration process o deposited SSA ‐ from the deposit o
SSA DIFFERENCES Fresh ash Deposited ash Fresh vs Deposited Statistical differences (p<0.05) o pH; Conductivity; Water content; Loss on ignition; Solubility in water o Elements Concentration: Al, Zn, Cu (attributed to SSA heterogeneity)
ED CELLS 3C ‐ cell 2C ‐ cell Matrix compartment: central Matrix compartment: anode Acid suspension H 2 SO 4 + stirrer Electrolyte: closed system Ion exchange membranes
EXPERIMENTAL DESIGN Constants: Current (50 mA) o Variables: SSA (fresh, deposited) o Cell set ‐ up (3C, 2C ‐ cell) o Acid concentration H 2 SO 4 (0.08, 0.19 M) o N.º exp. 12 (n=1) o
HM REMOVAL % of HM removal (7 days) 0.08 M 0.19 M Lowest (%) Examples (%) Lowest (%) Examples (%) cell SSA Fe/Pb Cd Cu Zn Fe/Pb: Cd Cu Zn fresh 6/2 70 69 62 9/14 82 69 56 3C deposited 6/2 64 40 69 12/10 82 76 73 fresh 10/7 18 55 64 6/12 23 69 53 2C deposited 12/9 23 44 51 8/14 27 64 51 Removal → Time dependent o Best approach → 3C ‐ cell, H 2 SO 4 0.19 M o SSA did no influence the results o
P RECOVERY 0.08 M 0.19 M cell SSA % P solubilized % P recovered % P solubilized % P recovered fresh 76 18 91 25 3C deposited 72 19 92 29 fresh 91 77 99 93 2C deposited 67 56 99 97 Higher acid concentration → higher P solubilization o 2C ‐ cell + 0.19M H 2 SO 4 → highest P recovery (anolyte, 93 – 97%) o SSA influenced the results → 2C ‐ cell + 0.08M H 2 SO 4 o
SEWAGE SLUDGE EMERGING ORGANIC CONTAMINANTS & PHOSPHORUS ‐ Guedes P*, Magro C, Couto N, Mosca A, Mateus EP, Ribeiro AB (2015) Potential of the electrodialytic process for emerging organic contaminants remediation and phosphorus separation from sewage sludge, Electrochimica Acta, 181, pp. 109 ‐ 117, DOI: 10.1016/j.electacta.2015.03.167 ‐ Guedes P, Mateus EP, Almeida J, Ferreira AR, Couto N, Ribeiro AB (submitted) Electrodialytic treatment of fresh sewage sludge: Current intensity influence on phosphorus recovery and organic contaminants removal ‐ Guedes P, Rodrigues A, Almeida J, Couto N, Mateus EP, Ribeiro AB (under preparation) Electrodialytic treatment of sewage sludge: Influence on microbiological community
SEWAGE SLUDGE SAMPLING o Portugal, WWTP Quinta do Conde (Águas de Lisboa e Vale do Tejo), Sesimbra o SS from the secondary settling tank
EXPERIMENTAL DESIGN Fresh SS 2C ‐ cell Frozen SS Constants: Cell set ‐ up (best) o Study: Constants: pH: no adjustment o pH: < 2 Phosphorus o Time: 3 days o Time: 5 days o 6 OCs Variables: •Caffeine (Caf) SS o Variables: •Bisphenol A (BPA) Current (mA) o 3 cell set ‐ ups •17 β‐ oestradiol (E2) o 0, 50, 75, 100 o Current (mA) o Current steps •17 α‐ ethinyloestradiol (EE2) o 0, 20, 50 o •Ibuprofen (Ibu) Microbiological control •Oxybenzone (MBPh) N.º exp. N.º exp. 7 (n=2) o 6 (n=2) o + 2 control electrodegradation (25 mA, 6 h, n=2)
MAIN RESULTS: FROZEN SS Cell set ‐ up: Matrix compartment: SS + stirrer o Electrolyte: closed system o Ion exchange membranes o Current influenced P ‐ recovery Highest P ‐ recovery → 78% (anolyte) Best OCs degradation → 71 ‐ 97% (Caf ‐ Ibu)
MAIN RESULTS: FRESH SS OCs degradation improved with current o Higher: 50 mA & 100 ‐ 75 ‐ 50 mA o r 2 = 0.989 % P recovered → current intensity 80 o 70 Current steps did not improve P recovery o 60 %P electrolyte 50 Highest recovery → 70% → 100 mA 40 o 30 20 55% → 24 h 10 0 Control Exp-1 Exp-2 75 Exp-3 0 50 100 I (mA)
CONCLUSIONS
BEST CELL DESIGN SS P+OCs → 2C ‐ cell (cathode+AEM,100 mA) ED SSA P → 2C ‐ cell (anode+CEM, H 2 SO 4 0.19M) HM → 3C ‐ cell (H 2 SO 4 0.19M)
P RECOVERY 40 g of P/ kg (70%, 3d) SS P SSA 125 g of P/kg (97%, 7d)
Lynettefællesskabet (Lynetten incinerator) ACKNOWLEDGMENTS
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