Life Cycle and Economic Analyses of the Removal of Pesticides and Pharmaceuticals from Municipal Wastewater by Anodic Oxidation
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-03-25 |
| Journal | Sustainability |
| Authors | Elena Surra, Manuela Correia, SĂłnia A. Figueiredo, Jaime Gabriel Silva, Joana Vieira |
| Institutions | Universidade Nova de Lisboa, Universidade de Vigo |
| Citations | 16 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis analysis assesses the sustainability of implementing an Anodic Oxidation (AO) unit as a tertiary treatment for Pesticide and Pharmaceutical (PP) removal at a full-scale Municipal Wastewater Treatment Plant (MWWTP), comparing Boron-Doped Diamond (BDD) and Mixed Metal Oxide (MMO) anodes.
- Environmental Burden of PP: The presence of PP in the MWW effluent contributes significantly to existing environmental burdens, accounting for 85% of Human Carcinogenicity and 90% of Freshwater Toxicities (ReciPe2016/USEtox).
- AO Operation Impact: Implementing the AO unit increases the overall environmental burdens of the system by 95% on average (USEtox), primarily due to the high electric energy consumption required for electrooxidation.
- Mitigation via Cogeneration: The existing biogas cogeneration unit at the WWTP is crucial, as the renewable electricity produced partially compensates for the indirect environmental burdens associated with AO unit operation.
- Electrode Environmental Trade-off: BDD anodes are environmentally more favorable than MMO anodes. However, the manufacturing of MMO anodes introduces significant toxicity burdens (e.g., Sulfidic Tailing from metal extraction) that often surpass the environmental benefits of PP removal.
- Economic Viability: MMO configuration is clearly more advantageous economically, yielding a positive Net Return (NR) and an acceptable Payback Period (PbP) of 10.26 years.
- BDD Economic Barrier: The high purchase cost of BDD anodes renders this configuration economically unviable, resulting in a Total Capital Investment (TCI) more than 10-fold higher than MMO and a negative Net Return.
- Integrated Solution Required: Effective PP management requires an integrated approach combining upstream reduction of PP use/disposal and the adoption of energy-intensive removal technologies strongly supported by dedicated renewable energy sources.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| WWTP Average Flow | 23,100 | m3/day | Current operational flow |
| AO Unit Hydraulic Retention Time (HRT) | 2 | h | Design parameter for 70% COD removal |
| Target COD Removal Efficiency (η) | 70 | % | Assumed efficiency for PP removal |
| AO Unit Inlet COD (CODin) | 0.068 | kg O2/m3 | Based on WWTP effluent data |
| AO Unit Outlet COD (CODout) | 0.020 | kg O2/m3 | Calculated based on 70% removal |
| Electric Energy (EE) Consumption | 3.55 | kWh/m3 | Required for AO treatment |
| Specific Energy Consumption | 75 | kWh/kg CODremoved | Conservative value based on pilot scale |
| Current Density (J) | 300 | A/m2 | Fixed parameter for AO design |
| Total Anode Surface (A) | 2019 | m2 | Required surface area for full-scale operation |
| Total Operating Current (I) | 605,754 | A | Calculated based on flow and COD removal |
| Operating Voltage (v) | 5.56 | V | Calculated based on conductivity and J |
| Wastewater Conductivity (”) | 1500 | ”S/cm | Used for voltage calculation |
| Optimum Electrode Spacing (d) | 0.3 | cm | Calculated for proper system operation |
| BDD Anode Cost (Unitarian) | 1.5 | âŹ/cm2 | Commercial cost for small electrode |
| MMO Anode Cost (Unitarian) | 842 | âŹ/m2 | Estimated cost for large-scale application |
| MMO Pt Loading | 50 | g/m2 | Assumed coating density |
| AO Unit Lifetime | 20 | years | Used for depreciation and profitability analysis |
| Minimum Acceptable Rate of Return (mar) | 6 | %/y | Used for Net Return calculation |
Key Methodologies
Section titled âKey MethodologiesâThe sustainability assessment was based on Life Cycle Analysis (LCA) and Economic Analysis, following ISO 14040/14042 standards.
-
Life Cycle Assessment (LCA) Framework:
- Functional Unit: 1 m3 of raw wastewater (influent).
- Impact Assessment Methods: ReCiPe2016 Endpoint (H) and USEtox (for ecotoxicity and human toxicity).
- System Boundaries:
- Boundary 1: Liquid phase treatment only (MWW to UV disinfection).
- Boundary 2: Liquid and solid phase treatment, including biogas cogeneration for electric energy production (avoided burdens).
- Avoided Burdens: Included partial re-use of treated water and avoided production of non-renewable electricity via biogas cogeneration.
-
Anodic Oxidation (AO) Unit Design and Operation:
- Reactor Design: Three sheltered reinforced concrete tanks (total capacity 2500 m3) equipped with 67 anode-cathode pairs.
- Performance Assumption: AO unit achieves 70% removal efficiency for COD and PP, based on pilot-scale data (Urtiaga et al., Popescu et al.).
- Cathode Material: Stainless steel (79.25 t/y).
-
BDD Anode Manufacturing (CVD):
- Substrate: Titanium plates.
- Deposition Technique: Chemical Vapor Deposition (CVD).
- Reactive Gases: Methane (1% CH4 in H2) doped with Trimethyl Boron (1-3 ppm).
- Scale-up: Gas flows and energy consumption were scaled up using a geometrical factor (1.01E+07) based on the ratio of full-scale to lab-scale anode area.
-
MMO Anode Manufacturing (Thermal Decomposition):
- Substrate: Titanium plates/wires.
- Coating Process: Painting with an MMO solution (assumed Pt oxides) followed by thermal treatment at 400 °C.
- Thermal Treatment Scheme: Multi-step heating (130 °C for water evaporation, 250 °C for adhesion, final calcination for metal oxide formation).
-
Economic Analysis:
- Methodology: Based on Timmerhaus and Peters (Delivered Equipment Method).
- Key Metrics: Total Capital Investment (TCI), Total Annual Treatment Cost (TTC), Return of Investment (ROI), Payback Period (PbP), and Net Return (NR).
- Revenue Assumption: Revenues derived only from public taxes for MWW treatment and sale of cogenerated electric energy to the national grid.
Commercial Applications
Section titled âCommercial ApplicationsâThe research directly addresses the implementation of advanced electrochemical processes in large-scale municipal infrastructure, focusing on the material science and economic viability of electrode selection.
- Wastewater Treatment (Tertiary): Implementation of Anodic Oxidation (AO) as a final polishing step to remove persistent organic pollutants (PPs) that bypass conventional biological treatment.
- Electrochemical Advanced Oxidation Processes (EAOPs): Commercial deployment of BDD and MMO electrodes for the degradation of bio-refractory organic waste streams, including landfill leachates and industrial effluents.
- Electrode Manufacturing: High-volume production of dimensionally stable anodes (DSA), specifically:
- BDD Electrodes: Used where high current efficiency, chemical stability, and low fouling are critical, despite high capital cost (e.g., specialized industrial effluent treatment).
- MMO Electrodes: Used for large-scale, cost-sensitive applications like chlorine alkali production and water electrolysis, now being adapted for wastewater treatment due to lower TCI.
- Sustainable Infrastructure Design: Providing data for engineers and policymakers to integrate renewable energy sources (like biogas cogeneration) directly into energy-intensive treatment processes to meet sustainability goals.
View Original Abstract
Several pesticides and pharmaceuticals (PP) have been detected in the effluent of a full-scale Portuguese Wastewater Treatment Plant (WWTP). Their presence contributed to the environmental burdens associated with the existing treatment of the Municipal Wastewater (MWW) in the impact categories of Human Carcinogenicity, Non-Carcinogenicity, and Freshwater toxicities on average by 85%, 60%, and 90%, respectively (ReciPe2016 and USEtox methods). The environmental and economic assessment of the installation of an Anodic Oxidation (AO) unit for PPsâ removal was performed through Life Cycle and Economic Analysis, considering two types of anodes, the Boron-Doped Diamond (BDD) and the Mixed Metal Oxides (MMO). The operation of the AO unit increased the environmental burdens of the system by 95% on average (USEtox), but these impacts can be partially compensated by the avoided the production of non-renewable energy in the Portuguese electricity mix by biogas cogeneration at the WWTP. If the construction of the AO unit and the manufacturing of the electrodes are considered, the Human and Freshwater Toxicities are often higher than the environmental benefits derived from the PPsâ removal. On the economic side, the MMO configuration is clearly more advantageous, whereas BDD is environmentally more favorable. The issue of the presence of PP in MWW effluents has to be addressed as an integrated solution both improving upstream PPâs management and adopting PPâs removal technologies strongly supported by renewable energies. Further insights are needed for the assessment of fate and of the environmental effects of PP in the sludge.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
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