Drawbacks & Opportunities of Electrocoagulation Technology in the Wastewater Treatment

Transcription

1 EMC 2007, June 11-14, Düsseldorf Germany Drawbacks & pportunities of Electrocoagulation Technology in the Wastewater Treatment J. Rodriguez, S. Stopić, B. Friedrich IME Process Metallurgy and Metal RWTH Aachen University, Germany Prof. Dr.-Ing. Bernd Friedrich

2 World Water Supply Saltwater 97.5% Freshwater 2.5% Source: WH Total available for anthropogenic consumption is less than 0.007% 68.9% Glaciers 30.8% Groundwater 0.3% Lakes and Rivers

3 World Water Use [Km 3 /a] 4000 In 2020, 17% more water than is available will be required to feed the world Reservoir losses Industry Domestic Agriculture [Year] Source: FA Aquastat

4 Competing Water Uses A compromise concerning Sustainable Water Reuse Practices must be found 100% 22% 10% 8% 80% 60% 8% 59% 69% 85% 40% 70% 11% 9% 82% 20% 0% World 30% 22% High-Income Europe 11% 4% Low- Germany & Mid-Income Source: UNEP Agriculture Domestic Industry

5 Predicted World Water Scarcity & Stress in % of world s population do not have access to adequate sanitation (2.64 B.) 20% do not have sustainable access to safe drinking water (1.0 B.) 80% of all diseases in developing countries are related to water Source: UNEP Scarcity Stress Water-borne diseases kill more than 25,000 people on a daily basis, from them a child every 8 seconds

6 Lack of Efficiency in Industrial Wastewater Treatment p Mn (++) Ni (++) Zn (++) Cu (++) Cr (+++) (+++) Fe (+++) Discharge ph ph useful for NaH ph with first precipitation Extended ph using lime or soda ash Admissible ph for discharge Some heavy metals like Manganese (Mn), force the precipitation process to go over the neutral range in order to achieve their removal

7 Wastewater Treatment using a Precipitation Line Pump Stirrer Storage tank Reactor 1 Reactor 2 Reactor 3 ph meter Product tank

8 Hydroxide Precipitation of Copper Production Effluents Before treatment with sodium hydroxide NaH: Cu = 50 mg/l = 13 mg/l Mn = 6 mg/l ph = 4.3 9,5 8,4 Concentration [mg/l] Cu = 34 mg/l = 12.3 mg/l Mn = 5.5 mg/l Cu = 0.9 mg/l = 0.4 mg/l Mn = 3.3 mg/l NaH + HCl Cu = 0.9 mg/l = 0.3 mg/l Mn = 0.1 mg/l NaCl 7,3 6,2 ph [-] ,3 5, ,5 0,9 0,4 3,3 0,9 0,3 0,1 15min + 15min + 15min 00:00 15:00 30:00 45:00 ph=5.7 ph=7.3 ph=9.3 Time [min] 4,0 Cu [mg/l] [mg/l] Mn [mg/l] ph [-]

9 Proposed Electrocoagulation Mechanism 2 ( ) 6 3+ H 2 (H) 2 ( ) H 3 + = H H 3 + H + + 2H H 3 + Hydrolysis, Condensation & Complexation H H 2 (H) 2 ( ) (H) 12 ( ) (H) 22 ( ) (H) 60 ( )

10 Absorption Principle of uminium Hydroxide M n+ M n+ H 24 (H) H H H H H H H M n+ Water M n+ H H H H M n+ M n+ -Hydroxide absorbed cations

11 Wastewater Treat. using an Electrocoagulation System Conditioning EC-Reactor Conductivity ph meter Filtration Power meter Power supply Data acquisition

12 Electrocoagulation Treat. of Copper Production Effluents ,5 40 8,4 Concentration [mg/l] Before Cu = mg/l No NaCl in treated effluents, enabling water reuse = 0.57 mg/l 7,3 Mn = 0.97 mg/l treatment with -hydroxide: Cu = 50 mg/l = 13 mg/l Mn = 6 mg/l ph = No need for Cu complete = 0.09 mg/l neutralization, 22,2 Cu = 22.2 since mg/l there is no = 0.6 disposal mg/l required = 5.5 mg/l Mn = 1.4 mg/l Mn = 4.9 mg/l + 5min + 5min ph= min ph=5.1 5,5 ph=4.8 4,9 0,09 0,6 1,4 0,009 0,57 0,97 00:00 05:00 10:00 15:00 6,2 5,1 4,0 ph [-] Time [min] Cu [mg/l] [mg/l] Mn [mg/l] ph [-]

13 Hydroxide Precipitation vs. Electrocoagulation 1,5 11 EUR/m EUR/m Concentration [mg/l] 1,2 0,9 0,6 0,3 4.8 kwh/m 3 2 kwh/m m 3 /y 526 m 3 /y ph = 9.3 ph = ,0 Chemical Precipitation Electrocoagulation Copper uminium Manganese

14 SWT Analysis Hydroxide Precipitation Neither a fast nor a cost-effective technology S Very simple Very simple dosage process Expensive material W Suitable for effluents Effective option for very acidic industrial wastewaters Expensive material raw (NaH), which certainly influences treatment process (<1 mg/l) Suitable for effluents with low ph values Environmental T Environmental concerns due to neutral salty effluents after treatment Not suitable for sustainable development

15 SWT Analysis Electrocoagulation Reliable fast & cost-effective technology Low energy demand per cubic meter & best metal removal at higher flow rates (0.09 mg/l Cu) Low energy demand S W May require external Higher efficiencies Best option for the majority of industrial wastewaters May require external ph conditioning for some effluents Higher efficiencies regarding material raw usage and disposal cost Uncertainties as regards renewable energy resources required to drive the EC-process Uncertainties as T Suitable for sustainable development

16 Lack of Efficiency in Municipal Wastewater Treatment Mechanical Treatment Influx Sand removal Sedimentation Chemical Treatment Biological Treatment xidizing beds Aerated filters Membrane reactors Chemical Treatment Phosphorous removal Nitrogen removal Disinfection 2 (S 4 ) (H) S 4 Electrocoagulation 2 ( ) e (H) 2 ( ) H 3 Normal Municipal Effluents Eutrophicated Excess of nutrients as Phosphor and Nitrogen causes Eutrophication

17 Electrocoagulation Treatment of Municipal Wastewater Phosphor rtho-p and suspended solid TSS removal up to 100%, as well as over 50% organic loads removal like CD, TC, TNb; providing a sustainable methodology for municipal wastewater treatment and agricultural water reuse rtho-p = 4,3 mg/l TSS = 500 NTU CD = 572 mg/l TC = 166 mg/l TNb = 41.1 mg/l NH 4 -N = 28.9 mg/l Before 100% 80% 60% 40% 20% 0% verall Removal Rates [%] Treated Effluents 41.3 Electrocoagulation 29.1 rtho-p TSS CD TC TNb NH 4 -N After rtho-p < 0.05 mg/l TSS < 1 NTU CD = 251 mg/l TC = 97.5 mg/l TNb = 19.4 mg/l NH 4 -N = 20.5 mg/l

18 Conclusions Sustainable Water Reuse Practices After Hydroxide Precipitation Lack Eutrophicated of nutrients Salty effluents No marketable sludge After Electrocoagulation No salty effluents Marketable Sludge Healthy Non-Treated Regular Tap Effluents Water Effluents after EC-process Improved Higher metal separation removal of rates organic without matter increasing without the contamination content of neutral of residual sludge, salts, resulting enabling sustainable greater water water reuse reuse opportunities practices and while improved providing costefficiencies to waste due to management material raw cycles usage and clean avoidance energy of production disposal better support fees

19 utlook Sustainable Water Management Concept Water Cycle Wastewater Electricity Biogas Sludge Iron Commune Municipal Wastewater Basic Needs Water Reuse Electrocoagulation Biological Treatment Waste Management Iron Ferromagnetic Separation Metal Clean Energy Electricity Biogas Sludge Water Cycle Electrical Grid Biogas Combustion Biogas Production Fertilizers

20 Acknowledgements ptimizing ptimizing Energy Energy Use Hydrolysis Electrical Engineering Chemical Engineering EC Electro- coagulation Electrolysis Precipitation Promoting Promoting Sustainable Sustainable Development Development Process Engineering Sixth Framework Programme Improving Wastewater Treatment

21 EMC 2007, June 11-14, Düsseldorf Germany Thank you for your attention. IME Process Metallurgy and Metal RWTH Aachen University, Germany Prof. Dr.-Ing. Bernd Friedrich