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Decision Support in the Reuse of Sewage Sludge in Agriculture

Decision Support in the Reuse of Sewage Sludge in Agriculture . Aida Valls, Xavier Mercadé , Marta Schuhmacher , Ana Passuello. Universitat Rovira i Virgili, Tarragona, Spain. Contents. The problem : WWTP sewage sludge disposal SMES: Sludge Management Expert System

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Decision Support in the Reuse of Sewage Sludge in Agriculture

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  1. Decision Support in the Reuse of Sewage Sludge in Agriculture Aida Valls, Xavier Mercadé, Marta Schuhmacher, Ana Passuello Universitat Rovira i Virgili, Tarragona, Spain

  2. Contents • Theproblem: WWTP sewagesludgedisposal • SMES: Sludge Management ExpertSystem • Filtering of data • Multi-criteriadecisionprocess • Construction of performance criteria • Aggregation of partialperformacesinto a global score • Visualizationtools • Conclusions

  3. WWTP sewage sludge disposal • Sewagesludge can be appliedtoagriculturalsoilstoimprovetheirquality. • Tokeepsustainability, countries are encouragedto do thisactivity. • Ecological and human impactmust be considered: • metals and organiccompoundsmay be transferredtothesoil, whichmay cause contamination (nitrification) • To determine thebestscenarioforsludgeapplication, a decisionsupportsystemispresented.

  4. Thesystemiscomposedby 4 modules:

  5. Input data • Toassessthosecriteriamany variables havebeenconsidered. Legal maximumlevels

  6. 1. FILTERINGSTAGE REPORT DATE: 2/23/2011 14:03 - - - - - - - - - - - - - - - - FILTERING OF SLUDGES - - - - - - - - - - - - - - - - Sludgedescription: WWTP of NorthArea (ID - S1) >> SLUDGE S1 WITHIN LIMITS!! << Sludgedescription: WWTP in Central Area (ID - S2) - Level of NPE over thelimit (165,0921 mg/kg dw > 50 mg/kg dw). >> SLUDGE S2 REJECTED!! << Sludgedescription: WWTP in EasternArea (ID – S3) - Level of Copper over thelimit (1456 mg/kg dw > 1000 mg/kg dw). - Level of Nickel over thelimit (410 mg/kg dw > 300 mg/kg dw). >> SLUDGE S3 REJECTED!! << Sludgedescription: WWTP of NorthArea (ID – S4) >> SLUDGE S4 WITHIN LIMITS!! << - - - - - - - - - - - - - - - - - FILTERING OF SOILS - - - - - - - - - - - - - - - - - Soildescription: Lettucefields in Lleida (ID - L1) >> SOIL L1 WITHIN LIMITS!! << ... • European legal regulations on the amount of chemical and organic contaminants that are present in each sludge and soil samples. • Sludge or soils above the limits are discarded from the rest of the analysis. • A reportisgenerated. REPORT DATE: 2/23/2011 14:03 - - - - - - - - - - - - - FILTERING OF SLUDGES - - - Sludgedescription: WWTP of NorthArea (ID - S1) >>

  7. 2. MCDA. Thefamily of criteria • Criteriahavebeenorganizedhierarchically. • At thefirstlevel, 3 groups are distinguished: • Economicalissues Costsderivedfromtheapplication, transport and management, and profitsfor non usingotherfertilizers • Environmentalimpacts Ecologicalimpactonsoil and groundwater (GW) contamination • Human healthrisks Social impact and consequenceson human healthduetodirectexpositionoringestion of pollutants

  8. The family of criteria

  9. Depend on the interactions between some soil and sludge properties Two types of criteria • Simple criteria (S): g:  [0..10] • Compositecriteria (C): g:  ...  [0..10]

  10. Simple criteria

  11. Compositecriteria • Theperformace score is a consequence of thecombination of soil and sludgeproperties (orother variables) • Interactionsbetweenseveral variables must be properlymodeled • Weproposedto use FuzzyExpertSystems Valls, A., Schuhmacher, M., Pijuan, J., Passuello, A., Nadal, M., Sierra, J., Preference assessment for the management of sewage sludge application on agricultural soils, International Journal of Multicriteria Decision Making, Indersicence Publishers, ISSN (Print): Vol1. No1. pp 4-24. 2010

  12. A fuzzyexpertsystemapproach • Rules are usedtomodelthedependenciesbetweenthegroups of variables • Linguistic variables permittomodeluncertainty • Theproperties of eachalternative are introducedintothefuzzyexpertsystem • Rules are activated and a conclusionisobtained, regardingthe performance of thealternative

  13. Input linguistic variables

  14. Output linguisticvariable for performance evaluation

  15. A fuzzyexpertsystemapproach

  16. 2. MCDA. AggregationLogicScoring of Preferences (LSP) • ProposedbyJ. Dujmovic (1973) • Performance scores are aggregated in a compositionalwayfollowingthehierarchy of criteria • Differentlogicaloperators can be chosen at eachaggregationpoint • Aggregation method based on continuous preference logic (CPL) • Simultaneity (andness), Replaceability (orness), Mandatory requirements and Sufficient requirements

  17. LSP aggregation operators

  18. Conclusions • The SMES system analyses the physical and chemical properties of the sludge and the soil in order to calculate the degree of suitability of each case study, taking into account that some soils are more suitable to receive some kind of sewage sludge than others. • A combination of different techniques has been used to solve the problem. • Some criteria related to territorial information are included in the multi-criteria analysis. • The SMES software is being developed by Microart S.L. (Barcelona, Spain).

  19. http://deim.urv.cat/~itaka http://www.sostaqua.com

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