Environmental performance of a municipal wastewater treatment plant
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Goal, Scope and Background
Nowadays, every strategy must be developed taking into account the global impact on the environment; if this aspect is forgotten, a change of environmental loads or their effect will be caused and no reduction will be attained. For instance, a wastewater treatment plant (WWIP), which is considereda priori as an ecological treatment system, gives rise to an environmental impact due to its energy consumption, use of chemical compounds, emissions to the atmosphere and sludge production, the post-treatment of which will also have diverse environmental effects. The goal of this study is to evaluate the potential environmental impact corresponding to a municipal WW1P and to identify the hot spots associated with the process.
In this study, the Centre of Environmental Science (CML) of Leiden University methodology has been considered to quantify the potential environmental impact associated with the system under study. A comprehensive analysis of the WWTP was evaluated for the physico-chemical characterisation of the wastewaters as well as the inventory of all the inputs (energy, chemical compounds, ...) and outputs (emissions to air, water, soil and solid waste generation) associated with the global process. Regarding Life Cycle Inventory Assessment, SimaPro 5.0 was used and in particular CML factors (updated in 2002) were chosen for characterisation and normalisation stages.
Results and Discussion
A comprehensive inventory of empirical data from water, sludge and gas flows during 2000 and 2001 was obtained. Two impact categories arise due to their significance: eutrophication and terrestrial ecotoxicity. Consequently, the aspects to be minimised in order to reduce the environmental impact of the system are the pollutant load at the watercourse discharge (mainly NH3, PO4 [3- and COD, even when all of them are below legal limits) and the emissions to soil (mainly Cr, Hg and Zn, even when they are present in low concentrations) when the sludge is used for agricultural application.
As far as the environmental impact is concerned, differentiation between humid and dry season is not required as results are practically equal for both situations. Water discharge and sludge application to land have turned out to be the main contributors in the environmental performance of a WWTP. Regarding the former, the removal of nitrogen by means of a nitrification-denitrification system coupled to conventional biological aerobic treatment implies a high environmental impact reduction and, as for the latter, bearing in mind the proposed legislation, heavy metals as well as pathogens are supposed to be the key parameters to define the most adequate treatment strategies for the generated sludge.
Recommendations and Outlook
This study can serve as a basis for future studies that can apply a similar policy to a great number of wastewater facilities. Besides, features such as different treatment systems and capacities can provide additional information with the final aim of including the environmental vector in the decision-making process when the operation of a WWTP is intended to be optimised. Moreover, sludge must also be a focus of attention due to the expected increase and its major contribution to the global environmental impact of a WWTP, which can determine other treatment alternatives.
KeywordsDenitrification ecotoxicity eutrophication life cycle inventory (LCI) sludge wastewater wastewater treatment plant (WWTP)
- Tillman AM, Svingby M, Lundstrom H (1998): Life Cycle Assessment of municipal waste water systems. Int J LCA 3 (3) 145–157Google Scholar
- Suh YJ, Rousseaux P (2001): Considerations in Life Cycle Inventory analysis of municipal wastewater treatment systems. Oral presentation at COST 624 WG Meeting, BolognaGoogle Scholar
- APHA-AWWA-WPCF (1985): Standard Methods for examination of water and wastewater. WashingtonGoogle Scholar
- Vilas-Cruz M, Gómez J, Méndez R, Lema JM (1994): Determinatión simultánea de NO2-y NO3- en aguas residuales por electroforesis capilar. III International Symposium of Analytical Methodology for the Environment, Vol. H, BarcelonaGoogle Scholar
- NIST, National Institute of Standards and technology (1995): NIST SRM 2781 Dried Domestic Sludge. United States Government Printing Office, WashingtonGoogle Scholar
- Real Decreto 1310/1990, de 29 de octubre, por el que se regula la Utilización de los Lodos de Depuratión en el Sector Agrario. BOE 262/1990Google Scholar
- PRé Consultants (2001): SimaPro5 Manuals: Database Manual Methods. AmersfoortGoogle Scholar
- Ullmann F (1997): Ullmann’s Encyclopedia of Industrial ChemistryGoogle Scholar
- IDAE: Instituto para la Diversification y Ahorro de la Energia. http://www.idea.esGoogle Scholar
- BUWAL250 (1996): Ökoinventare für Verpackugen. BernGoogle Scholar
- Henze M, Harremoes P (2000): Wastewater treatment: Biological and chemical processes. Springer, BerlinGoogle Scholar
- Hannigan M. (2003): Sources of air pollution. Oral presentation at Air Pollution Controls Course, ColoradoGoogle Scholar
- ISO (2000): ISO 14000. Environmental Management. GenèveGoogle Scholar
- Guinee JB, Gorreé M, Heijungs R, Huppes G, Kleijn R, de Koning A, van Oers L, Weneger A, Suh S, Udo de Haes HA, de Bruijn H, van Duin R, Huijbregts M (2001): Life Cycle Assessment: An operational guide to the ISO standards. LeidenGoogle Scholar
- Potting JMB (2000): Spatial Differentiation in Life Cycle Impact Assessment. A Framework, and Site-Dependent Factors to Assess Acidification and Human Exposure. PhD Dissertation by University of UtrechtGoogle Scholar
- Mattson J, Avergård I, Robinsson P (1991): Priority pollutants, heavy metals and main constituents in the domestic sewage from two residential areas in Gothenburg. Vatten 47, 204–211Google Scholar
- Lindqvist-Östblom A, Sörme L, Söderberg H (2001): Substance flow analysis as a tool to support environmental management of heavy metals in wastewater treatment companies, Oral presentation at Economic growth, material flows and environmental pressure at Folkets Hus in StockholmGoogle Scholar
- Hospido A, Martin M, Rigola M (2003): Comparison of sewage sludge disposal scenarios using life cycle assessment. Oral presentation at Environment 2010: Situation and Perspectives for the European Union, PortoGoogle Scholar