Energetic, environmental and economic challenges (ES1202)


The increasing demand by citizens and environmental organisations for cleaner waters led the European Commission to define water protection as one of its priorities. The Water Framework Directive (WFD) adopted in 2000 (2000/60/EC) is the legal tool for future water protection, in which the achievement of a "good status" for waters concerning both ecological and chemical quality is targeted. Additionally, the sustainable use of water resources in terms of quality and quantity is highlighted, which is related to an adequate water pricing.

Wastewater Treatment Plants (WWTPs) are key stakeholders affected by these new water policies, as they are responsible for urban and industrial effluent treatment before discharge into the aquatic environment. This implies that the new challenges during the conception, design, upgrading and operation of WWTPs have to be conditioned to the current and future legal, economical and social requirements.

Since 1914, when the activated sludge process was developed, all efforts were mainly devoted to increase effluent quality. However, current aims have to be much broader, including not only those related with water and sludge quality but also considering: i) Resource recovery alternatives; ii) Energetic and Economic efficiency; iii) Impact on climate change due to the emission of Greenhouse Gases (GHG); iv) Fate of emerging contaminants and v) Odorous contamination.

According to recent communications from the European Commission other issues directly related to the future of water treatment include: water scarcity and droughts (COM/2007/0414); the higher amounts and levels of wastewater treated due to the implementation of the Urban Waste Water Treatment Directive (91/271/EEC); the inclusion of priority substances as target pollutants (plant protection products, biocides, metals, Polyaromatic Hydrocarbons (PAH) and Polybrominated Biphenylethers (PBDE), pharmaceuticals and endocrine disruptors, etc.); the awareness on the contribution of sewage treatment on climate change.

Water industry is especially concerned about the important energy consumption during WWT, with around 1% of the average daily electricity consumption in Western Europe due to municipal and industrial WWT. However, wastewater can be a source of both thermal and chemical energy, enabling the recovery of substantial amounts of energy during collection and treatment. This offers a significant economical benefit, as currently energy costs account for up to 40% of the operational cost of WWTPs.