Nature-based solutions - Sustainable water management

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Activated sludge, SBR, MBR

Technological plants based on biological treatment guarantee efficient removal of organic and nitrogen loads with reduced areal footprint; on the other hands, these technologies are characterised by high operational and management costs in comparison to extensive nature-based solutions, such constructed wetlands, as well as specialized personnel.

IRIDRA propose compact technological solutions (activated sludge, SBR, and MBR) every time the available lands for a WWTP are not enough to implement natural solutions. On the basis of the morphological area, the availability of land and the wastewater typology, IRIDRA can propose a combination of technological solution for secondary treatment and constructed wetlands for tertiary treatment.

More information

Constructed Wetlands vS conventional technological solutions - Investment and O&M costs

Investment costs of constructed wetland (CW) systems are usually comparable with those of conventional technological solutions (e.g. activated sludge) up to the threshold of 2000 PE; above this value, scale effect leads to less investment costs for compact technological solutions. On average,and on the basis of our Italian Experience, investment costs for CW is about 100 €/mq of net surface; this is only an indicative value, since they can vary according with different water quality standards to be met, type of used CW system, WWTP size, and local material costs. For instance, the investment costs for small settlement can reach up to 150-200 €/mq. 

 costi di realizzazione  web

Comparison among investment costs of CW and activated sludge WWPTs on the basis of Italian experience (IRIDRA's analysis published in Masotti, 2009)

Operational and Maintenance (O&M) costs are significantly lower for nature-based solutions in comparison with activated sludge systems, due to the almost negligible costs of consumed energy. Usually, O&M costs of CW for wastewater treatment is on average equal to 14 €/PE per year (even lower if french systems for raw wastewater treatment are adopted, and equal to 7-8 €/PE per year), therefore about 5-10 less than O&M costs for activated sludge systems (50-100 €/PE per year). Moreover, CW WWTPs do not require specialized and permanent personnel to be maintained, reducing, even more, the O&M costs.

costi di gestione   1  web

Comparison of energy consumption for different conventional and nature-based treatment technologies (Kadlec&Wallace, 2009)

costi di gestione   2  web

O&M cost comparison between CW and activated sludge WWTPs on the basis of Italian experience (IRIDRA's analysis)

jesi planimetrico  web

Satellite view of the CW system for tertiary treatment of the Jesi WWTP (AN, Italy - 60.000 AE), designed by IRIDRA; source Google Earth (2013)


Kadlec R.H., Wallace S.D. (2009), “Treatment wetlands – Second Edition”, Lewis, Boca Raton.

Masotti L. (2009), Depurazione delle acque, Calderini.