Constructed wetlands for tertiary treatment

IRIDRA Fitodepurazione per trattamenti terziari

Constructed wetlands are usually adopted as nature-based solutions for tertiary treatment of centralised activated sludge WWTPs, for instance, due to either an increase of served town or more stringer water quality standard for discharge. Particularly, constructed wetlands are used for tertiary treatments to either provide denitrification or guarantee the effluent wastewater quality standard under variable peak influent loads. They are also used to exploit additional ecosystem services, such biodiversity increase and recreation of areas with a high naturalistic value.

High treatment efficiencies in terms organic and nutrient loads
High pathogen removal
Simple construction and functioning
Simple maintenance
Almost negligible OPEX in comparison to conventional systems (no or almost negligible energy consumption)
Neither odour issues, mosquito proliferations, nor aerosol
No use of chemical compounds
No need for specialised personnel

Tertiary treatment - IRIDRA's solutions

Classical constructed wetlands

  • Constructed wetlands with horizontal subsurface flow (HF)
  • Constructed wetlands with free water surface (FWS)
  • Hybrid constructed wetlands (HF + FWS)

Intensified constructed wetlands (Constructed wetlands 2.0)

  • Aerated constructed wetlands (FBA™)

Integrated additional solutions

  • Wetland restoration

Constructed wetland for tertiary treatment

Several application of constructed wetland for tertiary treatment are known worldwide. For instance, UK counts more than 200 applications in this field. The most representative Italian case is the tertiary treatment of Fusina WWTP: a free water surface system of 100 hectars, treating 4000 m3/h and fully integrated in the Venice lagoon. Another relevant Italian example is the tertiary stage of Jesi WWTP (60,000 PE), designed by IRIDRA: the system is composed by a sedimentation basin, an horizontal subsurface flow systems (10,000 m2) and a free water surface system (50,000 m2), aimed to improve the denitrification and the pathogen removal of the WWPT (Masi, 2008).

terziari jesi  web

Tertiary constructed wetland of the Jesi WWTP (60.000 AE), designed by IRIDRA

IRIDRA progetto Trattamento terziario del depuratore di Jesi (AN)

Tertiary treatment of Jesi WWTP (AN - Italy)

Treated person equivalent : 60.000 PE

Chosen Nature-based solution : HF + FWS

Year of realization : 2002

The municipal centralised treatment plant (a classic activated sludge technology) for the wastewater produced by the municipality of Jesi (Ancona province – central Italy) has been upgraded in the year 2002, with the realisation of a new “nitrification-denitrification” compartment and a hybrid constructed wetland as polishing stage. The whole system treats about 18000 m3/d (more than 60000 p.e.) and a part of the effluent is reused in a nearby industrial area. All the new sections have been provided with an online monitoring system, in order to reduce as much as possible the energy consumption for the denitrification process leaving more role to the final wetland whenever it obtains sufficient performances. The upgraded WWTP is operating since January 2003; after the first year of operation a good development of the macrophytes communities has been observed. The hybrid constructed wetland system consists in a first sedimentation pond with a volume of 2000 m3, a 1 hectare horizontal Submerged Flow System (HF) and finally a 5 hectares Free Water System (FWS). The accumulated sludge in the sedimentation basin are periodically pumped in a wet woodland planted with Populous alba.
IRIDRA progetto per Trattamento terziario del depuratore di Acerra (NA)

Tertiary treatment of Acerra WWTP (NA - Italy)

Treated wastewater quantity : 3000 m3/day

Chosen Nature-based solution : FWS

Peculiarità : Demonstration plant with high naturalistic value. To this aim, up to 13 different plant species were designed to be placed (e.g. Iris pseudacorus, Carex spp, Lythrum salicaria, Botumus umbellatus)

Year of design : 2014

IRIDRA progetto per Trattamento terziario depuratore del campeggio in località Chiarore-Graticcia, Capalbio (GR)

Tertiary treatment of WWTP serving a camping in Chiarore-Graticcia, Capalbio (GR - Italy)

Treated person equivalent : 1200 PE

Chosen Nature-based solution : HF

Year of realization : 2014

The camping is located along the seaside, in a very environmentally sensitive region near to the Burano wetland (a WWF protected area). The camping guests up to 1200 persons during the peak season. The Constructed wetland, 2200 m2 horizontal flow system, permits to postreat the effluent of an activate sludge plant, ensuring adequate denitrification and refining organic and suspended solid concentration
IRIDRA progetto per Trattamento terziario depuratore di Caraglio (CN)

Tertiary treatment of Caraglio WWTP (CN - Italy)

Treated person equivalent :  7000 PE

Chosen Nature-based solution : FWS

Year of design : 2016

The WWTP of Caraglio municipality (7000 a.e.) treats the wastewater with a secondary activated sludge system (SBR). In order to guarantee a more constant removal efficiency of the WWTP under time-variable influent loads, a tertiary stage with free water surface (FWS) constructed wetland (CW) was designed by IRIDRA. The FWS treats an average wastewater flow of 1400 mc/day and has a surface area of 2100 mq. The FWS was designed with different water depths (from 0.4 to 1.2 m), creating environments suitable for the placement of different type of vegetations.
IRIDRA progetto per Trattamento terziario depuratore di Trigolo (CR)

Tertiary treatment of Trigolo WWTP (CR - Italy)

Treated person equivalent : 1900 PE

Chosen Nature-based solution : FWS

Year of design : 2010

IRIDRA progetto per  Trattamento terziario del depuratore di San Casciano dei Bagni (SI)

Tertiary treatment of San Casciano dei Bagni WWTP (SI - Italy)

Treated person equivalent : 2000 PE

Chosen Nature-based solution : HF

Year of realization : 2005

The Municipality of San Casciano dei Bagni in Tuscany, Italy, needed to upgrade its existing activated sludge treatment plant, as the effluent from the plant did not respect the limits imposed by the current law (L. 152/99) and caused problems of eutrophication in the river and the lake receiving the effluent. So in 2005 IRIDRA managed a project of constructed wetland and chose to implement a horizontal subsurface flow system
IRIDRA progetto per Trattamento terziario del depuratore di Volongo (CR)

Tertiary treatment of Volongo WWTP (CR - Italy)

Treated person equivalent : 1000 a.e.

Chosen Nature-based solution : HF

Year of design : 2012

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