Dr. Daniela La Rosa

A surface flow constructed wetland as a A surface flow constructed wetland as a measure to maintain the natural habitat of a measure to maintain the natural habitat of a reserve and a way to reuse wastewatersreserve and a way to reuse wastewaters

G.Siracusa and A.D.La RosaDepartment of Physical and Chemical Methodology forEngineering - University of Catania, Italy

RelatorRelator

Wetlands are considered important earth’s ecosystems which play a key role for the maintenance of natural balances.

According with the Ramsar Convention, wetlands are considered of international importance and therefore they represent a significant component of the collective efforts to safeguard the environment

Sicily

Italy

VendicariSimeto

BeliceBiviere Capo passero

State of the art of wetlands in Sicily

The area under our investigation, called “Simeto’s Oasis”, is located in the east coast of Sicily where the river Simeto (the main Sicilian river) ends

The area was established as reserve in 1984 and includes the remaining wet zones around the Simeto’s river mouth that represents only a little portion of the much wider wetland existing before human action occurred (in the fifties).

The course of the river is of about 113 km

The reserve covers an extension of about 1860 haand includes some of the most important natural habitatfor bird nesting (the riparian vegetation Scirpus lacustris, S

maritimus, Phragmites communis and Typha latifolia.and an important system of dune and back-dune areasrich of a very wide and interesting psammo-halophyte

vegetation

One of the most important purpose of the “Simeto’s Oasis” reserve establishment was the protection and conservation of a wide cane-land used as refugee by thousands of birds for living and nesting

The main attraction of the reserve is its bird population: there are more than 270 species between resident and migratory birds.

Attempts to restore the original biotic community are in progress.

Unfortunately, during the years, a wild anthropic activity (creation of illages and agricultural practice) has occurred causing a threat for the

wildlife

Porphyrio

A study by the National Institute for Wild Fauna isunderway for re-introduction of Porphyrio porphyrio

Environmental impact of human activities

.Drying up of wetlands(low rainfalls, windy zone, land reclamationfor the creation of villages, use of water forirrigation)

causes the leaving of avifauna

waterwaywaterway

. Change of the primary physical-chemicalcharacteristics of the soil due to dune

levelling and to substitution of autochthonous vegetation with

other non- autochthonous coastal woods(acacia, eucaliptus)

Environmental impact of human activities

Eryngium maritimum Juniper

AmberAmber SimetiteSimetite

the the mostmost beautiful, beautiful, preciousprecious and rareand rarein the worldin the world

OurOur studystudy

In the past the area was used to partially discharge the untreated urban wastewater during summertime with an high impact due to the nutrients carried.Plants and animal species have been developing since then becoming more and more used to that environment.

Wastewater treatment plant discharge

At present, since the building of the wastewater treatment plant, the effluent is discharged into the watershed JungettoThe effluent waters, after crossing the reserve area, reach the sea and are totally

t d

2. The water flow from the treatment plant is 54.000m3/d and the Jungetto basin is not capable to collect all the waters, especially during heavy rains so that floods are very frequent.

Main consequences of the activation of the treatment plant:

1. Change of the nutritive balance (reserve habitats wereused to receive a huge amount of nutrients from the wastewaters

As a possible solution to avoid floods the authorities are planning to build an underground pipe in order to deviate he water flow and to discharge directly into the sea

Underground pipe

DebrisDebris accumulationaccumulation

LackLack of of nutrientsnutrients

WasteWaste of waterof water

ProposalProposal of of interventionintervention

Construction of a lagoon both as a tertiary treatment systemand as a basin to collect part of the effluent waters coming from the treatment plant

advantages

Water purificationWetland restorationWater reuse

It consist of a complex system of biofitodepuration whichcould be easily implanted in the area. It requires a 0.5-0.7 mdeep pond where wastewaters, after preliminary treatments,can be purified by living organisms

Proposal of intervention

The practice of lagooning (free water surfacewetland) to store partially treated wastewaters in a coastal zone.

Design criteria and calculations

Use of the Reed method to calculate the area of a free water surface cw considering the BOD removal

A = [Q* ln(Ci/Co)]/ KT * d* nv

A = wetland treatment area (m2)Q = influent wastewater flow (m3/d)Ci = influent pollutant concentration at wetland inlet (mg/l)Co= effluent pollutant concentration at wetland outlet (mg/l)d = water depth in wetland (m)nv = void ratio or porosity corresponding to proportion of typical

wetland cross section not occupied by vegetation

KT = K20 Θ (Tw –20)

KT = rate constant corresponding to water temperature in wetland (d-1)K20 = rate constant at 20°C reference temperature (d-1)Tw = wetland temperature (°C) Θ = temperature coefficient for rate constant

For first-order kinetic, constant values at 20°C (K20) and temperature coefficient (Θ) depend on the pollutant removal. For BOD removal K20 = 0.678 d-1 and Θ = 1.06

A = [Q* ln(Ci/Co)]/ KT * d* nv

Wetland temperature Tw is a fundamental parameter for the designer because the removal of BOD and the various nitrogen forms are temperature dependent. Winter temperatures correspond to lower reaction rates and should be used in the design calculations. The calculation of winter watertemperature was carried out through an iterative routine applied to the following expressions:

Tw = 14°C; Rn = ρ*λm*ET + Ha

ET= Ke*[Pw sat(Tw) - Pwa(T)]Ha = convective transfer to air (MJ/m2/d)ET = water lost to evapotranspiration (m/d)Rn = net radiation reaching the ground (MJ/m2/d)λm = latent heat of vaporization of water (MJ/kg) = 2453 MJ/kg at 20°Cρ = density of water kg/m3

PenmanPenman MethodMethod

Q = 54000 m3/dCi = 35 mg/l (mean value calculated from table 1 data) Co = 20 mg/ld = 0.5 m;nv = 0.75Tw = 14°C; KT = 0.678 * (1.06) (14-20) = 0.478A = [54000 * ln(35/20)]/(0.478)* (0.5)* (0.75) = 165690 m2

detention time t = (nv* d* A)/Q = 1,25 days

OurOur ApplicationApplication

The construction of a lagoon as tertiary treatment system in thereserve requires a land area of 16.5 ha

Into the lagoon, the effluent waters coming from the near wastewater treatment plant, would be purified thanks to the plants activity.

Phragmites australis (reed grass) is an autochthonous species very common in the area. Plant density should be of 4.4 rhizomes/m2.

The presence of the lagoon in this degraded area could contribute to wetland restoration and rehabilitation

The lagoon would be located in the pre-reserve area (B) which contains entirely abusive villages and is destined to agricultural practice.

The treated waters could be used for irrigation or for industrial requests or discharged into the reserve, when necessary, in order to keep the hydrological balance unaltered.