WASTEWATER TREATMENT

The treatment of tanning wastewater has always been a matter of the utmost  importance within the Tuscany Leather District, because of its environmental and economical impacts.

The sustainability of the whole tanning process strictly depends on the performances of the  wastewater treatment and, as a consequence of this, within the tanning district on the right bank of the river Arno,  were built three different wastewater treatment plants (WWTPs):

1. Fucecchio
2. Santa Croce sull'Arno
3. Castelfranco di Sotto

Consorzio Aquarno was the managerial company of the plant established in Santa Croce sull'Arno, the biggest in the District,  but after subsequent administrative and practical reorganisations, Aquarno has become the only manager of the municipal and industrial wastewater treatment on the right bank  of the river Arno.

On July 2013, Aquarno aquired the control of the plant in Fucecchio while, the one in Castelfranco di Sotto, is still operated by another company, however its discharge stream flows to Aquarno.

Santa Croce sull'Arno centralized plant, thanks to its treatment capacity of about 2.050.000 E.I. ( Equivalent Inhabitants), is one of the biggest WWTP in Europe. It covers an approximative land surface of 2km² where 42 basins of different capacities from 100 to 15.000m³, are distributed. The WWTP provides the cleansing of both industrial and municipal wastewater incoming from three different municipalities, to do this the plant has got two different treatment sections:

1. Municipal wastewater section
2. Industrial wastewater section

As a consequence of great differences among qualities and quantities of the two streams, also the wastewater treatment sections are very different, with regard to dimensions and typologies of processes involved.

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ANALYTICAL LABORATORY

Consorzio Aquarno manages several processes, that require intensive and continuous controls, because of the number and variety of monitoring parameters. This kind of heterogeneity, together with the impossibility to determine directly on-field all parameters with specific probes, need the intervention of an analysis laboratory.

Many years have passed since Consorzio Aquarno has solved this issue thanks to the construction of an internal laboratory which satisfy most of the analytical necessities of the monitoring system.

In 2010 the laboratory has been completely modified and transferred in a new bigger location. New instruments and modern accessories have been installed improving the analytical efficiency and increasing the number of parameters self monitored by Aquarno.

Besides the WWTP's indicators, the new analytical laboratory also provides useful analysis for the control of Ecoespanso and Consorzio Recupero Cromo processes, which are recently felt under  Aquarno's supervision.

In order to overcome the heterogeneity among monitored parameters the three plants, further modern instruments for the analysis of new kinds of samples, have been implemented.

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EXCESS SLUDGE TREATMENT

Conventional wastewater treatment processes, biological ones as well as physico-chemical ones, produce huge amounts of excess sludge, that represent the main waste of the whole water cleansing process.

The term "sludge" refers to a particular matrix whose composition depends on the native WWT process, but which can be classified into two main groups:

• biological sludge - high content of organic matter (usually expressed as %VSS)
• physico-chemical sludge - high content of inorganic matter ( low value of %VSS)
  

Aquarno WWTP produce both kinds of sludges, but the biological one prevails due to the "Tutto Biologico" process; nevertheless the most concerning issues related to sludge are their quantities and their disposal.

In order to answer to these problems in 2001 a new plant under the control of the company Ecoespanso, was expressly constructed for the treatment of sludge produced by the three WWTPs on the right bancks of the river Arno : Fucecchio, Santa Croce sull'Arno  and Castelfranco di Sotto.

On July 2014 also Ecoespanso became  a branch of Consorzio Aquarno, this new oganization enabled further optimization of all processes thanks to the synergic and systematic interaction between the two plants. 

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