Cuoiodepur – A filter between mankind and the environment

Since as far back as 1980, when it was founded, Cuoiodepur has relentlessly invested in research, technology, expertise, human resources and training in order to ensure leading edge purification procedures of the first order. Cuoiodepur stands out today as an efficient facility endowed with advanced technological resources for treatment, and as a major benchmark for the sector’s experts and other operators. 

Over the last decade or so, the wastewater treatment plant has evolved into a virtuous example of applied “circular economy”, specifically as regards management of the sludge, originating in treatment of the tannery wastewaters, which after a drying step and mixing with other ad hoc products of tanning origin, are transformed into a fertilizer.

Cuoiodepur SpA is a non-profit concern run by the consortium (with public and mainly private share capital). Its corporate purpose is construction, extension and management of the centralised purification facility located in località S. Romano, in the municipality of San Miniato (Province of Pisa). Its function is the processing of industrial wastewater and sewage; construction and management of facilities for the re-use and/or disposal of the waste materials generated by purification; and construction and management also of similar or linked facilities for removal of pollutants from the lands of the municipality, Comune di San Miniato, and of neighbouring lands.

A complex computerized system enables control and management of the various treatments of the waters line and sludge line. The various data − functionality of processes and of the key monitoring parameters; quantities of effluents discharged by companies; and monitored emissions, for control of environmental impacts − are processed and displayed in real time.

The facility built in the early 1980s and the more recent extensions currently provide a potential processing capacity of 850,000 in population-equivalence terms; processing of up to approx. 1,800,000 m³/year of industrial wastewater; and 1,500,000 m³/year of sewage from the neighbouring urban areas of San Miniato and Montopoli Val d’Arno.

Advanced, synergically linked physico-chemical and biological processes are implemented in order to remove the organic load (in terms of the COD), with performance standing at approx. 96-97%. Mean removal of nutrients, respectively nitrogen and phosphorus, stands at 95% and 99% of the input load.

From an environmental and economical point of view, a major consideration regards re-use of tannery sludge that would have otherwise been merely waste material. Instead, a virtuous conclusion has been attained for the entire tanning process, maximizing the principle “from waste to product”, thus minimizing the costs − both environmental and economic – of the production chain as a whole. The sludge produced by the wastewaters, mainly deriving from vegetable tanning, due to its characteristics, is particularly suitable for re-use for agricultural purposes. 

Several studies and monitoring activities – both lengthy and complex – led at last to a specific product known as Pellicino integrato – i.e. an organic nitrogenous fertilizer with high content levels of organic carbon and nitrogen (approx. 20% and at least 4%, respectively). This product has been approved and included in the national list of fertilizers, in accordance with the legislative decree, D.Lgs 75/2003.

Over the years, Consorzio Cuoiodepur has engaged in major R&D activities, now improved and concretizing during execution of projects aimed at finalizing reconfiguration of the process, for enhanced environmental and economic efficacy, accompanied by optimal energy efficiency. Furthermore, in regard to sludge management, the project has more recently turned its attention to the principle of recovery of both energy and materials (rather than materials alone). 

These activities and results are the concrete outcomes of work at the Laboratorio Congiunto CER2CO (Centro Ricerche Reflui Conciari) (laboratory engaging in tannery effluents research). The work, ongoing for more than ten years, is managed by the environmental and civil engineering department of the University of Florence (Dipartimento di Ingegneria Civile ed Ambientale dell’Università di Firenze).

The water purification processes and their efficiency shall also be significantly enhanced by completion of the current extension work − the fruit of a supplementary agreement regarding water management of the zones, Basso Valdarno and Padule di Fucecchio, by reorganisation of purification in the leather industry district and in the Empolese, Valdera, Valdelsa and Val di Nievole area (Accordo Integrativo per la tutela delle risorse idriche del Basso Valdarno e del Padule di Fucecchio attraverso la riorganizzazione della depurazione del Comprensorio del Cuoio e del Circondario Empolese, della Valdera, della Valdelsa e della Val di Nievole). 

Within this ambit, early next year, an MBR (biological membrane) treatment plant shall become operational. It is dedicated solely to purification of sewage. This plant will enable recovery of water for re-use within the plant as well as, in part, for re-use by the tanneries, as soon as the new industrial water supply system is activated.