A microbe-based value chain: TREatment and valorisation of texTILE wastewater

Il “sistema” depurativo del Distretto Tessile di Como The wastewater treatment “system” of the Como Textile District Giovanni Bergna LARIANA DEPUR SpA

Evento Finale _Webinar 3 giugno 2021 The Como Textile District In the Como area there is an important textile district with several small or medium textile firms.

The fibres processed are mainly synthetic, silk and cotton. Typical of Como area are textile finishing processes.

This area is served by centralised wastewater treatment plants treating domestic and industrial wastewater. Most of the pollution load is industrial.

Evento Finale _Webinar 3 giugno 2021 WATER: a competitiveness and sustainability factor

For the textile finishing sector, the water resource is a competitive factor and a strategic resource and is therefore the object of particular attention.

Evento Finale _Webinar 3 giugno 2021 Short story

In the mid-1970s to face the problem of water pollution, the public bodies and industrial associations of Como sign an agreement for the construction and management of the wastewater treatment system: private companies for WWTPs and public consortia for sewerage, are established;

At the end of the 1970s the WWTPs come into operation to treat domestic and industrial wastewater;

Evento Finale _Webinar 3 giugno 2021 The Como case: the industrial water service The industrial wastewater collected by the sewage system is equal to about 25% of the urban ww in the entire area of Como, but in some basins it reaches over 50% of the treated volume. The water supply system The wastewater treatment system Current users of the The plants, the sewerage networks and the Users Industrial Aqueduct constitute the wastewater treatment system of the consume about 5 million m³ textile District. of water per year for industrial use.

Evento Finale _Webinar 3 giugno 2021 WASTEWATER DISCHARGE LIMITS INTO THE SEWER improve the system by centralizing the treatment In the Como textile district, as in many other areas, the discharge limits into the sewer for industrial wastewater have been determined with values higher than those required by law, first by Law 319/76 then by Legislative Decree 152/06 . For example, the following limits are envisaged in the Lariana Depur basin: Basin pH SST COD BOD Total Surfactants Color Discharge Nitrogen limits mg/l mg/l mg/l mg/l mg/l dilution 5,5÷9,5 400 2500 1500 100 100 1:100 This choice made it possible to discharge the production wastewater as it is into the sewer and treat it in the centralized plant. In this way: • the construction of company treatment plants was avoided; • economies of scale and greater efficiency have been achieved; • investments have been concentrated on centralized ww treatment plants.

6 Evento Finale _Webinar 3 giugno 2021 What has been guaranteed In the Como textile district, the development of water services in agreement between the companies and public bodies with attention to the needs of production activities, has allowed:

• preservation of natural resources and the environment; • optimization in the use of the natural and economic resources of the district; • development of productive activities and economic growth; • access to the water service at an affordable cost for the companies.

Evento Finale _Webinar 3 giugno 2021 TEXTILE WASTEWATER CHARACTERISTICS

The textile industry is characterized by a significant environmental impact due to a significant use of chemical compounds and a high water consumption that gives rise to large volumes of highly polluted wastewater.

• highly variable composition according to type of fiber, chemical products and processes adopted; • high contents of recalcitrant and toxic / inhibitory compounds (surfactants, dyes, detergents, solvents, heavy metals, chelators, oils, ...); • intensely colored wastewater.

Evento Finale _Webinar 3 giugno 2021 CRITICAL ISSUES OF TEXTILE WASTEWATER

Color • important visual impact even at low concentrations; • expressed as "not perceptible with 1: n dilutions“; "Biologically refractory" COD • 20-40% of the total COD; • dyes, surfactants, complex molecules, ...; Surfactants • 30-80 mg / l, mostly non-ionic; • biological treatment is not enough; Nitrogen • High concentrations especially in textile printing (100-500 mgN / l); • Low COD /Nitrogen ratio.

Evento Finale _Webinar 3 giugno 2021 TREATMENTS PERFORMANCE

Biological treatment: • “Biologically refractory'' COD removal: 30% COD input (bio-adsorption, trapping of the particulate in the flock); • Removal of color (45%) and total surfactants (75%); • Removal of nitrogen and part of the phosphorus; Coagulation-flocculation treatment: • Refractory COD removal: 20%; • Marginal removal of color (5%) and total surfactants (5%); • Phosphorus removal (depending on coagulant dosages); Ozonation treatment: · • Refractory COD removal: 5-10% inlet; • Color removal: 25-30%; • Total surfactants removal: 15-20%.

Evento Finale _Webinar 3 giugno 2021 ALTO WASTEWATER TREATMENT PLANT

The plant is located close to the Seveso river east of the inhabited area of , extending south of the road Fino-Casnate to the wooded area of the “ Val Mulini ". The environmental characteristics of the site are those pre-eminently represented by an agricultural landscape, cut out within partly wooded areas, punctuated by building signs of recent interventions in the industrial and civil sectors.

Evento Finale _Webinar 3 giugno 2021 BLOCK Linea acque DIAGRAM Rimozione Grigliatura Sollevamento materiale grossolana iniziale Stacciatura Dissabbiatura lapideo OF ALTO Arrivo Trattamenti preliminari SEVESO liquame

PLANT Ossidazione Sedimentazione Denitrificazione biologica finale

Trattamenti biologici Ozonolisi The urban waste water treatment plant was Coagulazione Chiarificazione completed in 1978, Flocculazione a pacchi Ozonazione partially renovated and lamellari Torrente Trattamenti terziari upgraded in 1984, Seveso 1987-1989, in 1996 and 2008. Linea fanghi

Disidratazione Ispessimento con centrifughe Smaltimento fanghi

Evento Finale _Webinar 3 giugno 2021 ALTO SEVESO WWTP

SLUDGE TREATMENT TERTIARY TREATMENTS 1998 1998

PRE-TREATMENTS BIOLOGICAL TREATMENT 2008 1978 – updated 1984, 1987 e 1996

Evento Finale _Webinar 3 giugno 2021 DIGITAL TEXTILE PRINTING - DTP IN COMO TEXTILE DISTRICT

In about ten years, digital printing has gone from 2% of total production to the current 60-65% (estimated to reach 85% within five years).

In the Como district, the adoption of digital printing is one of the responses to the difficulties in the textile sector linked to the global crisis.

In the district there are not only textile printing companies, but also manufacturers of digital printing machines and inks.

Evento Finale _Webinar 3 giugno 2021 NITROGEN: A NEW PROBLEM

Evento Finale _Webinar 3 giugno 2021 NITROGEN DISCHARGE LIMITS REGULATION

Italian national legislation on water is Decree 152/06 which also defines the discharge limits to the environment and to the sewer system. The regulation issued by the Region (Regulation n°. 6/2019) specifies these limits considering the entire regional territory as sensitive area. Decree 152/06 Como Textile District D.lgs 152/06 Discharge limit Water service regulation + RR 06/19 into Sewer Sewer River N total mg/l 54 100 10 - 15

Derogation to the limit of 100 mg/l granted by the in case of need for the production process. Possible limitations in case of non-compliance with the discharge limits from centralized WWTP or from the sewer network in rainy periods.

Evento Finale _Webinar 3 giugno 2021 THE NITROGEN AMOUNT FROM DTP IN COMO TEXTILE DISTRICT WASTEWATER

• 158 textile finishing (dyeing and printing) factories; • the discharged volume from the textile finishing factories exceeds 7.8 million m3/year, discharging about 525 tN/year, and 80% of the total amount of nitrogen discharged by industrial activities in the district; • 49 printing and finishing factories which adopt or partially adopt DTP, discharge their wastewater in public sewers, containing nitrogen compounds at a concentration exceeding 50 mgN/l; • the discharged volume from these 49 factories (less than one third of textile finishing factories) exceeds 3 million m3/year, accounting for about 412 tN/year, and about 63% of the nitrogen from the total industrial discharges;

Evento Finale _Webinar 3 giugno 2021 POTENTIAL USERS OF PRE-TREATMENT TECHNOLOGY FOR N REMOVAL IN COMO TEXTILE DISTRICT

Firms Vi CODi Ni COD N n° m3 mg/l mg/l kg/a kg/a TOT.Textile N>200 8 541.184 577 276 312.374 149.450 28 Users TOT.Textile N>150 15 956.410 680 233 649.967 222.721 16% of Volume TOT.Textile. N>100 28 1.686.503 634 184 1.070.003 310.712 47.6% of N TOT.Textile N>50 49 3.104.039 640 133 1.985.343 412.717

TOTAL Textile 158 7.884.049 609 67 4.803.214 524.768 TOTAL 514 10.831.823 646 60 6.993.976 653.168 14 Users Firms Vi CODi Ni COD N n° m3 mg/l mg/l kg/a kg/a 13% of Volume TOT.Textile N>100 + V>100.000 m3/y 6 925.879 636 197 588.429 182.447 41.3% of N TOT.Textile N>100 + V>50.000 m3/y 14 1.450.919 575 186 833.878 270.353 TOT.Textile N>100 + V>15.000 m3/y 22 1.661.690 633 185 1.052.200 307.069 22 Users TOT.Textile N>100 28 1.686.503 634 184 1.070.003 310.712 15% of TOTAL Textile 158 7.884.049 609 67 4.803.214 524.768 Volume TOTAL 514 10.831.823 646 60 6.993.976 653.168 47.0% of N

Evento Finale _Webinar 3 giugno 2021 CONCLUSION a new paradigma for the Textile Como District The increasing attention to the environment and to the consequences of our behavior on the future of the planet, also translated into increasingly restrictive limits for wastewater, requires to articulate the paradigm of centralizing water treatment by evaluating the opportunity of specific treatments on industrial site to:

• optimization more and more the use of the natural and economic resources; • improve the sustainability of textile production; • achieve zero-pollution and circular economy goals.

Evento Finale _Webinar 3 giugno 2021 Partners:

Giovanni Bergna [email protected]

Progetto finanziato da:

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