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Optimization and reduction of water consumption in surface treatment processes

a speech by O. Balestrino


The presentation aims to highlight the evolution of the environmental approach over the years by the legislator and propose some technical solutions for the optimization and reduction of water consumption in surface treatment processes.

designs, builds, maintains water and wastewater treatment plants.Specialized in the Treatment and Finishing sector

Development of “Environmental Consciousness” in Italy and Europe

  • Legge 319/1976 (Legge Merli)
  • D.lgs 152/2006
  • 2019: “Industria 4.0”
  • 2022: DNSH

The Merli law indicated in detail the polluting substances, placing limits on their discharge into water and their concentration. With reference to discharges, the distribution of the same for the purposes of the relative regulations and the consequent sanctioning treatment was based on their origin; it was also established that unloading carried out in the absence of the necessary authorization, granted exclusively to unloading in compliance with the limits of acceptability, was always subject to a criminal sanction.

Legislative Decree 152 of which an important section is dedicated precisely to the protection of water from pollution and the management of water resources.

Industry 4.0 / Environment

Water treatment plants included in group 2 Annex A of the materials admitted to transition 4.0, or systems for quality and sustainability assurance, with particular reference to the following two categories :

  • components, systems and intelligent solutions for the management, efficient use and monitoring of energy and water consumption and for the reduction of emissions
  • filters and treatment and recovery systems for water, air, oil, chemicals, dust with signaling systems of filtering efficiency and the presence of anomalies or substances alien to the process or dangerous, integrated with the factory system and able to warn operators and / or to stop the activities of machines and plants

European Green Deal

The central pillar of Next Generation EU is the Recovery and Resilience Facility which, among other objectives, aims to support interventions that contribute to implementing the Paris Agreement and the United Nations Sustainable Development Goals, in line with the European Green Deal.

Objective “Zero pollution” for an environment free of toxic substances

Do No Significant Harm

The Do No Significant Harm principle (DNSH) states that the actions outlined in national NRRPs may not cause any significant harm to the environment: this is a fundamental principle for accessing funding from the RRF.

In addition, the plans must include actions which contribute 37% of the resources to the ecological transition.

The DNSH principle is based on the provisions of the “Taxonomy for Sustainable Finance” adopted to promote private sector investment in green and sustainable projects and help achieve the goals of the Green Deal.

Criteria of DNSH
The Regulation identifies six criteria for determining how each economic activity substantially contributes to protecting the ecosystem, without undermining any of the environmental goals

1   Climate change mitigation

 An economic activity must not lead to significant emissions of greenhouse gases (GHG)

  Climate change adaptation

 An economic activity must not have an increased negative impact on the current and future climate, on the activity itself or on people, nature or property

  Sistainable use and protection of water and marine resources

An economic activity must not be detrimental to the good health of water bodies (surface, groundwater or marine) or harm its quality or reduce its ecological potential

  Transition to the circular economy, including waste prevention and recycling

 An economic activity must not result in significant inefficiencies in the use of recovered or recycled materials, increase the direct or indirect use of natural resources, or significantly increase waste or the burning or disposal thereof, causing significant long-term environmental damage

5   Prevention and reduction of air, water and soil pollution

An economic activity must not cause increased emissions of pollutants in the air, water or soil

6   Protection and restoration of biodiversity and health of ecosystems

An economic activity must not harm the good condition and resilience of ecosystems or the conservation status of habitats and species, including those of interest to the Union.


A specific technical annex of the Taxonomy sets out the parameters for evaluating whether different economic activities substantially help with climate change mitigation and adaptation or whether they cause significant harm to one of the other goals. Based on the Statistical Classification of Economic Activities in the European Community (NACE), the activities that can help to mitigate climate change are then determined, identifying the sectors that are crucial for an effective reduction in pollution. The framework defined in the Taxonomy therefore provides a reliable guide for making sustainable investment decisions, and has become a core component of the criteria for allocating European resources

C24 – Manufacture of basic metals

   C24.4.1 – Precious metals production

C25 – Manufacture of fabricated metal products, except machinery and equipment

   C25.6.1 – Treatment and coating of metals


«Zero pollution» for an environment free of toxic substances

Sistainable use and protection of water and marine resources 

 An An economic activity must not be detrimental to the good health of water bodies (surface, groundwater or marine) or harm its quality or reduce its ecological potential

Prevention and reduction of air, water and soil pollution

An economic activity must not cause increased emissions of pollutants in the air, water or soil

DNSH in F.T.

Low impact plant design

  • Use of low toxicity products
  • Design of efficient systems
  • Reuse and recovery of solutions
  • Zero liquid discharge


Water reduction

The design of the washing system is linked to:

1. Process

a) Characteristicsof the process solution

b) Numbers of rinsing

c) Type of rinsing

2. Production

I. Surface

II. Final goal

Importance of rinsing: Water reduction

A cascade rinsing allows a strong reduction of the necessary water flow and as a first approximation we can say that the concentration in the washes Xn



The Zero Liquid Discharge can use different technologies and design philosophies but the key point is the last link which is almost always an evaporation-concentration system.

The evaporator-concentrator is a system that allows you to concentrate diluted solutions by eliminating / recovering water.

The main uses are :

1. Recovery of diluted solutions to be reused as process solutions

2. Reduction of disposal with water recovery



There are different technologies of evapo-concentrators:

Heat pump

  with immersed coil

  forced circulation

  with scraper

Hot water

  single effect

  double effect

  triple effect

Mechanical Vapour Recompression

1. Natural circulation

2. forced circulation

3. falling film

a) With lobe compresso



The reduction of water consumption, up to the extreme point of Zero Liquid Discharge, in the surface treatment processes pursues “the goal of zero pollution for an environment free of toxic substances“

Operating costs with the appropriate techniques can be very advantageous.