INNOVATIONS: PRESENT&FUTURE
PURAL® ZEROZERO: a second generation ZLD wastewater treatment (with no evaporator and without the formation of liquid sludge) Franco Falcone San Zenone al Lambro, Milano, Italia
franco.falcone@cieeng.com
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© ipcm ®
IE Srl is a company specialising in the can be applied to both horizontal and design and installation of purification vertical aluminium coating systems. systems for the wastewater of However, the treatment is facilitated in pre-treatment, coating, anodic oxidation and aluminium finishing processes. This firm (Fig. 1) has been a pioneer in the Zero Liquid Discharge (ZLD) water treatment technology. The surface attack that occurs during a pre-treatment process for preparing aluminium to coating is relatively limited: about 1 or 2 gr/m2 of metal are removed, both with chrome-based and with more modern chrome-free systems. That is why the concentration of chemicals, salts, pollutants and metals in the rinsing water is relatively low. The ZLD technology 1 was initially developed for the purification of pre-treatment Figure 1: Franco Falcone, the founder of CIE Srl. water precisely because it is a less difficult process. The first system of this type was installed at the vertical ones because the dragging the All.co plant of Pisa (Italy) in 1992. Over of pre-treatment water from one process fifty plants have followed, up to the most phase to another is limited, compared with recent ones installed at the premises of horizontal lines. Metra in Brescia (Italy) and in Canada. CIE Srl The remarkable development of this is now a world leader in the zero discharge technology has been due to two main industry, with a percentage of installed factors: the increasingly frequent use of equipment that exceeds 80% of the total. chrome-free pre-treatment processes Most of these systems are to be found in and the transition from alkaline to acid Italy, Greece, North America and Middle East. chemicals to attack aluminium surfaces. The ZLD wastewater treatment technology These elements have enabled an easier
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development of the ZLD technology, also making it relatively less expensive in terms of both plant cost and management expenses. The absence of chromium in the rinsing water makes it “lighter” and characterised by a lower concentration of salts, while the absence of soda in the baths, and therefore in the water to be treated, facilitates the chemical purification process. Incidentally, these two factors are of benefit not only to the ZLD technologies, but also to the conventional ones. In the water coming from acid-based pre-treatment processes, acids can be neutralised and metals abated, so that there are no more residues after treatment. In the water coming from alkaline-based pre-treatment operations, on the other hand, sodium has to be neutralised; however, it will always be present in small amounts in the treated water. ZLD systems are crucial in countries or at production sites with inadequate availability of water, where the discharge limits are particularly restrictive, and in all the cases in which a more eco-friendly treatment system is required.