Naslov
Flocculation as a Treatment Method of Printing Ink Wastewater

Autori
Meteš, Azra ; Koprivanac, Natalija ; Glasnović, Antun

Izvornik
Water Environment Research (1061-4303) 72 (2000), 6; 680-688

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
flocculation; printing ink wastewater; water reuse

Sažetak
In order to find a suitable method for treatment of printing ink wastewaters, the fundamental behaviour and characteristics of two kinds of model flexographic printing ink wastewaters have been studied. Differences between these two kinds of prepared wastewaters were due to the use of different kinds of binders/resins and pigments and the different solvent contents in real printing inks. The basic ecological parameters confirmed that the model wastewaters were too highly loaded with organic substances for discharge, and were not biodegradable. The model systems also showed some colloidal properties of their dispersions. Such properties were strongly influenced as pH was decreased, which caused neutralization of the negative electrical charges of the particles, resulting in their aggregation. Therefore, the present study was focused on optimization of flocculation, caused by flocculant addition, as the process for destabilization of the dispersions. Inorganic electrolytes were shown to be more efficient flocculants than chosen organic polyelectrolytes, which addition even in very small quantity caused extensive neutralization of particle charges and consequent floc formation. The optimal flocculant concentration was determined on the basis of electrokinetic (zeta) potential (ZP/mV) and turbidity (NTU) measurements. The effect of mixing on flocculation for these dispersion systems was investigated in a two liter, square, baffled tank having a turbine impeller with six blades. The best combination of the mixing intensity, expressed as the mean mixing velocity gradient (G), and time of mixing (t) was investigated and the optimum Gt product, GtOPT=4.45×104, was determined using NTU values of supernatant water and sedimentation velocity of obtained flocs as criteria for flocculation efficiency. Flocculation was shown as a very simple and efficient treatment, from an economic and technical point of view. It was capable of removing the substantial part of the organic content, and of completely removing the colour and turbidity.

Izvorni jezik
Engleski

Znanstvena područja
Kemijsko inženjerstvo

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