In waste water treatment, the use of a physico-chemical process by flotation would present some advantages compared to a separation by settling. However like each physico-chemical process, a separation by flotation needs a chemical destabilization. We have studied the use of an electrochemical destabilization coupled to a process of flotation (DAF). This paper presents the results obtained on an urban waste water treated by electrocoagulation and dissolved air flotation (DAF). To show the interest of coupling flotation and electrocoagulation, we have studied each process separately. Then we have combined the two processes. The role of each operation on pollution removal is presented. An effect of synergism between the two processes on the pollution abatement is shown. A reduction of 75% of the global COD is obtained. The results of the coupling are compared to the performance of an intensive treatment by flocculation-lamellar settler.

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The aim of the paper is to compare two optical methods (UV spectrophotometry and laser granulometry) for a better knowledge of the behaviour of wastewater suspended solids. The first one, based on UV spectrophotometry, is used for the estimation of solids concentration and nature in water and wastewater with the help of an advanced exploitation method of UV spectra. But the interpretation of UV spectra, in presence of a very wide size distribution of solids is not always easy, because of the different phenomena responsible of light diffusion. The second method, more classical, allows to characterise the size distribution of particles.

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In this paper, the authors present an electrochemical treatment associated to flotation. They want to show that microfiltration can be used in waste water treatment. For this, they have studied the coupling electrocoagulation - flotation, and they have studied the influence of this association on the flux of permeate in microfiltration. The conclusion of this work is that the combination of the three processes is a possible alternative to an extensive treatment in coastal areas. Moreover it is a compact process with which they have obtained a water of a quality suitable for irrigation.