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Wastewater from olive oil mills has been treated by means of the Fe(II)/H 2 O 2 system (Fenton's reagent). Typical operating variables such as reagent concentration (C H2O2 ) 1.0-0.2 M; C Fe(II) ) 0.01-0.1 M) and temperature (T ) 293-323 K) exerted a positive influence on the chemical oxygen demand and total carbon removal. The optimum working pH was found to be in the range 2.5-3.0. The exothermic nature of the process involved a significant increase of the temperature of the reaction media. The process was well simulated by a semiempirical reaction mechanism based on the classic Fenton chemistry. From the model, the reaction between ferric iron and hydrogen peroxide [k ) 1.8 × 10 15 exp((-12577 ( 1248)/T)] was suggested to be the controlling step of the system. Also, the simultaneous inefficient decomposition of hydrogen peroxide [k ) 6.3 × 10 12 exp((-11987 ( 2414)/ T)] into water and oxygen was believed to play an important role in the process. On the basis of stoichiometric calculations for hydrogen peroxide consumption, an estimation of the process economy has been completed.

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Some integrated processes to deal with landfill leachates have been investigated and their efficiencies expressed in terms of chemical oxygen demand (COD) removal. The systems tested were the result of different combinations of the following single stages:  acidic pH shift (elimination of humic substances), ozonation (O3), coagulation−flocculation with Fe(III) salts, Fenton's oxidation (Fe(III) + H2O2), wet air oxidation (with or without radical promoters), and adsorption onto activated carbon (commercial Norit 0.8 powdered activated carbon). COD removals obtained ranged in the interval of 80−96% for initial COD values close to 11000 mg L-1. None of the processes tested reduced the COD levels sufficiently to allow direct discharge; however, the ratio biochemical oxygen demand (BOD)/COD was significantly increased (up to 1000% in some cases, i.e., from 0.1 to values above 1.0). Total carbon reduction achieved ranged from 60 to 94%, while complete decolorization (measured as the absorbance at 410 nm) was obtained in practically all the combinations investigated.