Ozonation of weathered olive mill wastewaters

Abstract

The treatment of fully and partly weathered olive mill wastewaters by means of ozonation was investigated, with emphasis on the effect of treatment conditions (organic loading, treatment time, ozone concentration) on the extent of chemical oxygen demand (COD) and total phenol degradation, colour removal as well as ecotoxicity to the marine bacterium Vibrio fischeri. In general, ozonation was capable of substantially reducing the concentration of phenols as well as decolourising the effluent after relatively short treatment times, with the extent of phenol and colour removal exceeding 80% in most cases. The fast and selective degradation of phenols was ascribed to the direct electrophilic attack by molecular ozone (ozonolysis). Conversely, complete mineralisation proved difficult; at the conditions employed in this study, COD removal varied from as little as 10% to about 60%. Both effluents were strongly ecotoxic owing to the presence of phenols and other organics in substantial concentrations; toxicity decreased partly following considerable degradation of the organic matter.

Ozonation of humic acid in water

“…7,8 Ozonation processes result in the cleavage of unsaturated bonds and formation of lower molecular weight compounds which are more readily biodegradable. 9,10 Ozonation as an effective method has been applied to treat HAs for years due to its capability of minimizing the formation of trihalomethanes that are known to have carcinogenic effects. 11 -13 By using characterization methods, it was demonstrated that ozonation of HAs leads to decoloration and to decrease in UV absorbance due to the cleavage of chromophores, 14 -17 as can be seen in Table 1.…”

Olive oil mill wastewaters before and after treatment: a critical review from the ecotoxicological point of view

“…These results were in agreement with Fiorentino et al (2003) who concluded that several individual phenolic compounds had a strong toxic potential on different trophic levels in the aquatic system, evaluating the OMW toxicity on four organisms: the algae P. subcapitata, the rotifer Brachionus calyciflorus, and two crustaceans, the cladoceran D. magna and the anostracan T. platyurus. Karageorgos et al (2006) also observed that in most of their experiments the toxicity values decrease with the decrease of organic content, but an increase of residual phytoxicity was observed possibly due to the production of short-chain fatty acids (C8-C9) during the oxidative process of ozonation.…”

A Review on the Applications of Ozonation for the Treatment of Real Agro-Industrial Wastewaters

“…The most usual way to manage these wastewaters consists in dumping them in evaporation pounds (Karageorgos et al 2006), which are an environmental danger for groundwater besides the production of bad smells (Azbar et al 2004). Moreover, this process depends upon the weather conditions.…”

“…It means that the effluent may not evaporate by the end of the summer and the pond may not be available in the next year. Karageorgos et al (2006) analyzed this possibility and investigated the potential of ozonation on the management of such weathered effluents (Table 1). Ozone was able to remove up to 80% of phenolic content (TPh) and color in 120 min of reaction.…”