Organic matter removal from wastewaters of the black olive industry by chemical and biological procedures

Chemical treatments of wastewaters from the olive industry are conducted by means of single UV radiation and by the action of hydroxyl radicals, which are generated by the simultaneous presence of UV radiation and hydrogen pe roxide, Fe2+ and hydrogen peroxide (Fenton system) and Fe2+ and hydrogen pe roxide plus UV radiation (photo-Fenton system). The single photochemical pr ocess produces a 35% removal of organic matter present measured as COD afte r 6 h of reaction, while the hydroxyl radicals enhance significantly this r eduction with values in the range 41-76%. At the same time, a removal of ar omatic compounds in the oxidation by single UV radiation and combined UV H2O2 was obtained in the range 20-52%. In the anaerobic digestion process, an organic matter reduction in the range 0.77-0.65 g of COD degraded per g of COD fed to the reactor was obtained, and a value of 250 ml CH4.g COD-1 o btained for the methane yield coefficient. A kinetic study was conducted us ing the Monod model, and rate constants k(o) in the range 0.061-0.015 min(- 1) achieved. This indicates that some inhibition effects by substances pres ent take place. The application of the Levesnpiel model for that inhibitory effect leads to the determination of the rate constant, inhibitory paramet er and critical substrate concentration of inhibition, their values being k =0.205 min(-1), n=18.8 and S*=20.1 g l(-1) respectively. Finally, the anaer obic digestion of the chemically pretreated wastewaters increases the rate constant k(o), as well as the methane yield coefficient, its value being 28 2 nil CH4.g COD-1. (C) 2001 Elsevier Science Ltd. All rights reserved.