title: Depuration in aerated ponds of citrus processing wastewater with a high concentration of essential oils.
abstract: Citrus processing wastewater was treated in aerated pilot plants in order to evaluate the following: (a) energy efficiency under different air flow rates and times; and (b) limits of spontaneous microflora in adapting to essential oils. In comparison to permanent air flow, night aeration for 12 hours determined an increase of up to 12% of the monthly removal rate of chemical oxygen demand (COD) and a consequent reduction by 10% of energy consumptions per unit of COD removed from 0.63 to 0.57 kWh/kg(COD). Lowering night aeration from 14 to 7 1/m3/h reduced by only 10% the removal rate of COD; the energy consumption per unit of COD removed (0.32 kWh/kg(COD)) was consequently reduced by more than 40%. Dissolved oxygen was maintained at very low level, rarely exceeding 0.2 ppm, with no bad smell. The consequent high oxygen deficit of 98-99% of saturation induced high oxygen transfer efficiency. The microbial population was characterized mainly by aerobic bacteria; only 5-8% of bacteria were strictly anaerobic. In the deep tank layer under the air diffuser a small amount of sludge settled (0.03-0.04 kg of dry matter per kg of COD removed), containing only 3% of total organic matter detected at the end of the depuration process. The fact that the concentration of essential oils could be progressively increased up to 1400 ppm without noticeably slowing down the biological processes demonstrated the remarkable microbial adaptation.
authors.affiliation: Unit of Agricultural Hydraulics and Soil Conservation, Department ofAgro-Forestry and Environmental Sciences and Technologies (DiSTAfA), 'Mediterrranea' University of Reggio Calabria, Reggio Calabria, Italy.
authors.forename: Demetrio Antonio
authors.initials: DA
authors.lastname: Zema
authors.forename: Serafina
authors.initials: S
authors.lastname: Andiloro
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Bombino
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Tamburino
authors.forename: Rossana
authors.initials: R
authors.lastname: Sidari
authors.forename: Andrea
authors.initials: A
authors.lastname: Caridi
mesh_terms: D000220:Adaptation, Biological / Q000187:drug effects*; D001419:Bacteria / Q000378:metabolism; D002957:Citrus / Q000737:chemistry*; D007220:Industrial Waste; D059013:Microbial Consortia / Q000187:drug effects*; D009822:Oils, Volatile / Q000494:pharmacology*; D010865:Pilot Projects; D018508:Water Purification
chemical_list: D007220:Industrial Waste; D009822:Oils, Volatile