Oil removal from fishmeal mill wastewater by the Fe°/UV process: optimization by experimental design

Abstract

Oil is one of the most difficult to eliminate pollutant present in the fishmeal mill wastewater industry, due to its physical properties which allow it to expand in a fine layer on the water’s surface, inhibiting light penetration, and gaseous exchange between the water–air phases. This alters photosynthesis, which reduces dissolved oxygen content, with consequent modifications on the structure of the food chain. In order to reduce oils from wastewater, we used elementary iron in catalytic suspension with ultraviolet radiation (254 nm). The reaction was carried out in a cylindrical quartz reactor. The efficiency of the studied system was determined by means of multivariate analysis with the statistical program MODDE 7.0, where the experimental variables were pH and reaction time. The response of the treatment was given by the percentage of oil removal. The optimal experimental value obtained was 96% of oil removal, under conditions of pH = 4.8 and 40 min of reaction time. Total organic carbon reduction, measured as total organic carbon, reached 70.9%. Additionally, we achieved reduction of chemical oxygen demand and biological oxygen demand of 78.18 and 70%, respectively, under optimal variable conditions. Under the same conditions, the disinfection capacity of the system reached nearly 100%. Based on these results, we affirm that the Fe°/UV treatment is efficient in the removal of fish oil from fishmeal mill wastewater, thus avoiding effluent filtration, which is necessary in treatments that use iron salts, such as the traditional Photo-Fenton reaction.

Keywords:

• Experimental design
• Fishmeal mill wastewater
• Oil
• Response surface methodology
• Zero-valent iron

Acknowledgment

This research was supported by the Facultad de Ciencias of the Universidad Católica de la Santísima Concepción.