Employment of factorial design to evaluate the organic loading and aeration of biological systems in the degradation of dairy wastewater

Abstract

Among industries producing foodstuffs, the dairy industry is notable for producing great amount of wastewater and high water consumption. Organic loading treatment based on biological degradation is a preferential treatment for dairy wastewater and effluents. However, it has some limiting factors for broader application due to the organic loading variation that results in an overload and wash-out of biological treatment systems. Considering these limitations, the organic loading and oxygen supply as factors in the rated efficiency of biological treatment systems with results expressed as removal efficiency of chemical oxygen demand (%CODremoved) were evaluated. The variables investigated were: 1) initial concentration of organic load [raw, diluted 1:1 v/v (wastewater/distilled water) and diluted 1:3 v/v (wastewater/distilled water)] and 2) aeration (with or without). A Doehlert factorial design type (2x3) was employed for these studies. Aerobics systems with organic loading at a 1:3 ratio (v/v dairy effluent /distillated water) showed elevated efficiency in biodegradation (88.31 ± 2.16 %CODremoved). The least efficient biodegradation was observed in anaerobic system for raw dairy effluent equal to 10.42 ± 3.97 %CODremoved. This indicated that a dilution of effluent organic loading was necessary in obtaining greater efficiency from a biodegradation system and low hydraulic retention time.