Performance of treatment system for dairy wastewater and the effects of their disposal in Argisol

Abstract

This study aimed to analyse the performance of a treatment plant of wastewater of dairy industry (ARL), as well as the effects of its use on chemical characteristics of Argisol in Mossoró, RN, Brazil. The ARL was treated first in a grating system and later in an aerated lagoon (hydraulic detention time of 11 days). During the period from March to June 2013, the Biochemical Oxygen Demand (DBO), Chemical Oxygen Demand (DQO), total solids (ST), suspended solids (SS), dissolved solids (SD), K⁺, pH, Na⁺, Ca²⁺, Mg²⁺, salinity and hardness of the ARL of treated water were characterized. In parallel, the values of K⁺, Na⁺, Ca²⁺, Mg²⁺ and pH in five depths of Argisol (0 to 0.10, 0.10 to 0.20, 0.20 to 0.30, 0.30 to 0 40; and 0.40 to 0.50 m) with and without application of ARL, the application rate of 35 L m^-2 day^-1 for a period of five years were determined. The results indicated that the treatment system of ARL presented removal efficiency higher than 50% only for the DBO, DQO, ST, SS and Mg²⁺; the application of ARL resulted in increase of K⁺, Ca²⁺ and pH in five layers of Argisol and the highest levels of K+ and Na+ occurred in the surface layer of Argisol (0 to 0.10 m) fertigated with ARL.