Efficiency of chemical treatment on drip irrigation systems with sanitary sewage

Abstract

The efficiency of chemical treatment to prevent the clogging of emitters applying treated sanitary sewerage is discussed. The experiment was carried out at the Sewerage Treatment Pilot Plant of the Universidade Federal de Viçosa, Viçosa MG Brazil. A test platform was built for this experiment to supply four units of drip irrigation with treated sanitary sewerage, filtered in a 120-mesh disc filter. Three different models of drippers were tested (Naan Drip-Paz 25, Plastro Hydro PC and Naan-Tif) for 560 hours. Concentrations of free residual chlorine of 0.4; 1.0 and 1.9 mg L^-1 were tested for chemical treatment. Phosphoric acid was used in the treated sanitary sewerage to reduce pH to a mean value of 6.6. The results showed that the joint application of chlorine and phosphoric acid in the treated sanitary sewerage minimized the development of the biofilm inside the drippers and the lateral lines. The concentration of free residual chlorine of 0.4 mg L^-1 proved to be the most appropriate to prevent clogging of emitters. The treated sanitary sewerage applied by drip irrigation system produced a biofilm caused by the interaction between bacteria colonies and algae in the drippers. Consequently, CUC mean values decreased, varying between 3.63 and 16.96%, depending on dripper model, after 560 working hours by irrigation units.