Biofouling and performance of labyrinth-type emitters in drip irrigation with treated domestic sewage

The use of wastewater in irrigated agriculture is an alternative to the lack of water resources of higher quality and allows obtaining, besides the reuse, environmental improvements. In the application of wastewaters, such as treated domestic sewage, localized drip systems are affected by the decrease in application of uniformity and discharge rate of the emitters, due to clogging. In this context, this study aimed to characterize the material of the biofouling and evaluate its effects on the hydraulic performance of emitters utilized in drip irrigation with wastewater from treated domestic sewage. The experiment was carried out on a bench at the field, in the Brazilian semi-arid region, in the state of Paraíba, Brazil, and consisted of the application of wastewater and public-supply water using three models of labyrinth-type emitters. The hydraulic performance of the emitters was monitored through the variation in discharge rate and coefficient of uniformity along 1188 h of operation. X-ray spectroscopy analysis was performed to characterize the chemical composition of the material that caused biofouling. The chemical elements identified in the characterization of the biofouling material were sodium, magnesium, aluminum, silicon, chlorine, calcium, iron, carbon and oxygen; the latter two were found in higher amounts. In addition, the presence of fluorine was also detected. Biofouling caused linear and quadratic reduction in the discharge rate of the emitters over the time of operation. Both wastewater and the hydraulic characteristics of the labyrinth contributed to clogging of the emitters.