Agricultural use of sewage treated by a stabilization ponds system: experiences of Prosab in Lins - SP

Abstract

A Pilot Plant to treat the effluent from SABESP’s Wastewater Treatment Plant (Stabilization Pond System) located at Lins was built within a six-hectare area adjacent to the Treatment Plant. The study focused on agricultural applications of the final treated effluent. Additional unit operations for wastewater treatment were constructed – namely hypochlorite disinfection, UV light disinfection and ozonation units. The final effluent from the Pilot Plant was applied in crop ir¬rigation – namely coffee, corn and bean crops and the feeding system was by drop irrigation. Additionally, a fraction of the final treated effluent fed a hy¬drophonic system installed in vases, in which chrysanthemum and Gypsophila were cultivated. A third feeding line supplied a fish tank in which Oreochromis Niloticus were grown. A number of physical, chemical and biological variables were utilized for quality control of effluent streams at the various treatment stages, to monitor the cultivated crops and the soil, as well as agricultural pa¬rameters to identify growth characteristics. For all the cases under study there were conventional mode crops in parallel, acting as controls or references. The results obtained showed that the pond effluent, besides the hydraulic capacity itself, contained nutrients that are adequate for agricultural purposes, with sig¬nificant savings associated. Additionally, such applications in irrigation avoid the eutrophication of natural water bodies