Estudo dos coagulantes naturais cereus jamacaru, opuntia ficus-indica e pilosocereus gounellei como pré-tratamento para desinfecção solar

Abstract

Natural coagulants are used as an alternative to a viable water treatment, targeting populations that do not have access to treated water. The objective of this work was to evaluate the coagulant capacity of Cereus jamacaru (mandacaru), Opuntia ficus-indica (palm) and Pilosocereus gounellei (xiquexique) cacti as a pretreatment for disinfection by solar radiation. Acid extracts were prepared with 0.10 mol L-1 HCl of each cactus, using the viscous (pulp) and others with the dry matter coming from the bark, all in the proportion of 2.00 g of cactus to 3.00 mL of extraction solution. Ca (OH) 2 0.10 mol L-1 was used as the alkalizing agent. Nine tests of coagulation and flocculation were performed in Jar Test with the operating conditions as fast mixing speed of 150 rpm and fast mixing time of 60 s, slow mixing speed of 45 rpm, slow mixing time of 900 if sedimentation time 15 min along with the turbidity, color and pH parameters. The raw water samples used in the coagulation and flocculation tests presented high turbidity and color parameters. The tests performed with the extracts prepared with the dry matter did not show coagulant efficiency, on the other hand those that were used the extracts prepared with the pulp of the three cacti demonstrated good coagulant action obtaining, in the best test, the turbidity and color removals with the 98% and 92% mandacaru extract, 98% and 96% palm and 98% and 96% xiquexique. After the pre-treatment, disinfection by solar radiation was carried out, where the filtered and unfiltered samples were added in PET bottles with a capacity of 2.0 L and subjected to sun exposure for a period of 6 hours. The results obtained for the coagulation and flocculation pretreatment samples were negative for the presence of total coliforms, and no samples were positive for Escherichia coli. In this way, it can be affirmed that the cacti present themselves as great potential natural coagulants to be used as occasional pretreatment of real turbid waters for subsequent solar disinfection, since after the treatment all the evaluated parameters have met the established by the Brazilian legislation for drinking water.