FLOTAÇÃO POR AR DISSOLVIDO COMO PÓS-TRATAMENTO DE EFLUENTES DE LAGOAS DE ESTABILIZAÇÃO
Algal biomass. Coagulation-Flocculation-Flotation. Stabilization pond
Stabilization ponds have important advantages, such as high efficiency in removing organic matter and pathogens, non-use of electricity and operational ease in wastewater treatment, especially in warmer climates. On the other hand, one of its disadvantages is the high concentration of suspended solids, mostly due to algal biomass. The objective of this research is to evaluate the removal efficiency of algae from wastewater stabilization ponds using flotation by air dissolved (FAD) as a technique of post-treatment. For tests with the FAD (coagulation-flocculation-flotation) we used a bench flotatest. A random factorial experimental design was planned using the ka-1 criterion, where k is the number of levels (three: low, middle, major) and a is the number of factors (four: coagulant dose recirculation rate water saturated, pH and flocculation time), performed in triplicate for the coagulant polyaluminium chloride and ferric chloride at effluent primary facultative pond and maturation pond. The samples were collected weekly in the morning, the effluent from the facultative pond and final effluent from Ponta Negra ETE (Natal). The following variables were evaluated in the raw wastewater and after the tests with FAD: turbidity, total suspended solids, apparent color, COD, chlorophyll "a", the total phosphorus, orthophosphate soluble and ammonia and organic nitrogen. The operational variable with greatest influence was the dose of coagulant for the PAC coagulant and coagulant ferric chloride to remove the greatest influence was pH followed by coagulant dosage. And from the optimized dosage removals in the analyzed parameters reached values between 66% and 97%. The post-treatment in the facultative pond had the highest removal percentage for the two coagulants, and ferric chloride got higher removal percentages for in all situations.