Flotação por ar dissolvido como pós-tratamento de efluentes de lagoas de estabilização

Abstract

For treatment of wastewater stabilization ponds have important advantages, such as high efficiency in removing organic matter and pathogens, non-use of electricity and operational ease, especially in tropical regions. 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 was to evaluate the removal efficiency flotation by dissolved air (FAD) in the post-treatment stabilization ponds effluent. For tests with the FAD (coagulation-flocculation-flotation) we used a bench flotateste. a random factorial experimental design was planned using the ka-1 criterion, where k is the number of levels (k = 3: low, middle, major) and a is the number of factors (a = 4: coagulant dose saturated, water recirculation rate, pH and flocculation time) with assays performed in triplicate for the coagulant polyaluminium chloride, ferric chloride effluent primary facultative lagoons and maturation pond. Samples of the effluent from the facultative pond and final effluent from the WWTP Ponta Negra (Natal) were collected weekly in the morning. The following variables were evaluated in the raw wastewater and after the tests with FAD: turbidity, total suspended solids, apparent color, COD, chlorophyll "a", total phosphorus, orthophosphate soluble and ammonia and organic nitrogen. The operational variable with higher influence on the removal variables was evaluated coagulant dose for the PAC coagulant and the coagulant ferric chloride to remove the greatest influence variable was the pH followed by coagulant dosage. 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 percentage removal in variables for the two coagulants, and ferric chloride got higher removal percentages in all situations.