Reuso de efluentes na irrigação de milho e no cultivo "in door" de microalgas para fins biotecnológicos.

Abstract

The effluents reuse in irrigation corresponds to a viable and sustainable alternative, because in addition to ensuring the use of water, allows crops to receive nutritional supplementation, as they are made up of essential macro and micronutrients for plants. Nile tilapia (Oreochromis niloticus) is one of the most commercially cultivated species and in its processing, the viscera are discarded and as a way of using them are used for the production of effluents. Effluents are also used in the cultivation of microalgae species, mainly because is a low cost alternative cultivation medium and has essential nutrients for their development. In this experiment, the reuse of effluents was used in irrigation of hybrid corn, in pots, with a completely randomized design using 2 types of water (supply and treated domestic sewage), 5 doses of NPK with 4 repetitions. The leaf composition and the levels of macro and micronutrients were analyzed. The reuse of sewage effluents promoted an accumulation of micronutrients in the leaf, which can be used as a source of mineral supplementation for the cultivation of corn. To evaluate the growth of microalgae, two species were used: Chlorella vulgaris and Scenedesmus obliquus, which were inoculated in four percentages (25, 50, 75 and 100%) of effluents from tilapia viscera. The growth of Chlorella vulgaris was satisfactory in 75% reuse water, indicated by the long exponential phase and maximum cell density reached in 28 days of cultivation. In relation to Scenedesmus obliquus, the growth was satisfactory in the 100% effluent, showing adequate nutritional efficiency to obtain all phases of growth and maximum cell density in 35 days. The microalgae were sedimented using cationic starch. The results showed 80% sedimentation efficiency when the cationic starch 2040 concentration was fixed between 1.0 and 2.0 g. The efficiency of sedimentation with cationic starch 3040 was positive in a concentration between 0.5 and 1.0 g of starch. Thus, we concluded that both cationic starches can be used in the flocculation of microalgae, indicating that cationic starch 3040 is better because it uses a lower concentration with efficiency above 80% in the first 60 minutes of flocculation.