Adequação de Águas Ferruginosas Para Uso em Irrigação Por Gotejamento

Abstract

Many regions of Brazil have low rainfall or an irregular distribution of rainfall, such as the northern region of the state of Espírito Santo, included in the drought polygon, where the use of irrigation is necessary. In areas of this region, water with high levels of total iron (FeT) is frequently present, an element capable of causing serious clogging problems in emitters. This occurs mainly when the iron is in a reduced form, prone to precipitate inside the pipes after oxidation, also favoring the development of iron bacteria. Taking into account difficulties in using water with a high iron content in an irrigation system, the objective of this work was to evaluate the performance of sand filters, consisting of proportions of zeolites (0; 33 and 67%, m/m), associated with aeration/decantation, pH correction and addition of chlorine, in addition to treatment using a magnetizing device, in the adaptation of ferruginous waters, with high FeT contents exceeding 2 mg L-1, originating from tubular wells to be used in a system drip irrigation. Additionally, these waters were applied to a prototype drip irrigation system without a self-compensation system (SPC), flat-type labyrinth emitters. The degree of clogging and uniformity were then evaluated, as well as the reductions in total iron (FeT) after the water passed through the treatment system. Water samples were collected biweekly, bimonthly and quarterly, at 26 points of the project. The analyzes were subjected to descriptive analysis, in order to identify the treatments with the greatest efficiency in reducing the iron present in the water, which identified that the use of aeration and decantation significantly reduced the concentration of iron present in the water, reducing the risks of clogging of emitters from high to medium when assessed. All treatments, for the evaluation period, provided water emission coefficients (CUE) classified as “excellent”, however, it was observed that with the use of water with a high iron content, without additional treatment, this source over time began to show a drop in CUE values, due to the high levels of iron in its composition.