Sistema modular para tratamento de esgoto doméstico em assentamento rural e reúso para produção de girassol ornamental.

Abstract

The increase in world population in recent decades has pushed the natural resources, particularly the water. The crisis is worsening in developing countries, where the population limit coming up on food supplies, whose relationship with the availability of water is close. The lack of a management policy of water resources and growing need for food supply has sued other conservation policy and conscious, planned reuse of water. The reuse for agricultural purposes is becoming a more advantageous opportunity, when it takes water to use less restrictive, reducing the use of good quality water and increased agricultural production at low cost. This work was conducted at the Universidade Federal Rural do Semiárido in Mossoró city, Rio Grande do Norte state/Brazil in order to determine the technical feasibility of a low cost modular system for the collection and treatment of domestic sewage water and reuse of treated effluent in the production ornamental sunflower (Helianthus annuus) cultivar 'Doble sungold'. The experimental design was randomized blocks with five treatments and four replications, each plot consisting of four plants, grown in individual pots, the factors being tested dilution of wastewater (T1 - 100% of treated wastewater - EFD) (T2 - 75% of treated wastewater - EFD + 25% of recommended nutrient solution-SNR), (T3 - 50% of treated wastewater - EFD + 50% of recommended nutrient solution - SNR), (T3 - 25% treated domestic wastewater - EFD + 75% of recommended nutrient solution - SNR) and (T5 -100% of recommended nutrient solution - SNR). The treatment system is feasible, but there are needs to be adjusted to reduce the concentration of nitrate (NO3-) which proved to be high. Regarding the reduction of nutrients, the treatment plant has its limitations, it is necessary to engage other system of treatment, depending on the intended purpose for the effluent. For growth variables, the dilution factors were significant, however, the dilution factor 5 was higher than the effluent dilution factor 4 at the end of the cycle of sunflower cultivation, due to increased nutritional demands of culture, going the opposite for the variable stem diameter and except for plant height and number of petals, that showed growth coincidental. Also, there was no significant difference for the assessment of dry leaf, stem and chapter, and the effluent dilution factor 1 (100% EFD) had unsatisfactory results. In the evaluation of the macronutrients, only the levels of nitrogen (N), phosphorus (P) and magnesium (Mg) showed significant differences between the effluent dilution factors, and the effluent dilution factor 3 showed the best performance in relation to N, P, Mg, K and Ca with values well above the required culture; whereas the effluent dilution factor 1 showed a worse performance compared to N, P, Mg, and yet, despite having only used wastewater 4% of the concentration of nutrients in the recommended nutrient solution met the needs of ornamental sunflower cultivation, but the mixtures (dilution factors) diluted SNR, unbalanced as to decrease efficiency.