The water and nutritional potential of wastewater has been frequently exploited as an alternative water source for the irrigation of crops, especially in regions affected by the scarcity of water resources. Thus, this study aimed to evaluate growth and production of ornamental sunflower (Helianthus annuus L.) cv. Anão de Jardim irrigated with different dilutions of treated domestic sewage in public-supply water. The experiment was conducted in completely randomized design with five treatments and four replicates, in a greenhouse, in the Experimental Area of the Agricultural Engineering Graduate Program of the Federal University of Recôncavo of Bahia, located in the municipality of Cruz das Almas - BA, Brazil. Treatments started seven days after transplanting of the seedlings and consisted of five dilutions of treated domestic sewage (TDS) in public-supply water (PSW) (100% PSW – control; 25% TDS + 75% PSW; 50% TDS + 50% PSW; 75% TDS + 25% PSW and 100% TDS). In the control treatment, plants were fertilized with 100% of the mineral fertilization recommendation, whereas plants in treatments with effluent received 50% of the nitrogen (N) and potassium (K) recommendation. Biometric (plant height, stem diameter, number of leaves, shoot fresh and dry matter and leaf area) and production (capitulum internal and external diameter, capitulum fresh and dry matter, beginning of flowering and full capitulum opening) indicators evaluated at harvest demonstrated that ornamental sunflower plants irrigated with 100% TDS showed similar performance to those irrigated with PSW, which makes it possible to infer on the possibility of replacing PSW by TDS in irrigation, along with the 50% reduction in the recommendation of N and K fertilization, with no damage to the growth and production of ornamental sunflower, cv. Anão de Jardim, thus leading to the saving of good-quality water and fertilizers.

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Helianthus annuus L.. Wastewater. Water resources. INTRODUCTION In agriculture, water is essential for crop development and production. Therefore, in areas where rainfall is scarce, it is of fundamental importance to complement irrigation. In some regions, such as the Northeast semi-arid region, where weather conditions establish a situation of scarcity of water resources due to the low rainfall levels and high evapotranspiration rates, domestic and industrial purposes are the priority in the use of water, which limits the use and expansion of irrigated agriculture. In addition to such limitation, most regions also face sanitary problems, with poor sanitation systems and sewage effluents dumped in watercourses, causing contamination of water bodies and environment. Given this environmental degradation, especially water pollution, many studies have been carried out in Brazil to establish a sustainable management for water resources. Since irrigated agriculture is one of the most water-consuming activities and water resources are becoming increasingly scarce, wastewater utilization in agriculture and studies on defining techniques for the treatment of these waters and their subsequent use have been stimulated (CUBA et al., 2015). The reuse of water in agriculture has increased significantly due to factors such as the increasing difficulty in identifying alternative sources of water for irrigation, the high cost of fertilizers and the treatment systems required before its discharge into receiving bodies, in addition to the guarantee of being used with minimum risks to public health and soil contamination. Therefore, water reuse represents a tool for the sustainability of water resources, applied mainly for non-potable Received: 08/04/19 Accepted: 30/12/19