Irrigação por infiltração com efluente de lagoa anaerobia em solo cultivado com milho (Zea mays L.)
AUTOR(ES)
Saulo Bruno Silveira e Souza
DATA DE PUBLICAÇÃO
2004
RESUMO
The experiment was conducted around of a Sewage Treatment Plant located in Limeira city, São Paulo, Brazil. This research had the proposal to reuse the domestic effluent treated in an anaerobic lagoon, that present a BOD removal efficiency of 50%. The main objective was the determination of application rates of effluent in the soil according to sanitary and agronomic engineering practices. Three different rates were studied, corresponding to irrigation depths of 0.20, 0.40 and 0.60m. The study was carried out for three treatments, parcels irrigated with effluent, water plus fertilizer, and only water. Collectors were placed in the soil profile at 0.25, 0.50 and 0.75 m to extract the soil solution. The experiment was happened during three harvests, using the cultivar AG 405 for the two summer harvests, and, the cultivar BR 106 for the winter harvest. The fertility of the soil was verified through chemical analyses of routine, in the end of each harvest. The productivity of the culture was evaluated by the weight of dry grains to 65oC; by the weigh of dry grains to 13% of water; and, by the weigh from 1000 grains to 13% of water. Also, it was determined the total contents of the metals Cd, Cr, Cu, Ni, Zn, and, Pb, for the leaves and grains in the second harvest, and, for the grains in the third harvest. The results indicated that the agricultural reuse is, without a doubt, advantageous. The physiochemical characteristics, considered unsatisfactory in the anaerobic treatment, are advantageou to the system soil-plant. For the three harvests, the production of grains was practically the same, so much for the treatment with sewer and as for the treatment with water plus fertilizer. The irrigation depth of 0.40 m obtained the best productivity. In the last harvest, for this irrigation depth, the parcels irrigated with efluente had a productivity of 6.2 ton ha-1, while in the fertilizer parcels, 6.3 ton ha-1. In the sanitary aspect, the results indicated good removal of organic matter and phosphorus. The removal of DBO varied from 77.8 to 99.5% in relation to the anaerobic efluent. For DQO, the results varied from 87.7 to 99.4%. The P content was reduced around 97.0% in relation to the applied efluent, returning to its natural reservoir, the soil. The nitrification process was complete, with reduction of 99.0% in the N-NH4+ concentration when compared to efluent. Nitrate percolation occurs more frequently after the decreasing of the water and nutrient demand of the plants; in some cases, the concentrations of nitrate were high, so much for the treatment with sewage, as with mineral fertilization. It can be noticed concentrations of nitrate in the liquid collected above the water potability parameters, 10 mg L-1. Still, the results obtained for coliforms indicated that these microrganisms are present in the soil, independent of the treatment. For E. coli it was verified a reduction of the order of 3 logs in relation to the applied efluent. The reuse of anaerobic efluent in agricultural soils is viable, since precautions are taken to avoid the nitrate and coliforms contamination
ASSUNTO(S)
agua - reutilização esgotos aguas residuais de irrigação irrigação
