Avaliação de um sistema de Wetlands construído no pós-tratamento de efluente de frigorífico

Abstract

The production of swines is an important branch of the Brazilian industry. However, the discharge of generated effluents in the water bodies causes degradation of the water quality and affects the environmental equilibrium and the human health. Therefore, this work sought to evaluate the removal efficiency of carbonaceous, nitrogen and phosphorus matter of a constructed wetland system, vertical flow, applied in the post-treatment effluent from pig fridge. Two wetlands systems were set, being one build with 13 cm of coarse sand and 14 cm of graded gravel 1 and the other one planted with seedlings of Zantedeschia aethiopica macrophyte (calla lily) under the bed of sand and grit. The systems were operated in batch mode during the months of October to December of 2014 to determine the physical-chemical parameters pH, liquid temperature, COD, ammonia, nitrite, nitrate and total phosphorous. It was possible to compare the efficiency obtained by the systems based on the results of the cultivated and non-cultivated systems (filter). The assays were carried out with collection of the samples in intervals of 2 h during the period of 8 h. With the results of the removal of organic matter in terms of COD were made adjustments by kinetic models of 1st and 2nd order to obtain the apparent constant consumption of organic matter. Was found higher average removal efficiency of COD, ammonia nitrogen and phosphorus in the planted system (90% ± 11%, 86% ± 6% and 86% ± 7%, respectively) in relation to the filter (81% ± 22%, 84% ± 9% and 63% ± 43%, respectively). However, higher production of nitrate was observed in the filter (6.23 ± 5.81 mg.L-1) compared to that noted in the cultivated system (0,52 ± 0,39 mg.L-1). Removal of nitrite was verified in the cultivated system (65% ± 26%) and production in the filter (266 ± 468%). The planting system was more efficient in removing phosphorus (86% ± 7%) of the filter system (63% ± 43%). The kinetic models of 1st and 2nd order for removal of COD presented adjustment less than other works reported in the literature (R² <0,6) for planted and filter systems. Regarding the 1st order model, the apparent coefficient of removal of organic matter in terms of COD ranged from 0,3730 to 1,8383 h-1 for the filter and 0,7330 to 1,8383 h-1 for the system planted. As for the 2nd order model, this ratio ranged from .0012 to 0.0397 h-1 for the filter and 0.0036 to 0.0397 h-1 for planting system.