COMBINED UNITS FOR SWINE WASTEWATER TREATMENT - PART II NUTRIENTS

In this study, we assessed the combined effect of two treatment units on removal of total Kjeldahl nitrogen (TKN) and total phosphorus (TP). Continuous feeding was provided to the units which consisted of an upflow anaerobic sludge blanket (UASB) reactor with a working volume of 96 L and a constructed wetland system (WS) with a capacity of 237 L. The experiment was performed in three phases with variation in hydraulic retention time (HRT). UASB reactor had a HRT of 59, 19.5 and 5 hours; and for the WSs, HRTs were 146, 48 and 13 hours. Volumetric organic loading rates (VOLR) applied to the reactor were 1.2, 1.3 and 13.0 kg. m(-3) d(-1) of COD. Surface application rates (SAR) in the WS were 120, 130 and 464 kg ha(-1) d(-1) of TKN, and 13, 51 and 240 kg ha(-1) d(-1) of TP. Removal efficiency of TKN and TP reached approximately 35% for the entire system with no significant differences among phases. However, such removal rates achieved higher values with increasing loads. Regarding the evaluated variables, we concluded that the effluent generated by the combined system at all phases did not reach the environmental standards proposed by the state of Minas Gerais (Brazil) to be released into water bodies. On the other hand, this waste has a great nutritional potential that should be used to enhance agricultural production.