Reator aeróbico de biogrânulos e lagoa de aguapé como biotecnologia para o tratamento de águas residuais da suinocultura

Abstract

Residues generated by pig farms have high pollutant potential, can cause damage to human and animal health and deteriorate the quality of air, soils and water resources. These environmental troubles have led researchers to investigate alternative processes for wastewater treatment, replacing the conventional management of the wastewater in anaerobic lagoons. In this context, the aim of this thesis was to develop an integrated treatment system for piggery wastewater that is able to simultaneously remove pollutants from wastewater and recover organic compounds and nutrients in the concentrated form of sludge and biomass of plants. Three modular processes composed the wastewater treatment system: solid-liquid separation module (gravity settler), an aerobic granular sludge sequencing batch reactor (SBR) and a constructed wetland module. The settler (module 1) was constituted by a 50 cm-high PVC column, in which wastewater was treated with a sedimentation time of 5 minutes. The supernatant fraction was submitted to treatment in the aerobic granular sludge SBR (module 2). This bioreactor operated continuously for 505 days, with 1,515 cycles, in laboratory conditions. The reactor operated in sequencing batch mode, with hydraulic retention time (HRT) of 8 h, feeding in the first minutes of the cycle and settling/discharging in a time of 1 to 5 minutes. Piggery wastewater was used as influent, in natura or after solids separation. After discharging from the reactor, the effluent was settled 15 minutes for the sludge and liquid supernatant separation. The supernatant was submitted to a post-treatment in a water hyacinth (Eichhornia crassipes) wetland system (module 3), in greenhouse conditions. The wetland was operated in a semi continuous mode with discharging of effluent and influent feeding every 2 days and a total HRT of 10.6 days. The settler showed a considerable contribution in solid and organic compound removal. In the reactor, a stable and uniform sludge bed was developed. The reactor was operated with a extremely high organic loading rate (29.8 kg m-3 day-1 of COD) and it was possible to demonstrate the occurrence of simultaneous nitrification and denitrification, the influence of flocculated biomass in the removal of particulate organic matter and a high rate of soluble organic matter removal (0.9 kg m-3 h-1 of COD). The wetland contribution for pollutant removal was considerable less than the other two modules of the integrated treatment system, but it was essential for water purification. For all the evaluated pollutants, the removal efficiency was at the range of 92.4 to 99.9% and it was possible to accomplish with the Brazilian environmental legislation for treated wastewater quality. An average of 79% for N, 88% for P and 56% for K was recovered in the sludge form, which has in order of 5 to 11 times less volume than the wastewater submitted for treatment. The integrated wastewater treatment system is a promising biotechnology for the sustainable management of piggery wastes.