Banca de DEFESA: CAROLINA TAVARES PAULA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : CAROLINA TAVARES PAULA
DATA : 22/06/2018
HORA: 16:45
LOCAL: Sala de aula do LARHISA
TÍTULO:

Performance evaluation of UASB–AS system (A/O) in hot climate regions

PALAVRAS-CHAVES:

UASB reactor. Activated sludge. Continuous-flow reactor. Biological nitrogen removal. Hot climate.

PÁGINAS: 39
GRANDE ÁREA: Engenharias
ÁREA: Engenharia Sanitária
RESUMO:

The association of modern anaerobic reactors (UASB) to activated sludge systems has been widely employed nowadays, especially in hot climate regions, as it provides the reduction of the organic load affluent to the activated sludge system. This results in a decrease of the oxygen demand and the sludge mass produced in the aerobic system. In these regions it becomes essential to consider the nitrification process in the aerobic reactor design to avoid competition for dissolved oxygen (DO) between autotrophic and heterotrophic microorganisms. Moreover, the need to include an anoxic stage for nitrate removal arises, in order to reduce its concentration in the secondary settler. It must be considered because the occurrence of denitrification in the sedimentation tank causes operational problems in the system, such as solids loss with the final effluent. Some studies indicate that the contribution of the UASB reactor in organic matter removal from the raw sewage interferes in both nitrification and denitrification processes. The lower organic load affluent to the activated sludge can reduce the development of heterotrophic microorganisms, which can decrease the minimum required DO concentration in the aerobic reactor. In addition, the UASB reduces the COD availability for denitrification, which can make the process unfeasible and bring instability to the system. Thus, the objective of this work is to evaluate the performance of activated sludge system with pre-denitrification used as post-treatment of UASB reactor in hot climate region. Thereunto, an experiment was carried out in a pilot scale WWTP, composed by UASB reactor followed by activated sludge system with anoxic and aerobic reactors and secondary settler. Sludge recycle from the settler and the aeration tank (to provide nitrate for denitrification) to the anoxic reactor were promoted, as well as the deviation of a portion of raw sewage directly to the anoxic reactor (to provide carbon for denitrification). The study was conducted in four stages, in which the following parameters were varied: reactors hydraulic retention time, DO concentration in the aeration tank and by-pass flow of raw sewage. Physical-chemical analyzes (COD, P, NH4+, NO3ˉ, NO2ˉ, TSS) were weekly performed to monitor and evaluate the pilot WWTP performance. During the whole experiment, sludge flotation in the secondary settler was observed as a consequence of inefficient denitrification in the anoxic reactor, which occurred uncontrollably in the sedimentation tank. Furthermore, the low organic load affluent to the activated sludge system limited the heterotrophic biomass growth, favoring nitrifying bacteria in the aeration tank. The results show that there are still limitations to the application of activated sludge system as post-treatment of UASB reactor in relation to the removal of nitrogen, in hot climate regions.

MEMBROS DA BANCA:
Presidente - 1759924 - HELIO RODRIGUES DOS SANTOS
Externo ao Programa - 3919045 - JULIANA DELGADO TINOCO
Externo à Instituição - SILVÂNIA LUCAS DOS SANTOS - UFCG