Characterization and treatment of sludge originated from septic tanks / Caracterização e pré-tratamento de lodo de fossas e de tanques sépticos

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Septic tanks are small structures used for partial treatment of wastewater produced from urban and rural areas. It utilization is justify mainly by simplicity of construction and for being a technology that requires low operational dedication. Although it is a technology vastly used in Brazil, there is not much information about the characteristics of the waste dumped in there, and the conditions of collection, transport, and final destination of the sludge generated in the system. The objective of this research was characterize the sludge originated from septic tanks and to design, construct and evaluate a treatment unit model to be used for prior treatment of the sludge generated in those septic tanks. This unit, composed by a sieve, a degritter, and a flotation device, was assembled in the São Paulo University Campus, near the area 1 from the campus Wasterwater Treatment Plant (WWTP). It had the purpose to remove har solid particle, sand and the floating material before their entry in the Wasterwater Treatment Plant. Was made to characterize the sludge septic tank collected in situ and the sludge originated from the Septic Pumper Truck, unloaded into a tank of 15000 L. Furthermore, the characterization of the sludge originated from the Septic Pumper Truck was performed twice, once in the material collected in the first visit to the defined location and the other in the material collected about six months after the first collection. The use of ultrasound was tested to ameliorate the fragmentation of the particulate material and to improve the method of analysis of the sludge in situ. Additionally, it was characterized the sludge from septic tanks in the Waste Reception Center from the city of Campinas, São Paulo State - SANASA - Society of Water Supply and Sanitation in composite samples collected from 24 trucks during the unloading. Septic Pumper Truck in th Waste Receptation Center. A complementing test was performed in order to text the degradation of the floated sludge by anaerobic and aerobic processes. The characterizations revealed a great heterogeneity in the composition of the sludge and the high organic content, which should be taken in consideration regarding the impacts in the environment and in the WWTP. This underlines the importance of treatment of the sludge prior to discharging into the WWTP. The pilot plant was managed to work at different rates of surface sludge application (80, 110, 140 and 200 M POT.3/M POT.2.day). The 110 M POT.3/M POT.2.day rate displayed the highest efficiency with the removal of 91.7% of suspended solids, 89.3% of the chemical oxygen demand, and 81 9% of oils and waxes. The results showed the efficiency of the flotation system in the removal of suspended solids, oil and greases. The aerobic digestion of the floated material was efficient when it received inoculation with aeration period greater than 20 days, which allowed CDO the removal of 88.3% and 90% of oil and greases.

ASSUNTO(S)

flotação degradação anaeróbia characterization of the sludge degradação aeróbia aerobic digestion lodo de fossa e tanque séptico ultrasound caracterização de lodo pré-tratamento de lodo sludge from septic tanks flotation prior treatment of the sludge anaerobic digestion ultrassom

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