Influence of flocculation conditions in the performance of an experimental domestic sewage treatment plant consisting of an anaerobic expanded bed reactor followed by dissolved air flotation.
This paper presents the results of a study performed with an experimental domestic sewage treatment plant (240 m3 x d(-1) flow) consisting of expanded bed anaerobic reactor (EBAR) followed by dissolved air flotation (DAF) unit. For the flotation step, the anaerobic reactor effluent was previously coagulated with 50 mgFeCl3 x l(-1) and flocculated under different conditions (mean velocity gradient, Gf, and flocculation time, Tf). The Gf values were from 60 to 100 s(-1) associated with 13 and 20 min Tf values. During the tests, the following operational conditions of the flotation unit were maintained: chemical addition (50 mgFeCl3 x l(-1)), 18% recirculation rate associated with a pressure of 450 +/- 10 kPa in the saturation chamber and overflow rate of 180 m3 x m(-2) x d(-1). Temperature ranged from 23.8 degrees C to 30.0 degrees C. Best results were achieved for Gf = 80 s(-1) and Tf = 20 min. For these conditions, the DAF unit removal efficiencies were: 94.4% for chemical oxygen demand (with 53 mg x l(-1) COD residual), 87% for phosphorus (with 0.80 mgP x l(-1) residual), 96.7% for total suspended solids (with 9 mg x l(-1) TSS residual) and 96.4% for turbidity (with 12.9 NTU residual), when the anaerobic reactor effluents have worst quality during the whole day.
Penetra
R G
RG
Department of Hydraulic and Sanitary Engineering, São Carlos School of Engineering, University of São Paulo (SHS-EESC-USP), Av. Trabalhador São-carlense, 400, São Carlos, SP, Brasil 13560-250. penetra@otv.com.br
Reali
M A P
MA
Campos
J R
JR
D000388:Air; D001421:Bacteria, Anaerobic / Q000502:physiology*; D019149:Bioreactors; D005427:Flocculation; D010758:Phosphorus / Q000302:isolation & purification; D012722:Sewage / Q000382:microbiology*; D012995:Solubility; D014865:Waste Disposal, Fluid / Q000379:methods*
D012722:Sewage; D010758:Phosphorus