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Post-treatment of anaerobic effluents in an overland flow system

2001; Pergamon Press; Volume: 44; Issue: 4 Linguagem: Inglês

10.2166/wst.2001.0228

1996-9732

C. A. L. Chernicharo, R. da Silva Cota, A.M. Zerbini, Marcos von Sperling, L.H. Novy de Castro Brito,

Wastewater Treatment and Nitrogen Removal

This research aimed at the investigation of an overland flow system applied to the post-treatment of anaerobic effluents. The system treated domestic sewage in Itabira City (Brazil), being composed by an anaerobic reactor and an overland flow system, the latter working as a post-treatment unit. A portion of the reactor's effluent was directed to a group of three overland flow slopes (demonstration scale), that were operated with different application rates. During Phase 1 of the research the overland flow system was fed under a permanent hydraulic regime (constant flows), having as inflow the effluent from an UASB reactor (full-scale, volume of 477 m3). During Phase 2, the overland system was fed under a hydraulic transient pattern (variable flows with hourly variations), having as inflow the effluent from a partitioned UASB reactor (demonstration-scale, volume of 9 m3). In general, the performance of the overland flow system as a polishing step was very good, mainly because of the low solids and organic matter concentration in the final effluent (average values of BOD from 48 to 62 mg/L; COD from 98 to 119 mg/L and SS from 17 to 57 mg/L). Regarding nutrients and coliforms, the system also reached satisfactory efficiency levels. Based on the experience obtained with this study, it is suggested that overland flow systems, working as post-treatment step of UASB reactors, can work with application rates in the range of 0.4 to 0.5 m3/m.h, which are higher than those normally applied.