EFFICIENCY OF CURTAIN FLOCCULATION INTEGRATED WITH DISSOLVED AIR FLOTATION APPLIED TO WATER TREATMENT SLUDGE

Abstract

The idea of integrating hydraulic flocculation with Dissolved Air Flotation (DAF) into one unit had as fundamental hypothesis the simplicity of this type of flocculation, the reduction of the required volumes and the high efficiency and robustness provided by dissolved air flotation. A pilot Flocculation - Dissolved Air Flotation (FDAF) unit was built to treat filter backwash-sludge produced by a direct filtration water treatment plant. The new system required a low overall hydraulic detention time (22 min) and showed high efficiency with significant removal of colour (98.1%), total coliform (98.2%), suspended solids (87.1%), COD (92.5%), aluminium (88.5%) and turbidity (99.2%). The FDAF adjusted the effluent to Brazilian reuse standards and presented a high resilience to affluent quality variations. Thus, FDAF technique proved to be feasible for the treatment of filter backwash-sludge and for other types of wastewater containing low-density solids, reducing significantly the volume requirement as compared to conventional sedimentation or dissolved air flotation clarification processes.

Key Words: Curtin flocculation, dissolved air flotation, WTP sludge treatment.