Dissolved Air Flotation as superior pre-treatment for municipal waste water treatment
Wilbert Menkveld – Nijhuis
(free)
A pilot-scale dissolved air flotation (DAF) system was placed at the municipal WWTP of water board Rijn and IJssel in Olburgen, the Netherlands to investigate the potential of DAF as alternative to
conventional pre-sedimentation tanks. In two tests the pilot system treated either the influent or the effluent of a pre-sedimentation tank. Flocculation/flotation gives the following improvements when
compared to a pre-sedimentation tank (PST): – increase of TSS removal from 25-40 % in a traditional PST, to 70-80 % for a DAF system with
polymer and >90 % for a DAF system combined with polymer and coagulant dosing.
– increase of COD removal from 20-25 % in a traditional PST, to 50-60 % for a DAF system with polymer and 60-70 % for a DAF system combined with polymer and coagulant
dosing.
This pilot research proved that DAF systems can be applied as an alternative for pre-sedimentation tanks for municipal waste water. The investment and total yearly costs for DAF without chemical dosage are lower compared to a traditional PST. When operational aspects are compared, the DAF
system shows advantages in regard to the removal efficiency of TSS and COD, footprint and less effect of variations in TSS load on the effluent quality. Moreover, DAF can be better adjusted compared to PST by adding chemical dosage to reach a high removal efficiency in order to meet
future restrictions on effluent discharge demands.
