First WTP to use DAF with ozonation and filtration
The plant used water from the Catskill and Croton Aqueducts. In spring, heavy rains combined with low reservoir levels and raised the turbidity to 100 NTU. Flow rates were lowered through inverted siphons in the aqueduct and created large volumes of entrained air and supersaturated conditions. Stilling basins would have been a logical choice, but there was insufficient room.
Nordic Water Products' Dissolved Air Flotation system was installed to handle the turbidity and supersaturated air. The DAF produces microscopic air bubbles that attach to the small particles and provide better removal than clarification.
The new system was laid out to draw raw water through two stages of rapid mixing with different chemicals. The water is then distributed to five identical treatment basin, each with flocculators and a NWP DAF clarifier.
From the DAF, the flow passes to two ozone contactors for disinfection. Disinfected flow then enters six gravity flow underdrain filters that contain anthracite over sand. As a final step, the filtered water is lightly chlorinated.
When the DAF started up, it produced quality water within 45 minutes using less coagulant chemicals than conventional methods.
As part of the system's maintenance program, the dual media filters are periodically cleaned by backwashing. The wastewater passes into a NWP GEWE inclined plate settler for clarification.
<%=company%>, 29850 N. Skokie Hwy., Lake Bluff, Illinois 60044-1192 Phone: 847-473-3700 Fax: 847-473-0477