A major electrical utility in the Lake Charles Louisiana area required high quality water for boiler feed makeup water. A ground water pumping station provided 5700 l/m water flow to a clarifier. The treated water with high Total Dissolved Solids to two parallel carbon steel pressure filters filled with sand/anthracite media.
5,700 l/m of filtrate water with low TDS was required to feed a large Reverse Osmosis system, where the product water was to be used for boiler makeup water at the electricity generating plant. Two problems were encountered with the multi-media filters:
- The design flux rate could not be achieved without the delivery pressure increasing forcing frequent backwash cycles.
- The filtrate TDS target for the RO feed water quality could not be achieved, Hence the RO equipment could not be operated at the design specifications to provide the 4500 l/m of RO product water for the boiler
Unable to operate the RO system due to the poor performance of the multimedia filter system the energy plant engineer contacted a NEXT treatment engineer and arranged to undertake a pilot trial of NEXT-SAND. After a 10 day trial, the utility plant actioned replacement of the multimedia filters with NEXT-SAND.
The two pressure vessels were loaded with NEXT-SAND and went on line in early 2002. The filters operated at the net 5.700 l/m design capacity for the following 2 years consistently producing a filtrate below the 50 mg/l TDS limit thus ensuring a reliable supply of water for the RO. Table 1 shows representative water quality data for the NEXT-SAND filter application.
|Table 1. Operating conditions and next-Sand performance
|Average over 24 months
The NEXT-SAND media allowed economic operation of a high volume Reverse Osmosis system on a water supply that was unusable based on conventional filtration methods