Case study for the use of Nextsand Filter Media

Application: Clarified efluent polishing prior to UV Disinfection & Chlorination
Flow Rate: 160l/sec
Details: NextSand Filtration and UV package.

FRP Pressure vessels with NextSand filter media treating secondary clarified effluent. Designed to cope with rapidly varying inlet turbidities and TSS, with an optimized #ux rate and consistent outflow turbidity, for constant recycled water availability.


PERFORMANCE PARAMETERS

DESIGN Influent Turbidity NextSand Filtered Water Turbidity OUTCOME
4 – 75 NTU Variable Inlet Typical 0.8-1.3NTU >2NTU Max. Limit 95th %ile. Outlet Breach of license (NTU over-run): NIL


Specifications

Number of Filters 6
Flow Rate: 160L/sec (maximum)
240L/sec (future)
Inlet TSS >70 mg/L
(50mg/L per spec, 20 typical)
Filter Water Turbidity 2 NTU
Flow Rate per Vessel 30 L/sec
Operation Automatic
Operation Time 23 Hours per Day
Controls Local Control Panel with
outputs for SCADA
Filtration Rate 20-30 m3/m2.h
Filter Dimensions 2.2m Diameter x 2.4m High
Filter media surface 3.25 m2 per filter
No of Media layers 2
Maximum Inlet Pressure 500 kPa
Minimum Inlet Pressure 100 kPa
Filter Media 1 NextSand
Depth 900 mm
Density 2.6 x conventional multi media
Effective Size 0.4-1.4 mm
Uniformity coeficient 1.7
Micron rating 3 – 5 micron
Filter Media 2 Coarse Gravel
Backwash biocide Periodic CEB w/ sodium hypochlorite
Backwash water rate 13.4 L/m2.s
Backwash volume 15.65 m3per !lter per wash
Backwash Flow Rate 43.5 L/sec (per filter)
Backwash Filter Rate 46 m3/hr/m2
Backwash initiation method Pressure Differential or
Manual Selection
Expected backwash Frequency One per Day (typical -
dependant on water quality)
Air Scour Yes, prior to Water Backwash







Filtration performance: SDI & Turbidity reduction, filtration efficiency.

Test Results

Conclusion

The particle analysis shows that next Sand performs as well as or better than most 5 micron cartridge filters. next Sand operated at 1/2 the backwash frequency indicating twice the solids loading capacity of multi-media.