According to the results from an 18-month trial of the new DynaSand EcoWash filtration system combined with the Biolac extended aeration activated sludge, the Parkson system performs effectively and at approximately half the capital cost of competing designs.

 
The Wastewater Treatment Plant (WWTP) at Laurel, southwest Delaware, was required to upgrade its facultative lagoon system to an ENR capable system to meet the new regulations established for the Chesapeake Bay watershed. The specified ENR effluent limits are BOD5 < 5.0 mg/l, TSS < 5.0 mg/l, TN < 3.0 mg/l, and TP < 0.5 mg/l.
 
The Parkson DynaSand EcoWash system improves the DynaSand filter by changing the continuous backwash into an intermittent backwash process. The intermittent backwash allows solids to accumulate in the sand bed, creating a thin layer that reduces the voids between the sand grains improving the solids capture rate of the filter.
 
The addition of the EcoWash intermittent backwashing sand filtration system at Laurel WWTP enabled the plant to cut chemical usage in half and reduce energy consumption by around 90%. The results showed that the DynaSand EcoWash filter consistently provided effluent nitrate (NO3-N) concentrations below detection limit of 0.2 mg/L even with instantaneous influent nitrate as high as 14 mg/l and 12 mg/l. At the same time, the EcoWash achieved a 90% reduction in reject water compared to continuous backwash operation, which dramatically reduces the reprocessing flow through the plant.
 
“The EcoWash design has performed very well and exceeded the expectations of everyone in the community,” said Marianna Novellino, product manager for Filtration and ENR Filtration at Parkson. “Operators and engineers like this technology because it doesn’t require extensive training to make the system perform at its best.”