This study evaluated the ability of hydrous ferric oxide reactive filtration (HFO-RF) to remove mercury (Hg) from municipal secondary effluent at four study sites. Pilot HFO-RF systems (136 m 3 /day) at two sites demonstrated total Hg concentration removal efficiencies of 96% (inflow/outflow mean total Hg: 43.6/1.6 ng/L) and 80% (4.2/0.8 ng/L). A lightly loaded medium-scale HFO-RF system (950 m 3 /day) had a concentration removal efficiency of 53% (0.98/0.46 ng/L) and removed 0.52 mg/day of total Hg and 2.2 μg/day of methyl-Hg. A full-scale HFO-RF system (11,400 m 3 / day) yielded a total Hg concentration removal efficiency of 97% (87/2.7 ng/L) and removed an estimated 0.36 kg/year of Hg. Results suggest that the quality of secondary effluent, including dissolved organic matter content, affects achievable minimum total Hg concentrations in effluent from HFO-RF systems. Low HFO-RF effluent concentrations (<1 ng/L) can be expected when treating secondary effluent from suspended-growth biological treatment systems.

A tertiary reactive filtration system has been developed by Blue Water Technologies, Inc. to removal total phosphorus and other constituents from wastewater. The reactive filtration system utilizes continuous backwash upflow filtration technology. The short-term and long-term fullscale testing completed by Blue Water Technologies, Inc. has yielded promising results for the removal of phosphorus from municipal wastewater. The long-term steady-state test of 0.25 mgd through the Blue PRO-CEPT dual reactive filtration system produced monthly average effluent total phosphorus levels of 0.036 mg/L, 0.009 mg/L, and 0.016 mg/L from December 2005 through February 2006. The system was not completely optimized as a dual-pass system diurnal conditions at the facility. Total phosphorus effluent during this testing period averaged 0.13 mg/L from the first filter stage and 0.015 mg/L from the second stage. The diurnal flow varied from 75 gpm to 250 gpm (0.11 mgd to 0.36 mgd).Results from Blue Water Technology, Inc., indicate that progress is being made in reducing the level of TP from wastewater effluent when compared to traditional coagulation and filtration technologies. To achieve effluent TP concentrations to 0.01 mg/L suggests a more complete precipitation of soluble phosphorus, or the presence of other reactions such as adsorption.