Satisfactory results were obtained in a broad range of inlet organic loadings.
Chemical oxygen demand (COD) values, which varied from 251 to 1325 mg/L, were
reduced by 75%, and biochemical oxygen demand (BOD) values, which ranged
between 108 and 494 mg/L, were also reduced by 75%. The total suspended solids’
(TSSs) cumulative removal of 99% was very close to the theoretical maximum with
an average effluent TSS of 4 mg/L. The overall corresponding turbidity removal was
84%. Also obtained were the following nutrient reductions: phosphorous 82%, total
nitrogen 30%, and ammonia-nitrogen 19% [19].
All above-mentioned reductions have been attained over a wide range of flow
rates (76–170 L/min) and varying recycle ratios (5–63%). Also using various
combinations and concentrations of coagulants and flocculants, it was possible to
produce biosolids with a solids content of 3%, making it easier and less costly to
manage and dispose. The hydraulic loadings were up to 235 L/m
2 /min on the
primary F-Cell unit and 155 L/m
2 /min on the secondary FF-Cell unit. These
hydraulic loading rates are 7- to 11-fold greater in comparison to the 20 L/m
2 /min
loading of a conventional sedimentation system.
In addition to proving the effectiveness of the two-stage system in treating raw
municipal wastewater, it was possible to optimize the coagulant and flocculant
chemicals and doses to the following types and their concentrations [21]:
1. Primary clarification (F-Cell)
Ferric sulfate: 75 mg/L
Magnifloc 496 C: 4.4 mg/L
2. Secondary clarification (FF-Cell)
Magnifloc 496 C: 3.3 mg/L
Enhanced results were obtained for total phosphorous and nitrogen removals as
well as for the reduction of various forms of nitrogen. Changing from ferric sulfate to
polyaluminum chloride (PAC) in the F-Cell caused a significant reduction in total
phosphorous from 7.3 to 0.04 mg/L. This could be explained as an enhanced co- and
postprecipitation of phosphorous when PAC was used instead of ferric sulfate.
Another application of flotation for treatment of raw wastewater effluents has been
reported by Bratby [35]
6 Treatment of Activated Sludge Effluent
An FF-Cell pilot study was performed at the Oak Meadows Sewage Treatment Plant
in Licking County, OH, USA [18]. The objective of this study was to demonstrate
the FF-Cell’s performance in the treatment of their secondary clarifier effluent
following an aeration basin. The FF-Cell was run at various chemical dosages
using up to 5.6 mg/L alum and 0.5 mg/L polymer. All results reported in
Table 2.4 were based on daily composite samples. The FF-Cell was proven to be
62
N. K. Shammas et al.
Chemical oxygen demand (COD) values, which varied from 251 to 1325 mg/L, were
reduced by 75%, and biochemical oxygen demand (BOD) values, which ranged
between 108 and 494 mg/L, were also reduced by 75%. The total suspended solids’
(TSSs) cumulative removal of 99% was very close to the theoretical maximum with
an average effluent TSS of 4 mg/L. The overall corresponding turbidity removal was
84%. Also obtained were the following nutrient reductions: phosphorous 82%, total
nitrogen 30%, and ammonia-nitrogen 19% [19].
All above-mentioned reductions have been attained over a wide range of flow
rates (76–170 L/min) and varying recycle ratios (5–63%). Also using various
combinations and concentrations of coagulants and flocculants, it was possible to
produce biosolids with a solids content of 3%, making it easier and less costly to
manage and dispose. The hydraulic loadings were up to 235 L/m
2 /min on the
primary F-Cell unit and 155 L/m
2 /min on the secondary FF-Cell unit. These
hydraulic loading rates are 7- to 11-fold greater in comparison to the 20 L/m
2 /min
loading of a conventional sedimentation system.
In addition to proving the effectiveness of the two-stage system in treating raw
municipal wastewater, it was possible to optimize the coagulant and flocculant
chemicals and doses to the following types and their concentrations [21]:
1. Primary clarification (F-Cell)
Ferric sulfate: 75 mg/L
Magnifloc 496 C: 4.4 mg/L
2. Secondary clarification (FF-Cell)
Magnifloc 496 C: 3.3 mg/L
Enhanced results were obtained for total phosphorous and nitrogen removals as
well as for the reduction of various forms of nitrogen. Changing from ferric sulfate to
polyaluminum chloride (PAC) in the F-Cell caused a significant reduction in total
phosphorous from 7.3 to 0.04 mg/L. This could be explained as an enhanced co- and
postprecipitation of phosphorous when PAC was used instead of ferric sulfate.
Another application of flotation for treatment of raw wastewater effluents has been
reported by Bratby [35]
6 Treatment of Activated Sludge Effluent
An FF-Cell pilot study was performed at the Oak Meadows Sewage Treatment Plant
in Licking County, OH, USA [18]. The objective of this study was to demonstrate
the FF-Cell’s performance in the treatment of their secondary clarifier effluent
following an aeration basin. The FF-Cell was run at various chemical dosages
using up to 5.6 mg/L alum and 0.5 mg/L polymer. All results reported in
Table 2.4 were based on daily composite samples. The FF-Cell was proven to be
62
N. K. Shammas et al.