Nitrate Removal from Wastewater Using
Fluid Bed Technology
ROBERT F. GASSER, Vice President
ROGER W. OWENS, Project Engineer
JOHN S. JERIS, Vice President
Ecolotrol, Inc.
Bethpage, New York 11714
INTRODUCTION
With the aid and cooperation of Nassau County, a nominal 36,000 gallon per day pilot
plant for denitrification was placed into operation in May of 1973 at the County's Bay Park
Water Renovation Plant. The pilot facility consists of a column of sand through which
nitrified effluent is passed upwardly at velocities sufficient to fluidize the sand. Nitrate and
nitrite are removed biologically by a large population of denitrifying bacteria which
completely cover each sand particle. Methanol was used as the carbon source for these
bacteria.
Under normal operation, the flow to the reactor was 25 gallons per minute or 15
gallons per minute per square foot of surface area. The empty bed detention time in the
column at this flow rate was 6.5 minutes, not including freeboard. Under these conditions
the effluent concentration was consistently less than 0.5 mg/1 nitrate plus nitrite nitrogen
which was equivalent to a daily removal of 99% or higher of the influent oxidized nitrogen.
For a period of one week, flow was increased to 40 gpm or 24 gpm/ sf, giving an empty
bed detention time of approximately 4 minutes with no detrimental effect on the effluent
quality. To determine the effect of power failure on the system, the reactor was shut down
for a period of. 17 hours and repeated at a later date for a period of 25 hours. Within 45
minutes and 15 minutes respectively, after start-up, the system was again achieving 99%
removal. During a high nitrogen concentration study, the influent oxidized nitrogen
averaged 55 mg/1 and the effluent 2.5 mg/1 for an overall removal of 95%. On two days of
this study, however, insufficient methanol was fed to the reactor. If these two days are
excluded from the average, the removal of nitrogen was 99%. A run was also performed on a
simulated industrial waste with NO,-N concentrations of up to 130 mg/1, and excellent
removals were obtained. Operation during the winter months with temperatures as low as 8
to 12 C did not significantly affect the performance of the unit.
During the latter portion of the study, a 13,600 gpd sf sand separation tank and a 4,600
gpd/sf settling tank were added to the pilot facility. The sand separation tank was used
successfully to return back to the denitrification reactor any sand which might escape in the
effluent. The settling tank, at this high loading rate, was able to remove all the suspended
solids, which averaged about 10 mg/1, produced by the denitrification unit.
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