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Simcoe
REGIONAL MUNICIPALITY OF HALTON
BURLINGTON WATER PURIFICATION PLANT
REPORT ON THE FEASIBILITY OF
ODOUR CONTROL BY POWDERED ACTIVATED CARBON
SIMCOE ENGINEERING LIMITED
MAY, 1981
Simcoe
REPORT ON THE FEASIBILITY OF
ODOUR CONTROL BY POWDERED ACTIVATED CARBON
INTRODUCTION
In October, 1979, Simcoe Engineering Ltd. prepared a report
entitled "Report on the Feasibility of Tertiary Treatment by Activated
Carbon" which outlined the use of granular activated carbon (GAC) as a
bed replacement for filters 1 - 7 at the Burlington Plant, to control
odour levels in the finished water. That report briefly addressed the
possibility of using powdered activated carbon (PAC) and noted that
"PAC treatment is not a viable treatment, except under virtual emergency
conditions".
A major drawback of the suggested GAC scheme was the require-
ment for a large capital investment for mechanical alterations and
granular carbon purchase estimated in 1979 to total $400,000.
This report will consider the alternative of PAC treatment
which will have a significantly lower initial cost.
PROPOSED TREATMENT
Since no data are available to indicate what dose of PAC
would be appropriate for use at Burlington, and the use of PAC is not
widespread with water from Lake Ontario, the opinion of the MOE Research
Laboratory was obtained as to the likely carbon dose which would prove
effective. Their opinion was that a dose of 5 - 10 ppm PAC would be
effective.
Typically, odour problems occur in periods of the year where
plant output is approximately equal to average day flow, and these
incidents are of less than four days duration.
The proposed treatment considered therefore i this report
is to store PAC in the new chemical building, together with an appropriate
slurry preparation and feed system, in the unallocated area south of the
Simcoe 2.
alum tanks. Sufficient PAC would be stored to allow four days continuous
treatment at average day flow at a dose of 10 mg/L PAC.
PROCESS CONSIDERATIONS
The use of PAC for odour control is widespread at treatment
plants where sedimentation is one of the processes used. A major disad-
vantage of the use of PAC at direct filtration plants is that all of the
PAC added to the raw water must be removed by the filters, thus increasing
the solids load to the filters and reducing the quantity of water which
can be filtered before the filter needs to be backwashed.
A preliminary estimate of the effect on quantity of water
filtered between washes, for doses of powdered carbon up to 10 mg/L
indicates that filter runs weuld be reduced approximately 25% for normal
raw water turbidity levels. Prior to any commitment to the PAC treatment,
testing should be done at the Burlington plant to verify this estimate,
and provide data to assess the effect of PAC at other doses. This testing
could be conducted at pilot scale.
OTHER CONSIDERATIONS
The potential problem of powdered material consolidating during
long-term storage was discussed with a supplier and the MOE Research
Laboratory. Both sources stated that the material would retain its free-
flowing characteristics even when stored for long periods.
Another consideration is the problem of handling of the material
which is finely divided and liable to produce large quantities of dust
if not handled carefully and with appropriate equipment. This matter
was discussed with an equipment supplier who proposed a proprietary
system which we believe would be satisfactory for the Burlington plant,
for an installed cost estimated at $85,000.
SUMMARY
The following table, a comparative cost analysis, indicates the
estimated annual costs for PAC treatment at two rates and for GAC treatment
Simcoe
as described in our 1979 report, costs shown are current,
COMPARATIVE COST ANALYSIS
GAC SYSTEM PAC SYSTEM
5 mg/L 10 mg/L
Total estimated capital cost 350,000 - 85,000 85,000
Provincial subsidy @ 15% 50,000 12,500 12,000
Net capital cost $300,000 $72,500 $72,590
Annual cost of debentures
10 years @ 16% 15,000 15,000
Annual power cost* - i
Annual chemical cost ** 5,000 10,000
Total annual cost $63,000 $20,000 $25,000
* based on ten days/year carbon treatment
** based on bulk costs of $1.10/kg.
From this table it is apparent that, provided the operation of
the filtration plant with shorter filter runs is acceptable, PAC treatment
is a less costly option than GAC treatment, and would provide equivalent
finished water quality.