Wastewater, comTABLE 1 - FLOW DATA(mVd) jVlaximum
Minimum
Dally
Daily
Average Daily
filter bed and the reject water contain ing the removed solids is piped off to the plant inlet works for further treat
ing the test period are summarized in
ment. The unit is constructed of 304
tal phosphorous concentrations of raw sewage and final effluent, as well as the removal efficiency during the test pe
Flow
Flow
Flow
Average
373
164
224
High
593
201
252
The final plans and specifications
Low
242
103
176
for the new Indian Road WPCP were
stainless steel in a rectangular, lateral mode.
prepared by TSH and submitted to the MOB for approval in 1993. However, mechanical components than other con tinuous backwash systems, but the de sign configuration and adjustable wash rate were best suited to this plant. Moni tored head loss, automatically adjusted wash rate and reject water rate were important considerations for this plant design. The Toveko filter, which performs two simultaneous filter operations (fil tration and sandwashing), has been used in many industrial wastewater and sew age treatment plants in Europe as a ter tiary filter process. The liquid to be fil tered enters an inlet shaft which traverses
the length of the filter and uniformly dis tributes the liquid from the bottom of the bed to the entire sand bed through a series of distribution channels. As the
influent is filtered through the bed, sus pended solid materials are separated or entrapped and remain in the sand bed. The filtered water then exits the filter
through V-notch weir openings located along the entire length of the filter. A small amount of air is continuously supplied to an air lift which conveys the sand containing the entrapped solids from the bottom of the filter up to an open screw sand washer assembly lo cated above the filter. The sand is trans
ported to the base of the washer where the sand slurry is introduced to the ro tating screw. As the screw rotates, the sand grains are slowly rubbed together
as no Toveko filters had been installed
if the equipment would achieve a total effluent phosphorous concentration be low 0.3 mg/L. The MOB issued a Cer tificate ofApproval conditional upon the District submitting a performance report covering full-scale plant testing of the continuous contact effluent filtration
system, at design peak flow conditions, over a 12-month period. Performance Testing of Tertiary Filter The construction of the plant was completed in 1996. In order to comply
period, together with the MOB effluent objectives, are summarized in Table 3. Conclusions
It is noted that during the full-scale
plant testing, the average effluent BODj, suspended solids and total phosphorous concentrations were 1.96 mg/B, 2.34 mg/B and 0.09 mg/B respectively which more than satisfy the MOB effluent ob jectives of 10 mg/L, 10 mg/L and 0.3 mg/L respectively. The plant perform ance test report was submitted to the MOB in October 1997, to comply with the Certificate of Approval. The District Municipality of Muskoka plant operations staff have reported
TABLE 3- SUMMARY OF AVERAGE EFFLUENT QUALITY IN COMPARISON WITH MOE OBJECTIVES
Average Effluent During Test Period
Effluent Parameters
undertaken be BOD, tween August 1996 Suspended Solids and July 1997 with only one train of Total Phosphorous the process unit in operation. The total rated capacity of
the plant is 550 mVd with the incorpo ration of two filtration units. Since the
plant operated with only one train of the process filtration unit, the capability of the plant was limited to 275 mVd dur ing the test period so as not to exceed peak filtration capabilities. A liquid alum dosage of approximately 60 mg/L was added to the final clarifier inlet
channel for precipitation of total phos phorous. The average daily flow, maximum daily flow and minimum daily flow dur-
sand is then evenly redistributed to the
riod, are summarized in Table 2. The average effluent quality at the new Indian Road WPCP during the test
with the Certificate
of Approval re quirement, fullscale plant testing ofthe tertiary filtration system was
conveyed to the top of the washer where ated solids from the sand. The cleaned
The BODj,suspended solids and to
in Ontario or Canada, it was not known
to liberate the solids. The sand is then
rinse water is added to wash the liber
Table 1.
MOE Effluent
(mg/L)
Objectives (mg/L)
1.96
10
2.34
10
0.09
0,3
satisfaction with the operation of the Toveko filters. The receiving surface water quality is showing no impact and is aesthetically showing improvement. TSH has since used this type of ter tiary filter in other sewage treatment plants currently in operation or under design. These plants are located in the community of Komoka in the Township of Lobo and the Village of Benelon Falls.
For more information,
circie repiy card No. 155
TABLE 2- BOD3,SUSPENDED SOLIDS AND TOTAL PHOSPHOROUS REMOVAL EFFICIENCY BOD, Month
Average
Suspended Solids
Total Phosphorous
Raw
Final
Removal
Raw
Final
Removal
Raw
Final
Removal
Sewage (mg/L)
Effluent
Efficiency (%)
Sewage (mg/L)
Effluent
Sewage (mg/L)
Effluent
(mg/L)
Efficiency (%)
Efficiency (%)
(mg/L)
(mg/L)
87.58
1.96
97.76
84.38
2.34
97.23
2.56
0.09
96.48
High
179.25
3.00
99.37
127.75
3.20
98.78
4.26
0.16
99.04
Low
44.33
1.10
94.04
45.00
1.50
94.96
1.21
0.03
86.78
32
Environmental Science & Engineering, June 1998