414
W. Torpey, H. Heukelekian, A.J. Kaplovsky, and R. Epstein
during this three stage operation has been compared in Table 2 with the first three stages
of operation when stage 1, alone, was equipped with a hood. In the first period the
B.O.D.S of the influent was reduced by 86% while in the latter period a B.O.D. 5
reduction of 90% was effected by three stages of treatment. Improved results were also
noted with respect to the parameters of T.O.C. and S.O.C. In conjunction with the latter
operation it was found that a substantial amount of nitrification, that is 7.6 mg/1 of
nitrates, were produced in stage 3. Under these specific operating conditions not only had
nitrification been brought upstream but the rate was increased substantially.
During the 2 year period of operation there were no biological upsets which would
deteriorate the quality of the effluent. Considering the normal range of variation of the
influent, the daily profiles through the treatment system show that the maximum
B.O.D.5 of the effluents exceeded the average by not more than 10 mg/1.
Referring to Table 1, base period, stages 6 to 10 produced 10.5 mg/1 of nitrates or 2.1
mg/1 per stage during 6 minutes of contact. When operating with oxygen enrichment over
stage 1, stages 4 to 7 oxidized 8.7 mg/1 or 2.2 mg/1 per stage. The oxidation of ammonia
by these fixed slimes followed zero order kinetics. According to Jenkins (2) a survey of
activated sludge plants in England disclosed that a maximum rate of 4.2 mg/1 of nitrogen
was oxidized per hour of contact with a mixed liquor solids concentration of 7000 mg/1.
Comparison of the operating results for summer and winter months did not indicate
any substantial difference in the rate of nitrification, that is within the temperature range
of 62 to 78°F. Since these findings are in conflict with the observations of various
investigators regarding the effect of temperature on nitrification, it is believed that other
factors such as the influence of predation exerted a compensating effect. Predatory
activity was suppressed during the colder months leaving a greater coverage of the
surfaces by nitrifying slimes.
In the upstream stages of treatment which are concerned with removal of
carbonaceous matter the nitrifiers cannot propagate as they are smothered and starved for
oxygen by heterotrophic organisms.
After the bulk of carbonaceous matter had been removed down to a B.O.D.5 level of
15 mg/1, a highly specialized nitrifying culture, brown in color, developed on the disk
surfaces, was able to utilize the ammonia in the stream as its source of energy. The
attached nitrifying culture was self-regenerating and not wasted as in the case of using a
suspended culture to oxidize carbon and nitrogen. However, the low growth rate of
nitrifiers, in the presence of a predator population results in the periodic development of
bare spots on the disk surfaces.
SUMMARY
The results of operating a 41,635 liter per day staged rotating disk pilot plant have
been presented for three modes of operation, namely, (1) the slimes in all stages exposed
to ambient atmospheres, (2) the slimes in stage 1 exposed to oxygen enrichment, and (3)
the slimes in stages 1 and 3 of a 3-stage operation exposed to oxygen enrichment. The
first mode of operation about 30 minutes of contact with the slimes was sufficient to
remove 90% of the B.O.D. 5 whereas the second mode of operation 18 minutes
accomplished the same rate of removal of B.O.D. s . In the third mode, not only was 90%
of the B.O.D.5 removed during 18 minutes of contact with the slimes but a substantial
portion of the nitrogenous demand was satisfied.
W. Torpey, H. Heukelekian, A.J. Kaplovsky, and R. Epstein
during this three stage operation has been compared in Table 2 with the first three stages
of operation when stage 1, alone, was equipped with a hood. In the first period the
B.O.D.S of the influent was reduced by 86% while in the latter period a B.O.D. 5
reduction of 90% was effected by three stages of treatment. Improved results were also
noted with respect to the parameters of T.O.C. and S.O.C. In conjunction with the latter
operation it was found that a substantial amount of nitrification, that is 7.6 mg/1 of
nitrates, were produced in stage 3. Under these specific operating conditions not only had
nitrification been brought upstream but the rate was increased substantially.
During the 2 year period of operation there were no biological upsets which would
deteriorate the quality of the effluent. Considering the normal range of variation of the
influent, the daily profiles through the treatment system show that the maximum
B.O.D.5 of the effluents exceeded the average by not more than 10 mg/1.
Referring to Table 1, base period, stages 6 to 10 produced 10.5 mg/1 of nitrates or 2.1
mg/1 per stage during 6 minutes of contact. When operating with oxygen enrichment over
stage 1, stages 4 to 7 oxidized 8.7 mg/1 or 2.2 mg/1 per stage. The oxidation of ammonia
by these fixed slimes followed zero order kinetics. According to Jenkins (2) a survey of
activated sludge plants in England disclosed that a maximum rate of 4.2 mg/1 of nitrogen
was oxidized per hour of contact with a mixed liquor solids concentration of 7000 mg/1.
Comparison of the operating results for summer and winter months did not indicate
any substantial difference in the rate of nitrification, that is within the temperature range
of 62 to 78°F. Since these findings are in conflict with the observations of various
investigators regarding the effect of temperature on nitrification, it is believed that other
factors such as the influence of predation exerted a compensating effect. Predatory
activity was suppressed during the colder months leaving a greater coverage of the
surfaces by nitrifying slimes.
In the upstream stages of treatment which are concerned with removal of
carbonaceous matter the nitrifiers cannot propagate as they are smothered and starved for
oxygen by heterotrophic organisms.
After the bulk of carbonaceous matter had been removed down to a B.O.D.5 level of
15 mg/1, a highly specialized nitrifying culture, brown in color, developed on the disk
surfaces, was able to utilize the ammonia in the stream as its source of energy. The
attached nitrifying culture was self-regenerating and not wasted as in the case of using a
suspended culture to oxidize carbon and nitrogen. However, the low growth rate of
nitrifiers, in the presence of a predator population results in the periodic development of
bare spots on the disk surfaces.
SUMMARY
The results of operating a 41,635 liter per day staged rotating disk pilot plant have
been presented for three modes of operation, namely, (1) the slimes in all stages exposed
to ambient atmospheres, (2) the slimes in stage 1 exposed to oxygen enrichment, and (3)
the slimes in stages 1 and 3 of a 3-stage operation exposed to oxygen enrichment. The
first mode of operation about 30 minutes of contact with the slimes was sufficient to
remove 90% of the B.O.D. 5 whereas the second mode of operation 18 minutes
accomplished the same rate of removal of B.O.D. s . In the third mode, not only was 90%
of the B.O.D.5 removed during 18 minutes of contact with the slimes but a substantial
portion of the nitrogenous demand was satisfied.