DESIGN CONSIDERATIONS FOR
EXTENDED AERATION  IN ALASKA
  FEDERAL WATER QUALITY ADMINISTRATION
                    NORTHWEST REGION
             ALASKA WATER LABORATORY
                         College, Alaska

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      DESIGN CONSIDERATIONS FOR EXTENDED AERATION IN ALASKA*

                              by

                        Sidney E.  Clark
                        Harold J.  Coutts
                       Conrad Christiansen
               FEDERAL WATER QUALITY ADMINISTRATION
                      ALASKA WATER LABORATORY
                         College, Alaska
*Paper presented at the International  Symposium for Cold Regions
 Water Pollution Control, University of Alaska, Institute of
 Water Resources, July 22 to 24, 1970.

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A Working Paper presents results of investigations
which are to some extent .limited or incomplete.
Therefore, conclusions or recommendations-.-expressed
or implied—are tentative.

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                               CONCLUSIONS

The feasibility of the extended aeration activated sludge process
as a relatively economical and effective means of secondary waste
treatment has been demonstrated in the laboratory and in the field.
  \
The process requires more consistent operation and maintenance than
aerated lagoons and this is a disadvantage where costs are high and
skilled operators are extremely scarce.

The Utilization of exposed aeration chambers for the extended aeration
process is feasible.  Earthen basins are also feasible for use where
economic and construction conditions warrant.  When utilizing exposed
basins, heat loss effects must be evaluated in conjunction with deten-
tion time determinations to avoid potential freezing problems.  Solids
entrainment in ice can cause failure of an activated sludge process.

Environmental protection in varying degrees should be provided for
the remaining equipment, such as heated enclosures for pumps and flow
measurement devices.  Housing must be provided for secondary sedimenta-
tion basins and should include a minimum of an unheated structure with
panels which can be removed for warm weather operation.

Effective solids separation is the key to successful operation of
extended aeration facilities and is dependent on both the biological
and physical aspects of the system.  It has been demonstrated that a
sludge can be developed which will perform very efficiently at tem-
peratures <1°C.  A turbid effluent will result at cold temperatures

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 with an unacclimated sludge or loading  rates  that are  too  high.   Under
 these conditions,  a less  stabilized sludge  develops  with a corresponding
 relative decrease  in numbers of stalked ciliates  and an increase  of  dis-
 persed bacteria which appears to contribute to turbidity (22).

 A bulking sludge may develop at cold operating temperatures.  This
 type of sludge can lead to separation problems but will provide a very-
 clear effluent at  temperatures ranging  down to less  than 1°C.

 Properly designed  tube settlers will provide  effective cold (0 to 4°C)
 temperature solid  separation.  This is  true for sludges with SVI's
 ranging up to 250.  A backwash cycle should be provided for reliable
 operation and is mandatory for operation with high MLSS concentration
 (4000 mg/1) and bulking sludges.,.  Some  effort should be directed
 toward developing  upflow clarifier configurations for cold temperature
 application since  the method has advantages (27). The tube settler
 does provide an upflow cVarifier type action  in high MLSS  activated
 sludge solid separation applications.   Providing  consistent solids
 separation with tube settlers at warmer temperatures (greater than 4°C)
 appears to be the  most demanding and yet insufficiently defined area
•of need in their application.

 Cold climate sludge wasting and disposal for  the  extended  aeration
 process must be given consideration for the following reasons:

 (1)  Excess solids production increases with  decreasing temperature.

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 (2)   Shorter  detention times  to prevent freezing will also increase
X,                             '-i.
 solids  production at  a given  MLSS level.



 (3)   Auto  induced sludge wasting may be expected to be more severe,

 placing greater potential stress on the receiving water.



 (4)   Retarded assimilative capabilities of the receiving water at

 cold  temperatures.

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                          RECOMMENDATIONS

Facility Design


The following design recommendations are based on laboratory studies,

experience with the Eielson Air Force Base pilot facility, and experience

reported by others:

                                                             I
                                                             !
(1)  Exposed aeration basins should be considered for reducing con-

struction costs of waste treatment facilities.  Raw sewage temperatures

and heat loss effects must be considered to prevent freezing which can

cause process failure by entrainment of solids from the system.


(2)  Housing should be provided for pretreatment units such as bar racks,

pumps and flow measuring equipment.


(3)  Some minimum protection should be provided for aeration equipment

such as strip heaters or minimum heat enclosures for compressors and

unheated housing for oxidation ditch rotors.


(4)  Housing should be provided for secondary sedimentation basins.

Minimum housing would include a structure with panels which may be

removed for warm weather operation.


(5)  Where economic and construction considerations warrant, earthen

basin designs should be considered for aeration chamber construction.

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Otherwise, sidewalls that are vertical  or near the angle  of repose
should be utilized to promote better mixing.


(6)  Submerged settling units should be situated in the center  of
basins with low sidewall  construction with aeration on at least two
sides to promote adequate mixing.   Several questions require answers
before submerged settling units are practical.


(7)  When basins with low sidewall  slope construction are utilized
                  f
without submerged settling units,  the aeration devices should be clus-
tered in the center of the basin for best mixing.


(8)  Flexible membranes should not be used where the danger of  heavy
icing exists.


(9)  Concrete block and concrete grout  should be considered as  econom-
ical liner materials where the design permits.


(10)  Tube settlers with  backwashing of tubes should be given consid-
eration for both submerged settling units and sedimentation basin
installations, however, more information is necessary before their
reliability is predictable.   Effective  methods must be provided for
removal of settled solids from the unit for recirculation.   Lack of this
capability will result in poor tube settler performance.   Considerable
thought must be given to  maintenance, both routine and emergency, prior
to and during the design  phase for tubesettlers to be useful.

Process Design

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The following preliminary recommendations for. low temperature extended
aeration systems are. based on laboratory studies and experience re-
ported by other investigators.   Attempts will  be made to verify these
findings on a pilot plant scale.

(1)  Organic loadings should be maintained below ^ 0.20 #BOD/#MLVSS-
Day.  More studies are necessary at higher F/M values, especially up
to 0.4 #BOD/#MLVSS.

(2)  Provision should be made for sludge wasting of ^ 0.5 #MLSS/#BOD
removed, particularly at shorter detention times such as a 12 hour
detention time system.  Further studies are necessary to determine
temperature and detention time  influences.
                                                                p
(3)  Tube settler overflow rates-should be held below 0.5 gpm/ft  with
high MLSS concentrations (^ 4000 mg/1).
(4)  Sludge wasting and disposal  facilities or a polishing lagoon  for
effluent discharge should be provided where heavy discharges  of sus-
pended solids may place excessive stress on receiving waters.

Research and Development Needs

The following list of suggested research and development needs is  not
intended to be all inclusive but includes areas which have come to
the attention of the authors through laboratory and pilot plant ex-
perience and a review of experience reported by other investigators:

(1)  Sludge bulking conditions at lower temperatures (^ 8°C and below)
must be defined so the condition can be predicted in actual application,

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 (2)   Further develop  low temperature  bio-kinetic parameters at detention
-times ranging from 4  to  36  hours  and  varying MLSS levels.

 (3)   Further develop  low temperature  tube  settler design criteria and
 backwashing techniques at various MLSS  levels.

 (4)   Investigate  upflow  clarifier designs  for  low temperature appli-
 cation.

 (5)   Investigate  methods of sludge digestion .and disposal under low
 temperature conditions;  particularly  the use of the freeze-thaw cycle
 as  an aid to promoting better  drainability.

 (6)   Develop reliable methods  for positive recirculation of settled
 solids from submerged settling units.

 (7)   Further investigate criteria for predicting heat loss from ex-
 posed basins.

 (8)   Continue evaluation of cold  temperature bio-kinetic design para-
 meters on pilot plants and  existing facilities.

 (9)   Develop design and  operation criteria for low temperature hori-
 zontal flow clarifiers.

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(10)  Investigate power requirements and mixing characteristics  of
various earthen basin configurations.

(11)  Further investigate the effects  of heavy ice cover on solids
entrainment in aeration basins, particularly where flow patterns are
parallel to the surface as in the oxidation ditch.

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                           INTRODUCTION

Alaska is the largest state of the United States,  sparsely populated
and with a variety of climates, including arctic,  subarctic,  marine sub-
arctic and temperate.  The population is small  and widespread with
294,417 people (preliminary 1970 census figure) inhabiting 586,000
square miles of land area.  Settled areas requiring domestic  sewage
treatment include large municipalities, military installations,  remote
sites and villages, each of these having different requirements  and
presenting different problems.

Construction and power costs in Alaska are very high in general, and
excessively so in remote areas (1.5 to 5 times  Seattle  construction cost
index).  Skilled personnel for operation of treatment plants  are scarce
and, in most cases, nonexistent.

The effect of man's waste on Arctic and Subarctic  ecosystems  has re-
ceived little attention in the past and is not  well understood.   Because
of recent increased interest in the Arctic region, some information is
now becoming available on man's possible influence.  For example, during
the winter, dissolved oxygen (DO) of ice-covered Alaska rivers may reach
extremely low levels of 3 mg/1 or less under natural conditions  (10,  12,
28).  Because of the retarded ability of Alaska streams to replenish  DO
under total or nearly total ice cover, it becomes  essential that the
natural balance not be upset by man.  Under these  conditions, high level
secondary sewage treatment will be required to  assure adequate stream
protection.

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 One of the major advantages  of  biological  processes for provision of
'secondary treatment is  their ability  to  oxidize waste without large in-
 puts of energy,  thus reducing shipping costs, etc., associated with
 materials required  for  chemical  treatment.  All factors considered,
 extended aeration systems  have  considerable potential for reliable
 and economical  secondary treatment  at larger governmental installations
 and larger communities  in  Alaska  (populations greater than 250).

 Current extended aeration  research  is being conducted by several groups:

 1.   Corps of Engineers
         Cold Regions Research and Engineering Laboratory
         Alaska  District
 2.   University  of Alaska
         Institute of Water Resources
 3.   Federal  Water Quality  Administration,  Alaska Water Laboratory
         Cold Climate Research Program

 Waste treatment research at  the Alaska Water Laboratory is concerned
 primarily with  adapting methods developed  in the contiguous United
 States to the extreme cold climates found  in Alaska.  The scope of the
 present work, on  activated  sludge  is.  in  general, limited to extended
 aeration, and includes  investigations in the following areas:

 1.   Low temperature bio-kinetics
 2.   Low temperature solids removal

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3.  Degree of environmental  protection required for equipment and
processes.
4.  Aeration requirements
5.  Aeration chamber mixing
6.  Waste sludge characteristics and disposal

The above investigations are being conducted on a laboratory and pilot
plant scale.  Monitoring of  existing facilities is also taking place.

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                 LITERATURE AND EXPERIENCE REVIEW

Low Temperature Biological Treatment Feasibility

Although the activated sludge process is affected by temperature,
operation at temperatures approaching freezing is feasible.  A number
of investigators have reported a considerable amount of biological
activity taking place at freezing temperatures and below (3, 15).
Miller (23) has reviewed the information available on microorganisms
indigenous to cold environments and found that research on psychro-
philic organisms is still in the initial stage, but concluded that
"truly psychrophilic microorganisms do exist and are distinguished by
their ability to grow at very, low temperatures and to do so at rates
comparable to those of mesophiles at higher temperatures."  The feasi-
bility of effective biological treatment by full-scale extended
aeration facilities at operating temperatures as low as 2°C has been
demonstrated (2, 13, 30).

Temperature Effects

Pasveer (24) conducted laboratory scale temperature studies with
activated sludge and reported that the process goes on almost as well
at 3-5°C as it does at 20°C.  Wuhrmann (34), found in his studies of
the activated sludge process that "the BOD removal-seems to be only
slightly influenced by temperature, whereas nitrification is markedly
higher in summer than in winter."  Ludzack (21) conducted bench scale

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 studies  using a  continuous  apparatus  with  a  detention  time of  24
"hours  and a loading  of  35#  COD/1000 ft3  and  demonstrated  COD re-
 moval  efficiencies of <90%  at  21-25°C, 90% at  10°C and 84% at  5°C.
 Hunter et al . (19) conducted batch operated  laboratory scale studies
 on  the effect of temperature and  retention times on  the activated
 sludge process.   At  temperatures  between 4°C and 45°C, they found
 little change of BOD or suspended solids removal efficiencies.  As
 the temperatures increased, they  found less  filamentous growth  and
 increased protozoa and  rotifer populations.  Grube and Murphy  (13)
 evaluated an  oxidation  ditch and  found BOD removal efficiencies
 greater  than  90% with liquid temperatures  of 2°C, air  temperatures
 ranging  down  to  -40°C,  and  average detention times of  2.3 days.
 Influent temperatures averaged 16.6°C with a minimum of 7.5°C.
 Gustaffson and Westbury (14) evaluated the activated sludge process
 for application  at Kiruna,  Sweden, and obtained 75%  BOD reduction
 with a 3 1/2  hour detention time  system  at 2.8-4.8°C and  2700-3500
 mg/1 MLSS.

 Temperature Coefficient

 The temperature  coefficient, e, is used  in the relationship
                         k1/k2  =  e  (t]  -  t2)

 to define the effect  of temperature  on biological  activity.   The
 values k-j and V.%  refer  to  velocity constants  at  temperatures  t-j and

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respectively.  The value of e indicates the extent of the temperature
effect on the biological activity.   Use of this equation, known as
the Arrhenius relationship, to define the effect of temperature on
wastewater and reaction rates, dates back to Streeter and Phelps (1925)
and Theriault (1927), who reported e values of 1.047 for domestic waste-
water and river water (35).  Pohl (25) concluded that 0 was dependent
on the mixed liquor concentrations:   e = 1.038 at low MLSS and 1.000
at high MLSS.  Benedict (4) conducted studies in the temperature range
of 4-32°C and concluded e (e = 1.078 @ 4°C) was independent of loading
when the loading rate did not exceed 0.53 Ibs BOD/day/lb/MLSS, but  e
increased as loadings above .0.53 were imposed.  Eckenfelder (8)
suggested that e, based on overall  treatment efficiencies, was a
function of the organic loading and  reported e values for activated
sludge of 1.00 at low loadings and 1.02 at high loadings.

Solids Separation

Solids removal plays a very important part in the efficiency of the
activated sludge treatment process.   The degree of sludge separation
directly influences the quality of effluent from wastewater treatment
plants with higher concentrations of effluent solids contributing to
high effluent BOD.  Reed and Murphy  (27) conducted an investigation
on settling characteristics of activated sludge at temperatures ranging
from 1.1 to 23.4°C and found that the influence of temperature on
settling velocity decreased as the concentration increased.  They de-
veloped an equation for zone settling based on experimental data.  They

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also suggested upflow sludge blanket clarifiers as having greater
potential for cold regions application.  Benedict (4)  suggested that
the effect of sludge settleability on gross COD removal  was magnified
at low temperatures and as the-loading rate was increased.

Hansen (16) reported on a method of solids separation  which success-
fully employed shallow depth sedimentation theory.  The settling units
consisted of small diameter tubes (1-inch) inclined at 5° and 2-4 feet
in length.  Detention times were very short and backwashing was
necessary for removal of accumulated solids.  Hansen (17) also reported
on the use of steeply inclined tubes (60°) which permit solids deposit-
ed in the tubes to continuously slide down by gravity.  A secondary
clarifier of a trickling filter plant was converted to a biological
reactor and the steeply inclined tubes utilized for solids separation
which increased plant efficiency from 85 percent to more than 95 per-
cent.  The effluent suspended solids averaged 70 mg/1  varying from a
low of 7 mg/1 to a high of 190 mg/1 which was comparable to those
produced by a conventional clarifier of an extended aeration plant of
the same capacity (3000 gallons per day at 12-hour detention).  Other
reports are available which descirbe the use of tube settlers in
water treatment and waste treatment solids separation  (6, 29).

Pohl (26) investigated tube settlers in the laboratory and obtained the
best results at room temperature but found the tubes passing excessive
collodial solids occasionally.

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Design Parameters

Little imformation is available on biological  treatment process  design
for temperatures less than 5°C.  Ludzack (21)  and Hunter,  e_t  a]_.  (19)
observed that excess MLSS accumulation increased  with  decreasing temper-
ature.  The cell yield (c) increases with increasing  temperature
because it is believed a larger portion of BOD removed is  utilized  for
energy at low temperatures than at high temperatures  (32).  Since the
rate of endogenous respiration is depressed at low temperatures,  the
quantity of excess sludge produced is increased.   Benedict (4) reports
values for c and k (endogenous rate) at 4°C of 0.42 mg/mgCOD  and 1.32
percent respectively.

Aeration

Eckenfelder and O'Connor (9)  stated that the temperature coefficient
9, when applied to oxygen transfer efficiencies,  has  been  reported  to
vary from 1.016 to 1.047 and  that studies on bubble aeration  indicated
a temperature coefficient of  1.02 applied.  The effects of temperature
on stream reaeration has been studied under controlled experiments  in
the laboratory (1).  A value  for 9 of 1.0241 for  the  temperature range
of 5 to 30°C was found.  Black (5) described a procedure for  evalua-
tion of aeration devices and  stated that a 9 value of  1.030 or higher
should be used for cold water.

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    ALASKA WATER LABORATORY PILOT PLANT AND LABORATORY STUDIES





Laboratory Studies







During the past two years, three bench scale activated sludge reactors



have been utilized for kinetics and solids separation studies.  The



three units are illustrated in Figures 1, 2, and 3.   The systems have



been operated as continuous flow through systems with the feed being



primary effluent brought to the laboratory from the  Eielson primary



sewage treatment plant.  Routine analysis included influent and



effluent BOD and COD, mixed liquor and effluent suspended solids (SS)



and volatile suspended solids (VSS).  Nutrient analysis of the influent



and effluent samples were made weekly and included ammonia, nitrite,



nitrate, organic nitrogen, total phosphates and orthophosphates.  A



limited number of coliform counts were made on the influent and



effluent.  Microscopic examinations of the reactor contents were made



on an irregular basis at times when apparent or suspected changes in



the mixed liquor had taken place.  The examinations  consisted of



general observations on the relative quantities of protozoa present



and the degree of activity.  BOD, COD, and solids analyses were done



in accordance with Standard Methods procedures (31).  Coliform counts



were made by the membrance filter method as described in Standard



Methods and nutrient analyses were made in accordance with Federal



Water Quality Administration Standards (11).

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The cone reactors (Figure 1), when operated at 1.3°C and 6.5°C for
long periods of time, showed some interesting characteristics which
are summarized in Tables 1 and 2.  Both biological sludges were rel-
atively easy to establish.

The reactor runs started with the longest detention time first and
the times decreased in chronological order.  The 1.3°C reactor took
a considerable amount of time to establish a stable system (more
than 3 months).  However, a good removal rate was obtained before
the MLSS stabilized.  There was apparently little difference in the
biological activity at the two temperatures, but, operation of the
reactor at 6.5°C was more erratic.

Both reactors generally showed "auto induced slude wasting" in the
same manner as the College Utilities oxidation ditch described by
Grube and Murphy (13).  The MLSS would build up to a point and begin
to pass solids for 1 or 2 days and then repeat the cycle.  The cycle
was repeated within 2 to 3 weeks as opposed to the monthly occurrence
reported by Grube and Murphy.

The reactors differed in their manner of passing solids, with the
1.3°C reactor generally having a much more turbid effluent and the
6.5°C reactor having a relatively clear effluent.  Heavy solids
passed from the 6.5°C reactor by rising in the settling tube as a
solid mass.  As the concentrations of solids in the mixed liquor

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increased, the level of solids in the settling tabe would rise until
spilling over into the effluent tank.  After passing an undetermined
amount of solids, the cycle would be repeated.  A gradual drop in pH
was noted in the 6.5°C unit as the suspended solids began to build
before discharging.  The pH dropped from slightly above 7 to values
of 6.6 to 6.7.  pH of the 1.3°C unit consistently remained around
7.4.  The 6.5°C effluent solids settled to the bottom of the effluent
tank leaving a clear liquid above, whereas, the 1.3°C effluent solids
did not settle out to any degree.  As the 1.3°C reactor became more
stabilized, the effluent became less turbid and the MLSS began to
increase.  The 6.5°C reactor operation was less stable, with the
maximum level of MLSS generally not rising above 2300 as opposed to
3000 for the 1.3°C MLSS.  Results of nutrient analysis are presented
in Table 3.  There was a significant change in nitrate and total
nitrogen at 6.5°C when going from 9 to 13 hours detention time.  This
was also true at 1.3°C to a lesser degree.  There was a greater
reduction in ammonia nitrogen and a greater increase in nitrate
nitrogen at 6.5°C.  Ammonia was essentially not affected at 1.3°C.
Total nitrogen removals were much higher at 6.5°C than at 1.3°C with
little detention time effects.

Overall results of operation of the 8.9 gal and 12.45 gal reactors
are presented in Tables 4 and 5.  Temperature changes were accomplished
by a gradual increase or decrease in the constant temperature room
temperature.  These reactors were operated at 12-hour hydraulic detention

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times with daily sludge wasting to maintain the MLSS at 4000 mg/1.
The 8.9 gal reactor was later converted to a 24 hour operation.
Sludge was wasted by drawing off the required amount of mixed
liquor.  A portion was used for a solids analysis to determine the
exact amount of solids removed.  The effluent BOD and COD figures
of 9 to 21 mg/1 and 46 to 96 mg/1 indicate that a considerable
amount of biological activity takes place at low operating temper-
atures.

Effluent BOD/COD ratios varied from 0.13 to 0.27 indicating that
effluent organics were well oxidized.  These were in comparison
with the influent BOD/COD ratios of 0.55 to 0.66.

The amounts of sludge wasted varied from 0.42 m9 -»usp.  solids at
                                              mg BOD removed
the low temperatures to 0.14 at 10.5°C and 24 hour detention time.
The pH of both reactors ranged from 7.2-to 7.6 during the sample
periods reported.

Poor settling sludges were developed during operation of these
reactors with the Sludge Volume Index (SVI) consistently ranging
above 200.  The sludge produced appeared to be of a zoogeal  type
similar to that reported by Heukelekian and Wiesburg (18) who found
a direct correlation between increasing SVI and increasing bound
water for this type of bulking.  Very little evidence of Sphaerotilus

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was noted during microscopic examination.   Ludzack (21)  also  re-
ported a poor settling sludge at low temperatures  (5°C)  with  very
poor drainability.

The significance of protozoa in an efficiently operating activated
sludge process as reported by McKinney (22),  was observed during
operation of the reactors even at the coldest temperatures.   The
12.45 gal reactor was started at temperatures <2°C with  return
sludge from an oxidation ditch treating domestic sewage.  Initially,
the effluent was very turbid as the sludge was acclimating itself
to the new conditions.  The decreasing turbidity of the  sludge  as
acclimation progressed corresponded to increasing  numbers of
protozoa, generally Paramecium and Vorticella. As reported by
McKinney (22), a very well stabilized activated sludge system will
have few stalked ciliates and no other protozoa because  of relatively
few bacteria, whereas, a somewhat less stabilized  system will have
greater numbers of free swimming ciliates  because  of greater  numbers
of free swimming bacteria.  He stated that the presence  of stalked
ciliates indicates an activated sludge system with a low BOD  effluent.
Vorticella was present in both reactors after initial  startup except
for one period in the 12.45 gal reactor as described below.

After stable operation at temperatures <2°C and ^°C the 12.45  gal
reactor temperature was increased to 8°C over a period of 6 days.
The effluent suspended solids increased from approximately 5  mg/1

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before the temperature increase to approximately 18 nig/1  during
the increase and reached a maximum of 46 mg/1  after 3 days at 8°C.
During this period, the effluent became turbid with few solids set-
tling out in the effluent tank.'  The protozoa  became very reduced
in numbers and inactive.  Again, the return to normal operation
corresponded to an increase in the number of Vorticella and Parame-
cium present in the sludge.  Coliform removal  also corresponded
directly to the numbers of protozoa present, dropping from 99.8
percent removal before the upset to less than  80 percent during
the protozoa number reduction.  Ten days after returning to stable
operation at 8°C, the sludge was exhibiting the same characteristics
as with the 8.9 gal reactor.  That is, the SVI was ranging around
250 and the floe exhibited a fluffy snowflake  appearance.  Operation
of the reactor was not impaired under these conditions because a
backwash cycle was added to the settling apparatus.  Protozoa in-
creased in numbers when the systems stabilized at 12°C.

Sludge wasting and disposal in cold climates should be given attention.
Based on data presented earlier, it would appear that provision should
be made for wasting 0.5 Ib solids per Ib or BOD removed at colder
operating temperatures (<5°C) and at organic loadings of 0.1 Ib influent
BOD per Ib MLVSS-Day.  Sludge digestion and disposal methods present  a
problem at colder temperatures due to added heat requirements and poor
drainability.  Ludzack (21) indicated that sludge development at cold
temperatures may require digestion at higher temperatures before

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 disposal.   Thomas  (33)  indicated  the  freeze-thaw  cycle may  be  taken
"advantage  of in  cold  climates'to  increase  drainability.

 Tube settlers have  been evaluated as  a  possible alternate means of
 providing  solids separation  and return.  During operation,  sludge
 rises in the tubes  until  it  reaches a level  at which  it  is  in  equi-
 librium with the effluent flow.   Action  in the tube consists of a
 rolling motion in which solids are being carried  up along the  top
 side of the tube in a mass with the effluent, as  shown in Figure 4.
 The mass gradually  settles toward the bottom side of  the tube  where
 it enters  a current moving downward caused by the weight of the
 solids.  During  normal  operation, solids in the tube  are constantly
 being replaced at a relatively high rate (<3 hrs).  In the  temp-
 erature range of 0° through  4°C the SVI  of the mixed  liquor ranged
 around 230 and did  not  hinder the operation of the reactor.  At 8°C
 and above, the SVI  increased to values  of  260 and greater and  the
 sludge took on a fluffy snowflake appearance.  The rolling  action
 of the sludge in the  tubes stopped and  the sludge height began to
 rise eventually  spilling  out with the effluent.   Cutting the effluent
 flow rates, back  to  less than 0.2  gpm/ft2 resulted in  lowering  the
 DO in the  effluent  tubes  to  zero, which  further complicated the
 problem.  The studies indicate that some means for backflushing tube
 settler controlled  upflow clarifiers  must  be provided if mixed
 liquor concentrations greater than 2000 mg/1 are  to be achieved with
 reliable operation.

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 The  12.45 gal  reactor was  operated  for  a  period  of time with a very
 low  continuous overflow  rate  and  then increased  to an  average rate
 of 0.5 gpm/ft2 with  an alternating  on-off cycle.  In other words,
 with the on 1/2 hour—off  1/2  hour  cycle,  the  actual flow was 1 gpm/
 ft2  for 1/2 hour.  The SVI  again  ranged above  200 with very consistent
 solids removal. The effluent  solids concentrations were very low for
 the  whole range of studies.   The  longer on  times for the on-off cycle
 (2-1/2 hours on as opposed to  1/2 hour) did  indicate that longer cycles
 may  result in  higher effluent  solids concentration.  Summaries of the
 results obtained at  various temperatures  and overflow  rates are pre-
 sented in Tables 6 and 7,  and  Figures 5 and  6.   Adding a backwash cycle
 provided a definite  advantage  in  that it  prevented a bulky sludge from
 becoming stagnant in the tubes.

 Indications are that sludge bulking probably is  a general problem in
 the  activated  sludge process  at colder operating temperatures and special
 precautions in design will  be  necessary to  assure effective solids con-
 trol.   This problem  was  reported  by Ludzack  (21).  Bulking sludges have
 not  been reported in cold  temperature oxidation  ditch  studies (2,13);
 however, these ditches were operated at much longer detention times (1.6
'to 2.3 days) which may be  a factor.  Downing (7) showed that settle-
 ability is improved  by longer  detention time (>10 hrs) and very short
 detention time (<5 hrs)  when  operating an activated sludge plant at
 warm temperatures.   At any rate,  indications are that  backwashing in
 conjunction with lower overflow rates will  overcome this problem.

-------
Unless a polishing lagoon is employed, provision should be made for
sludge wasting.  These studies" indicate a probably maximum wasting
rate of around 0.5 #SS/#BOD removal.

Pilot Plant

In cooperation with the Alaskan Air Command, the Alaska Water Laboratory
constructed and operated a pilot waste treatment facility at Eielson  Air
Force Base (EAFB).  The facility included an aerated lagoon and an
extended aeration basin.  The purpose of the facility was to increase
the knowledge of biological  waste treatment at cold temperatures  and  to
develop design criteria.

Eielson Air Force Base is located 22  miles southeast of Fairbanks  and
has a similar subarctic climate.  The mean annual  temperature at
Fairbanks is approximately 25°F with  minimum and maximum recorded
temperatures of -66°F and +99°F respectively (20).  The area has
approximately 150 degree days below 0°F.

Originally intended to serve as  a facultative lagoon, the extended
aeration unit consisted of an earthen basin lined with 20 mil polyvinyl
chloride film (PVC) and tube settler  modules as shown in Figures  7 and
8.  The PVC film at the bottom of the basin was covered with 6 inches
of sand and a concrete pad poured in  the center for support of aerators.
Aeration and mixing were provided by  eight Hydroshear aerators, manu-
factured by the Chicago Pump Company.  Air supply was by a 120 SCFM
Sutorbilt blower, manufactured by the Fuller Company.

-------
Solids  separation was  provided  by two tube settler modules.  The tube
"settlers  were developed  by  Neptune Microfloc Company for use in water
treatment.   The manufacturer  has recently initiated studies to adapt
them  for  use in activated sludge separation (17).  This type of
settler was  felt to  provide optimum design for submerged operation
which was desired to overcome icing problems.  The basin was fed by a
Marlow  centrigal pump, manufactured by  ITT Marlow Company.  Pumping
rate  was  approximately 180  gpm  with the feed drawn from a manhole on
the influent line just before entry to  the EAFB primary treatment plant.
Temperature  of the sewage averages about 20°C with the sewer lines
enclosed  in  a utiliddr,  which is heated during the winter months.

The extended aeration  facility  as described was built to provide the
very  simplest operation  with  a  minimum  of environmental protection for
evaluation under cold  climate conditions.  Construction of the extended
aeration  facility was  completed in December 1968 and the unit placed in
operation later that month.   The unit was operated at a 2-day detention
time, which  corresponded to an  average  overflow loading rate on the
tube  settler of 1.3  gpm/ft^.  A problem was encountered with breakage
of pumps, due to entrained  solids entering the pumping chamber.  The
feed  line also filled  with  solid material and plugged.  As a result,
the basin was not fed  for a week, during which time 3 feet of ice
formed  over  the pond and frozen foam built up to 8 feet abover.the aer-
ator.

-------
 Beginning in January  1969  and  lasting approximately 6 weeks, a period


.of extremely cold weather  occurred with ambient air temperatures dropping


 as low as -60°F.  A detention  time of 1 day was maintained during this


 period with no  ice forming.  The  loading on the tube settlers was approx-

                  o
 imately 2.5 gpm/ft  .  The  gear housing of a compressor was broken and


 teeth stripped  from the  gears  while attempting to start it at a low


 temperature. Apparently,  metal contraction had reduced clearances which


 caused internal rotating parts to make contact with and break the pump


 housing.




 During February, the  feed  pumps were moved inside the Eielson primary


 treatment plant and feed taken from the grit chamber.  For the remaining


 of the winter and the following spring, while operating at a detention


 time of 2 days, the MLVSS  of the  system generally did not rise above


 500 mg/1.




 Inadequate mixing was suspected as the cause of poor performance, and


 velocity measurements were made with an ice current meter obtained from


 the M. S. Geological  Survey which measured the horizontal component only.




 Velocities were generally  lower than the 1.0 ft per second recommended


 for complete mixing,  except within 2 feet of the surface.  The aeration


 rate was 120 cfm, depth  of the basin 11 feet and with approximately 4


 horsepower input.  Velocities  were measured again at a later date with


 300 cfm being delivered  and 9  horsepower input with generally the same

-------
 results  except  the  surface velocities were higher.  The velocities
•found were  not  considered low; enough to cause the extremely poor basin
 performance.

 The  possibility of  excessive  turbulence being carried into the tubes
 was  also considered because of  the close proximity of the settler
 modules  to  the  aerators  (2-3  feet).  To check the possibility, a new
 aerator  was fashioned of a short length of 3-inch pipe attached to
 flexible hose and placed in the basin approximately 10 feet from the
 settler  modules.  The MLSS of the basin increased to 1000 mg/1 during
 operation of this aerator which did indicate that basin turbulence or
 entrained air bubbles was effecting the settler operation.

 The  basin was then  taken out  of operation to permit modifications in
 preparation for the next winter's operation.  The modifications are
 illustrated in  Figures 9 and  10.  The system was placed in operation
 in December 1969.   It was recogniized that at a detention time of 24
 hours and with  low  winter operating temperatures, the hydraulic load
 on the  tube settlers would be too great.  An attempt was made to
 reduce  the  hydraulic load on  the system while maintained a BOD load
 equivalent  to a 24-hour  detention time system by supplementing the
 feed with primary sludge from the Eielson tratment plant.  Basin ve-
 locity  proved to be restricted  around and beneath the separator hoppers
 because  of  the  low  clearance  and resistence offered by the settler
 support. As a  result, a heavy  sludge deposit blocked the separator
 hoppers, accumlated in the tubes and passed into the effluent.

-------
During a cold period in January 1 97G,  the surface of the  basin  began
to freeze due to low heat energy being supplied.   The sludge  accu-
mulated in the ice, reducing the suspended solids level in  the  pond
from approximately 2500 mg/1 to less than 200 mg/1.   During this
period, the mean ambient temperatures  averaged -23°F, with  a  range of
-8 to -35°F.  Wind velocity ranged from 10 knots  to  calm  and  averaged
3 knots.

A block was cut from the ice and a sample taken of the unfrozen sludge
beneath the ice.  A cross section is shown in Figure 11.  The ice had
reached a thickness of 14 inches with  a sl.udge layer of 17  inches
beneath the sampling point.  The sludge was not moving under  the ice
and apparently had attached itself, building up a thicker and thicker
layer which eventually froze into the  ice layer.

The long sloping side walls associated with earthen  basins  present
two very important problems in activated sludge aeration  chamber ap-
plications.  The relatively high surface area to  volume ratio will
result in high heat energy losses from the system which may be  very
critical with low temperature influent.  Greater  heat losses  will
promote ice formation which will entrain MLSS from the system,  de-
stroying the effectiveness of the process.

The second problem is the difficulty in obtaining adequate  basin velo-
cities at lower depths without excessively high horsepower  for  mixing.

-------
Even at high aeration, rates, the minimum recommended  velocities  of
1.0 fps were generally not present in the pilot facility extended
aeration basin at Eielson Air Force Base.

Another effect observed during operation in  the second  winter was
that, with the aerators off center, a circular  flow was induced  in
the basin in the horizontal  plane around the aerators.   The flow
was similar to the Coriolis effect which may be observed when drain-
ing a bathtub, etc.,  and seemed to be promoted  by  the earthen basin
shape of a large surface area to bottom  area ratio.   This effect will
only become a problem in situations in which flow  directions in  the
basin are important as in the Eielson AFB pilot facility, where  the
circular flow pattern did have an effect in  hindering sludge removal
from bneath the hoppers.

The cross sectional  shape of a basin and the temperature to which it
is exposed will, in general, determine the type of liner which should
be provided.  Material  must be used which will  prevent  erosion and
scouring by velocities in the basin.  Side slopes  of  less than 1
vertical to 2 horizontal permit use of flexible liners, whereas,
vertical sides will  require bearing wall  construction of impermeable
concrete or wood crib design with an impermeable liner.

Experience with the PVC liner indicates  it is not  feasible for use
in permanent installations for cold temperature applications.  The
liner becomes very susceptible to damage at  low temperatures because

-------
of brittleness, and ice formation can cause extensive breaks in the
lining.  Aging and exposure to sunlight also increase its susceptibility
to damage.

Impermeable liners such as low temperature butyl  rubber membranes are
feasible for use in earthen basins when the danger of major freezing
does not exist.  Care must be taken to insure that the liner is resist-
ant to hydrocarbons which may be present in the sewage as softening or
dissolution may result.

Concrete provides a reliable material for cold temperature application.
However, construction is expensive in Alaska and  particularly so in
remote areas.  Examples of the successful application of cheaper methods
of concrete construction are the College Utilities oxidation ditch in
Fairbanks, Alaska, and the oxidation ditch at Glenwood, Minnesota (2).
Concrete block was used for the construction of vertical sides for the
College Utilities ditch.  Concrete silo staves were originally used
for the sloping sidewall construction of the Glenwood ditch but were
not sealed and soil behind the staves washed out.  The problem was
successfully alleviated by placing steel mesh and 4 inches of concrete
grout over the staves to provide a smoother waterproof lining.

-------
                             REFERENCES
 1.  Anonymous, "Effect of Water Temperature  on  Stream  Reaeration,"
     Thirty-First Progress Report,  Committee  on  Sanitary  Engineering
     Research, Journal  of the Sanitary Engineering  Division,  Proceed
     ings of the American Society of Civil  Engineers, 87,  No.  SA6
     TNovember, 1961).

 2.  Anonymous, "Report on Operation of Oxidation  Ditch Sewage Treat-
     ment Plant, Glenwood, Minnesota," Department  of Health,  Divison
     of Environmental  Health, Section of Water Pollution  Control
     (July 8, 1965).

 3.  Ayres, John C.,  "Temperature and Moisture Requirements,"  Low
     Temperature Microbiology Symposium Proceedings  (Camden),  Campbell
     Soup Company (1962).

 4.  Benedict, Arthur Howe, "Organic Loading  and Temperature  in Bio-
     Oxidation," Doctor of Philosophy Thesis, University  of Washington
     (1968).                              .

 5.  Black, S.A., "How to Evaluate  Aeration Devices," Water and Pollution
     .Control, 106,  No.  10 (October  1968).

 6.  Culp, Gordon,  "A Better Settling Basin," The  American City (January
     1969).

 7.  Downing, A.L.,  "Factors to be  Considered in the Design of Activated
     Sludge Plants,"  Advances in Water Quality Improvement, University  of
 •    Texas Press,  pp..190-202, (1968).

 8.  Eckenfelder, Wesley, Jr., "Theory of Biological Treatment of  Trade
     Wastes," Journal  Water Pollution Control Federation,  39,  No.  2
     (1967).

 9.  Eckenfedler, W.W.,  and O'Connor, D.J., Biological  Waste  Treatment,
     Pergamon Press,  Inc., 44-01 21st Street, Long  Island, New York
     (1961).

10.  Frey, Paul J.",  "Significance of Winter Dissolved Oxygen  in Alaska,"
     presented at the Alaska Water  Management Association  Annual Meeting
     (May 1969).

11.  FWPCA Methods  for Chemical Analysis of Water  and Wastes,  Federal
     Water Pollution  Control Administration,  Division of  Water Quality
     Research, Analytical Quality Control  Laboratory, Cincinnati,  Ohio
     (November 1969).  .

-------
12.   Gordon, Ronald C.,  Research  Microbiologist,  Alaska  Water  Laboratory,
     College, ^Alaska, Unpublished data (April  1970).

13.   Grube, Gareth A. and Murphy, R.  Sage,  "Oxidation  Ditch  Works  Well
     in Sub-Arctic Climate," Water and Sewage  Works, 116,  No.  7  (July
     1968).

14.   Gustaffson, Bengt and Westberg,  Nils,  "Experiment with  Treatment  of
     Sewage from the Town of Kiruna by the  Activated Sludge  Method,"
     Royal Institute of Technology, Stockholm, Sweden, Institute of
     Water Supply and Sewage Technology,  Institute  of  Water  Chemistry,
     65., No. 4 (1965).

15.   Halvorson, H.O., Wolf, J.,  and Srinivasan, V.L.,  "Initiation  of
     Growth at Low Temperatures," Low Temperature Microbiology Symposium
     Proceedings (Camden), Campbell  Soup  Co.   (1962).

16.   Hansen, Sigurd P.  and Gulp,  Gordon L.,  "Applying  Shallow  Depth
     Sedimentation Theory," Journal  American Water  Works Association,
     59., No. 9 (September 1967~T

17.   Hansen, Sigurd P.,  Gulp, Gordon  L.,  and Stukenberg, John  R.,
     "Practical Application of Idealized  Sedimentation Theory,"  Pre-
     sented at the 1967  Water Pollution Control Federation Conference,
     New York City (October 10,  1967).

18.   Heukelekian, H. and Wiesburg, D., "Bound  Water and  Activated  Sludge
     Bulking," Sewage and Industrial  Wastes, 28.  No. 4,  p. 558 (April
     1965).

19.   Hunter, T.V. , Genetelli, E.J., and Gilwood,  M.E., "Temperature and
     Retention Time Relationships in  the  Activated  Sludge  Process,"
     Proceedings of 21st Industrial  Waste Conference,  Purdue University
     (1966).

20.   Johnson, Philip R.," and Hartman, Charles  W., "Environmental Atlas of
     Alaska," Institute  of Arctic Environmental Engineering, Institute of
     Water Resources, University  of Alaska,  College, Alaska  (1969).

21.   Ludzack, F.J., "Observations on  Bench  Scale  Extended  Aeration Sewage
     Treatment," Journal  Water Pollution  Control  Federation, 37, No. 8
     (August, 1965J;

22.   McKinney, Ross E.  and Gram,  Andrew,  "Protozoa  and Activated Sludge,"
     Sewage and Industrial Wastes, 28, No.  10  (October 1956).

23.   Miller, Ann P., "The Biochemical  Basis  of Psychrophily  in Micro-
     organisms," Institute of Water Resources, University  of Alaska,
     College, Alaska  (1967).

-------
24.  Pasveer, A., "Research on Activated Sludge, V:  Rate of Biochemical
     Oxidation," Sewage and Industrial  Wastes, 27, No.  7 (July 1955).

25.  Pohl, E.F., "The Effect of Low Temperatures on Aerobic Haste Treat-
     ment Processes," M.S. Thesis, University of Washington, Seattle,
     Washington (1967).

26.  Pohl, E.F., Chief, Sanitary Engineering Section, District Engineers
     Office, U.S. Army Corps of Engineers, Anchorage, Alaska, Personal
     Communications (April 22, 1970).

27.  Reed, Sherwood C., and Murphy, R.  Sage, "Low Temperature Activated
     Sludge Settling," Journal of the  Sanitary Engineering Division,
     Proceedings of American Socity of Civil Engineers, 95, No.  SA4
     (August 1969).

28.  Roguski, Eugene, Biologist, Alaska Department of Fish & Game,
     Fairbanks, Alaska-, Personal Communications.

29.  Schlecta, Alfred F. and Hsiung, Kou-Ying, "High Rate Processes in
     Advanced Waste Water Treatment,"  Presented at the 1969 Water Control
     Association of Pennsylvania (1969).

30.  Schmidtke, N.W., "Low Temperature Oxidation Ditch Field Study,"
     Thesis submitted to Department of Civil Engineering, University of
     Alberta, Edmonton, Alberta, Canada (April 1967).

31.  Standard Methods for the Examination of Water and Wastewater, 12th
     Edition, American Public Health Association, New York (1965).

32.  Stewart, Marvin J., "Activated Sludge Process Variations--The
     Complete Spectrum," Water and Sewage Works, pp. R2-41 - R2-62
     (December 1964).

33.  Thomas, Harold Allen, Jr. ,.•;•"Report" of Investigation of Sewage
     Treatment in Low Temperature Areas," for the Sub-Committee  on
     Waste Disposal, Committee on Sanitary Engineering and Environment,
     National Research Council (May 22, 1950).

34.  Wuhrmann, K., "Factors Affecting  Efficiency and Solids Production
     in the Activated Sludge Process,"  Biological Treatment of Sewage
     and Industrial Wastes, B.J. McCabe and W.W. Eckenfelder (ed),
     Reinhold Publishing Company, New  York, New York '(1956).

35.  Zanoi, A.E., "Secondary Effluent  Deoxygenation at Different Temp-
     eratures," Journal Water Pollution Control Federation, 41,  No. 4
     (April 19697!

-------
                               TABLE 1
                            DATA SUMMARY
                         1.3°C Cone Reactor
                   Feed:  Primary Plant Effluent
Detention
   Time (hrs)

Influent
   BOD (mg/1)

Reactor
   Susp. Solids (mg/1)
   Volatile
   Susp. Solids (mg/1)

Filtered Effluent
   BOD (mg/1)
   % BOD Removal

Unfiltered Effluent
   Susp. Solids (mg/1)
   BOD (mg/1)
   % BOD Removal

Loading Factor
   # BOD Feed
   #MLVSS-Day

Product of
   MLVSS and Det. Time
21
111
1,074
890
37
66
29
40
64
15
170
1,561
1,324
11
93
43
62
64
13
201
2,657
2,212
20
90
38
28
86
9
184
2,926
2,402
14
92
82
44
76
   .19
14,700
   .21
.17
19,500     28,000
.20
        21,600

-------
                               TABLE  2
                            DATA SUMMARY
                         6.5°C  Cone  Reactor
                    Feed:   Primary Plant  Effluent
Detention
   Time (hrs)                 17          15          13          9

Influent
   BOD (mg/1)                139         132         153        155

Reactor
   Susp. Solids (mg/1)     2,346       1,885       1,880       2,285
   Volatile
   Susp. Solids (mg/1)     1,915       1,563       1,587  .     1,801

Filtered Effluent
   BOD (mg/1)               51.3        16.3        13.3        11.7
   % BOD Removal              63          88          91          92

Unfiltered Effluent
   Susp. Solids (mg/i)        11          69          96          45
   BOD (mg/1)                 53          36          31          33
   % BOD Removal              62          73          80          79

Loading Factor
   # BOD Feed                .08        .106         .18        .23
   #MLVSS-Day

Product of
   MLVSS and Det. Time    31,600   .   23,000      23,300      20,600

-------
                                               TABLE 3

                                            CONE REACTORS
                                     RESULTS OF NUTRIENT ANALYSIS
                                        13 Hour Detention Time

Nhh-N (Ammonia)
N02-N (Nitrite)
NOs-N (Nitrate)
Kjeldahl-N (Nitrogen)
Total (Nitrogen)
Total Nitrogen
Removals (%)
0-P04 (Otho-Phosphate)
1.3°C REACTOR.
Influent
22
.13
.13
41
41.26

--
20
Fi 1 tered
Effluent
19
.09
2.13
28
30.22

27
18
Unfil tered
Effluent
18
.05
2.02
29
31.07

25
18
6.5°C REACTOR
Influent
19
.11
.21
37
37.32

--
19
Fi 1 tered
Effluent
1
.13
9.17
3
12.30

67
18
Unfil tered
Effluent
1
.15
12.13
3
15.28

59
18
                                         9 Hour Detention Time

NH3-N (Ammonia)
N02-N (Nitrite)
N03-N (Nitrate)
Kjeldahl-N (Nitrogen)
lotal (Nitrogen)
Total Nitrogen
Removals (%)
0-P04 (Otho-Phosphate)

Influent
21
.06
.11
36
36.17

—
17
.3°C REACTOR
Fi 1 tered
Effluent
19
.03
.68
26
26.71

26
14
Unfil tered
Effluent
19
.03
.54
27
27.57

24
15
6.
Influent
21
.06
.07
35
JD. IJ

•--
19
5°C REACTOR
Filtered
Effluent
1
.14
8.03
3
11.17

68
18
Unfil tered
Effluent
1
.12
14.45
3
17.57

50
16
(1) Total  nitrogen results reported are the
    nitrogen analysis
sum of the nitrite, nitrate and Kjeldahl

-------
                                TABLE 4

              SUMMARY OF RESULTS OF 8.9 GALLON REACTOR AND
                12.45 GALLON REACTOR AT 12-HR DETENTION

                    Feed:  Primary Plant Effluent
Reactor MLSS (mg/1)
     % VSS
     BOD
     COD

.    ,.     Ib Infl.  BOD
Loadin9:  Ib MLVSS-Day
c,  .   ,.  .   .
Sludge Wasted:
                mg/MLSS
BOD Removed
Unf i 1 tered
Effluent
     Suspended
     Solids (mg/1)
     BOD (mg/1)
     BOD Removal (%)
     COD (mg/1)
     COD Removal (%)

BOD/ COD Ratio
     Influent
     Effluent
     Reactor
REACTOR TEMPERATURE (AVG°C)
.6
4160
80
2489
5648
2.9
4097
80
2503
5788
3.8
4076
81
1477
5260
8.0
3737
80
1299
4705
 0.12
 0.42
18
21
89
78
76
 0.60
 0.24
 0.44
 0.10
                                                     0.33
 3
13
92
46
73
 0.60
 0.23
 0.43
 0.10
           0.32
12
17
90
67
78
 0.55
 0.25
 0.28
                                                     0.14
          0.33
                                                     5
                                                     9
                                                    96
                                                    96
                                                    83
                                                     0.66
                                                     0.16
                                                     0.28

-------
                                TABLE 5

              SUMMARY OF RESULTS OF 8.9 GALLON REACTOR
                         AT. 24-HR DETENTION

                    Feed:  Primary Plant Effluent
Reactor MLSS
     % vss
     BOD
     COD
             (mg/1)
Loading:
          1b Infl.  BOD
          Ib MLVSS-Day
Sludge Wasted:
    3
                        -
                mg BOD Removed
Unf i 1 tered
Effluent
     Suspended
     Solids (mg/1)
     BOD (mg/1)
     BOD Removal (%)
     COD (mg/1)
     COD Removal (%)

BOD/COD Ratio
     Influent
     Effluent
     Reactor
REACTOR
'1.9
2595
83
1693
3712
TEMPERATURE
6.8
3872
83
2105
5019
(AVG°C)
10.5
3896
82
1808
5178
                                       0.07
                                       0.42
                                       3
                                      14
                                      93
                                      51
                                      83
                                       0.66
                                       0.27
                                       0.46
 0.07
 0.16
 4
10
95
53
84
 0.66
 0.19
 0.42
 0.07
 0.14
 6
10
95
69
80
 0.62
 0.13
 0.35

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                                                 TABLE 6

                                            8.9 GALLON REACTOR
                                RESULTS OF OPERATION  WITH VARYING EFFLUENT
                                   OVERFLOW RATES ON  THE  SETTLING TUBES

Reactor^
Temp
(°C)
.35
(.3-. 5)
.7
(.4-. 9)

4.2
(2.8-6.4)

3.8
(3.5-4.1)

INFLUENT
Susp.
Solids
(mg/1)
95

112


94


77


BOD
(mg/1)
244

253


193


142


COD
(mg/1)
292

370


229


283


REACTOR
Susp. SVI
Solids
(mg/1)
3973 238

4237 238


4147 ™


4067 229


EFFLUENT
Overflow
Rate
(gpm/ft2)
.4

.3

.6
.3

.6
.5

.8
Susp.
Solids
(mg/1)
10

8

20
10

• 14
10

13
BOD
(mg/1)
12

22

29
17

20
14

20
% BOD
Removal
95

91

89
91

90
90

86
COD
(mg/1)
69

71

87
60

70
62

69
• % COD
Removal
76

79

77
74

69
78

76
(1)  Values in parenthesis are minimum and maximum for that period

-------
                                TABLE 7

                          12.45 GALLON REACTOR
           RESULTS OF OPERATION WITH  VARYING EFFLUENT OVERFLOW
                       RATES ON THE SETTLING TUBES

Reactor
Temp
(°c)
2.4
(1.4-3.5)

2.9

, ? '
4.4
(4.0-4.7)

7.8
(6.8-8.4)

INFLUENT
Susp.
Solids
(mg/1)
77


86


93


87


BOD
(mg/1)
177


185


223


194


COD
(mg/1)
303


275


321


313


REACTOR
Susp. SVI
Solids
3957 —

-
4157 214


4095 235


4504 209


EFFLUENT
Overflow^
Rate
(gpm/ft2)
.2
(continuous)

.3
(on 1/2 hr
off 1/2 hr)
.5
(on 1/2 hr
off 1/2 hr)
.5
(on 2 hr
off 1 hr)
Tube
Size
2 x 3.5

4 x 3.5
2 x 3.5

4 x 3.5
2 x 3.5

4 x 3.5
2 x 3.5

4 x 3.5
Susp.
Solids
(mg/1 )
2

2
4

3
4

5
12

14
BOD
(mg/1)
19

19
12

10
12

12
20

23
% BOD
Removed
89

89
94

95
95

95
90

88
COD
(mg/1)
35

39
50

52
55

69
69

64
% COD
Removed
88

87
82

81
83

79
78

80
(1)  Values in parenthesis  are  minimum  and  maximum  for  that  period
(2)  Notes in parenthesis indicate  the  time cycle of  effluent  flow  through  the  tubes

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   Mixer
                  Holter Perfusion
                    Roller Feed
                          Pump
Reactor
                                                             Effluent
                                                             Holding
                                                               Tank
                                                         Concentric Cones
                            Moisture
                            Trap
                                        FIGURE  1

                                    CONE  REACTORS*
                                SCHEMATIC OF APPARATUS
•*J\s manufactured by Pope Scientific

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Mixing
Pump
                                             f
                                     To Aeration Chamber

Refriger-
ation
Unit

j


i
j
Feect
Tank^
                              Settling
                                Tubes
                                   Holter :
                                   Perfusic
                                   Roller
                                   Feed
                      k60 Gal
                                   Pump
Air Supply
                           n
                                                 Effluent
                                                  Pump
                                                 (HoUer),
                              Moisture
                                Trap
                          Reactor
                          Plexiglas
                                                          Effluent
                                                          Recycle
                                                            Pump
                                                          (Holter)
                                                    Effluent
                                                    Overflow
                                                    Line
                                                                         Reactor
                                                                        Side View
                                                          Effluent
                                                           Tanks
                                              FIGURE 2

                                            AWL REACTOR
                                             8.9 GALLON
                                       SCHEMATIC OF APPARATUS

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                                                                                       1-hr timer
                                                                                   	D
                                                                                   lenoid Valves
                                                                                       24-hr
                                                                                       Timer
Refrigera-
tion Unit
                                                                             Recycle
                                                                            * Pump (Holter)
Feed Pump (Holter
                              Moisture
                                Trap
                                                                                   Effluent Tank
                                                                                      2" Tubes
                                              FIGURE 3

                                            AWL REACTOR
                                            12.45 GALLON
                                       SCHEMATIC OF APPARATUS

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      Beginning _
of clear effluent
     and sludge
     interface
                                                          Gear
                                                         Effluent
                                                      Particles
                                                     rising above
                                                   sludge blanket
                                                 Sludge circulation
                                                      pattern
                          FIGURE  4

      SLUDGE ACTION IN UPFLOW CLARIFIER  SETTLING TUBES

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    50..
    40 -.
 
-------
20._
l/l
3 15.
o
-a
0)
TD
QJ
Q-
3 10.
CO
OJ
3
4!
UJ
5 -




A
A
.0

A 0 A
o



v
B

Legend
Continuous Flow
O< 1°C
A^ 4°C
Intermittent Flow
on 1/2 hr
off 1/2 hr
Q% 3°C
V^ 4°C


Intermittent Flow
on 2 hr
off 1 hr
A^C
MLSS ^ 4000 mg/1 ,
III! f . 1 i
III! ' 1 I 1
.1 .2 .3 .4 .5 .6 .7 .8
             Overflow Rates (gpm/ft2)
                      FIGURE 6

        8.9 GALLON AND 12.45 GALLON REACTORS
            EFFLUENT SUSPENDED SOLIDS vs
       OVERFLOW RATES AT VARIOUS TEMPERATURES

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xA
 \
.70"-
                          Aerators
                           Plan View
                                          Tube Settler
                                            Modules
                                               \
                                                          70'
                                                         \
                                   A
                       Maximum Working Liquid Depth
                         View A-A
                       FIGURE 7

            EXTENDED AERATION PILOT FACILITY
                   EIELSON A.F.B. .
                  1968  Configuration

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4'
                          Settling
                           Tubes
                                            Effluent
                                            Header
                                      !o O
                                             O O O O O O
"l I !  I i~[lTiTiTr
 • 11  n  ['!!!!•!
         1,  I 11  ' I
         I'  I 11  I ,
                                        I
i. M .  iit
Ll_l_LLLJ_lLJ_LLL
         5'
                     FIGURE  8

                TUBE SETTLER MODULE

                1968 Configuration

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                          Chicago Pump
                          Shearfusers
                                          Monosparj
                                          Diffuser
                                            Header
                                    } Tube Settler
                                      Modules
                      Plan View
                       Elevation
                     FIGURE 9

EXTENDED AERATION PILOT FACILITY AFTER MODIFICATION
                  EIELSON A.F.B.
                1969 Configuration

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\\
                            FIGURE 10
                    TUBE SETTLER MODULE DESIGN
                  .WITH FLOW BENEATH THE HOPPER

                        1969 Configuration

-------