QUHDE DGinFECTl OF  TREfllED UJBSIE11ER
   in BBFFLEO COHTBCT
Bl <1C
  U. S. ENVIRONMENTAL PROTECTION  AGENCY
ARCTIC ENVIRONMENTAL RESEARCH LABORATORY
          COLLEGE, ALASKA 99701

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CHLORINE DISINFECTION OF TREATED WASTEWATER

    IN A BAFFLED CONTACT CHAMBER AT <1C
              Ronald C. Gordon
           Charlotte V. Davenport
               Barry H. Reid
            Working Paper No.  21
    U.S.  ENVIRONMENTAL PROTECTION AGENCY
  ARCTIC ENVIRONMENTAL RESEARCH LABORATORY
              COLLEGE, ALASKA
          Associate Laboratory of
 National  Environmental Research Laboratory
             Corvallis, Oregon
     Office of Research and Development
                October 1973

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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.  Mention of commercial products or
services does not constitute endorsement.

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                             Abstract
     This study was designed to examine the disinfection process at low
temperatures because effluent in the Arctic and Subarctic can be expected
to be in the 0 to 10C range during a significant portion of each year.
Disinfection was considered effective if the effluent contained no more
than 1000 total and 200 fecal coliforms/100 ml.  Total chlorine residual
was monitored with the orthotolidine and iodometric methods, and the memr
brane filter method was used for all bacteria enumeration.
     During the first phase of the study, batch treatment was used to ex-
amine three secondary and one primary effluent.  The results indicated
that effective disinfection was attained in samples from all sources at
<1C when the actual contact time was 60 minutes and the final chlorine
residual was approximately 1 mg/1 (orthotolidine).
     The second phase of the study was conducted in an 8-compartment,
over-under baffled, 60-liter contact chamber at <1C and 10C.  Flow
rates providing 30, 60 and 120 minutes theoretical contact time were used.
Dye studies at each flow rate indicated that extensive short-circuiting
occurred, and that the 120 minute contact time flow rate was the only
one which provided 60 or more minutes residence time for the majority of
the effluent.
     Regardless of the flow rate or chlorine residual maintained, the
fecal coliforms were essentially destroyed (<5/100 ml) at <1C.  However,
reduction of the total coliforms to <1000/100 ml did not occur when
the theoretical contact time was 30 minutes, even when the chlorine
residual was 3.3 mg/1 (orthotolidine).  At 60 minutes theoretical con-
tact time, nearly 2 mg/1 chlorine residual (orthotolidine) were required

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                                                                    11
before the total  coliforms were sufficiently reduced.   Only slightly
more than 0.5 mg/1 chlorine residual  (orthotolidine) was required for
the total coliforms at the 120 minutes theoretical contact time flow
rate.  The fecal  streptococci  numbers were generally reduced to a level
between those found for the total  and fecal  col iforms.
     Theoretical  contact times of 30  and 60 minutes were used at the 10
operating temperature.  The results suggested that raising the tempera-
ture from <1C to 10C caused little  or no change in the effectiveness
of disinfection.

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                                                                     m
                            TABLE OF CONTENTS
                                                                     PAGE
INTRODUCTION    '                                                       1



MATERIALS AND METHODS                                                  5



EXPERIMENTAL RESULTS                                                  11



DISCUSSION                                                            41



CONCLUSIONS                                                           52



REFERENCES                                                            54

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                                                                       IV



                            LIST OF FIGURES


NUMBER                                                               PAGE

   1        Flow through system used in the disinfection studies.       6

   2        Instantaneous and continuous dye injection in flow
           through contact'chamber studies.  (60 minutes
           theoretical  contact time)                                    13

   3        Average number of bacteria surviving disinfection at
           <1C with corresponding total  chlorine residual average
           and range.   [60 minutes theoretical  contact time, 1 mg/1
           chlorine residual (OT)]                                     16

   4        Average number of bacteria surviving disinfection at
           <1C with corresponding total  chlorine residual
           average and  range.   [60 minutes theoretical contact
           time, 2 mg/1 chlorine residual  (OT)]                        19

   5        Instantaneous and continuous dye injection in flow
           through contact chamber studies.  (30 minutes
           theoretical  contact time)                                    21

   6        Average number of bacteria surviving disinfection at
           <1C with corresponding total  chlorine residual average
           and range.   [30 minute theoretical  contact time, 2.5
           mg/1 chlorine residual (OT)]                                25

   7        Instantaneous and continuous dye injection in flow
           through contact chamber studies.  (120 minutes
           theoretical  contact time)                                    27

   8        Number of bacteria surviving disinfection at <1C
           with corresponding total chlorine residuals.  [120
           minutes theoretical contact time, 1  mg/1  chlorine
           residual (OT)]                                              30

   9        Number of bacteria surviving disinfection at <1C
           with corresponding total chlorine residuals.  [120
           minutes theoretical contact time, 1  mg/1  chlorine
           residual (OT)]                                              31

  10        Number of bacteria surviving disinfection at 10C
           with corresponding total chlorine residuals.  [60
           minutes theoretical contact time, 1  mg/1  chlorine
           residual (OT)]                                              37

  11        Number of bacteria surviving disinfection at 10C
           with corresponding total chlorine residual.  [30
           minutes theoretical contact time, 2  mg/1  chlorine
           residual (OT)]                                              38

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                             LIST OF TABLES


NUMBER                                                               PAGE
           Effluent Sample Parameters from Flow Through
           Contact Chamber Studies at <1C.  [60 minutes
           theoretical contact time, 1 mg/1 total chlorine
           residual (OT)]                                             15

           Effluent Sample Parameters from Flow Through
           Contact Chamber Studies at <1C.  [60 minutes
           theoretical contact time, 2 mg/1 total chlorine
           residual (OT)]                                             18

           Effluent Sample Parameters from Flow Through
           Contact Chamber Studies at <1C.  [30 minutes
           theoretical contact time, 2.5 mg/1  total
           chlorine residual (OT)]                                    23

           Effluent Sample Parameters from Flow Through
           Contact Chamber Studies at <1C.  [120 minutes
           theoretical contact time, 1 mg/1 total chlorine
           residual (OT)]                                             29

           Effluent Parameters of Samples Subjected to 60
           Minutes Batch Disinfection at <1C in Parallel with
           the Flow Through System.                                    34

           Effluent Parameters Common to Samples Examined at
           10C.                                                       35

           Effluent Parameters of the 10C Flow Through System
           and Parallel  60 Minute Batch Disinfection at 10C
           and <1C.                                                   40

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                          Introduction
     The use of chlorine as a disinfectant in water and treated wastewater
has come under rather intensive study, beginning with the early work of
Heathman ejt. al. (17) and Rudolfs and Gehm (27) in 1936, and the current
"State of the Art" has been well  documented in several  recent publications
(2, 5, 26, 35).  With the exception of the early study of sewage disinfec-
tion by Rudolfs and Gehm (27), nearly all  the literature indicates that
the disinfecting ability of chlorine is severely hindered by low tempera-
tures (5, 6).  However, most of these studies used pure culture-pure
water systems to establish the disinfecting characteristics of chlorine
without the inherent interferences found in treated wastewater (5).  In
1967, Marais et. al_. (24) pointed out the need for reliable laboratory
studies to establish the disinfecting ability of chlorine in the presence
of the inherent interferences found in treated wastewater.  Subsequently,
some effort has been made in this direction (8, 21, 22), but these studies
have not considered the effect of low temperature on the disinfection pro-
cess.
     Over a large portion of the world, water temperatures in waste treat-
ment systems and in effluents from these systems may approach 0C during
several months each year, and disinfection may be difficult to achieve in
these cold effluents.  Throughout the cold months, the receiving waters
into which the effluents are discharged will also have temperatures near
0C.  These very low receiving water temperatures accentuate any problems
caused by ineffective chlorine disinfection because cold effluents may

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contain more enteric bacteria  than warm effluents  (9,  29),  and  fecal  in-
dicator bacteria survive for  longer  periods  in  0C receiving  water (15)
than in warmer receiving water (3).   Preliminary evidence also  indicates
that salmonellae have increased survival  at  0C (34).  Therefore,  an  ef-
fective effluent disinfection  process  is  of  great  importance  in cold  cli-
mates where low temperatures may make  disinfection difficult  to achieve.
However, the process has received  little  or  no  special consideration  in
actual cold climate waste treatment  practice.
     Minimum effective treated wastewater disinfection,  as  used throughout
this presentation, is based on the disinfection criteria established  by
the U. S. Environmental  Protection Agency, Region  X  (11).   These criteria
are:  [1]  that effluents from chlorine contact chambers shall  average
less than 1000 total coliforms and 200 fecal coliforms/100  ml when the ef-
fluent is discharged into recreational waters and  [2]  that the total chlo-
rine residual shall not be less than 1 mg/1  after  60 minutes  of contact
time when conclusive coliform  data are not available.
     In order to determine whether or  not effective  treated wastewater dis-
infection could be achieved at less  than  1C (<1C), a two-phase study was
conducted at the Arctic Environmental  Research  Laboratory.  During the
first phase, batch treatment with  rapid initial chlorine mixing and con-
tinuous stirring was used to study effluents from  four waste  treatment sys-
tems at <1C with controls run in  parallel at 25C (16).  These effluents
were from a primary sedimentation  system, a  15  day detention  time aerated
lagoon and two extended aeration systems. The  results indicated that both

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chlorine demand and the rate or extent of coliform reduction were de-
creased at <1C where compared to the 25C results.  Effective disinfec-
tion was attained in effluents from all sources at <1C within the 60
minutes contact time in the presence of no more than 1  mg/1  final total
chlorine residual (orthotolidine method).  The ease with which effective
disinfection was attained varied significantly among the four effluents
at <1C, but there was essentially no difference in the 25C controls.
The primary sedimentation system produced a more uniform effluent which
was consistently easier to disinfect than the secondary effluents.  How-
ever, it did require a slightly greater initial chlorine dose to provide
a final 1 mg/1  chlorine residual.
     When disinfection is conducted using a batch system, theoretical
and actual contact time are the same.  This is analogous to  plug flow in
a flow through system.  It has been pointed out in several  recent publica-
tions (7, 8, 20, 21, 23, 28, 30, 35) that plug flow provides the most
nearly ideal situation for disinfection because all liquid entering the
contact chamber is retained in tne chamber for the theoretical contact
time.  In actual practice, short-circuiting in the contact chamber pre-
cludes the attainment of residence time approaching theoretical contact
time.  Thus, theoretical contact time has little meaning, rendering in-
correct the assumption that batch disinfection results can be extrapolated
to flow through contact chambers (7).
     As was previously discussed, the first phase of this study showed
that effective disinfection could be attained with batch treatment at <1C

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with no more than 60 minutes  contact  time  in  the presence of  1 mg/1  or
less final total  chlorine residual  (orthotolidine method).  Since  higher
bacterial quality can be expected  in  the effluent after batch disinfec-
tion than in flow through contact  chambers, a second phase of this study
was conducted at <1C using a well  baffled flow through chlorine contact
chamber.  The objective of this  study was  to  determine if minimum  effec-
tive disinfection could be achieved in a contact chamber built according
to the design guidelines established  by the U. S. Environmental Protec-
tion Agency, Region X (11).   Briefly, these design guidelines state that:
[1]  the chlorine contact chamber  must be  sized to provide 60 minutes con-
tact time at design flow with 20 minutes contact time at peak hourly flow
or maximum pumping rate, which ever is greater; [2]  the contact chamber
must be designed  to minimize  short-circuiting; and [3]  chlorine must be
thoroughly mixed  with the treated  wastewater  to achieve maximum disinfec-
tion efficiency.

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                      Materials and Methods
Effluent Source and Sampling
     The primary sedimentation system effluent examined during the first
phase of this study (16) was from the 2.5 million gallon/day Fairbanks,
Alaska city plant.   This effluent was selected for further study because
it had uniform physical  and chemical  characteristics, and because it was
relatively easy to disinfect in batch treatment.   The day prior to each
experiment of the second phase, approximately 150 gallons of effluent
were collected in 15 gallon polyethylene barrels  and transported immedi-
ately to the laboratory.
Effluent Preparation After Arrival in the Laboratory
     The barrels of effluent were placed in a controlled temperature room
where the ambient air temperature was maintained  at or slightly below the
experiment temperature.   The effluent temperature was determined, then
cooled to 0.3-0.5C, or adjusted to 10C, in three 50 gallon batches using
the 55 gallon barrel and cooling apparatus shown  in Figure 1.  These
batches were stirred continuously until  the next  day.
Flow Through and Batch System Description
     Figure 1 is a schematic diagram of the flow  through system showing
the pattern of effluent and chlorine feed, and movement of the liquid
through the contact chamber.  The various flow rates were obtained using
Holter model ER 161 variable speed pumps equipped with different size tub-
ing.  All liquid, was moved in Tygon or latex rubber tubing.  It was neces-
sary to continuously stir the effluent in the feed barrel and the constant

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  REFRIGERATED
  WATER BATH;
VTH^
3 LITER CONSTANT
LEVEL CHAMBER
VAR. SPEED   100 Ml. CONSTANT  VAR. SPEED
   PUMP -7-LEVEL CHAMBER 7     PUMP
              OVERFLOW
       D
  MAGNETIC
   STIRRER

^
^
4.
^
^
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) r 
?
^
^
^
r
s
**
P
CO
 rn

               PROPELLER
               STIRRER
   \
 L
      55 GAL. FEED BARREL
                                                      CHLORINE
                                                      STOCK
                                                      SOLUTION
                                                    18 GA. NEEDLE
                                      BAFFLES
                                                    CHLORINE CONTACT CHAMBER
                                                                                   TO
                                                                                   WASTE
Figure 1.   Flow through system used in  the disinfection studies.
                                                                                               cr>

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level chamber to maintain solids in suspension.
     The contact chamber was an eight compartment over-under baffled  unit,
having a 60 liter capacity.   Effluent passed the under baffles  through  a
0.8 cm slot the full  width of the chamber,  and passed the over  baffles  at
a depth of 0.8 cm.  The first seven compartments were the same  size,  38.1
cm wide by 16.2 cm deep by 10.2 cm long.  The last compartment  was  21.3
cm long.
     Flow rates through the contact chamber were 0.5, 1.0 and 2.0 liters
per minute providing theoretical contact  times of 120, 60 and 30 minutes,
respectively.  The pump speed was adjusted  so that it took 60  1 second
to fill an appropriate size class A volumetric flask with liquid as it
was discharged from the chamber.  The flow  rate was monitored frequently
throughout each run and adjustments in pump speed were made as  necessary
to maintain the desired flow rate.
     Chlorine stock solution was pumped from the reservoir into the con-
stant level chamber, a modified 100 ml polypropylene graduated  cylinder
with the top closed to minimize volatilization of chlorine.  The flow
rate was adjusted so that there was a continuous overflow to waste  from
the constant level chamber rather than returning the overflow to the
stock solution reservoir.  The constant level chamber was mounted above
the contact chamber so that the hydrostatic head would easily permit
gravity flow of chlorine through a rotameter used to control and monitor
the volume of chlorine being injected into  the effluent feed line.
     The batch system run in parallel with  the flow through system  was

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                                                                        8
set up as described previously (16).  A 60 minute contact  time  was  used
regardless of the flow rate  used in the contact chamber.
     All studies were conducted in a controlled temperature  room with the
temperature adjusted to maintain the effluent at <1C or 10C in the con-
tact chamber.
Glassware and Glass Distilled  Mater Preparation
                                       x
     All glassware used during this study was made chlorine  demand  free
(1) and glass distilled water  was prepared as described previously  (16).
Both the glassware and the glass distilled water were allowed to equili-
brate at the temperature to  be used for the  particular disinfection ex-
periment.
Chi orination Methodology
     A chlorine stock solution volume sufficient for all needs  was  prepared
by dilution of household bleach (Purex brand) with glass distilled  water
immediately prior to each experiment.  The stock solution  was made  up to
500, 1000 or 2000 mg/1 chlorine depending on the effluent  flow  rate through
the contact chamber and the  chlorine residual desired.  Varying the chlo-
rine concentration permitted the stock solution flow rate  to be maintained
at no more than 13 ml/minute,  minimizing any dilution effect in the efflu-
ent.
     Immediately prior to the  start of each  disinfection experiment, the
initial chlorine demand and  the 60 minutes contact time chlorine demand
were determined in the effluent, as previously described (16).
     Total chlorine residual was determined  by both the orthotolidine (OT)

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and iodometric methods as described in Standard Methods (1).  At the start
of each experiment, chlorine residual  determinations were made with both
methods in the unchlorinated effluent.  The OT method was then used to
monitor the residual at predetermined  time intervals until a fairly con-
stant concentration was reached.  Both methods were then employed through-
out the remainder of each experiment.
Bacteria Enumeration
     Total coliforms, fecal coliforms  and fecal streptococci were enumer-
ated with the membrane filter method (13).  The media were M-Coliform
Broth (BBL), M-FC Broth (BBL) and KF-Streptococcal Agar (BBL and Difco),
respectively.  Each time the M-FC Broth was prepared, the pH was measured
and adjusted to 7.4 if necessary.
     Effluent samples for bacteria enumberation were collected in sterile,
220 ml, polypropylene containers (Falcon Plastics) which contained 0.5 ml
of 10 percent sodium thiosulfate solution.
     The potential problems and their  possible effect on coliform enumer-
ation with the membrane filter method  in chlorinated effluents were dis-
cussed previously (16).
Physical and Chemical Parameter Measurement
     Chemical oxygen demand (COD), total solids (TS), total suspended
solids (TSS), volatile suspended solids (VSS), total dissolved solids
(TDS), volatile dissolved solids (VDS) and total volatile solids (TVS)
were determined by the methods described in Standard Methods (1).  Am-
monia nitrogen (NH3-N) and total nitrogen (kjeldahl) were determined ac-

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                                                                       10
cording to Techinicon AutoAnalyzer Methodology  (31, 32).  Nitrite  (N02-N)
and nitrate (N03-N)  were determined according to U. S.  Environmental  Pro-
tection Agency methods (10).   A Leeds  &  Northrup pH meter (model 7401),
equipped with a Leeds & Northrup automatic  temperature  compensator and a
Beckman Combination  Probe (GP Glass),  was used  for pH determinations.
Dye Studies in the Chlorine Contact Chamber
     For these experiments, tap water  cooled to <1C was pumped  into  the
contact chamber at rates of 0.5, 1.0 or  2.0 liters/minute.   The  Rhodamine
B dye was injected in the same manner  and location as the chlorine in the
disinfection studies (Figure  1). Dye  concentration was measured using a
G. K. Turner Associates model  111 Fluormeter equipped with  a flow  through
door, and recorded on a Beckman model  1005  recorder.
     To determine residence time of particles entering  the  chamber, a vol-
ume of dye was rapidly injected and its  passage through the system fol-
lowed.  To establish operating time required for constant concentration,
dye was injected continuously for several hours.  The volume or  rate  of
dye injection and the instrument sensitivity were adjusted  so that maxi-
mum readings of 60-90 percent of full  scale were obtained on the recorder.

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                                                                       n
                      Experimental Results
     The results presented here were derived from 16 flow through contact
chamber experiments.  Of these, 14 were conducted at <1C and two at 10C
using four total chlorine residual:theoretical contact time relationships.
As a parallel control with each flow througn experiment, effluent was
treated in batch using 60 minutes contact time with a 1 mg/1  final total
chlorine residual.
     The study was conducted from November 15, 1972 to April  15, 1973,
during which time the city waste treatment system operating temperature
was 8-10C.  Because a large sample volume was collected for each experi-
ment, it was necessary to transport the effluent in an open truck.  As a
result, the effluent temperature was generally lowered by the ambient air
temperature during the trip.  Effluent temperature measured immediately
after arrival in the laboratory ranged from 0.6C to 9.2C.  Temperature
variations were random throughout the time the study was conducted and
there did not appear to be any correlation with the disinfecting charac-
teristics of a particular sample.  The only apparent effect resulting
from this temperature variation was the length of time required to cool
the effluent to 0.3-0.5C.
     The range of values obtained for effluent parameters was generally
random throughout the entire study.  However, some variation could be ex-
pected during the five month period that samples were taken.   The chlo-
rine concentration added initially varied with the chlorine demand of
each sample and the desired residual in the contact chamber during each

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                                                                       12
series of experiments.
Dye Studies at 60 Minutes  Theoretical  Contact Time
     Figure 2 shows  typical  results of instantaneous and continuous dye
injection at the 60  minute theoretical  contact  time flow rate.   After in-
stantaneous injection,  dye was first detected in  the effluent from the
contact chamber in 14 minutes.  Other  results showed first  dye  appearance
in 12 to 15 minutes  at  the same flow rate.   The dye concentration then
increased rapidly and the  peak was reached  42 minutes  after injection.
The curve produced by dye  passage was  not symmetrical, and  it required
50 to 51 minutes for 50 percent of the dye  to pass.  Thirty-three percent
of the dye was still in the chamber after 60 minutes residence  time,
which was theoretical contact time at  this  flow rate.   Recently,
Kothandaraman et^ a_K (21)  discussed chlorine contact chamber performance
and pointed out that plug  flow was represented  by a Morril  index of 1.0.
The Morril index for this  chamber at the 60 minute theoretical  contact
time flow rate was 2.8  which indicated that plug  flow  was not even ap-
proached.
     When the dye was injected continuously, elapsed time for first dye
appearance was approximately the same  as the instantaneous  injection.
However, the concentration increased at a much  slower  rate  and  reached
maximum concentration after approximately 160 minutes  elapsed time.  The
dye concentration then  continued at a  nearly constant  level for the re-
mainder of the time  the chamber was operated.
Disinfection Studies a_t <1C Using (50  Minutes Theoretical Contact Time
1 mg/1 Total Chlorine Residual (OT)

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lOOr
                              INSTANTANEOUS DYE  INJECTION
                       	CONTINUOUS  DYE  INJECTION
        20
40
60
80
100
120     140     160     I6C
ELAPSED  TIME,  minutes
"20O~
220
240
260
280
300
  Figure  2.   Instantaneous and continuous  dye  injection in flow through contact  chamber studies.
                  60 minutes theoretical contact time.

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                                                                       14
     The five replicate experiments  in the 60 minute theoretical  contact
timerl  mg/1  total  chlorine  residual  (OT) series at  <1C were  conducted
over a  39 day period.   The  arithmetic mean, and maximum and minimum para-
meter values are shown in Table 1.   This value range is comparable  for
most values  obtained throughout the  study.
     Preliminary determinations indicated that total chlorine residual
in the contact chamber effluent reached its maximum concentration in
about the same elapsed time as observed for the dye.   Therefore,  moni-
toring of the effluent for  chlorine  residual and  viable bacteria  began
after the system had operated for  120 minutes.  As  shown  in Figure  3,
the average  total  chlorine  residual  (OT) became stable at 0.9-1.0 mg/1
after 150 minutes elapsed time, with a range of 0.57-1.5  mg/1 for the
five experiments in this series.   The average iodometric  residual reached
a concentration of 4.2 mg/1 in 120 minutes and continued  to increase un-
til it reached 4.5 mg/1 at  270 minutes.  The minimum and  maximum  concen-
trations determined by the  iodometric method during the series were 3.4
and 5.0 mg/1, respectively, and the  average was 3.4-3.6 mg/1  higher than
obtained with the OT method.
     The average number of  total coliforms, fecal coliforms and fecal
streptococci surviving disinfection  in the presence of these  total  chlorine
residuals are also shown in Figure 3.  The initial  total  coliform count in
the unchlorinated effluent  ranged  from 2.2-3.6 x  10/100  ml.   When  the  to-
tal chlorine residual  in the contact chamber effluent  reached its maximum
average concentration, the  lowest  average total coliform  count was  3.4  x
10 /100 ml.   The lowest total coliform count recorded  for any sample dur-

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                                                                       15
Parameter
Initial temperature, C
Final temperature, C
Initial pH
Final pH
Chlorine added as HOC1 , mg/1
TS, mg/1
TVS, mg/1
TSS, mg/1
VSS, mg/1
VDS, mg/1
TDS, mg/1
NH3-N, mg/1
N02-N, mg/1
N03-N, mg/1
Kjeldahl-N, mg/1
COD, mg/1
Arithmetic
mean
0.6
0.5
7.2
7.3
5.6
444
256
65
49
183
363
16.8
0.020
0.052
24.6
235
Maximum
value
0.7
0.8
7.4
7.4
6.9
490
380
81
59
280
400
20
0.04
0.07
30
289
Minimum
value
0.4
0.2
7.1
7.2
4.6
400
200
54
40
120
320
14
<0.01
0.04
20
183
Number
of
samples
5
5
5
5
5
5
5
5
5
4a
4a
5
43
5
5
5
a Results not  available for some samples.
Table 1.  Effluent Sample Parameters from Flow Through  Contact  Chamber
          Studies at <1C.
               60 Minutes Theoretical Contact Time,  1 mg/1
               Total Chlorine Residual  (OT).

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                                                                             16
  10
  10'
E   ;
O lO
  10
a:
UJ
H

< in3
OD 10
at
ii1 ,~2L
  10
O   TOTAL  COLIFORMS

A   FECAL  COLIFORMS

D   FECAL  STREPTOCOCCI
 . 6


1 =
V)
uj 4
IT

UJ 3
5
O  I
                                          O  IODOMETRIC RESIDUAL

                                          D  ORTHOTOLIDINE RESIDUAL
         3O   60   90   120   150  180   210   240   270  3OO
                               ELAPSED TIME,  minutes
                            33O   36O  39O  42O
   Figure  3.   Average number of bacteria surviving disinfection at  <1C
               with corresponding total  chlorine residual  average and  range.
                    60 minutes theoretical contact time,  1  mg/1
                    chlorine residual  (OT).

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                                                                      17
                           o
ing the series was 1.8 x 10/100 ml.  From an initial  count of 6.8 x
10^-7.0 x 105/100 ml  in the unchlorinated effluent, the fecal  coliforms
were rapidly reduced  to <100/100 ml.  They continued to decrease in all
samples during this series until, after 240 minutes elapsed time, all
samples contained <5/100 ml (shown as 5/100 ml  in Figure 3).  The aver-
age fecal streptococci number was reduced to <1000/100 ml  from initial
                      5
counts of 2.1-6.1 x 10 /100 ml.   The lowest average number was 110/100 ml
with 30/100 ml as the lowest count in any sample.
Disinfection Studies  a_t <1C Using 6J3 Minutes Theoretical  Contact Time
2 mg/1 Total Chlorine Residual (OT)
     In the 60 minute theoretical contact time:2 mg/1  total chlorine re-
sidual (OT) series at <1C, four replicate experiments were conducted dur-
ing a 23 day period.   The arithmetic mean, maximum and minimum parameter
values for the effluent samples  examined in this series are presented in
Table 2.
     The total chlorine residual, total coliform, fecal coliform and fe-
cal streptococci results for this series of experiments are shown in Fig-
ure 4.  Monitoring of the effluent was begun after the system had operated
for 120 minutes.  The average total chlorine residual, as  measured by the
OT method, continued  to increase from 1.4 mg/1  at 120 minutes to 2.3 mg/1
at 420 minutes elapsed time.  The minimum and maximum concentrations were
1.1 mg/1 at 120 minutes and 2.5 mg/1 at 420 minutes, respectively.  The
residual, as measured by the iodometric method, did not show the continu-
ous increase found with the OT method but became stable at 5.6-5.8 mg/1

-------
                                                                       18
Parameter
Initial temperature, C
Final temperature, C
Initial pH
Final pH
Chlorine added as HOC1 , mg/1
TS, mg/1
TVS, mg/1
TSS, mg/1
VSS, mg/1
VDS, mg/1
TDS, mg/1
NH3-N, mg/1
N02-N, mg/1
N03-N, mg/1
Kjeldahl-N, mg/1
COD, mg/1
Arithmetic 
mean
0.4
0.5
7.2
7.3
6.8
470
285
70
49
188
363
19.0
0.022
0.072
23.8
263
Maximum
value
0.6
0.6
7.3
7.4
7.7
540
340
no
78
220
400
22
0.04
0.08
25
332
Minimum
value
0.3
0.4
7.0
7.1
6.3
440
240
52
35
160
330
14
0.01
0.07
23
215
Number
of
samples
4
4
4
 4
4
4
4
4
4
4
4
4
4
4
4
4
Table 2.  Effluent Sample Parameters  from Flow Through Contact Chamber
          Studies at <1C.
               60 Minutes Theoretical  Contact Time, 2 mg/1
               Total Chlorine Residual  (OT).

-------
                                                                              19
  io8
  io7
 OlO6
 O>
 o
o
o
I04
CD
U
O
  IO1





  IOC


   7
                                        O    TOTAL COLIFORMS

                                        A    FECAL COLIFORMS

                                        D    FECAL STREPTOCOCCI
o>
E
o
V)
                                                  O   IODOMETRIC  RESIDUAL

                                                  D   ORTHOTOLIDINE  RESIDUAL
I
30   60   90   120    150   180  210   240   270
                     ELAPSED  TIME, minutes
                                                       300   330   360  390   420
     Figure 4.   Average number of bacteria surviving  disinfection at  <1C
                with corresponding total chlorine  residual average and  range.
                     60 minutes theoretical contact time, 2 mg/1
                     chlorine  residual (OT).

-------
                                                                       20
after 240 minutes elasped  time.   During the time when the average residual
was stable, the minimum and maximum residuals recorded were 5.2 mg/1  and
6.2 mg/1, respectively.
     The total  coliforms in the  unchlorinated effluent ranged from  1.6  to
        7                                                  4
7.4 x 10/100 ml, and  were reduced to an average of 2.2 x 10/100 ml  of
effluent from the contact  chamber after 120 minutes of elapsed time.  The
total coliforms continued  to  decrease until the average number surviving
disinfection was 830/100 ml  after 210 minutes with the range of 420/100 ml
           3
to 1.5 x 10/100 ml.   The count/100 ml remained >1000 in one of the  four
                                                                  3
experiments during this  series  and ranged between 1.1 and 1.7 x 10
throughout that experiment.   In spite of the high numbers in one  experi-
ment, the average count  remained <1000/100 ml after 210 minutes with a
low of 120/100 ml.  The  lowest  total coliform number recorded during this
series was 23/100 ml.
     The initial fecal  coliform numbers were 5.2-7.3 x 10 /100 ml, and
were reduced to <200/100 ml  by  the time the first sample was taken at 120
minutes elapsed time.   After a  somewhat unstable period, the count was  re-
duced to <5/100 ml at 240 minutes in all experiments and remained at this
very low level.  Fecal  streptococci, initially 3.4-6.0 x 10  , were reduced
to an average of <100/100 ml  of contact chamber effluent after 210 minutes
elapsed time and remained fairly stable.
Dye Studies ajt 3_0_ Minutes Theoretical Contact Time
     Typical results for instantaneous and continuous dye injection  at  the
30 minutes theoretical  contact  time flow rate are shown in Figure 5.  In

-------
                                                                21
z
o
I-  2

%  ?  i
?  3
UJ  Z
"  UJ
CO  O

u  co

<  o
I-  ID
         00  O
         ?  O
                                                     O
                                                    -CM
                                                     O
                                                     O
                                                        ul
                                                     o  1
                                                        o
                                                        LU
                                                        UJ
                                                     o
                                                     CVJ
            oo   ooo    ooooo
            OCDI^tOio^rOcW   

            S1INH 30N30S3dOn"ld  3AllV13d
Figure 5.  Instantaneous and continuous  dye injection  in flow through
          contact chamber studies.
               30 minutes theoretical contact time.

-------
                                                                       22
all instantaneous injection  trials, four minutes were required  for the dye
to be detected in effluent from the contact chamber.  The  dye concentration
increased rapidly and reached  its peak 28 minutes after  injection.  At this
flow rate, 58 percent of the dye remained in the chamber for the 30 minutes
theoretical contact time, and  it required 32 to 33 minutes for  50 percent
of the dye to leave the contact chamber.  Only four percent of  the dye had
60 minutes or more residence time.  The Morril index was found  to be 2.9
indicating a considerable divergence from plug flow.
     Although time of initial  dye detection in the continuous injection
studies was nearly the same  as for the instantaneous injection, the con-
centration increased at a slower rate.  Maximum concentration was reached
after about 65 minutes and remained essentially stable as  long  as dye was
being injected.
Disinfection Studies a_t <1C Using 30 Minutes Theoretical  Contact Time
2.5 mg/1 Total Chlorine Residual (OT)
     The three replicate experiments for the 30 minute theoretical contact
time:2.5 mg/1 total chlorine residual  (OT) series were conducted over a 34
day period.  During this time, several of the effluent parameter values
shown in Table 3 deviated from the typical range for the entire study per-
iod.  The ammonia and Kjeldahl nitrogen concentrations were all higher than
those found during any other series.  Several other parameters  had consist-
ently, high values even though  maximums for the entire study were not neces-
sarily obtained during this  series.  These parameters were: initial and
final effluent temperature in  the contact chamber, total solids, volatile

-------
                                                                       23
Parameter
Initial temperature, C
Final temperature, C
Initial pH
Final pH
Chlorine added as HOC1 , mg/1
TS, mg/1
TVS, mg/1
TSS, mg/1
VSS, mg/1
VDS, mg/1
IDS, mg/1
NH3-N, mg/1
N02-N, mg/1
N03-N, mg/1
Kjeldahl-N, mg/1
COD, mg/1
Arithmetic
mean
0.6
0.9
7.2
7.4
8.5
497
233
89
73
137
403
29.0
0.033
0.053
32.0
306
Maximum
value
0.9
1.0
7.5
7.6
11.3
500
250
no
88
160
420
32
0.04
0.08
34
320
Minimum
value
0.2
0.9
7.1
7.2
6.7
490
220
71
55
120
390
27
0.03
0.03
31
283
Number
of
samples
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
Table 3.  Effluent Sample Parameters from Flow Through Contact Chamber
          Studies at <1C.
               30 Minute Theoretical Contact Time, 2.5 mg/1
               Total Chlorine Residual (OT).

-------
                                                                       24
suspended solids,  total  dissolved solids, nitrite nitrogen and  COD.
     Following initial  chlorine  injection, the contact chamber  was oper-
ated for 60 minutes before  starting chlorine residual and bacteriological
monitoring.  The results are  presented  in Figure 6.  At 60 minutes elapsed
time, the average total  chlorine residual (OT) reached 1.6 mg/1.  The  con-
centration continued to increase, reaching a 1.9 mg/1 plateau after  90
minutes.  Between 120 and 135 minutes,  a second concentration increase be-
gan and reached 2.5 mg/1 when the sample was taken at 150 minutes elapsed
time.  The average total chlorine residual then remained quite  stable  at
2.5-2.6 mg/1.  Between 150  and 210 minutes elapsed time, the minimum and
maximum values determined by  the OT method were 1.8 and 3.3 mg/1, respec-
tively.  The average chlorine residual  by the iodometric method ranged be-
tween 5.3 and 5.7 mg/1  starting  with  the measurements at 150 minutes.   Dur-
ing the same time period, the minimum concentration was 4.6 mg/1 and the
maximum was 7.2 mg/1.
     The total coliforms in the  unchlorinated effluent ranged between  1.2
            7                                                       4
and 2.3 x 10/100 ml.  Those  surviving  disinfection averaged <1  x 10 /100 ml
after 90 minutes elapsed time with the  lowest average number being 2.7 x
  3
10/100 ml.  During one experiment in this series, numbers <1000/100 ml
were recorded at two time intervals with the lower being 630/100 ml.   From
initial numbers of 3.8-8.9  x  10  /100  ml, the average fecal coliform  count
was reduced to 23/100 ml after 90 minutes elapsed time.  The average then
remained very low, except for the 120 minute samples which contained an
average count of 160/100 ml (450/100  ml maximum).  The initial  fecal strep-

-------
                                                                             25
  10
  io
  10
 o
o>
o
EI05
o
o
IKJ*
oc
tlJ
HI
3'*
  10'
  10
                        TOTAL COLIFORMS
                        FECAL COLIFORMS
                        FECAL STREPTOCOCCI (TOO NUMEROUS  TO COUNT)
V) 4
Ul
(E
LJ 3
 _l
 <
        O
        D
IODOMETRIC  RESIDUAL
ORTHOTOLIDINE RESIDUAL
              30
                        60
                       90        120
                  ELAPSED TIME, minutes
                                           150
ISO
    Figure 6.  Average number of bacteria surviving  disinfection at <1C
               with corresponding total chlorine  residual  average and  range.
                    30 minute theoretical contact time,  2.5 mg/1
                    chlorine  residual (OT).

-------
                                                                      26
                              c
tococci count was 5.1-9.5 x  10 /TOO ml in this series of experiments,  and
their removal by disinfection  presented somewhat of an anomaly.   During
the first experiment 110-210/100 ml remained in effluent from  the contact
chamber after 90 minutes elapsed time.  The count was >500/100 ml  through-
out the second experiment and  was recorded as Too Numerous To  Count (TNTC).
Effluent volumes for filtration were adjusted during the third experiment
                                                    3
to accommodate the higher number.  However, >2.3 x 10  streptococci  were
present and were again  recorded as TNTC.  Since no average number could
be established, fecal  streptococci results are not shown in  Figure 6.
Dye Studies ajt 120 Minutes Theoretical Contact Time
     Typical results of instantaneous and continuous dye injection at  the
120 minute theoretical  contact time flow rate are shown in Figure 7.  Dye
was first detected in effluent from the chamber 28 minutes after instan-
taneous dye injection (28 to 30 minutes for all results).  The concentra-
tion increase was essentially continuous, but did not produce  a  smooth
curve at this flow rate.  The first point of interest on this  curve is
that the area remaining under the curve after 60 minutes elapsed time  in-
dicated that 73 percent of the dye was still in the contact  chamber.  The
peak was reached in 65 minutes, and 81 to 82 minutes were required for 50
percent of the dye to be discharged in the effluent.  Only 24  percent  of
the dye had a residence time equal to or greater than the 120  minutes  theo-
retical contact time.   The dye concentration curve was extrapolated to zero
at 225 minutes to permit an  approximate Morril index determination.  This
index was 3.4 indicating a rather extreme departure from plug  flow.

-------
  100


OT 90

1 80
Ul
" 70
tJ
O 6O
V) bu
UJ
g 50
13

u! 40
Ul
  20

   10

   0
                                INSTANTANEOUS  DYE INJECTION

                                CONTINUOUS  DYE INJECTION
                               80   ~  100    T20     J40     160     180    200    220   240~   260~
                                        '  ELAPSED  TIME, minutes
           20     40
280
     Figure 7.   Instantaneous and continuous  dye  injection in flow through contact chamber studies.
                     120 minutes theoretical  contact time.
                                                                                                                 ro

-------
                                                                       28
     The curve produced by continuous  dye  injection was erratic  throughout
most of the 280 minutes the contact  chamber was operated.  There appeared
to be an unstable concentration plateau which  started at about 105 minutes
and continued until  165 minutes had  elapsed.   The dye concentration then
increased and approached a fairly  stable plateau between 230 and 280 min-
utes elapsed time.
Disinfection Studies at <1C Using 120 Minutes Theoretical Contact
Time 1 mg/1 Total Chlorine Residual  (OT)
     The two experiments in this series were conducted during an 18 day
period.  The parameter values for  both experiments are shown in  Table 4.
These are comparable to other values obtained  throughout the study.
     Bacteriological and total chlorine residual results for both exper-
iments are presented in Figures 8  and  9.   Monitoring of the  total chlo-
rine residual by both methods was  started  after 60 minute.s elapsed time.
Little or no residual (OT) appeared  in the contact chamber effluent prior
to 120 minutes, but then a continuous  increase was observed, reaching a
maximum concentration of about 0.8 mg/1.   There was approximately 60 min-
utes difference between the two experiments  in the time required to reach
both the 0.5 mg/1 residual level and the maximum residual level  measured
by the OT method.  When the first  chlorine residual samples  were taken at
60 minutes, the iodometric method  indicated  the presence of  0.76 and 1.0
mg/1 chlorine, and continued to show an increase to stable concentrations
of 2.7 and 2.9 mg/1.  These concentrations were both recorded initially
at the 330 minute elapsed time sampling.

-------
                                                                       29
Parameter
Initial temperature, C
Final temperature, C
Initial pH
Final pH
Chlorine added as HOC1 , mg/1
TS, mg/1
TVS, mg/1
TSS, mg/1
VSS, mg/1
VDS, mg/1
IDS, mg/1
NH3-N, mg/1
N02-N, mg/1
N03-N, mg/1
Kjeldahl-N, mg/1
COD, mg/1
Experiment #1
0.8
0.8
7.0
7.0
5.2
410

59
49
300
340
21
0.01
0.03
24
241
Experiment #2
0.6

7.2
7.3
4.5
410
250
57
36
140
320
16
0.01
0.03
20
202
Table 4.  Effluent Sample Parameters from Flow Through Contact Chamber
          at <1C.
               120 Minutes Theoretical Contact Time, 1 mg/1
               Total Chlorine Residual (OT).

-------
                                                                           30
 io7
o>
o
if
a:
ui
o
 10'
                                              TOTAL COLIFORMS


                                              FECAL COLIFORMS


                                              FECAL STREPTOCOCCI


                                              TOO NUMEROUS TO COUNT
 E

 - 3
O

V)
LU2
oc.

UJ
3  '
X
o
I
                O  IODOMETRIC  RESIDUAL


                D  ORTHOTOLIDINE  RESIDUAL
150   180   210   240  270


 ELAPSED TIME,  minutes
3OO   330   360  390   420
    Figure 8.  Number of bacteria surviving disinfection  at <1C with

               corresponding total chlorine residuals.

                    120 minutes theoretical contact time, 1  mg/1

                    residual (OT).

-------
                                                                         31
  I07
  10"
                      o
                      A
                      D
O
O
CT
Ul
  io2
  10'
TOTAL COLIFORMS
FECAL COLIFORMS
FECAL STREPTOCOCCI
TOO  NUMEROUS TO COUNT
_ I0
o>  _
E  3
2
UJ
I  '
o
O   IODOMETRIC  RESIDUAL
O  ORTHOTOLIDINE  RESIDUAL
30   60    90
                          120   I5p   180   210  240  270   300  330 -   360
                             ELAPSED  TIME,   minutes
    Figure 9.   Number of bacteria surviving disinfection at <1C with
               corresponding total chlorine residuals.
                    120 minutes theoretical contact time,
                    1 mg/1 chlorine residual (OT).

-------
                                                                       32
     The total  coliform numbers were  5.5  and  9.2  x  10   in  the unchlorinated
effluent, and were reduced to <1 x  10/100 ml  at  the 210 minutes elapsed
time.  The elapsed time for total coliform reduction to <1000/100 ml  was
about 300 minutes in Figure 8 (980/100 ml) and 240  minutes in Figure  9
(850/100 ml) which were the times required for the  chlorine residual  to
reach 0.5 mg/1  (OT).  Although the  elapsed times  differed  by 60 minutes,
the rates of decrease were similar  with final  counts of 45/100 ml  (Figure
8) and 25/100 ml  (Figure 9).
                                                          5
     The initial  fecal  coliform counts of 2.7 and 3.7  x 10  were reduced
to <200/100 ml  in no more than 210  minutes elapsed  time.  There was consid-
erable dissimilarity in the rates of  decrease after 210 minutes, but the
numbers were reduced to <5/100 ml during  the  last 60 minutes the system
was operated.  The fecal streptococci  initial  counts were  4.7 and 6.6 x
10 /100 ml.  The number of these bacteria surviving disinfection in the
two experiments followed nearly the same  rate of  decrease  with 280/100 ml
(Figure 8) and 220/100 ml (Figure 9)  remaining viable  at 210 minutes  elap-
sed time.  When the last samples were taken,  the  effluent  still contained
140/100 ml (Figure 8) and 100/100 ml  (Figure  9).
Batch Treatment Disinfection  a_t <1C  60_ Minutes Using  Contact Time,
]_ mg/1 Total Chlorine Residual (OT)
     A batch treatment control was  run in parallel  with each of the 14 dis-
infection experiments conducted in  the flow through system at <1C.  The
solids, nitrogen and the COD concentrations  (Tables 1, 2,  3, 4) apply to
the effluent used for batch treatment.  Other parameters for batch treat-

-------
                                                                       33
ment at <1C are presented in Table 5.  It was not possible to maintain a
uniform temperature throughout the controlled temperature room because
the air flow patterns created warm and cold spots.  Although the room tem-
perature was adjusted to maintain <1C in the contact chamber, some parts
of the room deviated more than 1C from this setting.  The temperature
variation affected the small effluent volume used for batch treatment, re-
sulting in batch temperatures which exceeded 1C during five of the exper-
iments.  This is reflected in.the average and maximum temperatures shown
in Table 5.  During two of the experiments, it was not possible to obtain
final counts for total coliforms, fecal coliforms or fecal streptococci
and the total coliforms were TNTC in a third experiment.  This biased the
final average and maximum bacteria counts in Table 5 to some extent, but
the numbers reported still indicate what was generally found.
Disinfection Studies at 1QC
     An attempt was made to obtain comparative disinfection results with
the flow through system at 10C.  However, the transition from winter to
spring in the Fairbanks area began approximately one month earlier than
expected in 1973 and flow through the city waste treatment system increased.
The increased flow may have caused dilution of the wastewater in the' sys-
tem as shown by the parameter values in Table 6.  Most of these concentra-
tions were either lower than the minimum values recorded or in the low.end
of the value range found during the <1C studies, suggesting that direct
comparison with the <1C results would be unsatisfactory.  Nevertheless,
two experiments were conducted to acquire some information on what might

-------
Table 5.   Effluent Parameters of Samples  Subjected to  60 Minutes Batch  Disinfection  at <1C in
           Parallel with  the Flow Through  System.
Parameter
Initial temperature, C
Final temperature, C
Initial pH
Final pH
Chlorine added as HOC1 , mg/1
Final chlorine residual:
iodometric method, mg/1
orthotolidine method, mg/1
Initial total coliform count/100 ml
Final total coliform count/100 ml
Initial fecal coliform count/100 ml
Final fecal coliform count/100 ml
Initial fecal streptococci
count/100 ml
Final fecal streptococci
count/ 100 ml
Average
0.9
1.0
7.2
7.2
5.4
3.9
0.98
2.7xl07
132
4.8xl05
20
5.2xl05
67
Maximum
1.9
2.4
7.5
7.5
7.8
4.9
1.5
7.4xl07
 470
8.9xl05
220
9.5xl05
230
Minimum
0.4
0.4
7.0
7.0
4.2
3.0
0.46
5.5xl06
30
6.8X101*
<5b
2.1xl05
5a
Number
of
samples
14
14
14
14
14
13C
14
14
llc
14
12C
14
12C
   j* Average of less than 20 colonies per filter when  triplicate filters were examined.
     No coliform colonies on any  filter when triplicate  filters were examined.
   c Results not available for  some samples.
CO

-------
                                                                      35
Parameter
TS, rng/1
TVS, mg/1
TSS, mg/1
VSS, mg/1
VDS, mg/1
IDS, mg/1
NH3-N, mg/1
N02-N, mg/1
N03-N, mg/1
Kjeldahl-N, mg/1
COD, mg/1
Experiment #1
400
210
78
40
150
300
13
0.01
0.04
17
170
Experiment #2
370
210
56
34
'120
330
12
0.01'
0.03
15
150
Table 6.  Effluent Parameters Common to Samples Examined at 10C.

-------
                                                                       36
be expected when the  effluent  temperature in the contact chamber  was
raised from <1C to 10C.
     One experiment was  conducted with 60 minutes theoretical  contact
time and 1  mg/1  total  chlorine residual  (OT) in the contact chamber and
the second  with  30 minutes  theoretical contact time and 2 mg/1  total  chlo-
rine residual  (OT).   In  parallel with each experiment,.batch treatment
was conducted  at both <1C  and 10C using 60 minutes contact time and
1 mg/1 total chlorine residual  (OT).  Figure 10 shows the results of  the
60 minutes  theoretical contact time experiment.  The total chlorine re-
sidual (OT) reached the  maximum concentration plateau of 0.76-0.85 mg/1
after 180 minutes elapsed time, and 120  minutes was required to reach
the 2.2-2.5 mg/1 plateau measured by the iodometric method.  The  total
coliforms were reduced from an initial count of 3.0 x 10 /TOO  to  a low of
1000/100 ml after 180 minutes  elapsed time.  The count then increased to
2.0-2.5 x 103/100 ml  where  it  remained.  Starting with 4.0 x 105  fecal
coliforms/100 ml, disinfection reduced the count to 5/100 ml at the 180
minute elapsed time sampling and the number did not increase after this
                                                      5
time.  The  initial fecal streptococci count of 3.9 x 10 /100 ml was re-
duced to 95/100 ml after 180 minutes, and remained near this number.
     The 30 minute theoretical  contact time results are presented in  Fig-
                                                     t,
ure 11.  The total chlorine residual (OT) reached the plateau  in  no more
than 60 minutes  and remained in the 1.5-1.7 mg/1 range.  During the same
time period, the iodometric total chlorine residual was on a 3.1-3.4  mg/1
plateau.  The total coliforms  started with an initial count of 1.7 x

-------
   I08
                                                                       37
   10'
   10*
o
O
   I03
o
m
   I0<
   10'
                                      O    TOTAL COLIFORMS

                                      A    FECAL COLIFORMS

                                      D    FECAL STREPTOCOCCI
_  10*-
O
CO
tlJ
2
(T
O
_J
I
O
                                           O  IODOMETRIC  RESIDUAL
                                           D  ORTHOTOLIDINE RESIDUAL
               60
         90    120    I5O   180   210

           ELAPSED TIME, minutes
240   270   300   330
Figure  10.
Number of bacteria surviving disinfection at 10C with
corresponding total chlorine residuals.
     60 minutes theoretical contact time,
     1 mg/1 chlorine residual (OT).

-------
                                                                  38
                    TOTAL  COLIFORMS (TOO NUMEROUS TO COUNT)

                    FECAL  COLIFORMS

                    FECAL  STREPTOCOCCI
                                         O  IODOMETRIC RESIDUAL

                                         D  ORTHOTOLIDINE  RESIDUAL
                   90         120         150

                   ELAPSED  TIME, minutes
                                         180
>to-
Figure  11.
Number  of bacteria surviving disinfection at 10C with
corresponding total  chlorine residual.
     30 minutes theoretical contact time,
     2  mg/1 chlorine residual (OT).

-------
                                                                       39
107/100 ml and were reduced to 3.1  x 10/100 ml  after 60 minutes elapsed
                                        3
time.  The count then remained >8.3 x 10/100 ml  which was reported as
TNTC and does not appear in Figure 11.   The initial  fecal coliform count
of 3.4 x 10 /100 ml was reduced to 15/100 ml after 90 minutes, and re-
mained in the 5-10/100 ml  range after that time.   The initial  count of
3.2 x 10  fecal streptococci/100 ml was reduced  to 210/100 ml  at the 90
minute sampling and remained between 130 and 200 for the rest of the time
the contact chamber was operated.
     The parameter values  for the batch controls  at 10.C and <1C, along
with the temperature and pH values for  the contact chamber, are shown in
Table 7.  When the effluent was brought to the laboratory, a small por-
tion was cooled immediately to <1C and the rest  was adjusted to 10C.
As soon as the effluent was brought to  temperature, samples were taken
for an immediate total coliform, fecal  coliform  and fecal streptococci
count (experiment #2 only).  The results indicated that changing the ef-
fluent temperature did not alter the numbers of  bacteria present.  The
effluent was then held overnight at those temperatures.  When the ini-
tial counts were made at the start of each experiment on the second day,
there was a four to six fold difference in the total coliform numbers at
the two temperatures.  However, this does not provide an adequate explan-
ation for the poor total and fecal  coliform results at 10C in experiment
#1.  .

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Table  7.   Effluent  Parameters of  the 10C Flow Through System and Parallel  60 Minute  Batch
           Disinfection at 10C  and <1C.
Parameter

Initial temperature, C
Final temperature, C
Initial pH
Final pH
Chlorine added as HOC1 , mg/1
Final chlorine residual:
iodometric method, mg/1
orthotolidine method, mg/1
Initial total coliform count/100 ml
Final total coliform count/100 ml
Initial fecal coliform count/100 ml
Final fecal coliform count/100 ml
Initial fecal streptococci count/100 ml
Final fecal streptococci count/100 ml
Experiment #1
Flow
through
system3
10.0
10.0
7.1
7.1
5.0
	
	
S.OxlO7
	
4.0x105
	
3.9xl05
	
Batch

10C
10.3
10.5
7.1
7.2
5.0
2.7
1.1
3.0xl07
	 c
4.0xl05
TNTCf
3.9xl05
260


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                                                                       41
                            Discussion
     The hydraulic performance of chlorine contact chambers having various
configurations has been the subject of considerable study and discussion
during the past few years (7, 21, 23, 28, 30, 33, 35).   The two major con-
siderations pointed out in these reports are:  that the chlorine should be
thoroughly and rapidly mixed with the wastewater before entering the con-
tact chamber, and that the contact chamber design should be such that the
hydraulic performance approaches plug-flow.   Even attaining plug-flow
would not be adequate unless the actual  residence time  of the thoroughly
mixed wastewater and chlorine in the contact chamber is long enough for
the enteric bacteria to be reduced to an acceptable number.
     In current disinfection practice, non-plug-flow (short-circuiting)
characterizes contact chamber hydraulic performance. The extent of short-
circuiting is a measure of the degree to which the chlorine and waste-
water have less than theoretical residence time before  leaving the chamber.
The degree of short-circuiting may be such that the effluent is inade-
quately disinfected unless excessive chlorine has been  added before en-
tering the chamber.  These problems will continue to exist as long as
wastewater disinfection receives minimal design and operational attention.
     The configuration of the contact chamber used in this study, and
the method of adding chlorine before entering the contact chamber, pro-
vided a system which is comparable to any system that might be designed
in accordance with the previously mentioned guidelines  (11).  Short-
circuiting was a serious problem even though the contact chamber was well

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                                                                       42
baffled.   When the dye  studies at the three flow rates were compared  (Fig-
ures 2, 5, 7), the amount  of dye having a residence time at least equal  to
the theoretical  contact time decreased with decreasing flow rate.  That  is,
short-circuiting appears to be magnified at lower flows.  However, the
amount of dye having  at least 60 minutes residence time increased with de-
creasing  flow rate.   Plug-flow was not approached at any of the flow  rates,
and only the 120 minutes theoretical contact time provided residence  time
approximating that obtained with 60 minutes batch treatment.   In other
words, a  reactor volume twice the design volume would probably provide more
adequate  exposure time.
     The disinfection guidelines (11) recommended a 1 mg/1 total chlorine
residual  after 60 minutes  contact time, but did not specify a  method  for
chlorine residual determination.  Since the OT method is still widely
used for monitoring chlorine residual, it was selected for use during
the first phase of the  study  (16).  Minimum effective disinfection  (less
than 1000 total  and 200 fecal coliforms/100 ml of effluent) could be  re-
liably achieved at <1C in the presence of 1 mg/1 total chlorine residual
(OT) after 60 minutes contact time, but the reliability decreased as  re-
sidual concentrations decreased below 1 mg/1.
     It has been well established that there can be a considerable dif-
ference between the total  chlorine residual concentrations measured in
treated wastewater by the  OT and iodometric methods (1, 25).   The dif-
ference in concentrations  measured by the two methods is usually in the
2 to 5 mg/1 range and may  be even greater (1), the iodometric  method  in-

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                                                                       43
cheating the higher residual.   Some of the residual  measured  with the
iodometric method, and not measured with the OT method,  is  probably in
a tightly bound form which is  ineffective in the disinfection process
(25).  However, there is evidence that disinfection  can  proceed  even
when no chlorine residual  can  be demonstrated with the OT method (7, 25).
     All of the results presented here show that the total  chlorine resi-
dual measured by the iodometric method is significantly  greater  than that
measured by the OT method.  If the recommended 1  mg/1  total chlorine re-
sidual (11) is measured with the iodometric method,  it is obvious that
an actual contact time considerably longer than 60 minutes  would be re-
quired to achieve effective disinfection at <1C and probably at 10C;
assuming effective disinfection could be attained at all  with such low
residual.
     Since there is no apparent correlation between  the  total  chlorine
residual measurements with the two methods, both the OT  and iodometric
methods were used during this  study.   The OT method  was  used  as  the basis
for establishing the desired residual, and the iodometric method was used
for comparative purposes.   The results (Figures 3, 4,  6,  8, 9, 10, 11)
showed that operating temperatures of <1C apparently did not alter the
previously observed differences between the two methods.
     Some of the chemical  and  physical effluent quality  parameters (Tables
1, 2, 3, 4, 6), as well as effluent residence time in the contact chamber,
appeared to affect the chlorine demand.  The chlorine concentration to
satisfy this demand, and to maintain a particular residual, seemed to be

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                                                                      44
closely related to the ammonia  nitrogen concentration and more  casually
related to solids components.   After the chlorine demand was  satisfied,
the effluent quality parameters apparently were not a significant factor
in the disinfection process  as  <1C with effluent from  this source.   Simi-
lar observations have been made under other operating conditions  (7).
     Under some operating conditions, the disinfection  process  has been
shown to be dependent on the contact time and  total chlorine  residual  as
measured by the amperometric method (7, 35).   Since the amperometric and
iodometric methods give essentially the same results  (1, 25), disinfection
at <1C would be expected to be more closely related  to the total  chlorine
residual as measured by the  iodometric method  than by the OT  method.  How-
ever, this relationship was  somewhat less obvious than  expected at both
operating temperatures (<1C and 10C).  Regardless of  the flow rate
through the contact chamber, a  chlorine residual measureable  by the OT
method was necessary before  significant bactericidal  action was apparent
(Figures 3, 4, 6, 8, 9, 10,  11).  The extent of the reduction was thus de-
pendent upon both total chlorine residual concentration (OT), and resi-
dence time.
     Reduction of total coliforms to an acceptable number  (<1000/100 ml)
proved difficult to accomplish  in the flow through system at  <1C.  In
fact, this level of disinfection was not attained at  the 60 minutes theo-
retical exposure time until  the total chlorine residual  (OT)  approached
2 mg/1 (Figures 3 and 4). With the 30 minutes theoretical residence, a
total chlorine residual (OT) of 3.3 mg/1 was not effective  (Figure 6).

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                                                                       45
Extending the theoretical reaction time to 120 minutes permitted effective
disinfection to be achieved with only a 0.5-0.6 mg/1  total  chlorine resid-
ual (OT) as shown in Figures 8 and 9.  When the residual  was increased to
approximately 0.8 mg/1, the total coliforms were held at  <100/100 ml  of
effluent.  This suggested that the contact time is at least as important
for total coliform reduction as the maintenance of a  particular chlorine
residual.  Probably the most significant point was that the 120 minutes
theoretical contact time was the only one which provided  60 or more min-
utes residence time for more than 50 percent of the effluent.
     No problems were encountered in reducing the fecal coliform numbers
to <200/100 ml of effluent (minimum effective disinfection) at <1C.
Average numbers of <5/100 ml were eventually achieved at  all flow rates
(Figures 3, 4, 6, 8, 9).  However, minimum effective  disinfection was not
attained at the 30 minutes theoretical  contact time until  the chlorine
residual (OT) was in excess of 1.6 mg/1 (Figure 6).  When the theoretical
contact time was 120 minutes, approximately 0.3 mg/1  total  chlorine re-
sidual (OT) was required for minimum effective disinfection (Figures 8
and 9).  Again, as with the total coliforms, this suggested that resi-
dence time in the contact chamber is as important as  total  chlorine re-
sidual.
     The reason for enumerating fecal streptococci in water pollution
control has generally been to aid in more accurately  defining the source
of warm-blooded animal pollution (14).   Even though the intestinal tract
of man and other warm-blooded animals is a normal habitat of these bac-

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                                                                      46
teria (1), no guidelines have been established for  the  number  of fecal
streptococci permitted in effluent from disinfection  contact chambers.
The fecal  streptococci have a different cell  structure  than the coliforms
and related bacteria,  consequently treated wastewater disinfection with
chlorine would not necessarily affect  these groups  in the  same manner.
During this series of  experiments at <1C, some  possible differences  were
noted.  When the theoretical  contact time was 60 minutes,  increasing  the
chlorine residual  from 1 mg/1  (Figure  3) to 2 mg/1  (Figure 4)  affected
the fecal  streptococci in a manner very similar  to  that observed with the
total coliforms.  When the theoretical contact time was reduced to 30 min-
utes, chlorine appeared to be less effective  against  the fecal strepto-
cocci than against either coliform group  (Figure 6).  At the  120 minutes
theoretical contact time flow rate (Figures 8 and 9), the  reduction in
fecal streptococci numbers was very similar to that found  with 1  mg/1 and
60 minutes contact time.  This was in  contrast to the rather  sharply re-
duced numbers of total coliforms at 120 minutes  contact time.   Thus,  it
appeared that the contact time was the controlling  factor  in fecal strep-
tococci reduction until a certain minimum was reached (approximately 60
minutes) with additional contact time  having  little apparent effect.
After this minimum time was reached, the chlorine residual concentration
(OT) became the factor controlling fecal streptococci numbers  in the con-
tact chamber effluent.
     It has been demonstrated during this series of experiments (Table  5),
and during the first phase of the study (16), that  effective disinfection

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                                                                       47
of treated wastewater could be achieved  with a  high  degree  of  reliability
at <1G if the actual contact time was 60 minutes  (batch  treatment)  and
the total chlorine residual was 1  mg/1  (OT). These  results also  indi-
cated that batch treatment provided an effluent bacterial quality far su-
perior to that obtained in the short-circuit plagued contact chamber, un-
less the flow rate through the chamber provided 60 or more  minutes of ac-
tual residence time for a large portion  (>50 percent) of  the effluent
(Figures 8 and 9).  This points out that batch  treatment  laboratory  re-
sults cannot necessarily be extrapolated to operating contact  chambers,
an observation supported by studies conducted under  other conditions (7).
     Experiments conducted in the  contact chamber  at 10C were too limited
in number for the results to give  more than an  indication of what might
occur if the temperature was raised from <1C to 10C.  The contact  cham-
ber results (Figures 10 and 11) did suggest that any improvement  in  ef-
fluent bacterial quality would be  minimal.  This suggestion was also sup-
ported by the parallel batch treatment results  at  10C  and  <1C (Table 7).
Probably the most interesting observations from the  limited 10C  studies
were the apparent changes in numbers of  bacteria present  at 10C  and <1C
during the 24 hours the effluent was held at the two temperatures before
the disinfection studies were started.   The total  coliform  numbers in-
creased several fold at 10C, while they remained  the same  or  decreased
at <1C.  The fecal coliform numbers showed no  change at  10C  and either
no change or a decrease at <1C.  The fecal streptococci  either did  not
change or showed a slight increase in numbers at both temperatures.

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                                                                       48
These results suggested that at least  some  portion of  the  total  coliform
population was sufficiently cold adapted that  significant  reproduction
could occur at temperatures near their minimum for growth.   Similar low
temperature reproduction has been  observed  previously  in a mountain stream
(18).
     During both the batch (16) and  contact chamber  studies  at <1C, fecal
coliforms were usually absent from the chlorinated effluent  samples after
a shorter contact time in the presence of a lower chlorine residual  than
was required to reduce the total coliform numbers to their minimim accep-
table level.  This suggests that fecal coliforms are more  susceptible to
chlorine disinfection at <1C than are the  total coliforms.   Other work
has indicated that this also occurs  at warmer  temperatures (7).   The po-
tentially detrimental effects on surface water quality in  arctic and sub-
arctic regions resulting from this difference  in susceptibility to chlorine
disinfection, and the current trend  to de-emphasize  or not use total col-
iform bacteria in determining recreational  water quality,  have been dis-
cussed previously (16).  It has already been suggested that  total  coliforms
should be retained and used in conjunction  with fecal  coliforms for deter-
mining water quality (7, 16).  This  is particularly  important in the Arctic
and Subarctic because there is little  chance that any  coliform bacteria
come from other than sewered sources during the winter months.
     It has been shown (16) that chlorine varied significantly in its abil-
ity to disinfect effluent from different sources at  <1C,  and it has been
reported that similar variations can be found  with time in effluent from

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                                                                       49
the same source (7, 19).   This points out the fallacy of arbitrary chlo-
rine residual  and contact time criteria, since the only real  measure of
adequate disinfection is  the number of enteric bacteria being discharged
into a receiving water.   It has been suggested that the chlorine resid-
ual rcontact time relationship must be determined for the effluent from
each source if effective  disinfection is to be attained (5,  19).  In addi-
tion, the relationship must be determined at all operating temperatures
encountered in the disinfection system, particularly the lowest tempera-
ture.
     The toxicity of residual chlorine to the biota in receiving waters
has been a subject of increasing interest during the past few years.  A
comprehensive  literature  review has recently been prepared (4) pointing
out that the residual chlorine can be toxic at very low concentrations,
and several interim criteria were suggested for permissible  concentrations
of total residual chlorine in receiving waters.  One particular criterion
is probably of more interest than the others in relation to  this study:
"In areas receiving wastes treated continuously with chlorine, total re-
sidual chlorine should not exceed 0.01 mg/1 for the protection of more
resistant organisms only, or exceed 0.002 mg/1 for the protection of most
aquatic organisms."  No mention was made of the method used  to determine
the chlorine residual, but it was pointed out that the total  chlorine re-
sidual measured with the  amperometric method was most closely related to
biological activity.  Thus, the 0.002 mg/1 residual was probably measured
either by the  amperometric or iodometric method.  It has also been demon-

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                                                                       50
strated that toxic effects  persist for several days  (12).
     Temperature was not included as a factor  in any of the  proposed
toxicity criteria.  The indigenous aquatic organism sensitivity  to  the
total chlorine residual  is  essentially unknown at  low temperatures.   It
is likely,  however, that chlorine toxicity in receiving waters with tem-
peratures approaching 0C is  as  great or greater than at warmer  temper-
atures.  If this toxicity is  superimposed on the low dissolved oxygen
concentrations found in many  arctic and subarctic  rivers during  the win-
ter months, there may be extremely serious consequences (6).
     Considering that the total  chlorine residual  necessary  for  effec-
tive disinfection at <1C (Figures 4, 8, 9) was between 2.7  and  6.2 mg/1
when measured by the iodometric  method, it is apparent that  a very  large
dilution would be needed to reduce the chlorine residual to  0.002 mg/1
or less.  Since most arctic and  subarctic rivers have very low discharge
during the winter months, the least dilution would be available  when  the
highest total chlorine residual  would probably be  required for effective
disinfection.  If effective disinfection is to be  achieved using chlorine,
and toxicity in receiving waters minimized, dechlorination of the efflu-
ent before discharge must be  considered in waste treatment plants opera-
ting in cold climates.  Dechlorination methodology has been  discussed re-
cently (35), and it has been  demonstrated that dechlorinated effluents
are no more toxic to aquatic  organisms than are the  unchlorinated efflu-
ents (12).
     This discussion has pointed out the lengths to which one must  go if

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                                                                       51
effective chlorine disinfection of treated wastewater is  to  be attained
at <1C and at 10C.  The current practice of giving minimal  attention
to the disinfection process not only fails to provide an  effective bar-
rier to the spread of enteric disease, but also ignores the  toxic  ef-
fect of chlorine on the indigenous aquatic organisms in the  receiving
water.  To reduce this to a universal  language:  current  practice  is
simply pouring money down a rat hole,  with the public footing the  bill
and not realizing how little they are  getting for their money.  Since
the use of chlorine as a disinfectant  will no doubt persist  for some
time, technology must be improved so that effective disinfection is
achieved under all but possibly the most extreme conditions.   This means
that disinfection must be given the role of a unit process  having  equal
importance with other unit processes in the treatment system.  However,
under no conditions can disinfection be considered a substitute for ade-
quate treatment of the waste.

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                                                                       52
                            Conclusions
1.   Effective treated  wastewater disinfection can be achieved at  <1C  in
the presence of a 1  mg/1  or  less total chlorine residual, if the  effluent
receives sufficient  contact  time and the total chlorine residual  is meas-
ured by the orthotolidine method.
2.   The contact time is  at least as important as a particular total chlo-
rine residual for attaining  effective disinfection at low temperatures.
Since the chlorine residual:contact time relationship for effective coli-
form reduction varies  with effluent source and temperature, this  relation-
ship should be determined for  each source and set of operating conditions.
3.   The use of total  coliforms, in conjunction with fecal coliforms, is
necessary for ascertaining the effectiveness of treated wastewater disin-
fection and the quality  of receiving waters, at temperatures approaching
0C.
4.   The health effects resulting from inadequately disinfected effluents
being released into  the  receiving water make it imperative that the ex-
tent of enteric pathogenic bacteria survival, as compared to that of col-
iform bacteria, be determined  in receiving waters approaching 0C.
5.   The source and significance of "non-fecal" coliforms (those not giv-
ing a positive elevated  temperature test) found in waste treatment sys-
tems during the winter should  be determined.  Particular emphasis should
be given to the portion  of the population which appears to have a signi-
ficant increase in numbers at  10C.
6.   Operating temperatures of  <1C had little or no effect on the 2-5  mg/1

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                                                                       53
difference between the orthotolldine and iodometric methods of determin-
ing total chlorine residual.  However, one method for total chlorine re-
sidual determination should be specified in order to eliminate possible
confusion.
7.  Treated wastewater disinfection must be considered a unit process
which is given equal consideration with all other processes in the waste
treatment system.  This means that the "State of the Art" should be con-
solidated so that design criteria employing the best technology can be
developed for rapid mixing of effluent and chlorine ahead of the contact
chamber and for contact chamber design which actually minimizes short-
circuiting and allows for maximum rather than average flow.
8.  Total chlorine residual toxicity to the indigenous aquatic organisms
in the receiving water should be established for receiving water temper-
atures approaching 0C.  Emphasis should be given to determining the
possible synergistic effects on the organisms, of the chlorine toxicity
and low dissolved oxygen concentrations frequently found in arctic and
subarctic rivers during periods of ice cover.
9.  Evaluation of disinfectants,  other than chlorine, for possible ap-
plication in effluents at low temperatures, should be accelerated.

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                                                                        54
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     IND-18-69W, Technicon AutoAnalyzer  Methodology.   Technicon  Corp.,
     Tarrytown, N. Y., 1969.

32.   Technicon Corp.  Total  Nitrogen  (Kjeldahl).   Industrial Method 30-69A,
     Technicon AutoAnalyzer  Methodlogy.  Technicon  Corp.,  Tarrytown, N. Y.,
     1969.

33.   Thomas, A. A. and W. H. Brown.   Closed-Loop Chlorination  for Waste-
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     April 1968.

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  34.  Van  Donsel,  D., R. C. Gordon  and C. V. Davenport.   Unpublished  Data.
       Environmental  Protection Agency, Fairbanks, Ak.   1973.

  35.  White,  G.  C.  Handbook of  Chlorination.  New  York, Van Nostrand
       Rheinhold  Co., 1972.  744  p.
* U. S. GOVERNMENT PRINTING OFFICE: 1973-798-165

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