ENVIROi
            OFFICE OF ENFORCEMENT
                 EPA-330/1-74-001
                     and
        Type Automatic   Sampling Techniques
                   on an
NATIONAL FIELD INVESTIGATIONS CENTER-DENVER
              DENVER, COLORADO
               SEPTEMBER 1974

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       ENVIRONMENTAL PROTECTION AGENCY
            OFFICE OF ENFORCEMENT
   COMPARISON OF MANUAL (GRAB) AND VACUUM
     TYPE AUTOMATIC SAMPLING TECHNIQUES
 ON AN INDIVIDUAL AND COMPOSITE SAMPLE BASIS
NATIONAL FIELD INVESTIGATIONS CENTER - DENVER
              DENVER, COLORADO

               SEPTEMBER 1974

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                               DISCLAIMER

     Mention of brand name of equipment does not constitute endorse-
ment or recommendation of product by the Environmental Protection
Agency.  The information and findings presented in this paper are
not to be construed as representing official equipment design or
modification specifications.

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               TABLE OF CONTENTS

  Disclaimer
  Glossary
  I.   Introduction
  II.  Summary and Conclusions
 III.  SERCO Automatic Sampler
  IV.  Field Study Procedure
  V.   Statistical Approach
  VI.  Statistical Analysis of Data
 VII.  Additional Data Evaluation
VIII.  Discussion

  Appendix
  1.  SERCO Automatic Sampler Technical Report
  2.  SERCO Automatic Sampler Specifications

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                                 GLOSSARY
 Composite Sample -       Individual grab samples of fixed volume collected
                          on a regular time basis and combined on the
                          basis of the corresponding volume of flow at
                          the time of collection.

 Individual Grab Sample - One sample of fixed volume collected either
 or Grab Sample           manually or by automatic sampler and analyzed
                          independently.
 TS  - Total Solids

 TSS - Total Suspended Solids

 VSS - Volatile Suspended Solids


 Statistical Parameters
 u = Population mean

 0 = Population standard deviation

°J = Standard error of the population mean

 X" = Sample mean

 S = Sample standard deviation

S  = Standard error of the sample mean
 A

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                            I.   INTRODUCTION

     The National  Field Investigations Center-Denver (NFIC-D)  has  been
engaged in water quality and waste source evaluation studies  since its
inception.  Due to the magnitude of the surveys,  NFIC-D often  has  relied
upon automatic samplers, particularly the SERCO,  to collect samples of
the wastewater streams.  These samplers are used  to collect water
samples over specified periods for subsequent compositing;  individual
grab samples are collected manually.
     With the advent of compliance monitoring, the use of automatic
samplers is expected to increase.   Data provided  by the manufacturer
show that the automatic and manual sampling methods are equivalent
(Appendix).  To confirm that the sampling methods are equivalent,
NFIC-D conducted studies at a local wastewater treatment plant (WWTP)
and statistically evaluated the results.  This paper presents  the  results
of these studies.

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                                   -2-
                       II.  SUMMARY AND CONCLUSIONS
      The  SERCO automatic  sampler was compared with the manual sampling
method on a composite  sample and individual grab.sample basis on
July  16-21, July 22-27, and August 15-22, 1974.  Samples were collected
from  a local wastewater treatment plant and analyzed for total solids,
total suspended solids and volatile suspended solids July 16-27, and
for total suspended solids August 15-22; composite samples were combined
on a  flow weighted basis.
      The  statistical approach used to evaluate the data was the two-tailed
"t" test at a risk level of 5% (95% confidence level).  The pooled  .-
sum of squares method was used to calculate the statistical parameters.
The hypothesis, tested statistically, was formulated:  the mean of the
samples collected by one sampling technique is equal  to the mean of the
samples collected by either a similar sampling technique or different
sampling method.   If the value of "t" calculated from the data was
less  than the tabular value of "t", the hypothesis was accepted.
      The automatic sampler data were also compared with one another to
determine if there was a significant difference in the samples when the
probe inlets faced upstream downstream, or lateral  to the direction
of flow.
     Although the samples were collected in locations where the waste-
water was thoroughly mixed,  the possibility existed that the solids
could vary with depth.   Since the automatic sampler collects samples
at depth, and manual  collection includes surface sampling,  a special sampler

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                                   -3-
manually operated, was fabricated to collect samples at the same depth
as  the automatic sampler.  Results were compared with results from the
manual and automatic sampling methods.
     The sampling frequency for a composite sample was evaluated also.
Samples were collected manually at 15 and 60 minute intervals for 6
hours and composited individually.
     Based on the statistical evaluation, the following conclusions
were made:
                EQUIVALENT ON A COMPOSITED SAMPLE BASIS
     1.  Automatic Sampler and Manual Sampling Method
     2.  Automatic Sampler and Special Sampler
     3.  Automatic Sampler and Automatic Sampler
     4.  Manual Sampling Method and Special  Sampler
     5.  Manual 6-Hour Composite (15-minute interval) and Manual 6-Hour
         Composite (60-minute interval).
     6.  Automatic Sampler and Manual 6-Hour Composite (15 and 60-minute
         intervals).
             EQUIVALENT ON AN INDIVIDUAL GRAB SAMPLE BASIS
     1.  Automatic Sampler and Automatic Sampler-'
     2.  Manual Sampling Method and Special  Sampler
          NOT EQUIVALENT ON AN INDIVIDUAL GRAB SAMPLE BASIS
     1.  Automatic Sampler and Manual Sampling Method
     2.  Automatic Sampler and Special Sampler
a/  The samples collected with the probes in the upstream and downstream
    positions were not equivalent only for the VSS parameter for the
    influent, July 16-21.  Since the VSS parameter was considered unsatis-
    factory for the statistical  comparison, it was concluded that all
    probe positions collected equivalent samples.

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                                    -4-
 In the above comparisons, the automatic sampling method, with the probes
 facing in any position relative to the direction of flow, was equivalent
 to the other sampling methods, except on the individual grab basis.
 In the comparison of automatic sampler vs.  automatic sampler, the position
 of the probe was not significant as samples were equivalent on a composite
 sample basis and grab sample basis.
      The temperature of the first sample collected by the automatic
 sampler was monitored for six and ten hour  periods.   About six hours
 is required for the initial  sample to cool  from'21°C to 4°C.   When the
 bottles and automatic sampler were cooled prior to the  sampling  period
 (i.e.,  overnight),  the time  required  to cool  the sample from  21°C to
 4°C was only three  hours.   When  the ambient air temperature is above
 freezing,  the rate  of temperature drop may  be further increased  by
 replacing  the insulated metal  box housing the sampler,  with a  non-
 insulated  metal  housing,  and  packing  ice between the metal  housing and
 an insulated outer  box.   This  modification  is  currently being done by
 NFIC-D.
     The results confirm  that  the  vacuum type  automatic sampler  evaluated
 in this study may be  used to collect  representative  wastewater samples
 on a composite basis.  Modifications  to the sampler  are necessary  to
 provide adequate sample preservation.
     The findings also raise serious doubts as  to the viability of
 accepted manual grab  sampling methods, particularly with respect to
 high and variable solids collection.  Therefore  NFIC-D  has  initiated an
 ancillary  testing program to develop  reliable grab sampling equipment
and techniques.

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                                   -5-
                      III.   SERCO AUTOMATIC SAMPLER
     The SERCO automatic grab sampler,  Model  NW-8,  works  on  a  vacuum
principle.  Twenty-four, 500 ml  bottles are evacuated  to  approximately
25 inches of mercury by means of an AC  operated vacuum pump.   Each  bottle
is connected by an individual tygon tube or similar tubing  to  an  intake
probe which is immersed in  the wastewater stream.   Samples  are collected
when the mechanical triggers are activated sequentially using  a clock
and distributor arm assembly-'.   As each trigger is activated, the
vacuum on the respective  sample bottle is released and a wastewater
sample is drawn into the bottle.
     The amount of the sample collected depends on  the atmospheric  pressure,
the degree of evacuation, and the lift.  After collection,  the samples
are hand composited on an equal  volume  or flow weighted basis.  The
sampler is readied for the  next compositing period  by  back-flushing the
collection lines with tap water and inserting clean bottles.
     The sampler is housed  in a metal  case.  The 24 bottles encircle
two plastic ice containers  used to preserve samples.  NFIC-D has
modified the unit for summer and winter application.  The entire unit
is placed in a foam insulated plywood box.  For warm weather use,
additional ice is packed between the metal case and plywood box to
increase the rate of temperature decrease and to help maintain low
sample temperatures.  During cold weather conditions,  a heat source
(light bulb), which is controlled by a  thermostat,  is placed inside the
plywood box to prevent the clock, mechanical parts, and samples from
freezing.  The heat source operates with either AC or DC power.
a/  Triggers can be activated at  various  intervals, usually 5, 15
    or 60 minute, depending upon the clock used.

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                                   -6-
     The sampler has proved mechanically reliable under extensive use by
NFIC-D field personnel.  Operational difficulties are minimal and only
routine maintenance is required.
     A more detailed description of the SERCO automatic sampler is
presented in the appendix.

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                                   -7-
                        IV.   FIELD STUDY PROCEDURE
     A  local wastewater  treatment plant was selected for the study due
 to  its  proximity  to  the  NFIC-D  laboratories and reliable flow measuring
 equipment.  The study was conducted over three periods, July 16-21,
 July 22-27, and August 15-22, 1974.
 A.   Parameters Evaluated
     Total solids  (TS),  total suspended solids (TSS), and volatile
 suspended solids  (VSS) were  evaluated for the July studies.   The only
 parameter used in  the August study was TSS since most NPDES permits
 limit suspended solids rather than TS and VSS.  Analyses were done
 according to Methods for Chemical Analysis of Water and Wastes, EPA,
 NERC-AQC Laboratory, Cincinnati, Ohio, July 1971, as specified in the
 October 16, 1973  issue of the Federal Register, "Guidelines Establishing
 Test Procedures for Analysis of Pollutants".
     Field measurements of pH and temperature were made as samples
were collected.  Flows were determined from a Parshall  flume and
 recording device.   During the July study a thermocouple probe was
placed inside an automatic sampler bottle containing the first sample
collected and the rate of temperature decrease was monitored.
B.   Sampling Methods
     To minimize the variations in the data during the  evaluation of
manual  and automatic sampling methods, samples were collected simultaneously.
The trigger mechanisms on the automatic samplers  were tripped by hand
at the same time that manual  samples  were collected.   All  composite
samples were manually combined on a flow weighted basis at the end of

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                                   -8-
the sampling period.  Dye was added periodically at the influent to the
grit chamber to insure that the wastestrearn was mixed thoroughly at the
sampling location downstream from the grit chamber.  Dye was also
added periodically in the final clarifier overflow to the wet-well  to
determine that adequate mixing occurred at this sampling location.   All
samples were preserved under ice and analyzed within two hours at the
laboratory.
     Automatic samplers were compared with the manual sampling method
on an individual grab sample basis and a composite basis.
July 16-21 (Influent)
     Three automatic samplers were placed at the plant influent, each
with a sampling probe inlet facing in a different position, e.g.,
upstream, downstream, and lateral (perpendicular), to the direction of
flow.  Samples were collected hourly for 12 hours with the automatic
samplers and by the manual sampling method and composited at the end of
each 6-hour period, yielding 2 sets of composite samples per sampling
technique daily.  In addition, two 6-hour composites, composed of
24 manually collected samples (15-minute intervals) were collected
sequentially over the 12-hour period to determine if a significant
difference existed as a result of the sample collection frequency at
random intervals.
     Six individual grab samples were collected by each sampling technique
during the 12-hour period.
July 22-27 (Influent and Effluent)
     The automatic sampler probes were placed in the influent and effluent
in the lateral position only, since under many field conditions, this

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                                   -9-
 is  the  only  position available due to the limitations of the probe length
 and the configuration of the sampling location.  Samples were collected
 hourly  using automatic and manual sampling techniques.  These samples
 were composited at the end of 24 hours.
      Six  individual grab samples, each from the influent and effluent,
 were collected randomly over 24 hours using both sampling techniques.
 August  15-22 (Effluent)
      Four automatic samplers were placed at the effluent wet-well.  Two
 sampling probes were placed with the intakes facing upstream and two
 probes  were placed in a lateral position.  All probes were positioned
 at  the  same depth.  Samples were collected for 12 hours at 1-hour
 intervals and composited at the end of each 6-hour interval, providing
 8 composite samples daily.   In addition, four random grab samples were
 collected daily with each automatic sampler.
     Grab samples were collected manually at the same time that the
 automatic samplers collected samples and composited in the same manner.
 Manual  grab samples were also collected for individual analysis at the
 same times as the automatically collected samples.
     Although the samples were collected at locations where the waste-
water was thoroughly mixed, the possibility existed that the solids
 could vary with depth.   Because the automatic sampler probe is  immersed
 in the wastewater stream and manual  sampling  normally includes  surface
 flow as well  as the flow at depth,  a special  sampler was built  to obtain
a grab sample at the same depth as  the automatic sampler probe.

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                                 -10-
A 500 ml sample bottle was attached to a metal  pole;  a rubber stopper,
mounted on a tripping rod, sealed the bottle until  it reached the desired
depth at which time the stopper was removed, the sample collected, and
the stopper was replaced.  Composite and grab samples were collected
with the special sampler at the same times that the automatic and
manual samples were taken.

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                                   -11-
                         V.   STATISTICAL  APPROACH
 A.    Parameters
      Since  the entire wastewater  stream  could  not be examined to deter-
 mine  actual  values  of the statistical parameters, estimators were used
 to  evaluate  a given parameter.  For example, the sample mean I is an
 estimator for the population mean  u, and the estimator for o, the
 standard deviation  of the population distribution, is S.  When making
 inferences based on estimators, it is necessary to obtain estimates for
 the variances of the estimators.   In the case  of the sample mean, the
              2     2
 variance is  o_  = a /n where n is  the sample size.  To estimate the variance,
  ?    2
 S-rr^ = S /n is substituted.  The standard error of the mean o  is estimated
 X                                                          X
 by S_.
    X
 B.    "t" Test
     The "t" distribution was used to test the hypothesis that the mean of
 the samples  collected by one method is equal to the mean of the samples
 collected by another method, e.g., composite sample made up of individual
 hand grab samples vs composite made from samples collected by an automatic
 sampler.
     The t-distributions are a one-parameter family of distributions.
 The distributions vary with the size of the sample and the effect of
 sample size  is evaluated in terms  of degrees of freedom.   The distribution
 is symmetric with the mean equal  to zero, but for finite degrees of
 freedom,  it differs  from the normal distribution in that there is more
area in the tails of the t-distribution and it is more peaked.   As the
degrees of freedom  increase (i.e., more samples), the more closely the
t-distribution resembles the normal distribution.

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                                   -12-
      If the sample size,  n,  is  small  (less  than  30),  the  "t"-test is
 used,  even if the samples are from populations which  depart  "moderately"
 from normal  populations  (1).   The  value  of  "t" is  calculated  from the
 equation
                       t  = |x'-p|'/T
                              s
 Special  tables  list  the value "t"  may reach  for  given probability levels,
 and  the  calculated "t" may be compared with  the  tabular value to  determine
 if the  hypothesis  is  valid.   If  the absolute value of the calculated "t"
 is less  than  the  tabular  value,  the hypothesis is acceptable.
 C.   Two Sample Techniques
     If  two independent random samples,  one from each of two populations
 are  collected, the pooled  technique may  be used to estimate the variance
 in the "t" test.   Since the two  independent random samples came from
                                           2
 the  same wastewater stream, the  variance, a  , and mean, \i, are assumed
 to be the  same for both populations  and the best estimate is obtained by
 pooling  the information contained  in both samples.
     The "t" statistic is  then calculated as follows:
                            - (p- -UP)
                            nl   n2
where Sp is the pooled variance estimator and the degrees of freedom
equal to n  + n  - 2.  Since v  is equal to y,, t =  ] >\  ,  ,
          1     £              I               *      Sp/1    i
                                                        "]    "2
     The calculated value is compared with the tabular value to determine
if the hypothesis that the means are equal is true.  For this study,
a risk level  of 5% was selected (95% confidence level).
     Wieks. S.S.. Elementary Statistical  Analyses.  Princeton University
     Press.  Princeton,  New Jersey,  1958.

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                                   -13-
                    VI.  STATISTICAL ANALYSIS OF DATA
     The  statistical  hypothesis, the mean of the samples collected by
 one  sampling  technique  is equal to the mean of the samples collected by
 either a  similar sampling technique or different sampling method, was
 formulated and evaluated at the 95% confidence level.  The hypothesis
 was  tested using the  "t" distribution, and the pooled sum of squares method
 was  used  for  calculating the statistical estimators.  If the value of "t"
 calculated from the data was less than the tabular value for "t", the
 hypothesis was accepted.  A 2-tail test was used and the a/2 value was
 0.025.  The degrees of  freedom were dependent on sample size.
 A.   Significance of  the Automatic Sampler Probe Position
     1.   July 16-21 Sampling Period - The automatic sampler probes were
 placed in the influent  with the inlets facing upstream, downstream, and
 laterally to  the direction of flow.  Samples were collected for evaluation
 on an individual grab basis and a 6-hour composite basis for 6 days.
 Thirty-six samples were collected for the grab basis evaluation and
 twelve samples were collected for the composite basis evaluation (Table
 VI-1).
     Based on the 6-hour composite samples, the statistical analysis showed
 that the automatic samplers collected equivalent samples for the three
 probe positions for all three parameters.
     The same results were obtained on the grab sample basis evaluation
 for all probe positions for TS and TSS.  However, for the VSS parameter,
 the samples collected with the probes in the upstream and lateral positions
were not equivalent.  The upstream vs downstream and downstream vs lateral
samples were statistically equal.

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                                                 TABLE VI-1

                                       COMPARISON OF SAMPLING METHODS
                                                WWTP INFLUENT
                                              July 16-21, 1974


                           Grab  Samples	h£/=36         6-Hour Composite Samples	N=12
Sampling
Technique
Automatic Sampler
Upstream^/
Downstream
Lateral
Manual Sample
60 minute-'
15 minute
TS (mq/1)
Range
533-741
554-742
548-774
525-730
-
Mean
641
650
660
620
- •
TSS (mq/1)
Range
26-240
24-292
12-324
10-224
-
Mean
126
133
155
108
-
VSS (mq/1)
Ranqe
22-108
18-278
8-314
6-210
-
Mean
110
116
139
94
-
TS (mq/1)
Ranqe
581-965
588-690
580-728
595-653
525-730
Mean
662
642
650
627
620
TSS (mg/1)
Range
92-182
92-180
80-230
86-156
56-174
Mean
118
125
136
112
121
VSS (.mg/11
Ranqe
72-146
70-170
74-212
82-144
34-150
Mean
100
111
123
101 *
103
a/N is the number of samples.
b/Indicates probe inlet position relative to the direction  of flow.
c/Indicates the elapsed time between sample collection.

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                                    -15-
      2.  August 15-22 Sampling Period - Four automatic samplers were
 used to collect the effluent, two probes were placed with the inlet facing
 in the upstream position (UP-1 and UP-2) and two with the inlet facing
 laterally (LAT-1  and LAT-2) to the direction of flow.   The sampling
 duration was 12 hours per day over the 7-day period, however samples were
 composited after  the first  six  hours and after the  second six  hours for
 a  total  of 14 samples per automatic sampler.   Twenty-eight individual
 grab samples were  also collected  at random with each sampler during the
 7  days  for a comparison on  an individual  grab sample basis.
      The following comparisons were made  of  the automatic  samplers  for
 both composite  and the individual  grab  samples  collected over the 12 hour
 daily sampling  period (Table  VI-2).
      a)   UP-1 vs UP-2 and LAT-1 vs  LAT-2  to determine  if two  samplers
          with probes  placed in the  same direction collected equivalent
          samples,  and
      b)   Upstream  position vs  lateral position  to determine the effect
          of  probe  position on  sample collection.
The statistical analysis showed that the samplers were equivalent for all
comparisons.
     The same comparisons, a) and b), were also made using the individual
6-hour composites  collected during the first and second 6-hour intervals
over the 12-hour sampling period  (Table VI-3).  The statistical  analysis
again showed that  samplers were equivalent for all  comparisons.

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                                -16-

                            TABLE  VI-2

                  COMPARISON OF SAMPLING METHODS
                      TOTAL SUSPENDED SOLIDS
                           WWTP EFFLUENT
                        August 15-22, 1974
Grab Samples
                                        =  28  6-Hour Composite  Samples  N=14
Sampling
Technique
Automatic Sampler
Upstream^l-
Upstream-2^/
Lateral-!
Lateral -2
Manual Sample
Special Sampler-
Range
(mq/1)
10-45
10-61
9-66
9-42
6-32
4-39
Mean
(mq/1)
25
26
29
26
21
21
Range
(mq/1
16-48
14-55
8-41
11-59
19-67
9-39
Mean
(mq/1)
28
30
26
30
30
23
a/N is the number of samples.
b/Indicates probe inlet position relative to the  direction  of flow.
c/Indicates either first or second sampler.
(I/Special sampler collected samples from the same depth  as  the automatic
  samplers.  Sampler was manually operated.

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             TABLE VI-3

   COMPARISON OF SAMPLING METHODS
INDIVIDUAL SIX-HOUR COMPOSITE SAMPLES
       TWELVE HOUR STUDY PERIOD
    TOTAL SUSPENDED SOLIDS (mg/1)
            WWTP EFFLUENT
         August 15-22,  1974
Upstream27-!"7 Upstream-227 Lateral-1 Lateral-2 Manual Sample
Ranqe Mean Ranae Mean Ranap Mpan Uanno Moan uanna 	 u^,.
First Six 16-48 27 14-55 30 8-41 23 11-59 26 19-67 32
Hour Period
Second Six 21-39 29 16-50 30 21-37 30 22-40 33 20-37 28
Hour Period
Special Sampler"
Range Mean
9-37 21
15-39 26
a/ Indicates probe inlet position relative to the direction  of flow.
b_/ Indicates either first or second sampler.
£/ Special sampler collected samples from same depth  as  the  automatic  samplers
Note:  Number of samples collected by each method was 7.
                                           Sampler was manually operated.

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                                  -18-
 B.   Comparison of Automatic Sampler vs Manual Sample Method
     1.  July  16-21 Sampling Period - Manual samples were collected
 according to established procedures.  The discrete manual samples were
 collected using a fixed volume dipper (stainless steel) attached to a
 metal pole.  The dipper was rinsed several times in the wastestream
 before the sample was taken.  The samples were placed in 500 ml bottles
 and stored at  4°C.
     The manual sampling technique was compared with the automatic sampling
 technique with the probes placed in the three different positions (Table VI-1).
 Based on the 6-hour composite samples, samples collected manually were
 equal to the samples collected with the automatic samplers.   On an
 individual grab sample basis however, the manual sampling method was
 not equivalent to the automatic sampling method for the lateral and
 downstream probe positions, but was equivalent when the probe was in the
 upstream position.
     2.   July 22-27 Sampling Period - Manual  and automatic sampling
 techniques were compared on the wastewater treatment plant influent and
 effluent (Table VI-4).  The automatic sampler probes were placed in the
 lateral  position only.  Samples were composited over 24 hours.
     On the 24-hour composite basis for the influent samples, the auto-
matic sampling and the manual  sampling methods were equivalent  only for
 the total  solids parameter.   The two sampling techniques were statistically
 equivalent for the effluent samples for TS,  TSS, and VSS.

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                                                  TABLE VI-4

                                        COMPARISON OF SAMPLING METHODS
                                          WWTP INFLUENT AND EFFLUENT
                                               July 22-27, 1974
Sampling
Technique
24-Hour Composite^/
Automatic Sample) —
Manual Sample
Grab Sample-
Automatic Sampler-
Manual Sample


TS (me /l)
Range
573-720
574-640
493-776
446-712
Mean
629
607
649
602
Influent
TSS (mq/1)
Range
106-178
81-120
25-350
7-328
Mean
143
93
138
88


VSS (mq/1)
Range
. 86-158
68-106
21-324
7-274
Mean
122
81
122
78
Effluent
TS (nig/
Range
481-510
442-514
459-539
456-537
1)
Mean
497
498
507
502
TSS (mq
Range N
/I) VSS
ean Ranae
(.man)
Mean
12-26 22 12-30 20
16-139 45 16-105 37
13-52 26 10-42 23
4-42 20 4-42 19
a/ Sample size = 6
b_/ Sampler probe inlet in the lateral  position relative to the direction of flow.
£/ Sample size = 35 for the influent and 36 for the effluent.

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                                     -20-
        On  an  individual  grab  basis,  the two methods were  not equivalent for
   total  suspended  and  volatile  suspended  solids  for'either  the  influent or
   the  effluent  samples.   For  the  total solids  parameter,  the sampling methods
   were equivalent  for  the effluent,  but not for  the influent.
        3.   August  15-22  Sampling  Period -  Based  on the 6-hour composite
   samples,  the  sample  collected with the  automatic samplers with  the probes
   in the upstream  and  lateral positions were equal to the samples collected
   manually  (Table  VI-3).
  ^v/^ On  the individual  grab sample basis, the  automatic sampling and
 /manual sampling  methods were  not equivalent.
^L-—
   C.    Comparison  of Manual Sample Method  and  Special Sampler
        Since  the analysis of  the  data for  the  July studies  showed that the
   automatic samplers were not equivalent  to the  manual sampling method on
   an individual grab sample basis, a special sampler was  fabricated to
   collect  samples  at the  same depth  as the automatic, sampler probes (Section  IV).
   The  special sampler, operated manually,  was  used during August  15-22.
        The  samples collected  by the  manual method were statistically equal
   to the samples collected by the special  sampler for the individual grab
   samples  and the  6-hour  composite samples  (Table VI-2).
   D.    Comparison  of Automatic  Sampler and Special Sampler
        Based  on the 6-hour composite samples,  the automatic sampler
   and  special sampler  collected equivalent samples (Table VI-2).  However,
   the  methods were not equivalent on the  individual grab  sample basis.

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                                   -21-
  E-    Composite Sample Collection Frequency  (July 16-21)
       Manual samples were collected hourly and every 15 minutes for 6
  hours and composited into two separate samples to determine if there was
  a significant difference in sampling frequency (Table VI-1).  The frequency
  of sample collection was insignificant as the samples collected at
  each time interval were equal.
      The samples  collected manually  every 15 minutes and  composited
 after 6 hours  were also  compared with the automatic  sampler 6-hour composited
 samples  which  were collected  hourly.   The former  samples  were  equal
 to  the automatic  sampler composites  for all  three probe positions,  upstream,
.downstream,  and lateral.

-------
                                    -22-
                      VII.  ADDITIONAL  DATA  EVALUATION
 A.    Sampling  Velocities of Automatic  Samplers
      The  relative  intake sampling velocities of the automatic samplers
 were  measured  for  the period July 16-21.  The tubing lengths from the
 probe inlet to the top of the automatic sampler were marked at exactly
 8.0 feet; the  elapsed time between  the tripping of the mechanical trigger,
 releasing the  vacuum, and the sample reaching the 8 foot mark was 1.0
 second.  The vacuum in the bottles  was approximately 21 inches of mercury.
 The lift was 8 feet and the barometric pressures ranged from 24.69 to 24.99
 inches of mercury.
      All of the automatic samplers  had relative velocities of 8 feet per
 second for a total of 34 observations.  Since a greater vacuum can be
 exerted at lower elevations, the velocities may increase.  An increase
 in velocity or vacuum would result  in an increase in the amount of sample
 collected.
 B.   Temperature Control  in the Automatic Sampler (July 16-27)
     The temperature inside the sample bottle containing the first
 sample collected was monitored to determine the rate of temperature
decrease.   The ambient air temperatures ranged from 27°C to 34°C
 (80°F to 93°F) during the study.   The temperatures were monitored for
6 hours during the July 16-21  period when the 6-hour composites  were
collected  and  monitored for 10 hours during the July 22-27 period when
the samples  were composited over  a 24-hour period  (Figures VII-1  and VII-2).

-------
                              -23-

                          FIGURE VII-1

                  AVERAGE TEMPERATURE DECREASE
                    AUTOMATIC SAMPLER BOTTLE
                          WWTP INFLUENT
                        6 HOUR COMPOSITE
                        JULY 16-21, 1974
                                   B--
                                               Not Precooled
      Precooled
CVJ
     Preservation  Temperature
                     I
I
                     2        3         4

                    ELAPSED TIME (HOURS)

-------
                           -24-

                        FIGURE VII-2

                AVERAGE TEMPERATURE DECREASE
                  AUTOMATIC SAMPLER BOTTLES
                        WWTP INFLUENT
                      24 HOUR COMPOSITE
                      JULY 22-27,  1974
                                         Preservation Temperature

                                                I	 I
0
4.6         8

ELAPSED TIME (HOURS)
10
12

-------
                                   -25-
     After collection it required approximately 6 hours for the samples
to reach 4°C from 21°C when precooling of the sampler was not practiced.
Whe precooling was employed, i.e., the automatic samplers were left
overnight in their plywood boxes which were filled with ice,  the
temperature inside the sample bottle containing the first sample collected
dropped from 21°C to 4°C in approximately 3 hours, or one-half the
time required without precooling.
     Temperatures of the first 6 individual samples,  collected hourly,
at the time of composition are listed in Table VII-1.
                                TABLE VII-1
                     TEMPERATURE OF INDIVIDUAL SAMPLES
                             AUTOMATIC SAMPLER
                             JULY 16-21, 1974
Bottle No.
1
2
3
4
5
6
Initial
Temp
°C
21
21
21
21
21
21
Time Elapsed
Since Collection
Hours
5
4
3
2
1
0
Temperature (°C)
When Removed
From Sampler
4.9
7.0
9.5
11.8
16.8
21
Temperature
Decrease, °C
16.1
14
11.5
9.2
4.2
0.0

-------
                                   -26-
                              VIII.   DISCUSSION
      The analytical  techniques  of  the NFIC-D  laboratory were  checked
 on  duplicate  samples during  the study.   The reproducibility of  the  laboratory
 was 98.9%.  The  means of  the samples and standard  deviations  were as
 follows.
                              Mean  (mg/1)     Standard Deviation (mg/1)
 Total  Solids                     526                  8.71
 Total  Suspended  Solids            33                  5.71
 Volatile  Suspended Solids         32                  5.30
 The analytical techniques were  assumed insignificant in the statistical
 analysis  since the reproducibility was very high and the variations of the
 solids were high.  In addition,  the samples used for comparison were analyzed
 at  the same time and  the laboratory techniques would be equivalent.
     The  statistical analysis of the sampling techniques showed that the
 automatic samplers were equivalent to the manual sampling method on a
 composite sample basis, but not on an individual grab sample basis.
Although  the July 22-27 study showed that the automatic and manual  sampling
 techniques were equivalent for only total solids on the raw waste based on
 the 24-hour composite, the previous week's study showed that TS, TSS, and
VSS were equivalent in the 6-hour composite samples.   Since more samples
were collected the first week, using three probe positions, and since
only the lateral  position was evaluated  the second week,  it was concluded
that insufficent samples (6)  were collected and  that the  July 16-21  sampling
period was more representative of the automatic  sampler performance.

-------
                                   -27-
     Although the automatic sampler can be used to collect grab samples
by  installing a clock which activates the trigger mechanism at desired
times,  the practice at NFIC-D is to collect grab samples manually and use
the automatic sampler for composite samples.
     The data show that the samples collected manually were lower in
concentration than the samples collected automatically (Tables VI-1, 2,
and 4)  on an individual grab basis.  However, it cannot be concluded
from this study that the automatic sampler does not collect a representative
sample.  In order to determine whether the automatically collected sample
or the  manually collected sample represents the true conditions of the
wastewater stream requires that the parameters of the wastewater stream be
known.  This type of study necessitates a synthetic wastewater which can
be rigorously controlled.
     Ideally both methods should be compared using "isokinetic" sampling
conditions.   In field application, this is not practical  or achievable
to date.  Manual sampling collects samples without exerting a velocity on
the stream and the sampling velocity of the automatic sampler is dependent
on the vacuum, lift,  and barometric pressure, not on the flow rate.
     The automatic samplers collected equivalent samples for the three
positions on both the composite and grab sample basis, with one exception.
The upstream vs the lateral positions were not equivalent for the VSS para-
meter during July 16-21  on an individual grab sample basis.  However, the
upstream position was statistically equal  to the downstream position and the
downstream position was equal  to the lateral position for VSS.  In the
analysis for VSS,  inorganic material  will  also be volatilized in the muffle

-------
                                      -28-
 furnace  along  with  the  organic matter.  The VSS are also more variable
 in  the influent  than  in the effluent.  Therefore it was concluded that
 VSS is not  a satisfactory  parameter  for the statistical comparison.  The
 possibility exists  that the VSS  for  the upstream position may have been
 equivalent  to  the lateral  position and statistically rejected (value of
 "t"  calculated was  2.04 and the  tabular value was 1.997), especially since
 the upstream vs  downstream and downstream vs lateral were equivalent.
 The possibility  also  exists of accepting a hypothesis when it is false.
 However, the level  of significance is selected to minimize the latter
 possibility.   In this study, the level of significance, a, was 0.05, and
 the  probability  is  much  higher that a true hypothesis will be rejected
 than a false hypothesis accepted. Since the August 15-22 data showed that
 the  probe locations,  upstream vs lateral, were equivalent, and due to the
 other factors cited above, it was concluded that all probe locations
 collected statistically  equivalent samples.
     Since all  probe  positions collect equivalent samples on both a composite
 and  grab sample basis,  field application is not limited due to the configuration
 of the sampling site or  height of the lift.  Also,  the probe can be positioned
 laterally or downstream  position in the flow to prevent clogging or freezing
 of the inlet.
     Sample collection frequency, on a composite basis, over a 6-hour
 period was not  significant as the samples collected  every 15 minutes
and composited  were equivalent to samples collected  hourly and composited.
The application of  sampling more frequently is recommended when  the
wastewater stream is highly variable in strength.   However,  the  length
of sampling period would then be limited  by the number of sample bottles.

-------
                                    -29-
     The monitoring of temperature in the sample bottles clearly shows
that the bottles should be precooled before sampling begins.  NFIC-D
is presently modifying the metal sampler case.  A non-insulated case
(thin walled, sheet metal) will be used when ambient air temperatures
are above freezing.  This casing will  be used in the plywood box and
ice packed between the metal  and insulated plywood walls.  It is
expected that the temperature inside the sample bottles will decrease
at a greater rate,  thus enhancing sample preservation.

-------
APPENDICES

-------
                SONFORD PRODUCTS  CORPORATION
 2 US HAND TOWK*                                                MINNCAPOLI9 ». MINNESOTA
                           SERCO Automatic Sampler
                               Technical Report


     The SERCO Automatic  Sampler operates on the principle of Boyle's Gas Law.
The sample is collected in  the sampling container by  a  driving force caused by
the difference in pressure  in the evacuated container and the atmospheric
pressure.

     The size of sample collected depends on the atmospheric pressure, the level
of evacuation, the lift,  and the volume of the sampling container.  The standard
SERCO Sampler, Model NW-3,  has a 16 02. sampling container and three foot lift.


                               Sample Volume

     The volume of sample to expect at various conditions is shown in Figure 1
and 2, as well as in the  table in the brochure.

     In general,  the larger the volume of sample collected, the more representative
it will be.   According  to Standard Methods for the Examination of Water and Waste
Water, each  individual  waste water sample collected for compositing should be at
least 120 milliliters and the portions should be collected each hour—in some cases
each half hour or even  every 5 minutes—and mixed at  the end of the sampling period,
or combined  in a single bottle as collected.   This minimum is noted on the two
figures and  is recommended  as the minimum volume of waste water to collect.
Smaller volumes can be  considered for special applications, however.

     Larger  sample volumes will be necessary for stream sampling because each
individual sample will  be analyzed.   It is expected that about one liter (1000
milliliters)  would normally be desired.

     The volume of sample needed for other automatic  samplinq applications, such
as river sediment studies and chemical processing control would be dictated by the
specific needs of the applications.

-------
                         SONFORD PRODUCTS CORPORATION
                                2355 Rand Tower
                          Minneapolis, Minnesota 55402
                                 SAMPLING DATA

     The following laboratory and field tests represent comparative analytical
data of samples taken at the same time by the SERCO Automatic Sampler and manually
for several different types of waste water.  The comparison of sampler data with
data for manually collected samples does not mean that it is assumed that manual
sampling is more accurate.  In fact, the samples collected with the Sampler may
be more representative of conditions in the flowing stream.  However, manual
collection of samples is common in the waste water field and these studies have
been made to demonstrate that the SERCO Automatic Sampler can collect at least
as representative a sample as would be"collected manually.
I.   ACTIVATED SLUDGE

     Several samples of activated sludge were collected directly from an aeration
tank to determine the effect of the air bubbles in the liquid on the sampler, as
well as its ability to collect the solids.  The results of the analysis are as
follows:


                                                  Suspended Solids,  mg/1
     Trial No.                 SERCO Automatic Sampler                Manual

         1                              2585                           2585
         2                              2650                           2735
         3                              2790                           2880
         4                              2950                           2835
      Average                           2744                           2759


Results of tests on concentrated activated sludge is as follows:


                                                  Suspended Solids,  mg/1
     Trial No.
         1
         2
         3
         4
      Average
ERCO AUTOMATIC Sampler
17,490
16,750
17,530
17,360
17,540
Manual
18,040
17,410
18,960
17,350
17,940
                                       -2-

-------
                           SONFORD PRODUCTS CORPORATION
                                  2355 Rand Tower
                           Minneapolis, Minnesota 55402
 II.  DOMESTIC WASTE
 Laboratory Test
      Fresh raw domestic waste was brought to the laboratory for this  study.   While
 the waste was being thoroughly mixed,  nine samples  were collected from the waste
 sample container with the SERCO Automatic Sampler and then were collected  manually
 with 250 ml french-square bottles.   The samples  were collected  alternately;  that
 :s, a sample was collected with the Sampler,  then a sample was  collected manually,
 and so on.  The raw waste was thoroughly mixed using two plunger type  manual  mixers.
 These samples were analyzed for suspended solids and the data is as follows:

                                                  Suspended Solids, mg/1
      Trial No.                  SERCO Automatic Sampler                 Manual
          1                           *    270                           ~286
          2                               264                            270
          3                               268                            270
          4                               260                            244
          5                               262                            262
          6                               252                            248
          7                               254                            274
          8                               238                            228
          9                               258                            240
                                          238-270                        228-286
      Average                            258.3                         258.0

Field Studies .

     A SERCO Automatic Sampler was taken to a municipal waste treatment plant and
24 individual samples of the raw sewage were collected using the Sampler and 24
samples were collected manually at the same time.  These samples were collected
over a period of about 30 minutes.  The two sets of 24 samples were composited
separately and analyzed.  The laboratory results are as follows:
Analysis                          SERCO Automatic Sampler
Manual
5-day BOD, mg/1                               72                         72
Total solids, mg/1                          2230                       2270
Total volatile solids, mg/1                  510                        575
Suspended solids, mg/1                       112                        113
Suspended volatile solids,  mg/1              103                        104
P"                                             7.70                       7.70

     The above data demonstrates the ability of the SERCO Automatic Sampler to
collect a representative sample of raw domestic sewage.

-------
                          SONFORD PRODUCTS CORPORATION
                                 2355 Rand Tower
                          Minneapolis, Minnesota 55402
III.  MEAT PACKING WASTE

     Composited samples of meat packing waste were collected using the SERCO
Automatic Sampler and by manual procedures over the same 24 hour period.  A total
of 24 individual samples were collected at one hour intervals with the Sampler.
The manual samples were collected at 30 minute intervals.  The Sampler samples
were collected from the influent channel, ahead of the Parshall flume.  The manual
samples were collected after the flume, as the waste water discharges into the
wetwell.  However, the same waste flow was collected at each location.  The five
day BOD results of the composited samples are as follows:
Analysis

5-day BOD, mg/1
PH
SERCO Automatic Sampler

           2095
              7.10
Manual

 2095
    7.10
     Waste water samples were collected with the Sampler and manually from a com-
bined domestic waste and meat packing waste.  The meat packing waste constitutes
about 90% of the waste water volume.  The samples were collected manually and with
the Sampler at exactly the same time from the influent channel to the primary
settling tank.  The analysis of the related samples are as follows:
                  SAMPLER
                                                         MANUAL
Sample
No.
1
2
3
4
5
6
7
8
Average
5-day BOD
mg/1
3280
2790
•—
—
1900
—
2050
—
2505
Total Solids
mg/1
6170
5590
3590
3790
3950
3820
4370
4330
4450
                                               5-day BOD
                                                  mg/1
                                                  3300
                                                  2670
                                    Total Solids
                                        mg/1
                                        6330
                                        5590
                                        3740
                                        3560
                                        3730
                                        3810
                                        4370
                                        4440
                                        4446
     Based on previous analytical data, the suspended solids concentration of the
above sample would be expected to be 1000-1500 mg/1.   The BOD and solids data
indicates that the SERCO Automatic Sampler will collect representative samples of
meat packing waste with high concentrations of organic solids.   The total solids
data showed almost identical analytical results and the BOD data was within the
limits of accuracy for the test.  It should be noted also, that the BOD of the
manual samples were slightly lower.
                                       -4-

-------
                           SONFORD PRODUCTS CORPORATION
                                 2355 Rand Tower
                           Minneapolis, Minnesota 55402
 IV.   PAPER MILL WASTE

      Samples of paper mill waste water were collected both manually and with the
 SERCO Automatic Sampler at the same time.  The analysis of samples of the screened
 wood  room  effluent are as follows:

                                         Analysis for Total Solids, mg/1
      Trial No.                SERCO Automatic Sampler                 Manual

         1
         2
         3
       Average

 The analysis of waste water from the Kraft Mill process is as follows:

                         Analysis for Total Solids, mg/1
           SERCO Automatic Sampler                  Manual
                      710                             725
     The suspended solids concentration for the screened wood room effluent was
about 2000 mg/1 and for the Kraft Mill waste was about 100 mg/1.   The sampling
station used for the wood room effluent was located very close to the screens,
making it difficult to obtain a uniform sample, which accounts for the variations
in the solids concentration for both methods.  The average concentration of solids
for the wood roof effluent was higher in the samples taken with the Sampler because
they were collected near the bottom of the channel, while the manual samples were
collected near mid-depth.  It is difficult to say which of the sampling methods is
more representative of stream conditions.   However, this test does clearly show that
the SERCO Automatic Sampler can collect satisfactory samples of paper mill waste
water with suspended solids concentrations of at least 2000 mg/1.
                                       -5-

-------















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-------
     3000
           3750  ml- (1
           gallon)
SERCO AUTOMATIC
Sample Size
llection Co
    SAMPLER
with Variou
itainer
                                                                                                      Volu les
     2500
           3000 ml
    2000
•0
t—
ID
2000
    1500
 NOTE:  The
       were
       Atmo
       Gage
       Othe
ollowing as
made for ca
pheric pres
Vacuum--26
 physical c
umptions
culation:
ure—30 in.
n. Hg.
inditions
                                                                                                            Hg.
    1000
                                                                                         for
                                                                                    odel NW-3
          1000 ml
     500
                                                            \
          16 oz.
                                                                                  20 ml Rccomnended Minim :m Sample
                                              Lift in Fe«

-------
 SERCO  AUTOMATIC SAMPLER

 Assembly for Model NW-3

 1.  The SERCO Automatic Sampler {Fig. 1) is shipped ready for operation except for placing the bottles in
    the trays. Be certain the numbers on the bottles correspond both to the tray numbers and the numbers
    on e?ch switch.

 2.  Water may be visible in some of the bottles and tubes when the  sampler is received. This is simply
    residual water left  in  the sampler after  being  tested  prior to shipment. The water used is City of
    Minneapolis tap water.

 3.  To  Remove Arbor Hub — See Figures 2 and 3
    a. Loosen and remove Knurled Screw (left hand thread).
    LJ. R.-rnove Tripper Arm.
    c. L dusen alien head set screw (B) on side of Arbor Hub.
    d. Turn alien head screw (A)  located in,Arbor  Hub below Knurled Screw. This will force hub off the
      tapered clock arbor.

 4.  To Install Arbor Hub — See Figures 2 and 3
    a. Unscrew alien head screws (A) and (B) a few turns.
    b. Place hub on clock arbor and tap gently to set in place.
    c. Turn alien head screw (A) into hub just until it is in contact with top of clock arbor.
   d. Tighten alien head screw (B) at side of Arbor  Hub.

 5. To Install Gear Head — See Figure 4
    a. Remove Arbor Hub (See mstructions)
   b. Place Gear-Head over arbor and rotate until ends of Gear Head are under  the heads of the posts
      provided in top or clock nousmg.
   c. Install auxiliary strap to hold gear head in place.

 Routine Operating Instructions for Model NW-3

See Figure 1 and 2

 1. Be certain all bottles and tubing are clean.

2. Wind clock used to actuate switches. When using the clock in  a room where the noise level is high and
   where the tick of the clock may not be heard, the motion of the main spring may be observed through
   the especially provided hole in  the Switch Plate. This assures the user that the clock  is running.

3. Set rubber stoppers securely in the 24 bottles.

4. Place Vacuum Head over Sampling Head and hold in place until it is vacuum sealed.

-------
  SERCO  AUTOMATIC SAMPLER

  5.  Evacuate the system through the hose connection on the Vacuum Head using a vacuum source (such as a
     vacuum  pump, vacuum system, or ejector). This can be done in the lab or in the field if a source  of
     vacuum  or power is available. A vacuum is assured in each bottle if each of the rubber tubes is collapsed
     (flattened.) The necessary vacuum to  be  maintained in the bottles in order to obtain a properly sized
     sample will vary with the conditions  under which the sampler is used. See Table 1 for variation of
     sample size with sampling conditions.

  6.  Seal off each bottle  by setting the switches on the Switch Plate.

  7.  Release the Vacuum Head and check to see if all bottles are evacuated and holding a vacuum. This may
     be easily done  by observing the rubber tubes to see that each remains collapsed. As a precaution, the
     tubes to  each bottle should be checked again at the installation site to be assured that bottles are still
     evacuated.

  8.  Set Tripping Arm to desired starting position. Be certain that the hole in the Tripping Arm fits snugly
     over the  raised section at the top of the Arbor Hub and that the Knurled Screw is tightened securely.  If
     Tripping. Arm is not securely attached to Arbor Hub it will turn and not be capable of providing the
     torque to operate switches.
     Caution:  Do  not  set tripping  Arm until  you want to start sampling since the clock continues to run
     once it is started.

  9.  If you wish to cool  the samples, place the ice containers in bottom of sampler by centering them in the
     painted'square in sampler bottom.

10.  Lower rack into outer case.

11.  Transport the sampler to point  of  use. Hang Sampling Head in the flow, and  be  sure it is-low enough
    to obtain-a-sample when the flow level is at the minimum elevation.

12.  Record the bottle number of the first sample and the time sampling is started.

13. After  sampling period, bottles may be  removed and covered with caps and transported to a  laboratory
    for analysis. Samples may be composited according to flow  records and any one sample may be run
    individually. (Sample bottles may be left in sampler and entire unit transported to lab.)

14. Back flush each line with water  (preferably  hot, if available) from the rubber stopper end, and allow to
    dry  for future use.  Back flushing is best  done with a piece of pipe or plastic tubing  approximately
     1/2-inch in diameter. With one end of this tube connected to a hose from the faucet, the other end may
    be pressed firmly against the rubber stopper to  force water back through the' sampling line. Also, the
    solids should be flushed from under Sampling Head Shroud.

-------
      Lifting
      Handle
Twenty-four clear
flexible vinyl sampling
lines — '/. inch I.D.
                                                     Twenty-four
                                                     rubber sampling
                                                     lines. '/• inch 1.0.
                                                   Spring-driven
                                                   timing motor
                                                   with tripper-arm
          Double-Hinged
          cover
                                                 Polystyrene
                                                 rigid insulation
                                                                                Stucco aluminum
                                                                                outer case
                                                                       VIEW OF SAMPLER
                                                                           IN POSITION
                                                                             FOR  USE
                                                               Stainless
                                                               steel sampling
                                                               head
R ubber stoppers
in twenty-four
16oz. French
square glass
sample bottles.
Bott les are
numbered.
VIEW  OF SAMPLER
REMOVED  FROM CASE:  Model  NW-3
                            Bottles have been
                            removed to show core
                            space used to hold
                            ice for cooling
                            samples.
                 Figure 1
                                           Table 1

              APPROXIMATE  VARIATION  OF SAMPLE  SIZE
                      WITH  CONDITIONS  OF  SAMPLING
SAMPLE VOLUME
Milliliters
VACUUM GAGE
READING
IN. OF MERCURY
LIFT
3 FT.
LIFT
8 FT.
LIFT
13 FT.
26
370



282



153



24
333
363
400

237
272
310

97
128
167

22
295
323
356
395
193
222
257
300
43
67
97
137
20
259
283
312
347
149
173
204
240

6
27
56
18
221
243
268
300
105
125
150
180




16
184
203
222
252
61
77
97
120




14
147
163
178
205
27
28
43
60




12
no
123
134
157








10
74
83
90
110








8
36
43
46
62








ATMOSPHERIC
PRESSURE
IN. OF
MERCURY
30
28
26
24
30
28
26
24
30
28
26
24
            The size of the sample varies with the lift, the length
            and size of the sampling tube, the size of the sample
            bottle, the atmospheric pressure, and the vacuum held
            in the bottle. The values in the above table have been
            obtained with the equipment furnished with Serco Auto-
            matic Sampler Model NW-3.
  SAMPLE
   TUBE

 LIQUID
SURFACE
                                                                          SAMPLE
                                                                          BOTTLE

-------
                                     DETAILS OF SWITCH R
                                PLATE  FOR  MODEL  NW-3
 Figure 2
                  Knurled screw
                  holding tripper
                  arm
Nut for
winding
clock
                                                     Switch with
                                                     sampling line
                                                     sealed
                                                                            Aluminum plate
                                                         Spring-driven
                                                         timing motor
                                                         rotating
                                                         once each
                                                         24 hours
                                                                              Switch with
                                                                              sampling
                                                                              line open
                                                                            Hole to observe
                                                                            timing motor
                                                                            operation
                               PLAN  VIEW  OF  SWITCH  PLATE
                                 (Shown With Tubes Cut  Off)
           Figure 4
                                            TRIPPER ARM
                                Gear heads are
                                available to earily
                                change the interval
                                of sampling from
                                hourly to every 30
                                minutes or
                                whatever is
                                required.
                        ALLEN-HEAD
                        SCREW (A) FOR
                        USE !N REMOVAL
                        OF HUB (RIGHT-
                        HAND THREAD)
                                            TAPERED	
                                            CLOCK ARBOR
PLAN VIEW OF  GEAR HEAD
  INSTALLED ON  CLOCK
                                               Figure 3
                                                                        KNURLED SCREW
                                                                        (LEFT-HAND THREAD)
                                                                     ARBOR HUB
ALLEN-HEAD SCREW (B)
(RIGHT-HAND THREAD)
                                                                             - CLOCK

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