DESIGNING EXTENDED AERATION UNITS FOR OPERATION IN COLD REGIONS
by
H. J. Coutts, P.E.
Chemical Engineer
U.S. E.P.A. Alaska Water Laboratory
College, Alaska
Presented as Part of A
COLD CLIMATE WASTEWATER TREATMENT DESIGN SEMINAR
Sponsored by
The U.S. E.P.A. - Technology Transfer Program
Anchorage, Alaska
-------
DESIGNING EXTENDED AERATION UNITS FOR OPERATION IN COLD REGIONS
H. J. CouttS, F.E.
I. Background
A. Extended Aeration In Alaska
1. Smaller (less than 0.05 MGD) Units - most units put into lower 48
environment by housing.
Lower 48 performance of package plants was summarized by the USPHS
in 1960 (1).
The National Sanitation Foundation has developed criteria for
evaluating the performance of package extended aeration units (2).
The US Army (CRREL) has built a small low cost do-it-yourself
(1700 gal/day) unit which is undergoing testing (3).
2. Larger 0.02 MGD through 1+ MGD - for larger units (0.05+ MGD) the
cost of housing the entire unit becomes expensive. With proper
design the aeration basins can be left exposed to the environment.
This talk will point out some design and operation constraints
imposed by the subarctic. A conceptual design for a 1/2 MGD
plant is also presented.
B. Application of Processes
1. Economics, Effluent Quality - construction and operating costs are
usually higher than for aerated lagoons; but with proper sludge
handling higher performance can be generally obtained by extended
aeration units.
2. Feed Characteristics - although the process will tolerate biological
poisons (4, 5, 6) the process information presented here will be
limited to domestic sewage with a BOD range from 150 to 250 ppm.
II. Operating Units from which Empirical Design Criteria is Developed
A. College Utilities (CU), a 1/2 MGD oxidation ditch
Description of plant (Figure 1)
B. AAC-AWL (EAFB) Pilot Extended Aeration Units - approx. 0.1 MGD
Description of units (Figures 2, 3, 4, and 5)
C. AWL Bench Scale Cold Room - 10± gal. units (Figures 6 and 7)
smaller
housed
units
larger
units
oxid.
ditch
conven-
tional
bench
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III. Process Performance is Proof that It Can Be Done
effect
eff.
solids
A. Temperature has little effect for long detention (1+ day) system, but
a significant effect for a shorter detention, more heavily loaded system.
1. CU Performance (Table 1)
2. EAFB Performance (Table 2)
B. Solids control (wasting) more important
EAFB and CU - all data (Table 3)
IV.
solids
prdctn.
food
mass
food
volume
solids
level
clarifier
hydraulic
load
Process Design Considerations
A. Facilities for excess sludge wastage must be incorporated
1. Facilities designed to handle up to 0.6 #MLSS/#B0D applied below
10°C; if unit will be operated at detention down to 1/2 day or
less. Lower 48 criteria is approximately 0.5 #MLSS/#B0D. (Figure
8 - Growth Vs. MLSS). Excess sludge facilities should be capable
of disposing up to 5% of the return sludge flow on a continuous
basis.
2. If effluent polishing lagoon is used in lieu, size for 2-day
detention minimum.
B. Loadings
1. Limit organic below 0.1 #B0D/#MLSS-day for low temperatures.
Bulking sludge (dispersed floe) encountered above 0.1.
Figure 9 - Loading Vs. % BOD Removal.
2. Hold corresponding volumetric loading below 10 #B0D/1000 CF-day
when mixed liquor temperatures go below 10°C.
Figure 10 - Volume % @ 1/2 Hr. Vs. D.T.
3. MLSS should be held between 1500 and 4000+ ppm - no cushion
if below 1500.
Figure 11 - Startup of % BOD R Vs. MLSS (NSF)
Don't assume for mixed liquor temperatures below 7°C that MLSS
will be above 4000 ppm. Most existing Alaskan units don't exceed
3500 ppm P low temperatures.
Upper operating value is limited by what container will hold.
Sludge return flow and mixing problems can be encountered when
the mixed liquor becomes as thick as mud.
4. Average clarifier overflow rates should be held below 0.3 gpm/ft2
Peak overflow rate of 0.5 gpm/ft^
Figure 12 - Effluent SS Vs. Overflow
Figure 13 - Settling Rate Vs. MLSS @ 1/2 Day Detention (EAFB)
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V. Project Considerations
A. Flow Equalization
pi 1. Peak flow could be more than 3 times average.
Watch institutions, construction camps, military installations, etc.
level-flow 2. Consider varying operating depth to absorb peaks by using constant
control head (floating) weirs. A floating weir is designed such that the
crest of the weir floats up and down with rising (falling) water
level (Figure 14). Floating weirs are used in European treatment
plants and in Florida for controlling canal levels. A fixed
vertically slotted pipe (sides of weir) with a sleeve (crest of
weir) attached to a float ring has been used at EAFB to average
out peaks. Effluent collector pipes can then be submerged.
B. Heat Transfer is the Main Consideration
clarifier
housing
1. The clarifier should be housed in a lighted heatable enclosure
with minimum 8' work/walkways on three sides or over surface.
At EAFB the prefab 2" urethane panel A-frame cost approx. $6/ft^.
Consider construction of clarifier adjacent to aeration basin with
a common wall. Mounting the clarifier within the aeration basin
could save earthwork.
piping
protection
accessory
protection
4.
All piping-including air lines should be buried and heat traced
to protect against freezing.
Double heat trace with nichrome coaxial or MI cables. Check for
continuity and shorts before backfilling. MI cables are usually
heavier duty but require more carefull installation. Buried
thermostats are the only type that seem to fail.
Alternate: Circulate heated low freeze point fluids in small
pipes parallel to pipe wanting to protect. Don't put heat
sources in pipes. Object is to keep soil around pipes above
freezing. Flowing fluid in pipe will carry away heat.
The control lab, process monitoring instruments and all moving
equipment should be housed in a lighted heated enclosure large
enough to not limit access for monitoring, maintenance or
operation.
Don't construct any tanks on or in permafrost unless you are
willing to provide thermal protection for the permafrost.
5. Maximum winter detention for aeration basins in Interior Alaska:
Detention
1 day
2 day
4 day
Feed Temperature
5°C
10°C
20°C
It is not impossible to operate with longer detention but surface
freezing problems will increase.
Watch out for winter startup of new plant which may be way underloaded.
Deep aeration tanks (15+ ft) are much preferred since they have much
less exposed (freezable) surface pen.volume.
Exposed basins limit their heat loss by growing an ice cover.
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Aeration and Aeration Basins
1. Surface aerators will cause excessive ice buildup on themselves
and exposed supporting structures (7).
They are difficult to service. Ever crawl over a glaciated walkv/ay
or paddle a raft in your down suit to grease the aerator's bearings?
2. Oxidation ditch rotor assemblies need to be housed for ease of
maintenance and freeze protection during shutdown.
At the College oxidation ditch mudflaps were used during the first
year or so to restrict sheet ice from freezing onto the rotors.
Level fluctuations (i.e., too much submergence) has been responsible
for chewing up gear boxes.
3. Submerged aerators; best choice.
The minimum air rate for oxygen transfer into 5°C, 2000 ppm SS
mixed liquor was found to be 1000 SCF/#B0D at the EAFB units. The
transfer efficiency (including surface effects) with the open type
aerators (monospargers and shearboxes, both underloaded) was
approx. 4% @11 ft depth and 1/2 ppm D.0.
The oxygen requirement is much lower at the lower temperatures
because there is less nitrification and wet oxidation (endogenous
respiration). The warmer temperature values of 1500-2000 SCF/#B0D
should be used (8, 9).
Several investigators have reported that the "spiral-flow" aeration
(basins) pattern exhibits poor oxygen transfer (10,11).
For weaker sewage mixing may require more air than does oxygen
transfer. For adequate mixing in vertical wall tanks with 11 ft.
aerator submergence, air requirement is about 1.5-2.0 SCFM/1000 gal.
The EAFB units (primary effluent feed) have operated with air inputs
as low as 0.7 SCFM/1000 gal. but some MLSS did settle out.
Use open aerators and avoid need for knee joint pipe. Make all
process piping penetrations thru aeration basin wall at least 2 ft.
below low operating level and heat trace.
4. Compressors
Use 3 - 50% (or 5-25%, etc.) compressors for D.0. control.
Low operating D.0. (0.3 to 1 at less than 10°C) appears to give
lower SVIs and less floatables on clarifiers. Time cycling larger
compressors may shorten their life.
Positive displacement blowers (gas pumps) are very noisy and
should be installed in separate sound proof rooms.
5. Aeration Basin
The aeration basin should be constructed with a center dividing wall
so the plant can be operating with one aeration cell drained during
the summer for removal of rocks, eyeglasses, tools and beer cans.
Also aerators can be checked.
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6. Materials
Air entrained (anti-spall) concrete is satisfactory for wall con-
struction. Don't consider the soil as being capable of absorbing
vertical sidawall hydrostatic pressure.
Sloped sidewalls would reduce construction cost and will exhibit less
depth changes in absorbing flow fluctuations. Minimum slope is 1:2.
Clarification
1. Avoid the use of moving parts for sludge collection. Hoppers with
60° walls are satisfactory. Allow some separation room; use 12 ft.
minimum depth to give operator a chance to change conditions before
sludge passes over weir. Eye, et al., (12) reports that the most
frequent operating problems have been with activated sludge col-
lection and return.
At EAFB when using raw sewage as feed, activated sludge has plugged •
1-1/2" 0 suction holes in return manifolds. They were unplugged by
giving the air lifts more air. 2" 0 suction holes would probably
not have plugged.
8' long hopper bottoms with 4" pipe suction manifolds (1-1/2" 0 holes
@ 12" o.c.) have worked satisfactorily with primary effluent as feed.
2. Air lifts for sludge return are very reliable (no moving parts or
valves)and are much easier to maintain.
Sludge return rates from 15 to 300% of feed are easily obtainable
by use of solenoid and air throttling valves and timers.
EAFB sludge return rate approx. 100-300% of feed.
CD sludge return rate approx. 5-20% of feed.
3. Expect many floatables, use control baffles, skimmers and surface
rakes. Don't clutter up clarifier surface with unnecessary
paraphenalia.
4. Tube Settlers
The performance of the horizontal vs. upflow w/tubes clarifier is
about comparable.
Installation of tubes makes it more difficult to observe the
condition and level of the sludge blanket.
Tubes should not be installed without backwash and/or sparging
facilities. At EAFB use of 2/3 of the tubes to backwash the other
1/3 has been satisfactory.
The best use for tubes would be for effluent polishing, i.e. removing
residual effluent SS.
A floating tube settler as clarifier appears to have worked well in
a small CRREL wood stave tank extended aeration unit (3).
Chiorination
1. Use U.S. EPA specs (13). Consider using hopper dead zones as contact
chamber.
2. Hypochlorator pumps require much maintenance, use CI2 gas if possible.
3. Watch out for chlorine hydrate (chlorine ice - Cl2'8H20) which forms
at 49°F. It hasn't been a problem yet because 49 F carrying water
-------
4. Vapor Pressure of CI2 is 15 psi at -35°C. Don't expect CI2 to
flow froni a CI2 cylinder that has been setting outside at -40°.
5. The U.S. EPA (14), VJPCFv(15) suppliers;(16, 17) and interested
parties (18, 19) can supply detailed instruction on chlorine
handling.
Process Monitoring, Operator Training, and Control Tests
1. Instrumentation
It seems like fewer and fewer of the electronic instruments work
properly after the warranty period is up. The attendance of a good
electronics tech or instrument man is in many cases necessary to
keep the instruments operating.
A maintenance contract for the instrumentation should be included
as part of the operating cost.
Use all the fancy instruments you want but also include simple
indicators such as a counter on the final lift station pump and
calibrate its sump. Provide portable dp cells.
2. Operators
If there are no plans to provide for a trained operator at each new
plant then it is a waste of money to buy or build the plant. Other
investigators state that the extended aeration process shouldn't be
used unless the plant will be properly operated and maintained (20).
The Water Pollution Control Federation has recently put together an
extended aeration package plant training package (21).
The State of Alaska also prints an Operating Manual for small
extended aeration treatment plants (22).
3. Process parameter analysis
Monitoring in-out BOD too slow for process control - pollution
control authorities may require it. Mixed liquor D.O., settling
rate and effluent turbidity are the most important parameters.
EPA puts out a sound-slide show on control tests for activated
sludge (appendix). The only lab equipment required for these
tests is 2-1. beakers (settlometers), a centrifuge, and a good D.O.
meter. A lab centrifuge is usually less delicate and requires less
-------
OXIDATION DITCH, COLLEGE, ALASKA
PERFORMANCE DATA
(1)
Avg.
Ditch Liquid Avg.
Detn. Temp. % BOD MLSS Overflow Effluent
Date: Mo/Yr Days °C Removal Avg. % Volatile gal/ft -day SS
10/67-3/68 2.0± 10-11 92 1700 - 240 21
(2)4/69-12/69 - 11-20 91(S) 2800 - - 18
(3)l/71-3/71 1.0* 8-14 80(A»5) 1600 71 470 35(4)
(3)5/71-7/71 1.8t 16-20 88(4'5) 4500(6) 50 260 18(4)
^ Grube, G. A. Ms. Thesis, University of Alaska, 1968
^ Institute of Water Resources, University of Alaska
^ Ranganathan, K. R. Ms. Thesis, University of Alaska, 1971
^ Data not included when effluent SS were above 100 ppm
^ Septic tank sludge not included in influent BOD
Solids in quiescent sections of ditch have exceeded 20,000 ppm
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AAC - AWL - EAFB
PILOT EXTENDED AERATION UNITS
PERFORMANCE DATA
Excluding Effluent SS Over lOOppm
Clarifier Average Liquid % BOD Average Average
Flow Aer. Tank Temp. Removal MLSS % Vol- Overflow Effluent
Pattern Detn. Days °C Average Avg. atile gal/ft2-day SS
Hz
0)
0.42
12-19
75
2800
76
450
27
Hz
(2)
0.65
7-12
78
2300
84
690
27
Hz
(2)
0.43
2-7
45
1900
74
380
43
Up
(1) 0.43
12-19
77
3400
83
550
Up
(2) 0.61
7-12
80
1900
80
660
Up
(2,3) 0.41
2-7
55
2500
66
410
(1) From 1/71 to 11/71, feed was raw sewage; average BOD = 110.
(2) From 11/71 through 2/72, feed was primary effluent; average BOD = 170.
(3) One inch air line to 6 inch sludge return air lift froze for two weeks
out of seven week data period.
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SUBARCTIC ALASKA EXTENDED AERATION UNITS
PERFORMANCE DATA
Locati on
Clarifier
Flow
Pattern
Average
Aer. Tank
Detn. Days
Liquid
Temp.
°C
% BOD
Removal
Average
Loading
BOD/
MLSS-day
MLSS
Avg.
% Vol-
ati 1 e
Average
Overflow
gal/ft2-day
Average
Effluent
SS
EAFB
Hz
(1)
0.42
12-19
75
0.11
2800
76
450
47
EAFB
Hz
(2)
0.65
7-12
74
0.12
2300
84
700
63
EAFB
Hz
(2)
0.43
2-7
9
0.17
1750
77
390
143
EAFB
Up
(1)
0.43
12-19
76
0.12
3400
83
560
51
EAFB
Up
(2)
0.61
7-12
80
0.14
2000
80
670
101
EAFB
Up
(2,3)
0.41
2-7
<0
0.41
1500
73
370
136
Col 1ege
Oxidation
Ditch
Circ.
Up
.(4)
1.4+0.4
8-20
35
0.05
3000
60
370
398
(1) From 1/71 to
11/71
, feed was
raw sewage
; average
BOD = 110.
(2) From 11/71 through 2/72, feed was primary effluent; average BOD s 170.
(3) One inch air line to 6 inch sludge return air lift froze for two weeks out of seven week data period.
(4) Ranganathan, K. R. Ms. Thesis, University of Alaska, 1971. Septic tank sludge not included in
influent BOD. Solids in quiescent sections of ditch have exceeded 20,000 ppm.
-------
DIMENSIONS
Water Depth - 4.5-6 ft.
Ditch Volume - 333,000 gal.
Clarifier Volume - 54,000 gal
89 RPM (? 30 HP
<- 30'—>
%
in
o
f>
out
College Utilities
Oxidation Ditch
Capacity ^ 1/2 MGD
College, Alaska
On Stream
Summer 1965
-------
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Collection and Return
14'
-------
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AERATION CELL WITH TUBE SETTLER CLARIFIER
PROCESS FLOW SECTION
Wastage
Clear Effluent
Complete
Sewage
Feed
Mix
Return Sludge
AERATION
CELL
HORIZONTAL
FLOW BASIN
(Clari fier)
BLOCK FLOW
UPFLOW EXTENDED AERATION UNIT
-------
Air to
Aerators
and Air-
lift Pumps
Sew-
age
Feed
SL
s* Return
SIudge
COMPLETE MIX
AERATION CELL
J
Air Lift Pumps
"Aerators
II Returning Sludge
Effluent Collection
>-
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HORIZONTAL FLOW
CLARIFIER
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_ o o
v
Effluent Line
AERATION CELL WITH HORIZONTAL FLOW CLARIFIER
PROCESS FLOW SECTION
Wastage
Clear Effluent
Complete Mix
Sewage
Feed
Return Sludge
AERATION
CELL
HORIZONTAL
FLOW BASIN
(Clarifier)
BLOCK FLOW
HORIZONTAL EXTENDED AERATION UNIT
-------
mxi„g Q
Pump
J
To Aeration Chamber
£T1
Effluent
Pump
(Hoi ter),
Refnget
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Perfusic
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60 Gal.
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Air Supply-
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0
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Recycle
Pump
(Hoiter)
Effluent
Overflow
Line
Y
Effluent
Tanks
Reactor
Plexiglas
Reactor
Side View
AWL REACTOR
8.9 GALLON
SCHEMATIC OF APPARATUS
-------
Bypass channel for circulation
through back channel and und=r/
tubes.
'/ Return
Effluent
i
H—12"—H
Air-w
FIGURE 7
12.45 GALLON REACTOR DETAILS
-------
SOLIDS GROWTH
EAFB PILOT EXTENDED AERATION UNITS
# MLSS/jrBOD APPLIED
.2
Key:
£3 = Horizontal Flow Side
O = Upflow Side
1.0
0(2-7°C)
.8-
From National Sanitation Foundation (2)
MLSS
#B0D Removed
o c
o .6
CO
to
CO
=*te
O (7-12°C)
t3(2_7°c)
§ -4
CO
C3 (7-12°C)
4
1000 2000 3000
MIXED LIQUOR SUSPENDED SOLIDS (PPM)
4000
-------
TEMPERATURE EFFECTS OF LOADING ON PERFORMANCE
Effluent SS Limited to Less Than 100 ppm
References 1, 3, 24
100-t-
Key:
£3
= 1°-7°C
o =
0 =
7°-12°C
12°-20°C
90-
O
O
tt
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a
a
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O
O
00
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50-
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a
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1
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ORGANIC LOAD
.12
irBOD
.16
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miSS Day
-------
VOLUME PERCENT AT 1/2 HR. VS. DETENTION TIME
EAFB Pilot Extended Aeration Plant
Horizontal Flow Side
Key:
0 = 12-19°C
O = 7-12°C
8 = 2-7°C
2 liter Settlometer used
at EAFB
lOO-i-
Downing (23)
75-
UJ
o
OL
£ 50 i"
UJ
s
ra
_i
o
>•
25
8
it"
DETENTION TIME (Hours)
20
-------
PERFORMANCE VS. SOLIDS CONCENTRATION
EAFB PILOT EXTENDED
AERATION UNITS
Key:
C3 = Horizontal Flow SideLl/2 day
O = Upflow Side J detention
100
NSF Package Plant Data (2)
g 60
LU
ce.
o
o
CO
LU
1500
2000
2500
3500
1000
3000
MIXED LIQUOR SUSPENDED SOLIDS (PPM)
-------
20.-
O
0
A O A
©
A
El
V
Legend
Continuous Flow
©< 1°C
A^ 4°C
intermittent .-low
on 1/2 hr
off 1/2 hr
0^ 3°C
4°C
Intermittent Flow
on 2 hr
off 1 hr
A ^ 8°C
FILSS * 4000 ir.c/1
H 1 1 1 » 1 1 h-
.1 .2 .3 .4 .5 .6 .7 .8
Overflow Rates (gpm/ft^)
FIGURE 12
8.9 GALLON AND 12.45 GALLON REACTORS
EFFLUENT SUSPENDED SOLIDS vs
OVERFLOW RATES AT VARIOUS TEMPERATURES
-------
.10 - •
2 LITER SETTLOMETER TEST, 0-5 MINUTE RATE
EAFB Pilot Extended Aeration Plant
Horizontal Flow Side
Key:
t3 = 2-7°C
O = 7-12°C
0 = 12-19°C
o ooo
o
o o o
oo o
0
o o o
O 00 o
t$3 O 0 O 0 0
—0—mi e—ea— o
1000 2000 3000
MIXED LIQUOR SUSPENDED SOLIDS (PPM)
-------
Weir Plate Guide (2)
/
Weir Back-up Wall
_2_
IQ
C
-5
ft>
I I J
J—*/
L_>
Floats (2)' Attached Only to Weir Plate
-------
HYPOTHETICAL DAILY SEWAGE FLOW PATTERN
24 hour average - 0.5 MGD
peak - 1.0 MGD
7 T
Ul
20
24
12
16
8
HOURS
-------
80'
4
V _
40' to Max.
Water Level
_ 30' to Mi
Water Level
AERATION
CELL
in. I
1,
¦15' -
r*B
40'
y
Clari fier
Open Aerators
40'
1
AERATION
CELL
All Slopes
1:2
-Hydraulic
Dividing Wall
X
PLAN
Vertical
Wall
J
J
^Housing
Clarifier
y!4.5' Min.
Aerators
ELEVATION SECTION AA
Inlet
Grit
Trough¦
Control
Housing
Clarifier Cover
20' Max.
v14.5 Min.
Clarifier Designed as Hydraulic Wall
Air Header and Aerators
4 v y v v v v v V v v y y -
ELEVATION SECTION BB
1/2 MGD EXTENDED AERATION PLANT
-------
Air Return
Chlorine
Solution
Injection
Sludge Lines
Separator
Boxes
Excess
Sludge
Sump
Excess
Sludge
Floating
Weir Box
Wastage
Mixed
Liquor
Inlet
Air
Lifts
Effluent from
Chlorine Contact Hopper
Dead Zone CLARIFIER SECTION
^60° Hoppers All Walls ^
£Scum Collector Trough
Air Lift Piping
CLARIFIER PLAN
21
-------
References
1. Porges, Ralph and Morris, Grover L., "Extended-Aeration Sewage Treatment,"
Technical Services Branch, Robert A. Taft Sanitary Engineering Center, US Dept.
of Health, Education and Welfare, Cincinnati, Ohio (June, 1960).
2. National Sanitation Foundation, Package Sewage Treatment Plant Criteria
Development, Part I. Extended Aeration (1966).
3. Reed, Sherwood C., and Crowther, Allan W., "Single Tank Secondary Sewage
Treatment for the Arctic," presented at ASCE CRE Symposium, 21st Alaska Science
Conference, University of Alaska (August, 1970).
4. McKinney, R. E., Biological Waste Treatment lecture at University of Alaska
(March 24, 1971).
5. Hart, S. A., "Animal Manure Lagoons - a Questionable Treatment System,"
paper presented at the Second International Symposium for Waste Treatment Lagoons,
Kansas City, Missouri (June 23-25, 1970).
6. Baars, J. D., "The use of Oxidation Ditches for Treatment of Sewage from
Small Communities," W.H.O. Bulletin, V-26 (1962).
7. Pick, A. R., et al., "A Comparative Study of Aerated Lagoon Treatment of
Municipal Wastewaters,1' paper presented at the Second International Symposium
for'Waste Treatment Lagoons, Kansas City, Missouri (June 23-25, 1970).
8. McKinney, R. E. and O'Brien, W. J.."Activated Sludge - Basic Design Concepts,"
Journal of the WPCF, Vol. 40, Pt. 1, No. 11 (November, 1968).
9. Goodman, B. L., Manual for Activated Sludge Sewage Treatment and Design
Handbook of Wastewater Systems, Technomic Publish. Co., Inc., 265 W. State STreet,
Westport, Conn. (1971).
10. Hughes, C. E. Jr., and Reynolds, J. F., "Activated Sludge Studies at Decatur,
Illinois," Journal Water Pollution Control Federation, 41, 184 (February 1969),
Pt. 1.
11. Leary, R. D., Ernst, L. A., and Katz, W. J., "Effect of Oxygen-Transfer
Capabilities on Wastewater Treatment Plant Performance," Journal Water Pollution
Control Federation, 40, 1298 (July, 1968).
12. Eye, T. David, Eastwood, David P., Requena, Fernando, and Spath, David P.,
"Field Evaluation of the Performance of Extended Aeration Plants," Journal of
the Water Pollution Control Federation, Vol. 41, No. 7 (July, 1969).
13. U.S. Federal Water Quality Administration, Northwest Region, Seattle,
Washington, Disinfection Criteria and Design Guidelines, December 15, 1970.
14. Office of Water Programs, "Storage and Handling Facilities for Chemicals,"
EPA, Washington, D.C., technical bulletin D-71-1.
15. Water Pollution Control Federation , "Safety in Wastewater Works," Manual of
Practice No. 1, 3900 Wisconsin Ave., Washington, D.C. 20016.
16. Sottarelli, H., "Using Compressed Gases Safely," (wall chart),
-------
17. "Chlorine Manual," Chlorine Institute, Inc., 342 Madison Avenue, New York,
N.Y. 10017.
18. "Chemical Safety Data Sheets," Manufacturing Chemists Association, 1825
Connecticut Ave., Washington, D.C. 20402.
19. "Hazardous Chemical Data," Publication 42, National Fire PRotection Association,
60 Batterymarch St., Boston, Mass. 02110.
20. Clark, D.B., et al., "Evaluation of Extended Aeration Treatment at Recreation
Areas," Working Paper #68, March 1970, FWPCA, Pacif Northwest WaterNLab., Corvallis,
Oregon.
21. Water Pollution Control Federation, "Highlights, Deeds and Data", Vol. 9,
No. 2 (February 1972).
22. Anonymous, "Operating Manual for Small Extended Aeration, Activated Sludge
Treatment Plants," Alaska Department of Health and Welfare, Division of Public
Health, Juneau, Alaska (October 1963).
23. Downing, A. L., "Factors to be Considered in the Design of Activated Sludge
Plants," Advances in Water Quality. Improvement, pp. 190-202, University of Texas
Press (1968).
24. Clark, Sidney E.,"Coutts, Harold J., and Christianson, Conrad D., "Design
Considerations for Extended Aeration in Alaska," Working Paper No. 5, Federal
Water Quality Administration, Dept. of the Interior, Alaska Water Laboratory,
-------
US EPA
AUDIOVISUAL INSTRUCTION UNITS
INSTRUCTION UNITS:
These consist of slides and a narration tape with cues which
• ^ ^ ^ — .» *11 » - — * ±- — ' — -1 • • J -
nuvvtttuwxwaxj.^ wiiuu^c oxxuca xii a ^ivjCVoCd * r\±.± uiax ua iuvxuuc
a script of the narration.
BORROWING SLIDE-TAPE UNITS:
Upon request for a loan, the National Training Center will mail:
1 set of slides in proper order in a Carousel tray
1 cassette tape of narration with cues to automatically change
slides for the series
1 tape playback unit with a connection for a projector*
1 instruction sheet regarding setting up the equipment
1 copy of the script for the series
1 copy of any associated instructional materials
1 sheet for record information to return to the Center
The User Must Provide:
-A projector equivalent to a Kodak Carousel slide projector
-A screen
FURTHER INFORMATION: Please address correspondence to:
ENVIRONMENTAL PROTECTION AGENCY
Office of Water Programs
National Training Center
Audiovisual Instruction Units
4676 Columbia Parkway
-------
OPERATIONAL CONTROL TESTS FOR THE ACTIVATED
SLUDGE PROCESS - Part I
XT-40
ABSTRACT: Part One of a three-part lesson series on operational
control tests for the activated sludge process. Entitled
"Observationsthis first part is concerned with the accurate
reading of meters and with the visual observations to be made
both at the aerator (foam characteristics, sludge color and
odor) and at the final clarifier6 (clarity, evidences of
bulking and of septic solids). Provisional interpretations
to be made of these visual observations are presented, with a
detailed discussion of effective use of a sludge blanket finder.
(1971)
FOR: Experienced wastewater works operators who wish to upgrade
plant performance and to increase their own knowledge and skills,
REFERENCES: West, Proceedings:8th Annual Environmental & Water
Resources, Eng. Conf. , Vanderbilt U. (1969); Mallory, Water Works
& Sewerage (1941 and 1943); Hughes & Reynolds, JWPCF (1969)
and Leary, et.al., JWPCF (1968).
NOTES: 16 minute tape and 51 slides, also script.
"DISSOLVED OXYGEN ANALYSIS—ACTIVATED SLUDGE XT-43
CONTROL TESTING
ABSTRACT: Rapid and valid techniques are described for control
of the activated sludge treatment process using electronic
measurement of DO and DO changes. Sample data are discussed
for interpretation of sludge condition in response to
stabilization, feed, load ratio or conditions. Information
obtainable within 20 minutes provides suggested corrective
action in time to upgrade effluent quality. (1971)
FOR: Advanced wastewater treatment plant operators or plant
control supervisors.
REFERENCES: Bloodgood, Sewage Works Journal (1938); Kessler,
Water Works and Sewerage (1936); Sawyer, Sewage Works Journal
(1939); Hughes and Reynolds, JWPCF (1969), and Manufacturers'
literature.
-------
OPERATIONAL CONTROL TESTS FOR THE ACTIVATED XT-41
SLUDGE PROCESS - Part II
ABSTRACT: Part Two of a three-part lesson series on operational
control tests for the activated sludge process. This part is
a detailed discussion of the preferred techniques involved in
conducting settlometer tests to determine settling character-
istics and in centrifuging samples to determine the concen-
tration of the mixed liquor and return sludge. Handling the
related samples is included along with provisional interpre-
tations and applications of the tests presented. (19 71)
FOR: Experienced wastewater works operators who wish to upgrade
plant performance and to increase their own knowledge and
skills.
REFERENCES: West, Proceedings:8th Annual Environmental & Water
Resources Eng. Conf., Vanderbilt U. (1969); Mallory, Water
Works & Sewerage (1941 and 1943); Hughes, JWPCF (1969) ; and
Leary, et.al., JWPCF (1968)
NOTES: 17 minute tape and 47 slides, also script.
OPERATIONAL CONTROL TESTS FOR THE ACTIVATED XT-42
SLUDGE PROCESS - Part III
ABSTRACT: Part Three of a three-part lesson series on operational
control tests for the activated sludge process. This conclud-
ing part presents development of settling and concentration
curves from settlometer and centrifuge test "results, techniques
for conducting turbidity tests as well as the significance of
turbidity results, a summary of all the tests presented in
the three-part series, the control adjustments which are made
on the basis of these test results, and progressive trend
charts of process characteristics. (1971)
FOR: Experienced wastewater works operators who wish to upgrade
plant performance and to increase their own knowledge and skills.
REFERENCES: West, Proceedings'8th Annual Environmental & Water
Resources Eng. Conf., Vanderbilt U. (1969); Mallory, Water
Works & Sewerage (1941 and 1943); Hughes & Reynolds, JWPCF
(1969); and Leary, et.al., JWPCF (1968).
-------
THE APPLICATION OF PHYSICAL-CHEMICAL
TREATMENT METHODS IN ARCTIC REGIONS*
R. M. Smith**
Alaska is truly America's last frontier, and, in land area, is a very
large State. Alaska covers more than 585,000 square miles and contains
more than two thirds of the United States coastline.* More than one third
of our fresh water exists in this State. Up until the recent past, Alaska,
and much of the other Arctic regions of our neighbors in Canada, have been
hindered in their development, for many reasons. One of the most
predominant of which is the wastewater disposal problem.
INTRODUCTION
Let us look at some of the factors that enter into this problem. At or
near the ground surface, water or ice make up the vast majority of the soil
mass, but this lessens at greater depth. The average annual ground temp-
erature ranges from 10 to 15 degrees, at 20 to 30 foot depths, and the earth
is frozen a thousand feet or more in depth. Layers or lenses of ice are
common throughout the upper 20 to 30 feet of depth. This zone exists as ice
*For presentation at EPA Technology Transfer Seminar, Anchorage, Alaska,
March 28-29, 1972.
**Vice President and General Manager, Met-Pro Systems Division of Met-Pro
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-2-
for the greater part of the year. Freezing air temperatures occur almost
75 percent of the days of an average year. Summer is virtually continuous
daylight, but air temperatures, on the average, are in the neighborhood of
1 7
40 degrees. Thawing extends only a few inches down from the surface. > c
Burying is virtually impossible, and even if the wastes were buried,
4
they would be preserved for many years. Potential health hazards
obviously remain. The water supply and waste disposal practices which
have been utilized in the southern portion of Alaska, and in many of the
northern "Lower 48" simply are not practical for this location. One can
imagine that a flushing sewage system, without the water to flush the system,
can certainly present many problems, not the least of which is disease.
THE PROBLEM
One area of the arctic, known as the "North Slope" of Alaska, is
projected for tremendous industrial development as the quest for petroleum
reserves expands. It is typical of an arctic region from a wastewater dis-
posal viewpoint. For more than ten years, small settlements of drilling
and expeditionary camps have dotted this area in the search. Facilities
of all kinds--temporary, semi-permanent, and permanent-- have been
constructed on the tundra to house communities of from 40 to 1,000 men.
In support of these communities, roads, air fields, supply points, and
many other facilities are necessary. Most installations must be portable
-------
-3-
This includes the water supply and wastewater facilities as well.
It is no wonder that water supply and wastewater disposal requirements
to support these facilities are difficult to define and expensive to construct.
Water costs range from 4£ to $1 per gallon, depending upon the location
of the facility, since very few sites are located near large quantities of
fresh water. Most water is hauled to the sites, some even by airlift.
Although a great deal of snow and ice are available, the melting of these
supplies is expensive and time consuming. One contractor has admitted
that he will have a $10, 000 per day water bill for this 250-man construction
camp. These costs certainly are unusual for other areas of the world, but
are not out of line when talking about the arctic region.
WASTE CHARACTER
Several years ago an analysis of estimated total water usage for
various types of arctic installations was made and is shown in Figure 1.
The breakdown of these quantities is shown in Figure 2, where the per-
centage of the total water usage for each purpose is given. The anticipated
concentrations of waste constituents is given in Figure 3, based on waste-
waters of non-arctic origin. Using the data from the preceding Figures
and calculating combined waste characteristics, we have the values shown
in Figure 4. Also shown is a "normal" raw sewage for comparison.
Subsequent to this estimation, numerous samples were collected from
-------
-4-
higher concentrations of pollutants have been experienced there. This
could be anticipated, since caloric intake is extremely high in these
climates, and water consumption is somewhat reduced. Design values
for BOD and COD for example, indicate a BOD in the range of 400 to 800
mg/L and a COD of 1, 000 to 1, 600 mg/L. Surprising, the flows were
not much different than what would be experienced anywhere in more
temperate regions: 30 to 120 gallons per capita per day with an average
5
of 84 gallons per capita per day, based on six camps' usage.
Very early in the analysis of the waste disposal problems in arctic
areas, the possible segregation of various wastewaters was approached
with camp owners and constructors, and was met with considerable
resistance, based on the anticipated costs of the separate collection lines.
Further, the possibility of recirculation of partially treated wastewater,
for whatever purpose, back into the camp proper, also compounded costs
since every pipeline meant tens of thousands of dollars in the cost of camp
construction.
However, based on the experience gained to date, it would seem that
these costs could quite likely be amortized very quickly with the high
water supply costs. Several camps have practiced recirculation of the
effluent from their wastewater treatment facility for toilet flushing, with
good success. Figure 5 shows one example of how this is accomplished.
Further, water usage can be reduced significantly by use of conventional,
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-5-
TREATMENT NEEDS
In arctic regions, restrictions from an environmental and economic
point of view are many when considering the waste treatment alternatives.
As a service to the many groups which have descended upon the arctic
regions of Alaska, the Alaska Department of Health and Welfare issued a
series of guidelines. A quotation from those guidelines will serve to
emphasize the needs of the area.
"Cold is a resource to be understood, evaluated, respected and
often used in far north operations. The implications of the "cold
resource" should be evaluated and appropriately considered in respect
to each mission and service. Many conventional systems and processes
have not been shown to be feasible, economical, or effective in cold
region application. Yet, public health objectives must be met regardless
of climatic conditions. All facilities and services will be reviewed from
the viewpoint of cold region usefulness in meeting overall public health
objectives."
Regarding water pollution control, the following statement is
emphasized:
"In water pollution control, the Alaska Water Quality Standards
embody policies which will guide in assessing the adequacy of control
measures. The water uses to be protected, the level of water quality
to be maintained, and--particularly--the policy that all means for
-------
fundamentals and the standards which will be applied to these guidelines.1
In view of the many restrictions that have been outlined above, the
waste treatment system to be utilized should incorporate the following. ^
1. Minimum physical size
2. Minimum sensitivity to temperature
3. Maximum removal efficiency in terms of:
a. Color
b. COD
c. Solids
d. Turbidity
e. Odor
4. Maximum ability to start and stop without deterioration in
treatment efficiency
5. Positive control of treatment capabilities
6. Relative ease of operation
TREATMENT ALTERNATIVES
Reasonable reductions of BOD, suspended solids, and other material
is required with a target for a minimum of 80 percent removal of these
contaminants. Those concerned with waste treatment in the arctic have
three basic routes for treatment: physical, chemical, biological, or
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-7-
The one system which most closely fulfills the needs of treatment
outlined above, and meets the various constraints mentioned previously,
is physical-chemical treatment. This decision, made several years
5
ago, has been borne out in field experience.
A combination of biological and physical-chemical treatment might
also be employed. This would constitute utilization of a package biological
treatment plant for pretreatment, followed by a tertiary physical-chemical
treatment. Of course, this would occupy more space and therefore add to
the cost of installation and operation. On one recent study of a 50, 000
gallon per day facility, the land area required for the physical-chemical
plant was less than 50 percent of that of a biological package plant plus
tertiary treatment, to achieve similar overall removal efficiencies.
The superior treatment that can be obtained with physical-chemical
treatment in an "on-off" operation is particularly important when compared
with biological methods. Extended aeration facilities at one drilling camp
were slow in getting started, and an adequate biological mass had not
developed following 90 days of operation. One author has observed that
"biological plants placed in operation to serve drill sites are really not
5
much more than primary settling basins for the first two months."
PROCESS DESCRIPTION
Why do we call this physical-chemical treatment"> The obvious answer
-------
-8-
experience of many consultants, designers and operations personnel in
various parts of the world, the usual process sequence is chemical
addition, coagulation, sedimentation, adsorption and filtration, Figure 6.
Provided that adequate coagulant is employed, the chemical addition,
coagulation, and sedimentation sequence can be expected to remove in the
neighborhood of 65 to 80 percent of the COD, color, turbidity, phosphorus
and some oil and grease.
Adsorption on granular activated carbon provides further removal of
dissolved organic matter while filtration polishes the adsorber effluent for
removal of suspended solids. Subsequent disinfection will render the
wastewater suitable for discharge and also for reuse. In terms of comparing
it with a biological plus physical-chemical plant, a strictly physical-chemical
plant is frequently termed Independent Physical-Chemical treatment or IPC.
The type of effluent that can be obtained from such a facility is shown on
Figure 7. One such treatment plant, for a flow of only 7, 000 gallons per
day, is shown in Figure 8.
FLOW EQUALIZATION
Since most waste treatment facilities to be constructed in arctic regions
are for small communities or oil related installations, flow variations are
quite severe and treatment efficiencies could be seriously affected. An
g
example is shown in Figure 9. Physical-chemical treatment methods
-------
-9-
operated on a steady or controlled flow of wastewater. For this reason,
flow equalization ahead of these treatment facilities is desirable.
Equalization tanks for arctic facilities would normally be constructed
above grade and have the raw sewage, at varying rates, pumped into it.
Likewise, the flow out of the equalization tank would normally be pumped
to treatment. Waste depths of 5 to 8 feet would be utilized. Aeration is
a necessity for maintaining solids in suspension and preventing odor
production. In most tanks all horizontal corners should be filletted to
prevent solids deposition as well. The horsepower input for mixing may
vary depending upon the type of equipment utilized, but a usual air require-
ment is 20 cfm per 1,000 cubic feet.of tank capacity. The cost of flow
equalization is minimal when compared with the elaborate instrumentation
that would be required to control chemical feed and pump rates with a
widely varying flow. A tank sufficient to hold 50 percent of a day's flow
is desirable for the smaller facilities. Using the flow rates given in
Figure 9, Figure 10 was developed, indicating the varying liquid level in
the equalizing tank, with time. Another method for computing tank volume
is given in the Process Design Manual for Upgrading Existing Wastewater
7
Treatment Plants.
COAGULATION
Much has been written about the preferred coagulants-for use in
-------
-10-
employed, alone and in combination with polyelectrolytes. Polyelectrolytes
have also been used alone where phosphorus removal is not a requirement.
If phosphorus removal is required, then one of the inorganic coagulants
must be employed. To date, the most desirable method of obtaining the
proper dose of coagulant has been to conduct jar tests on the wastewater
involved. For those situations where detailed control is desired, turbidity
monitoring can be employed on the clarifier effluent.
In the smaller plants, with flows up to several hundred thousand
gallons per day, where the feasibility of coagulant recovery is nonexistent,
the metallic coagulants are usually employed. They are easier to feed
and usually produce less pounds of solids per 1,000 gallons of wastewater
treatment, than with lime.
Flocculation of 10 to 20 minutes, preceded by a flash mix of 1 5 to 60
seconds is normally employed. Automatic pH control has been designed
into several plants where metallic coagulants are used, to optimize
treatment performance. However, pH control is regularly employed to
control lime dosage when that is the coagulant of choice.
Usual removal through this first stage of physical-chemical treatment
will be: BOD - 65 to 80 percent, suspended solids - 90 to 95 percent,
9
-------
-11-
CLARIFICATION
Clarification can be accomplished in conventional circular clarifiers
with center or peripheral feed at hydraulic overflow rates of up to 1, 000
gallons per day per square foot. Solids contact clarifiers may also be
employed, so long as the solids blanket is not allowed to become septic.
With aerated flow equalization, this should not be a problem.
The coagulated solids, containing the precipitated phosphates and
sewage solids, will normally settle to 0.5 to 1.5 percent solids in the
clarifier, with separate external thickening increasing this to 2 to 4
percent solids, by weight.
ADSORPTION
Granular activated carbon is the preferred adsorbent for the soluble
organics, following chemical clarification. Several mesh sizes are
available from the different manufacturers and they all have application
in this step of treatment. Usual sizes employed are 8 x 30 mesh and
12 x 40 mesh.
This step can be accomplished in several modes: (11 pressure upflow,
(2) pressure downflow, (3) expanded bed upflow and (4) gravity downflow.
Each has its application. In our work we feel that the expanded bed upflow
design offers several advantages, brought about by the configuration
employed. Hydraulic expansion, with the waste flow alone, requires upflow
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-12-
A modification of this is to utilize a small amount of air flow, with
less liquid flow per square foot, to obtain the same degree of expansion.
With a liquid flow of under 2 gallons per minute per square foot, and an
air rate of 0.2 scfm per square foot, the desired 10 to 15 percent bed
expansion is obtained. And, the air helps keep the carbon aerobic and
odor free. In this way, the carbon is kept in suspension and the required
adsorption time can be obtained in larger diameter, shorter height
columns. This also facilitates the portability of the physical-chemical
plant. A comparison of carbon column dimensions is shown in Figure 11.
Two or more columns, in series, are normally employed with the waste-
water flowing countercurrent to the carbon as shown in Figure 12. Carbon
usage can be expected to run 500 to 800 pounds per million gallons of
sewage treated, while operating in the mode outlined above.^
The effluent from the second column will normally have a BOD of
10 to 15 mg/L, which is superior to the typical secondary biological plant.
A large percentage of this BOD will be biological solids that grew on the
organic-rich carbon particle surface.
When utilizing a fluidized or expanded bed adsorption system, post
filtration is highly desirable. Pre-filtration is not normally employed
since suspended solids carryover from the clarifier, if present, can pass
upward through the activated carbon and out in the effluent--going to the
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-13-
FILTRATION
Although gravity filtration may be desirable from many viewpoints,
pressure filtration minimizes filter area and thus helps to keep the over-
all plant size to a minimum.
Following the adsorbers, a small surge tank of 5 minute flow capacity
is employed to even out minor plant flow variations. A pressure filter pump,
which if properly chosen and installed can also operate as a backwash
pump, discharges to the filter, at rates of up to 5 gallons per minute per
square foot. Dual media is employed with a 1 to 1.5 mm anthracite over
a 0.5 mm sand, and depths of 18 inches and 6 to 9 inches respectively.
Backwash of the pressure filter should be controlled by pressure
differential across the media bed and the use of a several minute pre-
backwash air scour, is also helpful to keep the media clean. The source
of backwash water can be the "dirty" adsorber effluent or disinfected
pressure filter effluent. In either event dirty backwash water should be
directed back to the flow equalization tank for treatment through the entire
system.
DISINFECTION
A great amount of study has been given to the question of the preferred
method of disinfection in the arctic. There are several alternates including:
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-14-
With the transport problems of the various chlorine containing compounds,
the other alternates appear promising.
Work on the effluent from a physical-chemical plant, at the Cincinnati
Labs of EPA, with ultraviolet light, proved highly satisfactory with only
electrical power to supply. The same is true of ozone, although a contact
tank is then required.
From a practical point of view, ultraviolet disinfection should be the
method of choice. Several manufacturers offer this equipment in various
sizes and ratings and it has been proven effective in years of service in
bottling plants and other applications.
SLUDGE DISPOSAL
As mentioned previously, the sludge which settles out in the clarifier
will normally contain 1 to 1.5 percent solids. If desired, this sludge can
be separately gravity thickened to 2 to 4 percent solids with 4 to 6 hours
settling. Then some type of dewatering equipment could further concentrate
it for ultimate disposal. An alternate would be to draw the sludge from the
clarifier directly to dewatering equipment.
As you can visualize, the small amount of sludge generated from most
of the physical-chemical plants discussed, is quite a different problem to
dewater than that from larger municipal treatment facilities. It has been
experienced that the sludge production per 1, 000 gallons of sewage treated
-------
-15-
20 to 40 gallons of sludge per 1,000 gallons treated. The wide variation
in sludge production rate is influenced by the type and quantity of
coagulant, the raw sewage solids content, the alkalinity and phosphate
content of the wastewater and whether the spent activated carbon is disposed
of with the chemically precipitated solids.
Whether a separate sludge concentrator is utilized or not, it is
desirable to have a sludge storage tank for holding the sludge until there
is sufficient accumulated to make a "run" of the dewatering equipment.
A wide variety of equipment has been utilized to further concentrate
the sludge for ultimate disposal. Among this equipment are: (1) small
basket centrifuges, (2) small horizontal vacuum filters, (3) continuous paper
belt traveling filters.
The centrifuge, Figure 13, has produced up to 12 percent dry solids
as part of a physical-chemical treatment system developed for shipboard
waste disposal; the horizontal vacuum filter, Figure 14, can produce 10 to
20 percent dry solids, while the traveling belt filter, Figure 15, will
concentrate physical-chemical sludge to 5 to 6 percent solids. The latter
operates with only a 6 to 8 inch liquid head, so it is not capable of producing
nearly the sludge concentration of the vacuum filters or centrifuges.
The concentrated and dewatered solids can then be handled by usual
trash incinerating equipment available from many suppliers. The spent
-------
-16-
An alternate would be to incorporate the carbon into the sludge prior to
dewatering and handle it as one slurry.
INSTALLATION
With flow equalization tankage, exposed piping and solids disposal
equipment being a part of a physical-chemical plant, it is imperative that
the system be installed inside a heated building.
On the North Slope, plants have been installed inside prefabricated
metal buildings where the temperature is maintained above 40° F. All of
the treatment units are usually skid-mounted, arranged for above ground
installation and are thus usually set on heavy timbers, crushed stone, or
a concrete slab.
Separate clean space should be provided for some laboratory work,
and storage of chemicals for several months operation is required. Six (6)
feet of clear space around the treatment unit is desirable, with a ceiling
height of 15 to 16 feet. If utilized at the site, the incinerator, and sludge
holding tanks, and reuse water storage, should also be located near the
plant.
TYPICAL PERFORMANCE
One Independent Physical-Chemical waste treatment system, identical
to one installed on the North Slope, was installed and operated for a short
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-17-
summarized on Figure 16. These data represent the average of a wide
range of operating conditions and are taken across the entire plant.
These tests were run on sewage in a piece of integrated equipment
that had been developed by the manufacturer, for treating laundry waste-
waters by physical-chemical processes. However, it did contain the
necessary unit processes to prove the concept. Since these tests were run,
the manufacturer has developed a complete line of equipment especially
for physical-chemical treatment of sewage that incorporate the features
outlined previously.
SUMMARY
Physical-chemical treatment methods are certainly one of the most
desirable routes to follow when considering alternatives for arctic waste
disposal. Flexibility, portability, available control, on-off operation and
effluent quality are all of such importance in this very ecologically
consious area, that this method will probably grow in importance in the
months and years ahead.
Several systems are already installed, others will be in the immediate
future, and more, now on the drawing boards will follow in the months
ahead. Many engineers have realized the significant benefits to be gained
by physical-chemical treatment in the arctic and we hope that the facts
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BIBLIOGRAPHY
1. Anonymous, "The Alaska Plan, A Statement of Economic and
Ecological Purpose, " Alaska Department of Economic Development,
Pouch EE, Juneau, Alaska 99801.
2. Alter, Amos J., Sidney E. Clark, and E.K. Day, "Arctic Waste
Management, " presented at Purdue Industrial Waste Conference, May
1970, West Lafayette, Indiana.
3. Alter, Amos J., "Water and Waste Systems for North Slope Alaska, "
1969.
4. Cold Regions Research & Engineering Laboratory, "Sewerage and
Sewage Disposal in Cold Regions, " Cold Regions Science and Engineering
Monograph III-C5a, 1969.
5. Clark, S. E. , A.J. Alter, J. W. Scribner, H.J. Coutts, C.D.
Christianson and W.T. McFall, "Alaskan Industry Experience in Arctic
Sewage Treatment," 26th Purdue Industrial Waste Conference, May 1971.
6. Kreissl, J. F., S.E. Clark, J.M. Cohen and A. J. Alter, "Advanced
Waste Treatment and Alaska's North Slope, " Cold Regions Engineering
Symposium, College, Alaska, August 17-19, 1970.
7. Weston, Roy F. , Inc., "Process Design Manual for Upgrading Existing
Wastewater Treatment Plants, " EPA Contract No. 14-12-933, Program
No. 17090 GNQ, October 1971, pages 3-2 and 3-3.
8. National Sanitation Foundation, "Package Plant Criteria Development
Part I: Extended Aeration, 11 September 1966, page 42.
9. Kugelman, I.J. and J.M. Cohen, "Physical- Chemical Processes, "
Technology Transfer Design Seminar for Municipal Wastewater Treatment
Facilities, New York, February 29 and March 1-2, 1972.
10. Lawrence, Alonzo Wm. , "Granular Activated Carbon Treatment of
Primary and Chemically Treated Effluents," Proceedings of 3rd Annual
Northeastern Regional Anti-Pollution Conference, University of Rhode
-------
APPROXIMATE WATER USAGE
WHICH MAY BE ANTICIPATED
FOR VARIOUS COLD REGION INSTALLATIONS
(In gallons per capita per day)
TYPE OF SERVICE
RANGE OF USE
ANTICIPATED
AVERAGE USE
Field Use
(No central water supply)
10 to 20
15
Field Use
(Central water not under
pressure)
20 to 40
30
Temporary Camp
(Water under pressure)
30 to 50
40
Semi- Permanent Facility
(Water under pressure)
30 to 60
45
Permanent Facility
60 to 100
80
-------
ESTIMATED QUANTITIES OF WATER USED
FOR EACH PURPOSE
TYPE OF USE FOR WATER
QUANTITY EXPRESSED AS A
PERCENTAGE OF TOTAL PER
CAPITA PER DAY CONSUMPTION
RANGE
AVERAGE
Drinking and Culinary
15 to 25
20
Washbasins, Showers & Bathing
20 to 50
30
Water Flush Toilets
15 to 35
25
Laundry
10 to 30
20
Miscellaneous, Washing, Scrubbing,
Mopping, Flushing, etc.
--
5
-------
ANALYSIS OF WASTE STREAMS
(Concentration, mg/L)
Constituent
Kitchen
Wastewater
Synthetic
Shower Waste
Institutional
Laundry
Wastewater
Toilet
Wastewater
pH (units)
7.4
7.7
9.3
--
Turbidity (J. U.)
462
58
39
--
Alkalinity as CaCOg
233
200
497
Hardness as CaCOj
91
288
27
COD
1377
220
225
11 60
Oil & Grease
293
54
16
Surfactants
12
2
5
Suspended Solids
598
190
29
360
P as PO.
4
26
6
12
68
NH3 as N
9
4
2
116
N03
< 1
< 1
< 1
TDS
1409
924
865
1250
-------
COMBINED WASTE CHARACTERISTICS
Concentration, mg/L
Constituent
Calculated Waste
Raw Sewage
pH (Units)
8.1
7.5
Turbidity (J.U.)
168
--
Alkalinity as CaCO^)
294
263
Hardness as CaCO^)
157
278
COD
710
350
Oil & Grease
111
20
Surfactants
6
7
Suspended Solids
287
250
P as PO.
4
28
24
NH3 as N
34
16
N03 as N
1
1
TDS
1100
500
-------
FIG.5
LAUNDRY
WASH
BASINS
KITCHEN
DRINKING
FOUNTAINS
TOILET
SLUDGE
EFFLUENT
PHYSICAL CHEMICAL
TREATMENT
WATER SUPPLY
-------
AIR
COAGULANT
RAW
SEWAGE
SLUDGE TO DISPOSAL
MAKEUP CARBON
FIGURE 6
A PHYSICAL CHEMICAL TREATMENT SYSTEM FLOW DIAGRAM
CLARIFICATION
CARBON
ADSORPTION
DISINFECTION
FILTRATION
PRELIMINARY
-------
FIG.7
EFFLUENT QUALITY FOR INDEPENDENT
PHYSICAL CHEMICAL TREATMENT
BOD 2-10mg/L
SUSPENDED SOLIDS 5-10mg/L
-------
"V
Vi'r-C^ &S£? -
FIGURE 8
-------
FIG.9
DIURNAL SEWAGE FLOW RATE FOR SMALL PLANTS
3400
3200
3000
2800
2600-125%
2400
2200
AVERAGE FLOW RATE
2000
75%
1200
50%
1000
800
600
400
200
MID
NIGHT
MID
NIGHT
-------
F1G.10
14000
13,000
STARTING LEVEL
12,000
j 11000
, 10000
9000
¦ 7000
5000
_j 6000
<
4000
5g 3000
¦r1 2000
1000
LEVEL=STARTING VOLUME + HOURLY INFLUENT-^
24
0 1 23456 7 8 9 10 II N 1 23
MID 2
NIGHT ft
5 6 7 8 9 10 11 12
MID
NIGHT
-------
3 FT.DIA.
FIG.ll
30 FT.
5 FT. DIA.
r
7 FT.
w
WASTEWATER FLUIDIZED AIR ASSIST FLUIDIZATION
COMPARISON OF ADSORBER DIMENSIONS
-------
FIG.12
ADSORBER NO.1
ADSORBER NO.2
SPENT
CARBON
FRESH
CARBON
CLARIFIED SEWAGE
-------
FIGURE 13
CENTRIFUGAL CLARIFIER FOR DEWATERING
-------
FIGURE 14-
-------
FIGURE 15
-------
FIGURE 16
SUMMARY OP RESULTS
IPC WASTEWATER TREATMENT PLANT
INFLUENT
EFFLUENT
% REMOVAL
COD, mg/L
330
14
96
Turbidity, JTU
96
3
97
Color, Units
48
4
92
Total P, mg/L
10
0.1
99
Suspended Solids, mg/L
150
3(est.
-------
*
LAGOON SEWAGE TREATMENT FOR THE ARCTIC AND SUB-ARCTIC
PREPARED BY
J.W. GRAINGE, P. ENG., REGIONAL ENGINEER
J.K. GREENWOOD, RESEARCH ENGINEER
ENVIRONMENTAL PROTECTION SERVICE
ENVIRONMENT CANADA
AND
J.W. SHAW, P. ENG.
HEALTH AND WELFARE CANADA
257 FEDERAL PUBLIC BUILDING
EDMONTON 2, ALBERTA
CANADA
FOR
THE ENVIRONMENTAL PROTECTION AGENCY
TECHNOLOGY TRANSFER SEMINAR
ANCHORAGE, ALASKA
MARCH 28-29, 1972
* _
The opinions in this paper are those of the authors and they
do not represent the policies of the Environment Canada and
-------
PART I
ARE SEWAGE LAGOONS* THE ANSWER?
Introduction
It is only too easy, when one is only familiar with the
comforts, the conveniences, or indeed the stresses of city life
in the "south", to assume that pollution problems in the north
will be essentially similar, and that they will require the same
kind of solutions as we are beginning to impose on the more
densely-populated regions. We feel pressured to require uniform,
nation-wide standards for waste disposal, whether for effluent
quality at sewage outfalls, or for the water quality to be main-
tained on rivers, or for the city people who must dispose of
their garbage. But this seductively simple approach to regulations,
which seems so fair, leads to requirements which are neither
equitable nor workable.
You will hardly be surprised to be told that different types
of northern operations produce different quantities and types of
wastes, and the stresses which they in turn exert on the natural
environment vary in their seriousness.
In general, uniform standards for waste treatment are impracticable
too strong in many situations to be obeyed, and too weak in others,
to do any good. Standards must be variable, to take into account
the nature of the activity producing the waste, and the duration
of the activity. Perhaps even more important, and more often
ignored, the standards should take into account the nature of the
receiving body, be it lake, stream or dry land.
It may make admirable sense to take, for example, drastic
measures to preserve Lake Tahoe, which is a highly admired tourist
and recreational lake. However, much of the arctic tundra is
characterized by a multitude of shallow lakes and swamps, and it
would be over ambitious to try to prevent eutrophication of one
or two of these often already thoroughly eutrophic bodies.
* - In this paper sewage oxidation ponds, sewage lagoons and
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2
We should question whether a village beside a small but
well-stocked trout stream in the south would be more likely to
degrade the environment for more people, than a settlement beside
the huge Mackenzie River. The quality and flow of many northern
rivers varies enormously over the seasons, without any assistance
from man, and it is arguable that any changes such as a few
people were able to make in the river quality would go unnoticed
beside the catastrophic variations wrought by nature.
As with all waste treatment situations from small, isolated
places, there are two goals which should be achieved, i.e. the
avoidance of any health hazard by the protection of public
thoroughfares and water supplies, and the avoidance of public
misance from odors, or unsightliness. As long as these objectives
are met, there is usually little need to go to any more elaborate
systems. Consider, therefore, the alternatives available for
sewage treatment in the north.
Alternative Sewage Treatment Methods in Northern Settlements
1. Discharge of all sewage into an unprepared tundra depression
or a natural lake in such a way as to avoid any risk of infiltration
into the settlement water supply.
At first sight, this disposal method seems very little different
from the lagoon principle. A lagoon is usually pictured as some-
thing which has been constructed by digging into the ground, and
building berms of a predetermined height, slope and material
specification. The use of a natural lake without surface prepara-
tion could serve the same purpose, in that summer bacterial and
algal growth will serve to stabilize the sewage,and the effluent
from the lagoon would be of very good quality. ^Furthermore, this
disposal "system"has the marked advantage of complete simplicity.
As long as the outfall to the lagoon is well protected from freezing,
all wastes can be routinely flushed away and "forgotten about".
The avoidance of site preparation may be advantageous in permafrost
regions, where disturbance of ground cover has been known to cause
progressive melting of the permafrost, and, frequently, extensive
slumping of the ground. This becomes particularly significant if
the slumping actually alters drainage patterns, affecting stream
life, or if it threatens nearby construction. The use of an
existing lake, already in equilibrium with a thaw bowl beneath it,
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3
There are, of course, some objections to raise against such
a simple "solution". The main one is that without bottom pre-
paration there is insufficient control over the flow of liquid
and solids through the lagoon. Solid materials will be trapped
by emergent vegetation, and will build up in localized areas,
particularly near the intake. In the spring and summer these
"sludge banks" (which may in fact be very largely grease and
paper wastes) will be unsightly, surely a natural attraction for
flies, and thus a possible disease risk. Less noticeable, but
also significant, is the effect of an uneven pond on the liquid
flow. Treatment, or stabilization of suspended and dissolved
materials in the water must depend on the detention time of these
materials in the pond, as well as on the surface area for trans-
mission of solar energy. Yet a badly chosen pond might suffer
from considerable short-circuiting, with most of the effluent
passing rapidly through in a "channel" while the rest of the lake
lies stagnant. The extent to which this would happen would depend
on the situation, but one's usual assumptions on the areas required
for a given waste load could be quite misleading.
The plan to use the natural lake or depression has some draw-
backs. But this does not mean we should condemn it out of hand.
The town of Inuvik, N.W.T. has a very expensive utilidor system
for the collection of sewage, which terminates in just such a lagoon
as described above. All the criticisms raised above apply to the
Inuvik lagoon, which is indeed offensive to those of us used to
better things. But think for a moment of its low cost, and its
flexibility. In 1959 Inuvik's population was about 1,000. It is
now nearer 3,500, and this figure is expected to double within
another 15 years. If an expensive, manufactured activated sludge
plant had been installed in the late fifties, it would have been
sized perhaps for 2,000 people. For a few years it would have
operated poorly, because of being underloaded, then remarkably
quickly - perhaps within five years, it would be very overloaded,
and a new plant would have been needed. Today that second plant,
perhaps designed for 3,000 people, would be in turn obsolete. The
funds which would have been spent on the plant were better spent
-------
4
can be no doubt that in spite of its latter day deterioration,
the Inuvik lagoon lias served extremely well for a long time.
These are facts to be borne in mind.
2. Spray discharge of sewage, or ditch irrigation, onto "dry"
tundra.
This idea of course is hardly a new one. Over large areas
of the world farmers have been using human and animal wastes for
centuries to fertilize soil. Even treated sewage effluents
contain high concentrations of dissolved nutrients which, we are
realizing, would in general be more valuable to us if returned
to the soil than if flushed out to sea. Furthermore, in the
south, where the population is more dense, our established habits
of pouring nutrients into surface waters has the annoying result
of encouraging plankton growth in our most prized lakes and rivers,
and upsetting our fishing, swimming and drinking uses of these
waters. Returning the sewage to the land can be a means of pre-
venting deterioration of the recreational waters.
A review of the possibilities for irrigation in the far north,
as a method of waste disposal, reveals that while it should be
widely possible, there are probably few significant advantages to
such a system to justify the expense of installation, and there
may be certain disadvantages, depending on your point of view.
We can assume for a start that there is little or no agricultural
activity around the settlements on the arctic and sub-arctic, so
that refertilization of the soil has doubtful value to man. Again,
certain biologists working in the undeveloped north feel that one's
aims should always be to minimize change of the natural environment,
and that a "positive" alteration of biota caused by increased
fertility of the land near a settlement is just as undesirable as
a "negative" change such as clearing of forest land. In both cases,
natural habitat for animals is altered, and new animal populations
and behavior patterns which are dependent on the ephemeral presence
of man, will emerge. As I mentioned earlier, it rather depends on
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5
More specific engineering and public health objections
can also be raised against the irrigation concept which render it
relatively unattractive. Because of the widespread permafrost,
and the rather poor percolation characteristics of many northern
soils, one can predict that application rates in many areas would
have to be very low if flooding and runoff is to be avoided.
Moreover, it would be preferable to disseminate treated effluents
in this way, because sewage solids would more quickly clog soils
and create worsening conditions. Hence, one is still looking at
a lagoon as the basic treatment device. I say a lagoon, rather
than some other, shorter detention settling basin, because it is
likely that irrigation could only be carried out in the summer
months, to avoid freezing problems, and if so, considerable winter
storage becomes necessary.
All this is not to say that sewage effluents cannot be
discharged to the tundra at significantly higher rates, faster than
the ability of the soils to absorb the liquid.
3. Discharge or raw or partially treated sewage to remote and
inaccessible swampland.
The sewage from the serviced portion of Hay River, N.W.T.
passes through two short-detention (4 day) deep settling ponds
and is then discharged to low lying forested tundra and swampland.
As long as the drainage is generally away from inhabited areas,
it is hard to find great fault with this practice, no matter how
little treatment is achieved in the primary settling ponds.
4. Discharge of untreated sewage into a large stream such as
the Mackenzie River, so that the resulting concentrations of
nutrients, pathogens, and viruses are so low as to cause negligible
health risk to downstream water users, and negligible ecological
changes which might threaten the aquatic ecosystem.
Leaving aside, for the moment, the question of political accept-
ability of this disposal system, the only objections to this
solution must be in whether or not the conditions implied in the
-------
6
calculations which show that if the sewage from 600 people at,
nay, Fort Norman on the Mackenzie River were completely mixed
with the entire river flow at that point, then resulting con-
centrations of any of the usual contamination indicators would
he below normal detection limits. However, there are indications
that quite poor mixing may be the result for many miles downstream.
Unusually high concentrations of coliform bacteria are in fact
found in samples of Mackenzie River water below the villages, and
unless we were to require a prohibitively long and costly outfall,
it would be hard to prove that such a discharge would never present
any health hazard. It is worth noting, however that many northern
rivers, including the Mackenzie, show enormous variability in
their flow rates and sediment load. During the spring flood
these rivers rise dramatically, carrying vastly greater quantities
of \7ater, and scouring the river bottom and banks to a degree which
renders the water quite unsuitable for drinking. Any small dis-
charges during these freshets, even of quantities equivalent to
several months storage, would almost certainly pass unnoticed in
these turbulent, muddy waters.
However, attractive this idea sounds as a convenient and cheap
riverside waste disposal system, it is extremely doubtful that it
is a politically acceptable method during a period in our history
when wo are endeavoring to stamp out this practice everywhere else.
Unfortunately for northern operators, this is just not the time
to suggest that rivers can be looked upon as treatment plants
provided by nature for our use. They used to say/'the solution
to pollution is dilution". Nowadays, one can say, "the prevention
of contention is retention".
5. Discharge effluent into a "properly designed" lagoon, the
aim being to stabilize the sewage so that the effluent meets
typical standards for secondary treatment, and to avoid spring
odor problems, undue sludge buildup, and fly-breeding areas.
We are now coming to "engineered" solutions to the waste dis-
posal problem, and we can expect to see costs rise dramatically
over the simpler systems described previously. But a lagoon is
still relatively cheap to run when compared with small extended-
-------
7
There are certain prerequisites which determine whether a
lagoon like this can or should be built. The primary one is
geological and topographical; there must be a suitable site for
the lagoon, from which the effluent can drain or percolate away
from the camp. If permafrost exists at the site, then the con-
struction of the lagoon will create a thaw bulb in the permafrost;
for this reason relatively stable, low moisture soils are to be
preferred at the lagoon site. The material used for berm construction
must be left open to choice, since it will doubtlessly depend on
the nature of the indigenous soil and the availability of gravel.
Moisture-laden organic soils would be more subject to annual frost
heaving and erosion difficulties, which would necessitate annual
repair of the berms. Gravel berms have the disadvantage of porosity,
but impermeable liners can be used in the lagoon.
Experience with the sludge buildup problem at Inuvik has led
various people to recommend the provision of deep, short-detention
primary ponds to trap much of this material. An added benefit
that these ponds provide is the maintenance of a rather higher
temperature in their lower layers, giving rise to a higher
fate of anaerobiosis. The sludge buildup might be further reduced
if all sewage passed through a grease trap before arriving at the
lagoon.
6. Treat sewage in a "package" biological plant, such as an
extended-aeration unit, or in a package physical or physical-
chemical plant. Numerous proprietary brands are on the market,
each claiming features which render them especially suitable for
small northern operations.
The available biological units all operate on essentially
the same principle, that of complete oxidation (so-called). If
provided with careful, frequent maintenance, there is no real
reason why they cannot operate perfectly satisfactorily. However,
they do have a significant drawback in that time is required for
sludge buildup in the oxidation chamber before they reach full
treatment effectiveness. Experience in Alaska is that this lag
-------
8
employing 3ome mix of chemical flocculation, precipitation and
filtering can operate fully effectively from the day it is hooked
up, but there is the problem of cost. Chemicals must be bought
and added daily. Sludge must be removed and disposed of, probably
by incineration. Filters must be backwashed or otherwise cleaned.
All this represents the services of a relatively skilled operator,
well
who must be/paid. A third type of package treatment unit is one
which relies on heat treatment and incineration of all liquid
wastes. These last systems are capable of supplying "pasteurized"
recycled water - a feature that is only significant if water is
particularly scarce.
All these systems must be critically analyzed for their
sensitivity to mechanical failure. Our experience in the north has
lent us a slightly cynical faith in the validity of Murphy's First
Law (or is it Finagle's Law) which says that if something can
possibly go wrong with a mechanical system and bring everything
to a grinding halt, then it will. It is no use denying that shut-
downs will happen, and if repair and maintenance is to be effective,
these plants must be housed and heated, so that the operators may
replace pumps or clean out plugged and frozen lines in relative
comfort. Spare parts must be rapidly available; operators and
maintenance men have to be trained so that they know what they
are doing, and above all, do not expect a biological plant to
suffer an extended shutdown and then pick up just where it left off.
Small extended-aeration plants take a fair amount of attention
and understanding to qperate well; and it is worth remarking that
a plant which is not operating well is of little use. Very little
heavy equipment ever seems to get transported out of the north,
and a package sewage plant's main contribution to the northern
environment is likely to be its addition to a growing arctic dump.
These are harsh words, but they are intended to cause comment.
It is poor engineering to spend moi'e money than is really needed
to achieve an objective. On economic grounds, one tends to find
fault with sophisticated treatment plants in isolated northern
situations. Our waste treatment goals should be tailored to the
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9
Lagoons, whether properly engineered or even unprepared,
appear to fill the essential criteria for satisfactory sewage
disposal. With a little common sense they can be sited so that
they are far enough from the settlement to cause little nuisance,
and so that soil slumping and berm degradation are minimized, and
cause no threat to the settlement. If maintained minimally, they
can be in fact so unobtrusive most of the year as to be literally
"forgotten about". And this is perhaps one of the most desirable
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10
PART I I
THE DESIGN OF A SEWAGE LAGOON SYSTEM
Basic Design Considerations
In designing a sewage pond system which will provide accept-
able treatment, we must first understand the unusual characteristics
of the ponds, which are related to the amount of sunlight and the
temperatures which occur in the north.
There is ice and snow cover on the ponds for a much longer
period of time in winter, which reduces the sunlight, so that
the algae cannot photosynthesize. This process is the principal
factor in the reoxygenation of the water in the pond. In addition,
of course, the ice prevents the physical reaerating of the water
by the dissolving of oxygen at the surface. As a result, the
aerobic decomposition processes in sewage ponds in winter are not
significant. Studies of lagoons in Alberta^" and the Mackenzie
2 3
District ' have demonstrated that when the ponds are anaerobic
in winter, there is sedimentation, but little organic decomposition
activity.
In slimmer, the sunlight reaches the surface of the water for
a much longer period of time each day than in the temperate zone.
This results in almost continuous algal metabolism, and although
the metabolic processes may be slower due to the colder tempera-
tures, the longer periods of algal activity more than compensate
for this deficiency. As a result, dissolved oxygen levels of over
200% saturation have occurred in the surface layers of the N.W.T.
lagoons.
It is necessary to consider these two effects in planning a
sewage pond system. Where primary treatment is satisfactory, two
"primary" ponds which provide a few days of theoretical retention
time will be adequate.
When secondary treatment for the effluent is required, a
"secondary" pond is required which will provide 100% storage of
the sewage for a full year. Effluent from the pond would not be
discharged until the aerobic conditions had existed throughout
the pond for a complete summer. Under these conditions, treatment
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11
A new set of criteria should be developed to judge the
effluent from sewage ponds, because of fundamental differences
between ponds and treatment plants. Secondary sewage ponds are
in fact very fertile lakes, and the effluent should probably
be judged by standards which take this into consideracion rather
than by those which have been developed for effluent from
mechanical treatment plants.
The development of these standards should be based on compara-
tive studies of the protection given to water supplies and the
concentration of nutrients maintained in the downstream receiving
waters by both treatment plants and ponds. It would be most
interesting also to have a study done by biologists on the com-
parative effects of the discharges from sewage lagoons and
naturally eutrophic lakes on receiving waters.
Sewage Lagoon Construction Criteria
Dawson and Grainge proposed design criteria for wastewater
lagoons in arctic and sub-arctic regions based on studies by
2 3
Dawson in 1965 and 1966. ' More recent routine examinations of
the operation of lagoons in the Mackenzie District tend to
substantiate their conclusions and recommendations which are
summarized herein.
The basic objective is that the lagoon should provide
effective methods of wastewater disposal without creating objection-
able conditions or public health hazards in the vicinity or
downstream in the receiving water course.
The lagoon should incorporate the following qualities:
1. The lagoon should be structurally sound and aesthetically
acceptable.
2. The operation should be free from objectionable odors or
nuisance conditions.
3. Breeding of macroinvertebrates, such as insect larvae and
adults, worms, etc., should be minimized.
4. Seepage from the lagoon should be prevented if pollution of
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12
Effluent quality of the lagoon must maintain certain
standards:
1. The lagoon must be designed to provide effective removal of
organic material and destruction of harmful biological organisms.
2. The effluent should be relatively free of oils, grease, color
and floating solids.
3. The settleable solid content should be low.
4. Conditions in the receiving water should meet the currently-
accepted standards.
Classification of Lagoons
Wastewater lagoon systems for the Arctic and sub-Arctic
regions will be classified into four types:
1. Single-Cell Long Retention.
2. Primary Short Retention.
3. Secondary Long Retention.
4. Aerated.
The term "secondary long-retention ponds" is used to distinguish
between single-cell and multiple-cell lagooning systems.
Single-Cell, Long-Retention Lagoons
These ponds are most suitable for small installations. The
ponds should allow for variable depth operation. A summer operating
depth of 4 to 5 ft is optimum. However, in winter, the pond will
freeze to depths which vary up to 5 ft. Therefore, the winter
operating depth should be such that there is a 3 ft minimum depth
below maximum ice cover, i.e. from 6 to 8 ft.
The retention time should be 8 to 12 months to allow complete
storage throughout the winter. Now that the equivalent of
secondary treatment is required in Canada, we prefer a full 12-month
retention period. B.O.D. loading may be up to 20 lb of 5-day B.O.D./
day/acre. The pond site should be located a minimum of one-quarter
mile from the nearest residence in a settlement. If practical, the
pond should be situated so that the prevailing low winds blow
across the pond towards uninhabited areas. Ponds also should be
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13
The berms should be constructed of impervious material and
compacted to form a relatively stable structure. A minimum
top width of 10 ft is desirable to permit maintenance vehicle
access. A horizontal to vertical slope of 3:1 is most common
with clay soils. However, steeper slopes can be utilized if
the structural properties of the soil permit. Where wind erosion
or unstable soils are factors, shallower slopes, such as 6:1,
are recommended. A minimum 2 ft summer freeboard is advisable
which can be reduced to 1 ft during winter to increase the storage
volume. The berm should be made impermeable to prevent surface
ponding outside of the lagoon. Following construction, the berms
should be seeded.
To prepare the bottom, all vegetation and organic topsoil
should be removed and the bottom levelled. The bottom should be
made impermeable if water-aquifer contamination, short-circuiting
to a surface stream, or ponding on the surface outside the berms
could occur. In addition, if seepage causes exposure of sludge
banks, sealing is required.
Normally, the lagoon should be square or rectangular with
rounded corners. However, if mixing and circulation is not impaired
a lagoon of another shape may suit the topography and be more
pleasing in appearance and less expensive to construct.
The inlet should extend well into the lagoon so that the
sludge will be distributed by wind-induced currents. Usually the
inlet will be subsurface,and located along the bottom of the pond.
Forcemains should be extended to the center of the lagoon
terminating with an upturn elbow set on a concrete pad. The force-
main must be so designed as to avoid any possibility of the lagoon
contents siphoning back into the lift station in the event of a
check valve failure or anyother mechanical failure. A forcemain
discharging above the surface of the lagoon would be a satisfactory
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14
Gravity mains should extend past the toe of the bernwand
sludge should be prevented from blocking the end of the pipe by
horizontal discharge to a saucer-shaped excavation in front of
the pipe. The bottom of the last manhole before the inlet should
be above the maximum water level of the lagoon. The manhole
should be as close as possible to the inlet so that the inlet
pipe is as short and as steeply graded as possible.
Both overflow and drain outlets should be provided. The
overflow device should be adjustable to permit operation at
depths between 3 and 8 ft.
Primary Short-Retention Ponds
These ponds are suitable for use either by themselves where
an equivalent of primary treatment is required, or with secondary
long-retention ponds. At least two ponds capable of series
operation generally are used. A four-pond arrangement inter-
connected for any combination of series or parallel operation is
preferable/to provide efficient treatment and flexibility of
operation in case of odors.
An operating depth of from 10 to 25 ft is desirable. Deep
ponds conserve heat and help maintain an efficient anaerobic
process. A deep water layer is also provided on top of the
decomposing sludge to prevent the escape of odorous gases.
A two to four-day retention period in each pond is desirable.
A loading from 6 to 9 lb 5-day B.0.D./day/1,000 cu ft is optimum.
Short-retention ponds should be isolated at least one-quarter mile
downwind of the nearest residence. The construction criteria are
the same as for the long-retention ponds with the following
exceptions:
1. The berm slope should be steeper if stable soil materials are
available (i.e. 2:1 horizontal to vertical maximum).
2. Impermeable berms must be provided.
3. For pond inlet structures the inlet sewers should discharge
to a depth of approximately 6 ft. They should terminate well
above the accumulating sludge. A concrete pad and riprapped
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15
4. Short-retention ponds will overflow all year long. Therefore,
outlet structures need not be capable of variable depth operations.
The outlet 3hould draw from a depth of approximately 4 ft.
The four-pond system allows flexibility in operation. Three
ponds can be operated in series for several years until the primary
pond is half full of sludge. At this time, raw wastes water can
be introduced into the unused pond in series with the other ponds,
while the initial primary pond is rested. After a long period of
digestion, the sludge can be pumped from the pond used as a
primary cell and then this pond can be returned for service.
Secondary Long-Retention Lagoons
The secondary pond should be designed according to the criteria
established for single-cell lagoons. However, the inlet arrange-
ment is usually a simple valved overflow pipe from the short-
retention pond. The combination arrangement of short-retention
and long-retention ponds is the preferred method of lagoon sewage
treatment now. In addition, we tend to opt for a full 12-months
retention time in long-retention ponds.
Aerated Lagoons
Aeration of deep short-retention lagoons allows increased
loadings with maintenance of aerobic conditions and equivalent
efficiency to secondary treatment.
We recommend a minimum depth of 10 ft, a maximum of 20 ft,
a retention time of 30 days and a B.O.D. loading of up to .6 lb
5-day B.0.D./day/1,000 cu ft.
Compressed-air introduction of oxygen is preferable to
mechanical aeration since ice buildup in the latter might be
excessive unless care is taken to avoid this. Construction of
the lagoon should conform to the criteria established for short-
retention ponds. Since aerated lagoons are completely in the
aerobic state, isolation of the ponds is not critical as with
long-or short-retention ponds. A minimum of 300 ft from the
nearest residence and 100 ft from the nearest roadway should be
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16
Wastes should be discharged by the forcemain or gravity inlet
to a minimum depth of C ft. Outlets should be designed to draw
from a depth of 3 ft below the liquid surface during summer and
C ft below the surface during the winter. Pond drains should be
provided so that the cells may be emptied completely if necessary
for maintenance. Multiple pond installations are desirable and
should be designed to allow either series or parallel operation.
Soils Conditions and Berm Construction Methods for Lagoons in
Permafrost Regions
We have no experience with lagoon construction in very
unstable permafrost conditions. However, some conclusions may be
drawn from various other investigations of permafrost.
Mackay^'^'^ defines the distribution of ground ice in perma-
frost areas, and how it was formed. He points out that a high
percentage of the massive ice deposits found in the western arctic
were formed through a process of "ice segregation" in which water
from the unfrozen regions of the soil migrates to the freezing
surface, creating a supersaturated condition in the frozen soil
which contrasts markedly with the saturated or unsaturated
condition of unfrozen soils^. It is these supersaturated soils
that cause nearly all of the problems associated with engineering
and construction in permafrost regions. Should the surface cover
be disturbed, this tends to result in an increase of the mean
surface temperature in the summer months, and hence an increase in
the depth of the active layer .
Increasing the depth of the active layer is not in itself
necessarily a problem. If the upper layer of permafrost consists
of undersaturated material, and is of adequate thickness, then
little or no settlement will result from thawing this layer. If
however, the upper layer of permafrost is supersaturated, then,
upon thawing, the excess water will separate from the smaller
amount of saturated soil and settlement will occur. This is what
is known as "thermokarst", and it is this phenomenon rather than
thermal erosion, which is of chief concern to engineers. Super-
saturated conditions in the upper 5 or 10 feet of permafrost are
"widespread" in the western arctic, and the ratio of excess water
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17
The depth of the active layer in undisturbed ground is
reasonably clearly related to ground-surface cover and surface
soil type. If the surface is removed or disturbed, then from
this knowledge we can predict approximately the new equilibrium
depth of the active layer. From a knowledge of the ice content
of the permafrost at the site, we can then compute simply the
amount of permafrost that will melt to establish the increased
active layer depth.
To summarize, with respect to lagoons, if an area is chosen
which does not intersect any significant surface or subsurface
drainage patterns, thermokarst, rather than thermal erosion will
be the primary disturbance feature. If the lagoon is then bull-
dozed clear, removing the surface cover and the upper foot or so
of the active layer, the worst result one could reasonably expect
would be a settlement of the lagoon bottom some 2 or 3 feet,
depending on the supersaturation of the exposed permafrost. The
excess water released would largely remain on the surface if the
soil is not permeable, forming a typical thermokarst lake.
Gold,and others** warn that disruption of drainage patterns
is likely to have more far-reaching effects. If the lagoon were
sited, for example, on a slope, then the impoundment of water
caused by the berms will create a lake, and new drainage channels,
both of which will supset the previous equilibrium and cause
melting of permafrost. In addition, the flowing effluent may
exert a thermal erosion effect,in addition to thermokarst, which
may cause gullying at some distance from the original construction.
* 6
In many such areas, ice wedges are common, and running water
will bend to move along these wedges as they melt.
For these reasons, it appears logical to site the lagoon in
a flat area where drainage is unlikely to be a problem.
Gold, and others** summarize the available methods for esti-
mating heat transfer in soils and the effects of various construction
such as pipelines or insulating pads on the permafrost. These
* - Ice wedges are vertical sheets of wedge-shaped ice in the
ground which result in the formation of the polygon ground
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18
methods assume numerous simplifications; among them, homo-
geneous soils, simple conduction as the sole form of heat transfer,
uniform moisture content,*and the like. Such conditions are
rarely found in practice, and the authors point out several
limitations to the theory. This paper contains no indication of
detailed methods for estimating undercutting of a linear berm
beside a lake or a lagoon although some simplified theory can
undoubtedly be established that would assist in recommending
lagoon berm designs for permafrost regions. It would be logical
to pursue this study.
On the basis of this limited survey, the following preliminary
recommendations emerge for lagoon siting and design in permafrost.
Lagoon Siting and Design in Permafrost Regions
1. Site the lagoon in a flat or low-lying area, or a natural
depression, where no significant surface or subsurface drainage
paths will be affected.
2. Determine the ice content of the permafrost, and the
existence of any massive ice or ice wedges by taking core samples
under the lagoon site. Make estimates of the extent of thermokarst
and of any predicted erosion effects.
3. The berm designs should contain features which will tend to
aggrade, or raise the permafrost underneath the berm. This will
reduce the annual maintenance that would otherwise become necessary
as the berm foundations slump and erode.
Methods that could be considered are:
(a) Construct the lagoon and berms in late fall, to avoid
thermokarst problems until the following summer.
(b) Ventilate the berms in winter through conduits placed during
construction.
(c) Choose insulating soils or artificial insulating layers to
preserve the frozen foundation.
4. The effluent from the lagoon should be diverted either to
existing drainage channels wherever possible, or to ditches in
unsaturated soils which are free of massive ice deposits.
5. The lagoon and effluent channel should be sited so that in
the event of unforeseen thermal damage, no harm can come to
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19
in the vicinity will occur.
Further Research Required
In addition to the further investigation required to refine the
design and construction criteria for sewage lagoons, research into
the alternatives noted in Part I is also needed.
There are many places in the north where irrigation with
water containing nutrients might be desirable from the point of
producing a more interesting landscape. For example, large areas
of the Arctic are bare ground, gravel or tundra. It would not be
wrong to landscape some of this and make it more interesting
visually by inducing plant growth of some kind in some barren
areas and replacing some of the tundra with grass. Many of the
small communities may be made more pleasant by an improvement of
the landscape around them.
Many settlements in the north border swampland, and usually
the most obvious effluent disposal point is to one of the lakes
in the area. Often too, the swampland is so close to the town that
there is no room for pond construction in the area. There is a
need to define the effects of sewage effluents on swamps and
likewise the effects of swamps on sewage effluents.
Treatment Obtained by Seepage from Ponds
Seepage from sewage ponds may be up to 100%. The treatment
of the effluent which is obtained by seepage through the soil will
vary according to the particle sizes of the soil and the length of
the seepage path. Very little treatment would be obtained when
the effluent seeps only a short distance through the berms and/or
the foundation soil and surfaces a short distance away from the
pond. However, in some cases the effluent seeps through sandy
soil for a considerable distance before it surfaces.
9
A few studies have been made on the extent of the treatment
which will be obtained by seepage of sewage throuqh soil, but the
information has not been evaluated and compiled so that the design
engineer can make dependable predictions about the degree of
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20
It would be worthwhile to make a literature survey of the
subject of treatment obtained by the seepage of sewage through
soil and compile the information in the form of a report. An
actual research project is not warranted because it would yield
too little information considering the time which would be
required for the study.
However, whenever the soils investigation indicates that
there will be a substantial amount of seepage from a pond, then
there should be an assessment by the design engineer of the pro-
bable effect on water aquifers and surface water bodies in the
vicinity.
It would be undesirable from public health and aesthetic
standpoints for the seepage to appear on the surface near to a
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21
PART III
CASE HISTORIES OF LAGOON SEWAGE TREATMENT IN THE MACKENZIE DISTRICT
Long-Retention Lagoons
1. The Town of Inuvik Sewage Lagoon
The northernmost lagoon which we have studied is that serving
Inuvik. Inuvik is situated on the east boundary of the Mackenzie
River, approximately 60 miles from the Arctic Ocean at 68°21'N.
Lat. Originally, the ultimate population of Inuvik had been
estimated to be 1,000 people. The lagoon was required, therefore,
to provide at least a year's retention time for the anticipated
sewage flow equivalent to this population.
The lagoon was built in 1959 by the simple expedient of constructing
a road along the western boundary of a natural depression. The
lagoon does not conform to the usual design criteria for berm con-
struction, bottom preparation, etc. The sideslopes on the three
sides boundaried by the road are 3:1 horizontal to vertical, while
the natural slope on the eastern side varies from 4:1 to 30:1.
Bottom preparation and brush cutting in the lagoon basin were not
attempted during construction because of the swampy nature of the
overburden. Therefore, approximately 60% of the lagoon is covered
with scrub willow and alder and many large trees up to 6 inches
in diameter. At the north end an effluent weir consisting of
removable stoplogs controls the liquid level.
Effluent from the lagoon follows the original drainage course
of the depression to a point of discharge into the Mackenzie River
approximately 4,000 ft downstream from Inuvik. The lagoon is
approximately 43.5 acres in area and averages about 4 ft in depth.
It is 3,200 ft long and from 300 to 700 ft in width.
2
When Dawson studied the operation of this lagoon in 1965
and 1966, the contributing population had already reached 1,500
people. Runoff into the lagoon reduced the theoretical retention
period to about one-half year. Nevertheless, despite the construction
deficiencies and the increased population, the lagoon produced an
85% reduction in B.O.D. from raw sewage to effluent in summer and
a 45% reduction in winter. The suspended solids were reduced by
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22
by 99.9% in summer and 99.8% in winter. The last data which
we have from the latter part of 1968 shows the lagoon still
providing over 85% reduction in B.O.D. with the contributing
population approaching 2,000. The contributing population is
now close to 3,000, but the lagoon is still apparently providing
yeoman service. There is a slight odor problem for a short period
in spring which affects some houses which have been built very
close to the lagoon.
The mean annual temperature at Inuvik is only 16°F. The
average temperature at Inuvik rises above 32°F for only 4 months
of the year, i.e. June, July, August and September, as compared
for example, to the 7-month periods in the prairie provinces
where lagoons are common. This is particularly important, for
during the ice-covered season light is excluded from the lagoon.
Precipitation is very light in Inuvik being only a little
over 9 in a year. A feature of the climate which favors lagoon
treatment is that during the 4 summer months the daily temperatures
at Inuvik are not much lower than in the prairie provinces.
Furthermore, the incident solar radiation is very close to that
received in the prairie provinces, and for most of the open water
period the sun shines for almost 24 hours per day.
2. The Town of Fort Smith Sewage Lagoon
Fort Smith is situated on the west bank of the Slave River
just north of the Alberta-N.W.T. boundary, which is the 60th
parallel.
The lagoon serving this town is an engineered design and
well constructed. The lagoon is square in shape, 10 acres in
area and with a common usual depth of 4 ft. The inside berm
slopes are 4:1 horizontal to vertical, and the exterior slopes
3:1. It was built in 1960 to serve a population of 1,000 people
on the basis of 100 people per acre of lagoon surface. Currently,
it serves about 2,000 people, receives 3 million imp gal a day
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23
In summer, the lagoon achieves an 87% reduction in D.O.D.,
95% reduction in suspended solids, and significant reductions
in nitrogen, phosphate and methylene blue active substances.
In winter, it achieves a 53% reduction of the B.O.D. and 72%
reduction of the suspended solids. Unfortunately, there are
no bacteriological data.
The sewage is comminuted and pumped to the lagoon. At the
end of the forcemain there is a 100 ft X 100 ft X 2 ft deep pit
in the bottom of the lagoon. A large sludge bank has accumulated
in this pit over the years,and its top surface is now only 1 or
2 in below the lagoon surface.
The forcemain ends in one corner of the lagoon at a point
about 100 ft equidistant from the two sides. It is possibly due
to the location of the forcemain in this position rather than
in the center of the lagoon that the solids have accumulated and
have not been more evenly distributed throughout the lagoon by
wind currents. In summer, the lagoon shows signs of overloading
in that dissolved oxygen is absent or very low throughout much of
the lagoon. Nevertheless, the lagoon is maintaining a very high
level of efficiency. The lagoon is odorous for a short period
in spring but it is quite distant from the town so that there is
no nuisance.
The effluent from the lagoon flows towards the Slave River,
but in summer it percolates into the sandy soil of the river bank
before reaching the river.
In winter, it is probable that the effluent flows under the
snow and finally reaches the river.
3. Fort Smith Airport Sewage Lagoon
This lagoon serves about 85 people who are resident on the
airport complex and approximately 8 other employees and 30 to
40 passengers each day.
The lagoon is square in shape with bottom dimensions of 200 ft X
200 ft, and a maximum depth of G ft with 1 ft freeboard. At the
forcemain inlet there is a 30 ft X 30 ft X 2 ft deep pocket at the
bottom of the lagoon to hold the accumulating sludge. Berm slopes
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24
The lagoon capacity is 1,780,000 imp gal at the
maximum depth which is 6 ft. The lagoon is lined with 6 mil
polyethylene which is protected by 6 in of coarse sand. This
lagoon operates on the fill and draw principle. The full winter
flow is retained in the lagoon long enough during summertime
for stabilization of the contents to occur. Then effluent is
released.
The effluent seeps away into the sandy soil of the woodland
between the lagoon and the Slave River which is about 1/2 mile
west.
The lagoon was built in 1961 for a design flowrate of 8,000
imp gal per day and a retention time of about 7 months. Currently,
the lagoon receives about 5,000 imp gal/day and the retention time
is approximately 12 months.
In summertime, the lagoon supports^ prolific growth of
algae. In the mid-afternoon the lagoon/usually supersaturated
with dissolved oxygen. The lagoon contents showed reductions of
80% in B.O.D. from the raw sewage and 46% for suspended solids.
However, two-thirds of the remaining B.O.D. and most of the
remaining suspended solids are not due to sewage but to the con-
centration of algae in the lagoon liquor. The coliform reduction
is estimated to exceed 99.99%.
Short-Retention Lagoon Systems
1. The Town of Hay River Sewage Lagoon System
The town of Hay River is situated on the south shore of
Great Slave Lake where the Hay River discharges,at a Lat. of
60°50'N.
The lagoon system consists of two deep short-retention cells.
Each cell is square in shape with bottom dimensions of 35 ft X 35 ft
and a working depth of 12 ft. The interior berm slope is 3:1
horizontal to vertical and the exterior berm slope is 2:1. The
cells may be operated singly, in parallel or in series.
The system was built in 1968 and designed for a population
of 1,700 and 45 imp gal per capita per day allowing a retention
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25
serves about 1,600 people, but the water consumption is much
higher than anticipated, and the retention time for two-cell
operation is only 4.4 days.
In the summer the lagoon achieves a 41% reduction in B.O.D.
and 69% reduction in solids. In wintertime, the B.O.D. is reduced
by 43% and the solids by 81%. The slightly lower figures for
summer operation are probably due to the prolific growth of
algae which occurs in the surface layers of these primary lagoons.
Sunny weather results in supersaturation with dissolved oxygen
in the surface layer. Rough measurements of the sludge accumulation
in these primary lagoons indicates that the accumulation rate is
about 9.4 cu ft/1,000 persons/day. This compares with the accumu-
lation rate found by Dawson^at Yellowknife of 12.9 cu ft/1,000
persons/day. Higo^found an average accumulation of 7.6 cu ft/
1,000 persons/day in 4 Alberta ponds.
The effluent flowsfrom the lagoons approximately 4 miles
through swampland to Great Slave Lake. The effluent is drawn
from a depth of 4 ft in the lagoons and is usually devoid of
dissolved oxygen. In summer, the drainage into Great Slave Lake
from the swamp, including the sewage effluent,has a dissolved
oxygen of 5.6 mg/1, a B.O.D. of 2.2 mg/1, suspended solids of
16 mg/1 and very low nitrogen, phosphate and methylene blue active
substance levels. These reductions cannot be accounted for by
dilution in the drainage from the swamp area. It must be assumed
that there is considerable uptake of nutrients in the swampland
and further stabilization of the organic content of the sewage
effluent.
2. The Hamlet of Pine Point Sewage Lagoon System
Pine Point is situated 4 miles from the south shore of Great
Slave Lake about 60 miles east of Hay River at a Lat. of 60°50'N.
The lagoon system, which was built in 1963, although based
an
on our recommendation for/anaerobic lagoon system, does not meet
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26
The lagoon consists of two cells in scries. The first
cell has 384 ft X 148 ft bottom dimensions, a working depth of
6 ft and a 3 ft freeboard. An overflow channel in the berm
limits the depth. Interior berm slopes are 3:1 horizontal to
vertical and the berm is 10 ft wide at the top. There is a
wedge-shaped sludge pocket in the bottom of the lagoon at the
raw sewage inlet. The pocket is 50 ft X 50 ft X 2 ft deep at the
inlet side. The cell has a capacity of 2.5 million imp gal or
401,000 cu ft and a surface area of 1.77 acres at a liquid depth of
6 ft..
Raw sewage flows into the first cell at the middle of one long
side. Effluent is drawn from the bottom of the lagoon in the
middle of the other long side at a point directly opposite and
only 125 ft from the inflow.
The second cell is 675 ft X 50 ft at the bottom and has a
working depth of 3 ft. The freeboard declines from 6.5 ft at the
inlet to 0 at the outlet. The sideslopes are 2:1. The cell has
a capacity of 700,000 imp gal or 112,2 00 cu ft and a surface area
of .97 acres at a liquid depth of 3 ft. This cell is an excavation.
It was designed as an effluent channel to keep the outfall from
the first lagoon icefree.
In 1970, the system served 900 persons and
received an average daily flow of 135,000 imp gal allowing a
retention time of 18.5 days in the first cell and 5.2 days in
the second cell. There is considerable short circuiting between
the raw sewage inlet and the outlet to the second cell. During
the summertime the B.O.D. was reduced only 30% in the raw sewage
to the effluent and the suspended solids only 15%. However,
the second cell contained a heavy growth of algae which contributed
in a large part to the high B.O.D. and suspended solids levels of
the effluent. Methylene blue active substances were reduced by 91%.
In winter, by contrast, the overall B.O.D. removal was 46%
and the overall suspended solids reduction was 82%. These reductions
are due entirely to sedimentation and to no interference from algae
growth. Because of the short circuiting, the second cell receives
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27
layers of the first cell. Therefore, the reductions in the
second cell are apparently considerably lower than the reductions
in the first cell.
The first cell is generally aerobic over its whole surface
during the summer, but the second cell is generally anaerobic,
and there is some odor problem which is accentuated by the high
sulfate concentration in the Pine Point water supply. In the
anaerobic condition the sulfates are reduced to sulfides by a
group of organisms which can utilize the sulfates as a source
of oxygen. Some of the sulfides are released to the atmosphere
as the foul smelling gas hydrogen sulfide.
The effluent drains away to inaccessible swampland and may
eventually reach the Little Buffalo River, about 30 miles south-
east of Pine Point.
Combination Lagoon Systems
1. The City of Yellowknife Lagoon System
Yellowknife is situated on the north shore of Great Slave
Lake at a Lat. of 62°28'N.
The Yellowknife lagoon was originally a shallow slough
called Niven Lake. Because of the rocky terrain this was the
only available location for a sewage lagoon. A concrete dam
was constructed across the natural outlets from the lake at the
northeast and thereby increasing the pond area to 21 acres and
deepening it to a surprisingly uniform 3.2 ft at overflow level.
This lagoon system is currently the only combination system
in the N.W.T. Prior to 1961, the sewage was treated in a
mechanical primary treatment plant and the effluent was pumped
into Niven Lake (the main sewage oxidation pond). During 1961
the mechanical treatment plant was bypassed and the raw comminuted
sewage was pumped directly to Niven Lake. At this time, the
population of Yellowknife was 3,245. A 1962-63 study showed
that the sewage was being treated effectively in the oxidation
pond. However, there were sludge banks emerging from the oxidation
pond from which objectionable odors were emanating. During 1964 a
deep primary pond was constructed with dimensions 90 ft X 50 ft X
3 .
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28
that the sludge was being confined to the primary pond and
this resulted in the stabilization pond operating much better.
The color of the main pond became dark green instead of greyish,
the odor was reduced and there were no emergent sludge banks.
The current population of Yellowknife is close to 7,500
people. Sludge accumulates rapidly in the primary settling pond
and is removed from time to time by draglines. The 1966 study
3
by Dawson shows theoretical retention times of .6 days in the
primary pond and 4 9 days in the main pond - Niven Lake.
The combination system was producing a B.O.D. reduction
73% in summer and 60% in winter, and a solids reduction of 91%
in summer and 98% in winter. Coliform bacteria were reduced
by 99.99% in summer and 97.7% in winter.
More recent studies show that the theoretical retention
times have been reduced to .3 days in the primary pond and 26
days for the main pond. The B.O.D. reductions aiE 59% in summer
and 39% in winter.Owing to a very high algal content in the
summer there was no apparent suspended solids reduction.
In winter, however, the suspended solids were reduced by
69%. High levels of dissolved oxygen were maintained in the
main pond in the summer. In fact, the water was often super-
saturated with dissolved oxygen. Even under ice-cover in April
there was dissolved oxygen present in the main pond. Although
actual figures are not available, there was apparently a very
high reduction in coliform bacteria. The effluent from the pond
discharges to Back Bay of Yellowknife Bay. Although Back Bay is
a relatively stagnant water body, the bacterial levels are con-
sistently below the accepted criteria for receiving waters.
No objectionable odors were noticed around the primary
or stabilization ponds. There is a slight septic odor emanating
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2 i)
The natural slopes of the lake are choked with bullrushes
and other emergent aquatic vegetation, but most of the pond is
free from emergent growth.
It is now anticipated that Niven Lake will be filled in
eventually,and then used for building development in the City
of Yellowknife which is expanding rapidly. The consulting
engineers for the City of Yellowknife have recommended the use
of Kam Lake as a new sewage lagoon. This lake is much deeper
and larger and should meet the needs of the city for many years
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REFERENCES
30
1. Higo, T.T., "A Study of the Operation of Sewage Ponds in
the Province of Alberta", Publ. Province of Alberta, Dept.
Pub. Health, March, 1965.
2. Dawson, R.N., "Conventional Long-Retention Sewage Lagoon
Treatment at Inuvik, N.W.T.", Pub. Health Eng. Div., Dept.
National Health and Welfare, 1966.
3. Dawson, R.N., "Lagoon Sewage Treatment in the Mackenzie
District, N.W.T.", Pub. Health Eng. Div., Dept. National
Health and Welfare, 1967.
4. Dawson, R.N. and Grainge, J.W., "Proposed Design Criteria for
Wastewater Lagoons in Arctic and Sub-Arctic Regions", Jour.
W.P.C.F. 41, 2, Part 1, Feb., 1969.
5. Mackay, J. Ross, "The Origin of Massive Icc Beds in Permafrost,
Western Arctic Coast, Canada", Can. Jour. Earth Sci. 4, 1971.
6. Mackay, J. Ross, "Disturbances to the Tundra and Forest Tundra,
Environment of the Western Arctic", Can. Geotech. Jour., 1_, 4,
1970.
7. Mackay, J. Ross, "Permafrost and Ground Ice". Paper presented
at Canadian Northern Pipelines Research Conference, Feb., 1972.
8. Gold, L.W., Johnston, G.H., Slusarchuk, W.A., and Goodrich, L.E.,
"Thermal Effects in Permafrost". Paper presented at Can. Northern
Pipeline Research Conference, Feb., 1972.
9. Butler, R.G., Orlob, G.T. , and McGauhey, P.II. , "Underground ,
Movement of Bacterial and Chemical Pollutants", Jour. Amer.
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TABLE 1. SUMMARY OF OXIDATION POND INSTALLATIONS, MACKENZIE DISTRICT, NORTHWEST TERRITORIES
Tributary
Sewage Flow
Location
Longitude Population Daily Per Capita
i9Pcd
Lagoon Type
Average Loadin
Depth Area lb BOD,,
ft acres
Inuvik
68°21'N.
City of Yellowknife 62°28'N.
Yellowknife Correc- 62°31'N.
tional Camp
Hay River 60°50'N.
Pine Point 60°50'N.
Town of Fort Smith 60°N.
Fort Smith Airport 60°N
1,500(166)190,000
1,900('68)209,000
3,500('66)373,000
6,000('70)699,200
44
1,200
900
2,000
120
1,440
180,000
135,000
100,000
4,500
127
110
110
Single Cell, Long-
Retention .
1 day Short-Ret.
Combi-(
117nation(Long-Retention
Single Cell, Long-
Retention. Following
Ext. Aer. Plant.
150 Two Short-Retention
Cells.
150 Two Short-Retention
Cells.
50 Single Cell, Long-
Retention .
Single Cell, Long-
Retention.
12
3.2
3
12
6
3
43.5
II
0.1
21.0
0.09
0.263
each
1.67
0.75
10
392
586
534
636
1.1
135
113
215
-------
TABLE 1 - (Continued)
Location
Inuvik
**
* *
City of Yellowknife
Yellowknife Correct-
ional Camp
**
Hay River
Pine Point
**
Town of Fort Smith
i
Fort Smith Airport
***
***
Loading
lb BOD5X lb BOD5/
1,000 ft/d acre/d
9
13.5
14.8
17.7
3. 07 513
68
21.5
10
Theoretical
Retention
Time
Days
*
180 Summer
300 Winter^
160 Summer
270 Winter
0.6 & 49
0.3 & 26
52
1.5 Each
17
5.3
110
365
BSD
% Reduction
Efficiency
Solids
% Reduction
Coliform
% Reduction
Summer Winter Summer Winter Summer Winter
91
85
89.5
73
59
41
30
87
80
45
85.3
60
39
43
42
53
21
91
69
15
95
46
90
98
69
81
82
72
56
99.9
99. 99
99.8
97.7
99.99
* - Retention time reduced by surface runoff to lagoon.
** - Continuous effluent discharge.
-------
ALASKA
BEAUFORT SEA
BANKS
fSLANO
AkUWki
\Hobnon /stand
"*7
f McPherson
\rctic Red River
VICTORIA
ISLAND
o r
Bay
Bay
Fort
Franklin,
Port
t/iurst Met !
R/C T
D /
* C if
*e#^/e
Fort Reliance
V,. Fork^Simp* on,
OF
FIGURE
Fort
K EE W A TIN
MACKENZIE
DISTRICT
>er River
Hay Rivep,
Eskimo Point
rort Smith
N W T
100
IOO
-------
|-— io'-o'—*|
//W/SV/AW ¦
SEEDED SLOPES
MID LAGOON
UPTURNED 90 ELBOW
WL.
SLUDGE
FORCEMAIN INFLOW SEWER
CONCRETE SPILL PAD
STANDARD
MANHOLE
f- 10-0'
l-O" FREEBOARD
MID LAGOON
^3' ICE COVERS
' ' ' ' S / * '
SLUDGE
in
CONCRETE SPILL PAD
-------
'//>/////'?/'*
/3 ICE COVER
//////////«//
VALVE BOX A VALVE
STEM EXTENSION
X
GATE VALVE
GRAVITY OUTFALL SEWER
UPTURNED ELBOW
ANCHOR BLOCK —
Figure k. Long-retentI on pond with vatved overflow pipe at
winter operating depth.
W.L.
GATE VALVE
OVERFLOW STRUCTURE WITH
REMOVABLE STOPLOGS
Figure 5. Long-retentI on pond with variable depth overflow
-------
-O FREEBOARD
lO-O-
—7WC
W.L.
SLUDGE
CONCRETE SPILL PAD
RIP RAP
Figure 6. Short-retentI on pond - typical forcemaln Inlet.
OVERFLOW
POND No. I
SLUDGE
POND No 2
GATE VALVE
VALVE BOX
Figure 7. Short-retentI on pond - typical overflow between
series ponds.
(fair
-------
OVERFLOW STRUCTURE
W.L
-—VALVE BOX
GATE VALVE
2*x I" GROOVES
2x6
STOPLOGS
-Hj-
o
W.L.
'INSULATED COVER
c
-REIN. CONCRETE
i i
i i
i I
i i
i i
u
~
. . ' u^-
1
FLOW THROUGH SECTION
OVERFLOW STRUCTURE
Figure 8. Short-retentJon pond - variable depth overflow from
pa ra1 lei ponds.
-------
EFFLUENT
N
RAW SEWAGE INLET
FIGURE 9
INUVIK SEWAGE LAGOON
SCALE fslOOO*
EFFLUENT
SECONDARY LAGOON
PRIMARY LAGOON
RAW SEWAGE INLET
FIGURE IP
NIVEN LAKE, YELLOWKNIFE SEWAGE LAGOON
-------
'8
Outlet
¦ I .1.1 .1 .i t\ ,nt '
^'1' I ') '11 f ¦) 'I' I M 11 'i'l'( 'I 'I 'I 'I 'llV'l 'I')'
<3>
<3>
Sludge
bank
\
CD
//ii.).i,I. /, i. iii. 11111,1.1.1.1. !¦ 111.111,1.1,111111/111 fit.
11'i1)11'iti'i 11'I'i'i1 t'l1 iF)'r>¦ i'v it r im'iti'it
-Bcrm Interior slopes 4:1
exterior slopes 3 :1
Pocket In sewage lagoon
'lOO'x lOO'x 2' deep
Influent
forcemain
700'
FIGURE II
TOWN OF FORT SMITH
SEWAGE LAGOON
Scale l*a 200'
Sampling point* thus (§)
-------
FIGURE 12
AIRPORT LAGOON, FORT SMITH NWT
Berm slopes 1: 3
>S\ I i I i 1 i i i I i 1 ) 1 i I i 1 i 1 i 1 I 1 1 f i I i 1 i \ i I I 1 i 1 i i i t 1 1 ) I '
ni1 rrrrri11 !r rr rrri ti 'riTki
&
Influent
I —
i deep sludge pocket
\
—3Cf-l-
*0
\ V
/ \
\
2 layers of 6 mil
polyethylene IO'xIO'
-200'-
i I I I i I i 1 I I I I < I I ll M I I I i I I I I
(M
m
Overflow
Drain
^Xl11' r I' I M'l '11 I11 M'I'I 'I '| M M') ')'! VI1 l'l\
PLAN
scale l"= 50'
Valve box
6670
Jnfluenl forcemoin/ f r^ximpost
Bottom lined with 6" coarse sand
over 6 mil polyethylene
Elev. 660-0
AWAUJ
SECTION A-A
horizontal scale I = SO'
vertical scale l"= 20'
-------
figure: 13
TOWN OF HAY RIVER NWT SEWAGE LAGOON
133'
39' 4 35' + 39' H IO' —
Bcrm Interior slopes 3:1
. exterior slopes 2:1
Outlet drain structure
«n ®
m —
Distribution M.H.
Lagoon drain
ditch
¦30-
Outlet drain structure
PLAN
scale l"o 40'
Distribution M-H-
2'i std golv. pipe vent
e'-549,0
10" gate valve
w I. 54I.O
el 53B.O
el. 535.0
IO"$ inlet pipe
SECTION A-A
horizontal scale l"o40'
-------
N
I GREA T SLAVE LAKE
INDIAN \
y ILL AGE
OLD
TOWN
/J "EST
/CHANNEL
VILLAGE
Sample point
VALE
Sewage tank
truck disposal
Sewage
lagoon
Sample
point
Garbage
dump
FIGURE 14
TOWN OF HAY RIVER
-------
2/
27'
Overflow channel
X>o**
r
2' deep
sludge
pocket
Berm interior slope 2:1
_*o_
in
MX.
MK
PLAN
scale l"= IOO'
First cell
IM
Berm interior slopes 3.1
exterior slopes 25.
FIGURE IS
HAMLET OF PINE POINT NWT SEWAGE LAGOON SYSTEM
Sampling point thus Q)
el. 7SO.O
el 747.0
^ Rock riprap
(-\ to 5* ea side
C--,—01 P'Pt
>imt74Q.
el 743.Q
SECTION THRU CENTRELINE OF LAGOON SYSTEM
horizontal scale f=IOO'
vertical scale fslO"
d.73B.S
Grovity^^
inflow sewei
IO* drainage
valve
Rock riprap
to S* eo side
of, pipe
ml 732-O
/VAAVWV/AVV/AW
sa
118'
675*
8 Cf
SO'
------- |