•• • .
FEDERAL WATER-POLLUTION CONTROL ADMINISTRATION
NORTHWEST REGION, PACIFIC NORTHWEST WATER LABORATORY
HOUSEBOAT WASTE CHARACTERISTICS
AND TREATMENT
APRIL 1968
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HOUSEBOAT WASTE
CHARACTERISTICS AND TREATMENT
Prepared by
B.D. Clark
Technical Projects Branch
Report No. PR-6
U. S. Department of the Interior
Federal Water Pollution Control Administration
Northwest Region
Pacific Northwest Water Laboratory
Corvallis, Oregon
September 1967
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ACKNOWLEDGHENTS
The assistance of the following groups and individuals is
gratefully acknowledged:
1. Mr. Terry Pettus and Hr. King of the Seattle
Floating Homes Association
2. Mr. Ray Mills
3. Mr. Ray DeFir
4. Mr. Alex Gilbert, City of Portland Water Bureau
5. Mr. Ralph Baggerly, Hershey Sparling Co.
6. Mr. Fred Repp, Master Equipment Co.
1
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DEF INITIONS
BOD 5 -- Five day, 20°C biochemical oxygen demand
COD -- Chemical oxygen demand
Tot. Kjeld. Nit. -- Total Kjeldahl nitrogen which includes all
organic and ammonia nitrogen as N
Tot. P0 4 -- Total phosphate as P0 4
Ortho P0 4 -- Soluble, ortho phosphate as P0 4
TGO -- Total grease and oil
TS -- Total solids
TVS -- Total volatile solids
SS - - Suspended solids
VSS - - Volatile suspended solids
gpd -- gallons per day
gpcd -- gallons per capita per day
11
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TABLE OF CONTENTS
I. INTRODUCTION
A. Authority
B. Objectives and Scope
C. Study Area
II. SUMMARY OF FINDINGS AND CONCLUSIONS
A. Findings
B. Conclusions
Page
1
1
1
2
3
III. WASTE QUALITY CHARACTERISTICS
A. Location
B. Methods
C. Results
D. Discussion
V. TREAT €NT OF HOUSEBOAT WASTES
VI. BIBLIOGRAPHY
. *
5
7
10
10
26
33
. S
IV. WASTE QUANTITY
CHARACTERISTICS
A •
Location
18
B.
Methods
19
C.
Results
19
D.
Discussion
21
i-Li
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LIST OF TABLES
Page
I Moorage Inventory Results 6
2 Average Daily Houseboat Was tewater
Characteristics 11
3 Per capita Houseboat Waste 12
4 Variation in Daily Houseboat Wastewater
Quality 13
5 Ratio of Per capita Land Residential Waste
to Per capita Houseboat Waste 16
6 Houseboat and Moorage Water Use 20
7 Houseboat Moorage No. 1 Water Use 22
8 Houseboat Moorage No. 2 Water Use 23
9 Houseboat Moorage No. 3 Water Use 24
iv
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LIST OF FIGURES
No. Page
1 Sampling Apparatus 9
2 Pneumatic Ejector Test Assembly 27
V
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I. INTRODUCTION
A. Authority
The Pacific Northwest Water Laboratory of the Federal Water
Pollution Control Administration, Northwest Region, was requested by
the Oregon State Sanitary Authority, letter dated January 19, 1966,
to conduct a study on houseboat wastes leading to methods for their
collection and treatment.
The Federal Water Pollution Control Act, P.L. 84-660, as amended,
provides Federal authorization for State assistance studies.
B. Objectives and Scope
Houseboat and moorage wastewaters are essentially domestic in
nature and as such will require adequate treatment prior to discharge
to any watercourse. In order that treatment facilities may be properly
designed for strengths and flows encountered from moorages and houseboats,
two studies were conducted to determine the average houseboat wastewater
strength and volume and the waste flow characteristics from moorages or
groups of houseboats. On this basis, criteria are suggested for considera-
tion in the design of treatment and pumping facilities for wastes from
individual houseboats and inoorages.
C. Stu4yArea
The study area for this report included the States of Oregon and
Washington. Two houseboats were sampled continuously, each for a
two-week period, to determine wastewater characteristics.
The average moorage wastewater quantity was determined by recording
water use continuously at three moorages in the Portland, Oregon, area.
—1—
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II. SUNMARY OF FINDINGS AND CONCLUSIONS
A. Findings
1. Houseboat wastes were found to be more concentrated than
normal municipal sewage but less concentrated than the wastes from
individual land residences with two or three children.
2. The average per capita BOD 5 and per capita SS in the house-
boat wastes is 43 ± 3 (957. confidence limits) gm/day and 34 ± 7.1
gm/day, respectively. Both of these values are significantly less
than values normally used in the design of wastewater treatment
facilities. Average per capita BOD 5 and SS reported for several land
residences, each with several children, more closely agree with
standard design values.
3. The average per capita TGO in the houseboat waste is
17.4 ± 7.7 gm/day. This value is higher than normal domestic sewage
and waste from the average land residence.
4. Maximum houseboat wastewater concentrations occur between the
hours of 2100 to 2300 and 0700 to 0900. These periods account for
30 to 43 percent of the total daily waste.
5. The average wastewater contribution from houseboats was
approximately 62 gallons per capita per day (gpcd).
6. The minimum 3-hour waste flow for an individual houseboat is
0 gpcd while that for a moorage varies from 3 to 15 gpcd.
7. The maximum 3-hour flow noted for an individual houseboat
was 700 gpcd. For a moorage with 18 houseboats it was approximately
275 gpcd.
-2-
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8. The waste discharge pattern from houseboats is similar to
that generally reported for municipal wastes with peaks occurring at
niealtimes and little use during bedtime hours.
9. Approximately 87 percent of the houseboat waste occurs in
an 18-hour period from 0600 to 2400, giving an average daily 18-hour
per capita flow of approximately 75 gpd.
B. Conclusions
1. Small submersible centrifugal pumps preceded by uiaceration
will pump houseboat wastes without problems when occupants are informed
that rags and stringy material should not be discharged to the sewer.
2. A small pneumatic ejector for use on an individual houseboat
was designed and tested on a houseboat. The unit was found to operate
satisfactorily without difficulties for a period of approximately 8
weeks.
3. Small extended aeration biological treatment units offer a
practical means of economically providing secondary treatment for
houseboat wastes. A study made in Canada indicates the applicability
of these units for individual home application.
4. Use of conventional design values of 0.17 pounds (77 gin) of
BOD 5 and 0.2 pounds (90 gin) of SS per capita per day would provide
a conservative design of biological treatment facilities for houseboat
and moorage wastes.
5. The average daily 18-hour per capita flow of 75 gpd with a
minimum retention time of 24 hours should be used in hydraulically
-3-
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sizing treatment aeration tanks. A tnaxifnum 3-hour flow rate of 700
gpcd should be used to size settling compartments and inlet-outlet
devices.
6. The alkalinity contributed by the houseboat may be insufficient
to maintain optimum pH conditions in aerobic biological treatment units.
Addition of a buffering solution may be necessary.
-4-
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III. WASTE QUALITY CHARACTERISTICS
A. Location
In order to select representative houseboats for sampling, it
was first necessary to characterize houseboats on the basis of number
of people per boat, typical numbers of fixtures, and living habits.
To do this a survey was conducted at 10 moorages, 9 in the Portland,
Oregon, area and 1 in Seattle, Washington. The survey included 308
houseboats or approximately 25 percent of all houseboats in the States
of Oregon and Washington. Results of the survey indicated an average
population of less than 2 persons per houseboat and slightly over
1 bedroom per houseboat. Approximately half the houseboats have
washing machines and less than 20 percent have dishwashers. Only
one houseboat was found with a garbage disposal unit. The average
number of fixture-units per houseboat, based on the National Plumbing
CodeO-) designation is eleven.
Regarding the resident population living on houseboats, it was
found that most residents could be grouped in one of two categories:
(1) an older group, generally retired, that occupied the houseboat
nearly full time, and (2) a working group composed of childless
couples and single men and women. Table 1 gives the results of the
survey.
Two houseboats, both with complete plumbing systems suitable
for installing sampling equipment to determine waste characteristics,
were selected in Seattle, Washington. The Floating Homes Association
-5-
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Table 1
l4oorage Inventory Results
?IOORAGE
DATE OF
SURVEY
HOUSEBOATS
PEOPLE
BATHROOMS
WASHING
MACHINES
DISH..
WASHERS
GARBAGE
DISPOSALS
PORTLAND, OREGON
Oregon Yacht Club
Suttie Road Noorage
Sauvies Island 14oorage
Ski Dock Moorage
Hayden Island Moorage
Wuerth Moorage
Waterly Lane
Portland Rowing Club
Standard Moorage
SEATTLE, WASHINCTON
Freeman’s Moorage
8/66
11/66
8/66
11/66
9/66
11/66
8/66
8/66
10/66
10/66
31
10
40
22
103
14
18
17
2
51
68
16
60
40
185
29
31
35
6
103
31
10
42
22
105
28
25
20
3
52
30
4
10
1
64
7
10
6
0
17
15
0
2
0
28
2
7
0
1
0
0
0
1
0
0
0
0
0
1
0
TOTALS
308
573
338
159
55
2
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of Seattle made the arrangements with owners of the two homes to
cooperate in the study.
Houseboat No. 1 was owned by an older couple who spent most of
their time aboard their home. The wife was home during the entire
period of this study while the husband was generally away during the
middle of each weekday. Water-using fixtures included a kitchen sink,
1 bathroom with water closet, sink and combination tub and shower, and
a clothes washer. The home was sampled by collecting daily composite
samples during the periods 2100 to 0900; 0900 to 1300; 1300 to 1700;
and 1700 to 2100. The water supply to the home was sampled daily
at 1300. Sampling began at this home on April 28, 1967, and was
completed on May 13, 1967.
Houseboat No. 2 was owned by a working couple. Both were away
from the houseboat during the work-week from 0800 to 1700 but home
on weekends. Water-using fixtures included the same as those for
Houseboat No. 1, plus a dishwasher used approximately once every
3 days. This houseboat was sampled by collecting composite samples
three times daily during the week and five times daily on weekends.
Sampling began on May 16, 1967, and was completed on May 30, 1967.
B. Methods
Composite samples were collected from both houseboats by attach-
ing a sump and pump to the houseboat sewer and pumping all wastes to
a storage tank. Each time a sample was collected, the contents of
the storage tank were measured, mixed, a sample collected, and the
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tank then drained and rinsed out to receive the next sample. To obtain
a representative, well-mixed sample, the raw waste passed through a
food grinder which was activated by a flow switch in the sewer. A
5/8-inch water meter was attached to the water line serving each
houseboat and read each time a sample was collected.
Figure 1 illustrates the sampling equipment used, and the wiring
diagram for the food grinder flow switch.
Samples were stored in an ice chest until the last daily sample
was collected. They were then delivered to the local bus depot where
they were shipped to the Pacific Northwest Water Laboratory at Corvallis,
Oregon, for analysis. The maximum elapsed time between first sample
collection and start of analysis was 23 hours.
Each sample was analyzed according to the latest edition of
Standard Nethods 2 for the following parameters:
Volatile Solids (Total, dissolved, suspended)
Fixed Solids (Total, dissolved, suspended)
Chemical Oxygen Demand
Biochemical Oxygen Demand
Chlorides and sulfates
Alkalinity
Detergents (MBAS)
Total grease and oil
Revised methods of analysis were used for organic and ammonia
nitrogen and total and ortho phosphates. The description of these
methods can be supplied upon request.
Samples of the water supply to the houseboats were collected once
daily and analyzed for the parameters listed above. Corrections were
then made to the wastewater sample results so that all data reported
are the net discharges due only to the waste.
-8-
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55 Got.
Storage Tank—
(See Detail
Be tow)
2’ Swing Check
Va lv e
.8”øx 30” Steel Sump
Coated with epoxy paint
4” Drain Line
Gate Valve
SAMPLING APPARATUS
Flow
SEWER’
Grinder
Sump Pump
Figure 1
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C Results
Table 2 lists values for the individual parameters in the average
daily houseboat wastewater. It gives values for each houseboat sampled
and the combined average for the period of sampling.
Table 3 gives the average per capita contribution of BOD 5 , TS,,
COD, SS, and TGO with standard deviation and 95 percent confidence
limits.
Table 4 gives data on the average daily variation in wastewater
quality from each houseboat in terms of percent of daily total.
D. Discussion
General comparison of the waste strength from the two houseboats
indicates that they varied inversely with the volume of waste contri-
buted; i.e., the wastewater from houseboat No. 1 is less concentrated
than the waste from houseboat No. 2 by a ratio of waste volumes.
Calculation of per capita contributions from each houseboat confirmed
this relation.
Review of Table 3 indicates a per capita BOD 5 of 43 gm/day with
very little variation. This value is significantly less than the
value of 77 gm/day (0.17 lb/day) normally used in estimating the
strength of municipal wastes.
The average suspended solids from the houseboats is 34 gm/day but
shows a wide variance in the samples obtained with a standard deviation
of 15.7 gm/day. The normally-used figure for estimating suspended
solids in domestic wastes is 0.2 lb/day or approximately 90 gm/day.
-10-
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Table 2
Average Daily Houseboat Wastewater
Characteristics
Parameter Houseboat Houseboat Combined
_________ No. 1 No. 2 Average
Chlorides, mg/i 23 31 26
Sulfates, mg/i 12 26 18
Alkalinity, mg/i 72 119 90
Detergents as MBAS, mg/i 0.34 0.96 0.58
Total Solids, mg/i 322 504 393
Total Volatile Solids, mg/i 221 341 269
Suspended Solids, mg/i 139 173 150
Volatile Suspended Soiids, mg/i 113 152 128
Kjeldahl Nitrogen, mg/i 47.8 67.0 55.4
Total Phosphates, mg/i 23.3 49.1 34.0
Ortho Phosphate, mg/i 17.7 21.7 19.3
Chenical Oxygen Demand, mg/I 322 460 377
Biochemical Oxygen Demand, mg/i 164 222 187
Total Crease and Oil, mg/i 66.3 92 76.5
Average Daily Flow, gallons 157 103 130
—11—
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Table 3
Per Capita Houseboat Waste
gm/day/capita
Parameter
BOD 5
COD
Total Solids
Suspended Solids
Grease and Oil
Mean
43
87
94
34
17.4
Standard
Deviation
6.2
39.9
33.9
15.7
17.0
957 Confidence
Limits
t 17.7
15.4
t7.l
7.7
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Table 4
Variation in Daily Houseboat Wastewater Quality
in Percent of Daily Total
HOUSEBOAT NO. 1
Parameter
2100-0900
0900-1300
1300-1700
1700-2100
Flow
35
27
19
19
BOD 5
25
39
19
17
COD
26
43
18
13
Total
Nitrogen
31
43
14
12
Total
P0 4
31
43
14
12
Total
Solids
25
38
19
18
HOUSEBOAT NO. 2
Parameter
2100-0900
0900-1200
1200—1430
1430-1700
1700-1900
1900-2100
Flow
30
24
3
4
23
16
BOD 5
28
29
•
2
2
22
17
COD
34
28
3
1.5
20
13.5
Total
Nitrogen
46.5
8.5
1
5
22
17
Total
P0 4
26
30.5
9
1.5
16
17.5
Total
Solids
28
26
4.5
2.0
20
19.5
- 13—
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The value for houseboats is less than half this standard value.
The average per capita BOD and SS from the homes sampled by
Watson( 3 ) more closely agree with the standard design values.
It has been reported that the average per capita contribution
in feces and urine of total nitrogen, phosphorus, total solids, and
chloride is 15.5, 1.5, 80 and 11 gm/day, respectiveiy.( 4 X 5 ) Compari-
son of these figures with those for houseboat wastes reported in
Table 3 indicates that the urine and feces wastes contributed essentially
all of the total nitrogen and total phosphates and a major portion of
the total solids. This was expected as a result of the low number of
water-using fixtures on houseboats and the type of population residing
aboard most of the homes.
In a study of five Ohio towns, Bunch and Ettinger( 6 ) reported
the average concentrations of various parameters contributed through
water use. These data are compared with an average of the houseboat
data below:
Average Normal 6
Parameter mg/l Houseboat Data Domestic Sewage
COD 377 143
Total Nitrogen 55.4 22.0
Total Alkalinity 90 122
Total Phosphate 34.0 24.3
Ortho Phosphate 19.3 22.8
Total Solids 393 291
Sulfates 18 33
Chlorides 26 56
With the exception of alkalinity, chlorides, and sulfates, the
houseboat wastewater is more concentrated than normal domestic sewage.
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This is attributed to infiltration and storm water contributions to
the normal domestic sewage, as well as certain low strength industrial
and commercial wastes, all of which would dilute the individual house-
hold contribution.
Table 5 compares the per capita land residential waste to per
capita houseboat waste. It can be seen that the land household
contributes significantly more per capita detergent, BUD, COD, and
solids (total and suspended) than the typical houseboat. Per capita
flow, total nitrogen, phosphates (total and ortho) and total grease
and oil contributions all are fairly close with any differences well
within the variability of the data reported.
A major portion of the differences in the per capita detergents,
solids, and organic matter could be explained on the basis of different
volumes of laundry wastes. For example, the three homes studied by
Watson all had 2 or more children and complete home laundry facilities
whereas the houseboats had no children and home laundry facilities
were used only occasionally. Children would tend to increase per
capita laundry water use while decreasing other per capita use such
as that for baths, showers, etc. Analytical data have been reported
on laundry effluent giving a total solids concentration of 1100 mg/l
and a BOD 5 of 300 mg/l. 5 It has also been reported that approximately
20 percent of the total daily flow is due to laundry wastesJ 7 )
Based on data in Table 4 the waste discharge pattern from both
houseboats was quite similar with approximately 30 percent of the
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Table 5
Ratio of Per capita Land Residential Waste
to Per capita Houseboat Waste
Ratio of Average Land Residence (a)
to Houseboat Per capita Wastes
8.9
1.0
1.4
1 • 4
2.0
1.6
2.0
1.7
2.2
0.7
0.9
(a) Average of data from three households reported by
Watson, et al. (3)
Parameter
Detergents
Total Nitrogen
Total P0 4
Ortho P0 4
BOD 5
COD
Total Solids
Total Volatile Solids
Suspended Solids
Grease and O l
Flow
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daily waste load contributed during the hours of 2100 to 0900.
In general, the variation in waste strength by periods represented
in this study was not as extreme as was expected and, therefore, does
not appear to warrant special consideration in the design of treatment
processes.
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IV. WASTE QUANTITY CHARACTERISTICS
A. Location
It was assumed that the quantity of waste discharged was equal
to the water used at moorages and houseboats. This assumes little or
no consumptive loss. This assumption was checked during the sampling
survey of two houseboats at Seattle and it was found that over 99
percent of the water used was returned as waste. On this basis
quantity characteristics were determined by monitoring continuously
the water use for various periods at three moorages in Portland,
Oregon, and at the two individual houseboats in Seattle, Washington.
Moorage No. 1 had a total of 21 residential houseboats, a combina-
tion houseboat-machine shop, and several boathouses. There was a total
of 55 people residing on the houseboats during the duration of this
study. The population was well mixed as regards working and nonworking
adults and preschool- and school-age children. This moorage was
monitored continuously from April 5, 1967, to May 31, 1967.
Moorage No. 2 had 17 houseboats and one clubhouse with facilities
at the time of the study. There were 33 persons living on the house-
boats, primarily married adults, with only one of the adults working.
This moorage was monitored for the periods August 26-30, 1966, and
October 3-10, 1966.
Moorage No. 3 had 18 houseboats with a resident population of 31
persons. Most of the people could be classed as young married
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couples or single and working. This moorage was monitored for the
periods September 3-10, 1966, and October 22-25, 1966.
Houseboats No. 1 and 2 were described previously.
B. Methods
The water use at Moorage No. 1 was monitored continuously by
installing a 1-inch meter with a transmitter head. This was attached
to a continuous flow rate recording instrument with a 7-day chart.
Data was extrapolated from the charts at 3-hour intervals using a
radial planimeter.
Water use at moorages No. 2 and 3 was monitored by the City of
Portland Water Department for the periods mentioned. Data was
extrapolated from charts provided by the City at 2-hour intervals.
Water use at the two houseboats was recorded by installing a
water meter on each line. The meter was read each time a sample was
collected which was four times daily at houseboat No. 1 and three
times daily during the week and five times daily on weekends for
houseboat No. 2. The waste discharged by each houseboat was
determined by measuring the depth of waste in the 55-gallon barrel
sample collector described previously. The barrel was rated for
depth versus gallons.
C. Results
Table 6 summarizes the average maximum and minimum daily flows
plus hourly variations in water use at the three inoorages and two
houseboats. These data are reported on a gallons-per-capita basis.
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Table 6
Houseboat and Moorage
Water Use
Results in gallons per capita per day
Unit
Houseboats
Moorages
No. 1
No. 2
No. I
No. 2
No.
3
Average Day
78
56
62
61
62
Minimum Day
54
30
53
-
-
Maximum Day
112
142
75
-
-
Mm. 3 hours
0
0
13
15
3
Max. 3 hours
8O
700
103
145
275
Avg. 18 hours
-
-
73
74
78
Mm. Day/Avg.
Day
0.69
0.54
0.85
-
-
Max. Day/Avg.
Day
1.44
2.54
1.21
-
-
18 hours/Avg.
Day
-
-
1.18
1.21
1.26
-20 -
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Tables 7, 8, and 9 present data on the water use at the three
moorages for both weekday and weekend periods.
D. Discussion
As indicated by Ta.ble 6, the average daily per capita water use
at moorages showed little variation with an average use of 62 gpcd.
The average individual houseboat use was 56 and 78 gpcd for the two
homes studied which is close to the moorage average value. These
data agree closely with the figure of 60 gpcd for the average dry
weather waste flow from a single family residence as reported by
Robinsonc 8 The value of 75 gpcd for single family residences
recommended in the Manual of Septic Tank Practices 7 appears to be
a conservative figure for estimating moorage and houseboat wastewater
quantities.
Robinson 8 reports that the flow in a sewer serving 18 homes was
found to vary rapidly from a trace to nearly 400 gpcd and that an
allowance of 3 times the average flow be provided in sewer lateral
design. The maximum 3-hour flow noted for an individual houseboat
was 700 gpcd. For the moorages, this value was 275 gpcd. The ratios
of these values to the average daily flow are 12.5 and 4.5 respectively.
The basic design flow variations used for small army installations
as reported by Babbitt 9 are 70 gpcd for the 24-hour average, 97.5
for the 16-hour average day, 122.5 gpcd for the 4-hour maximum day,
and 210 gpcd for the extreme peak. Data for the moorages generally
fall within this range but is exceeded by the individual houseboats
for the extreme fluctuations.
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Table 7
Houseboat Moorage No. 1 Water se(a)
April 5 to May 31, 1967
WEEKDAYS WEEKENDS
Hour Gallons 7 Total Gallons - , Total
24-3 250 7.5 279 7.5
3-6 173 5.2 203 5.5
6-9 519 15.6 414 11.2
9-12 410 12.3 550 14.8
12-15 448 13.5 560 15.1
15-18 465 14.0 576 15.5
18-21 568 17.0 595 16.1
21-24 496 14.9 530 14.3
TOTALS 3,329 100.0 3,707 100.0
(a)Moorage had 22 houseboats with 55 residents at time of study.
Population mixed as to number of families and number of single
persons.
-22-
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Table 8
Houseboat Moorage No. 2 Water use(a)
August 26-30 and October 3-10, 1966
Hour
24-2
2-4
4-6
6-8
8-10
10-12
12-14
14-16
16-18
18-20
20-22
22-24
— WEEKDAYS
Gallons % Total
105 5.3
81 4.1
96 4.8
114 5.8
256 12.9
180 9.1
226 11.4
175 8.8
107 5.4
192 9.7
253 12.8
195 9.9
1,980 100.0
WEEKENDS
Gallons Total
112 5.5
80 3.9
67 3.3
142 7.0
179 8.8
252 12.4
254 12.5
200 9.8
181 8.9
204 10.0
221 10.9
142 7.0
2,034 100.0
(a)Moorage had 17 houseboats with 33 residents at time of study.
TOTALS
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Table 9
Houseboat Moorage No. 3 Water Use(a)
September 3-10 and October 22-25, 1966
____________________ WEE NDS
Hours ______ ______ Gallons 7 Total
24-2 42 1.8
2-4 72 3.0
4-6 108 4.6
6-8 127 5.4
8-10 399 17.0
10-12 342 14.5
12-14 244 10.3
14-16 302 12.8
16-18 173 9.8 9.4
18-20 225 12.8 9.2
20-22 211 12.0 7.4
22-24 194 11.0 ______ _ 4.6
TOTAL 1,760 100.1 100.0
(a)Noorage had 18 houseboats with 31 residents at time of study.
WEEKDAYS
Gallons Total
44 2.5
67 3.8
123 7.0
248 14.1
130 7.3
120 6.8
152 8.6
76 4.3
222
217
175
108
2,358
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The water use pattern and therefore waste discharge pattern of
houseboat moorages given in Tables 7, 8, and 9, is essentially the
same classical pattern that is exhibited in most texts and studies of
this nature. This pattern is one with peak periods of use occurring
during food preparation and mealtime periods and low use occurring
during the bedtime period.
It was interesting to note the difference in use pattern by type
of population at the moorages. Moorage No. 2 had a family-oriented
population and had a use pattern essentially the same for both weekend
and weekday periods with peak use near mealtimes. Moorage No. 3 had
a population composed mainly of unmarried, working adults and had a
water use pattern reflecting this fact. Weekday use showed little
use during the noon period because most of the population was at work.
On weekends, the pattern indicated a high use between 0800 and 1000
that tapered off through the day. There was no sharp trend following
mealtimes indicative of an unmarried population.
Moorage No. 1, on the other hand, had a mixed population. Its
water use reflected this fact with a pattern somewhat in between that
of moorages No. 2 and 3.
In all three moorages studied, approximately 87 percent of the
total daily use occurred in the 18-hour period from 0600 to 2400.
This figure appears reasonable when compared with data reported by
Babbitt( 7 ) for small populations. He reports a figure of approximately
83 percent in a 16-hour period.
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V. TREATMENT OF HOUSEBOAT WASTES
Treatment of the houseboat wastes can be considered in the same
manner as the treatment of any domestic or municipal wastewater and
would be amenable to any number of processes presently used to treat
these wastes. State and Federal laws in most cases will require a
minimum of secondary treatment and disinfection before the waste can
be discharged to a surface water. This requires essentially that
85-90 percent of the BOD 5 and suspended solids be removed and that
the waste be chlorinated to maintain a residual of 0.5 mg/i after 30-
60 minutes retention.
However, before the waste can be treated it must be moved from
the sewer to point of treatment. In the case of houseboats located
on moving bodies of water such as rivers and tidal estuaries, pumps
will be necessary to move the waste. Gravity sewers could be designed
but in most cases it would require their placement under water.
Two methods of pumping were considered suitable for the individual
houseboat wastewater. These included a small commercially available
centrifugal pump preceded by a inacerating device (see Figure 1) and a
pneumatic ejector which was designed specifically for houseboat
application.
A submersible centrifugal pump preceded by maceration was tested
for a 4-week period on two houseboats in Seattle, Washington, as
described previously. The pump unit worked satisfactorily over this
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period with only one instance of clogging difficulty. This clogging
occurred during the first 3 days of use and was due to a rag which
clogged the pump. The occupants of the houseboat were informed of
the difficulty and no trouble was encountered thereafter. The grinding
mechanism on the pump, though, was a continual source of difficulty.
This was not due to the waste, but due entirely to physical limitations
of the flow switch apparatus. The switch was not sealed completely
and moisture in the air and splashings from the lake shorted the unit
out. This difficulty could be eliminated with proper selection of
equipment and installation.
A pneumatic ejector was tested that was built specifically for
houseboat and individual home application. The unit featured non-clog
check valves, light weight aluminum construction of valve casings, 10
gallon capacity, heavy gage steel tank construction, and no moving
parts. The unit was operated by a small 3/4 hp compressor at a gage
pressure of 60-80 pounds per square inch (psi). The pump was installed
on a houseboat in the Portland, Oregon, area that was rented by a
woman and one child of school age. The pump operated without difficulty
for a period of 8 weeks. ABS plastic pipe was found to be completely
unsuitable for this use. This pipe is brittle and subject to cracking
from impact loads. Schedule 80 PVC pipe was found to be completely
satisfactory and easy to install on an installation of this nature.
An illustration of the pump and compressor is given in Figure 2.
There are essentially three different methods in which the waste
can be treated to meet secondary requirements: physically and/or
chemically, or biologically.
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Compressed Air Inlet
Check Valve
Outlet
Compressor
I
Pressure Sensor
I c.
Non-u iog
Check Valve
Vent
Inlet
Figure 2
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In the case of the houseboat and inoorage wastes an extended aeration
biological process is probably the best suited for this application.
This process involves little mechanical equipment and in areas where
solids wasting in the effluent is permitted, no sludge handling.
Sludge handling costs alone generally represent 50 percent or more
of wastewater treatment costs and the advantage of the extended
aeration process from this standpoint alone is obvious.
The main disadvantage to the extended aeration process is the
operation and maintenance skill required to achieve proper operation.
This is actually true of all treatment processes but more so with
biological processes due to close control required to maintain an
optimum environment for the biological process. Proper operation
and maintenance requires daily attendance. Many of the manufacturers
of the extended aeration units are now offering a service contract
with purchase of their equipment. This type of arrangement, if
conscientiously performed by the manufacturer, should make the small
packaged extended aeration plant acceptable for treating both moorage
and individual houseboat wastes.
Campbell and Smith 10 reported an investigation of individual
household aerobic treatment units in 1962. They installed an aerobic
treatment unit with 560 gallons aeration capacity to serve a family
of 4 individuals. After more than a year’s study they concluded
that similar type units may have wide applicability. The cost is
not much greater than a septic tank and the maintenance no more than
is required for a common household oil burner. The effluent from the
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plant had an average BOD 5 of 80 mg/l and suspended solids of 33 mg/i.
The unit functioned satisfactorily after no—load periods of at least
three weeks. The author has pointed out that the major weaknesses of
the unit were inadequate settling and short circuiting under shock
loading conditions. While the efficiencies reported by Campbell and
Smith do not meet secondary standards, proper settling and hydraulic
design should make the standards attainable.
There are many commercially available units that could be used
for both group and individual situations.
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DESIGN CRITERIA
Based on the data presented previously, the following criteria
are suggested for use in the design of biological systems to treat
houseboat wastes:
1. The organic strength of the waste can be conservatively
estimated by the standard figure of 0.17 pounds per capita of BOD 5
per day. If aeration is provided for this strength, peak flows and
loadings will be provided for adequately.
2. The average 18-hour daily per capita flow is approximately
75 gallons per day and the average number of persons per houseboat
approximately two. This indicates that a minimum flow of 150 gallons
per day be allowed per houseboat. The minimum figure of 600 gpd per
home as suggested by the National Academy of Sciences 1 appears to
be quite conservative for use in the sizing of treatment units for
houseboats.
3. The sizing of settling units and design of weir overflow
rates should be based on the maximum 3-hour flow of 700 gpcd. If
hydraulic storage is provided in the aeration tank, these rates could
be reduced in accordance with flow rates to be expected.
4. The aeration tank should be sized with a detention period
of 24 hours on the basis of design flow or a loading of 20 pounds of
BUD 5 per 1,000 cubic feet of aeration tank, whichever gives the larger
volume. The hydraulic load or detention period will generally govern
for houseboat wastes.
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5. It may be necessary to add additional buffering capacity
to the waste in order to maintain a suitable pH range of 6.5 to 8.5
in the aerator due to the low alkalinity in the houseboat waste.
6. The National Academy of Sciences recommends an air
supply of “not less than 1,000 cubic feet per pound of influent 5-day
ROD. The air may be applied continuously or intermittently.’ t This
would indicate that the average houseboat would require an air supply
with a capacity of 200 to 300 cubic feet per day.
7. There are significant quantities of grease and oil in
the houseboat waste. This will require adequate scum removal facilities
to insure trouble-free operation of any biological treatment unit.
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VII. BIBLIOGRAPHY
1. Report of Technical Committee on Plumbing Standards, Public Health
Service. September 1962.
2. Standard Methods for the Examination of Water and Wastewater, 12th
Edition, APHA, AWWA, WPCF.
3. Watson, K. S., Farrel, R. P., and Anderson, J. L. “The Contribution
from the Individual Home to the Sewer System.” Paper presented
before the annual WPCF Meeting, September 1966.
4. Sunderman, F. W. and Boerner, F. “Normal Values in Clinical Medicine.”
p. 260, W. B. Sanders and Co. (1949).
5. “The Effect of Industrial Wastes on Sewage Treatment.” New England
Interstate Water Pollution Control Commission. June 1965.
6. Bunch, R. L. and Ettinger, M. B. JWPCF 36, 1411 (1964).
7. Manual of Septic Tank Practices . Public Health Service Publication
No. 526, 1957.
8. Robinson, Lloyd R. “Design Considerations for Sanitary Sewer
Extensions.” Water & Sewage Works, July 1967.
9. Babbitt, H. E. Sewerage and Sewage Treatment , 6th Edition, John
Wiley & Sons, Inc. 1947.
10. Campbell, L. A. and Smith, D. K., “An Investigation of Individual
Household Aerobic Sewage Treatment Units.” Canadian Municipal
Utilities, November 1963.
11. Report on Individual Household Aerobic Sewage Treatment Systems ,
National Academy of Sciences, Pub. 586, Washington, D. C.,
1957.
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