May 1981
WASTEWATER TREATMENT BY ROOTED AQUATIC
PLANTS IN SAND AND GRAVEL TRENCHES
Pamela R. Pope
Moulton Niguel Water District
Laguna Niguel, California 92677
Grant No. R-805279
i Project Officer
1 Ronald F. Lewis
i Wastewater Research Division
Municipal Environmental Research Laboratory
: Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROCTECTION AGENCY
CINCINNATI, OHIO 45268
o
M
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
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FOREWORD
The Environmental Protection Agency was created because of increasing
public and government concern about the dangers of pollution to the health
and welfare of the American people. The complexity of the environment and
the interplay between its components require a concentrated and integrated
attack on the problem.
Research and Development is that necessary first step in problem solu-
tion and it involves defining the problem, measuring its impact, and search-
ing for solutions. The Municipal Environmental Research Laboratory develops
new and improved technology and systems for the prevention, treatment, and
management of wastewater and solid and hazardous waste pollutant discharges
from municipal and community sources, for the preservation and treatment of
public drinking and to minimize the adverse economic, social, health, and
aesthetic effects of pollution. This publication is one of the products of :
that research; a most vital communications link between the researcher and ;
the user community. ; :
As part of these activities, this report was prepared to make available
to the sanitary engineering community the results of field tests of a process
developed in West Germany that utilizes reeds and bulrushes planted in trenches
for treatment of wastewater. ; :
Francis T. Mayo, Director
Municipal Environmental Research Laboratory
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ABSTRACT
' The Moulton Miguel Water District of Laguna, California, constructed and
operated an earthen trench system employing rooted aquatic plants for the
treatment of wastewater. Two trenches in series were planted with the reed
Phragmites and the bulrush Scirpus, respectively.
A two-month study using conventional secondary effluent as the trench
influent showed the system was not effective for removal of nitrogen and
phosphorus components.
An 11-month study demonstrated that raw screened wastewater applied to
the trench system at a rate not exceeding 95 m3/d (25,000 gpd) could be .
treated to secondary effluent quality. Spatial requirements were about the
same as for a septic tank system.
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CONTENTS
Page
Foreword iii
Abstract iv
Figures 1 vi
Tables .......... vi
1. Introduction . . 1
2. Conclusions 3
3. Recommendations 4
4. Description of MPI System 5
5. Operational Experiences 11
6. Results and Discussion . 16
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FIGURES
Number Page
1. MPI System at Mouton Miguel, CA 6
2. Elevation View of Filter Trench 7
3. Elevation View of Elimination Trench >...... 9
TABLES ' " "' " ' ~"
Number Page
1. Tertiary Treatment Results for MPI System ~ 17
2. Secondary Treatment Results for MPI System 19
. VI
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SECTION 1
INTRODUCTION
The objective of this project was to evaluate a patented process developed
by the Max Planck Institute (MPI) of West Germany fcr the treatment of indus-
trial wastes, as an energy-efficient method for the treatment of municipal
wastewater. The major goal was to achieve effluents meeting the United States
Federal Effluent Standards by this novel biological treatment process that
uses a minimal amount of mechanical equipment and does not require a great
amount of manpower for normal operation.
HISTORY _ .... . . . .
Dr. Kaethe Seidel, who led a working group at the Institute of Plant
Genetics of the Max Planck Association, is primarily responsible for the
development of this novel biological treatment method. Biological Water
Purification of California, Inc. (BWP) headed by Mr. James E. O'Connor was :
the California sub-licensee for the MPI system; BWP of New York, headed by
Mr. L. Banks, is the general licensee of the patent (U.S. Patent 3,770,623;
November 6, 1973} and has an installation in Long Island, New York.
In May 1976, a joint pilot project was put into operation by BWP of Cali-
fornia and the Moulton Niguel Water District (MNWD), a public agency formed
in 1961 under the Special District's Act. MNWD is engaged in providing
domestic and irrigation water, wastewater collection treatment, and disposal ;
within its geographical service area. The pilot project was located at the ;
3A facility of the MNWD plant in Mission Viejo, California. A daily loading j
of 75 m^ (20,000 gpd) of raw wastewater was used in this study. An EPA Re-
search Grant was applied for based on initial data collected during this ;
study. The grant was awarded in August 1977 with MNWD as the grantee and ;
James E. O'Connor of BWP of California as the Project Director. The project
period was to be from September 15, 1977 to September 14, 1979. ;
The construction of new trench systems was planned to begin in mid-
January and operation was expected at the beginning of March. Because of
excessive rain, major construction did not start until the end of March 1978,
and was completed in the beginning of June 1978.
The first two months of the project were devoted to testing the MPI sys-
tem as a tertiary treatment process. This was done upon request by interested
parties associated with MNWD. This phase of the study lasted from the end of
June 1978 until the end of August 1978 with an average daily flow of 95 m^d
(25,000 gpd).
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Starting in mid-September, raw wastewater was used as influent for the
system to evaluate capability for secondary treatment. Testing was to con-
tinue for one year in order to determine the effects of seasonal changes on
the development and performance of the MPI system. Flow was started at 57
(15,000 gpd), and it was hoped that a maximum flow of 190 nvVd (50,000 gpd)
could be achieved by the end of the project.
The project was terminated short of the September date due to the death
of the Project Director, James E. O'Connor.
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SECTION 2
CONCLUSIONS
(1) Nutrient concentrations were not reduced to low enough levels in the
effluent to consider the MPI system as a tertiary treatment system.
(2) The MPI system operated as a secondary treatment system appears to
be an alternative to conventional secondary treatment systems for subdivision
size facilities. The spatial requirements are about the same as a septic
tank system.
(3) The effluent from the MPI system, when operated as a secondary treat-
ment system, met the Federal Effluent Discharge Standards for BODs and sus-
pended solids when the flow did not exceed 95 m3/d (25,000 gpd).
(4) The Phragmites and Scirpys plants grew well in all seasons and all
weather conditions of southern California. _ \
(5) The plants required harvesting approximately every four months; if
left unharvested, they degenerated, collapsed and lay down on the trenches.
(6) The MPI system appears to perform most efficiently with flows of
57-95 m3/d (15,000-25,000 gpd) through the filter trench. A flow of 133 m3/d
(35,000 gpd) lead to a poorer quality effluent and caused operational problems.
(7) Bacteriological tests indicated that disinfection of the MPI effluent
would be needed to meet a total coliform standard of 1,000 per 100 ml.
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SECTION 3
RECOMMENDATIONS -
(1) Further studies should be conducted in other parts of the United
States to determine whether the MPI system can be used in colder climates.
(2) For future pilot plant size or full-scale systems, improved engi-
neering design of the freeboard level in the filter trenches and the method
of applicaiton of the filter trench effluent to the beginning of the elimin-
ation trench may prevent some of the operational problems noted.
(3) A lower loading rate and use of more filter trenches with a longer
period of drying between each cycle an individual filter bed is loaded may
prevent the clogging problems experienced in this study.
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SECTION 4
DESCRIPTION AND OPERATIONAL METHODOLOGY OF THE MPI SYSTEM
The MPI process utilizes higher aquatic plants, such as reeds and bul-
rushes, for the treatment of wastewater. The system consists of two earthen
trenches, lined with impervious membranes, operated in series. The first
trench, designated as the filter trench, removes coarse suspended solids from
the wastewater. The second trench, designated as the elimination trench,
removes dissolved materials from the effluent of the first trench.
The MNWD services a residential area and the wastewater is domestic in
nature. The MPI system, as it was installed at the MNWD 3A facility, con-
sists of two filter trenches and two elimination trenches. Two species of
plants were used for the project, a reed Phr agmites cornmunis in the filter
trench and a bulrush Scirpus lacustris in the elimination trench. Figure 1
is a plan view of the trench system.
The two filter trenches are each 25 m (75 ft) long and 4 m (12 ft) wide
and 1.3 m (4 ft) deep. They are filled with three layers of gravel 150 mm
(6 in) of 50 mm (2 in) gravel on the bottom, 225 mm (9 in) of 19 mm (3/4 in)
gravel as the middle layer, and 75 mm (3 in) of pea gravel above. A 75 mm
(3 in) layer of silica sand covers the top. Figure 2 is an elevation view of
a filter trench. The raw wastewater enters the MNWD 3A facility at the north
side of the plant and is passed through a rotostrainer for removal of large
particles. .
The screened influent flows down an influent channel and is pumped to /
the MPI system at a rate of approximately 8.8 to 9.5 x 10~4 m-Vs (14-15 gpm).
The influent then flows south through a control valve into the east end of
the filter trenches. Every 24 hours, the flow is alternated between the two
trenches. Each filter trench contains a central 150 mm (6 in) plastic pipe ,
with an open slit running its entire length with alternating long and short
smaller 100 mm (4 in) plastic pipes extending from it for even dispersion of
the influent. The wastewater flows down the central pipe through the extend-
ing pipes and onto cement splash pads located directly below. The wastewater
percolates through the trench in a vertical filtering action leaving a sludge
layer on top. The sand filters out the suspended solids while the plant sys-
tem draws moisture and nutrients. Slow drying of the deposited solids occurs
and extensive growth of the plant rootlets and runners aid in the degradation
of the sludge layer on top of the sand. Each trench has a perforated 100 mm
(4 in) plastic pipe extending the entire length of the trench from the surface
to the bottom in a "U" shaped configuration. Flow from the underdrain goes
into this pipe and through pipe extensions and a butterfly valve into a sump.
This pipe not only transports the flow but allows aeration to the bottom
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since it has openings to the surface. The sump is a 1.3 .n (48 in) concrete
pipe 3.3 m (10 ft) in height and is buried 2.6 m (8 ft). The flow is then
periodically pumped by a small 0.25 kW (0.33 hp) pump, activated by a float,
to the elimination trenches.
Normally, this process would be a total gravity flow system, and the
elimination trenches should be placed to facilitate this, but because of site
conditions at this location, the elimination trenches had to be constructed
.90 m (100 yds) north of the filter trenches. The two elimination trenches
are 50 ra (150 ft) long, 4 m (12 ft) wide, and 0.75 m (2.5 ft) deep. They are
divided in the center by a weir, which was designed to allow composite sam-
pi ing in this area and to aid in aeration. Figure 3 is an elevation view of
an.elimination trench. The filter trench effluent enters two 150 mm (6 in)
ACP pipes 4 m (12 ft) long set perpendicular to the trenches at the south
side. The side facing the trenches is open, and the liquid is allowed to
flow out into an area 1.3 m (4 ft) by 4.0 m (12 ft) in a waterfall-like action.
This area is filled with 15 mm (5/8 in) gravel which is held in place by
50 x 100 mm (2 x 4 in) wood baffels. A subsequent observation by BWP of New
York showed that elimination of the baffles gave less operational problems.
The liquid percolates down in a horizontal manner at a level approximately up
to 50 mm (2 in) below the surface of the trenches. The trenches are filled
with 15 mm (5/8 in) gravel with 75 mm of pea gravel on top. The flow passes
through the weir and runs into two standpipes that lead into a sump. The
level of the liquid flow in the elimination trenches is governed by raising
or lowering the standpipes. A valve in the bottom of the weir- allows peri- .
odic draining of the liquid in the lower portions of the trenches. The total
retention time for the entire system is estimated to be 6 hr and 8.5 hr at
flows of 133 m-Vd and 95 m-vd, respectively.
Flow meters were originally installed in the influent and final effluent
lines to measure net loss due to evaporation and transpiration, and for cal-
culation of retention time. The effluent line meter was removed in mid-
August when it was found to be greatly impeding flow from the sump pump. The
nfluent meter clogged immediately upon switching the system to raw wastewater
T mid-September and had to be removed. After this, flow was determined by
ming the filling of a known volume container from a pipe set up for the
.rpose of diverting all the flow for the measurement.
Both type trenches were lined with a Gulf Seal polyethylene liner. All '
effluent from this system was pumped directly back into the Trabuco sewer line
since this was a demonstration study.
The filter trenches were plated with the reed Phragmites by placing root
system shoots evenly spaced about 50 mm (2 in) below the surface of the entire
trench. The four sections of the elimination trenches were planted alternately
with two type plants, so that each trench was plated half with the Phragmites
and half with the Scirpus. By this alternate planting, laboratory results
might show whether or not one plant was superior for dissolved organic pollu-
tants and nutrient removal.
Twelve composite sampling sites were established, eight of these were -
used for daily sampling while the other four sampling sites were available
for special use, if needed.
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SAMPLING AND ANALYTICAL METHODOLOGY
Automatic composite samplers were used with sample intervals at 15 minutes
for the 24-hour composite samples collected from Sunday through Thursday of
each week for the chemical analyses. Daily grab samples were used for measure-
ment of physical parameters. All laboratory results were recorded on daily
sheets and then transferred to montly sheets for each sampling location.
Monthly averages were calculated and recorded.
All analyses were performed according to Standard Methods for the Exam-
ination of Water and wastewater (14th Edition, 1976.American Public Health
Association, Washington, D.C.) as shown below:
Analysis
Total suspended solids (TSS)
Volatile suspended solids (VSS)
Biological oxygen demand (8005)
Chemical oxygen demand (COD)
Ammonium nitrogen (NH4-N)
Kjeldahl nitrogen (TKN)
Organic nitrogen (TKN)
Nitrite Nitrogen (N02-N)
Nitrate nitrogen (NOq-N)
Total phosphorus (TP)
pH (pH)
Standard Methods Procedure Number
208E
208G
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413J
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420
419D
425F -
424
10
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SECTION 5
. OPERATIONAL EXPERIENCES WITH THE MPI SYSTEM
TEST OF MPI SYSTEM AS A TERTIARY TREATMENT PROCESS
Secondary effluent from the MNWD extended aeration plant was introducted
to the MPI system on July 1, 1978, at a loading rate of 56 m3/d (15,000 gpd)
and the flow was increased to 95 m^/d (25,000 gpd) in August.
The newly planted Pragmites planted in both the filter and elimination
trenches grew very slowly. It was not clear whether this slow growth was due
to a lack of sufficient nutrients in the influent, not providing a wet enough
environment in the trench after initial planting, or whether the plants were
extending their subsurface root systems rather than extending their above-
ground growth. In mid-July, the operational procedure was changed so that the
filter trench being used on a particular day was allowed to fill before the
discharge valve was opened. This change seemed to improve the growth rate of
the plants. Some of the Pragmites planted died and these areas had to be re-
planted. The Scirpus in the elimination trench did not experience growth
problems and attained a height of 1.6-2.0 m (5-6 ft) by September. BWP of New
York has found that Phragmites is quite delicate during the first 3-4 months
of growth. They feel that a very wet environment should be provided for about
4 weeks after planting.
Growth of algae within the clear plastic tubes for the composite samplers
and on the weirs in the middle of the elimination trenches recurred and could :
possibly effect the results of chemical analyses. Black plastic tubes which ;
prevented light from reaching the tubing solved the problem with the sampler.
A large sheet of plywood was placed over the area of the weirs and splash zone
to cut down the sunlight and algal growth in that area. i
; In the first months of operation and testing, a major problem was due to i
rodents in the area grazing on the young shoots of the growing plants. This
occurred at a time when the vegetation on the surrounding hills was drying
during the hot summer months. Within a short time, ten to twenty rabbits and
squirrels invaded the trench every evening. Trapping, and later rodent repel-
lents were used to limit the rodent activity. As the plants reached a more
mature height, the problem eased but rodents returned briefly after each har-
vest.
TEST OF MPI SYSTEM AS A SECONDARY TREATMENT PROCESS
Screened raw wastewater was used as the influent to the MPI system in
mid-September at a rate of 56 m^/d (15,000 gpd). The flow was increased to
. _ .. 11
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95 m3/d (25,000 gpd) in October and to a rate of 133 m3/d (35,000 gpd) in
January. It remained at this rate through July.
A thin sludge layer built up and completely covered the filter trenches
by the end of October. At this time, the Phragmites had not spread throughout
the trenches. Algae also started to grow on the sludge layer, and it is
possible that this algae may have contributed to later clogging problems. By
mid-December, algae covered a large portion of the sludge layer and the sludge
layer was not drying or breaking up while the flow was directed into the alter-
nate trench. The problem occurred equally in both filter trenches. Operation
was suspended at this time to consider this problem and to harvest the Phrag-
mites from the filter trenches. The Phragmites had turned brown because of
unusually cold weather and began to lay over because of their mature height
and weight. When the sludge layer was skimmed off a little at a time, it was
found that about 25 mm (1 in) of sludge was deposited on the filter media;
this sludge layer was wet and becoming septic. Below this was a layer of com-
pacted organic matter and fibers that were black in appearance and felt greasy;
this intermingled with the sand, formed an almost impermeable layer. If a
hole was piked through this layer, the liquid held in the sludge layer imme-
diately drained through the remaining sand. The only solution at this time
was to allow the filter trenches to dry after the harvesting, then carefully
rake out the semi- dry top sludge layer. .
In mid-November, another change was attempted to prevent the trenches
from clogging. The pipes which drain the filter trenches run along the bottom
of each filter trench and then into the sump. At this point of emergence into
the sump, there is a tee fitting and the stem of the tee is pointing upward
and open to allow the insertion of a sampling probe. Originally, the tee end;
was capped, but this was found to slow the rate of draining of the filter
trenches and cause clogging of the sampler probe. The removal of the cap did
help draining to be more efficient, but this still did not have any effect on
the status of the continuous sludge buildup and clogging of the trenches' top
layer. Also at this time, the pump which directed the raw wastewater to the
filter trenches developed a serious leak and a new pump had to be installed.
! Subsequent tests conducted in Long Island, N.Y., by BWP of New York, Inc.
showed that the use of four parallel filter trenches to allow increased drying
time and draining the filter trenches three times a week minimized this sludge
problem. ; . ;
j After one month of operation with the screened raw wastewater, the un-
planted gravel of the splash zone at the beginning of the elimination trench .
area began to clog and a temporary ponding occurred. The gravel was replaced
with new gravel but clogging began again three weeks later. Phragmites were
planted in these areas to see whether their root systems would keep the gravel
unclogged; only temporary success was achieved. It was learned that the load
of deposited solids which flowed to the elimination trenches could be handled
better when the filter trench sump was flushed out daily rather than weekly.
12
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Originally, the flow to the elimination trenches was continuous and split
between the two elimination trenches. During the third month of operation,
the flow to the elimination trenches was alternated in a manner similar to the
flow to the filter trenches. The purpose of this was to determine whether a
single elimination trench could be loaded to a rate of 95 m3/d (25,000 gpd)
and whether there was any effect caused by the low or reduced flow to the
elimination trench being rested on that day. Although the drained trench
appeared to become septic, it could not be determined whether this was caused
by the alternate operation or by the fact that retention time was halved at
this flow rate'. At the beginning of December, each elimination trench was
switched back to a continuous flow of 47 m3/d (12,500 gpd. Even with continu-
ous flow, it was found that the elimination trenches should be drained alter-
nately r.very two days to minimize the onset of anaerobic conditions.
As was mentioned before, the project was shut down through the latter
part of December and early January because of the sludge problems, overflow
caused by very heavy rains, pump malfunctions, and the cutoff of raw influent
due to a mechanical problem with the extended aeration activated sludge plant.
When start-up occurred in mid-January, the flow to the trenches was in-
creased to 133 m3/d (35,000 gpd). Even though the filter trenches had been
harvested at the end of December and the thick sludge buildup had been removed,
another heavy sludge layer appeared quickly. This level of feed, 133 m3/d
(35,000 gpd), apparently was more than the filter trenches could handle.
Heavy rains at this time caused further problems. When first built, the filter
trenches had nearly 150 mm (6 in) of freeboard from the gravel bed to the top,
but with the heavy rains and also because of repairs of pipes within the trench,
the sides settled to a level of only 50 to 75 mm (2 to 3 in) of freeboard in
some areas. This prevented an even flow distribution over the trenches, re-
duced the surface holding capacity, and reduced the head available for forcing
the liquid through the filter. Because of the continuous rainy days, the
trenches were unable to dry completely and this may also have contributed to
the problem of clogging and overflow.
j :
| In February, the trenches were operated 24 of the 28 days; surface run- :
off into the trenches caused by heavy rains forced a shutdown the other four
days. Application was changed to two days per trench, instead of alternating
daily, to see if this flow pattern would aid in drying the surface of the idle
trench. No observable improvement occurred; alternating daily between the ]
filter trenches was resumed. The influent flow during the latter part of the
month occasionally dropped to 57-75 m3/d (15,000-20,000 gpd) because of a
clogged influent valve. After this the valve was cleaned out once a week to
prevent this from occurring. The splash zone at the inlet of the elimination
.trenches again began to pond. Once more the gravel was replaced at this point.
J In March the MPI system was only on line 6 out of 31 days because of sur-
face runoff. Influent flow was reduced to 95 m3/d (25,000 gpd) but ponding :
and uneven filtering still occurred in the filter trenches. The walkway i
between the filter trenches subsided to such an extent that there was no
longer any freeboard. The construction company that had built the trenches
was contacted for repair work but could not do the repairs until May. Nearly
150 mm (6 in) of rain fell in March, the wettest month of the study.- The wind
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and rain flattened the bulrushes growing in the elimination trenches. The
plants were harvested at the end of the month.
In April the rain decreased and a flow of 133 m3/d (35,000 gpd) through
*"*"" the MPI system was again attempted. The system was only operated for about
one half of the month because of the surface runoff problem and a blockage
that occurred in the main influent line to the 3A facility. The obstruction
was found and removed after shutting down the system for over one week. Once
more the.gravel was replaced under the elimination trench splash zone because
of clogging. After replacing the gravel in this area this time, that particu-
lar zone was hosed down daily with a high pressure hose to help prevent clogging.
Since the previous harvest in January, the reeds had grown 2 meters (6
ft 6 in). The fastest growing periods corresponded to the months with the
greatest amount of rain and to the periods after harvesting. At the end of
April, the reeds were again harvested and the heavy sludge layer removed.
Harvesting, including cleanup and removal of plants and the -sludge layer
required approximately five working days for the filter trenches and three
working days for the elimination trenches.
The sides of the filter trenches were finally repaired during the middle
of May by placing sand under the sides and walkway of the trench. With the
end of the rainy season and the sides rebuilt, the surface runoff problem
ceased.
! The sampling location of the elimination trench influent was also changed
in May. Instead of alternating the sample line placement in the standpipes
daily, corresponding to the particular filter trench in use, the sample line
was placed directly into the sump. Thus, the sample would reflect the under-
w drain quality during all conditions, including draining.
Problems continued to occur in June. An attempt was made to minimize
the clogging at the splash zone of the elimination trenches by moving back
the berms about 3 meters (9 ft), allowing more area. This helped for a while,'
but did not completely prevent clogging caused by algal growth between and on i
top of the gravel layers. During the first three weeks of June, the weather I
was overcast and damp which made drying of the filter trench more difficult.
With the advent of warmer weather, insect larvae were in abundance in the
sumps and in the samples taken. ; ;
; By the end of June, the reeds in the filter trenches had grown to a
height of 1.5 meters (5 ft). The rate of growth appeared to slow down slightly
with the dryer weather and maturing of the plants. In reviewing the growth
pattern and density of the reeds, one could see areas of the trenches with no
reeds up through the second harvest in December. However, during the rainy
season, growth was prolific and the plants densely filled both trenches by
the third harvest. In the elimination trenches, the bulrush and reeds were
harvested as frequently as in the filter trenches. The bulrush grew very
well through the entire project; the only problems with the bulrush were that
because of their weight, they would not stand up in heavy rain and wind. It
may be necessary to harvest more frequently during these periods. Also in
.... . 14."
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June, when higher temperatures were present, the top half of the plants became
brown.
The project was terminated in July 1979 because of the sudden death of
Mr. James O'Connor, the project manager.
15 _
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SECTION 6
RESULTS AND DISCUSSION
HP I SYSTEM OPERATED AS A TERTIARY TREATMENT PROCESS
The results of the analytical program for samples obtained during the
time extended aeration effluent was applied to the system, are shown in Table
1, for the months of July and August 1978.
Overall removal of BODs, VSS, and TSS was about 50 percent each month.
COD reduction was about 40 percent. Ammonium nitrogen removal.of 67 percent
during August was superior to the 40 percent removal in July. Consideration
of the NH4-N, N03-N and N02-N valves between the two months indicates nitri-
fication and subsequent denitrification were more active in the system during
the warmer month of August. TKN samples were not collected during this period.
TP removal was not efficiently achieved by the MPI system operated as a '
tertiary process.
The extended aeration effluent applied to the system was of good quality.
The filter trench achieved the greater part of the overall pollutant removals,
with the elimination trench showing only marginal incremental removal.
MPI SYSTEM OPERATED AS A SECONDARY TREATMENT PROCESS
i The operation of the MPI system for treatment of raw, screened wastewater
was started on September 8, 1978. For evaluation, both filter trench results ,
were averaged together, as were both elimination trenches since preliminary
results showed efficiencies of the Phragmites and Scirpus in the elimination
trench were similar.
The major objective of this project was to evaluate the MPI system as a
low cost wastewater treatment alternative which would satisfy Federal discharge
requirements. These requirements are attainment of final effluent BODs and
SS concentrations not to exceed 30 mg/1 for 30 days average values, or 85
percent overall removal, whichever is more stringent.
= The system was evaluated for secondary treatment effectiveness for 11
months as shown in Table 2. For five of the months, the flow through the
system was 95 m3/d (25,000 god) or less. For six of the months, the flow
through the system was 133 m3/d (35,000 gpd). Secondary treatment requirements
for BODs and SS were achieved all five months at the lower flow. At the
higher flow rate, SS residuals and percent removals met secondary requirements
all six months; however, the BODs requirement was not achieved for five of
_ 16
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Table' Ter
-------
the six month. Three times the effluent violated both the concentration and
percent removal requirements (January, April, and July). The percent removal
requirement was violated twice (May and June).
There was little difference in overall COD removal for the two application
rates. For flows of 95 m^/d or less, the average was 78 percent and for the
higher flow, the average was 76 percent with only slight variation between
months.
The Nfy-N and Org-N concentration values in the effluent during the
periods of 95 irH/d application were representative of conventional secondary
treatment residuals. Variations in percent removals are due to fluctuations
in influent concentrations. The overall removal of total nitrogen varied
from 61 percent in September to 32 percent in March.
During application of 133 m^/d the organic nitrogen residuals were about
twice the values of the lower flow rate results. During February a negative
removal of Org-N was noted. The overall removal of total nitrogen was much
lower than during the 95 m^/d application. Values ranged from 18 percent in
January to 36 percent in June. - ...-.
Nitrite and nitrate nitrogen concentrations for all the sample periods
show that nitrification did not occur to any significant extent at either of
the two flow rates.
' The MPI system during both the 95 m^/d and the 133 m3/d application ;
rates was not effective for total phosphorus removal. During the higher ;
application rate, two months (January and June) showed negative removals.
; All sample periods showed a reduction in the pH value of about 1 unit
between the influent and elimination trench effluent, with the major fraction
of the decrease occurring in the filter trench.
| Total coliform tests were performed once every two weeks during the
months of December 1978 through March 1979 using the Most Probable Number
(MPN) method with final effluent dilution of 0.1, 0.01 and 0.001 ml. All :
test results showed effluent total coliforms to be greater than 240,000 per
100 ml. i
i ,
I
i Table 2 shows that the major increment of BOD5, SS, VSS, and COD removal
occurs at the filter trench and the elimination trench serves as a polishing
process. Both trenches in series are necessary for satisfactory treatment.
' The MPI system operated with raw screened wastewater at an application
rate of 95 m^/d did achieve secondary effluent quality. Using the trench
measurements given in Section 4, it can be calculated that the spatial require-
ments of the MPI system equate to 0.02 nH/m-d (0.5 gpd/ft2). Assuming a per
capita wastewater discharge of 378 1 (100 gal), the area required is 2 m^/capita
(21 ft^/capita). These two values are very similar to spatial requirements
of a septic tank system located in a satisfactory percolating soil.
18 '
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Table 2. Secondary Treatment Results for MPI System.
(Monthly Average Values)
Sample
Location
BOD5
TSS
VSS
COD NH4-N
September, 1978 mg/1
Influent
Wastewater
Filter Trench
Effluent
Elimination
Trench Effluent
Overall Removal,
Percent
203
68
26
87
205
42
19
91
176
32
14
92
501
246
102
80
October, 1978
Influent
Wastewater
Filter Trench
Effluent
Elimination
Trench Effluent
Overall Removal, ;
Percent
210
66
23
89
196
42
19
90
168
36
15
91
November
Influent
Wastewater
Filter Trench
Effluent
Elimination
Trench Effluent
Overall Removal,
Percent
212
86
27
87
250
46
24
90
220
40
20
91
448
142
86
81
, 1978
366
150
93
75
21
15
10
52
mg/1
24
16
13
46
mg/1
23
19
16
30 '
Org-N
flow
15
6
4
73
N02-N N03-N
15,000 gpd
0.0 0.1
0.2 0.9
0.1 0.4
~ 7"
TP
13.0
12.6
11.0
15
pH, Units
7.2
7.1
7.0
"
flow 25,000 gpd
12
8
4
67
flow
13
7
6
54
0.0 0.1
-
0.8 1.0
0.1 0.6
" ~
25,000 gpd
0.0 0.1
0.3 1.0
0.1 0.4
_
10.6
12.6
9.9
7
12.8
14.0
12.9
3
7.5
7.0
6.9
7.5
6.8
6.8
-
19
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Table 2. (Cont'd) Secondary Treatment Results for MPI System.
(Monthly Average Values)
Sample
Location
BOD5
TSS
VSS
December,
Influent .
Wastewater
Filter Trench
Effluent
Elimination
Trench Effluent
Overall Removal,
Percent
228
78
26
86
264
46
20
92
230
38
16
93
January,
Influent
Wastewater
Filter Trench
Effluent
Elimination
Trench Effluent
Overall Removal, :
Percent
214
85
38
82
146
47
21
86
144
40
18
88
February,
Influent
Wastewater
Filter Trench \
Effluent i
Elimination !
Trench Effluent ;
Overall Removal,
Percent
190
79
24
87
189
45
17
91
162
37
15
91
COO NH4-N
1978
360
183
80
78
1979
375
161
77
79
1979
381 ;
156 .
83
78
mg/1
24
21
18
25
mg/1
23
22
17
26
mg/1
26
18
15
42
Org-N
N02-N N03-N
flow 25,000
11
19
3
73
flow 35,
27
32
16
41
0
0
0
000
. 0
0
0
flow 35,000
11
9
14
(-27)
0
0
0
gpd
.0 0.1
.3 1.0
.1 0.4
.-
gpd
.0 0.2
.3 1.4
.0 0.7
gpd
.0 0.3
.7 1.6
.1 0.7
-
TP pH, Units
13.2
12.3
12.0
9
11.3
12.7
12.9
(-14)
11.7
11.7
11.7
0
7.5
6.4
6.7
7.9
6.8
6.8
7.7
6.6
6.6
-
20
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Table 2. (Cont'd) Secondary Treatment Results for MPI System.
(Monthly Average Values)
Sample
Location
BOD5
TSS
VSS
March,
Influent
Wastewater
Filter Trench
Effluent
Elimination
Trench Effluent
Overall Removal,
Percent
198
88
30
85
210
62
18
91
182
52
16
91
April,
Influent
Wastewater
Filter Trench
Effluent
Elimination
Trench Effluent
Overall Removal,
Percent
Influent
Wastewater
Filter Trench :
Effluent
Elimination
Trench Effluent
Overall Removal,
Percent
166
58
31
81
159
56
25
84
186
48
19
90
138
38
20
86
162
42
16
90
May,
118
34
15
87
COD
1979
380
174
82
78
1979
386
177
91
76
1979
444
165
98
78
NH4-N Org-N
mg/1 flow
29
25
22
24
mg/1 flow
29
26
25
14
mg/1 flow
24
21
21
13
25,
12
7
6
50
35,
9
8
7
22
N02-N N03-N
000 gpd
0.0 0.1
0.4 0.5
0.1 . 0.2
-
000 gpd
0.0 0.2
0.8 1.9
0.1 0.2
-
TP
13.4
12.1
12.1
10
17.7
15.7
15.8
11
pH, Units
7.8
6.7
6.7
-
7.7
6.6
6.8
-
35,000 gpd
28
6
12
57
0.2 0.6
0.8 1.4
0.3 1.4
13.8
13.0
11.6
16
7.7
6.8
6.8
21
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Table 2. (Cont'd) Secondary Treatment Results for MPI System.
(Monthly Average Values)
ample
.ocation BODs TSS VSS COD NH4-N Org-N N02-N
June, 1979 mg/1 flow 35,000 gpd
nf luent
lastewater 155 188 162 419 22 10 0.0
'liter Trench
f fluent 64 40 36 164 18 14 0.4
limination
Vench Effluent 27 16 14 98 19 6 0.1
Iverall Removal,
ercent 83 91 91 77 14 40
July, 1979 mg/1 flow 35,000 gpd
nfluent
lastewater 143 240 204 422 - - .0.1
liter Trench
ffluent 68 40 32 118 - - 0.6
.limination
"rench Effluent 31 20 18 112 - - 0.2
Jverall Removal, :
ercent ' 78 92 91 73
!
i :
N03-N TP pH, Units
0.1 12.1 7.4
0.3 12.1 6.6
0.2 13.5 6.8
. .- (-12)
0.2 11.6 7.4
0.4 11.9 6.5
0.1 11.4 6.6
2
22
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Section 5 detailed the several operating problems that occurred during
this demonstration study. These occurrences are to be expected with new
technology development. This initial assessment of the efficiency and spatial
considerations for the MPI system for secondary treatment indicates it is
worthy of further development. Many of the same operational problems were
encountered at the Long Island, New York, installation. Remedial measures
applied there included provision for increased area for the filter trenches,
thereby allowing longer idle times for drying. Also the Long island study
showed that frequent harvesting of the plants used in the system promotes
extra growth of the root systems and this contributes to clogging. Their
recommendation is to harvest plants not more than once a year. If plant
growth becomes excessive during the year, individual plants are culled by
pulling to thin the growth.
23
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing!
1. REPORT NO.
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
'^istewater Treatment by Rooted Aquatic Plants in
Wand and Gravel Trenches
5. REPORT DATE
May 1981 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Pamela R. Pope
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION-NAME AND ADDRESS
Moulton Niguel Water District
Laguna Niguel, California 92677
10. PROGRAM ELEMENT NO.
AZB1B - D.U. B-113
11. CONTRACT/GRANT NO.
Grant No. R-805279
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research LaboratoryGin. ,OH
Office of Research and Development
U.S. Environmental Protection Agency
incinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final 8/77-8/79
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Project Officer: Dr. R. Lewis (513) 684-7641
16. ABSTRACT
The Moulton Niguel Water District of Laguna, California constructed and operated
an earthen trench system employing rooted aquatic plants for the treatment of
wastewater. Two trenches in series were planted with the reed Phragmites and the
julrush Scirpus, respectively.
A two-month study using conventional secondary effluent as the trench influent
owed the system was not effective for removal of nitrogen and phosphorus components.
An eleven-month study demonstrated that raw screened wastewater applied to
the trench system at a rate not exceeding 95 nr/d (25,000 gpd) could be treated to
secondary effluent quality. Spatial requirements were about the same as for a
septic tank system.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Jastewater
Biological Removal*
Harvesting*
Flora
Rooted Aquatic*
Waste Treatment*
Earthen Trenches
Reeds
Bulrush
13B
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)
Release to Public
21. NO. OF PAGES
30
20. SECURITY CLASS (This page)
Release to Public
22. PRICE
**£PA Form 2220-1 (9-73)
24
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