Cleaning Up Carabuela:
What to do with Number Two
Team 7
Ian Compton
Adam DeYoung
Josh Scheenstra
Nathan Williams
Engineering 339/340 Senior Design
Project
Calvin College
December 12, 2012
©2012 Team 7, Calvin College
i
Executive Summary
Initial Project Summary
The focus of this project is to provide sanitary wastewater management practices for a small village in
Ecuador. The village, Carabuela, is made up of about 500 homes and is located in the Andes Mountains.
Carabuela currently has a defective treatment system that is releasing untreated or poorly treated
waste into a nearby river. The waste collection system is in an unknown condition and will be evaluated
and redesigned as needed.
Partnering Organization
The project was proposed through Calvin College by the global healthcare/ministries organization called
HCJB (Heralding Christ Jesus’ Blessing). HCJB operates largely out of Ecuador and does substantial work
with community development projects. They have partnered with Calvin College for a while and are
working with the team to help bring more sanitary conditions to the village of Carabuela.
Collection system
The village has an existing collection system that services approximately half of the homes. The
condition and location of the system is currently unknown and will need to be evaluated. Depending on
the state of the collection system, a completely new system will be designed or only broken-down
portions.
Treatment Facility
The treatment facility is the largest part of the design. The two main requirements of the facility are
that it must be a passive process and it must have low costs. The current preliminary design is a set of
bar screens, followed by a set of anaerobic ponds in parallel, and an infiltration bed to discharge the
treated effluent to the groundwater. This process will operate passively and require minimal
maintenance and installment costs.
Irrigation Distribution
A feasibility study to use the treated effluent for irrigation will be done after gathering more pertinent
information regarding Carabuela.
Travel Requirements
Team Carabuela will be traveling to Ecuador in January for 10 days to gather information about
Carabuela. This trip will entail evaluating conditions of the current collection system, surveying
topography, testing soil types, locating available land, working directly with HCJB, and communicating
with the local people to establish a relationship and understand the cultural parameters affecting any
possible designs.
Costs
The costs for the trip include airfare, room and board, food, equipment rental, and ground
transportation. The estimated cost per person for this trip then is $1700; $1000 for airfare and a $700
contingency fund for daily expenses. This is based on a cost estimate of about $55/day given by HCJB.
ii
Next Steps
The next steps of the project are to refine the initial treatment design and begin validating assumptions
made in the collection system model. This will mainly come through the information gathered from the
trip to Carabuela.
iii
Table of Contents
Executive Summary....................................................................................................................................... ii
Table of Contents ......................................................................................................................................... iv
Table of Figures ............................................................................................................................................ vi
Table of Tables ............................................................................................................................................ vii
1. Introduction .............................................................................................................................................. 1
1.1 The Team: Cleaning Up Carabuela .................................................................................................... 1
1.2 Project Background ............................................................................................................................. 2
2. Problem Statement .................................................................................................................................. 2
3. Partnering Organization ............................................................................................................................ 2
3.1 HCJB .................................................................................................................................................... 2
3.2 The Village and Context ...................................................................................................................... 2
4. Existing Conditions .................................................................................................................................... 5
4.1 The Treatment Plant ........................................................................................................................... 5
4.2 The Collection System ......................................................................................................................... 6
4.3 Village Demographics.......................................................................................................................... 6
5. Design Constraints .................................................................................................................................... 7
5.1 Flows and Loads .................................................................................................................................. 7
5.2 Effluent Standards............................................................................................................................... 8
5.3 Location ............................................................................................................................................... 8
5.4 Costs .................................................................................................................................................... 8
6. Design Norms ............................................................................................................................................ 9
6.1 Cultural Appropriateness .................................................................................................................... 9
6.2 Caring .................................................................................................................................................. 9
6.3 Stewardship ........................................................................................................................................ 9
6.4 Transparency....................................................................................................................................... 9
7. Design...................................................................................................................................................... 10
7.1
Collection System ........................................................................................................................ 10
7.1.1
Preliminary Design 1.1 ........................................................................................................ 10
iv
7.1.2
Preliminary Design 1.2 ........................................................................................................ 12
7.1.3 Materials Standards ................................................................................................................... 19
7.2
Treatment ................................................................................................................................... 19
7.2.1 Treatment Options ................................................................................................................... 19
7.2.2 Treatment Decision Matrix ........................................................................................................ 25
7.2.3 Selected Treatment Design Alternatives ................................................................................... 27
7.3 Effluent .............................................................................................................................................. 30
7.3.1 Effluent Targets .......................................................................................................................... 30
7.3.2 Irrigation Feasibility ................................................................................................................... 31
8. Construction and Maintenance .............................................................................................................. 31
9. Costs ........................................................................................................................................................ 31
9.1
Team Costs .................................................................................................................................. 31
9.2
Project Costs ............................................................................................................................... 32
9.2.1
Treatment System Cost ....................................................................................................... 32
9.2.2
Collection System Costs ...................................................................................................... 32
9.2.3
Design Costs ........................................................................................................................ 33
9.2.4
Cost Summary ..................................................................................................................... 33
10. Work Plan .............................................................................................................................................. 34
10.1 Interim............................................................................................................................................. 34
10.2 Trip .................................................................................................................................................. 34
11. Works Cited ........................................................................................................................................... 35
v
Table of Figures
Figure 1 : Map of Ecuador with a star on Carabuela .................................................................................... 3
Figure 2 : Overview Map of Carabuela ......................................................................................................... 4
Figure 3: Average Yearly Temperatures in Quito, Ecuador........................................................................... 5
Figure 4: Average Yearly Rainfall in Quito, Ecuador ..................................................................................... 5
Figure 5: Current Treatment Facility ............................................................................................................ 6
Figure 6: Preliminary Sewer Design 1.1 AutoCAD Approximate Pipe Layout for Entire System ................ 11
Figure 7 : Preliminary Sewer Design 1.2 SWMM Map with Manhole Invert Elevations and Pipe Slope .... 13
Figure 8 : Preliminary Sewer Design 1.2 SWMM Maximum Velocities ...................................................... 15
Figure 9 : Preliminary Sewer Design 1.2 SWMM Surface and Pipe Profile View of the Longest Reach
(Southern Most Point to Discharge) ........................................................................................................... 16
Figure 10 : Preliminary Sewer Design 1.2 SWMM Model Conduit Peak Flows .......................................... 17
Figure 11 : Preliminary Sewer Design 1.2 SWMM Model Conduit Capacity (Ratio of Depth to Full Depth)
.................................................................................................................................................................... 18
Figure 12: Manually Cleaned Bar Screen Structure Plan and Profile Views ............................................... 20
Figure 13: Typical Septic Tank Design ......................................................................................................... 22
Figure 14: Typical Bio-Filtration Setup ........................................................................................................ 23
Figure 15: Constructed Wetlands ............................................................................................................... 24
Figure 16: Infiltration Bed ........................................................................................................................... 25
Figure 17 : Waste Stabilization Pond Layout .............................................................................................. 27
vi
Table of Tables
Table 1 : Major Constituents of Typical Domestic Wastewater ................................................................... 7
Table 2 : Current and Projected Sanitary Flows ............................................................................................ 8
Table 3 : Preliminary Design 1.1 Pipe Lengths and Diameters ................................................................... 10
Table 4 : Collection System Flow Calculations ............................................................................................ 12
Table 5 : Sewer Size and Minimum Slope to Maintain a 2ft/s Flow Velocity ............................................. 14
Table 6 : Piping Materials............................................................................................................................ 19
Table 7: Horizontal Flow Grit Chamber Design Criteria .............................................................................. 20
Table 8 : Decision Matrix............................................................................................................................. 26
Table 9 : Waste Stabilization Pond Design Parameters .............................................................................. 28
Table 10 : Pond Sizing ................................................................................................................................. 28
Table 11: Recommended Rates of Wastewater Application for Trench and Bed Bottom Areasa .............. 29
Table 12 : Fresh Water Discharge Effluent Standards in Ecuador .............................................................. 30
Table 13 : Michigan Department of Environmental quality Standards for discharge into Ground Water . 30
Table 14 : Breakdown of Trip Costs ............................................................................................................ 32
Table 15 : Initial Estimated Wastewater Treatment Facility Costs ............................................................. 32
Table 16 : Initial Estimated Wastewater Collection System Costs.............................................................. 33
Table 17 : Initial estimated Design Costs .................................................................................................... 33
Table 18 : Total Cost Estimate .................................................................................................................... 34
vii
1. Introduction
1.1 The Team: Cleaning Up Carabuela
Team Carabuela is composed of civil/environmental engineering students; each member brings a variety
of experiences, interests, skills, and backgrounds to the design project.
Nathan Williams
Nathan was born and raised in Howell, Michigan. He is a senior at Calvin College expecting to graduate
in May 2013 with a Bachelor of Science in Engineering degree. He is interested particularly in the
environmental field but would like to work with water quality or quantity. He interned in the summer of
2012 at the City of Kentwood, working with the municipal engineering department.
Adam DeYoung
Adam was born and raised in Hudsonville, Michigan. He has a desire to use his skills acquired in Calvin
College’s Engineering program to provide clean water and quality water wherever God will tell him to
go. He has previously been involved with Varsity Athletics in Basketball and Track and Field at Calvin
College. He has been involved in youth ministry for three years through a summer camp in Montana and
Young Life in a local high school. This past summer, 2012, Adam worked as an intern at Vriesman &
Korhorn Civil Engineers completing a Global Positioning System (GPS) survey, a witnessing project, and
supervised new utility construction. His gained experience using the GPS will be put to use when the
team travels to Ecuador. He desires to serve others with his engineering, by providing for their needs,
and sharing the Gospel.
Ian Compton
Ian is a senior civil engineering student from Duanesburg, New York. He had the great opportunity to
work with HCJB Global, the partnering mission organization of this project, in the summer of 2012. He
worked specifically with the community development team in Quito on various clean water projects
throughout Ecuador. He is privileged to have the opportunity to work with HCJB again. He is mostly
interested in the hydraulic and environmental aspects of the project.
Joshua Scheenstra
Joshua Scheenstra is a senior at Calvin College who was born and raised in Kenya. His family has served
as missionaries to an unreached people group for the past 26 years. He has participated in numerous
community development projects in developing countries and many of them had to do with providing
clean water. He has interned for Tulare Irrigation District the past three summers in California’s central
valley. He is mostly interested in the hydraulics and structural aspects of civil engineering.
1
1.2 Project Background
The village of Carabuela Ecuador is a small, underprivileged community of approximately 500 homes
tucked in the Andes Mountains approximately 100 kilometers north of the capital city, Quito. The
mission organization HCJB Global (Heralding Christ Jesus Blessings) is an international organization
focused on community development in developing countries and has established large presence in
Ecuador, and specifically in Carabuela. Recently, HCJB implemented a water distribution system in the
village but also realized the village’s desperate need for a wastewater collection system and treatment
facility. Currently, there only exists a partial collection system and all of the effluent is discharged into
the local stream untreated. To solve this problem, Team Carabuela, is partnering with HCJB to design the
wastewater collection system and treatment facilities for them to implement in the near future.
2. Problem Statement
The goal of this project is to design a new wastewater collection and treatment system for Carabuela,
Ecuador. In addition to improving sanitation, the main constraints of the project are cost, ease of design
and a passive treatment facility that requires no power consumption. Keeping costs low is of high
importance for the village and the organization. The design must also be able to operate passively in
order to keep maintenance and labor requirements low.
3. Partnering Organization
3.1 HCJB
Team Carabuela is partnering with the international mission organization HCJB Global. HCJB works with
healthcare provision, community development, and multimedia ministry. They operate on almost every
continent with a strong base in Ecuador and the entire Latin America. HCJB has been very active in
Ecuador with both their radio and healthcare ministries. Especially from an engineering standpoint,
HCJB has worked on many projects, from clean drinking water to treating wastewater. Students from
Calvin College have often partnered with HCJB in the past to provide clean water needs to various
villages or organizations in Ecuador and around the world.
3.2 The Village and Context
The village we are working with is called Carabuela. Carabuela is a village of about 500 homes a few
hours driving distance north of the capital city, Quito. Ecuador is located in South America and straddles
the equator. Ecuador is divided into three main geographic regions: La Costa (the Coast), La Sierra (the
Highlands), and La Amazonia (the East). La Costa is made up of the coastal western side of Ecuador, La
Sierra is comprised of the Andes Mountain range through central Ecuador and La Amazonia is made up
mostly of rain forest.
2
N
a
s
Map not to scale
Figure 1 : Map of Ecuador with a star on Carabuela1
Carabuela is located in La Sierra in the Andes Mountains and has a relatively mild and dry climate
because of its altitude. A simplified overview of Carabuela can be seen in Figure 2. In this figure, the
contour of the village is shown along with roads, and the stream running through the village. Because
Carabuela is in the same climate zone as Quito, they have similar temperature and precipitation ranges.
To see average yearly temperature and rainfall, see Figure 3 and Figure 4, respectively.
1
http://mappery.com/map-of/Ecuador-Map-2
3
Figure 2 : Overview Map of Carabuela2
Ecuador gained its independence from Spain in 1820 and has been plagued with political instability
throughout most of the 19th and 20th centuries. It is currently a republic and has been holding
democratic elections since the late 1970s. Economically, Ecuador is growing and has stabilized
considerably over the past few decades. Almost half of its exports are crude oil related and the rest is
made up mostly of agricultural products, such as bananas and coca3. Ecuador has also improved in the
health care and infrastructure development areas over the past few decades; however, rural areas, such
as the area surrounding Carabuela, are still in need of much improvement.
2
3
HCJB
https://www.cia.gov/library/publications/the-world-factbook/geos/ec.html
4
Figure 3: Average Yearly Temperatures in Quito, Ecuador4
Figure 4: Average Yearly Rainfall in Quito, Ecuador 5
4. Existing Conditions
4.1 The Treatment Plant
The initial treatment plant for the approximately 200 homes that were connected to the collection
system was a septic tank and leach field (Figure 5). The leach field was undersized and became
saturated6. Untreated wastewater is now discharged into the river by the school (Figure 5). This
treatment system failed and an adequately sized treatment system is needed.
The septic tank could be used with a rebuilt treatment field to treat a portion of the wastewater but
most of the wastewater needs to be diverted elsewhere. The location of the current drainage field is
4
From World Weather and Climate Information
From World Weather and Climate Information
6
Obtained from Bruce Rydbeck, October 2012, HCJB
5
5
concerning because of its close proximity to the river and presumably the groundwater table as seen in
Figure 5. The size and status of the septic tank and drain field can be verified upon visiting the site.
Figure 5: Current Treatment Facility7
4.2 The Collection System
The initial information provided by HCJB on the collection system is very limited. The given information
stated that an existing collection system is attached to approximately 200 of the 500 homes and was
built around 2005 or 2006, but the condition and definite location is unknown. HCJB further stated that
the 200 homes are roughly located on the east side of the village between the central hill and the PanAmerican Highway. The only specific pipe information given was that one known 20cm diameter
concrete pipe runs perpendicular to the highway. The water consumption for the village was also given
from which a total treated water flow of 265600 L/day was calculated. The infiltration flow rate given
was 1 to 2 liters/second for the entire system. Not further information was provided.
4.3 Village Demographics
The 508 homes in the village were modeled with a growth rate of 3% per year. The growth rate was
provided by HCJB as an initial constraint.
7
Provided by HCJB
6
5. Design Constraints
5.1 Flows and Loads
In order to correctly design a suitable treatment facility for Carabuela, the concentration and amount of
wastewater constituents was crucial to understand. Due to the lack of specific information regarding
waste loads in Ecuador or developing countries in general, an estimate was made according to Table
1. We assumed a strong waste concentration. This confirms other research relating to waste in
developing countries as well as previous design teams that have worked in Ecuador with HCJB.
Table 1 : Major Constituents of Typical Domestic Wastewater8
Constituent
Total solids
Dissolved solids (TDS)19
Suspended solids
Nitrogen (as N)
Phosphorus (as P)
Chloride1
Alkalinity (as CaCO3)
Grease
BOD510
(mg/L)
Strong
1200
850
350
85
20
100
200
150
300
(mg/L)
Medium
700
500
200
40
10
50
100
100
200
(mg/L)
Weak
350
250
100
20
6
30
50
50
100
The water usage is 332 m3/day for the 508 homes, but only about 200 homes are connected to the
sewer line.11 The water usage for just the homes that are connected would then be around 133 m 3/day.
Sanitary flow typically ranges from 50% to 100% of the water usage.12 Sanitary flow ranges greatly from
city to city and there is no data for the flow in Carabuela so a safe estimate of 80% of the water usage
was used for comparing treatment options. Sanitary flows into the collection system vary throughout
the day, so it is important to be able to predict and design for peak flows. The peaking factor is related
to population and tends to become less pronounced at higher populations. The peaking factor can be
8
UN Department of Technical Cooperation for Development (1985)
The amounts of TDS and chloride should be increased by the concentrations of these constituents in the carriage
water.
10
BOD5 is the biochemical oxygen demand at 20°C over 5 days and is a measure of the biodegradable organic
matter in the wastewater.
9
11
12
Obtained from Bruce Rydbeck of HCJB in October 2012
Reynolds, Tom D., and Paul A. Richards. Unit Operations and Processes in Environmental Engineering. 2nd ed.
Boston: PWS Publishing Company, 1996: 96.
7
calculated using
𝑸𝑷
𝑸𝑨
=
𝟓
Equation 1, where P is the population in thousands and Qp/QA is
𝑷𝟎.𝟐
the peak hourly flow divided by the average hourly flow.
𝑸𝑷
𝑸𝑨
=
𝟓
Equation 1 : Sanitary Flow Peaking Factor13
𝑷𝟎.𝟐
Table 2 : Current and Projected Sanitary Flows
Year
Average Sanitary
Flow (L/day)
2012
265.6
2032 (Projected)
479.7
Peaking Factor
4.15
3.69
Peak Hourly
Sanitary Flow
(L/day)
1102
1770
The sanitary flows in Table 2 exclude storm water since there is a minimal time period where storm
water will dictate the amount of wastewater that can be treated. The projected flows are based on a
project design life of 20 years with a population growth rate of 3%.14
5.2 Effluent Standards
The effluent quality standards given by HCJB were quite vague. The standards for the design were to be
comparable to similar projects. In order to find a suitable target, case studies and national standards
were researched. For specific values, see Table 12 and Error! Reference source not found. in section 7.
5.3 Location
The village location itself is also a constraint that we have considered in relation to the proposed design
solution. Carabuela is in a mountainous and somewhat arid region. This limits the amount of land
available for the implementation of the design solution as well as the amount of water available to the
village for irrigation.
5.4 Costs
It is imperative to the design system’s costs as low as possible. This is a major constraint for our team
and HCJB as well as the village itself. We were given a maximum target cost of $50,000 (US) for the
13
14
Reynolds, Tom D., and Paul A. Richards. Unit Operations and Processes in Environmental Engineering: 98.
Obtained from Bruce Rdbeck of HCJB in October 2012
8
treatment facility and collection system (excluding labor costs). This dollar figure came from our HCJB
contact in Ecuador.
6. Design Norms
6.1 Cultural Appropriateness
The cultural appropriateness is of utmost concern in our proposed design. It was very important to
prioritize the differing culture and societal standards of Carabuela, Ecuador as opposed to Grand Rapids,
Michigan. Before travelling to the village, our designs could only be considered as tentative until they
could be evaluated in their proper context. As Christians, it was important to us not to try and impose a
type of cultural norm on the treatment design or the village.
6.2 Caring
At its most basic level, the purpose of the design project and proposed solution is to be able to help
people that need it. The village of Carabuela is currently living in unsanitary and unsustainable
conditions. The driving force of this project is to be able to provide a basic need to people without the
ability to provide it for themselves. It was important for our team to keep this in mind in order to stay
grounded and focus on helping people in need.
6.3 Stewardship
The design norm of stewardship is a crucial element to our design constraints and proposed
solution. An idea implicit within our design criteria is that the treated wastewater effluent must be safe
for the environment and potential contact with humans downstream. This idea is fundamental to our
beliefs as Christians that the earth has been charged to humans to be taken care of. Stewardship is also
important to the types of materials used in the design as well. Ideally, these materials will maximize the
effectiveness of the design while still not polluting the earth or having a negative effect for many years.
6.4 Transparency
It was important that our design be transparent, especially during the designing process
itself. Treatment designs must be clear and easy to comprehend under ordinary circumstances;
however, it is so much more imperative that this is the case when working across vast geographic and
linguistic barriers. Our communication with our engineering contact in Ecuador was infrequent at best
due to availability constraints. This made it very important that our communication with him was very
concise and clear. Many of the resources that we came in contact with were written in Spanish. This
was also something our group had to keep in mind when translating technical information into English.
9
7. Design
7.1 Collection System
7.1.1 Preliminary Design 1.1
Because the initial information was so limited, the preliminary design for the collection system was
based on numerous assumptions. The entire system to collect from all 508 homes was initially modeled
with sewage pipes running down each street and laid out in AutoCAD. The design can be seen below in
Figure 6. The main assumption made was that no system already exists. The assumption was made to
get an assessment of what the total length of pipe will be needed if the entire system has to be
replaced. The initial design yielded a total pipe length of 11500m. The estimated pipe diameters and
lengths can be seen below in Table 3. The pipe diameters and locations were chosen to have the
smaller pipes on the outskirts and the larger pipes for the main sewers where the largest flows are
found. The primary purpose of the preliminary design 1.1 was to find out what total pipe lengths would
be to estimate the initial cost. Because the location of the existing system was too vague, the initial cost
plan used this design layout of the entire system and did not take into account the possible 200 homes
already connected. After further information is collected, a much more accurate assessment will be
made.
Table 3 : Preliminary Design 1.1 Pipe Lengths and Diameters
6” Concrete Pipe
8” Concrete Pipe
10” Concrete Pipe
Total
Length (ft)
3326.4
3125.7
5051.3
11503.4
10
Figure 6: Preliminary Sewer Design 1.1 AutoCAD Approximate Pipe Layout for Entire System
11
7.1.2 Preliminary Design 1.2
After completing the general layout in Preliminary Design 1.1, a much more accurate and specific model
was created in Preliminary Design 1.2. This design’s purpose was to model the area on the east side of
the village where the probable location of the existing collection system resides. The computer software
used for this design was SWMM (Storm Water Management Model), which is a universally recognized
storm water and wastewater simulation program. Although the actual location of the system was
unknown, it was assumed that the pipes ran along the major streets and collected from all the homes in
the most populated part of the area between the hill and the Pan-American Highway. Figure 7 shows
the SWMM system layout. Table 4 shows the flow calculations for the model. (NOTE: Because SWMM
only used US Customary units all units were converted to that, and after the final model is finished all
the results will be converted back to SI units)
The flow calculations in Table 4 were based on the water consumption and infiltration flows given by
HCJB. Assuming that the average household hosts 5 members the total population connected to the
system was calculated. Additionally, the peak factor as a function of population was calculated using
Curve G given in the ASCE Manuals and Reports on Engineering Practice- No. 60.
The peak factor multiplied by the average discharge yielded the peak discharge for the entire system
and when divided by the number of homes it gave the peak discharge per home. Finally, the peak
discharge per home was multiplied by the number of homes contributing to each node in the SWMM
system and modeled as inflow in that location.
Table 4 : Collection System Flow Calculations
Discharge
Collection System Flow Calculations
US Customary Units
SI Units
35
gal/cap/day
0.133
m3/cap/day
Infiltration
22824.49
gal/day
90
m3/day
Infiltration
0.035315
cfs
0.001
m3/s
# of Homes
Population
Total Population
Peak Factor
Average Discharge
229
homes
5
persons/home
1145
total persons
3.761
Curve G
62899.49
gpd
229
5
1145
3.761
241.7125
homes
persons/home
total persons
Curve G
m3/day
Peak Discharge
Peak Discharge Per Home
0.366
0.001598
0.0105
4.59504E05
cms
cms
cfs
cfs
12
Figure 7 : Preliminary Sewer Design 1.2 SWMM Map with Manhole Invert Elevations and Pipe Slope
13
Several key design parameters were assumed for Preliminary Design 1.2. First, to ensure that the pipes
conveyed all of the waste adequately, a minimum velocity of 2ft/s was assumed (Practice No. 60). To
attain the minimum velocity, a minimum slope was required for each pipe. The minimum slopes for
various diameters required to ensure a 2ft/s velocity are shown below in Table 5 (Practice No. 60) and
the slopes of each pipe are seen above in Figure 7. Figure 7 also shows the invert elevations based on
the contour map of the village provided by HCJB. To prevent velocities from getting too high on the
villages steep slopes, a maximum velocity of 10ft/s was also assumed (Practice 60). Figure 8 shows the
designs initial velocities in the pipes. This initial design shows some possible problems in the system that
need to be addressed once final pipe locations and slopes are confirmed. Primarily, the main possible
problem is the areas where velocities may not reach the minimum 2ft/s or may exceed 10ft/s.
Table 5 : Sewer Size and Minimum Slope to Maintain a 2ft/s Flow Velocity
Sewer Size
(in)
8
10
12
15
18
21
24
30
36
Minimum
Slope
(ft/100ft)
0.40
0.28
0.22
0.15
0.12
0.10
0.08
0.058
0.046
14
Figure 8 : Preliminary Sewer Design 1.2 SWMM Maximum Velocities
Second, the minimum cover necessary was assumed to be 3 ft. Because the area is never inflicted with
freezing temperatures, no consideration was needed for the possibility of the water freezing in the
pipes. Additionally, because none of the houses have basements where bathrooms or other water
utilities exist, no consideration was taken to place the pipes below house basement levels. The minimum
cover of 3 feet was chosen to ensure that the pipes are always protected from vehicle loads in the roads
and possible erosion that would expose the pipes. The pipe and soil profile view can be seen below in
Figure 9. Further study will be done of the optimal depth once more information can be gathered from
the trip to Carabuela in January.
15
Figure 9 : Preliminary Sewer Design 1.2 SWMM Surface and Pipe Profile View of the Longest Reach (Southern Most Point to Discharge)
16
Finally, a pipe diameter of 8 inches was chosen initially based on the smallest available pipe sizes.
Sewers in the United States rarely use pipes smaller than 8 inches but after further information is gained
on the trip to Ecuador, 6 inch pipes may be substituted later. The main criteria for the conduit flows
were that the pipes should never surcharge and should be able to adequately handle all the flows.
Figure 10 below shows the peak flows in each pipe. Figure 11 shows the each pipe’s capacity, or the
ratio of maximum depth to full depth. The pipe capacity confirms that none of the pipes ever become
surcharged because none of the values exceed 1.
Figure 10 : Preliminary Sewer Design 1.2 SWMM Model Conduit Peak Flows
17
Figure 11 : Preliminary Sewer Design 1.2 SWMM Model Conduit Capacity (Ratio of Depth to Full Depth)
18
7.1.3 Materials Standards
The piping materials that are commonly used in the U.S. for sewer design are shown below in Table 6.
These materials are also commonly used around the world and will most likely be found in Ecuador.
Table 6 : Piping Materials15
Pipe Material
Asbestos cement
Ductile iron
Reinforced concrete
Pre-stressed concrete
Polyvinyl chloride
Vitrified clay
Description
Rigid yet light-weight; moderate resistance to
corrosion
Very leak-proof; susceptible to acid corrosion
High availability; vulnerable to corrosion if waste
stream contains hydrogen sulfide or in high-sulfate
environment
Well-suited to long transmission mains; vulnerable to
corrosion
Lightweight and strong plastic material; resistant to
corrosion
Commonly used in past; resistant to corrosion; quite
brittle and susceptible to leakage
7.2 Treatment
One of our main constraints is to design a passive process. This limited our treatment options
considerably and automatically ruled out most of the processes used in the United States. Passive
treatment can be very cost effective and easier to maintain than more mechanical processes if designed
correctly. The passive treatment options we then considered can be seen below.
7.2.1 Treatment Options
7.2.1.1
Bar Screens
Bar Screens are used for preliminary treatment. The effluent from the collection system flows through a
metal screen that filters out large objects such as rags and floatables. This prevents clogging
downstream and protects equipment. The closer the bars are together on the screen, the more
contaminates are removed, however, this increases the need to rake and remove the contaminates
from the screen. In most U.S wastewater treatment plants, bar screens are mechanically raked but our
system would require manual raking in order to be passive treatment. Bar screens are very simple and
have a very small footprint, which makes it an essential part of the design. A secondary flow path is
needed to maintain flow while cleaning the primary flow path as shown in Figure 12.
15
Source: From Metcalf & Eddy, Inc. [6-8]
Figure 12: Manually Cleaned Bar Screen Structure Plan and Profile Views16
7.2.1.2
Grit Removal
Grit is defined as sand, gravel, food waste and other heavy solid materials. Removal of grit prevents
excess accumulation in pipelines or waste lagoons. Grit removal also decreases the amount of manual
labor needed to maintain subsequent waste lagoons. A passive grit removal technique that could be
employed is a horizontal flow grit chamber. This uses weirs and control devices to maintain a constant
flow of 0.3 m/s. The length of the chamber depends on the items shown in Table 7.
Table 7: Horizontal Flow Grit Chamber Design Criteria17
Item
Detention Time
Horizontal velocity
Settling velocity
50-mesh
100-mesh
Head loss (% of channel depth)
Inlet and outlet length allowance
16
17
Range Metric
(English)
45-90 s
0.24-.0.4 m/s
(0.8-1.3 ft/s)
Typical Metric
(English)
60 s
0.3 m/s
(1.0 ft/s)
2.8-3.1 m/min
(9.2-10.2 ft/min)
0.6-0.9 m/min
(2.0-3.0 ft/min)
30-40%
25-50%
2.9 m/min
(9.6 ft/min)
0.8 m/min
(2.5 ft/min)
36%
30%
Drawn by Ian Compton
Wastewater Technology Fact Sheet: Screening and Grit Removal. Washington, D.C.: U.S. Environmental
Protection Agency, Office of Water, 2003. Internet resource. 8
20
7.2.1.3
Waste Stabilization Ponds
Waste Stabilization Ponds (or WSP’s) use the sun and natural processes to treat raw sewage. The three
types of ponds considered for the design are anaerobic, facultative, and maturation. All are open bodies
of water that require little to no human supervision or interaction18. The ponds are used to settle out
suspended solids in wastewater as well as lower the total BOD. As the waste stream enters the pond,
the liquid velocity goes to zero which causes most of the suspended solids to settle out. Bacteria in the
pond then break down organic constituents in the waste. These ponds are often good treatment
options when considering passive treatment methods, if the necessary amount of land is
available. Ponds like these rely on a specified residence time that is required to reduce targeted waste
constituents by a certain amount. The residence time is a function of how quickly the bacteria can break
down waste and can vary with temperature. Ponds can be connected in series or in parallel in order to
give a level of redundancy or increased residence time. Waste stabilization ponds need to be routinely
cleaned in order to remove accumulated solids. WSPs, when sized correctly, can achieve 80% BOD
removal19. WSPs also have a fairly large footprint, which could become a problem if areas of level
ground are limited in Carabuela.
7.2.1.4
Septic tanks
Septic tanks are similar to anaerobic ponds in that they separate the solids from the liquids and
biologically degrade the waste20. A septic tank, however, is a watertight tank underground as shown in
Figure 13. The tank allows waste to be broken down by bacteria and also relies on a certain residence
time in order to optimize effectiveness. A septic tank is currently being used in Carabuela, but it is
considerably undersized for the amount of wastewater being produced (Figure 13). Septic tanks also
require routine removal of accumulated solids.
18
Kayombo, Sixtus. Development of a Holistic Ecological Model for Design of Facultative Waste Stabilization Ponds
in Tropical Climates. Copenhagen: Royal Danish School of Pharmacy, Department of Analytical and
Pharmaceutical Chemistry, Section of Environmental Chemistry, 2001. 6
19
Mara, D. Domestic Wastewater Treatment in Developing Countries. London: Earthscan Publications, 2004. 109
Internet resource
20
From Onsite Wastewater Treatment and Disposal Systems, EPA Design Manual
21
Figure 13: Typical Septic Tank Design21
7.2.1.5
Bio-filtration
Bio-filtration relies on a gravity feed of the waste stream through a bed of filter media as seen in the
middle of Figure 14. This is often sand of various grain sizes, but can be different forms of activated
carbon or even man-made material. Filters of this type are used as secondary treatment after much of
the solids is removed. The filters then often contain a layer of biofilm which helps further reduce BOD
content in waste streams. However, some biofilm is flushed out with the water and trickling filters.
Scum layers form periodically on the top of bio-filters and need to be routinely backwashed and/or
scraped off in order to maintain optimal working conditions. The scum may contain disease-causing
pathogens, but can be safely scraped off and buried.22
21
22
Drawn by Ian Compton
From Onsite Wastewater Treatment and Disposal Systems, EPA Design Manual
22
Figure 14: Typical Bio-Filtration Setup23
7.2.1.6
Constructed Wetlands
Since Carabuela has a natural river that flows through the town, this natural feature could be utilized for
wastewater treatment in the form of a constructed wetland. This treatment option is useful for
irrigation purposes because of the removal of pathogens.24 Currently, constructed wetlands have
imprecise design and operation criteria. It is hard to quantify how well the wastewater would be
treated. Topographic relief may also prevent this approach. A portion of the river could be lined with
plants as shown below in Figure 15 .
23
24
Drawn by Ian Compton
Kayombo, S., and T.S.A Mbwette. Waste Stabilization Ponds and Constructed Wetlands Design Manual
UNEP-IETC. 44
23
Figure 15: Constructed Wetlands25
7.2.1.7
Ground Infiltration26
Ground infiltration is a process in which a treated discharge stream is allowed to percolate through the
ground. This effectively uses the soil as a type of filter media. This process relies heavily on the type of
soils in the area and the elevation of the water table. At least three feet of dry soil is required to
maximize pollutant removal and prevent ground water contamination. Infiltration usually takes place as
ground application or as an underground set of perforated pipes. With ground application, an effluent
stream is discharged onto a gravel bed that overlays the intended infiltration area as seen in Figure 16.
With underground infiltration, a pipe or pipes are laid along the bottom of an excavated trench or bed
and then packed with gravel before backfilling. These methods also require routine maintenance in
order to scrape off a biofilm “mat” that forms on top of the filter media and can clog the infiltration
capacity. This can be lessened with the use of dosing multiple infiltration beds one at a time. This
allows a period of drying for a field and can help prevent a mat from building up.
25
26
Drawn by Ian Compton
From Onsite Wastewater Treatment and Disposal Systems, EPA Design Manual
24
Figure 16: Infiltration Bed27
7.2.2 Treatment Decision Matrix
With many treatment options it was necessary to implement a decision matrix. The matrix seen in Table
8 is divided into preliminary treatment options and primary treatment options. Five characteristics are
used to evaluate each treatment process.
1) Passive
a) This was a constraint from HCJB and is critical for our design. Most treatments are either passive
or not. Three of the treatment options were in between because mechanisms are needed part
of the time to different degrees.
2) Maintenance
a) The facility will be maintained by villagers who may not be experienced with wastewater
treatment processes. The only maintenance will be in the form of manual labor. Therefor the
decision of the numerical value was based on frequency and amount of labor needed.
27
Drawn by Ian Compton
25
3) Footprint
a) The treatment facility needs to fit in a particular location in Carabuela. The current size of the
land available is unknown yet the matrix is giving treatment options with a smaller footprint
preference.
4) Cost
a) The main cost of the treatment facility will be the materials that need to be brought into the
village. Manual labor will be provided for construction. Therefrom the amount of piping drives
the cost characteristic
5) Quality
a) The wastewater needs to be treated effectively. The options presented all provide sufficient
treatment. However the value of quality was based on how quickly and now much wastewater
could be treated.
The characteristics were weighted to give particular characteristics a greater importance. Each of the
treatment options was given a rating in a characteristic from worst, 1, to greatest, 10. Three treatment
options stood out from the rest of the options. These are the most desired treatments to implement.
However, the different combinations of the options will dramatically increase the effectiveness of the
system. Several system combinations will be looked at.
Table 8 : Decision Matrix
Characteristic
Weight
Preliminary
Bar Screens
Grit removal
Primary
Waste Stabilization Ponds
Trickling filter
Septic Tank
Constructed Wetlands
Ground Infiltration
Passive
Maintenance Footprint
Cost
10
6
7
Quality
8
Total
6
370
10
5
8
8
10
10
8
5
4
3
306
226
10
5
8
10
10
6
4
4
8
8
3
7
6
4
8
10
5
6
4
8
8
9
7
8
8
285
217
236
256
316
26
7.2.3 Selected Treatment Design Alternatives
7.2.3.1 Waste Stabilization Ponds
The most important design parameters for waste stabilization pond design are temperature, net
evaporation, flow, and BOD inflow. Table 9 shows the parameters used to size the ponds. The flow used
is the 20 year projected flow. We used an estimate of 30 gcd28 for BOD concentration, which results in a
wastewater BOD of 287 mg/L. Net evaporation rate data was hard to find so a conservative estimate
was used. A pan test needs to be conducted to more accurately define the net evaporation rate. The
target reduction of the fecal coliform per 100 ml of wastewater is <10 4.29 This will allow the treated
effluent to be used for restricted irrigation based on WHO standards. Figure 17Figure 2 shows the
potential layout for the waste stabilization ponds. There are two sets of anaerobic, facultative, and
maturation ponds connected in parallel. The ponds connected in parallel provide redundancy so that a
pond can be shut down for desludging while the system remains operational. The additional ponds also
provide the desired removal of fecal coliform to provide an effluent suitable for irrigation purposes. The
pond sizing required to produce an effluent of 1767 fecal coliform per 100 ml of wastewater is given in
Table 10. This effluent would be clean enough for restricted irrigation. In order to achieve a cleaner
effluent the ponds would need to be larger or have the influent pretreated. The area of land available
will be determined upon visiting the site. The preferred placement of the ponds would be at a higher
elevation so that the treated effluent can be conveyed to irrigation fields without installing pumps.
Figure 17 : Waste Stabilization Pond Layout
28
29
http://www.unep.or.jp/Ietc/Publications/Water_Sanitation/ponds_and_wetlands/Design_Manual.pdf. 20
WHO, . Guidelines for the Safe Use of Wastewater, Excreta and Greywater, Volume 1: Policy
and Regulatory Aspects. Geneva: World Health Organization, 2006. Internet resource. 27
27
Table 9 : Waste Stabilization Pond Design Parameters
Parameter
temperature (C°)30
net evaporation rate (mm/day)
flow (L/day)
BOD5 (mg/L)
Volumetric Loading (gm/day/m3)31
Anaerobic Pond Depth (m)
Facultative Pond Depth (m)
Maturation Pond Depth (m)
Surface Loading (kg/hectare-day)
Fecal Coliform/100 ml of Wastewater
Value
16
4.2
479700
287
200
3
1.5
1
262
10,000,000
Table 10 : Pond Sizing
Quantity
Retention
Time (days)
Size (m2)
Anaerobic
2
1.43
127
Facultative
2
8.54
1512
Maturation
2
4.47
1186
6
14.44
5650
Pond
Total
7.2.3.2 Infiltration Beds
A set of infiltration is also proposed as a discharge mechanism for the treated effluent. This will
discharge the effluent to the ground water, as long as there are suitable soils and a low enough water
table. This process will deliver a treated effluent that should be of suitable quality to release into the
environment and not damage wildlife or pollute water sources.
Not many design specifications can be finalized before a visit to the village. This is because infiltration
relies heavily on the soil type in the area. Different soil types allow for different rates of application to
the beds. Some recommended rates can be seen in Table 11.
30
31
www.weather.com
http://www.unep.or.jp/Ietc/Publications/Water_Sanitation/ponds_and_wetlands/Design_Manual.pdf. 21
28
Table 11: Recommended Rates of Wastewater Application for Trench and Bed Bottom Areas a32
Soil Texture
Gravel, coarse sand
Coarse to medium sand
Fine sand, loamy sand
Sandy loam, loam
Loam, porous silt loam
Silty clay loam, clay loamd
Percolation Rate (min/in)
<1
1–5
6 – 15
16 – 30
31 – 60
61 - 120
Application Rateb (gpd/ft2)
Not suitablec
1.2
0.8
0.6
0.45
0.2e
a
May be suitable for sidewall infiltration rates
Rates based on septic tank effluent from a domestic waste source. A factor of safety may be desirable for wastes of
significantly different character.
c Soils with percolation rates <1 min/in can be used if the soil is replaced with a suitably thick (>2ft) layer of loamy sand or sand.
d Soils with expandable clay
b
7.2.3.3 Residuals33
Periodically, bio-solids must be removed and disposed of properly in order to keep the treatment
process in an optimal condition. In the preliminary design, the main source of residuals will be from the
bar screens and waste stabilization ponds. Waste stabilization ponds will need to be routinely cleaned
about once a year. The solids removed will have high concentrations of BOD, suspended solids, grease,
hair, grit and disease-causing pathogens.34 This requires care in their disposal in order to maintain
healthy conditions.
In the United States, the largest volume of residuals comes from septic tanks. This is called septage and
is handled in a variety of ways. Septage can be dewatered and spread over land; both on and under the
surface, buried in trenches, applied to a landfill, burned, composted, digested (both aerobically and
anaerobically), or treated with chemicals. In this design, many of the facilities and infrastructure used in
the United States are lacking. This limits options for residual removal in Carabuela.
For this design, we recommend composting the removed residuals. This option does not require much
equipment and can be done locally with little of the offensive odors associated with other methods.
This is also much safer than some options and contains less risk of contaminating ground water.
Composting requires adding a “bulking agent” to the waste in order to help aerate the waste and
prevent stagnation. This requires periodic mixing of the waste with an organic agent such as wood chips
or shavings. These agents are readily available in the area and are easy to create. After a suitable
amount of time, most of the pathogens in the waste will be destroyed and the compost will be
acceptable to add to soil.
32
From Onsite Wastewater Treatment and Disposal Systems, EPA Design Manual
From Onsite Wastewater Treatment and Disposal Systems, EPA Design Manual
34
Table 9-1, Onsite Wastewater Treatment and Disposal Systems
33
29
7.3 Effluent
7.3.1 Effluent Targets
Due to comparatively lax wastewater effluent standards in Ecuador, finding suitable effluent quality
standards for the region were difficult to find. However, we did find Ecuadorian standards as listed in
Table 12. These standards are considerably weak and are even comparable to weak waste stream
influents.
Table 12 : Fresh Water Discharge Effluent Standards in Ecuador 35
Contaminant
BOD5
Total Suspended Solids
Nitrogen
Phosphorous
pH
Fecal Coliform Bacteria
Standard Concentration
100 mg/L
100 mg/L
10 mg/L
10 mg/L
5–9
Removal >99.9% or 0
eggs/L
for
use
in
agriculture
After looking into effluent standards by the EPA, Michigan Department of Quality, and the World Health
Organization, we compiled a set of standards as seen in Table 13.
Table 13 : Michigan Department of Environmental quality Standards for discharge into Ground Water
Contaminant
CBOD
TSS
Total Phosphorous
Total Inorganic Nitrogen
pH
Sodium
Chloride
Concentration
25 mg/L monthly average;
40 as 7-day average
30 mg/L monthly average;
45 as 7-day average
5 mg/L
10 mg/L
6.5 - 9
150 mg/L
250 mg/L
35
From Ecuadorian Congress: NORMA DE CALIDAD AMBIENTAL Y DE DESCARGA DE EFLUENTES :
RECURSO AGUA LIBRO VI ANEXO 1
30
7.3.2 Irrigation Feasibility
Until more information is gathered, we cannot confirm the feasibility of using the treated effluent as an
irrigation source. This is due mainly to the lack of information regarding the layout of the village. If
most of the agricultural fields are downhill of the village, it may be quite possible to have a gravity feed
to the effluent to the farmland. However, if most of the fields are at a higher elevation than the
treatment facility, then it may no longer be feasible for the village to use the effluent stream as an
irrigation source. This part of the project will be put on hold until information can be gathered from the
village.
8. Construction and Maintenance
Construction of the project will be completed by HCJB, if chosen to be implemented. Labor then will be
provided by either the organization or the village itself. It still remains unknown what type of
equipment HCJB has at their disposal in order to build the proposed treatment facility. The infiltration
bed especially requires delicate construction methods so as not to damage the soils or disturb its
permeability.
Maintenance is projected to be relatively low. The proposed treatment process is designed to be a
passive process only requiring routine maintenance and cleaning. Dosing of the infiltration bed will
need to be changed periodically to perform optimally. This can perhaps be done on a daily or weekly
basis. The bar screens will need to be raked on a need basis. Routine cleaning will have to be
performed on the ponds yearly. This will require draining the pond (one at a time) and removing the
accumulated solid residuals. The infiltration bed will also require periodical maintenance if a biofilm
mat begins to develop on the surface of the soil media.
9. Costs
9.1 Team Costs
Team 7 requests $6100 as its total budget for the academic year. This amount is not feasible based on
the class’s budget so we are requesting the initial allotted $500 with whatever extra can be added if
funds permit. To attain the rest of the funds, our team is applying for the Innotec grant and raising our
own support. Currently, we have raised $2300 of our own support so far. Table 14 shows all the costs for
the team.
31
Table 14 : Breakdown of Trip Costs
Trip Costs (9 days)
Per Day
Airfare (round trip)
Based on Hotwire.com
Daily Costs ($/day)
As given by HCJB
Per Person
$55
Totals:
Total for Team
$1,050
$4,200
$495
$1,980
$1,695
$6,180
9.2 Project Costs
The project costs are divided into three parts: design work, collection system costs, and treatment
system costs. No labor or excavation costs were included because our client requested them to be left
out.
9.2.1 Treatment System Cost
The estimated initial treatment costs are shown in Table 15. These are based on the EPA cost curves of a
lagoon construction costs.
Table 15 : Initial Estimated Wastewater Treatment Facility Costs
3-Phase
Treatment
Plan
View
Area
(Pond)
Anaerobic
Depth
Volume
SI
Volume English
Retention
Rate
(m2)
254
(m)
3
(m3)
762
(ft3)
26910
(Days)
1.43
Facultative
maturation
3024
2372
1.5
1
4536
2372
160190
83766
8.54
4.47
Totals:
5650
8000
282517.3
14.44
Cost
(1979 US
$)
$2,200.00
$20,000.0
0
$4,500.00
$26,700.0
0
Cost
(2012 US
$)
$4,510.00
$41,000.0
0
$9,225.00
$54,735.0
0
9.2.2 Collection System Costs
Initial estimated collection system costs are shown in Table 16. Values are very high right now because
this is for the entire village and approximately half is already in place so a good amount of the costs are
already covered. Because we don’t know which part or where it is this is the overall cost of what the
whole village would be.
32
Table 16 : Initial Estimated Wastewater Collection System Costs
Initial Pipe Costs (PVC and Concrete)
10" Pipe
8" Pipe
Length (m)
5051.3
3125.7
Concrete Pipe
$20.10
$17.40
Cost ($/m)
Cost ($):
PVC Pipe Cost
($/m)
Cost ($):
6" Pipe
3326.4
$15.60
$101,531
(Cheapest)=>
$47.37
$54,387
$51,892
Total Cost ($) $207,810
$33.36
$24.87
$239,280
$104,273 $82,728
Total Cost ($) $426,281
9.2.3 Design Costs
The team is made up of for engineers. Each will generate an average of 8 hours in a week. The rate for
work is an industry standard for covering the overhead costs of an engineering firm. The total costs are
over 14 weeks, the first semester as seen in Table 17.
Table 17 : Initial estimated Design Costs
Number of
Hours Per Week
8
8
8
8
Hourly Cost
100
100
100
100
Weekly Cost
$800.00
$800.00
$800.00
$800.00
Total
Total Costs
$11,200.00
$11,200.00
$11,200.00
$11,200.00
$44,800.00
9.2.4 Cost Summary
The project is large and we currently have no data parting to a possible distribution of the effluent to
surrounding farmland. Adding that portion would increase the project cost substantially. Table 18
shows out total costs. A contingency factor is within the extremely conservative design of the collection
system and the treatment facility. Yet we added a 15% contingency to the total because we are at such
an early stage of the design process.
33
Table 18 : Total Cost Estimate
Item
Trip
Design
Treatment Facility
Collection System
Total With 15%
Contingency
Cost
$6,200
$44,800
$54,700
$207,800
$360,525
The total cost of our Project is currently $360,525. This is not including the potential distribution of the
effluent, but it includes a 15% contingency.
10. Work Plan
10.1 Interim
The team will make final preparations for the trip to Carabuela at the end of January. This will involve
gathering of all necessary equipment and questions that need to be addressed. The main piece of
equipment that is still needed is a GPS unit for surveying the current wastewater collection system and
possible placement of new sewer lines. HCJB is planning on buying a new GPS unit. They could have it
sent to our team to bring with to practice with it and make sure it is compatible with the team’s laptops.
HCJB also has a theodolite to check the slope of the sewer drains. The major questions that need to be
addressed during the team’s visit are: What and how much land is available for treatment? What types
of crops are grown in the area? What on-site treatment is currently implemented? Where is the water
table high? What is the infiltration rate of the soil? How are the household connections to the
collection system regulated? A more finalized itinerary will be made as well during interim break.
10.2 Trip
The team will travel to Ecuador for the days of January 19-27. HCJB Engineer Cesar Cortez will
accompany the team to Carabuela till Engineer Bruce Rydbeck returns on the 22nd. Bruce will
accompany the team on January 24-26. Visiting engineers Andrew and Laura Price Rescola may also
accompany the team for several days. The team plans to hand over a copy of this report to HCJB to be
translated into Spanish and given to the community. This will provide value to collaboration between
the team and the village. The expected costs of the trip are in section 9.1 and the team will plan
accordingly.
34
11. Works Cited
“Gravity Sanitary Sewer Design and Construction”. ASCE Manuals and Reports on Engineering PracticeNo. 60.
Kayombo, Sixtus. Development of a Holistic Ecological Model for Design of Facultative Waste
Stabilization Ponds in Tropical Climates. Copenhagen: Royal Danish School of Pharmacy,
Department of Analytical and Pharmaceutical Chemistry, Section of Environmental Chemistry,
2001.
Kayombo, S., and T.S.A Mbwette. Waste Stabilization Ponds and Constructed Wetlands Design Manual
UNEP-IETC.
Mara, D. Domestic Wastewater Treatment in Developing Countries. London: Earthscan Publications,
2004. Internet resource
Onsite Wastewater Treatment and Disposal Systems: Design Manual. Washington, D.C: U.S.
Environmental Protection Agency, Office of Water Program Operations, 1980. Print.
Reynolds, Tom D., and Paul A. Richards. Unit Operations and Processes in Environmental Engineering.
2nd ed. Boston: PWS Publishing Company, 1996: 96.
UN Department of Technical Cooperation for Development. (1985) The use of non-conventional water
resources in developing countries. Natural Water Resources Series No. 14. United Nations DTCD,
New York.
Wastewater Technology Fact Sheet: Screening and Grit Removal. Washington, D.C.: U.S. Environmental
Protection Agency, Office of Water, 2003. Internet resource
WHO, . Guidelines for the Safe Use of Wastewater, Excreta and Greywater, Volume 1: Policy
and Regulatory Aspects. Geneva: World Health Organization, 2006. Internet resource.
World Weather and Climate Information. N.p., 2010-2011. Web. 7 Dec. 2012. <http://www.weatherand-climate.com/average-monthly-Rainfall-Temperature-Sunshine,Quito,Ecuador>.
35