Identification of Sustainable Alternative Applicable to North Engineering Toilets
Identification of the Most Sustainable Alternative System to be
used for Toilets in North Engineering Building of University of
Toledo: A Comparative Study of Implementation of Rain Water
Harvesting, Grey Water Recycling and Composting Toilets
By
Akhil Kadiyala
Zheng Xue
Andrew E. Wright, LEED A.P.
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
Table of Contents
1. Abstract ........................................................................................... 5
2. Introduction ................................................................................... 5
2.1 Economic Input output Life Cycle Assessment (EIOLCA) ..................................... 7
2.2 Indicators................................................................................................................... 8
2.3 Sustainability Index and Performance Percentage .................................................... 9
2.4 LEED Requirements ............................................................................................... 10
3. Data Collection ............................................................................. 10
3.1 Data collected from Maintenance Department and Survey .................................... 11
3.2 Data collected for Life Cycle Inventory of Life Cycle Assessment ....................... 13
4. Design of Alternative Systems ................................................ 13
4.1 Rainwater Harvesting.............................................................................................. 14
4.2 Grey Water Recycling............................................................................................. 17
4.3 Composting Toilets ................................................................................................. 22
5. Results ........................................................................................... 25
5.1 LCA Results ............................................................................................................ 26
5.2 Indicator Analysis Results ...................................................................................... 27
5.2.1 Environmental Pollution Indicator ................................................................... 28
5.2.2 Natural Resource Consumption Indicator ........................................................ 29
5.2.3 Economic Indicator .......................................................................................... 30
6. Sustainability Index and Performance Percentage .......... 32
7. LEED Credits ................................................................................. 32
8. Conclusion .................................................................................... 33
9. References .................................................................................... 34
Appendix A ........................................................................................ 37
Appendix B ........................................................................................ 44
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
List of Figures
Figure 2.1.1: System Boundary of LCA ............................................................................. 7
Figure 2.1.2: Inputs-Outputs of construction and O&M phases ......................................... 8
Figure 4.1 - Graph of present water consumption in restrooms ....................................... 14
Figure 4.1.1: Concept of Rainwater collection system .................................................... 15
Figure 4.2.1: Concept of Living Machine System to be used at UT. ............................... 21
Figure 4.3.1 - Clivus Multrum M18.................................................................................. 24
Figure 4.3.2 – Schematic of composting system .............................................................. 24
Figure 5.1: Water use Consumption and Waste Water Effluent ....................................... 26
Figure 5.1.1: Greenhouse gases for “Construction” and “O&M” Stages of a Life Cycle 27
Figure 5.1.2: Energy for “Construction” and “O&M” Stages of a Life Cycle ................. 27
Figure 5.2.2.1: Average daily water savings (gal/day) for different systems ................... 29
Figure 5.2.3.1: Economical Choice Comparison based on Cost of Construction and O&M
........................................................................................................................................... 30
Fiigure 5.2.3.2: Economical Choice based on Cost/gal of water saved/day ..................... 31
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
List of Tables
Table 2.2.1: Indicators used for comparing the three systems ............................................ 9
Table 3.1.1: Details of Restroom Fixtures in North Engineering Building ...................... 12
Table 4.1.1 – Rainwater Harvesting Estimate1 ................................................................. 16
Table 4.1.2 – Rainwater Harvesting O&M ....................................................................... 16
Table 4.2.1: Effluent characteristics as observed in universities ...................................... 18
Table 4.2.2: Estimated Costs for Construction of Grey Water ......................................... 22
Table 4.2.3: Annual Costs for Operation and Maintenance of Grey Water ..................... 22
Table 4.3.1 – Proposed Composting System for NE ........................................................ 25
Tables 5.2.1 – Water Consumption Analysis from EIO-LCA .......................................... 28
Table 6.1: Sustainability Index and Performance Percentage Values .............................. 32
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
1. Abstract
This study compares the degree of sustainability and performance across three
different systems that could be practically adopted by The University of Toledo (UT) to
help conserve water for future generations. The systems considered were rainwater
harvesting, greywater recycling and composting toilets. Over the last decade, the role of
these three systems in reducing water consumption had been widely recognized across
the world and many buildings are currently using these systems either individually or in
combinations. While all three systems are capable of reducing the potable water usage in
toilet flushing in North Engineering (NE) building of UT, each system has its own
method of water conservation. Rainwater harvesting uses the collected rainwater as an
additional source of supply for toilet flushing while greywater treatment enables the reuse
of treated greywater from university for toilet flushing. Composting toilets reduce the
water consumption as they consume minimum amount of water per flush and no water in
some cases. None of the studies so far have compared these three systems that have
different ways of conserving water from a sustainability point of view and this study aims
at filling this knowledge gap.
This study provides two approaches of comparing these systems. Based on the
LCA and indicator analysis performed by the group, it was inferred that composting
toilets were found to be the most sustainable alternative system to reduce water
consumption at UT. However, it is also preferable to have greywater recycling for
maximum water conservation as the grey water produced by the university accounts for
almost 35% total water consumed by university.
2. Introduction
The College of Engineering at The University of Toledo has proposed to renovate
the North Engineering building in order to facilitate bringing all the students, faculty and
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
administrative services within the main campus. The College of Engineering has heavily
emphasized on the need to use sustainable alternatives during the renovation work. This
project is being performed as part of evaluating the sustainable options of water use
consumption for toilets and urinals in the North Engineering building that include the use
of rain water harvesting, grey water recycling and composting toilets.
Rainwater harvesting has been used mainly for agricultural usage and landscape
irrigation. It was found that rainwater harvesting has not been thoroughly studied in a
sustainable aspect for its uses for water to be recycled through toilet and urinal flushing.
Over the years, the number of studies that have focused on using recycled grey water for
toilet flushing has been increasing and the standards for recycled grey water vary from
one country to another. Lazarova et al. (2003) provided a comprehensive review of the
various studies that have used recycled grey water for toilet flushing and documented the
grey water quality criteria that needs to be adopted across different countries. The use of
composting toilets has shown to reduce the amount of water needed and therefore
reducing the amount of effluent going to waste water treatment plants (WWTP). There
were no studies found that have focused on comparing the performance of these systems
with respect to sustainability.
The overall objective of the study is to determine the most sustainable alternative
system that can be applied to NE building at UT to reduce the water consumption,
thereby identifying the possibility of obtaining LEED points for better management
practices. The approaches used by the researchers in meeting the objectives are listed
below and discussed in detail in subsequent sections 2.1-2.4.
1. Use ‘EIOLCA’ to determine the most suitable system by considering
‘construction’ and ‘operation and maintenance’ phases in a life cycle across
the impact categories of greenhouse gases and energy.
2. Use different sustainable indicators as listed in Table 2.1.1 to analyze the
performance of the systems.
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
3. Choose the most sustainable alternative system that could be adopted in toilets
at the NE building based on sustainability index and performance percentage
values.
4. Identify the possibility of obtaining LEED points for better management
practices.
2.1 Economic Input output Life Cycle Assessment (EIOLCA)
EIOLCA was used to compare the three systems based on the economic inputs for
each system obtained by designing of individual components for the systems and
obtaining cost estimates for each component in the system. EIOLCA was used to
identify the most sustainable alternative system from rainwater harvesting, grey water
recycling, and composting toilets to reduce water consumption by toilets in NE block at
UT using the phases of “Construction” and “Operation and Maintenance” across impact
categories of greenhouse gases and energy.
Figure 2.1.1: System Boundary of LCA
Figure 2.1.1 presents the boundaries of the system adopted by the research group
that is similar to the system boundary concept discussed by Memon et al. (2007). Only
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
the construction and O&M phases are considered while transportation and energy
required in material manufacturing and transport are neglected. To compare the three
technologies we use the savings per life cycle of each system ($/life cycle) as a functional
unit. It should be noted that only the raw materials for construction phase products will be
considered but not the raw material extraction at manufacturing phase.
Figure 2.1.2 shows that the construction and O&M phases require the
manufactured material and energy (electricity) as inputs for the three systems. The
resulting outputs from these operations are atmospheric emissions, energy, and savings
due to adoption of any of the systems. The life cycle assessment for these operations is
performed using EIOLCA tool. Costs for manufactured materials for the different
systems were obtained from online websites or open literature and are cited in the design
sections. The energy consumption included electricity and the cost of electricity per kWh
is taken as 5.6 cents that was taken from an electricity bill in Toledo.
Figure 2.1.2: Inputs-Outputs of construction and O&M phases
2.2 Indicators
Table 2.2.1 summarizes the type of indicators and their corresponding points used
for comparing the three systems. Three different types of indicators namely economic
indicator, natural resource consumption indicator and environmental pollution indicator
are used to identify the most sustainable system from their perspectives.
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
Table 2.2.1: Indicators used for comparing the three systems
Type of Indicator
Economic
Points for comparison
Determine economical choice for construction and O&M
phases and calculate payback period for each system
Natural Resource
Consumption
Compare the quantity of water saved by each system per day
Environmental
Determine the amount of greenhouse gases released and
Pollution
energy requirements for each system.
2.3 Sustainability Index and Performance Percentage
In order to compare the three systems, the points for comparison listed in Table
2.2.1 are used as a series of questions that were classified under economic, environmental
and natural resource consumption indices. Points are allotted (‘3’ for best alternative, ‘2’
for intermediate alternative, and ‘1’ for last alternative) for each system for each question.
If two systems have no relative advantages then both of the systems are given equal
points for that particular question considered. The points are allotted based on the
relativity rather than on absolute basis. The points are summed up in the end to provide a
sustainable score to each of the systems considered. The best sustainable alternative
system is then identified based on ‘Sustainability Index’ and ‘Performance Percentage’
calculated using equations 2.3.1 and 2.3.2 respectively.
….2.3.1
….2.3.2
where,
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
Performance percentage = Maximum Score of indicator × ∑Sustainable Score.
2.4 LEED Requirements
The U.S. Green Building Council's LEED Green Building Rating System
establishes “best practice” criteria for water and energy usage that can be applied to any
type of construction, even if certification is not the goal. The Water Use Reduction
section of LEED-NC identifies a baseline for water use and awards one or two credits for
surpassing requirements, in aggregate by 20 percent or 30 percent, respectively, beyond
the Energy Policy Act of 1992 fixture performance requirements.
The categories that the research group analyzed for obtaining points in water
conservation are listed below.
 WE 2: Innovative Wastewater Technologies. The intent is to reduce generation of
wastewater and potable water demand, while increasing the local aquifer
recharge.
 WE 3.1: Water Use Reduction 20%. The intent is to maximize water efficiency
within buildings to reduce the burden on municipal water supply and wastewater
systems.
 WE 3.2: Water Use Reduction 30% has same intent as 3.1.
3. Data Collection
The data collected for the project can be divided into two categories. The first set
of data was collected from the maintenance department, and also a survey of utilities in
existing restrooms. This data helped to determine the existing water usage, and to predict
water savings by adoption of alternative techniques. The second set of data was collected
from various websites and open literature to estimate the quantity and costs of materials
that would be used in the life cycle assessment.
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
3.1 Data collected from Maintenance Department and Survey
Preliminary information on water source and drainage systems was obtained from
the maintenance department at UT. It was confirmed that only potable water obtained
from Lake Erie provided by ‘The City of Toledo Water Treatment Plant’ is being used
for all purposes including toilets at UT and there have been no recycling systems on
campus. A monthly water bill for north engineering building revealed that the university
was paying about $4277.00 for 1048 ccf (783,904 gallons). All of the waste water from
toilets, sinks, sinks in labs, maintenance sinks and floor drains, and urinals are combined
together before discharge and there are no provisions for separate discharges from sinks
and toilets. In this study, we assume that 90% of this water is being released into the
city’s sanitary system. An in depth comparison of each system is presented for its water
reduction benefits and sustainability.
An initial survey was performed to find out the makes and model fixtures used in
the restrooms of the north engineering building. The maintenance department could only
provide information on the number of toilets in north engineering building and their floor
plans. A walk through of existing facilities provided information on the number of
fixtures and manufacturing company of the fixtures. The flow rates were obtained from
online web search after getting the company and model numbers for the different fixtures.
A summary of the restroom fixtures used in the North Engineering building are given in
Table 3.1.1.
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
Table 3.1.1: Details of Restroom Fixtures in North Engineering Building
Room No
Type of Utility
Company /
Manufacturer
Crane Plumbing
Zurn
Zurn
Flow rate
Faucets
Urinals
Toilets
No. of facilities
in the room
3
2
3
1262
1260
Faucets
Toilets
2
3
Crane Plumbing
Zurn
NA
1.6 g/f
2014
Faucets
Urinals
Toilets
3
2
3
Kohler
Sloan
Sloan
NA
1.6 g/f
1.6 g/f
2013
Faucets
Toilets
3
5
Kohler
Sloan
NA
1.6 g/f
2053
Faucets
Urinals
Toilets
3
2
3
Kohler
Sloan
Sloan
NA
1.6 g/f
1.6 g/f
2056
Faucets
Toilets
3
5
Kohler
Sloan
NA
1.6 g/f
1012
Faucets
Urinals
Toilets
3
2
3
Kohler
Sloan
Sloan
NA
1.6 g/f
1.6 g/f
1013
Faucets
Toilets
3
5
Kohler
Sloan
NA
1.6 g/f
1055
Faucets
Urinals
Toilets
3
2
3
Kohler
Sloan
Sloan
NA
1.6 g/f
1.6 g/f
1056
Faucets
Toilets
3
5
Kohler
Sloan
NA
1.6 g/f
0520A
Faucets
Urinals
Toilets
3
2
3
Kohler
Sloan
Sloan
NA
1.6 g/f
1.6 g/f
0600
Faucets
Toilets
3
5
Kohler
Sloan
NA
1.6 g/f
Page 12 of 47
NA
3.0 g/f
1.6 g/f
Identification of Sustainable Alternative Applicable to North Engineering Toilets
3.2 Data collected for Life Cycle Inventory of Life Cycle Assessment
The data collected for use in the EIOLCA that included parameters such as
materials, quantities, and their respective costs were obtained from various websites and
available open literature. Once the cost of construction and O&M were determined after a
careful design of the individual systems, EIOLCA was used to perform the life cycle
assessment.
4. Design of Alternative Systems
The design of alternative systems is based on the water requirement for toilet
utilities in NE block of UT. The amount of water required for toilet utilities in NE block
can be seen in Figure 4.1 It is assumed that there will be 2370 people in the building per
day based on the size of the classrooms and staff offices. The number of people is based
on the maximum seating in the laboratories, classrooms and offices. It is also assumed
that all persons in the building will use the restroom 1.5 times a day on average. It is
assumed that the students are 75% male and 25% female and that the males will use the
urinals and toilets in equal portions of their 1.5 times per day. This equates to 237,420
gallons per month used by the restrooms or 30% of the total water used in the building at
a cost per month of $1,283. The annual estimate is then $15,480 for 2,849,040 gallons of
water used by the restrooms only.
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
Figure 4.1 - Graph of present water consumption in restrooms
4.1 Rainwater Harvesting
Rainwater harvesting is the process of intercepting storm-water runoff and putting
it to beneficial use. Rainwater is usually collected or harvested from rooftops, concrete
patios, driveways and other impervious surfaces. Buildings and landscapes can be
designed to maximize the amount of catchment area, thereby increasing rainwater
harvesting possibilities. Intercepted water can be collected, detained, retained and routed
for use in toilet and urinal flushing.
Rainwater harvesting systems vary from the simple and inexpensive to the
complex and very costly. Typically, these systems are simple, consisting of gutters,
downspouts, and storage containers. Directing rainfall to plants located at low points is
the simplest rainwater harvesting system. Figure 4.1.1 presents a proposed system that
the north engineering building would utilize for the use of flushing toilets and would
include the following design criteria:

All the roof rainwater is collected at a general point and distributed to
the collection tank
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Identification of Sustainable Alternative Applicable to North Engineering Toilets

Prior to the rainwater entering the collection tank it is filtered via a ground filter.

The rainwater is then pumped to a header tank located on the roof

Prior to reaching the header tank it is disinfected via the ultra violet process

The rainwater is distributed to the WCs via the header tank which incorporates the
main water back up, riser connection and overflow.
This system virtually reduces the water needed for toilet flushing as long as the
tank(s) are sized to handle the daily flushing needs. Design considerations take into
account any drought conditions during summer months, given the fact that peak usage is
during the months August through May during college semesters.
Figure 4.1.1: Concept of Rainwater collection system [Greywater Reuse and
Rainwater Harvesting]
It was found that a rainwater harvesting system designed for the NE building
would cost approximately $262,757.17 as shown in Table 4.1.1. Table 4.1.1 presents an
estimate for the costs of installing a rainwater collection system and using the water for
flushing toilets and urinals. The tanks would be located outside of the building and could
range in any size depending on area designated for storage. The total volume needed for
the rain water tank(s) would need to be 240,000 gallons based on a maximum dry season
of 1 month in this area, multiplied by days, multiplied by required amount of water
needed (5691×30 = 170,730 gallons). In this study we are using 2 tanks at the size of
90,000 gallons each. The system would pump water to a header tank located on top of
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
the roof. The size of the header tank would need to be approximately 6,000 gallons based
on the daily usage requirements of 5691 Gpd. Each tank would have a Self Cleaning
Inlet Filter and a floating tank filter. The system would need to use 6” PVC pipes to
direct the rainwater from the roof downspouts to the holding tanks. There will also be 2”
PVC pipes installed from holding tanks to the Header tank and 4” PVC pipes from the
header tank to existing piping inside of the building to toilets and urinals. For practicality
of this study prices include installation and do not include unforeseen factors not
designed for and are not in the estimate. It is assumed by the group that at a minimum
the rainwater harvesting system would require the items as mentioned.
Table 4.1.1 – Rainwater Harvesting Estimate1
Rainwater Harvesting Estimate
Quantity
Holding Tanks
2
Pipe from downspouts to holding tank
300
Pump-2 hp, 100 gpm
1
Self Cleaning Tank inlet Filter
2
Floating tank filter
2
6000 Gallon Header tank
1
2" pipe from holding tank to header tank 50
4" pipe back to toilets piping
700
1.
Unit
ea
lf
ea
ea
ea
ea
lf
lf
$
$113,783.00
$14.50
$965.00
$750.00
$220.00
$4,611.17
$11.50
$32.50
Total
$227,566.00
$4,350.00
$965.00
$1,500.00
$440.00
$4,611.17
$575.00
$22,750.00
$262,757.17
Estimate pricing was obtained from internet searches at http://www.watertanks.com/products/0035-220.asp
for the tanks and at http://stores.floridarainwaterharvesting.com/-strse-Rainwater-Harvesting-Products-clnFilters/Categories.bok for the filters and from RS Means Building Construction Cost Data 2008 copyright
2008.
Table 4.1.2 – Rainwater Harvesting O&M
Activity
Labor Charges
Cost
$80
Power Consumption by Pumps
Spare parts and Repairs
Total O&M Charges
Page 16 of 47
$42.34
$800
$922.34
Identification of Sustainable Alternative Applicable to North Engineering Toilets
The benefit of this system is the use of collected rain water instead of using
potable water for flushing toilets and urinals. The use of rainwater collection would also
slow down the amount of water entering the municipal storm water system. The only
disadvantage of a system such as this would be the maintenance. Depending on the life
of the equipment, location of equipment, and ease of installation would mandate the
amount of maintenance needed. It was calculated that the operation and maintenance for
a system such as this would be approximately $922.34 per year as shown in Table
4.1.2. This was based on the need to replace and/or clean filters in the system twice a
year. The cost of operation for the system is based on a 2 Hp Pump at 100 gpm running
everyday for 80 minutes. This is equivalent to 1.5 kW per hour which is a total of 2 kWh
per day or a maximum total of 730 kWh per year. The cost for operation is then 730
kWh × $0.056 = $42.34 per year.
4.2 Grey Water Recycling
Grey water is the waste water resulting from the performance of various activities,
which involves using bathroom sinks, tubs, showers, laundry, kitchen sinks, dishwaters,
etc. and doesn’t involve any hazardous waste discharge or drainage from toilets and
urinals. Grey water, with proper treatment can be used for various water reuse
applications like irrigating lawns and flushing of toilets. Sunderan and Wheatley (1998)
observed that lavatories account for nearly 65% of water consumption in universities
which shows that adopting recycled grey water can decrease considerable amounts of
water consumption. The characteristics of effluent grey water coming out from the UT
can be assumed to be similar to the findings of Holden and Ward (1999) and Surendan
and Wheatley (1999) and are tabulated in Table 4.2.1.
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
Table 4.2.1: Effluent characteristics as observed in universities
Source
College
Large
College
BOD5
(mg/l)
80
COD
(mg/l)
146
Turbidity
(NTU)
59
NH3
(mg/l)
10
P
(mg/l)
-
Total
Coliforms
-
96
168
57
0.8
2.4
5.2×106
It is important to treat grey water to meet the U.S EPA guidelines of having a
BOD5 of 10mg/l, E.Coli of 1CFU/100ml, turbidity of 2NTU, pH of 6-9, and chlorine
residuals of 1mg/l before using it for toilet flushing. There are different types of grey
water treatment systems that help in meeting the required standards. Any grey water
recycling system will have the following components.
 Greywater Source
 Collection through plumbing
 Treatment System
 Storage
 Greywater Reuse
Sinks act as the main source of grey water in the NE building. All of the water
coming from the sinks would be collected using a 6˝ PVC pipe and transported to the
equalization tank where the collected grey water is treated using a suitable treatment
system and then the treated effluent is pumped back to the toilets.
A review of literature helped identify the various treatment methods currently
being used for many buildings around the world. Some of the well-known grey water
recycling systems currently being used are:
1. Basic Two-Stage System.
2. Physical and Physiochemical System.
3. Biological Treatment System (MBR, BAF, RBC).
4. Constructed Wetlands (Living Machines).
5. Chemical Treatment System (MCR).
6. Green Roof Water Recycling System (GROW).
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
A basic two-stage system involves coarse filtration using a metal strainer and
disinfection using either chlorine or bromine applied regularly. This process was used in
a study by March et al. (2004) where a hotel used filtration, sedimentation and
disinfection to recycle grey water for toilet flushing. This type of system however needs
to be considered only when lower treatment standards are sufficient as in some cases it
failed to maintain the coliform levels within the required standards regularly. The
physical process includes the use of sand and/or membrane filters with pre-treatment for
membrane filters while physiochemical systems work using coagulation and advanced
oxidation. This type of system imparts higher process costs due to higher energy
requirements. The application of this process for on-site greywater treatment and reuse in
multi-storeyed buildings is discussed by Friedler et al. (2005). The biological treatment
system is mainly used to remove the biodegradable material and is widely used in hotels
or places where the systems are large and the effluent is of a high quality [Merz et al.
(2007), Nolde (1999), Friedler and Hadari (2006), Atasoy et al. (2007)]. Membrane
bioreactors (MBR), biologically aerated filters (BAF), and rotary biological contractor
(RBC) are generally used to assist in biological treatment. The working of a chemical
treatment system (MCR) is similar to that of an MBR. Wetlands and green roof water
recycling systems are environmentally friendly [Memon, 2007] and also have a better
treatment efficiency as compared to other treatment systems.
The treatment system adopted for design of grey water recycling for the NE
building is a tidal wetland living machine system. This system was selected because it is
environmentally friendly, has higher treatment efficiency, and treats large quantities of
grey water. The hydraulic and organic loading rates are calculated using the equations
4.2.1, 4.2.2 and 4.2.3.
……….4.2.1
……….4.2.2
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
….4.2.3
In general, hydraulic flow rates of 0.25 to 1 gal/ft2/day and 3 to 10 gal/ft2/day are
used for fixed fine media and recirculating in fine media several times while organic
loading rates may vary from 0.00025lbs BOD5/ft2/day to 0.0012 lbs BOD5/ft2/day for fine
media fixed films [The Ohio State University Report, 2007]. The OSU report, 2007 also
states that the problem of clogging can be reduced by having lower dosage of the order of
up to 3 doses per hour and helps to facilitate higher organic and hydraulic loading rates.
Figure 4.2.1 provides a layout of a living machine at Port of Portland where the
treated domestic waste water is used for toilet flushing. The group used a similar design
to be adopted by Worrell Water Technologies, LLC for treating grey water at UT. The
grey water collected from different sources is first transferred to the equalization tank
through a series of horizontal and vertical pipes. After studying the plumbing system for
NE block, it was observed that rather than completely changing the piping system
(vertical and horizontal piping), it would be economical if only a 6" PVC pipe is provided
along the circumference of NE block at level 1 to collect grey water from vertical pipes
located at different positions in the building. The primary/equalization tank helps reduce
the fluctuations in flow through wetlands where simultaneous nitrification, denitrification,
and BOD removal occur as a result of “drain and fill” operation. The effluent from tidal
wetlands is disinfected and stored in a storage tank placed on the roof of the NE block
and the reclaimed water is sent back to the toilets for flushing through the plumbing
system under the force of gravity.
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
Figure 4.2.1: Concept of Living Machine System to be used at UT [21].
The design of the grey water recycling system also includes provisions for screens
along with an equalization tank, plumbing system with PVC pipes, suitable filter media
that includes gravel and sand, and reed bed plants. The calculations associated with
design flow, hydraulic & organic loading rates and energy consumption are shown
below:
Assuming that about 35 percent of the water consumed by the north engineering
building is grey water [Sunderan and Wheatley, 1998]; the design flow obtained is
274,366.4 gal/month ≈ 9,145.55 gal/day. Tidal wetlands requires about 150 ft2 for every
1000 gallons treated per day. Hence, considering 12,000 gal/day (including a margin of
safety) the area required for tidal wetlands is 1800 ft2. The hydraulic loading rate as
calculated from equation 3.2.1 is 6.67 gal/day/ft2 [12,000 Gpd/1800 sq.ft] that is good to
maintain medium hydraulic rate for recirculation. Considering the effluent BOD to be
a maximum of 10mg/l according to U.S norms and tidal wetland treatment efficiency
the organic loading rate calculated using equations 4.2.2 and 4.2.3 is 0.00055 lbs
BOD5/ft2/day which is also good as it is within the limits of 0.00025lbs BOD5/ft2/day
to 0.0012 lbs BOD5/ft2/day. The designed system treats all of the grey water coming from
NE building and any excess water can be diverted to maintaining lawns and grass areas at
Carter field.
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
The components/activities and costs associated with construction and O&M for
the designed tidal wetland living machine can be observed in Table 4.2.2 and table 4.2.3
respectively. (Refer to Appendix-A for detailed calculations).
Table 4.2.2: Estimated Costs for Construction of Grey Water
Components
Piping
Equalization Tank
Living Machine
Disinfection System
Pumps
Storage Tanks
Additional Charges
Total Construction Charges
Cost
$1,101.60
$11,108.12
$650,000
$244,000
$965
$ 4,939.04
$39,172.34
$950,321.10
Table 4.2.3: Annual Costs for Operation and Maintenance of Grey Water
Activity
Labor Charges
Power Consumption by Living Machines
Power Consumption by pump to lift water to storage tank
Spare parts and Repairs
Total O&M Charges
Cost
$1,040
$205
$4038.94
$5,222.98
$10,506.92
4.3 Composting Toilets
Composting toilets are one of the most direct ways to avoid pollution and
conserve water and resources. Composting toilets can be waterless or consume a
minimum amount of flushing water, thereby reducing the water consumption rate. The
working principle of composting toilet is that human waste is converted into an organic
compost and usable soil by microorganisms that help in natural breakdown to essential
nutrients. Typically, the waste breaks down to 10% of its original volume [Del Porto and
Page 22 of 47
Identification of Sustainable Alternative Applicable to North Engineering Toilets
Steinfield, 1998]. The resulting end product is a stable soil like material called humus,
which can be either buried or used as a soil conditioner.
The research group took into consideration the following factors when deciding
on the type of composting toilet system needed for the NE building: local regulation,
performance, lifestyle consideration, and installation constraints. Commercially used
composting toilets are of two types, manufactured composting toilet systems and sitebuilt composting toilet systems. Due to lack of precise performance data for site-built
systems or lack of guarantee by any standard organization, the design chosen would need
to be an approved NSF International manufactured composting toilet system.
The proposed system will have adequate ability to safely manage the excrement
for the amount of people who will use the system. There are a total of 46 toilets in NE
building. Assuming the average number of people in NE block being 2,370 (refer to
Appendix-A for a list of assumptions made) with their usage of toilet at 1.5 times per
person per day, number of times the toilets are used daily = 2,370 × 1.5 = 3,555 times.
Average no. of times toilets are being used daily = 3,555 / 46 = 77.28.
The capacity of a composting toilet is mainly related with the amount of
excrement, and not confined by the amount of urine. It is also assumed that the frequency
of defecating and urinating are in equal portion. In this case the actual daily use for each
toilet is nearly half cut. However, a margin of safety needs to be adopted to ensure that
the system is capable of handling any increase in the number of people at NE.
Composting toilet systems come either as self-contained system or central system.
A central system is preferable over self-contained system due to its advantages for ease in
construction and maintenance. The important aspect of a composting toilet system
installation is the location of the composting tank and air ventilation systems. Systems
with simple ventilation and a compact composting tank are preferable. With respect to
the above mentioned factors, the group chose to use the Clivus Multrum M18 model
manufactured by Clivus Multrum, Inc. This system has a capacity of 120 uses per day
and is applicable for public facilities. The advantages of this model are convenient
installation, long-term retention and infrequent handling of the end-product. An example
of the Clivus Multrum M18 model is shown in Fig 4.3.1.
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
Figure 4.3.1 - Clivus Multrum M18 [Clivus Spec Sheets]
Figure 4.3.2 shows a schematic diagram of the composting toilet system layout.
One can see that both the toilets in the first floor and the second floor share a single
composting tank towards the west part of the NE building. The proposed changes are
using foam flushing toilets in the second floor due to the convenience in setting up the
drain line, while using waterless toilets in the first floor as it can be connected to the
composting tank with a 14" straight chute for the standard model. The two restrooms on
floor 1 towards the eastern part of the building are also modified using foam flushing
toilets and collecting excrement in one composting tank for each restroom. Details of
replacements for existing toilets can be seen in Table 4.3.1.
Figure 4.3.2 – Schematic of composting system [Clivus Multrum, Inc.]
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
Table 4.3.1 – Proposed Composting System for NE
Room
Type of toilet
Number of toilets
1262
1260
1014
2013
1015
2014
1057
2053
1058
2056
Foam flushing
Foam flushing
Waterless
Foam flushing
Waterless
Foam flushing
Waterless
Foam flushing
Waterless
Foam flushing
3
3
5
5
3
3
3
3
5
5
Number of
composting tank(s)
1
1
5
3
3
5
It is recommended that about 30 foam flushing toilets, 16 waterless toilets and 20
sets of composting tanks be installed in NE building. Adopting these recommendations
would reduce the water usage by toilets in NE as much as 72.3% with an investment of
$105,180 for construction purpose while the maintenance and operating phase accounted
for $5,268. (Refer Appendix-A for detailed calculations). About 115 gallons of water will
be used for the composting system and 2223 gallons for sinks after adopting composting
toilets. So the daily water savings is 7914 – 115 – 2223 = 5576 gallons.
5. Results
The existing restroom facilities water consumption and the amount of waste water
effluent are summarized in Figure 5.1.1. This graph shows the required potable water
needed in the restrooms in gallons per day and the amount of waste water effluent in
gallons per day for existing conditions and the proposed conditions with rainwater (RW)
harvesting, grey water (GW) recycling, or composting toilets installed in the building.
Based on these conditions one can easily see that a modification to the existing system
using one of the proposed systems has significant results in the amount of water needed
on a daily basis. The following LCA and indicator results describe more detail on the
benefits for these systems.
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
Figure 5.1: Water use Consumption and Waste Water Effluent
5.1 LCA Results
The research group chose to use Mining and Utilities as the industry group list
with the industry sector #221300: Water, sewage and other systems to run the EIOLCA.
Figures 5.1.1 and 5.1.2 presents the variation of ‘construction’ and ‘O&M’ phases of life
cycle across impact categories of greenhouse gases and energy. It was observed that the
grey water recycling had significant environmental impacts as compared to rain water
harvesting and composting toilets and also is the leading energy consumer among the
three. The group also checked the cost of construction per quantity of water saved per day
for each system to account for the possibility of having higher environmental impacts and
energy for varying quantity of water treated by the three systems. The current scenario
suggests that composting toilets is the best sustainable alternative that can be adopted at
the north engineering building at UT.
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
Figure 5.1.1: Greenhouse gases for “Construction” and “O&M” Stages of a Life
Cycle
Figure 5.1.2: Energy for “Construction” and “O&M” Stages of a Life Cycle
5.2 Indicator Analysis Results
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
5.2.1 Environmental Pollution Indicator
Environmental indicators for each system shown previously in the LCA certainly
have different impacts. Utilizing the EIO-LCA for pollution reduction as it pertains to
water consumption; one can see the effect that water use reduction has on pollution.
Because the information obtained was an average month basis for costs and amount of
water used, this study assumed an average water use per day of 2,888,610 gallons per
year at a cost of $15,480.
The need for potable water use for toilet flushing would be the same for rainwater
harvesting and grey water recycling with 811,950 gallons per year at a cost of $4,348. If
using composting of toilets then the need for potable water would be 853,370 gallons
with a cost of $4,608. The environmental impact from the water savings is shown in
Table 5.2.1. and compares the LCA pollution amounts from the initial conditions with the
proposed conditions.
Gallons used per year were used for use of the LCA data as the
gallons per day the units were too small to compare.
Tables 5.2.1 – Water Consumption Analysis from EIO-LCA
Conventional Air Pollutants
Pre - Design
RW & GW
Post - Design
Composting
Water
Consumption
Cost/year
$
SO2
mt
CO
mt
Nox
mt
VOC
mt
LEAD
mt
PM
10
Mt
$15,480
$4,348
$4,608
0.020
0.006
0.006
0.034
0.009
0.010
0.016
0.005
0.005
0.059
0.017
0.018
0
0
0
0.002
0
0
Green House Gases
Water
Consumption
Cost
Pre - Design
RW & GW
Post - Design
Composting
$
GWP
MTCO2
E
CO2
MTCO2
E
CH4
MTCO2
E
N20
MTCO2
E
CFC
MTCO2
E
$15,480
$4,348
$4,608
121
34
36
10.9
3.07
3.25
72.2
20.3
21.5
37.8
10.6
11.3
0.106
0.030
0.032
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
5.2.2 Natural Resource Consumption Indicator
We consider the amount of water saved as a benchmark for the natural resource
consumption indicator. The quantity of water consumed on an average daily basis used
by toilets in NE building is 7914 gallon (refer Appendix-A), of which 5691 gallons are
used for flushing toilets and urinals while 2223 gallons are used for sinks. Figure 5.2.2.1
shows that the daily savings in water consumption on adopting rainwater harvesting,
greywater recycling and composting toilets are 5691 gal/day, 12000 gal/day and 5676
gal/day respectively. It can be observed that adoption of proposed greywater recycling
reduces the water consumption usage by NE buildings to as much as 45.92% (12000
Gpd×100/26130 Gpd) while rainwater harvesting and composting toilets reduce water
consumption by 21.77% (5691 Gpd×100/26130 Gpd) and 21.72% (5576 Gpd×100/26130
Gpd). Comparing the quantity of water saved by each system per day, greywater
recycling is considered to be the most efficient in potable water savings.
Figure 5.2.2.1: Average daily water savings (gal/day) for different systems
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
5.2.3 Economic Indicator
Figure 5.2.3.1 shows the comparison of three systems adopted from an
economical point of view. We considered the summation of cost of construction
and one years operation and maintenance charges to compare the economical
choice of investment. Figure 5.2.3.1 presented below shows that the order of
economical choice would be adopting the composting toilets followed by rain
water harvesting and greywater recycling. Since greywater recycling saved more
amount of water as compared to rainwater harvesting and composting toilets, the
group also compared the cost per gallon of water saved per day and similar
observations were made with regard to economical choice as illustrated in Figure
5.2.3.2.
Figure 5.2.3.1: Economical Choice Comparison based on Cost of Construction
and O&M
Page 30 of 47
Identification of Sustainable Alternative Applicable to North Engineering Toilets
Fiigure 5.2.3.2: Economical Choice based on Cost/gal of water saved/day
Payback period is calculated based on the annual water savings to regain the cost
of investment.
Cost of water from monthly utility bill = $0.0054/gal
Annual amount saved by using these three techniques = (Water Cost × Water savings/day
× 365 days)
Annual amount saved using rainwater harvesting, greywater recycling and composting
toilets are ($0.0054/gal × 5691 gal/day × 365days) $11,216.91, ($0.0054/gal × 12000
gal/day × 365days) $23,652, and ($0.0054/gal × 5576 gal/day × 365days) $10,990.30
Payback period is calculated using the equation given below.
Hence, payback periods for rainewater harvesting, greywater recycling and composting
toilets are ($262,800/$11,216.91) 23.42 years, ($950,321.10/$23,652) 40.18 years, and
($105,180/$10,990.30) 9.5 years respectively. Since composting toilets have less
Page 31 of 47
Identification of Sustainable Alternative Applicable to North Engineering Toilets
investment cost and quicker payback period, it is better to adopt composting toilets from
an economic perspective followed by rainwater harvesting and then greywater recycling.
6. Sustainability Index and Performance Percentage
The sustainable scores, sustainability index and performance percentage achieved
based on the points of comparison are tabulated in table 6.1.
Table 6.1: Sustainability Index and Performance Percentage Values
S.No Points of Comparison
Rainwater
Harvesting
Greywater
Recycling
Composting
Toilets
1
Economical choice of cost of
construction per gallon of
water saved per day
2
1
3
2.
Quantity of water saved per
day
2
3
1
3.
Environmental Pollution
2
1
3
Maximum Achievable Score
9
9
9
Sustainable Score Achieved
2+2+2 = 6
1+3+1 = 5
3+1+3 = 7
Sustainability Index
66.67
55.55
77.78
Performance Percentage
12
15
21
7. LEED Credits
Considering the reduction in water consumption based on toilet usage all three
systems are capable of obtaining a credit for WE 3.1. Greywater recycling, rainwater
harvesting and composting toilets would reduce the potable water usage by 21.77%,
21.77% and 21.72% respectively. This study only took into account the restroom
facilities and to achieve the LEED credits through water efficiency one would need to
Page 32 of 47
Identification of Sustainable Alternative Applicable to North Engineering Toilets
consider the building as a whole. Using a combination of systems, fixtures and other
criteria one would be able to obtain further credits.
8. Conclusion
The life cycle assessment and sustainability index values showed that the
composting toilet system is the most sustainable alternative recommended for water
conservation with respect to toilets in NE. However, there might be differences in
person’s perspective during design part that could change the choice of the systems. This
study did not take into account for complete life cycles of all materials and systems that
could have resulted in different selection. Even thought the rain water harvesting and
grey water recycling, for this study, only took into account the benefits of using the water
for flushing of toilets and urinals; the systems could also benefit the University in the use
of irrigation, diverting storm water, and possible laboratory uses. The use of composting
toilets in the NE building would benefit not only on the costs of water consumption but
would also benefit the environment by reducing greenhouse gases and energy required
for their existing systems. Greywater Recycling can be adopted by the university only on
a long term scale as the university produces significant amounts of grey water daily
(nearly 35% of total water consumed based on a study by Sunderan) that can reduce
potable water needs in other areas also where it is not required. Rain water harvesting can
also be used similarly but the source of supply to this system is dependent on rainfall and
seasons.
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
9. References
1. Agriclean
technology
Report,
2006.
Available
at
http://www.cals.ncsu.edu/waste_mgt/smithfield_projects/phase3report06/pdfs/B.1
.pdf, accessed November 22,2008.
2. Atasoy, E. et al. 2007. Membrane bioreactor (MBR) Treatment of Segregated
Household Wastewater for Reuse, Clean 2007, 35, 465 – 472.
3. BC greenbuilding code. Background Research - Greywater Recycling, October
2007.
<http://www.housing.gov.bc.ca/building/green/Lighthouse%20Research%20on%
20Greywater%20Recycling%20Oct%2022%2007%20_2_.pdf>
4. Carnegie Mellon University Green Design Institute. (2008) Economic InputOutput Life Cycle Assessment (EIO-LCA), US 1997 Industry Benchmark model
[Internet], Available from:<http://www.eiolca.net> Accessed 22 November, 2008.
5. C. K. Choi Building for the Institute of Asian Research
6. Clivus Multrum. Inc, Available at
http://www.clivusmultrum.com/products_basic.shtml, accessed on November 22,
2008.
7. Clivus Spec Sheets, Available at http://www.thenaturalhome.com/clivusm10.htm,
accessed on November 22, 2008.
8. Del Porto, D., Steinfeld, C. 1998. The Composting Toilet System Book. p15.
9. Environmental Sanitation, S.A. Esrey, U. Winblad et. al. 1999 SIDA. Sweden.
10. FEMP “Domestic Water Conservation Technologies.” 18 Mar. 2008 accessed at
<http://www1.eere.energy.gov/femp/pdfs/22799.pdf>.
11. Friedler, E., and Hadari, M. 2006. Economic feasibility of on-site grey water
reuse in multi storey buildings. Desalination, 190, 221-234.
12. Holden, B., & Ward, M. 1999. An overview of domestic and commercial re-use
of water. Presented at the IQPC conference on water recycling and effluent reuse,
16 December, Copthorne Effingham Park, London, UK.
Page 34 of 47
Identification of Sustainable Alternative Applicable to North Engineering Toilets
13. Joseph
Jenkins,
Humanure
Compost
Toilet
System
Instruction Manual, 2006.
14. Lazarova, V., Hills, S., Birks, R. 2003. Using recycled water for non-potable,
urban uses: a review with particular reference to toilet flushing, Water Science
and Technology: Water Supply, 3, 69–77.
15. Living
Machines
Presentation,
Available
at
http://www.edc-
cu.org/ppt/Living%20Machines.pdf, accessed November 22, 2008.
16. March, J.G. et al. 2004. Experiences on greywater re-use for toilet flushing in a
hotel, Desalination, 164, 241-247.
17. Memon, F. A. et al., 2007. Life Cycle Impact Assessment of Greywater Recycling
Technologies for New Developments, Environ Monit Assess, 129, 27–35.
18. Merz, C., Scheumann, R., El Hamouri, B., Kraume, M. Membrane bioreactor
technology for the treatment of greywater from a sports and leisure club,
Desalination, 2007, 215, 37-43.
19. Mikkelsen P.S., Adeler O.F. “Collected Rainfall as a water source in Danish
Households – What is the potential and what are the costs.” Water Science Tech.
Vol. 39 NO. 5, pp 49-56, 1999.
20. Nolde, E. 1999. Greywater reuse systems for toilet flushing in multi-storey
buildings – Over ten years experience in Berlin, Urban Water, 1, 275-284.
21. NEW FREIGHT RATES HIT STEEL TRADE, Special to The New York Times.
Jun 2, 2008, Sunday Section: Editorial, Page 30.
22. Port
of
Portland
Case
Study.
Available
at
http://www.livingmachines.com/docs/port_of_portland_case_study_final.pdf,
accessed November 22, 2008.
23. Sunderan, S., and Wheatley, A.D. 1998. Grey-Water Reclamation for NonPotable Re-Use, J.CIWEM, 12, 406-413.
24. The Ohio State University Report, 2007. Available at http://ohioline.osu.edu/aexfact/pdf/0756.pdf, accessed November 22, 2008.
25. United
States
Plastic
Corporation
(USPC),
Available
at
http://www.usplastic.com/catalog/product.asp?catalog_name=USPlastic&categor
y_name=13669&product_id=16587, accessed November 22, 2008.
Page 35 of 47
Identification of Sustainable Alternative Applicable to North Engineering Toilets
26. Waskom, R. Colorado State University Extension water resources “Graywater
Reuse and Rainwater Harvesting.” Colorado State University. 15 Feb. 2008
accessed at <http://www.ext.colostate.edu/pubs/natres/06702.html>.
Page 36 of 47
Identification of Sustainable Alternative Applicable to North Engineering Toilets
Appendix A
Design Calculations and Cost Estimations
Page 37 of 47
Identification of Sustainable Alternative Applicable to North Engineering Toilets
Calculations for Total Water Usage by Toilets and Urinals
Men
Toilets = 1778 people x .75 uses/day x 1.6 gal/use = 2134 gal/day
Urinal = 1778 people x .75 uses/day x 1.6 gal/use = 2134 gal/day
Sink = 2370 people x 1.5 uses/day x ½ gal/use = 1778 gal/day
Women
Toilets = 593 people x 1.5 uses/day x 1.6 gal/use = 1423 gal/day
Sink = 593 people x 1.5 uses/day x ½ gal/use = 445 gal/day
Total = 7914 gallons / day
Also given in section 4
Rain Water Harvesting Design Calculations and Cost Estimations
Rainwater Harvesting Estimate
Quantity Unit
$
Total
Holding Tanks
2
ea $113,783.00 $227,566.00
Pipe from downspouts to holding tank
300
lf
$14.50
$4,350.00
Pump
1
ea
$965.00
$965.00
Self Cleaning Tank inlet Filter
2
ea
$750.00
$1,500.00
Floating tank filter
2
ea
$220.00
$440.00
8000 Gallon Header tank
1
ea
$4,611.17
$4,611.17
2" pipe from holding tank to header tank
50
lf
$11.50
$575.00
4" pipe back to toilets piping
700
lf
$32.50
$22,750.00
$262,757.17
Use d
Page 38 of 47
$262,800.00
Identification of Sustainable Alternative Applicable to North Engineering Toilets
Grey Water Design Calculations and Cost Estimations
1. Estimating costs from purchases:
a. Construction Charges
Equalization Tank:
Total average daily flow = 12,000 gallons per day.
Total average hourly flow = 500 gallons per hour.
Since there is no data monitoring system available at UT, a worst case scenario of 1400
gal/hr is assumed as flow rate and an equalization tank is designed for this flow rate
assuming a retention time of 4 hrs.
Equalization tank Size = Flow × Retention Time
= 1400 gallons/hour × 4 hours = 5600 gallons.
The cost estimate for construction of this equalization tank is assumed to be similar to
that provided by Agriclean Technology Report (2006), where the equalization tank was
designed for 6000 gallons
Hence, cost of equalization tank (includes a tank, pump and control panel) = $11,108.12
Piping Cost
Direct purchase of 6"PVC pipes from United States Plastic Corporation (USPC) for a
circumference of 68 ft = $1,101.60
Living Machine Costing:
Since, Ohio has a cold climate the estimated cost of building a living machine with green
house is considered to be approximately $650,000 ($1,077,777 for 40,000 GPD as stated
in Living Machines Presentation).
Storage Tank Costing
Page 39 of 47
Identification of Sustainable Alternative Applicable to North Engineering Toilets
The storage tank is designed to meet the requirements of toilets and the excess water is
diverted to be used for watering Carter field which the maintenance department identified
as one of the major water consuming area at UT.
Total water used by toilets at NE block in UT = (2134+2134+1423) GPD = 5691 GPD.
Hence, required size of storage tank for toilet utilities ≈ 7800 gallons.
Cost of a 7800 gallon heavy duty vertical poly storage tank as observed in WaterTanks =
$ 4,939.04
Disinfection Unit:
Cost of UV disinfection unit based on EPA’s Waste Water Technology Factsheet =
244,000 (Capital Cost) + 19,190 (O&M) = $263,190
Additional Expenses:
Some miscellaneous charges of about 15% of the (Total Cost-Cost of Living Machine)
are incorporated to facilitate purchase of valves, fittings, etc.
Additional Expenses = 0.15×261,148.76 = $39,172.34
Hence,
Total Construction Cost
= 11,108.12 + 1,101.60 + 650,000 + 4,939.04 + 244,000 + 39, 172.34
= $950,321.1
b. Operation and Maintenance Charges:
Labour Charges:
A labour charge of $20/hr is taken to facilitate maintenance as used by Friedler and
Hadari (2006).
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Identification of Sustainable Alternative Applicable to North Engineering Toilets
Annual Labour charge = 20 ×52 = $1,040
Power Consumption by Living machines:
The energy consumed for running a living machine is 0.5 kWh/1000 gal/day.
Hence the average daily energy consumption for living machine = 0.5 kWh/1000 gal/day
× 12,000 gal/day = 6 kWh.
At 5.6 cents per kWh, Annual cost to treat 12,000 GPD = 6 ×5.6 × 365/100
= $122.64
Power Consumption by Pump:
Assuming a pump that uses 2hp, 100gpm
Time required to transfer 7800 gallons = 7800/100 = 78 min = 1.3hr
Power used = 1.3 × (2 × 76) × 5.6 ×365/100 = $4,038.94
Spare parts and Repairs:
These are calculated using 2%of total investment excluding living machine and
additional expenses = 0.02×261,148.76 = $5,222.98
Page 41 of 47
Identification of Sustainable Alternative Applicable to North Engineering Toilets
Composting Toilets Design Calculations and Cost Estimations
Calculation of Water Consumption After Replacements:
Waterless toilet: No water is needed for flushing.
Foam flushing toilet: 3 oz. of clean water each flush
Moistening system: 3 gallons clean water per day
Total water consumption: 3 × 20 +3 × 30 × 77.28 × 0.0078= 114.25 gallon/ day
Yearly water consumption of toilets is 41,702 gallons. Adding water used for sinks,
yearly water consumption is: 41702 + 2223 × 365 = 853,097 gallons at the cost of $4,265.
That is 72.3% reduction compared with $15,397 cost for 2,849,040 gallons of water for
the existing toilet system.
Calculation of Energy Consumption After Replacements:
Ventilation: 93 W
Automatic moistening system: 10 W (spray time is preset, and approximately half time
working)
Liquid removal pump: 575 W
Total energy consumption of the composting toilet system in NE: 13,460 W
Yearly energy consumption is 13460 × 10-3 × 24 × 365 = 17,909.6 kWh
According to Average Retail Price of Electricity to Ultimate Customers by End-Use
Sector from energy information administration of official energy statistics from the US
government, the retail electricity price in Toledo is 5.6 cents per kWh. Yearly electricity
cost of the proposed system is $1,003.
Cost of Clivus Multrum M18:
Considering the cost per set to be at $ 4,995, cost for 20 sets = $ 4,995 × 20 = $99,900
Page 42 of 47
Identification of Sustainable Alternative Applicable to North Engineering Toilets
Cost of Pipeline
diameter material
air ventilation duct
drain line from foam flushing
toilet to composting tank
Length
Price
per Total
(ft)
unit ($)
($)
4’’
PVC
720
5.50
3960
4’’
PVC
240
5.50
1320
Total = $5,280
The total cost for construction is $105,180. The yearly operation cost of composting toilet
system is $2,024.
Page 43 of 47
Identification of Sustainable Alternative Applicable to North Engineering Toilets
Appendix B
EIOLCA Results
Page 44 of 47
Identification of Sustainable Alternative Applicable to North Engineering Toilets
LCA - Using EIOLCA Website
Water Use Consumption
Conventional Air Pollutants
Pre - Design RW &
GW
Post - Design
Composting
Water
Consumptio
n Cost
$
SO2
mt
CO
mt
Nox
mt
VOC
mt
LEAD
mt
PM
10
mt
$51,600.00
$11,072
$6,403
0.034
0.003
0.002
0.116
0.01
0.008
0.034
0.01
0.008
0.023
0.003
0.002
0
0.002
0.001
0.008
0
0
CH4
MTCO2
E
N20
MTCO2
E
CFC
MTCO2
E
1.74
3.74
0.146
0.235
0.035
0.02
0.237
0.07
0.02
Green House Gases
Water
Consumptio
n Cost
GWP
CO2
MTCO2 MTCO2
$
E
E
Pre - Design RW &
GW
Post - Design
Composting
Rainwater
Harvesting
Greywater
Recycling
Compostin
g
$51,600.00
$11,072
$6,403
14.8
6.2
1.24
Conventional Air Pollutants
Manufactur
ing/Const.
Cost
SO2
CO
Nox
$
mt
mt
mt
$262,800.0 0.34 0.57 0.27
0
6
1
5
0.99
$950,321
1.25 2.06
5
0.12 0.47 0.11
$95,190
2
6
4
Green House Gases
Manufactur
ing/Const.
GW
Cost
P
CO2
CH4
12.5
4.4
1.05
VOC
mt
0.99
6
LEA
D
mt
0
3.6
0.10
9
0
N20
CFC
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0
PM
10
mt
0.0
34
0.1
22
0.0
24
Identification of Sustainable Alternative Applicable to North Engineering Toilets
Rainwater
Harvesting
Greywater
Recycling
Compostin
g
$
$262,800.0
0
$950,321
$95,190
MTC
O2E
206
0
743
0
58.5
6
MTC
O2E
186
671
48.5
9
MTC
O2E
123
0
443
0
5.90
6
MTC
O2E
MTC
O2E
642
232
0
2.55
3
1.8
6.51
1.49
3
Energy
Manufactur
ing/Const.
Cost
Tota
l
LPG
DISTI
LATE
KE
RO
TJ
0.1
07
TJ
0.74
7
TJ
Rainwater
Harvesting
$
$262,800.0
0
2.98
elec
Mk
Wh
0.12
6
Greywater
Recycling
$950,321
10.8
0.45
7
2.02
4.41
0.47
8
0.3
88
2.7
0
Compostin
g
$95,190
0.76
7
0.03
7
0.17
8
0.37
2
0.04
3
0.0
33
0.06
1
0
Rainwater
Harvesting
Greywater
Recycling
Composting
TJ
coal
natu
ral
gas
M
OT
O
GA
S
TJ
0.55
9
TJ
1.22
TJ
0.13
2
Conventional Air Pollutants
Opera
tion &
Maint.
Cost
SO2
CO
Nox VOC
$
mt
mt
mt
mt
$922. 0.00 0.00 0.00 0.00
34
1
2
1
3
$10,5 0.01 0.02 0.01
06.00
4
3
1
0.04
$10,6 0.56 0.05
0.00
71
9
8
0.27
9
Green House Gases
Opera
tion &
Maint.
Cost
GWP CO2 CH4
N20
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LEAD
mt
0
0
0
CFC
PM
10
mt
0
0.0
01
0.0
14
0
JE
T
FU
EL
TJ
0.
04
0.
14
4
0.
01
6
RESI
DUA
L
TJ
0.03
3
0.11
9
0.02
2
Identification of Sustainable Alternative Applicable to North Engineering Toilets
$
$922.
34
$10,5
06.00
$10,6
71
Rainwater
Harvesting
Greywater
Recycling
Composting
MTC
O2E
MTC
O2E
MTC
O2E
7.21
MTC
O2E
0.65
1
4.3
2.25
82.2
7.42
49
110
105
3.95
25.7
0.05
3
MTC
O2E
0.00
6
0.07
2
1.29
Energy
Opera
tion &
Maint.
Cost
Rainwater
Harvesting
Greywater
Recycling
Composting
$
$922.
34
$10,5
06.00
$10,6
71
Total
TJ
0.01
0.11
9
1.27
elec
Mk
Wh
0
0.00
5
0.00
2
natu
ral
gas
coal
TJ
0.00
2
0.02
2
TJ
0.00
4
0.04
9
0.23
7
0.98
LPG
MO
TO
GA
S
DISTI
LATE
KE
RO
JET
FU
EL
RESID
UAL
TJ
TJ
TJ
TJ
TJ
TJ
0
0.00
5
0.00
2
0
0.0
04
0.0
02
0.003
0
0
0.03
0
0.01
0
0
0.0
02
0.0
01
0.001
0.039
Table for Figure 5.1.1
Rainwater Harvesting
Construction Costs ($)
Greywater Recycling
Composting Toilets
262800
950321.1
105180
Construction GHG (MTCO2E)
2060
7200
823
O&M (MTCO2E)
7.21
82.2
41.2
922.34
10506.92
5268
O&M Costs ($)
Table for Figure 5.1.2
Rainwater Harvesting
Greywater Recycling
Composting Toilets
Construction
262800
950321.1
105180
Construction
2.98
10.8
1.19
O&M
0.011
0.119
0.06
O&M
922.34
10506.92
5268
$
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