Identification of the Most Sustainable Alternative System for
NE Toilets at UT: A comparative Study of Implementation of
Rainwater Harvesting, Greywater Recycling, and
Composting Toilets
CIVE 6900 Sustainability Science
and Engineering
Fall 2008
Professor: Dr. Apul
Presenters: Akhil Kadiyala, Zheng
Xue, Andrew E. Wright
Objectives
1.
Application of ‘EIOLCA’.
2.
Indicator Analysis – Environmental Indicator.
– Natural Resource Consumption Indicator.
– Economic Indicator.
3.
Sustainability Index and Performance.
4.
Possibility of obtaining LEED Credits.
Data Collection
• Floor plans, plumbing diagrams, and number of toilets –
Maintenance Department.
• Utility water usage (gal/flush) obtained from online
websites based on manufacturing company.
• NE water bill - $4277.00 for 1048 ccf (783,904 gallons).
• Materials required, quantities, and costs requires for LCA
are obtained from online web search and open literature.
Data Collection
Room No
Type of Utility
No. of facilities in
the room
Company /
Manufacturer
Flow rate
1262
Faucets
Urinals
Toilets
3
2
3
Crane Plumbing
Zurn
Zurn
NA
3.0 g/f
1.6 g/f
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
Current Water Usage in Restrooms
• Assumptions
 No. of people = 2370
 Usage of restroom = 1.5
times/day.
 75% Male and 25% Female
• 30% of total water
consumption is used by
toilets.
Rainwater Harvesting
•
Design Criteria:
 Roof rainwater collected at a
general point and sent to a tank.
 Filtered via ground filter.
 The rainwater is then pumped to
a header tank .
 Disinfection with UV.
 Rainwater is distributed to the WCs
via the header tank which
incorporates the main water back
up, riser connection and overflow.
Components and Cost Estimates for
Rainwater Harvesting
Rainwater Harvesting Estimate
Quantity
Holding Tanks
2
Unit
ea
$
$113,783.00
Total
$227,566.00
Pipe from downspouts
to holding tank
300
lf
$14.50
$4,350.00
Pump-2 hp, 100 gpm
Self Cleaning Tank
inlet Filter
1
ea
$965.00
$965.00
2
ea
$750.00
$1,500.00
Floating tank filter
6000 Gallon Header
tank
2
ea
$220.00
$440.00
1
ea
$4,611.17
$4,611.17
50
lf
$11.50
$575.00
700
lf
$32.50
$22,750.00
$262,757.17
2" pipe from holding
tank to header tank
4" pipe back to toilets
piping
Activity
Labor Charges
Power Consumption by Pumps
Spare parts and Repairs
Total O&M Charges
Cost
$80
$42.34
$800
$922.34
Greywater Recycling
• Components :
1.
Greywater Source
2.
Collection through
plumbing
3.
Treatment System
4. Storage
5.
Greywater Reuse
Greywater Loading Rates
• Hydraulic Loading Rates
 0.25-1 gal/sq .ft /day – Fine media
 3-10 gal/sq .ft/day – Recirculation
• Organic Loading Rates
 0.00025lbs BOD5/ft2/day to
0.0012 lbs BOD5/ft2/day - Fine
media
Components and Cost Estimates for
Greywater Recycling
Components
Cost
Piping
$1,101.60
Equalization Tank
$11,108.12
Living Machine
$650,000
Disinfection System
$244,000
Pumps
$965
Storage Tanks
$ 4,939.04
Additional Charges
$39,172.34
Total Construction Charges
$950,321.10
Activity
Labor Charges
Power Consumption by Living Machines
Power Consumption by pump to lift water to storage tank
Spare parts and Repairs
Cost
$1,040
$205
$4038.94
$5,222.98
Total O&M Charges
$10,506.92
Composting Toilets
• Waterless or consume a
minimum amount of
flushing water.
• Human waste is converted
into an organic compost and
usable soil.
Composting Toilet Replacements
and Estimates
Room
1262
1260
Type of toilet
Foam
flushing
Foam
flushing
Number of
toilets
Number of
composting
tank(s)
3
1
3
1
1014
Waterless
2013
Foam
flushing
5
1015
Waterless
3
2014
Foam
flushing
3
1057
Waterless
3
2053
Foam
flushing
3
1058
Waterless
5
2056
Foam
flushing
• Total Cost of
Construction =
$105,180
5
5
3
3
5
5
• Total Cost for O&M =
$5268
Water Consumption and Effluent
Quantity
Life Cycle System Boundary
• Functional Unit: savings per life cycle of
each system ($/life cycle).
LCA Results
Greenhouse gases for “Construction”
and “O&M” Stages of a Life Cycle
Energy for “Construction” and
“O&M” Stages of a Life Cycle
Environmental Indicator
• The need for potable water use for toilet
flushing：
• Cost for rainwater harvesting and grey water
recycling with 811,950 gallons per year $4,348.
• For composting toilets, it would be 853,370
gallons with a cost of $4,608.
Environmental Indicator
Conventional Air Pollutants
Water Consumption Cost/year
$
SO2
mt
CO
mt
Nox
mt
VOC
mt
LEAD
mt
PM 10
Mt
Pre - Design RW & GW
$15,480
0.020
0.034
0.016
0.059
0
0.002
Post - Design
$4,348
0.006
0.009
0.005
0.017
0
0
Composting
$4,608
0.006
0.010
0.005
0.018
0
0
Water Consumption Cost
GWP
CO2
CH4
N20
CFC
$
MTCO2E
MTCO
2E
MTCO
2E
MTCO
2E
MTCO
2E
Pre - Design RW & GW
$15,480
121
10.9
72.2
37.8
0.106
Post - Design
$4,348
34
3.07
20.3
10.6
0.030
Composting
$4,608
36
3.25
21.5
11.3
0.032
Green House Gases
Natural Resource Consumption Indicator
• Overall % Water
Consumption Reduction
 Rainwater Harvesting: 21.77%
 Greywater Recycling: 45.92%
 Composting Toilets: 21.72%
Economic Indicator
Economical Choice Comparison based
on Cost of Construction and O&M
Economical Choice Comparison based
on Cost/gal of water saved/day
Payback Period
Rainwater Harvesting: 23.42 yrs
Greywater Recycling: 40.18 yrs
Composting Toilets: 9.5 yrs
Sustainability Index and Performance
Percentage
Performance = Maximum Score of indicator × ∑Sustainable Score.
Points Allotted
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
2+2+2 = 6
1+3+1 = 5
3+1+3 = 7
66.67%
55.55%
77.78%
12
15
21
S.No
Points of Comparison
Sustainable Score
Achieved
Sustainability Index
Performance
Applicable LEED Credits
 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.
Conclusions
 Composting Toilets - Most Sustainable Alternative System.
 Greywater Recycling is recommended for long term use –
Ability to conserve large amounts of water, thereby reducing
potable water demand.
 Rain water harvesting can also be used similarly but the source
of supply to this system is dependent on rainfall and seasons.
Limitations and Scope for Future Work
• Limitations:
 Difference in persons perspective.
 Complete life cycle not taken into account.
 Applicability to only toilet flushing is considered.
 Scope for Future Work:
 Study the combination of alternative systems studied individually
in this study.
Questions?