Case Study: Water and Wastewater Design for Mer Island

This report presents a conceptual proposal for the sustainable design of water and wastewater infrastructure for a household on Mer Island, a Torres Strait township. The design addresses the increasing water shortage and the need for alternative water sources. The report covers key areas including water supply options (existing supply, roof water, and combinations), wastewater management (on-site systems, decentralized approaches, and reticulated sewerage), and water reuse strategies. The report also considers rainwater harvesting, greywater recycling, and conservative water treatment methodologies, taking into account the island's rainfall patterns and the existing municipal water supply system. The design incorporates considerations for housing requirements, bathroom design, kitchen design, and toilet design, aiming to minimize water consumption and maximize efficiency. The report also includes analysis of the municipal water supply system, housing requirements, and calculations for water demand in different areas of the house. The aim is to develop a sustainable water management plan that is suitable for the specific conditions of Mer Island, particularly in light of the asbestos house case study provided.

Name of student:
Institutional Affiliations:
Name of course:

Table of Contents
Introduction and Project requirements.........................................................................................................3
Rainfall harvesting......................................................................................................................................4
The municipal water supply system.............................................................................................................6
Housing requirements..................................................................................................................................7
The bathroom design...............................................................................................................................7
The kitchen..............................................................................................................................................9
The toilet design....................................................................................................................................10
Treatment of the wastewater......................................................................................................................12
Conclusion.................................................................................................................................................15
Bibliography..............................................................................................................................................17

Introduction and Project requirements
It has been indicated that there is an increasing shortage of water from the municipal distributor
which necessitates the use of alternative sources of water for both potable and non potable usage.
In line with this, it has been indicates that the changes in season results to a fluctuation in the
amount of water in the reservoirs. When summer and the dry season approaches, residents of
Queensland tend to increase the amount of water consumed. In the year 2017, there was need to
supply each resident with an extra 30 liters on a daily basis. This, as such, meant that the
municipal and the state needed to introduce a rationing strategy limiting the per person daily
water use to 150 liters. South-Queensland water use on a daily basis increased by 29 liters while
use in the sunshine coast increased by 71 liters (Moore, 2017).
However, this design is based on the 70% decrease in water levels that necessitate rationing. This
has been defined as the drought awareness strategy (Moore, 2017). In essence, one of the ways in
which water use may be mitigated is through rainfall water harvesting, with the dry months taken
into consideration. The other design strategy would be to ensure that the sink, bathroom and
toilet conserve as much water as possible. This may mean recycling the greywater. Also involved
in this design will be the design of a conservative water treatment methodology.

Rainfall harvesting
As has been indicated, the building is made of asbestos material. This indicates that there is
likely to be very minimal changes in the indoor building temperatures with the change in
external temperatures. Nevertheless, to fully implement a sustainable water use platform, one of
the most important considerations is the monthly rainfall experienced (Helmreich & Horn)
around the island. However, there may be three approaches to measuring the rainfall received in
a specific location: reliability, vulnerability and resilience (Allon & Sofoulis, 2006). This is
important for any building activities and can be used to supplement the water received from the
municipal system
The Australian drinking water standard has specified that there needs to be proper emphasis on
the physical, chemical and microbial quality of the water prior to the actual use (National health
and Medical Research Institute, 2011). However, when it comes to rainfall water, the most
discernible characteristic would be the physical characteristic. This means that the catchment
area has to be properly inspected. In essence, the major advantage would be the readily available,
depending on the storage capabilities. However, it may difficult to obtain water from the rooftop
watershed during the dry season.
To estimate the total rooftop area, one important assumption is on the total size of the roof. It
may be assumed that the roof measures 40m by 50 meters. This translates to a total roof area of
200 square meters. This forms the catchment of the analysis. The other assumption is on the type
of material that may be used to cover the roof. Seeing that the building is made up of asbestos,
the material used in roof design may be an asbestos sheet. The runoff coefficient, in this case, is
0.80 (Zende, 2015).

A single person has been estimated to consume about 0.30 cubic meters daily. This, as such,
means that the total amount of water used by the four individuals daily is 1.2 cubic meters. It can
be estimated that this is the same amount that may be used for domestic purposes such as
cooking. Finally, it may be assumed that water used for contingencies can amount to 5 cubic
meters
Therefore, the total amount of water consumed daily is 7.2 cubic meters. Approximate monthly
use is about 216 cubic meters. From the calculations, it can be seen that a tank whose capacity is
about 345.6 cubic meters will be sufficient for the storage of water to be used every month.
However, seeing that other months endure a shortage of water, the supplement of the municipal
water facility may be of immense importance.
According to statistics, the average rainfall received in the island every month is as indicated
below (Meat and Livestock Australia):
Analyzing the rainfall received beginning with the least amount; the table can be calculated as
follows:
Month Average rainfall(mm) Rainfall received
August 31 31*30*0.8*200=148.8
cubic meter
September 31 148.8 cubic meters
October 31 148.8 cubic meters
November 72 345.6 cubic meters
December 192 952.32 cubic meters
January 313 1502.4 cubic meters

February 312 1547.52 cubic meters
March 314 1557.44
April 196 972.16
May 72 345.6 cubic meters
June 33 158.81
July 32 158.72
However, it is important to ensure safety when it comes to the first flushes of rainfall. This may
mean disposal of the first 20-25 L after the first flush of rainfall. During high rainfall periods, it
may be important to ensure that only rainwater is used but when it comes to the dry season, the
municipal water should be used. This is a conservative strategy.
The municipal water supply system
According to the regional council, it is Important to ensure that each person receives adequate
amounts of water. Nevertheless, the agency ensures that society has adequate amounts of water
for both domestic and industrial purposes through the following provisions:
 Saltwater intake points and six desalination facilities.
 Fifteen lagoons for water catchment.
 A distribution network that has an average length of 88km
 Water treatment plants are about 15 in number.
In this design framework, the major assumption is that the municipal council is the sole supplier
of water to the household. It does not take into consideration the storage and supply of water
from the reservoir and the roof catchment area.

Nevertheless, according to the meter reading, water consumption in a house of 4 people may be
at an average of 57.67 cubic meters. This encompasses all domestic usage such as cooking,
cleaning, laundry and bathing, to mention a few.
Housing requirements
Research has indicated that the fulltime equivalent is essential in determining the amount of
water that is in demand on an average day.
Therefore, the FTE = (number of occupants* the times in which they are available in the house)/
Average hours of occupancy.
In this case, the average hours of occupancy have been indicated as 8.
Therefore, to determine the baseline demand for water in all the housing appliances, The FTE
can be estimated as:
(4* 10 hours)/8= 5
Therefore, 5 is the number of hours taken as the baseline for calculating the water demand for
sinks, toilets, showers, and the urinal among the other housing appliances.
The bathroom design
The model that may be used in the design is as follows:
The water into the bathroom- the water out of the bathroom=0 (Matos, Teixeira, Duarte, &
Bentes, 2013)
Therefore:

Water into the bathroom-grey water- bathroom water flowing into the sewer=0
That being stated, the baseline demand will be important for the overall design of the water
supply system
The baseline water flowing into the bathroom sinks is indicated by the following;
The number of bathroom sinks* The FTE* baseline flow of water into each of the bathroom
sinks* the time for flow out of each bathroom application
In this case, the number of bathroom sinks can be assumed as 3
The FTE has been estimated at 5
The time of flow out of each bathroom sink can be estimated as 30 seconds
And the rate of water flow for bathroom sinks has been estimated to be between 0.5 gallons per
minute and 1.5 gallons per minute
Therefore, the baseline flow demand for the bathroom sinks in the house can be estimated as:
3*1.5*5*5= 112. 5 gallons. This is an approximate value for the daily water demand by the
bathroom sinks
Therefore, the daily water demand from the bathroom sinks is 0.45 cubic meters.
The monthly water demand for the bathroom sinks can be estimated as 13.5 cubic meters
The annual demand for the bathroom sinks is estimated as 162 cubic meters
The kitchen
The stock principles from the bathroom sinks are the same principles that may be used in the

The baseline demand for the sink is calculated using the same principles as the baseline demand
for the bathroom.
The water into the bathroom- the water out of the bathroom=0
Therefore:
Water into the bathroom-grey water- bathroom water flowing into the sewer=0
That being stated, the baseline demand will be important for the overall design of the water
supply system
The baseline water flowing into the bathroom sinks is indicated by the following;
The number of kitchen sinks* The FTE* baseline flow of water into each of the sinks* the time
for flow out of each bathroom application
In this case, the number of kitchen sinks can be assumed as 2
The FTE has been estimated at 5
It has been estimated that the flow rate of the kitchen sinks is approximately 2.2 gallons per
minute.
Nevertheless, it should be assumed that the time that is usually spent in using the kitchen sink is
about 6 minutes. This means that the baseline water demand for the kitchen sinks is as follows:
6*2*5*2.2= 132 gallons per day
Therefore, the total amount of water that is used in the kitchen sinks every month may be
estimated at 14.99 cubic meters. To ensure that this water is used most efficiently, the discharge

point should be directly connected to the water treatment facility. This may either be the
municipal water treatment or a wetland system.
The toilet design
With the high water demand for toilets, it may become impossible to ensure that a building is in
line with the LEED requirements (Joustra, 2010) if a proper strategy is not developed. However,
it is also important to consider that water for flushing does not necessarily have to be of high
quality (Shamabadi, Bakhtiari, Kochakian, & Farahani, 2015)
Nevertheless, in this design, the water stock may be estimated as ni (Srinivasan, Stankovic, &
Whitehouse, 2011)l, meaning that water that enters the toilet is flushed before the accumulation
of water.
This translated that the water intake should be equal to the water outflow.
The various water input processes are detailed as follows:
The inflow of potable water into the system
The flow of treated sink water into the toilet
The flow of reclaimed and recycled water into the toilet
The flow of rainwater into the toilet
On the other hand, the outflow mechanisms include:
Sewer water that flows from the toiled
Backwater that flows into the treatment channel and the treatment facility

QDsgn T = FTE × NA T × VA T(Dsgn)
QDsgn T refers to the water required for the case design of the toilet
NA T refer to the actual number of toilet applications in the building
VAT refers to the actual flow rate of the water in the toilet appliance
In this case, the design does not consider the use of supplementary water flows into the toilet
appliance
As such, the design can estimate the total amount of water required for the total number of toilet
appliances in the building. As an estimate, the building may have four toilet appliances.
Moreover, the design may be based on the assumption that a single flush has 6 litres (McGee,
2018)
Therefore, the total amount of water that is flushed daily is about:
5*6*4=120 litres
This translated to 3.6 cubic meters every month and annual flush water of 43.2 cubic meters.
However, the uses of recycled water may improve the water footprint of the building.
In essence, it can be indicated that ensuring that the three building water use is kept in check
will be essential in ensuring that that building has a lower water footprint. The use of recycled
water may be more important when it comes to toilet use as compared to the other building uses.

Treatment of the wastewater
The first wetland system that nay is used to treat the wastewater is known as the free water
surface wetland system. In line with this, the design needs to consider the availability of a free
channel for the flow of water. This channel has to be impervious so that the water may not seep
into the ground (Budds, 2016). Seeing that the design is suitable for areas with clay, it may not
be important in this design. Secondly, there is the subsurface flow system. It is considerably
different from the free water flow because the water flows under the substrate material. The
substrate material may be in terms of boulder or gravel. That stated it might be the one for use
because it prevents nuisance such as mosquitoes and other pests. Nevertheless, the strategy used
for water disposal and reuse should be well in line with the Queensland water management
guidelines that have been indicated below:

(Power, 2010)
In line with this, the total amount of water to be treated can be estimated as :
Water from the sinks: 0.5 cubic meters

Water from the bathroom: 0.45 cubic meters
Water from the toilet: 0.12 cubic meters
A conservative approach is to separate the grey water and black water. This is mainly because
the greywater can be conserved and recycled for other purposes.
Parts of the Wetland system
 The liner
 The porous media
 The under drain
 and the vegetation
To estimate the area for treatment, the following formula may be used:
Area= The flow of the influent (cubic meters/day) * ln (concentration at the inlet/Concentration
at the outlet)/ KTdnv (Farooqi, Basheer, & Chaudhari, 2007)
Therefore, to fully develop a feasible wetland system, it is important to understand the various
characteristics of the effluent. The concentration of the building effluent is important in the
overall design criteria (Al-Jayyousi, 2003). This is because it determines the types of plants that
will be used in the removal of the loads. Moreover, this determines the total land area and the
types of materials to be used. Therefore, prior to the actual development of the water
management and waste disposal methodology, all the stakeholders should be involved.
Recycling and reuse of water should be managed through the management flowchart.

(Quensland Government EPA, 2005)
Conclusion
Therefore, the design of the building will need to take into consideration the total number of
occupants and the daily discharge of wastewater from the building, The FTE value, nevertheless,
is important when it comes to an understanding the baseline water use for a specific home

appliance. The sink, the bathroom and the toilet are the most important appliances when it comes
to the design of the water drainage and supply system. The use of rainwater harvesting will also
improve the water conservation of the building. The water may be used for non-potable as well
as potable use. Moreover, the use of greywater from the sinks will also reduce the water
footprint. When it comes to treatment, it may be important to consider environmental friendly
means such as the use of a wetland system.

Bibliography
Al-Jayyousi, O. R. (2003). Greywater reuse: towards sustainable water management.
Desalination .
Allon, F., & Sofoulis, Z. (2006). Everyday water: cultures in transition. Australian Geographer, .
Budds, D. (2016, 04 22). 5 Clever Architectural Strategies For Conserving Water. Retrieved
from https://www.fastcompany.com/3059199/5-clever-architectural-strategies-for-water-
conservation
Farooqi, H., Basheer, F., & Chaudhari, R. J. (2007). Constructed Wetland System (CWS) for
Wastewater Treatment. The 12th World Lake Conference.
Helmreich, B., & Horn, H. (n.d.). Opportunities in rainwater harvesting. Desalination .
Joustra, C. (2010). An Integrated Building Water Management Model for Green building.
Matos, C., Teixeira, C. A., Duarte, A., & Bentes, I. (2013). Domestic water uses:
Characterization of daily cycles in the north region of Portugal. Science of the total environment .
McGee, K. (2018, April 17). Faucet Flow Rates. Retrieved from
https://www.hunker.com/13415104/the-average-sink-faucet-gallons-of-water-per-minute
Meat and Livestock Australia. (n.d.). rainfall history. Retrieved from
https://weather.mla.com.au/climate-history/qld/murray-island
Moore, T. (2017, September 04). Retrieved from
https://www.brisbanetimes.com.au/national/queensland/water-restrictions-closer-as-southeast-
queensland-water-use-skyrockets-20170904-p4yvq1.html
National health and Medical Research Institute. (2011). Australian Drinking Water Guidelines 6.
Power, k. (2010). Recycled water use inAustralia: regulations,guidelines and validation
requirements for a national approach.
Quensland Government EPA. (2005). Queensland Water Recycling Guidelines.

Shamabadi, N., Bakhtiari, H., Kochakian, N., & Farahani, M. (2015). The investigation and
designing of an onsite grey water treatment systems at Hazrat-e-Masoumeh University, Qom,
IRAN. Energy Procedia .
Srinivasan, V., Stankovic, J., & Whitehouse, K. (2011). Watersense: Water flow disaggregation
using motion sensors. Systems for Energy-Efficiency .
Zende, A. (2015). Rooftop rainwater harvesting system - a model based approach. National
Conference on, Modeling, Optimization and Control.