Sustainable water management strategies A possible future tool for decreasing the water end-use energy
Totoianu Alexandra Aarhus, Denmark 27th of March 2015
Bachelor of Architectural Technology and Construction Management
Sustainable water management strategies A possible tool for decreasing the water-end energy
Alexandra Totoianu 27th of March 2015
Type of assignment: 7th Semester Dissertation
Title: Sustainable water management strategies Subtitle: A possible tool for decreasing the water end-use energy
Education: Architectural Technology and Construction Management programme
Institution:VIA University College
Author: Totoianu Alexandra
Consultant: Mihoko Brethvad
Date: 27th of March 2015
No of pages: 43
All rights reserved: No part of this dissertation may be reproduced without the prior permission of the author
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Sustainable water management strategies A possible tool for decreasing the water-end energy
Alexandra Totoianu 27th of March 2015
Preface This dissertation is made as part of the Bachelor of Architectural Technology and Construction Management Programme named: “Sustainable water management strategies. A Possible tool for decreasing the water end-use energy”
Acknowledgements I would like to thank to my consultant, Mihoko, without whom this paper wouldn’t have been possible through her guidance and patience for making this paper possible.
Abstract This paper analyses the methods we can use to decrease the water end-use energy using as a tool the sustainable water management in a building’s water usage. With a deep consideration of the water scarcity at a global level and on the embedded energy in terms of water use in a building, there will be presented the technological methods for water purification and conservation. The essence of the paper is to grasp the principles of the living roofs as a powerful tool for mitigating the storm water runoff and to understand how we can conserve the potable water by separating the grey water from the black one and by harvesting the water from the rooftops. These methods will be sustained ultimately by solid study cases which have measured their efficiency through the building’s behavior during the years. An important tool for fully grasping and ultimately applying the methods is the deep understanding of the principles the ecosystem works on and the water’s cycle in order to respond harmoniously and to adapt to the water scarcity for to apprehending how does the building relate to its context.
Keywords: water end-use energy, sustainable water management, water scarcity, water conservation, water purification, storm water management, water footprint, water cycle, living roofs, black water, grey water
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Sustainable water management strategies A possible tool for decreasing the water-end energy
Alexandra Totoianu 27th of March 2015
Contents 1. Introduction ............................................................................................6 1.1 Background information and presentation of the subject involved ....................... 6 1.2 Reason for choice and relevance for the future profession .................................7 3. Problem Statement .................................................................................8 1.4 Delimitation ........................................................................................8 1.5 Choice of theoretical basis and sources of empirical data ..................................9 1.6 Choice of research methodology and empirical data ........................................9 1.7 The report’s overall structure and argumentation ..........................................10 2. Actual situation – The importance of water ..................................................... 10 2.1 Water scarcity ....................................................................................10 2.2 The “embodied energy” - energy intensity of water use .................................11 2.2.1 Raw water source extraction .............................................................12 2.2.2 Water treatment ............................................................................ 12 2.2.3 Water distribution to the point of use ..................................................13 2.2.4 Wastewater treatment ....................................................................13 2.2.5 Water end-use energy .....................................................................14 2.3 The “water footprint” assessment ............................................................15 3. Water purification and recycling ..................................................................16 3.1 Gray water recycling ............................................................................ 16 3.2 Black water recycle.............................................................................. 17 4. Water conservation through storm water management .......................................19 4.1 Rain water harvesting .........................................................................21 4.1.1 The catchment area .......................................................................22 4.1.2 Collection devices .........................................................................22 4.1.3 Conveyance systems .......................................................................23 4. Living roofs as a tool for storm water runoff .................................................... 24 5.1Design principles ..................................................................................25 5.1.1 Extensive roof ..................................................................................28 5.1.2 Intensive roof ..................................................................................28 6. Case studies ...........................................................................................29 6.1 Case study no. 1-Water re-cycle and rainwater harvest-Music and Science Building, Hood River, Oregon USA.............................................................................. 29 4
Sustainable water management strategies A possible tool for decreasing the water-end energy
Alexandra Totoianu 27th of March 2015
6.1.1 Black water and grey water ...............................................................30 6.1.2 Rain water technology philosophy ....................................................... 31 6.1.3 Water conservation facts ..................................................................32 6.2 Case study no.2- Living roof typology - California Academy of Sciences (CAS), by Renzo Piano ............................................................................................33 6.2.1 Bio Trays innovation ........................................................................34 6.2.3 The living’s roof layers .....................................................................34 6.2.3 Vegetation design ...........................................................................35 6.2.4 Storm water runoff .........................................................................36 Bibliography ..............................................................................................39
List of Figures Figure 1: Components of the embodied energy in the water’s cycle ( (Sharon deMonsabert and Ali Bakhshi, 2009)............................................................................................................................................................. 11 Figure 2: Water end use in a residential building (Anon., 1999) ......................................................................14 Figure 3: Water use classification in buildings systems (Simonen, 2014) ....................................................... 15 Figure 4: The “Agus” system re-using the sink gray water for toilet flushing (Lepisto, 2006) ..................16 Figure 5: Black water treatment and re-use for irrigation and cooling towers (Aquacell, n.d.) ...............18 Figure 6: A typical rain water collecting system and its components (Center, n.d.) ...................................21 Figure 7: The rainwater collecting system (Austin, 2009) .................................................................................22 Figure 8: A typical conveyance system (UNEP, n.d.) ...........................................................................................23 Figure 9: An example of a green roof in Ha Long Bay,Vietnam (Inhabitat, 2012) ........................................25 Figure 10: The layers of a typical green roof and its drainage system (Goodwin, 2011)............................ 26 Figure 11: The physical process which contributes to the water runoff (Anon., n.d.) ................................27 Figure 12: The green roof of California Academy of Sciences by Renzo Piano (Sciences, n.d.)................ 31 Figure 13: Roof detail showing the water's journey to the drainage ( (Palmer, 2011) ...............................33 Figure 14: Hood River Middle School Music and Science Building (Architecture, n.d.) .............................36 Figure 15: The water cycle diagram in the building's usage (Architecture, n.d.) ..........................................37 Figure 16: Building section showing the rainwater strategy (Chris Brown, 2013) ...................................... 38 Figure 17: Annual potable Water Use Reduction................................................................................................ 39
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Sustainable water management strategies A possible tool for decreasing the water-end energy
Alexandra Totoianu 27th of March 2015
1. Introduction 1.1 Background information and presentation of the subject involved The paper is part of the 7th semester of the “Architectural Technology and Construction Management” programme. It analyzes the techniques we could reduce the energy in a building’s usage through the strategic implementation of the water usage by stressing the potable water availability and the ways we could reduce its consumption in a building. The so-called “water footprint” will be my guidance tool for apprehending the water usage divisions in our buildings and for tackling the methods we can apply for creating a sustainable water cycle within our buildings just as in an ecosystem without contaminating the environment. There will be presented the methods through which we can conserve water through recycling the gray and black water, harvesting it from our roofs, mitigating the storm water runoff using the green roofs. For grasping the prerequisite of the sustainable water reuse systems within a building coping together as in an ecosystem, I will be analyzing the Music and Science Building by Opsis Architects. The green roofs’ potential will be discovered through the analysis of the storm water efficiency and innovation of the California Academy of Science by Renzo Piano. The main aim of this paper is to encourage the sustainable water management within our buildings through becoming aware of the energy the water needs in its cycle within our household for potable and non-potable uses (the so-called “embedded energy” concept). The presented solutions should be our response to the water scarcity and a possible solution which we could opt for adapting to the inefficiency of the water treatment’s energy. Through these water conservation strategies, this paper should reveal that we can significantly reduce the energy in our water end-use and the energy needed for treating the waste water. It should also raise awareness in each of the readers’ minds, for being able to grasp alternative solutions for diminishing the water scarcity, ameliorate the energy through understanding better the principles on which nature works for having a high adaptability to the constant changes around us and for preserving the water. We should be able, in the end, to fully grasp the information, the gravity of the problem and to act as soon as possible always having in mind the fact that water is scarce and it is our most sacred resource.
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Sustainable water management strategies A possible tool for decreasing the water-end energy
Alexandra Totoianu 27th of March 2015
1.2 Reason for choice and relevance for the future profession First of all, I think sustainability is our future. Even though the term itself has become very popular in the last couple of years, it is still quite abstract, in my opinion, having more possibilities to be approached. Due to this fact, most of us are not entirely aware of its importance and potential and on how to approach it. One way to approach it would be to in terms of water provision systems, not in terms of materials. So, instead of addressing the term “sustainability” only from its building envelope point of view, we shall try to dissect the building as a “living organism” whose technological elements should work in a perfect harmony for consuming as less energy as possible and for harnessing the environment as least as possible. In this manner, I consider trying to catch a glimpse of the buildings not only from the exterior, but to see beyond that, in their concealed interior. Therefore, what makes a building truly “sustainable”, in my belief, is the way its elements and systems communicate between them, which I will try to show. Water is the most vital ecosystem service that our natural environment provides. It is ubiquitous and we have gotten so used to it that we are taking it for granted, since we are not entirely conscious that over the centuries we have been modifying our natural environment for approaching optimum conditions for liveability without reflecting on the consequences this has had upon the environment. We all hear each day about United Nations or Environmental Protection Agency water scarcity summits, but we are not actually aware enough of the strong impact the energy of the water provision services within our buildings have upon the ecosystem and that we can find the remedies, we only need to look around and observe. The water is getting scarcer and despite this fact we are wasting so much of it without even realising. This was the starting point for this research, as well as the fact that it is the most endangered resource which has a very high applicability to the building environment at a global scale. Despite the mentioned facts from above, my first and main inspiration was bio mimicry: the resemblance between a building and a living organism. Being intrigued by this art of emulating nature, I have begun to study it and discovered how important is that the building should be well integrated in its environment, function properly and respond to its context, just as the organism participates in a larger context (on a behavioural level). On the ecosystem level, the building mimics the natural processes and the environment’s (water) cycle. Aiming to expand my knowledge in the sustainable water management sector in order to apply it in my future profession, I am writing this paper presuming that one of the paragons of the future development will be the relation between the ecological technological achievements and the ecosystem. Therefore, I think we will use man-made solutions not only 7
Sustainable water management strategies A possible tool for decreasing the water-end energy
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with nature inspired aesthetics, but more important, with the technical strategies for collecting, recycling and purifying the water working with, for nature, for bringing a contribution on the natural environment’s principles and on the way they behave.
3. Problem Statement Most of us under evaluate the “price” or value of water thinking that is finite and are not really sensible of how much energy it takes to bring it for our use within our household. Therefore, the water security within a building’s usage is more and more threatened, so our concern for conserving the water and re-using it is beginning to grow day by day. Having this said, the main research question is: -How can we reduce the energy in the water end-use energy and through water conservation, purification and re-use? Secondary questions: •
How can we conserve water by purifying it and re-using it within our household for other purposes?
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How are we able to reuse the treated black water for other purposes within our buildings?
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How can we harvest the rainwater and re-use it for other purposes?
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How can we mitigate the storm water runoff through the green roofs?
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How can we adapt to the water scarcity and to the local demands through the implementation of these systems?
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How can these technological systems cope with each other for participating together to the water conservation?
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How can we maximize the use of our natural resources and how to adapt our future buildings to the water scarcity through sustainable water systems?
1.4 Delimitation This paper focus on strictly the technological strategies we can implement within our buildings for re-using and conserving water in order to reduce energy. Analyzing landscape strategies for purifying water or for urban flood control such as artificial built wetlands is beyond the scope of this paper. The “so-called” living machines which have the ability to recycle wastewater through wetlands or which can treat sewage ecologically is not my scope either, since it refers to urban strategies and my main focus is strictly in a building’s usage.
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Furthermore, it stresses the potential of these strategies which we can adopt within our building and site which can be integrated in the whole system for working in tandem with the ecosystem, but not at an urban level. Therefore, it is imperative to keep in mind that through them, at a municipal level, we could have an impact upon the ecosystem. It is addressed strictly to the potential ways of reducing the energy within our water-end use as in a cycle, so always keeping in mind the water steps. Its purpose is also to go beyond the water fixtures we can adopt in our buildings for decreasing the water use. Another important aspect to mention is the fact that I won’t make any socio-economic development analysis either.
1.5 Choice of theoretical basis and sources of empirical data This paper is mainly based on up-to date reports and on Sustainable Building Agencies such as United Nations (UN), Green Building Council (GBC), Leadership in Energy and Environmental Design, Environmental Protection Agency (EPA), since they have a long experience in designing the world’s most efficient and most sustainable buildings as well as the most accurate facts concerning the water threat.
1.6 Choice of research methodology and empirical data As a research method for this paper, I have used both primary and secondary data. Mainly, I have used primary data for getting acquainted with the context, with the actual problem and also with the main theories. The reason for studying secondary data was due to the fact that it contributed to grasping the problem in a more specific manner, making me perceive it from the angle of my profession and reflect on the remedies I could find for elucidating the problem statement in relation with my expectations for the future. The empirical data is based not only on qualitative data, but on quantitative data as well, which is indispensable in this paper, since it was the starting point for my further analysis, being a strong tool in the writing process for fully comprehending the accurate facts. The qualitative data is met along the paper in the sub conclusions of the chapters as well as in the main conclusion, where I state my point of view regarding the specific issue. In case of electronic sources, I have been always comparing them to assure they are alike. My research data methodology for answering to my problem statement is supported by accurate worldwide reports using qualitative data for interpreting them, secondary data and eventually, being supported by practical study cases by leading pioneers of sustainable architecture which provide a strong foundation for the theoretical part. Here it is important to mention the fact that the study cases which I have chosen are built, in order to have more accurate facts upon the efficiency of the systems related to the local regulations building’s behaviour.
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1.7 The report’s overall structure and argumentation The paper is divided in three main parts: •
Introduction: presents the actual situation, the importance of water in relation with the energy we are using for bringing it into our households and its division in the buildings;
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Main section: contains the possible solutions we could adapt for solving the problem stated in the introduction, theory eventually supported by solid cases for seeing the real life implementation;
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Conclusion: represents the sum up of my research and my personal reflection on how we could solve the problem.
The main structure of this paper is based on the ’Pentagon model’ (Stray Jørgensen & Rienecker 2006 p. 28), supplemented with the Theory of Science model. In addition to it, the Russian problem solving tool, “Theory of Inventive Problem Solving” (TRIZ), played a meaningful part. As a working methodology, I first started by getting intrigued by a specific subject which can be approached at worldwide scale in the building industry. Then, along my studies, I have become aware of its importance and of the problems which may arise with it. Because of that, I have begun to reflect upon these problems through my readings wondering how we could solve them. Here, it is important to mention the tool which I had in mind for elucidating them from the beginning was nature (as a mentor).This had also a major contribution, since it helped me indirectly in my research data progress to collect useful materials.
2. Actual situation – The importance of water 2.1 Water scarcity Water is a “critical natural resource”, as Kathrina Simonen (leader of the Carbon Leadership forum) calls it, on which not only the ecosystem depends, but also the social, economic, political issues, which we are surrounded by, lean on. (Simonen, 2014) The water scarcity affects not only the continent, but also 4 out of every 10 people. Off all the water from the Earth, only 3% is suitable for human consumption and the percentage is decreasing day by day. Most of that 3% either is locked in polar ice caps or glaciers or hidden beyond the reach of commercial technologies. A little less than 1% of our water is found in rivers, lakes or underground aquifers. (UN, 2014) 10
Sustainable water management strategies A possible tool for decreasing the water-end energy
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Therefore, the necessity of having quality water for satisfying our human and environmental needs and for our social and economic benefits is a global concern which we should urgently try to solve. More than that, around 80% of the wastewater produced globally is untreated. (UN, 2014).The percentage is huge, consequently highly polluting the water, being required an urgent need for various options for collecting, treating and disposing the water and the waste water more efficiently to stop injuring our ecosystems! Among the years, summits such as Kyoto Protocol and organisations such as United Nations (UN) or Leadership in Energy and Environmental Design (LEED), are just a few which have been striving to solve the water issues, through conserving the water and attenuate its pollution for ultimately reducing the energy. Nonetheless, the water quality data is not highly effective, being a global matter which cannot be solved instantly. Consequently, the demands for our water supply quality, for the storm drainage and for the water consumption in our future buildings are increasing daily. It is becoming very clear that we must make a shift in how we maintain our most important resource we have and in protecting the ecosystem. Through the sustainable water management systems, we see a huge potential for energy reduction through mitigating these issues, as well as a potential way for adapting our systems to the water insufficiency.
2.2 The “embodied energy” - energy intensity of water use In the last couple of years, there have been many studies quantifying the relationship between water end energy uses. In order to obtain sufficient water in our buildings, it has to go through multiple steps which harness the environment and consumes more energy than we imagine. Within a building’s life, the same phenomena occurs. The embodied energy (or the so-called “virtual energy)” is the total amount of energy, calculated on a whole system basis, required for the use of a given amount of water in a specific location (Sharon deMonsabert and Ali Bakhshi, 2009). The embodied energy depends mainly on the quality and type of water, on the pumping requirements for delivery (depending on location, function), on the efficiency of the water systems and on the energy of each consumer and end-use. We can track the urban water cycle into the following steps: source extraction, water treatment, distribution, wastewater treatment, collection and end-use, steps which are depicted in the below figure. Hence, before the water intended for our food services and domestic usage (such as bathing, cleaning, washing) arrives within our buildings, its carbon footprint automatically increases going through these steps.
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In order to have a better understanding upon it, I will briefly describe them, but with emphasis on the energy used in the water end-use and on the wastewater treatment.
FIGURE 1: COMPONENTS OF THE EMBODIED ENERGY IN THE WATER’S CYCLE ( (SHARON DEMONSABERT AND ALI BAKHSHI, 2009)
2.2.1 Raw water source extraction In general, the water supplies come from surface sources such as streams, rivers, lakes or from fresh groundwater, later on being stored in catchment areas or reservoirs, before being carried to the municipality by large aqueduct pipes. The water source is the starting point for the influence of the embodied energy, since it consumes a lot to move and pump water. This energy usually depends on the surface sources (depending if it is groundwater, desalinated water or recycled wastewater), the gravity suffices to supply the power changes, as well as the pumping depth, therefore the energy changes. It depends also considerably on the location and on the local water demands.
2.2.2 Water treatment In urbanised areas, treatment facilities are ubiquitous, providing clean drinking water for municipalities, process water for industrial facilities.
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Depending on the source, the water can require treatment or not in order to make it suitable for human consumption within the demands set by the local authorities. For instance, if the water comes from mountain reservoirs, it needs little or no treatment, whilst from river, streams or lakes require treatment for diverse contaminants or pollutants. Since most of the water comes from the ground, energy is needed for purifying it. For instance, it has been estimated that for the groundwater, the energy is with 30% more intensive, compared to the surface water (Wilson, 2009).
2.2.3 Water distribution to the point of use The transportation to, into and through buildings is made through cylindrical pipes under pressure. The grid of the pipes is laid under the streets, usually the water reservoir is above the level of the building. Therefore, the pressure increases with the height. This step is quite energy-intensive, since the water is treated, pumped to our buildings, and then pumped to wastewater facilities to be treated again. It has been estimated that 2-3 % of the nation’s energy is spent in moving and distributing water every year. The main concern is that the energy demand is expected to increase in the next 15 years with 20-30 % (Amy Hollander, n.d.). So, the water regulations are becoming more stringent for our future communities.
2.2.4 Wastewater treatment The wastewater usually comes from two types of sources: the sanitary sewage (generated from buildings) and from the rain or from the melting snow which drains off rooftops, parking lots and so on. In the past, cities combined wastewater collecting systems in a single sewerage network which collected the domestic wastewater, industrial wastes and storm runoff water. For this reason, nowadays, these systems do not support the level of pollution control required. The main problem is that storm water can contain gasoline spills or chemicals which eventually arrive in a stream or river. Due to this fact, the wastewater is collected through a separate system, conveyed to a treatment point through sanitary sewers, processed from removal of toxins, inorganic substances (such as metal, sand), gases, solid wastes in order to meet standards set by the local water demands from the specific location. Therefore, the wastewater needs much more energy to be treated (chemically, thermally). The storm water is conveyed to their receiving bodies of water through storm drainage networks. Sanitary sewers carry some level of flow during all hours of the day and night, whereas storm sewers flow mainly after periods of rainfall. During major storm events, the volumes of water carried by storm sewers are orders of magnitude greater than those carried by sanitary sewers, therefore they can load the pressure of the pipes, needing more energy. 13
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The municipal water and wastewater treatment facilities are among the most energyintensive entities accounting approximately 35% of energy used by the municipality (EFAB 2011). In fact, according to a recent study, water and wastewater together represent as much as half of a municipality’s total electricity consumption – double that of street lighting. At a global scale, approximately 4 per cent of the nation’s electricity consumption (56 billion kW) goes towards moving and treating water and wastewater (Sharon deMonsabert and Ali Bakhshi, 2009). Of course the demands depend not only on the geographical area and on the local regulations, but also on the capacity of the wastewater systems. Despite these factors, they both have the same main concerns such as disposing fresh water for sanitary human uses, for sustaining the ecosystems’ agriculture and for reducing the water demands. Therefore, we see a great potential in reducing the energy demands, in conserving water, reducing the water demands and volumes distracted to the wastewater system for treatment facilities and pumping stations, eventually mitigating the effects of the water issues. According to Environmental Protection Agency, 10% savings can readily be achieved in this area. (EPA, 2005)
2.2.5 Water end-use energy Once the water reached the buildings, extra energy is consumed in order to prepare it for our intended use (drinking, bathing, showering, washing, cooling, and heating). This extra energy is usually used for purification, heating, cooling and pressurising. Among the years, many studies have discovered a strong potential of energy savings and conservation in the water end-use cycle: “Energy embedded in water at end-uses typically represents the largest energy input in the water use cycle.” (Wilson, 2009) For instance, the team from the “River Network”, made a study in which they have discovered that the energy we are using for heating accounts approximately 75% of the energy and carbon embedded in the water we benefit from. (Wilson, 2009) Where does this potential come from? To make a parallel with Eugene Ionesco saying that “It is not the answer that enlightens, but the question”, in our case the same phenomena occurs. The answer is in the question, therefore, the potential of conserving water and saving energy lies in the energy needed to bring the water to the point of use, as well as from the energy spent for treating and distributing the 14
FIGURE 2: WATER
END USE IN A RESIDENTIAL BUILDING
Sustainable water management strategies A possible tool for decreasing the water-end energy
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water indoor. So, the energy savings are greater when the water end-uses are embodied. The picture from left depicts the percentage of energy used in the water end-use in a residential building. We can easily deduce that the highest percentage is for the toilet usage, clothes washer and shower. Therefore, in them lies also the biggest potential for saving energy. Undoubtedly, the percentage varies when speaking of a residential, industrial or commercial building, but in essence it is still huge. It has been indicated that it takes 95 liters of water to produce 1Kwh of electricity (Amy Hollander, n.d.). This should make us reflect for a moment and try to visualise this cycle within our buildings and the energy required for sustaining our needs, as well as finding alternative solutions for potable, waste water and for reducing the strains on our water supply.
2.3 The “water footprint” assessment The water consumption can be perceived as an “inventory item” or developed independently as a “water footprint”. It represents the way we track the freshwater consumption in the good production or services which our planet uses. (Simonen, 2014) When discussing about the water utilisation in a building, the same philosophy is applied, except the fact that we can measure or model the quantity. Making a parallel with the water’s track in nature, a significant volume can be consumed, which we can categorise in the following three components which are depicted in the picture from below: •
Blue water: the potable water we use for drinking;
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Grey water: slightly contaminated water which has a potential for being recycled for non-potable uses such as irrigation;
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Black water: the sewage or contaminated water.
In the last couple of years, due to the facts which I have described, architects and engineers have been striving to attenuate the water consumption within a building’s usage, by stressing the reduction of the blue water and the division of black and grey water. Taking into consideration the water usage depicted previously, it is perfectly reasonable to adopt these methods for conserving the water or re-using it, as we will see in the next chapter how they function and their efficiency.
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FIGURE 3: WATER USE CLASSIFICATION IN BUILDINGS SYSTEMS (SIMONEN, 2014)
3. Water purification and recycling “It is the property of water that it constitutes the vital humor of this arid Earth.” Leonardo da Vinci
3.1 Gray water recycling The grey water, as the name implies, is in between black and white water. It’s tap water, but more unclean since it is mostly provided from the use of the dish washing, showers, sinks and washing machines. The problem consists of the fact that, usually, it is connected to the overburdened sewage system it shouldn’t be, since it is not toxic (it does not come into contact with the solid human waste, it may contain soap or cooking oil), therefore we are wasting non-toxic water which we could recycle As I have explained in the previous chapter, the highest percentages derive from the mentioned usages. Therefore, we see a huge potential in this context for re-using and 16
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conserving the water and for using it more strategically indoor. Mostly, we could re-use it for non-potable purposes such as: toilet flushing, agriculture, cooling water for power plants construction activities, concrete mixing and artificial lakes.) I am going to analyse its re-use for toilet flushing since it is the most common and the easiest to implement. For instance, the toilet flushing accounts for 1/3 of water use. According to the University of Arizona’s Water Resources Research Center, between 60 and 65% of the water that enters in a home’s drainage has the potential to be reused. (Lepisto, 2006) The American brand “The Aqus”, among others, created a prototype for collecting the grey water from the sink for re-using it which is presented in the above picture. It is designed to be easily fitted into existing fixtures. It is made to work like this: the water from the sink drain is stored in a 21L tank under it, then it is being filtered and disinfected so it can be used for the next toilet flush. FIGURE 4: THE “AGUS” (LEPISTO, 2006)
SYSTEM RE-USING THE SINK GRAY WATER FOR TOILET FLUSHING
The water is transported from the tank via gravity and a small electric pump beneath the sink. The device from the toilet tank prevents the fresh water inflow. If a system as this one would be used by every household, then 4.8 gallons of water flushed down toilets could be saved (Lepisto, 2006). It’s vital to keep into account the fact that this is only one way we could use this strategy, we could also divert it for the showers or for the washing machines or irrigation. Only the local water regulations and the quality demand differ, but the purpose is the same: to learn to use our water strategically through re-using it.
3.2 Black water recycle The term “black water” is used to describe the solid wastewater from the toilets which is considered hazardous. Normally, it is not recycled because it contains a high amount of solid sewage, so a lot of energy would be required for cleaning it adequately for other usages. Despite this fact, due to the water usage problems, there have been invented diverse systems for recycling the black water, making the water usable for using it outdoor for irrigation, for clothes washing or for toilets. The treatment in which the black water consists of is more elaborate, since the matter contains more pathogens compared to the gray one, so it has to go through multiple steps consuming more energy: it should be filtrated very well and disinfected through biological 17
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treatment. This, certainly, depends on the water source, of the plumbing and on the local water demands. In order to understand how the system works, I will describe an example of a system which I found relevant from Aquacell in which they have implemented more types of treatments (physical, microbiological and oxidative treatments) for re-using the water for irrigation and for cooling towers. The black water is collected in a gathering point from where it is pumped in the system for beginning the treatment process. The underneath figure depicts how the water goes through six phases, where the insoluble material is reduced, the bacteria is removed and the protection against pathogens is made, this is the only time when chemicals are used in the treatment process, before being ready for usage. The safe water is being ultimately divided in two tanks, in this case, because of its disposal for the cooling towers and for the irrigation. Through this system, the onsite water reduction can be reduced up to 90% and has also huge contribution to LEED points. (Aquacell, n.d.) Basically, through this system, the insoluble material is reduced to a negligible residue for keeping the water safe by storing it for immediate use. This example is clearly showing there are multiple ways we could re-use the black water and how to reduce the amount of water. An important aspect is also to separate it from the grey water, as the example shows in order not to contaminate the environment. In this way, the energy demand for the plant will decrease, so we will manage to save considerable amounts of potable water. Recycling the black water can significantly help us to get to net zero water consumption in our buildings, according to many studies made among the years. Through the implementation of the presented systems for recycling the grey and black water, we can significantly reduce the need for fresh water, therefore conserve our supplies. In my opinion, it is imperative to be able to 18
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understand these basic principles we can adopt within our house and be sensitive towards the building and site to see which way would be better to adopt. In this way, we manage to use the water strategically in a cycle and to reduce the demands on the public water supply and on the septic systems by reducing the amount of potable water which is distributed to the site for other uses and the volume of wastewater going to the septic systems. FIGURE 5: BLACK WATER TREATMENT AND RE-USE FOR IRRIGATION AND COOLING TOWERS (AQUACELL, N.D.) I think through these strategies we give a good response to the climate changes and to the importance of maintaining our ecosystem healthy and preserving our water. In my opinion, we can reduce not only the water footprint on our buildings, but make a difference at a local level, through reducing the need for more maintenance and treatment.
4. Water conservation through storm water management In rain’s natural cycle, about 30% reaches the aquifers which feed the plants, another 30% nourishes deeper aquifers and approximately 40% is immediately returned into the atmosphere through plant evaporation and transpiration, as the below figure shows. There is rarely any surface runoff. (Scholz-Barth, 2001). In the urban ecosystem’s context, the water’s cycle is more dramatic, when thinking of the effects the climate changes (such as floods) and the extreme weather conditions have upon the pressure of the existing storm water systems and consequently upon our ecosystems and biodiversity (polluting the streams, lakes, rivers). The crucial aspect lays in the impervious surfaces, such as buildings and streets which comprise between 75% up to 100% of the surfaces cover. Consequently, the rainwater is distributed much more differently and it is absorbed much less: 75 % of the rainwater becomes runoff and only 5% infiltrates to the groundwater aquifers and 15% evaporates through the air through (Scholz-Barth, 2001).
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FIGURE 6: THE RAINWATER'S JOURNEY (SCHOLZ-BARTH, 2001) Out of the mentioned percentage, roofs represent approximately 40-50% of the impermeable surfaces, therefore we see a considerable opportunity in their potential role for influencing and controlling the rainwater (Goodwin, 2011). In fact, in the last couple of years there have been many studies which have shown a strong link not only between the dramatic runoff amounts from the roofs, but also in the changes of the water quality in rivers, streams. More than that, we could call the roof the “key” element, since it is the first one which has contact with the storm water. For this reason, it has the highest potential for controlling the rainwater’s runoff and quality. Basically, as impervious the surface coverage is, as much water is wasted and as much water gets degraded back into its cycle, in rivers, lakes and so on. So, as water runoff goes away, it does not have the opportunity to soak into the soil or groundwater reserves, fact which makes our aquifer lose water, therefore disturbing the ecosystem. For instance, one inch of rainfall on a 2,000 square foot residential roof, generates 1,250 gallons of water which can be reused. (Scape, n.d.) Thinking about the fresh water scarcity and on our built environment, we need to take advantage of this opportunity for harvesting, cleaning and reusing the storm water through storm water management strategies or creating a sustainable water infrastructure. “The city is a living ecosystem, therefore it is imperative to understand the relationship between water and other elements, such as roofs and the way these essential elements can interact as in an ecosystem for not harming the environment. Roofs need to become selfsupporting in their water use, possibly with water collected from their own site catchment, keeping in mind the fact that “water cannot be studied in isolation, but must be seen within the context of the total environment”. (Hopkins, 2011). 20
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I will tackle this in the following subchapters the methods we can do this in order to grasp how we could mimic the natural processes, especially the water cycle as a mentor for conserving and re-using our water through harvesting the rainwater and through the living roofs.
4.1 Rain water harvesting This method of harvesting rainwater can be traced back for 2000 years ago in Asia and it is currently used by the richest and poorest civilizations. In developed countries it is made with the help of the implementation of technological achievements for coping with the local water demands and with the carbon emissions, whereas in low income countries, people strive to collect water from self-made systems. Harvesting the rainwater can be really advantageous for places where there is a drought, since it can offer potable water to the community. It can help also mitigate flooding of lowlying areas and reduce demand on wells which normally enable the ground water levels to be sustained. Through this technology, the availability of potable water will increase, since the rainwater is free of salinity, so no energy will be consumed in places where the desalinisation is needed, which is a big opportunity and advantage to use.
FIGURE 7: A TYPICAL RAIN WATER COLLECTING SYSTEM AND ITS COMPONENTS (CENTER, N.D.)
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The most common systems are composed of three main elements: •
the catchment area
•
the collection device
•
the conveyance system
4.1.1 The catchment area The rooftop is the main catchment area, therefore, the amount and quality of the rainwater collected highly depends on the type of roofing material and also on the proper installation of the system. The system is pretty simple and logical, as the picture depicts: the water is accumulated in reservoir from the edge of the roof, then from the gutters which drain the water amount from the container through the down pipes built for this purpose; the rainwater from the gutters can also turn aside from its course, from the gutters, for being conveyed to the storage container for domestic purposes. For managing to collect pure water, the roof material has a strong influence as well. Reasonably pure water, clean enough for drinking can be collected from roofs which are made of aluminum, tiles, slates, galvanised corrugated iron. Therefore, it should be clean enough. Roofs with coatings such as metallic paint are not recommended within this system, since they may bring taste or color to the accumulated water. (Center, n.d.) FIGURE 8: THE RAINWATER COLLECTING SYSTEM (AUSTIN, 2009)
4.1.2 Collection devices Currently, there are more methods for storing the rainwater. In Asia there are used water containers made of earthen materials. This type of water collecting container can be used as 22
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an alternative to battery tanks, storage tanks made of pottery or polyethylene. The polyethylene ones are quite advantageous since they can store a large amount of water (ca. 1000 up to 2000l), they are quite easy to clean and they can be easily fitted with many fittings for the connecting pipes. There can be used also the storage tanks is the fact that they can be used above or below ground, but they should be protected against possible contaminants. (Center, n.d.) When calculating how much water can be stored within the system, it should be taken into consideration the rainfall amount, the length of any dry spells and the water consumption rate. For instance, in most of the Asian countries, the winter months are dry, sometimes for weeks on end, and the annual average rainfall can occur within just a few days. In such circumstances, the storage capacity should be large enough to cover the demands of two to three weeks.
4.1.3 Conveyance systems The third part of the rainwater collecting systems is the conveyance one, which the left figure shows. Its purpose is to conduct the rainwater from the rooftops to the storage tanks through the down-pipes connected to the rooftop gutters. It should be taken into consideration that a problem which we may encounter within the conveyance systems is during storms, when down-pipes can get contaminated with dirt coming from the rooftop and CONVEYANCE SYSTEM
FIGURE 9: A TYPICAL
(UNEP, N.D.)
gutters. Hence, the clean water will be available a while after the storm. The most used method for collecting the clean water in the storages is the “down-pipe flap”. The first flush of water is directed into the down-pipe flap, later on, the rainfall is directed into a storage tank. So, when it is raining, the flap should be left in the closed position, changing the water’s direction towards the down-pipe, being opened only after a while when relatively clean water is collected. The disadvantage within this system is the need for constant observation of the runoff quality and also the manual operation of the flap.
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A sensitive and imperative approach should be given to the pipes’ material, since the rain can have acidic pH, which eventually will cause their corrosion, hence it is be advisable to choose PVC, plastic or any other inert substance. (Center, n.d.) In order to safely fill a rainwater storage tank, the excess water should overflow and it also should be well taken into consideration the diverse blockages or dirt which can appear in the pipes for not contaminating the water supply. Therefore, it should be ensured from the beginning that within the installed system, the rainwater does not enter in the drinking water distribution system. Harvesting the rainwater can be a continuous source of water supply, at a local, regional level and especially for low-income countries where the water scarcity is beginning to increase more and more or in countries where the flooding is quite often, also. The rainwater harvesting technologies conserve the water in droughts and reduces run-off into the storm water drainage system, by making use of our natural resources and conserving the water. In my opinion, through harvesting the rainwater from the roof, we can adapt to the water scarcity and re-use the water within our homes more strategically and more efficiently.
4. Living roofs as a tool for storm water runoff The so-called “living roof” or “green roof” refers to the extension of the conventional roof with a layered system of membranes, substrates and living plants. This technology has been used for hundreds of years in many corners of the world not only because of its aesthetics, reduction of urban heat island effect and thermal properties, but also due to its key role in reducing the storm water runoff and improving the water quality, hence its popularity increased more and more. In urban systems which have combined sewer systems where the storm water and the untreated human and industrial waste are collected, they can easily become overwhelmed by the volume of water and overflow into nearby water bodies resulting in these combined sewer overflows. In contrast to traditional asphalt or metal roofing, they can absorb, store and later evo transpire initial precipitation, thereby acting as a storm water management system, consequently reducing the overall peak flow discharge to a storm sewer. It has been estimated that they intercept between 15% and 90% rooftop runoff and that the absorption rates vary between 50-60% (depending on the growing medium and on the plant type) (Streams, n.d.). Needless to say the fact that these numbers depend also on the location and other external factors. In order to see where this absorption rate lays, I will be analyzing its elements and how they interact with each other.
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FIGURE 10: AN EXAMPLE OF A GREEN ROOF IN HA LONG BAY, VIETNAM (INHABITAT, 2012)
5.1Design principles The secret in a green roof’s storm water management philosophy lays is in the way the construction components interact with each other for absorbing and draining the water properly. Even though each green roof is designed according to the particular context and conditions, I will analyze a typical constructive system, as depicted in the below picture.
FIGURE 11: THE LAYERS OF A TYPICAL GREEN ROOF AND ITS DRAINAGE SYSTEM (GOODWIN, 2011)
•
Waterproof membrane: lies on top of the structural roofing system and has the purpose to protect the leakage of water. Even though the usual roofs are also waterproofed, we have to keep in mind and grasp the fact that it shouldn’t be damaged, thinking that the green roofs it is a more special case, since it is an extension of the conventional roof;
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•
Leak-detection layer: usually it is embedded into the waterproof membrane in order to detect if there are any leaks within the roof area;
•
Drainage system layer: on the top of the membrane layer or barrier, there is located the drainage layer, which has the purpose to impede the extra impregnation of the growing medium, as well as providing the plant roofs with sufficient ventilation. Normally, it is made of high-density plastic which is able to carry considerable point loads for diverse machines (bobcats);
•
Root-protection barrier: usually it is embedded in the waterproofing membrane as a chemical barrier, but usually, a geo textile fabric is used above the drainage layer, at the filter layer;
•
Filter layer: prevents the particles from the growing medium to interfere with the drainage layer, a geo textile filter fabric is placed between the drainage layer and the growing medium.
•
Water storage system (optional): For a possible access of the plants’ roots to a waterabsorbing layer material, hydrocell may be used since it has the advantage of absorbing water as well as oxygen and to release them when needed.
•
Growing medium: it is the substrate determined by its water-retention capacity, aeration, weight and nutrient retention. In the green roof’s potential for conserving water, it plays a major role and it also characterises the green roof’s division, which I will analyse in the following subchapter.
•
Irrigation system: this also plays an important role in the water’s journey, since it is usually connected to a reliable water source with an automatic controller, hence influencing the energy amount. The subsoil, low-volume, low-pressure drip irrigation system is usually installed into the growing medium.
•
Mulch layer: This main purpose of this layer is to protect its substrate from heat and wind. It should be heavy enough and well fixed for not being removed by the wind or birds. It can be organic providing a composting benefit to the growing medium, but which has to be replenished periodically. The inorganic one can consist of pebbles, which are more long lasting, but with no fertilising effect, therefore the specialists should take this into consideration when dealing with this type of system. (Goodwin, 2011)
The underneath picture shows the physical process which helps the storm water runoff, how exactly the rainwater is absorbed and recycled.
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FIGURE 12: THE PHYSICAL PROCESS WHICH CONTRIBUTES TO THE WATER RUNOFF (ANON., N.D.) The philosophy on which the storm water’s runoff and absorption functions is based on nature’s principles, and processes embedded harmoniously with technology, as the picture depicts. This is how they emulate the natural systems: the storm water retaining, the air temperature reduction through evo-transpiration, pollutants removal through capturing the airborne particles on the leaves and deposits on roots, where the micro-organisms feed to transform particles and pollutants into water, CO2 and nutrients. The element which has the most important part in this process is the soil layer, together with the vegetation, which absorb the water which would normally run off into the storm sewer, possibly causing floods depending on its amount or harnessing the environment (being filled with pollutants, metals, pesticides). The vegetation reproduces many of the natural hydrological processes: takes up the rain water which, later on, will be dissipated through evotranspiration, as the figure shows and later will arrive on roof’s layers and a part of the remained water will find its way in the drain at the corner of the installation. The sediments, leaves and other particles are trapped in the soil layer and it will treat runoff before reaching the outlet. Of course, the water retention capacity depends on the soil substrate, on the type of vegetation used and on the local climate. They can mitigate the water amount-pressure upon the storm water infrastructure is because they act as bio filtration devices which remove pollutants such as nitrogen, copper, lead. The roof’s slope has also an essential role, due to the fact that can determine substantially the natural drainage of the water. The flat roofs are not ideal for building a green roof, therefore a slope between 5 degrees and 20 degrees would be the most suitable, due the efficiency caused by gravity. The roofs with a slope bigger than 40 degree can be greened, but the ones with a slope smaller than 20 degree would require a wooden lath for forming some
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fields for holding substrate in place until the plants will form a thick vegetation mat. (ScholzBarth, 2001) With the help of experienced specialists, green roofs can be designed to reduce the storm water runoff to zero, but it can be hard to generalise at a global level. Overseas studies have shown the runoff reductions are between 60%-80%, on average. In this context, it is important to consider the fact that the potential of retaining rainwater differs from summer to winter. As we would expect, during the summer time, a greater amount is returned to the atmosphere through evaporation and transpiration. Retention rates in summer can be between 70% and 100%, but in winter may be 40%-50%. (Hopkins, 2011)
5.1.1 Extensive roof When we are talking about the living roofs as tools for storm water management, we mainly refer to their behaviour towards retaining water, therefore the emphasis is made on the soil layer and vegetation. These are two main influences upon the types of green roof. The extensive roofs are characterised as being lightweight systems with low prostrate vegetation, often being inaccessible. The substrate is around 15 cm, so it can be sowed with deeper rooting plants and it is intended for public use. In general, they do not require so much maintenance and do not need irrigation. When the saturation reaches its highest point, the excess water slowly goes through the vegetation layer to the drainage outlet. For an extensive roof, on average, studies have shown that a 1 inch deep moss and sedum layer over a 2 inch gravel bed retains about 58% of water, a 2.5 inch deep sedum and grass layer retains about 67% of water and a 4 inch layer of grass retains about 71% of water. Therefore, as thicker the sedum is, as efficient the water conservation is. In a major 2-inch rainstorm, generating about 1.25 gallons of water per square foot, a 2.5-inch thick extensive green roof would retain approximately 0.5 gallon of water per square foot, or 40%. (Development, 2015) Due to their applicability, they are implemented more frequently than the intensive roofs.
5.1.2 Intensive roof The intensive roofs are very similar to the gardens on the ground level which people can use like a conventional garden. They are mainly built to be aesthetically pleasing and to support human foot traffic and accessibility. (Hui, 2009) Usually, the substrate is more than 150 mm, fact which makes it a very good moisture retainer. It significantly contains storm water runoff within the roof system. Due to its deep soil depths, it allows a wider diversity of planting such as: trees, shrubs, lawns and herbaceous plantings. (Hui, 2009) 28
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The green roofs are a strong tool proven to respond to our current and future needs concerning the fresh water scarcity and the adaptation of the climate changes. Through this sustainable storm water management tool and through this hydrologic cycle, they help conserving the water by reducing the volume of storm water discharged (red the ejection of millions of gallons of sewage into the local waterways), improves water quality and reduces flooding and protects downstream channels. In my opinion, they are a good method which can help us conserve and protect water and eventually releasing the pressure upon our drainage systems.
6. Case studies In order to understand better the presented systems, I will analyse a few projects for grasping how they could be integrated in a building’s system and how they function. The study cases which I will discuss about will be “real” projects, for supporting the theoretical part, since I find very important to be aware of the way the building behaves after it was built and the energy it saves, since there is always a considerable difference between the “paper” project and the “real” one. What is important to state, is the fact that the emphasis will be made on the water sustainable management, which is not the only strategy which makes the building fully sustainable, or which contributes to its energy reduction/ reduction, but it has a considerable contribution.
6.1 Case study no. 1-Water re-cycle and rainwater harvest-Music and Science Building, Hood River, Oregon USA The project replaces a bus storage barn from 1940 which was previously located on the same site. The building is a net-zero-energy building (thanks to the well-insulated walls, triple glazed windows, details which prevent the thermal bridging) which has received the LEED Platinum in which the water conservation and recycle has a considerable contribution. The most intriguing part in this project is the fact that they have planned a net-zero-water use wastewater, rainwater, but it was unable to achieve it due to the local demands. They have also planned to provide the potable water from the rainwater treatment, which, again wasn’t possible due to the low potable water demands. Still, they planned it in order to be able to add it in the future, separating already the pipes. (Chris Brown, 2013) Despite this fact, they have managed to conserve considerable amounts of water. It is interesting to see what solutions they have chosen to strive through that problem and how they have adapted the solutions to the local water demands.
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FIGURE 15: HOOD RIVER MIDDLE SCHOOL MUSIC AND SCIENCE BUILDING (ARCHITECTURE, N.D.)
6.1.1 Black water and grey water The strategy the specialists used began with was the separation of grey water and the black one. Even though the building has been designed for net zero waste using a black water treatment system, it wasn’t possible due to the regulatory demand of creating a duplicate system which would have been more expensive, this could be easily added in the future by changing the course of the wastewater (Chris Brown, 2013). The below figure presents the cycle of the water from the city water until the waste water. The city water enters first within the building after it is treated. Then, the strategic usage of water is made: we can notice that the non-potable needs such as toilet flushing and irrigation are provided through re-using the rainwater which is collected in a 14,000 l underground tank and which is filtered on-site. For the irrigation purpose, the stream water also brings its contribution, being stored in the same tank with the rain water, but traveling through a heat exchanger before re-used. As the picture shows, the storm water runoff is also collected onsite and then treated 100 % in a bioswale in order to remove the possible pollutants.
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FIGURE 16: THE WATER CYCLE DIAGRAM IN THE BUILDING'S USAGE (ARCHITECTURE, N.D.)
6.1.2 Rain water technology philosophy The underground tanks in which the rain water is filled in for irrigation re-use which is seen in the picture, has an interesting approach, which shows us how the architects have adapted to the local regulations, but in a sensitive manner, always having in mind the new options for conserving the water strategies. The containers have fish in it which fertilise the water, which, later is cycled through a hydroponic growing medium (a hydroponic system is a method for growing plants using mineral nutrients only in water, not in soil) where a variety of plants are grown, filtering the water. The tracking and reporting the electricity data in terms of water use, production and collection was always up to date through using twelve sub-meters. The result is they have managed to save more than 123.000 gallons of water annually. (Anon., 2012)
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FIGURE 17: BUILDING SECTION SHOWING THE RAINWATER STRATEGY (CHRIS BROWN, 2013) (Note: The yellow arrows depict the other sustainable strategies which they have adopted which are beyond the scope of this paper)
6.1.3 Water conservation facts Due to the fact that they have used the stream water and the rainwater for irrigation and toilet flushing, they have eliminated the need for using potable water for these purposes. They have managed to reduce the use of potable water with 89% annually. (Anon., 2012).The other secondary strategies in terms of water usage, despite the water management strategies, which have had their contribution to these savings consist in the toilet fixture approach and the low-water, native vegetation which covers the landscaped area around the building. The figure depicts the potable water use reduction indoor and outdoor. This study case is certified as a truly sustainable building which has received the LEED Platinum certificate not only due to the water management strategies, but also because of the other approaches which they have implemented (such as solar panels, recycled materials, heat recovery systems).
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FIGURE 18: ANNUAL POTABLE WATER USE REDUCTION (ARCHITECTURE, N.D.) To conclude, I consider that this study case teaches us a lot, since it shows us that we cannot always adopt the planned technological systems (as in this case was the black water treatment and making the rainwater potable), but we can always find alternative solutions which can help conserve the water in an efficient mode (even though they didn’t manage to transform the rainwater into potable water, they have used it for other purposes, which, in consequence lead to the same result: conserving water). Therefore, the important aspect is to have in mind what we want to achieve and it is imperative always to remember how one system relates to another one, so, as the ecosystem does, so we shouldn’t treat them independently having seen in this case the way the water technological systems cope with each other.
6.2 Case study no.2- Living roof typology - California Academy of Sciences (CAS), by Renzo Piano I have chosen this project because in my opinion it is one of the best examples which reflects the true meaning of “a sustainable building” in terms of storm water management by showing the interaction between the incorporated systems and of the sensitive approach in the way the living roof’s layers cope with each other for harvesting the storm water. It is said that it’s the greenest museum which was ever built. The main “actor” in the play, which is also the most intriguing element is the undulating green roof which embeds with the landscape through its seven mounds which are designed to mimic the hills of San Francisco, sheltering the planetarium and the rain forest habitat. The 197.000 square feet of green roof and 2 acres of solar panel canopy surrounds the glass ceiling, fact which turned out to be an issue, but it turned out into an opportunity eventually.
FIGURE 13: AERIAL PERSPECTIVE OF CAS’S GREEN ROOF (SCIENCES, N.D.)
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It is the “extensive” type, so it is mainly inaccessible, having the planting depths (growing medium) of 6inch (15.24 approx.), so quite shallow, compared to the “intensive” type in which we can support trees as well. What is really intriguing in this project is the fact that despite the shallow nature of the soil and short layer of the soil, it has a very good interception of the rainfall, keeping it out of storm drains and regulating the seasonal building temperature. One of the biggest challenges when constructing the roof was the “soil retention on the curvilinear, steep domes”, said Kephart, the Rana Creek executive director and holder of the patent of Bio Trays, because of the domes being sharply angled, in some places 45 and 60 degrees“, therefore “How we would retain the soil on those steep slopes was a major design question.” (Gonzalez, 2008) Therefore, the designers have made a feasibility study of existing soil-retention products, but due to the brutal slopes, there weren’t any suitable, since the different plants and their roots systems have various reactions to the slopes of the domes. In order to survive their installation, the vegetation needed a strong structure to resist
6.2.1 Bio Trays innovation After consulting with Renzo Piano, Kephart came up with the idea of developing the “biotrays”. They are made of coconut coir “a fibrous coconut-industry waste product from the Philippines”, especially for this project instead of the traditional modular green-roof trays which are made of plastic. Their advantage is that, being ecological, they will biodegrade during the years, leaving the roots’ plants time to grow through the trays and interact with the soil layer, forming a “living mat” which can secure the soil even on steep slopes, such as in this case. (Gonzalez, 2008) Another innovation which they have made was the inoculation of the coconut coir with fungi (a beneficial bacteria for the growing medium and the tray) which will help retaining more water and preserving the health of the roots, as well. Therefore, this innovation was the “unique solution” for dealing with the problem imposed by the steep slopes which eventually helped to retain more water.
6.2.3 The living’s roof layers The first layer is the structural slab, made of concrete. On its top there is the waterproofing layer. On top of the membrane, there are two layers of 2 inch thick insulation (extruded polystyrene). Next, there is the drainage layer, which is crucial for preventing the roots to rough. The gabion (linear-rock filled baskets) is placed in the corner for a better efficiency of the water drainage and soil retention. These are depicted in the below picture.
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Essentially, I tried to subsurface or sub flow as much water as possible to get it off the surface so we wouldn’t have erosion, said Kephart. The drainage system is a geo-composite one which includes a 3D drainage core. The fabric is attached to the ridges of the face of the core. The 3inch soil medium, which is an organic mix containing fungi and scoria rock is also custom made by Kephart. On top of the soil medium, there are located the Bio Trays which contain an additional 3inch of soil medium.
FIGURE 14: ROOF DETAIL SHOWING THE WATER'S JOURNEY TO THE DRAINAGE ( (PALMER, 2011) In order to test the efficiency of the multi-layered soil drainage section, the team has created full-scale models.
6.2.3 Vegetation design As I have mentioned in the previous chapter, the vegetation has a very important role in the storm water reduction, fact which is also encountered in the case of CAS. In order to see what plants fulfil the best the requirements of having “very little water and no fertiliser and tolerance to the shallow soil”, as they aimed for, they have made tests for more than 2 years, 35
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ultimately choosing 9 (native) species which correspond to the imposed criteria and which require no or very less irrigation. The secret in which the surface flow drainage of plants consists of, is in the grid of the intercept channels created by linear rock-filled baskets. (Gonzalez, 2008) So, the secret in which the surface flow drainage of the 3’’ of plants consists of, is the grid of intercept channels which are created by linear rock-filled baskets. The plants are hoisted up to the roof and fixed onto the plating layer with the gabion, since the flats will disintegrate and become part of the soil system. The storm water that does runoff the rooftop is captured and reused for irrigation of the rooftop vegetation through an underground cistern, when it is needed. In case of heavy rains, the water hold into the water media or reservoir, is directed to a groundwater recharge storm water below the building’s leading dock. The plants return the moisture up in the air through evo-transpiration.
6.2.4 Storm water runoff The presented strategies has a major contribution on distressing the amount of storm water runoff from roots upon the very old existing piping system, since San Francisco is one of the many cities where the sanitary system is mixed with the drainage one. They have made a study of the rainfall data, where they have noticed that only two months of the year were an issue as far as what the soil could hold. Normally, the six inches of soil from the living roof could hold 4 inches of water, therefore the runoff is zero except for those 2 months. They have determined they were holding 3.5 million gallons of water out of the storm drain. The small amount which manages to run off, goes into an underground chamber to recharge the groundwater within the park, so everything works harmoniously in a system. It also filters the pollutants. (Jane Hodges Young, n.d.) The key point which made the project receive the LEED (given by the US Green Building council) points is because of the living roof’s storm water management (despite its other sustainable strategies, such as solar panels). It absorbs about 98% of all storm water, preventing up to 3.6 million gallons of runoff from carrying pollutants into the ecosystem each year. (roofs, n.d.) It is needless to say that it also contributes to its energy conservation by being an excellent insulator, keeps indoor temperatures lower and it reduces the GHG emissions and the heat urban island effect) Besides the LEED Platinum, CAS green roof won also a 2008 Award of Excellence from Green Roofs for Healthy Cities, the industry’s trade association.
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Therefore, in my opinion, among the fact which certifies the efficiency of the roof, I would say that CAS roof it is not only an excellent example of how we could reduce the storm water runoff, but also it teaches us how to adapt to the local conditions, telling us how important is to understand the nature and to adapt to it. In this context, I am specifically referring to the innovations which the engineers made especially for this project. This tells me that there is not one way to adapt to the water scarcity and to reduce the storm water runoff, but it tells me that there are multiple ways, which should have the same result. So, I think the efficiency of the living roof is given by a deep understanding of the problem and of the context, of the specific location, with an emphasis on the local water demands and on the supply and also on the communication between all the specialists. I think that not only the design phase is crucial, but also a very detailed monitoring of how the building acts after it was built. In this case, this was also one of the reasons why it was so successful, since the specialists made constantly tests for monitoring its ability to capture the rain depending on the soil thickness, on the vegetation type and in deep correlation with the steel slopes. This is what makes it truly unique and amazing, in my opinion.
7. Conclusion Our water resources are decreasing day by day globally and it is imperative to act as soon as possible. Even though in some countries more energy is required than in others to convey the water for potable uses, energy which depends on the water source and on the local regulations, the effect is still disastrous: losing our most precious and vital source: water. First, we must act at a local level, then at a municipal one, so we can begin to conserve our water resources at global scale. Only in this way we could have a stronger impact upon our communities, upon our future buildings and cities. Therefore, it is important first to be aware of the scarcity of water, in order to act. I think through this paper I have managed to put a question mark to my readers and to raise awareness concerning all the amount of energy we are using for bringing the water within our household since we are taking it for granted, so we should give much more instead through using it strategically. The biggest potential in decreasing the energy in the water cycle lays within the water-end use, as I have depicted in this paper (as how many studies have shown), for ultimately manipulating it at a wider scale, at a global level and eventually, for having a stronger impact upon our environment, we should start considering it urgently. At this stage, the water management has proofed to be a very useful tool for learning how to use the water strategically through the conservation of the water energy leading to our adaption to the water concerns. Due to the climate changes which cause floods, draughts or many other
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problems, our drainage systems can’t handle the pressure, polluting the environment and the aquifers, so it will be a vicious circle. Through the wastewater management, we can release the pressure upon our systems and conserve considerable amounts of water, fact which was demonstrated in the case of Music and Science Building. Through re-using the grey water for other purposes such as: irrigation, toilet flushing and many, we can save a lot of water amounts. The studied case has demonstrated also the importance of being sensitive to the environment and to the local regulations, fact which is proved through the monitoring of the water efficiency and through the analysis which they have made for choosing the best solution. Their role was also crucial due to the fact that they supported the theoretical basis and showed accurate results. The rainwater harvesting has proved to be a resourceful tool which helps us grasp better the water loss which is made through all of the impervious surfaces, with emphasis on roofs, since they comprise the biggest percentage of the total amount of impervious surfaces. Through the practical case analysed for the Music and Science Building in which the rainwater is stored underground, we have explored the potential of its re-use for irrigation stressing the fact that there is not only one way to do it, but multiple ways. The living roofs, in my opinion are a very powerful tool for tackling the importance of the water which is lost because of them and also in reducing the pressure upon the drainage systems, which will consequently decrease the energy used for treating the storm water. Eventually, it will make less harm to the environment. The California Academy of Sciences is a unique and subtle case which makes us see beyond the conventional through their strategic adaptation to the steep slopes of the roof, of the delicate choice for the vegetation, on the innovation through the invention of the biodegradable bio trays and through the gabion placement in the drainage corner. The building’s behaviour said it all, since receiving the LEED Platinum certificate. The imperative point, in my opinion, is to be aware of these solutions working in a cycle together, not separated, fact which is strongly supported in the MSB study case. Which eventually saved considerable amounts of energy, even though they have explored the possibility of completing the water cycle through collecting the potable water use and did not succeed. Only through this way, we could fully adapt to the water scarcity, following this importance principle of the ecosystem: having all the elements working together in harmony, not separated. Having all these said, my opinion is that through the implementation of these strategies we give a wider meaning to sustainability and have a greater impact upon our build environment through conserving the water, consequently managing to decrease the energy we are using in our water end-use.
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I think I have managed to proof through these strategies that through conserving and re-using water we can save energy.
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