Ireland; Rainwater Harvesting and Greywater Treatment: Systems for Domestic Application in Ireland

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Ireland; Rainwater Harvesting and Greywater Treatment: Systems for Domestic Application in Ireland
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  Dublin Institute of Technology   ARROW@DIT  ArticlesSchool of Mechanical and Transport Engineering2010-05-20 Rainwater Harvesting and Greywater TreatmentSystems for Domestic Application in Ireland Zhe Li  Dublin Institute of Technology  , zhe.li@dit.ie This Article is brought to you for free and open access by the School of Mechanical and Transport Engineering at ARROW@DIT. It has beenaccepted for inclusion in Articles by an authorized administrator of  ARROW@DIT. For more information, please contact yvonne.desmond@dit.ie, arrow.admin@dit.ie. Recommended Citation Li, Z.: Rainwater harvesting and greywater treatment systems for domestic application in Ireland. Desalination. Volume 260, Issues1-3, Pages 1-8. 30 September 2010. doi:10.1016/j.desal.2010.05.035  Rainwater harvesting and greywater treatment systems for domesticapplication in Ireland Zhe Li ⁎ , Fergal Boyle, Anthony Reynolds Department of Mechanical Engineering, Dublin Institute of Technology, Bolton Street, Dublin 1, Ireland a b s t r a c ta r t i c l e i n f o  Article history: Received 5 March 2010Received in revised form 19 May 2010Accepted 20 May 2010Available online 12 June 2010 Keywords: Rainwater harvestingGreywater treatmentSustainable livingDomestic water supplyIreland Water shortage has been recognised as one of the key issues facing many countries. Fortunately, there arerelatively abundant water resources available in Ireland because of its plenty of rainfall. However, Ireland willinevitablyencounterwatershortageinthefuture,especiallyinurbanareas.ThewaterconsumptionpercapitaperdayinIrelandisoneofthehighestinEurope.Thewaterdemandisstillincreasingduetopopulationgrowthand higher standard ofliving. The useof domestic rainwater harvesting andgreywater treatment systems hasthe potential to supply nearly 94% of domestic water in Irish households. The utilisation of these systems canhelpIrishhouseholdersachievesigni fi cantwatersavingsandavoidthedomesticwaterbillsthatareduetobereintroduced.It alsohelps take pressure of the centralised watersupply to meet the increasing water demandin Ireland and eliminates issues such as high leakage during delivery and large treatment costs for domesticutilisation. Domestic rainwater harvestingand greywater treatment systems canplay avery important role infuture water management and prospective sustainable living in Ireland.© 2010 Elsevier B.V. All rights reserved. Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22. The current domestic water situation in Ireland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.1. Current domestic water consumption. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.2. Current issues in domestic water supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.2.1. The cost of the public water supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.2.2. Water leakage in the distribution system. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.2.3. Private group water schemes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33. The key drivers for applying domestic water systems in Ireland. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.1. Domestic water charges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.2. Climate change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.3. Demographic changes and rising in the standard of living . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.4. The quality of water for non-potable use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33.5. Potential cost savings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44. Domestic rainwater harvesting and greywater treatment systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44.1. Domestic rainwater harvesting system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44.1.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44.1.2. System components. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44.1.3. Domestic harvested rainwater quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54.1.4. Treatment of domestic harvested rainwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54.1.5. Bene fi ts of a domestic rainwater harvesting system. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64.1.6. Cost of a domestic rainwater harvesting system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64.2. Domestic greywater treatment system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64.2.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64.2.2. Characteristic of greywater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Desalination 260 (2010) 1 – 8 ⁎ Corresponding author. Tel.: +353 14022991. E-mail address: zhe.li@dit.ie(Z. Li).0011-9164/$ – see front matter © 2010 Elsevier B.V. All rights reserved.doi:10.1016/j.desal.2010.05.035 Contents lists available atScienceDirect Desalination  journal homepage: www.elsevier.com/locate/desal  4.2.3. Greywater treatment technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64.2.4. Costs of a domestic greywater treatment system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75. Potential water savings by using domestic water systems in Irish homes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7Acknowledgement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction Water shortage is becoming the largest problem in the worldtoday. Freshwater resources have been increasingly polluted anddepleted globally. This is constantly threatening sustainable develop-ment, and human and ecosystem health[1]. The water supply canhardly keep pace with demand nowadays. The global demand forwater has doubled roughly every 21 years.Ireland has an abundance of water resources because of its highrainfall levels. However, water shortage will be one of key issues thatIreland has to envisage in the very near future, especially in thegreater Dublin region. Water demand has been constantly increasingdue to the population growth, higher standard of living and climatechange, with the result that water shortage is expected to occur inIrelandinthenext10 yearsorevenbefore[2].Providingsuf  fi cientandadequate water for the estimated 5 million people in Ireland by 2021is going to be a major task for the Department of the Environment,Heritage and Local Government. The quality of water in many Irishwater resources (e.g. lakes, rivers and water reservoirs) hasdeteriorated in recent decades due to climate change and humanactivities. Large costs and high leakage levels are amongst the keyissues in the public centralised water treatment and water delivery inIreland.The use of domestic rainwater harvesting (DRWH) and greywater(GW) treatment systems can signi fi cantly lessen demand from thepublic water supply. These systems can be part of the solution fortackling water shortage in Ireland, and can be an important part of Ireland's sustainable development. The bene fi ts from an economicpoint of view are for both the country and householders. Inparticularly, the future introduction of a domestic water supply anda wastewater treatment charge could make these water systems evenmore attractive for householders. This paper outlines the currentwatersupplyissuesinIreland,thekeydriversforapplyingDRWHandGW treatment systems, and the currently available systems.Thereis anonus onthe government toimprove the understandingof the social impact, the potential, and the performance of domesticwater systems in Ireland. Information should be provided from publicwater sector to help householders accept domestic water systems.This information could also assist householders to assess the systems'costs and bene fi ts. Domestic water systems can both provide a sourceof water and can involve the public in water management, thusmaking householders more aware of water conservation andrecycling. 2. The current domestic water situation in Ireland The current domestic water situation in Ireland can best bedescribedfromtwoaspects:currentdomesticwaterconsumptionandcurrent issues in domestic water supply.  2.1. Current domestic water consumption The water supplied to the residential sector is a signi fi cant portionof total publicly-supplied water in Ireland. In 2006, domestic usageaccounted for approximately 60% of the total water demand[3].Agriculture, commercial and industrial consumption accounted forthe remaining 40%. Ireland's domestic water consumption per capitaper day is one of the highest in Europe. Domestic water consumptionper capita per day in selected EU countries is shown inFig. 1.The water consumption per capita per day increased from 130 l – 139 l in 1997 to 148 l in 2006 in Ireland[3]. Along with populationgrowth and climate change, the rise in the standard of living is one of the main factors for the increased domestic water consumption,especially for personal hygiene. In a typical house, the volume of water used for toilet fl ushing, showering and bathing, and in washingmachines and dishwashers is much greater than the volume of waterused for drinking and cooking. The breakdown of domestic waterconsumption per capita per day in an average household in Ireland in2006 is shown inFig. 2.  2.2. Current issues in domestic water supply The cost of the public water supply, water leakage in thedistribution system, and private group water schemes are the maincurrent issues in domestic water supply.  2.2.1. The cost of the public water supply Around 80% of the population-receiving water supply is fromsurface abstraction (rivers and lakes and reservoirs) in Ireland[3].Groundwater and spring-supply water account for 18% and 2%respectively. As a result of climate change and human activities,surfacewater has beenextensively contaminated and polluted and itsquality is not adequate for domestic use. Water must be treated to ahighstandard in order to make it fi t for human consumption. Therewere 869 water and sewage schemes invested in between 2004 and2006 across Ireland with a total cost of approximately € 5 billion[5,6].The costs involved in constructing treatment plants, processing waterand delivering water to households are substantial. The annualcost of the public water supply has to be raised through general taxation,even though the water is free for domestic householders in Ireland.Table 1shows the annual costs for water supply in Ireland in 2006.  2.2.2. Water leakage in the distribution system The level of water leakage during delivery is high in Ireland incomparison with other EU countries. According to a recent study, atypical EU country has a water leakage of around 30% of total water Fig.1. Averagedomesticwater consumptionpercapita perdayinselected EUcountriesin 2006[4].2 Z. Li et al. / Desalination 260 (2010) 1 – 8  supply[8].The overall water loss during distribution was in excess of  40% in the Dublin region in the late 1990s, but was reduced to 30% by2008[2]. This was achieved by large expenditure on pro-activeleakagemanagementandsubstantialnetworkrehabilitationschemes.Over the last seven years, € 140 million was spent on monitoringwater use and losses throughout the supply network, fi xing leaks andreplacing defective pipes in Ireland[9]. However, leakage stillaccounts for as much as 45% of the water supply in the distributionsystems in some urban areas[10]. This corresponds to 60 l to 100 l of water production losses per capita per day in Ireland. These massivewater losses from leakage result in wasted expenditure on unneces-sary water treatment, leakage management and water networkrehabilitation. The estimated wasted expenditure is approximately € 120 million between 2007 and 2011 alone[2].  2.2.3. Private group water schemes Water is supplied by private group water schemes if householdsare not connected to the public water supply in Ireland. There are 588private group water schemes currently running in Ireland[11]. Theseschemes are formed by a number of households coming together toprovide their own water supply. The water supplies are either fromthe public (if available) or a private source (well or lake, etc).However,waterhastobepaidforifthehouseholdbelongstoaprivategroupwaterscheme.Waterqualityhasbeenseenasthemainconcernfor private group water supply. According to national reports on thequality of drinking water in Ireland, the poorly treated or untreatedprivate group water supplies are most at risk from pollution[12]. Thelocal government does not have any input into the running of groupschemes as they are not responsible for maintaining group schemepipes and fi ltration systems. 3. The key drivers for applying domestic water systems in Ireland The key drivers show the necessity and urgency for applyingdomestic water systems in Ireland. These systems will help Irelandestablish a sustainable water policy and prevent water shortages.  3.1. Domestic water charges Thedomestic waterchargein urbanareaswas abolished inIrelandin 1997[13]. However following serious concerns about watershortage and the recent fi nancial crisis, the domestic water charge isexpected to be reintroduced by the Irish government as soon as 2010[13]. However, generally there are no water meters installed indomestic houses and, as a result, the water cannot be charged withvolumetric measures. A fl at water charge of around € 200 perhousehold per year is the preferred solution from the Irishgovernment until water meters are installed[14]. It is planned toinstall water meters for the whole 1.1 million houses that areconnected to the public water mains across Ireland over a two-yearperiod. The potential water charge could have a large fi nancial impacton Irish householders and, in particular, low-income families. Thefuture cost of water per household is not known yet in Ireland.However, the UK water cost per household can be taken as a valuableexample, as the average water consumption per capita per day iscomparable and the cost of living is similar between Ireland and UK.The water bill for an average household with three occupants isbetween £170 and £300 per year in the UK[15]. Apart from thedomestic water supply charge, wastewater treatment is also chargedin the UK and depends on the amount of wastewater released forpublic water treatment. The wastewater charge is about £130 to £300a year for a domestic house and this could also be introduced inIreland. The current price of water per m 3 will be expected to risebecause of the increasing water demand. Irish householders may befacing similar water bills as their UK counterparts.  3.2. Climate change The alteration of Ireland's climate due to the effects of climatechange is not fully known. The rainfall patterns will likely vary in anunexpected manner[16]. Climate change is also expected to lead tohotter and dryer summer months and wetter winter months. Climatechange may also alter the groundwater regime, and thus the 18% of ground-source-supplied water is at the risk of being affected inIreland[3]. Finding new water sources and developing newtechnologies to produce water in large scale are crucial to meet theincreasing public water demand.  3.3. Demographic changes and rising in the standard of living  Population growth has been recognised as one of the mostimportant factors in increasing water demand in Ireland. Thepopulation is expected to increase from the current 4.5 million to anestimated 5 million by 2021 in Ireland[17]. Even though the majorityof these new households are likely to be small, that could be less thanthe current 2.8 person per household in Ireland[18]. The growingnumberof householdand rising in the standardof living will raise theoverall water demand as a result of increasing use of washingmachines, showers, toilets and gardens, etc.  3.4. The quality of water for non-potable use Using 2006 fi gures, only 6% of domestic water supply is used fordrinking and cooking purposes[3]. The rest of the water supply doesnot have to reach drinking quality. However, domestic water isgenerallynot supplied throughseparate pipes for different utilisation.The high-quality treated water is unnecessarily used for low-quality-required appliances. It is not energy ef  fi cient and economical to usehigh-quality water for these appliances as they only require low-quality water. As Ireland has very little indigenous fuel resources, themajority of energy produced is from imported fossil fuels[19]. Energysaving is therefore very important for the country's sustainable  Table 1 The annual costs for the public water supply in Ireland in 2006[7].Category Billions of EurosCapital costs 0.678Operation costs 0.638Total costs 1.316Payments by industry and other non-domestic sectors 0.133Net annual costs 1.183 Fig. 2. Breakdown of domestic water consumption per capita per day into various usesin Ireland in 2006[3].3  Z. Li et al. / Desalination 260 (2010) 1 – 8
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