Rainwater Harvesting in Multifamily Social Interest Housing. Regina Lúcia Melo de Oliveira, Marília Karla da Silva Santos and Simone Rosa da Silva

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1 Journal of Civil Engineering and Architecture 9 (2015) doi: / / D DAVID PUBLISHING Rainwater Harvesting in Multifamily Social Interest Housing Regina Lúcia Melo de Oliveira, Marília Karla da Silva Santos and Simone Rosa da Silva Polytechnic School of the University of Pernambuco, Recife , Brazil Abstract: This study evaluated the reduction of water consumption in a SIH (social interest housing) complex from the simulation of implanting a rainwater harvesting system. The methodology consisted of characterization of the case study, survey data of water consumption and data of precipitation in the area, on-site visits to define the average consumption and monthly water distribution, and sizing of a rainwater harvesting tank following the Netuno Program. It was obtained L as the ideal volume for the tank, supplying the demand for drinkingwater in 32%, although the reduction in the drinking water bills would be minor, since the object of the case study is considered SIH, and residents pay a fixed fee for consuming up to 10 m 3 per month. Therefore, it becomes necessary to analyze this situation from a sustainable and environmental perspective, and the benefits are no longer only economic, but rather they take on a more comprehensive social dimension. Key words: Rational use of water, rainwater harvesting, rainwater collection, social interest housing. 1. Introduction The majority of the world s population is located in urban centers, which proposes a series of needs that must be met. Among these needs, there is the supply of water, which is vital for the development and survival of human beings. In this way, progress in general and the preservation of health are conditional on an efficient service of water distribution [1]. According to Kelman [2], since the year of 1950, the world s population has increased three times, while the demand for water has increased six times. The rational and sustainable use of water is a necessity today considering the problems of water scarcity and pollution that the planet has been facing. According to Marinho et al. [3], sustainability has a complex and long-term purpose and should, therefore, be in mind daily, always with new alternatives and possibilities of reduction involving this precious element. For years, the rainwater harvesting for drinking and Corresponding author: Regina Lúcia Melo de Oliveira, civil engineer, research fields: rational use of water and rainwater harvesting. rlmo_pec@poli.br. non-potable consumption has been used in several countries. Domènech and Saurí [4] found that, in the city of Barcelona, Spain, although there was little amount of rain and high rainfall variability demand, the toilet bowl of a single family housing can be supplied, as over 60% of the irrigation of gardens demand in single or multi-family buildings. Slys and Stec [5] performed an analysis of the life cycle of two variations of the water supply system for sanitary in a multifamily residential building in Rzeszow, Poland: (1) municipal supply system; (2) capture rainwater. They concluded that the use of rain water stored in tanks is more profitable considering the costs of initial investments for construction and operation and maintenance costs. In Australia, Zhang et al. [6] confirmed the viability of rainwater use in residential buildings in the cities, Sydney, Melbourne, Perth and Darwin. Rahman et al. [7] analyzed the sustainability of rainwater harvesting systems in a residential building multiple floors hypothetical in Sydney, Australia, in different scenarios. They found that a higher roof area is more favorable in terms of water savings and financial benefits and maintenance costs are responsible for

2 1262 Rainwater Harvesting in Multifamily Social Interest Housing most of the costs of a rainwater collection system. Previous researches have shown that tanks with larger storage capacity can maximize water savings in multi-family buildings [8, 9]. Paradoxically, larger areas constructed of multi-family buildings may limit the room for rainwater storage tanks [10]. Eroksuz and Rahman [8] highlighted some solutions to this problem: the incorporation of water storage tanks on the foundation of buildings, or the use of a series of interconnected smaller tanks. However, Hunt and Jones [9] warned that the costs of pumps and pipes for each tank reduce the practicality of the latter solution. Ghisi and Ferreira [11] evaluated the potential for potable water savings by using rainwater in a multi-family residential building in Florianopolis, South Brazil. The result showed that the average potential for potable water savings is ranging from 14.7% to 17.7% whereas the water for toilet flushing and laundry cleaning do not need to be potable. As for water potability, Helmreich and Horn [12] mentioned that rainwater can be contaminated by bacteria and chemicals and therefore require treatment prior to use, especially when it is for human use. Cunliffe [13] stated that, after contact with the collection surface, it suffers several forms of contamination, such as bacteria, algae and protozoa, and it is therefore advisable to only use it for non-drinking purposes. Tomaz [14] stressed that under no circumstances should rainwater be used for drinking purposes without prior treatment. In the sense of economy and sustainability, the use of rainwater is highly recommended in sanitary basins, cleaning of common areas, irrigating gardens and car washing. Today, with the growing awareness of urban sustainability, there is an increase in the number of projects and equipments designed for water efficiency in buildings, although most of these have a high cost of deployment and thus become inaccessible to the population of low-income. In this sense, this study was developed to propose a measure of water conservation in SIH (social interest housing), with the sizing of a rainwater harvesting system from the simulation in a specific case study in the city of Recife. The general objective is to assess the reduction of water consumption in the housing complex from simulating the deployment of the system. The objectives include quantifying the average water consumption in the residential complex Clube do Automóvel (Car Club), calculating the water demand and distribution of water consumption, rainfall analysis and sizing the tank. 2. Materials and Method 2.1 Characterization of the Case Study The object of this analysis is the residential complex Clube do Automóvel, located in the neighborhood Cordeiro in Recife, Pernambuco, Brazil. This residential complex is an area of SIH with constructer partly with municipal resources and partly through the Minha Casa Minha Vida (My House My Life) Program of the Federal Government. The total housing set has a m 2 area of natural soil of the 2, m 2 area of land property. It has approximately 3, m 2 of constructed area, which is composed of two towers with four floors and eight apartments per floor, totaling 64 housing units. Each unit has 40 m 2 of usable area subdivided into two bedrooms, a living room, a bathroom and a kitchen/service area, comprising four people on average, and each one has six water outlets (shower, toilet, washbasin, kitchen sink, laundry tub and washing machine). The water supply is performed by the public supply concessionaire COMPESA (Pernambuco Water and Sewage Company). There are individual water gauges in the condominium and there are no water outlets for collective use for the cleaning of common areas (halls and stairs), car washing or irrigation of gardens. These activities use water from the apartments of the residents, who need to transport water from their

3 Rainwater Harvesting in Multifamily Social Interest Housing 1263 apartments to the location of use. In a visit to the condominium, the existence of some free areas was observed, where a future deployment of a lower tank for a rainwater harvesting system would be possible. A green area was observed next to the lower tank that could be used for the rainwater tank. Then, a maximum area for the installation of the tank of 18 m 2 (3 m 6 m) was considered, and a maximum depth of 2 m, totaling a maximum volume available for deployment of the rainwater tank of 36 m 3. As for the area of rainwater collection, entire roof extension was used and in both towers it would be approximately m Data Collection and Preliminary Treatment Demand of Drinking Water The drinking water consumption of residential complex Clube do Automóvel and its history of water consumption were analyzed, provided by COMPESA for the period of January 2012 to October It was found that the combination of residential consumes approximately 526,400 L per month. Relating monthly consumption with the number of housing units, each apartment consumes 8,225 L per month on average. For the determination of per capita consumption per day, an average of 256 residents (four residents in 64 apartments) was considered, and the following equation was used: Q C = P 30days where: Q: flow (L/month); P: estimated population; C: water consumption used per day, on average, per resident. Thus, we have: C = 68.5 L/resident day Thus, the per capita consumption of the residential complex Clube do Automóvel is close to values found by several other researchers in Brazil. Cohim et al. [15] concluded that, in the municipality of Simões Filho, Bahia, a region of low income, the consumption per capita average is 80 L/resident day, with values ranging between 74.3 and 86 L/resident day. Dantas et al. [16] developed in their research that, in Itajubá, Minas Gerais, it was concluded that the per capita consumption in residences of social interest in this region varies from 80 to 133 L/resident day with an average of 117 L/resident day Rainwater Demand Table 1 shows the distribution of residential water consumption, from the perspective of several authors. The first point is characterized residential consumption in Switzerland, performed by SVGW (Schweizerischer Verein des Gas-und Wasserfaches) [17]. Then, the analysis from the data obtained from the PNCDA (Programa Nacional de Controle do Desperdício de Água) [18] presents very distinct values compared to the rest, because in this case the use of the toilets was considered saving water. Refs. [19-21] defined their values for distribution of water consumption from the analysis of residences of the Brazilian middle class. As there are more recent studies and they better reflected the reality of the case study considered herein, they were used for the analysis and creation of an arithmetic mean of residential water consumption from the values which are shown in Table 1. This mean is presented in Fig. 1, which shows that the shower is the leader in water consumption, with about 30 %, and the only way to alleviate or reduce its consumption is through educational and saving measures, since the drinking water used for baths cannot be replaced by non-drinking sources. However, about 32% of such consumption can be saved by replacing the use of drinking water with the use of rainwater, including the use of the toilet, water for gardens and car washing Rainwater Runoff Coefficient The runoff coefficient is used to represent the percentage of the total volume of precipitation that is

4 1264 Rainwater Harvesting in Multifamily Social Interest Housing Table 1 Distribution of water consumption by various authors [17-21]. Apparatus SVGW [17] PNCDA [18] Mieli [19] PURA-USP* [20] Hafner [21] Toilet 33% 5% 35% 29% 22% Wash bin 6% 8% 6% 6% 7% Shower 32% 55% 27% 28% 37% Kitchen sink 3% 18% 18% 17% 18% Washing machine 10% 11% 7% 9% 9% Laundry tub - 3% 4% 6% 4% Dishwasher 6% Gardens/car 5% - 3% 5% 3% *PURA- USP: Programa de Uso Racional da Água- Universidade de São Paulo. Laundry tub 6% Washing machine 8% Gardens 4% Toilet 28% Kitchen sink 18% Shower 30% Wash bin 6% Fig. 1 Average distribution of residential water use [17-21]. collected by the rainwater system. Therefore, the volume of rainwater lost by absorption and evaporation when reaching the collection surface is ignored. This coefficient depends mainly on the type of surface for the rainwater collection. The roof of the residential housing has channel type ceramic tiles, with an estimated value of 0.80 to It was used the value of 0.9 for this simulation, indicating that 10% of the rainwater captured corresponds to the losses due to the cleaning of the roof, evaporation and disposal [14] Rainfall Data from rainfall on a daily basis from the Meteorological Station of Recife (Curado) was used, belonging to INMET (National Institute of Meteorology), corresponding to the period of March 1, 1961 to June 30, 2014, totaling a historical series of 53 years. The station coordinates are 08º05 S and 34º95 W and its altitude is 10 m. These data were obtained through the Hidroweb of the ANA (National Water Agency) [22]. The choice of this station is justified by the fact that it has the most extensive and consistent historical series of the municipality of Recife and is at a distance of approximately 3 km of the residential complex Clube do Automóvel, the object of the present study. This practice is usual, since a meteorological station represents the climatic characteristics of a radius of up to 100 km from its origin Disposal of First Flush According to Tomaz [14], the disposal volumes the quantity of water from the catchment area sufficient to carry dust, soot, leaves, branches and debris. After

5 Rainwater Harvesting in Multifamily Social Interest Housing 1265 three days without rain, the roofs will accumulate dust, leaves and debris, and it is recommended that the first flush is not used for consumption. The surveys show that the first flush varies from 0.4 L/m 2 of roof to 8 L/m 2 depending on the location. In the absence of local data, a disposal value of 2 L/m 2 of roof area is suggested; This will be the value used in this simulation. 2.3 Program Netuno Netuno is a computational program conceived by LabEEE (Laboratory for Energy Efficiency in Buildings) of the Federal University of Santa Catarina, used for simulating rainwater catchment systems. Through data that allow an adequate modeling of the system, it presents results, such as the relationship between the drinking water savings potential by using rainwater and the capacity of the tank, the overflow volume of rainwater, among others. It also allows economic analyses to be performed for the simulated system [23]. To find the ideal volume of the tank, this study varied from the initial volume of the lower tank at intervals of 500 L. The ideal volume was considered to be the one in which the variation in the volume of the tank showed a smaller increase than 0.5% in potential savings, in comparison with the previous volume. After this, there was a variation in the percentage to be supplied by drinking water at 15% and +15 %, in increments of 5%. This variation was performed based on simulation made by Marinoski and Ghisi [24], due to the uncertainties in the estimates of the demand for rainwater. 3. Results and Discussion The ideal volume of the rainwater accumulation tank and its drinking water savings potential were obtained by means of program Netuno. The maximum volume of the lower tank was set as 36,000 L, due to the volume available for the construction of a tank in the residential complex Clubedo Automóvel being 36 m 3. The next step for the choice of the appropriate volume was varying the volume of the lower tank. Program Netuno indicated the ideal volume for the rainwater tank to be the value of 22,500 L, with a drinking water potential savings of 16.35%. If the available maximum volume of 36 m 3 had been used, there would be an increase in relation to the ideal volume of only 1.49% in potential savings. As previously explained in Section 2.3, due to the uncertainties in the estimates of the demand for rainwater, for different percentages of non-drinking end uses, the ideal volume of the lower tank, the drinking water savings potential and the daily demand of rainwater can be found. Therefore, the percentage of 32% obtained in the estimate of end use (non-drinking) varied from 15% to +15 %, in increments of 5%. These data are presented in Table 2. Thus, the ideal volume for the lower tank indicated remains 22,500 L, since moving to the following percentage of demand to be replaced by rainwater (37%) increases savings potential by only 0.7%. To illustrate this low variation, it was verified that a tank with 100,000 L would provide a drinking water Table 2 Results of ideal volume sizing for different percentages of end use for non-drinking water. Percentages of drinking demand Drinking water potential savings Ideal volume of the lower tank (L) Daily demand of rainwater (L) to be replaced by rainwater (%) 17 22, , , , , , , , , , , , , ,148.21

6 1266 Rainwater Harvesting in Multifamily Social Interest Housing Table 3 Volume (L) General data on the ideal volume. Drinking water potential savings (%) Consumed volume of rainwater (L/day) Consumed volume of drinking water (L/day) Overflow volume (L/day) Rainwater demand fully met (%) Rainwater demand partially met (%) 22, , , , Table 4 Month Initial estimates consumption. Total monthly consumption (L) Rainwater consumption (L) Drinking water consumption (L) Price of bill without use of rainwater (US$) Price of bill with use of rainwater (US$) Rainwater demand not met (%) Monthly savings (US$) January February March April May June July August September October November December Average Average (m 3 ) Average (m 3 /apt) savings potential of 20.22%, only 1.52% higher than the savings of a tank with half of its capacity (50,000 L). Considering the ideal volume of the tank to be 22,500 L, Table 3 presents the general data on the lower tank for rainwater catchment. The scaled reservoir completely replace 16.35% of potable water consumption of residential Automobile Club in 42.76% of cases during the year. 4. Conclusions When analyzing (in Table 4) the initial estimates of consumption and projections of prices in the water bill, according to local rates, it is clear that there is no real reduction in costs in the bill, since this case study is of SIH and its residents have the right to pay the social rate when they consume up to 10 m 3 /month. In this case, the monthly average was calculated at 8.62 m 3 /month, so even with a reduction of 15% or more in water consumption, it would still result in a bill of the same price. It should be emphasized that the most anticipated is the decision by use of rainwater, and less spending will occur with installation, making the choice of implementing a rainwater harvesting system more viable from the design phase. Thus, the deployment of the rainwater harvesting system in SIH areas will not possess its final value fully disbursed by residents. It is important to emphasize that the tank is normally one of the most expensive components of rainwater catchment systems, and its proper sizing is important. It should not remain empty for a long period of time, and rainwater should not be wasted in relation to demand. Therefore, the decision to build a rainwater harvesting system in buildings with small catchment areas will not be made with the sole purpose of saving money, but also aiming to ensure future water sustainability, promote water conservation and help to control floods. The main advantage associated with the use of rainwater, in addition to reducing the consumption of drinking water, is the reduction in the discharge flow rate for the urban drainage system,

7 Rainwater Harvesting in Multifamily Social Interest Housing 1267 which contributes to the reduction of floods and inundation resulting from waterproofing, such as decks and building covers. Thus, it becomes necessary to analyze the rational use of water from the sustainable and environmental point of view, since the obtained advantages are no longer economic, for few, but rather they take on a more comprehensive social dimension. References [1] Gonçalves, R. F Water and Energy Conservation in Public and Building Systems of Water Supply. Rio de Janeiro: ABES-PROSAB (Associação Brasileira de Engenharia Sanitária e Ambiental-Programa de Pesquisas em Saneamento Básico). [2] Kelman, J The Challenge of Taking Water to Everyone. Magazine and Environmental Education 12 (1): [3] Marinho, M., Gonçalves, M., and Kiperstok, A Water Conservation as a Tool to Support Sustainable Practices in a Brazilian Public University. Journal of Cleaner Production 62 (1): Accessed May 20, S [4] Domènech, L., and Saurí, D Comparative Appraisal of the Use of Rainwater Harvesting in Single and Multi-family Buildings of the Metropolitan Area of Barcelona (Spain): Social Experience, Drinking Water Savings and Economic Costs. Journal of Cleaner Production 19: [5] Slys, D., and Stec, A The Analysis of Variants of Water Supply Systems in Multi-family Residential Building. Ecological Chemistry and Engineering S 21 (4): [6] Zhang, Y., Chen, D., Chen, L., and Ashbolt, S Potential for Rainwater Use in High-Rise Buildings in Australian Cities. Journal of Environmental Management 91: [7] Rahman, A., Dbais, J., and Imteaz, M Sustainability of Rainwater Harvesting Systems in Multistorey Residential Buildings. American Journal of Engineering and Applied Sciences 3 (1): [8] Eroksuz, E., and Rahman, A. Rainwater Tanks in Multi-unit Buildings: A Case Study for Three Australian Cities. Resources, Conservation and Recycling 54: [9] Hunt, W. F., and Jones, M. P Performance of Rainwater Harvesting Systems in the Southeastern United States. Resources, Conservation and Recycling 54: [10] Ghaffarianhoseini, A., Tookeya, J., Hoseinib, A. G., Yusoffb, S. M., and Hassanb, N. B State of the Art of Rainwater Harvesting Systems towards Promoting Green Built Environments: A Review. Desalination and Water Treatment 9 (March): [11] Ghisi, E., and Ferreira, D. F Potential for Potable Water Savings by Using Rainwater and Greywater in a Multi-storey Residential Building in Southern Brazil. Building and Environment 42: [12] Helmreich, B., and Horn, H Opportunities in Rainwater Harvesting. Desalination 248 (1-3): [13] Cunliffe, D. A Guidance on the Use of Rainwater Tanks. 3th ed. In Water Series. Adelaide: National Environmental Health Forum. [14] Tomaz, P Utilization of Rainwater of Urban Coverage Areas for Non-potable Purposes. Digital Book. Accessed March 2, downloads/livros/livro_conservacao/capitulo8.pdf. [15] Cohim, E., Garcia, A., Kiperstok, A., and Dias, M. C Water Consumption in Low-Income Residences Case Study. Presented at 25th Brazilian Congress of Sanitary and Environmental Engineering, Pernambuco, Brazil. [16] Dantas, C. T., Ubaldo Jr, L., Potier, A. C., Ilha, M. S., and De, O Characterization of the Use of Water in Homes of Social Interest in Itajubá. Presented at National Meeting of Built Environment Technology, Florianopolis, Brazil. [17] SVGW (Swiss Association of Gas and Water Compartment). Carefully Usage of Water. Hittnau: Atelier Fischer. [18] PNCDA (Ministry of Planning and Budget) Ministry of Cities. PNCDA. Accessed October 20, na. [19] Mieli, J Reuse of Home Water. Graduation Program of Civil Engineering, Concentration Area: Civilian Production. M.Sc. thesis, Fluminense Federal University. [20] PURA-USP (Programa de Uso Racional da Água- Universidade de São Paulo) Presentation of the Program of Rational Use of the Water from the University of São Paulo. PURA-USP. Accessed October 25, pdf. [21] Hafner, A. V Conservation and Reuse of Water in Buildings: National and International Experiences. Master thesis, Federal University of Rio de Janeiro. Accessed April 17, index.php/component/docman/doc_view/1594-ana-vrenihafner-mestrado?itemid=. [22] ANA (National Water Agency) Hydrological Data Historical Series. ANA. Accessed October 25,

8 1268 Rainwater Harvesting in Multifamily Social Interest Housing [23] Ghisi, E., and Cordova, M. M Netuno 4: User Manual. LabEEE/UFSC (Laboratório de Eficiência Energética em Edificações/Universidade Federal de Santa Catarina) research report. [24] Marinoski, A. K., and Ghisi, E Utilization of Rainwater for Non-potable Uses in School: Case Study in Florianópolis-SC (Santa Catarina). Built Environment, Porto Alegre 8 (2):