EFFECTIVENESS OF RAINWATER HARVESTING SYSTEM AT OFFICE BUILDING IN COPING WITH CLIMATE CHANGE

Ir Dr Mohd Nasir Mohd Noh*, Norasman Othman**, Kamarul Azlan Mohd Nasir***, Mardhiah Farhana Binti Omar***, and Ellya Hayati Binti Omar

*** * Bahagian Saliran Bandar, JPS HQ, Kuala Lumpur ** Falculty of Civil Engineering, Universiti Malaysia Pahang (UMP) *** Falculty of Civil Engineering, Universiti Teknologi Malaysia (UTM)

Abstract: Rapid socio-economic development has begun to put a strain on Malaysia’s water supply and drainage facilities. Climate change has also caused higher intensity rainfall and prolonged drought. Rapid development has not only caused frequent flash flooding, but also has caused deterioration of water quality in the receiving water bodies. Climate change has caused some area to experience shortage of water supply due to drought. This water stress came to the fore on the back of the 1998 drought induced water shortages, which brought unpleasant water supply disruptions for 1.8 million residents in the Klang and Langat Valley. So, in order to overcome the water supply shortages problem, domestic roof water harvesting could be carried out in water stress area and areas that are experiencing prolonged dry period.Therefore, a case study of rainwater harvesting system for non-potable use at JPS Raub Office, Pahang was conducted. The system includes the catchment’s area, gutter, underground storage tank, elevated tank, pump and water meter. The instruments that were used for the data collection is rain gauge, level logger and water meter. The data collection program commences from 1st June 2008 until 1st June 2009 at JPS Raub. Historical rainfall data from 1990 until 2008 was analyzed for continuous dry period. Rainfall collected from the roof will flow via gutter while surface runoff at the pervious area will flow into the drain and stored in underground storage tank. Collected rainwater pumped into elevated tank and distributed to the toilet for flush, standpipe and landscape via gravity. Rainwater storage tank design is checked with recorded data. Four water meters were installed in JPS Raub to determine rainwater consumption. Average weekly rainwater usage is 16m³ where 72% is for toilet, standpipe at 3.2% and 2.4% for landscape. The result shows the utilization of the RWH system can reduced the usage of treated water by as much as 45% based on the monthly water bill.. Keywords : Rainwater Harvesting System, Underground storage tank, Continuous Dry Days, Climate Change, non-potable, water consumption, 1. INTRODUCTION

Rapid socio-economic development has begun to put a strain on

Malaysia’s water supply and drainage facilities. This strain came to the fore on the back of the 1998 drought induced water shortages hitch brought unpleasant water supply disruption for 1.8 million residents in the Klang and Langat Valley. The drought event jolted the nation to explore alternative water resources such as rainwater for conserving the public water supply. The drought spurred Government interest in rainwater harvesting and utilization. On 7 May 1998 the Minister of Housing and Local Government expressed the Government’s interest for houses to be designed for collecting rainwater. In 1999, the Minister of Housing and local Government produced a guideline on installation a Rainwater Collection and Utilization System.

Rainwater harvesting is a technology to collect and stored rainwater from

rooftop catchments, open surface, ground surface and also pavement or gravel surface. Nowadays, it has been improved from using jar collection system to underground storage tank with a mesh filter to avoid unnecessary waste or suspended solid flock in the tank. It is consider economical to maintain the system rather than build the system. This is due to constructing the system may increase cost for it is not practically known in Malaysia and the installation of the system are different from a normal water supply system. However, maintenance of the system is easy and simple where it can be done by users. Maintenance are necessary to remove suspended solid on the rooftop catchments and the conveyance system to avoid clogging and also particle that will produce pollution to the water stored in the tank.

The rainwater harvesting system depends on the rainfall frequency and intensity at the area and the size of the catchment's area. The rainfall frequency and intensity need to be frequent and high and the catchment area need to be large to make the system feasible where it is necessary for one session of rain to fill the tank up to the maximum level of storage. Installation of RWH system helps to reduce flood where it reduce runoff on the pavement area, save cost where it reduce usage of treated water and ecosystem where it helps to reduce pollutant on rivers and the shortage of water basin and water intake area. It will be easier and more economical if every developer built the system together with the building development rather than retrofitting the system to the existing building.

1.2 Study Objective The objective of this study is to determine the reliability of the existing

system in providing rainwater for non-domestic usage for office building 1.3 Scope of Work To achieve this objective, the following scope of work will be performed;

1) Determine catchment area for every development unit 2) Rainfall and Surface Runoff data collection 3) Data quality assurance

4) Determine above/below ground storage tank characteristics. (Storage Volume, Outlet and Pumping Characteristics)

5) To compare usage of treated water before and after installation of RWUS.

2. METHODOLOGY

The study will look at the quantity and quality of the rainwater stored in the tank. Samples for rainwater quality were collected for a week and analyzed. One is to define the average number of continuous dry days for the study area. The purpose is to determine the optimum design of storage tank capacity that is needed for that particular area during dry whether season. Second is to analyze the usage of the rainwater in comparison with the treated water supplied by JBA Pahang. This is to determine the effectiveness usage of the system installed in the area and third is to analyze how much volume can be stored in the tank for one rainy session and how sufficient the existing tanks are.

The rainwater harvesting system at JPS Raub is design to meet the capacity of 24 m³ with the average storage without raining is 16 days for underground storage tank. The estimated usage of rainwater per day is 2 m³. The catchments area can be divided in two areas that is impervious and pervious area. Impervious area is the roof catchments areas which consist of three roof building areas with the total of 1289 m² area. 1189 m² is the total of the roof catchments area while 100 m² is the area for the road hard standing. All roof catchments are assigned with the gutter and conveyance system for collection of rainwater. For the pervious area, it is the area with the green scenery with a total up of 80 m².

Instruments that were used in the data collection program include rain

gage, water meter and level logger. However, level logger data could not be used due to faulty equipment. Rainfall data was collected at JPS Raub and historical rainfall data were obtained from JPS Ampang. Rainfall data collection is used to determine dry days for groundwater storage tank design, while meter reading are used to obtain rainwater usage capacity. Monthly water bill for JPS Raub was used to compare the treated water usage before and after installment of the system.

The typical RWHS (Figure 3) consists of underground storage tank,

elevated tank and pump. The function of underground storage tank was to collect surface runoff from impervious and pervious area (Figure 1 and 2). Collected rainwater is pumped into the elevated tank and distributed to the toilet for flush, standpipe and landscape by gravity flow. Toilet cistern uses two valves that are connected to rainwater valve and JBA water valve. If the rainwater supply stopped, JBA water flow in the system after the valve is

opened.

Figure 1 : Pervious Area Figure 2 : Impervious Area

( Roof Catchments with gutter and conveyance system)

Figure 3 : The typical system of RWHS

3. STUDY AREA

The office building chosen for this study is the JPS Raub which is located at Jalan Cheroh. The rainwater harvesting system (Figure 3) is made up of a below ground storage tank, rainwater tank and a pump. The below ground

storage tank is to collect surface runoff from roof, while rainwater tank is to store water that is pumped out from the below ground storage tank. The rainwater tank is to supply rainwater to utilities that utilizes it such as toilet, stand pipe and washing basin. The rainwater flows by gravity to these utilities. The standpipe provides rainwater for washing the floor, drain, and vehicles and also for landscaping. In the case of system breakdown, a back up system or contingency plan is prepared for this system. The back up system provides alternative source of water, where treated water is allowed to replenish the rainwater tank if there is no water for toilet flushing. The storage tank receives surface runoff only from the roof and pavement.

Elevated Tank

Toilet

Standpipe

Underground Storage Tank

Figure 3 : Rainwater Harvesting System in Study Area

The rainwater harvesting system consists of gutter collection system,

below ground storage tank, rainwater tank and pump. The gutter system will collect roof runoff and transfer runoff to the storage tank. The dimension of the below ground storage tank which includes the sump for pump is able to store rainwater up to about 24 cubic meter. There are two over flow pipe that will lead out the rain water as the amount of rain water entering the underground storage tank are exceed the capacity of the tank. Figure 3.2 shows the dimension of DID-HQ Underground Storage Tank

4.0 RESULT AND ANALYSIS 4.1 Rainfall Analysis

The rainfall data was collected since 1st June 2008 until 28th January

2009 at JPS Raub. The table below showed the summary data that start collected from 1st June 2008 until 28th January 2009:

Table 4.1: Summary rainfall data collected at JPS Raub

The Total Rainfall Depth 821 mm Average Daily Rainfall 3.4 mm Maximum rainfall depth 54 mm Longest Period Without Rain 9 days

Historical rainfall data for the same site (Station No 3818054) was obtained from JPS Ampang, and analyzed. The record of rainfall data period that was analyzed is between 1990 and 2008. It is used to compare the result between summary rainfalls data collected at JPS Raub. The analyses are to determine the number of continuous dry days for this site and average daily rainfall.

Figure 3.1: Total dry day since year 1990 until 2008

TOTAL NO. OF DRY DAY SINCE YEAR 1990 UNTIL 2008 AT JPS RAUB

21

16

1014

19

12

20 1915

13

20

14

1916

12

27

12

39

16

05

1015202530354045

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2005

2006

2007

2008

YEARS

DA

YS

Figure 4.1: Number of Continuous Dry Days

Figure 4.1 shows the total number of dry day since between 1990 and 2008. The average number of continuous dry days is 19 days. The assumption for the design of the underground storage tank volume is based on 14 continuous dry days.

4.2 Rainwater Usage Analyses

Rainwater usage can be divided into two; weekly and daily. For the first situation is the rainwater usage excluding and including Saturday and Sunday at toilet for flush, standpipe and landscape at JPS Raub.

Figure 4.2 shows percentage of weekly rainwater usage. The rainwater

usage during weekdays is about 21 m³ where 72.1 % is for toilet flushing, usage for standpipe is at 3.2 % and 2.4% for landscape. However, usage in a week is about 15.8 m³, where 72.4 % is for toilet flushing, usage for standpipe is at 3.5% and 2.6% is for landscaping. Average daily rainwater usage in JPS Raub is about 2 m³.

Figure 4.2: Percentage of Rainwater Usage for Toilet Flushing, Standpipe

and Landscape. 4.3 Treated Water Usage The monthly water bill for JPS Raub was used to measure the success of the RWHS. The RWHS is supposed to reduce the usage of treated water for non-domestic purposes. The monthly water bills since year 2006 until 2009 were used to gage the effectiveness of the system. The RWHS was fully in operation at end of November 2007.

Figure 4.3: Water supply usage before & after use RWH System

Figure 4.3 show the water supply usage before and after use RWHS. Since, the utilization of the system, monthly treated water usage can be reduced by 45% has calculated from the water bill.

4.4 Rain Water Quality Index

An analysis was performed to the samples taken from the rainwater

stored in the tank. The result shows that the quality of the water is not suitable for domestic purposes. Few parameters are selected for this study such as pH, temperature, Dissolved Oxygen (DO), Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). From the result, the highest concentration parameters are BOD and COD with the value of 5.77 mg/l and 10.0 mg/l on January, 29 2009 at 3 p.m. The highest concentration on BOD and COD value shows that the water is polluted. Investigation on the cause shows that the water is polluted with some organic waste such as waste water from a leaking sink pipe and the waste from bird that have been wash along with the first flush rainwater. Theoretically, concentration of dissolved oxygen in water during rain is higher compared to the BOD concentration where it is lower in the rain and the result proves the theory.

The highest result of DO concentration is 5.65 p.p.m on January, 30 2009 where it starts raining at 8.00 am.The pH concentration for the sample is stable where every sample shows result in range of 6.00 to 6.44 pH which indicates that the water is alkaline. The water quality index shows that the water is in class 3 (non-potable use only). The stored rainwater could be used for potable purposes if simple treatment is provided. However, it could be quite costly.

5.0 CONCLUSION The water quality analyses results shows that the stored rainwater in the

tank is contaminated with sediment and unnecessary suspended solid. The maintenance is not done on a regular basis. The filter box is full with sediment, dead leaves and fruits. However the contamination can be control with regular maintenance and monitoring. Besides that, the stored rainwater can still be used for non-potable such as for toilet flushing system, cleaning of vehicles, lawn, garage and also can be used for fishery for landscape area. This may not only save the cost of using treated water but also helps Malaysia in reducing treated water cost and supplies.

Analysis on the rainfall data and the usage of treated water shows that the system is quite effective in reducing the consumption of treated water. This is due to some reduction seen in the graph plotted for the treated water consumption in year 2007 and at the end of year 2008. The total usage of the rainwater for the period of eight month (Jun 2008 – January,31 200) is 451m³. This is slightly higher than the expected usage of about 392 m³ (+ 59 m³). This shows a positive attitude of the user towards the used of the system. Analysis on the volume of rainwater can be stored in the tank in the other hands shows that the tank can be full in two session of rain with the average 12.75 m³ per

session with assumption that everyday usage are 2 m³ for a month.

Based on the analysis of the historical rainfall data collected from JPS Raub for 18 year period, it shows that the average of continuous dry days is 19 days. However, the maximum number of continuous dried days is 39 days (November-December 2007). This extreme event coincides with the article that was published in January, 10 2008, by the Earth Policy Institute that the year 2007 is the second warmest year in the whole world including Malaysia. Acknowledgement The author would like to extend his gratitude to JPS, Bahagian Saliran Bandar for funding this project and for allowing the collected data to be used for this paper.

6.0 REFERENCES Ferdausi, S. A., & Bolkland, M. W. (2000). "Rainwater Harvesting for Application in Rural Bangladesh" 26th WEDC Conference, WEDC (web based pdf) Fujioka, R. S. (1993). "Guidelines and Microbiological Standards for Cistern Waters" Proceedings of the 6th International Conference on Rainwater Catchment Systems. Gould, J. (1993). "A Review of the Development, Current Status and Future Potential of Rainwater Catchment Systems for Household Supply in Africa" Proceedings of the 6th International Conference on Rainwater Catchment Systems, IRCSA, Nairobi Hune (2001) Report on Water Tank Development in Ethiopia and Kenya, SIDA IDRC (Apr/1986) Rainwater Catchment - Status and Research Priorities in the Southeast Asian Region (Proceedings of the Regional Seminar and Workshop Held in Khon Kaen, Thailand, 29 November to 3 December 1983, (Report No. IDRD-MR127e). IDRC, Canada. Lee, M. D., & Visscher, J. T. (1990) Water Harvesting in Five African Countries, (Report No. Occasional Paper 14). IRC / UNICEF, The Hague Li, H., & Liang, S. (1995). "The Catchment and Unilisation of Yard Rainwater in Zhuanyaogou Valley" 7th International Rainwater Catchment Systems Conference, Beijing.

Monthly Treated Water Consumption

53

109

36 5226

500 0

148

89

160

0

74

0

351

104 11966 75

39 38 25 13 030

82

163

88

385

4093

49 48

180

94

95 13 8 15 8 6 0 0 0 0 0 00

50100150200250300350400450

January February March April May June July August September October November DisemberBulan

Usa

ge (m

3)

2006200720082009

Figure 4.3 : Water Consumption Before and After Installation