The Capability of Rainwater Harvesting as an Alternative Water Supply

This Rainwater Harvesting System (RWH) is considered the Best Management Practice (BMP) which is being implemented in Malaysia. This system is not only intended to slow down the flow of runoff the surface is even used as a free and safe alternative source of water supply. However, it is mentioned that the system is not viable and impractical considering the construction and maintenance costs that had to be borne by the users of the system. However, several studies inside and outside the country show the Return on Capital (ROC) factor for this system only in a short period, i.e., between two and three years. This article aims to identify the capability of the experimental study site of Rabbitland Jengka Pahang, Malaysia in providing the most suitable or potential location to apply the RWH system. Moreover, it predicts the capability of the RWH system as well as the ROC ability of the system. Results indicate that the level of the system’s reliability is high and the ROC for the investment of the system takes only 36 months to recover the cost of the investment. The National Water Quality Standards (NWQS) for Malaysia proved that RWH and groundwater used are in class 3 which is suitable for livestock drinking, and external domestic uses, and needs extensive treatment for drinking purposes.


Introduction
Malaysia can be considered a country that has received high annual precipitation and high domestic water demand.As a result, Malaysia is in a good position to collect rainwater.Although the rainwater harvesting (RWH) system guidelines were issued in Malaysia in 1999, the use of rainwater harvesting as an alternative water resource is still quite limited due to its slow return on investment and low public acceptance [1].RWH can serve as an alternative water technology that applies to university buildings, is commercially available, and may provide a chance to reduce freshwater use.Alternative waters are long-term water sources since they are not derived from the fresh surface or groundwater, and they can help to meet the need for freshwater.Rainfall harvesting is the collection, diversion, and storage of rainwater from roofs for future use.According to [2], RWH systems can be described as systems that gather rainwater and store it for later use instead of letting it waste as a runoff.
RWH system provides benefits such as conserving potable water, reducing flooding in urban catchments, and reducing nutrient loads to rivers.In addition, RWH can offer additional benefits such 1303 (2024) 012024 IOP Publishing doi:10.1088/1755-1315/1303/1/012024 2 as a smaller carbon footprint compared to conventional water delivery systems and more efficient energy usage due to less pumping needed from source to consumer [3].

Literature Review
Rainwater was generally utilised for a variety of purposes, including landscaping, irrigation, general cleaning, decorative filling of ponds and fountains, cooling tower make-up water, and toilet and urinal flushing [3], [4].The monsoon season, which occurs from March to May and June to September, is crucial for RWH.Unfortunately, most of this valuable water is wasted as runoff.The development of landscape irrigation projects is built on the foundation of water harvesting technology.
In solving the issues of future water scarcity and food security problems, an assessment of RWH must be done to help identify the constraints.In-situ RWH is the most efficient and cost-effective technique for preserving water, and the system is quite effective at retaining rainwater, especially during drought.A rainwater harvesting system is one method for making better use of runoff by gathering and storing it during periods of heavy rainfall for use when water is scarce.This system is typically constructed using either a basic technology, such as pots, tanks, and cisterns, or a complex technique, such as subsurface check dams [4].
RWH systems are classified into two types: roof harvesting systems (RHS) and pond harvesting systems (PHS).The RHS is more well-known and has been used in Jordan, Spain, Italy, Korea, and Malaysia [1], [5], [6].Rainwater collected from the RHS is typically used to meet both nonpotable and potable water demands.RHS has two different installation storage systems, which are placed on the ground and underground.The storage tank is a reservoir that is normally placed near the agriculture field as an irrigation.The runoff that is redirected into storage for the use of Rainwater Harvesting Systems is not lost because it is utilised for water supply.This demonstrates that rainwater collecting systems can provide most of the residential water demand, reducing reliance on conventional water supplies [6].
According to [7], high-income economic countries such as Australia, Greece, Poland, and Taiwan have rainwater collecting systems that can meet 50 to 90 percent of residential water demand, with storage tanks ranging in size from 5 to 76m 3 .Meanwhile, the data for lower-middle and uppermiddle income economic countries such as Bangladesh, Malaysia, and Southwestern Nigeria demonstrate that the domestic water demand that can be met is slightly lower (30% to 80%) than in high-income economic countries, despite the reported size of the storage tank being generally larger.Malaysia is a tropical climate country with comparatively abundant water resources (annual rainfall is estimated to be 2400 mm in the peninsular area) and has never experienced a water shortage in recent decades.However, global warming is projected to reduce future rainfall in various Malaysian states to as little as 32 to 61 percent of average monthly rainfall, particularly during the drought season from May to August.Figure 1 depicts the average monthly rainfall data for Negeri Pahang, Malaysia.This implies that Negeri Pahang saw extremely significant rainfall throughout the year.

Month
Many studies and research have been undertaken on RWH systems to minimize reliance on water resources and prevent water shortages, particularly during drought seasons, but the potential of RWH system application in Malaysia has not been fully implemented.More studies are required to confirm that the gathered rainwater is fit for its purpose.This research is based on the usage of RWH systems for landscaping and irrigation in upper-middle income countries with tropical climates, as these countries have a humid climate and a lot of undeveloped land.Its large storage tank capacity provides a great benefit for water supply since it reduces reliance on ordinary tap water.
In general, the objectives of this study were to identify the capability of the experimental study area that is the Rabbitland Area, located in Pahang, Malaysia in providing the most suitable or potential location to apply a RWH system.Moreover, it predicts the capability of the RWH system as well as the ability to return the cost of return on investment (return on capital) of the system.Besides, it is also to classify the water quality index for the collected rainwater and groundwater tube well of the study area.
The selection of this area was due to the excessive untreated water consumption for general cleaning, livestock drinking, watering the plants, bathing the pets, fishponds, landscaping, and other external purposes.The mean daily temperature for this area is about 27°C and the average monthly rainfall precipitation data ranged from 49 to 273 mm.The lowest rainfall precipitation data were recorded in February, with an average of 49 mm, while the highest amount was 273 mm in November.

Methods
This study was carried out in the Rabbitland located in Bandar Pusat Jengka, Pahang, Malaysia (Figure 2 and Figure 3   This project acts as a sustainable model of alternative water resources which is in line with the Sustainable Development Goals (SDGs) No 6. that ensures water availability and sustainable water and sanitation management [8].For general cleaning, drinking water, animal baths, watering plants, and other purposes, the management of Rabbitland uses alternative water resources that were from RWH and groundwater from the adjacent tube well.
Rainwater is collected using a gutter and is supplied into 400-gallon tanks and each of these tanks is connected to a piping system to be used from one area to another.If the collected water within the tank has dried up, the groundwater will be pumped into the tanks to be utilized as a substitute for the water.There were two parts of the methodology being carried out in this study.The first part is to measure the RWH to determine the daily water consumption rate of the Rabbitland area.This is important to calculate the return on capital (ROC) period for the investment of the system.The second part was carrying out in-situ fieldwork and laboratory testing to determine and classify the water quality index for the collected rainwater and groundwater of this study area.

Measurement of Rainwater Harvesting
The measurements were conducted within 3 months, the first was in February when the rainfall data was the lowest, in June when the rainfall data was moderate, and the last was in November when the rainfall data was the highest.This is important to ensure rainfall availability throughout the year.Three RWH tanks with different locations were measured in height purposely to record the initial water level.The water level was measured at the end of each operating day to record the daily water consumption where the difference between the initial and final measurement readings represents the amount of water used within the duration of the experiment period.For daily drinking water consumption, a total of 5 drinking bottles with a capacity of 4L were placed in the rabbit cage.The initial and final reading of the water level was recorded at the end of the operating day.The total difference in water volume per day represents the water consumption of rabbit drinking water.

Water Quality Monitoring and Assessment
The chemical and physical variables of the collected RWH and groundwater were measured directly using the YSL Proplus Probe.Tests were conducted according to the Standard Methods for the Examination of Water and Wastewater (APHA, 2005).Five (5) parameters were selected to record during the in-situ study which are Dissolved Oxygen (DO), turbidity, temperature, Electric Conductivity (EC), and pH.To ensure the readings taken are accurate and correct, the equipment was calibrated prior to use based on the manufacturer's directions.For the laboratory testing, to reduce all the activities and metabolism of the organisms in the water body, the samples collected from the field will then be stored in a cool room with a temperature below 4°C.For the laboratory testing, five (5) parameters were tested for determining the water quality index according to the National Water Quality Standard (NWQS), Malaysia methods which are Biological Oxygen Demand (BOD5), Chemical Oxygen Demand (COD), Suspended Solid (SS), and Ammonia-Nitrogen (NH3 -N).The water quality index will be obtained by using the equation stated below: (1 Where WQI is the water quality index; SIDO is the sub-index of DO; SIBOD is the sub-index of the BOD; SICOD is the subindex of COD; SINH3 -N is the sub-index of NH3 -N; SISS is the subindex of TSS; SIpH is the sub-index of pH.Sub-indexes for all parameters will be calculated from the sub-index calculation table provided by the Department of Environment (DoE) Malaysia.

Results and Discussion
This section is divided into two parts, namely the analysis of the return on capital of the system and the second analysis of the water quality classification.

Return on Capital Analysis
To analyse the importance of investing in the proposed project, a cost-benefit analysis was done to compare the expected costs against its expected revenue.The sampling of water demand and consumption was conducted to measure the water used for drinking and cleaning purposes.The data were tabulated in Table 1 below.According to Perbadanan Air Pahang (PAIP), the rate of bill water tariff for commercial uses is RM 1.45 per m3.Therefore, 2.868m3/d x RM1.45/m3 x 30 d = RM 125 / month and as much as RM1500 per annum can be saved from water charge bill payment expenses.The construction cost of the whole system, including the tanks installation, piping system, fitting systems, and gutter installation was around RM5000, so it only requires a total of 3 years for the return on capital (ROC) period for the investment of the system.

Water Quality Analysis
In order to determine the classification of the water quality index for the collected rainwater and groundwater tube well in Rabbitland, a laboratory test analysis has been conducted and the result is shown in Table 2. From the data obtained, according to National Water Quality Standards in Malaysia, it is proven that RWH and groundwater (GW) used are in Class 3 and are suitable for livestock drinking, and external domestic uses, and need extensive treatment for drinking purposes.The analysis was also conducted on other parameters as shown in Table 3.The results indicate that all parameters of GW gave higher concentration as compared to RWH.The higher groundwater concentration was also the result of high concentrations of certain elements such as sodium, sulphate, boron, fluoride, etc. [9].Salinity refers to the amount of salt in the water.
Since dissolved ions increase salinity and conductivity, the two measures are interconnected.The high value of turbidity in GW is due to the high amount of organic and non-organic substances that are suspended and dissolved, such as mud and fine sand.The higher value of the suspended density contributes to a higher degree of turbidity.The high value of chlorine may be associated with the presence of saltwater intrusion, mineral dissolution, and industrial and domestic waste.

Conclusions
A rainwater harvesting system is an example of an optional water supply system that can be used in industry as well as services.This study has shown that local meteorological conditions in Bandar Pusat Jengka, Pahang, Malaysia are suitable for the development of the system.The reliability of the system is high and the ROC for the investment of the system takes time only 36 months to recover the cost of the investment.The National Water Quality Standards for Malaysia prove that RWH and GW used are in class 3 which is suitable for livestock drinking, and external domestic uses, and needs extensive treatment for drinking purposes.

Figure 1 :
Figure 1: Average rainfall data per month for Negeri Pahang, Malaysia.
) (3.76896,102.54904)which is about 1.5 km from Universiti Teknologi MARA Cawangan Pahang, Kampus Jengka, Pahang, Malaysia.Rabbitland which covers an area of almost 4.5 acres is a mini zoo for about 17 species of animals and covers a 1-acre area of plants and herbaceous trees.

Table 1 :
Water demand and consumption

Table 2 :
Result of Water Quality Index

Table 3 :
Comparison of the water quality of RWH and GW