Rainwater harvesting (RWH) is proposed as the concept of accumulation and deposition of rainwater for use instead of allowing it to runoff. RWH systems are able to simultaneously address the water scarcity problem and reduce the dependence on domestic water supply. In Malaysia, the government began to promote the use of RWH system in 1999. With the recent increasing water shortage and rationing events, RWH has started to gain its practical application. In Malaysia, the Green Building Index (GBI) has set up green rating tool for building in order to promote sustainability in built environment. RWH is one of the rating tools under water efficiency and carry 10% of the total score for non-residential building and 12% for residential building. The purpose of this paper is to introduce the RWH System. It covers the previous research about RWH and overview the RWH policy and development.
Definition Rainwater Haversting System
Rainwater harvesting is a technique of collecting rainfall as a supplementary source of water supply for households, commercial and industrial premises, landscape watering, livestock water, and irrigation of agriculture. The planning and development of rainwater harvesting systems shall be carried out adhering to the principles and guidelines described here. This is to ensure that the system complies with sustainability, water quality and design standard. The collection of rainfall from the roof of a building, usually referred to as rainwater harvesting (RWH), and its subsequent use for non-potable applications, such as water closet (WC) flushing or garden watering, is a simple method of reducing the demand on the public water supply. The benefits of RWH are then considered in detail before reviewing the different types of RWH systems which are commonly used in developed countries. The main system components, namely, catchment area, treatment methods and storage tanks are discussed in relation to how they affect system performance. The capacity of the rainwater store is important both economically and operationally. The size of the store influences both the volume of water conserved and volume of water flowing into the storm sewers, the installation costs and the final quality of water supplied by the RWH system. The quality of delivered rainwater is assessed in terms of its physical, chemical and microbiological characteristics and will affect system acceptability, potential health risk and the selection of system components.Rainwater Harvesting Policies and Development
In 1999, the “Guidelines for Installing a Rainwater Collection and Utilization System” was first introduced by the Ministry of Housing and Local Government (KPKT) after 1998 drought event. It was the initial phase of RWH policy in Malaysia. It aimed to reduce the dependence on treated water and provide a convenient buffer in times of shortfall in water supply. The guidelines proposed the construction of rainwater collecting tanks in urban area instead of continuing to build giant dams upstream and it served as a reference for those who want to install a rainwater collection and utilization system. However, the implementation of the first RWH policy was not really successful back then. This was because RWH was still very alien to Malaysian, it gen erally did not deal with cost and implementation issues and most of the systems were not available locally.
In 2004, one cabinet paper was prepared by the KPKT and submitted to the National Water Resources Council to encourage government buildings to install a rainwater collection and utilization system. The council encouraged installing rainwater collection and utilization but it was not mandatory. Two government agencies, namely the Department of Irrigation and Drainage (DID) and the Ministry of Energy, Water and Communication (KTAK), were the pioneers in implementing RWH system in their buildings. However, the acceptance of RWH system was also not satisfactory in the beginning stage whereby it was only introduced in a few new housing development projects.
Type of Rainwater Harvesting
There are two types of rainwater harvesting which is
Indirect Gravity – This type of system differs in that the harvested water is first pumped to a high level tank (header tank), then allowed to supply the outlets by gravity alone. With this arrangement, the pump only has to work when the header tank needs filling. Also the mains water is fed directly to the header tank, not into the main harvesting tank.
Direct Pump – Instead a booster pump set is used to provide a pressurised supply. This system employs the benefit of not having to feed mains back-up water to the underground tank, whilst also offering great flexibility as the booster pumps can be tailored to suit the flow and pressure requirements of the building.
Component of rainwater harvesting system
Whether it is large or small, a rainwater harvesting system (RWHS) has five basic components:
Catchment area – the surface area which catches the rainfall. It may be a roof or impervious pavement and may include landscaped areas;
Conveyance – channels or pipes that transport the water from catchment area to a storage;
First flush – the systems that filter and remove contaminants and debris using separation devices;
Storage tanks – where collected rainwater is stored;
Distribution – the system that delivers the rainwater to the point of use, either by gravity or pump.
In certain case where collected rainwater is for potable usage, purification involving filtering, distillation and disinfection are the optional components in rainwater harvesting system.
From this paper, it highlight about the type of Rainwater Harvesting System, the definition of Rainwater Harvesting System. On this paper also cover on the policies and development of Rainwater Harvesting System. It then reviews a component that have in Rainwater Harvesting System.