A review of greywater recycling related issues: Challenges and future prospects in Malaysia

To realize Malaysia's vision of becoming a developed country by the year 2020, rapid urbanization and development have taken place in many parts of the country. Despite vast development in Malaysia, the country experiences a myriad of water shortage issues. Therefore, Malaysia needs to carefully manage its freshwater resources to achieve sustainable development. Greywater has proven to be a useful substitute for fresh water for non-potable activities. This paper reviews examples of greywater recycling that have been successfully implemented globally, and identifies constraints of implementing greywater recycling systems for use in Malaysia. Greywater represents 43-70% of total domestic wastewater volume, and reusing greywater for irrigation may have adverse long-term impacts on soil. Greywater should be treated and disinfected before reuse, and can be disinfected via chlorine, UV, or ozone disinfection. Chlorine disinfection is recommended as chlorine is widely available and inexpensive. Malaysia lacks strategies for kick starting greywater recycling projects. To overcome obstacles, Malaysia could establish a moderate treated greywater quality standard (pH 6-9, TSS < 20 mg/L, <5 NTU, BOD5 < 20 mg/L and <10 CFU/100 mL of E. coli) for urban reuse and initiate greywater recycling efforts by recycling low strength greywater from ablution activities and bathrooms. Last but not least, researchers and local authorities could work closely to monitor the greywater recycling systems, while the latter could provide subsidies and rebates to financially support the implementation of the greywater recycling system and eventually achieve the goal of water sustainability.