Review of the greywater and proposed greywater recycling scheme for agricultural irrigation reuses

In this study, we reviewed greywater characteristics and various treatment technologies with the aim of coming up with the schematic of greywater recycling system designed specifically for restricted agricultural irrigation reuse. Characteristics of greywater are highly variable; greywater amount varies from 50% to 80% of the wastewater volume produced by households. All types of greywater show good biodegradability in terms of COD: BOD5 ratios. The ratio of BOD5/COD in greywater ranged from 0.31 to 0.71. Most countries apply the same standards to reclaimed municipal wastewater as they do to greywater. However, some countries have established specialized standards for greywater reuse. Technologies used for greywater treatment are classified into physical, chemical, biological, and natural systems, or a combination of these. Using physical greywater treatment processes solely as the main treatment method is insufficient for greywater treatment, chemical greywater treatment processes are attractive for single household low-strength greywater treatment systems, as the variability in the strength and flow of the greywater did not affect their treatment performance. Constructed wetland can be regarded as the most environmentally friendly and cost-effective technology for greywater treatment and reuses. Finally, the study suggests the possible greywater recycling scheme for agricultural irrigation reuse purposes.