**4. Conclusions**

The deficiency of water supply is considered a global issue and in the near future (2030; 160% of currently available resources) should be provided to overcome this threat. In the present chapter, we have discussed both treatment technologies and guidelines set for water reuse that may be considered one of the available solutions presented to overcome the future water crisis. The treatment technologies are divided into three main categories including pretreatment, PT, ST, and TT based on the main endeavors suggested for water reuse. The PT can reduce 30–40% of the organic load and pathogens, accordingly, it may be exploited to provide water for the controlled irrigation of forestland and parks, as long as the safety precautions are fulfilled. The ST is capable of reducing the organic load and pathogens by ~95% and provides disinfection in some cases. The ST is suitable water for the irrigation of trees (e.g., olive orchards and vineyards), as long as there is no direct contact with the crops. Lastly, The TT may be convenient for all types of edible crops owing to it being fully capable of reducing the organic load by 99%, and UV disinfection completely removes the pathogens. The standard guideline for the application of water reuse at a global scale is unavailable, whereas, several guidelines for water reuse were discussed in the present chapter including FAO, WHO, USEPA, FDA, State-level guidelines in the United States, Europe guidelines, and Egypt.
