It is estimated that 380 billion m3 of wastewater is produced annually worldwide, which equals about 15% of agricultural water withdrawals. The recovery of nitrogen, phosphorus and potassium from wastewater can offset 13.4% of the global agriculture demand for these nutrients . Recycling human waste worldwide could satisfy an estimated 22% of the global demand for phosphorus . It has been estimated that some 36 million ha worldwide  reuse urban wastewater, mainly for irrigation. However, only around 15% is adequately treated , thus the need to invest in sustainable, low-cost wastewater treatment to protect public health. The irrigation potential of this volume of wastewater stands at 42 million ha. Wastewater production is expected to increase globally to 574 billion m3 by 2050, a 51% increase compared to 2015, mainly due to a growing urban population . Water reuse with treated wastewater for potable and non-potable purposes can be practised in a manner that is protective of public health and the environment . For example, when implemented with sufficient treatment standards, the use of recycled water for the irrigation of crops is protective of public health , as was determined by an appointed panel of experts in the state of California . However, there are several barriers to the adoption of wastewater reuse; these include technical barriers and public health aspects related to microbiological and pharmaceuticals risks . These are currently being addressed by strengthening regulatory standards, with, for example, 11 out of 22 Arab States adopting legislation permitting the use of treated wastewater . Benefits of wastewater reuse usually outweigh the costs .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report