Of the planet’s water, only 1% is available as freshwater. Demand is steadily outpacing supply and is projected to do so by 40% by 2040. Drivers including population growth, pollution, land subsidence and seawater intrusion of aquifers are forcing people to consider the sustainability of their water supplies – it is not a guarantee anymore. One of the biggest untapped opportunities to alleviate water stress is the recycling of wastewater to augment freshwater supplies.
Water recycling is a continuum – as the amount of time between wastewater treatment and the inevitable human consumption gets progressively shorter, more advanced treatment and monitoring of water quality is required. The continuum (Figure 1) moves from treating wastewater for pollution abatement purposes, to non-potable reuse such as agricultural or industrial purposes, to freshwater augmentation, where treated recycled water is used to recharge aquifers and reservoirs, or even more directly, through an engineered buffer to a drinking water facility to augment raw or treated water.
Reverse osmosis (RO) is commonly used in advanced reuse flowsheets for its ability to remove pathogens, nutrients, trace chemicals of concern and dissolved salts. Electrodialysis reversal can be used to remove these salts as well.
Ozone and UV are used in flowsheets for the disinfection of pathogens and can be used in advanced oxidation operations as well to provide high amounts of pathogen removal as well as destruction of certain chemical constituents of concern.
Specific drivers within a community determine the water recycling needs and technologies required. It is important to consider that decisions made today can prepare the foundation for a more advanced recycling program in the future as community needs evolve. For example, incorporating membrane technologies as the basis for treatment and non-potable recycling programs can provide a strong backbone to build on with advanced treatment steps as evolving community and environmental drivers move the recycling needs further along the continuum.
With the right combination of technologies for the given application, water recycling produces the water quality needed to protect public health, satisfy regulatory needs, and ensure a sustainable freshwater supply for generations to come.
