It has been demonstrated that existing technologies for advanced water treatment can successfully upgrade wastewater to drinking water quality in large scale. There are installation for water reuse/water reclaim in California that are treating municipal wastewater to drinking water quality in volumes over 70 MGD.
These technologies employed include membrane filtration, RO, UV and ozone. Despite the technology there are a number of barriers from keeping this from happening. The first issue is that while water resources are being depleted and lower quality sources are increasingly being used, most of the US has ample supplies of water. Second, advanced treatment technologies cost more money that conventional treatment technologies. Simply put, treating dirtier water with higher technology costs more. It is difficult to justify diversifying the water resource given the higher costs.
However, even in areas where water is scarce and governments are interested in exploring new approaches, there are challenges. Schemes for water reuse up till now have used indirect water reuse for potable water. Wastewater is treated and then injected into the ground for later use. Direct reuse, connecting the sewage plant to the drinking water plant is creates the “yuck” factor. People are more comfortable with the water passing through the environment prior to going directly from wastewater treatment to drinking water treatment.
Even if the “yuck” factor is overcome, there is a regulatory gap that needs to be addressed. There are no federal regulations in place covering this area, thus no guidance to the states. California, the most advanced in this area, hopes to have regulations in place by 2016. Many states just have guidelines. Without clear rules, it is difficult for planners and governments to decide how to proceed.
Finally, there is no one solution for all locations. RO systems for example produce concentrated waste streams that need to be disposed of. Some location have the ability to do so economically and other do not. So, solutions have to be crafted for each location and water source. This involves engineering that adds to the cost and complexity of each project.
In all likelihood, it will take many years for direct reuse of reclaimed water for direct potable use to become a mainstream application. Nonetheless, many intermediate projects are moving forward to increase the overall supply of clean water.