To present measures to be taken by water supply utilities, both private or public, wishing to implement an direct potable reuse of water project, but in doubt of how to begin due to gaps in knowledge and uncertainty associated with the technology, including the question of (absence) of legislation and public perception and acceptance.
Lack of specific legislation for direct potable reuse; public image and acceptance; water quality; economic feasibility using affordable purified water price
From extensive references reviews and research, a total of six measures was listed to be done by water supply utilities. Since one of them is assessment of economic feasibility, we used the net present value (NPV) analysis method, for a 10 year project lifetime. For this method, it is necessary to calculate approximate cost of building and operating the plant, and we adopted purified water price same as water price in Sacramento, California. For construction cost, we used price correlations, with dimensions given by preliminary design of the plant, including ultrafiltration and reverse osmosis systems, ultraviolet reactor, tanks for storage and process pumps. For operating cost, we calculated on a year basis cost of labor, maintenance, replacing equipment, insurance and chemicals.
The six measures are: (1) assemble a specific team; (2) identify requirements and limitations of legislation; (3)choose the technology train for treatment of wastewater and purification of water, considering the water quality requirements; (4) list actions that can be done to improve public acceptance before the project goes any further, and ways of monitoring public response (5) analyze the economic feasibility (6) establish a schedule and final recommendation: whether it is feasible or not to move on with the project. For example, whether legislation or public acceptance may become such problem that can forbid the project of moving on.
In the paper, each measure will be detailed and discussed. We can anticipate that the project is not economically feasible for water price in Sacramento, California (U$0.99/100cubic feet). It would be necessary water price to be U$2.1/100 cubic feet, for design flows of at least 15 million gallons per day.
Water scarcity is an emerging challenge; pollution, unsustainable management and emerging concern of how climate change will affect the water resources increase pressure on local drinking water supplies. Direct potable reuse is one possible answer for that. In this work, by presenting DPR technology in the light of its challenges and basic economic and technical feasibility analysis, we will help shorten the gaps that are preventing this technology of getting the broad implementation it should be getting as tool to address water problems.
Two of the biggest challenges for DPR projects are the lack of legislation specifically regulating its practice and the public acceptance, which are both themes much more of in the field of policy acting than properly engineering or economics. The authors expect that, by exposing and discussing these challenges, and giving recommendations and best practices, it will help boost direct potable reuse projects.