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.
This study evaluates the potential of implementing rainwater harvesting (RWH) as an alternate source of water, capable of meeting the domestic outdoor demand, for dry and wet regions of the United States. As the representatives of dry and wet regions, the states of Arizona and Florida were selected, respectively. An interactive system dynamics model was developed using Stella that considered historical rainfall amount, population growth, outdoor water demand, number of households, and different climate scenarios as the predictors of the model. Monthly rainfall data for 10 years i.e., 2005 to 2014 were used and dataset was projected for the upcoming 10 years using the near term climate projections from US Environmental Protection Agency. The model results were used to compare the domestic outdoor demand and the amount of water that can be generated using RWH for the upcoming years. The user of the model had control over two different sets of parameters. The first set, known as the primary set, included percentage of per capita water used for outdoor water demand, percentage of existing households with RWH, percentage of future households (to be built) with RWH, and percentage of population using desert landscaping. The desert landscaping parameter was introduced to supplement the reduction of outdoor water use in arid areas. The second set of parameters, known as the secondary set, included capture ratio of the roof (depends on the roof material), reduction factor due to the effect of antecedent dry period, and parameters of the governing equation. Both primary and secondary set of parameters allowed the user to perform sensitivity analyses and evaluate different scenarios. The results indicated that for wet regions, such as the state of Florida, RWH was already a viable option. In fact, for such regions, advanced cisterns with water treatment facilities can be used to meet some indoor water demand as well, since there would be excess after using for outdoor purposes. For dry states, such as Arizona, to make RWH a feasible option, all the parameters of the primary set need to be adjusted. To store the water generated from RWH, a 50-gallon rainwater barrel was selected, which was found to be capable of storing 42% of the water generated from a typical household rooftop for the state of Arizona. The study presented an “achievable scenario”, with adjustments of the parameters from the primary set, which showed potential of meeting 60% of the total domestic outdoor demand for the state of Arizona. The results indicated that RWH could be a feasible option even for some dry states with limited rainfall. This model allows the water managers to test different assumption and evaluate the potential of RWH under multiple climate scenarios.
The use of treated, partially treated or untreated wastewater in agriculture has, both historically and contemporarily, been a common practice around the world. In Egypt, agricultural drainage accounts for the greatest quantity of wastewater utilized in agricultural production. Other sources include effluent from industries and output from wastewater treatment facilities. This mixed drain water is pumped and used for irrigating crops, often in large volume, and particularly in times of water shortage within fresh water irrigation canals. While the practice offers farmers some benefits including continuous supply of water, savings in fertilizer application, and increase in production, it also has the potential to inflict harm on both human and environmental health. This paper assesses farmers’ current practices, their perceptions, as well as the benefits and costs (human health, economic, and environmental) of using untreated or partially treated wastewater in agricultural production. The study was carried out in El Hussainiya district of Sharkia Governorate. Data collection was carried out through the administration of a questionnaire to 120 households and focus group discussions in three villages. Analyses of collected data exposes several challenges in the current practice but also identifies potentials to increase overall agricultural water availability in the area. The paper thus offers specific policy recommendations to promote safe use of wastewater to supplement the ever growing demand for water in the agricultural sector.
Currently, over 700 million people do not have access to sufficient supplies of clean water. Many regions suffer severe water stress, i.e. draw on 80% or more of their renewable water resources. About 44% of the world population live within a 150 km wide shoreline belt susceptible to flooding by the encroaching ocean and sea water intrusion into the groundwater resources. Global recharge of the fresh water resources is a finite quantity originating from the unevenly distributed atmospheric precipitation and is vulnerable to the climatic changes. For example, countries in the Middle East and North African region receive as little as 1% of the world’s precipitation of which 85% is lost through evaporation. World Resources Institute predicts that by the year 2040 at least 33 countries will endure acute to severe water stress. Time honored practice of carrying water from distant “water-rich” and less populated regions via costly aqueducts, canals, pipelines etc. to water-thirsty regions has been proven not a solution, but only a temporary remedy as recently demonstrated by the California drought.
Israel, located in one of the most water-stressed regions of the world has recently demonstrated a long-term, if not permanent solution to its water scarcity. Until about 2010 Israel was rapidly depleting all renewable water resources. It was clearly losing the battle with the sea water intrusion into the coastal aquifer. The glorified 130 km long National Water Carrier added less than 500 million cubic meters of water a year – less than a third of Israel’s water usage at the time of its peak performance – causing lateral environmental and political damages, e.g. a drastic fall in the level of Lake Tiberias (The Sea of Gallilee), that in turn caused increased inflow of saline springs through the Lake bottom, causing rise in lake water salinity; decline in the flow rates and increase in salinity of the lower Jordan River; the enormous damage to the Dead Sea due to the vast decrease in the amount of water entering it from the Jordan River and, last but not least, the conflict with Syria and Jordan over water.
The Israeli solution consists of the water triad: desalination, recycling and optimization of the irrigation methods. Sixty percent of the Israeli agricultural land is irrigated by highly efficient drip irrigation. Israel produces 500 million cubic meters of wastewater every year, more than 90% of which reaches the various treatment plants. Currently, Israel utilizes 85.6% of the wastewater it processes (highest in the world, compared to the second-highest 12% in Spain, 9% in Australia, 5% in the USA and 1% in Europe). Israel’s desalination capacity has currently reached 560 million m3/year with some of the world’s largest sea water reverse osmosis facilities, lowest costs (less than $0.40/m3) and numerous innovations. The Israeli water triad should be considered a valid pilot project, particularly for the countries located within the areas characterized by high water stress index.
In the United States, desalination has considerably expanded since the 1950s, reaching a daily production capacity of 2 BGD (billion gallons per day) with around 1,336 operating plants as of 2013 (GWI, 2013). The steady increase in the number of new desalination plants online as well as the production capacity in the US indicates long-term trends in the desalination sector (Gasson, 2013). Despite this continuous growth, a steady increase in desalination investments and growing demand for water, in many regions, the costs of desalination are still prohibitive for its quick uptake. At the same time, the technology offers a tremendous potential for ‘enormous supply expansion that exceeds all likely demands’ (Chowdhury et al., 2013). Moreover, research on long-term desalination trends, socio-economic impacts and potentials for additional water supply is still limited, mainly due to data paucity and a regional differentiation of the desalination plants in the US.
This paper provides answers to those questions by developing interactive geospatial models and a multi-dimensional analysis of desalination trends in the time span 1950-2013. The analysis is based on data from Global Water Intelligence (GWI, 2013). The models use the Keyhole Markup Language (KML) and the C++ computing language to represent desalination trends over time and space in virtual globes environment. Thus, the results of the analysis and the models themselves can be viewed in any virtual globe (e.g., Google Earth, Google Maps, ArcGIS).
The analysis shows that more than 90% of all the plants in the US are small-scale plants with the capacity below 4.31 MGD. Most of the plants (and especially larger plants with the capacity above 4.31 MGD – million gallons per day) are located on the US East Coast, as well as in California, Texas, Oklahoma, and Florida. Some larger plants are also present inland in Illinois and Colorado. The vast majority of plants in the country operate with a capacity in the range between 0.31 MGD and 1.80 MGD. Despite the geographical proximity to the sea, most of the plants use brackish groundwater due to economic factors related to the desalination process itself and the disposal of the highly saline byproduct - brine. The models provide information about economic feasibility of a potential new plant based on the access to feed water, energy sources, water demand, and experiences of other plants in that region. The models also evaluate correlations between population density and the developments of desalination plants in different US regions, which directly determines the necessity for a reliable water supply.
The analysis and models can be used both for educational and interdisciplinary research purposes and help with determining socio-economic viability of establishing prospective desalination plants in different regions in the future. They can also help support decision makers in solving emergency questions related to water shortages and preparing for long-term water scarcity in different regions.