| Abstract
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A searchable database consisting of compiled water reuse guidelines was created as a screening tool for decision-analysis for potential beneficial reuse in (1) irrigation, (2) livestock watering, (3) aquaculture, and (4) drinking (potable) water. Data compiled from literature for the four water reuses (FWR) yielded guideline values for over 50 water quality parameters, including concentrations of inorganic and organic constituents as well as general water chemistry parameters. These water quality guidelines can be used to identify constituents of concern in water, to determine levels to which constituents must be treated for water reuse applications, and to assess the suitability of treated water for reuse. In addition to water quality, water quantity was also assessed. Water volumes required for producing 16 different crops in 14 countries were estimated as an example of assessing water quantity in the decision-making process regarding potential for water reuse. Calculations were made to assist in crop planning by estimating land and water requirements for growing a specific crop in a particular country. Among the crops and countries investigated, the crops producing the highest yields in terms of weight per water volume are tomatoes in Australia, Brazil, Italy, Japan, Turkey, USA; sugar cane in Chad, India, Indonesia, Sudan; watermelons in China; lettuce in Egypt, Mexico; and onions (dry) in Russia. Water quality data from an oilfield in Africa were compared with water quality guidelines for irrigating crops and watering livestock to identify constituents of concern (COCs) in produced water. A parameter was considered a COC if its concentration was greater than guideline concentration for the specific reuse purpose. Based on the comparison, the following COCs were identified in the oilfield produced water: oil and grease, metals (Zn, Ni, Fe, Mn), F, and P. A pilot-scale constructed wetland treatment system was designed and built based on biogeochemical pathways (i.e. sorption, oxidation, reduction) required for transferring and transforming the identified COCs to achieve target concentrations that meet water quality guidelines (less than 35 mg/L oil and grease, 1 mg/L zinc, 0.01 mg/L nickel, 0.2 mg/L iron, 0.02 mg/L manganese, 1 mg/L fluoride, and 0.05 mg/L phosphorus). The system design allows parameters (i.e. hydraulic retention time and organic content of the hydrosoil) to be adjusted to promote the conditions needed to achieve maximum removal of COCs by the identified biogeochemical pathways. The pilot-scale treatment system consisted of three series of wetland cells, with four cells in each series. Two series of subsurface flow wetland cells were constructed with each cell having a two-layer hydrosoil of pea gravel and medium-sized gravel that was planted with Phragmites australis . For performance comparison, a free water surface series was constructed, with each cell containing sand hydrosoil and planted with Typha latifolia . Each series was given time for plant density and redox potential to stabilize. The data demonstrated that the system was poised to treat simulated oilfield produced water.
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