Assessment of Water Quality in the Irrigation Drainage Canals as a Source of Reusable Irrigation Water By Kai Williams, Graduate Student Civil Engineering Department New Mexico State University Faculty Advisors: A. Salim Bawazir, Associate Professor Nirmala Khandan, Professor Civil Engineering Department New Mexico State University TECHNICAL COMPLETION REPORT New Mexico WRRI Student Water Research Grant (Index #): 125248 June 2015 New Mexico Water Resources Research Institute in cooperation with the Civil Engineering Department New Mexico State University The research on which this report is based was financed by the New Mexico Water Resources Research Institute. DISCLAIMER The purpose of the Water Resources Research Institute (WRRI) technical reports is to provide a timely outlet for research results obtained on projects supported in whole or in part by the institute. Through these reports the WRRI promotes the free exchange of information and ideas and hopes to stimulate thoughtful discussions and actions that may lead to resolution of water problems. The WRRI, through peer review of draft reports, attempts to substantiate the accuracy of information contained within its reports, but the views expressed are those of the authors and do not necessarily reflect those of the WRRI or its reviewers. Contents of this publication do not necessarily reflect the views and policies of the Department of the Interior, nor does the mention of trade names or commercial products constitute their endorsement by the United States government. 2 Problem Statement Main irrigation canals in the Rincon and Mesilla Valleys were designed to convey irrigation return flow (also flood runoff at some of the locations) back to the Rio Grande River where it is mixed with the river water for downstream use. However, due to several decades of dwindling flows and in some cases no-flow in the river, the mixing of poor quality water from the irrigation drainage canals further degrades the quality of river water downstream. Research Objectives The Rio Grande River in southern New Mexico is experiencing poor mixing and degrading water quality as a result of decreased flows due to many years of drought. The objectives of this research are to a) assess water quality in the irrigation drainage canals specifically in southern Mesilla Valley for downstream irrigation reuse and b) identify pollutants and their point and non-point sources. Methodology Grab samples of irrigation drainage water were analyzed on a bi-weekly basis near and at the Sunland Park Urban Test Bed Site to assess how the water quality in the drains changed over time and geographical location (See Map, Figure 1). The water quality parameters that were tested for include Total Organic Carbon (TOC), Ammonia-Nitrogen, Chemical Oxygen Demand (COD), Escherichia coli (E. coli), anions, metals, pH, salinity, Total Dissolved Solids (TDS), and temperature. Temperature was simultaneously assessed with dissolved oxygen (DO) on site using a DO probe, and the conductivity and pH were assessed using the Hach 160 Multi-Parameter probe in the lab. Also, flowrate readings were measured at sampling point 3 (SP3) and used to estimate the flowrate throughout the Sunland Park Test Site. Grab samples for water analysis, excluding anions and metals were preserved by refrigeration. Preservation methods for anion and metal analysis of water samples will be discussed in the methodology below. 3 Figure 1. Map of Water Quality Sampling Points (SP) For Total Organic Carbon analysis, the non-purgeable organic carbon analysis procedure was used due to its wide use. Samples were put into glass vials without dilution along with 1 mgC/L and 10 mgC/L standards. Standards were prepared by accurately weighing 2.125 g of reagent grade potassium hydrogen phthalate which was dried at approximately 120 ˚C for one hour and dried in a desiccator. This was transferred to a 1 L volumetric flask and dissolved in de- ionized (DI) water. The solution was well mixed so that the final concentration was 1000 mgC/L which was further diluted to 1 mgC/L and 10 mgC/L concentrations. A lab blank was added throughout the run to prevent carryover during sample analysis. Total organic carbon analysis was conducted using the Shimadzu Total Organic Carbon Analyzer. Chemical Oxygen Demand (COD) was measured using the Hach TNTplus™ 821 Low Range kit following the US EPA Reactor Digestion Method. Samples were well mixed before 2 mL of sample were pipetted into the Hach kit vials. Vials were capped and inverted several times to mix the solution well. Afterwards, the vials were put into a 150 ˚C DRB200 Reactor for two hours and allowed to cool to 120 ˚C. Vials were inverted while still hot and placed in a rack to cool to room temperature. Vials were cleaned and then read in the Hach DR 6000 machine. Water samples were analyzed for E.coli using the IDEXX Coliert-18 Method. In this method, 100 mL of sample was placed into a plastic vessel with pre-measured sodium thiosulfate which neutralizes 15 mg/L of chlorine that could be potentially present in the sample. The sample was, then, mixed well and set aside until foaming subsided. After the foaming subsided, the sample/reagent solution was put into sterile Quanti-trays and bubbles removed from solution. The trays were sealed with the Quanti-tray sealer and then incubated for 18 hours in 35 ˚C temperature. After samples incubated for 18 hours, sample were read under a UV light in a dark viewing cabinet, compared against the IDEXX E.coli comparable, and analyzed for the number of illuminated (or E.coli positive) wells. The number of small and large illuminated wells represented the most probable number of E.coli in 100 mL (MPN/100 mL). Grab samples for anion analysis were taken in the field in 50 mL plastic vials without air to prevent volatilization of anions and prepared for analysis on the same day. Water samples were diluted with deionized (DI) water to prevent oversaturation and clogging of the ion chromatograph column. 100 μL (1000X dilution) and 1000 μL (10X dilution) were inserted into 4 two separate 10 mL volumetric flasks, and the rest of the volume was filled with DI water. After dilution samples were put into plastic polyvials while preventing air from being in the vial and capped with a filter cap. Dilutions ensured that accurate data is acquired for, both, analytes of low and high concentration. Calibration standards were prepared with a concentrated IC standard (phosphate, sulfate, bromide, nitrite, nitrate, chloride, and fluoride) which was diluted to the concentrations shown in Table 1. Specific standard anion analyte concentrations are in Appendix B. Matrix spikes were prepared by mixing 10 mL of diluted sample of choice and standard to compare the method sensitivity and accuracy. To ensure that anion peaks were separated in the IC program, 20 mg/L sulfate and 4 mg/L carbonate samples were prepared separately. Samples were then put into the Dionex ICS-2100 RFIC to be analyzed. Table 1. Anion Standard Preparation Standard Amount D.I. Water Amount Final Concentration (mL) (mL) (mg/L) Standard 1 0.1 9.9 1.50 Standard 2 0.2 9.8 3.00 Standard 3 0.4 9.6 6.00 Standard 4 1.0 9.0 15.0 Standard 5 2.5 7.5 37.5 Standard 6 5.0 5.0 75.0 Grab samples taken in 50 mL plastic vials from the field were preserved with trace metal grade nitric acid to bring the pH of the sample to pH 2 for metal analysis following EPA Method 200.8. Samples were prepared in the lab by diluting the sample with 1% nitric acid (99% DI) solution to prepare 10X and 1000X dilutions. Samples were diluted in 50 mL plastic vials, and then 385 μL of the sample was taken out of that vial so that 385 μL of internal standard dilution could be added without changing the total volume of the sample solution. Internal standard dilution was made by taking 1 mL of 10 μg/mL internal standard (Bismuth, Indium, Lithium 6, Scandium, Terbium, and Yttrium) and bringing the total volume up to 10 mL with the 1% nitric acid solution mentioned previously. Then, external standards with different analytes and concentrations (Appendix A) were prepared as seen in Table 2. Two different external standards were used to prepare the calibration standards due to the wide range of metal analytes targeted. Then, 385 μL of the internal standard dilution was added to the prepared standards to keep the same concentration of internal standard as in the water samples. Samples were analyzed using the Perkin Elmer Sciex Induced Coupled Plasma-Mass Spectrometer. 5 Table 2. Metal External Standard Preparation 10 μg/mL 1 μg/mL 1% Nitric Final Standard Standard Acid Concentration Standard 1 0.01 0.1 99.89 1.50 Standard 2 0.10 1.0 98.90 3.00 Standard 3 1.00 10 89.00 6.00 Standard 4 5.00 0.0 95.00 15.0 Standard 5 10.0 0.0 90.00 37.5 Results and Recommendations Comparing the changes in anion concentration over time in Sampling Point 3 (SP3), 5 (SP5), and 7 (SP7) (Figure 2 and Figure 3) show that chloride, sulfate, and fluoride concentrations were relatively consistent throughout the research period. Sulfate and chloride anions were the highest among the other anion fluoride, nitrite, nitrate, and bromide. However, nitrite, nitrate, and bromide concentrations were too low in concentration for the anion analysis software to register. In addition, higher concentrations of sulfate and chloride were observed in SP3 than in SP5 and SP7. 1000 12/5/2014 12/15/2014 1/14/2015 1/30/2015 2/16/2015 3/2/2015 900 3/16/2015 3/30/2015 4/13/2015 5/11/2015 5/26/2015 6/22/2015 800 700 600 500 400 300 Concentration (mg/L) Concentration 200 100 0 SP3 SP5 SP7 SP3 SP5 SP7 Chloride Sulfate Figure 2.