Experiment 10 Lab Report: Wastewater TreatmentJennifer Lipton Lab Partner: James LaMarca Chem 113E TA: Lisa Funari 3/27/14 2 Introduction: Throughout time, water treatment and sanitation has been an area marked by important development. Even today, identification of water containments and remediation techniques are important in ensuring that the water we ultimately drink is clean. This empirical study sought to identify different types of water contaminants and ways in which to lower the concentration of these impurities. By obtaining a better understanding of wastewater and what qualities a water sample possesses, it is possible to determine from where and in what way contaminants enter a water supply. The streams in Pennsylvania get a large portion of their flow from groundwater. Prior to reaching streams, groundwater can pick up waste from agricultural lands, sewage, and mine runoff. 1 Possible contaminants from these sources observed in this study are heavy metals, excess hardness, excess acidity, and organic contaminants. Groundwater flow thus deposits these impurities into the water supplies of the state. If proper treatment were not employed, then the drinking water of Pennsylvania would not meet health standards. The goal of this study was to determine which two of the four main contaminants were present in an assigned water sample. After determining which contaminants were present, the proper remediation techniques then had to be employed until the sample had an observable decrease in contaminant levels. In order to determine what was present in the sample, it was necessary to know how to use and understand the results of Atomic Absorption Spectroscopy, Spec 20, and litmus paper. Knowledge of activated carbon, 3 limestone, and ion exchange resin and how they react with different contaminants was important in the remediation process of the water samples. When discussing water quality, a water sample is considered “hard” when there is an excess amount of dissolved minerals such as calcium and magnesium. Water is a good solvent for these minerals so water readily dissolves calcium and magnesium as it flows through soil and rock. The effects water hardness has can be quite troublesome. Water hardness contributes to mineral buildup on pipes and other plumbing fixtures. Excess hardness in water supplies can decrease the ability for soaps and detergents to clean as well as lower the efficiency of water heaters. Significant concentrations of calcium and magnesium in water supplies can have many bothersome affects and thus must be remediated. 2 Excess acidity is another major contaminant present in water supplies. Some sources of acidic water are acid rainfall due to atmospheric pollutants and runoff from mining spoils. 3 The major health concerns of acidic water are indirect. When acidic water flows through pipelines, it can corrode metals such as copper and lead. If copper is digested for a long period of time, it can lead to liver or kidney damage. Although not as serious, direct effects of water acidity are redness and irritation to the eyes and skin. 4 Iron can become present in water supplies through the process of rainwater seeping through iron rich soil and rock. Corrosion of water pipes is also a common source of excess iron in water. Iron presence in water can cause problems by clogging wells, pipes, and pumps. Damages done to devices such as dishwasher can lead to costly repairs. Iron can also give a metallic taste to the water as well as effecting food preparation. 5 4 Organic contaminants are another class of water impurities that enter water supplies through herbicide runoff, discharge from chemical and agricultural factories, and runoff from landfills. The health effects of organic contaminants can be severe and include damage to organs, increased risk of cancer, and problems with blood flow. Acid orange is just one of many organic contaminants that can effect water quality. Without proper remediation techniques, the aforementioned water contaminants would have long lasting effects and create low quality and unhealthy drinking water. 6 An understanding of how wastewater enters our water supplies and techniques to remediate samples is paramount to the quality of drinking water. The learning objective of this study was not only to determine what contaminants were present in a water sample and how to remediate them, but also to be able to determine where a water sample came from based on observed results. The techniques and skills learned in this study can be employed on a large-scale basis to observe and treat large water supplies in the environment. Procedure: Water sample number six was assigned and an antiquate amount of the sample was collected to use throughout the experiment. First, a test for water hardness was conducted. A pure sample of water sample number six along with samples that were 50% and 75% diluted with distilled water were collected into beakers. The samples were than run through the Atomic Absorption Spectrometer using the proper techniques used to test for the presence of Ca 2+ and Mg 2+ . To test the acidity of the water sample, pH paper was 5 dipped into the sample. The color change of the pH paper was than compared to the pH color scale give on the paper container. A test for the presence of Fe 2+ was than conducted using a Spec 20 at a wavelength of 562 nm. First, standard values were collected by setting up cuvettes for a blank, 0.5 ppm, 1.0 ppm, 1.5 ppm, and 2.0 ppm samples of iron. The samples were than mixed with ferrozine and pH 5.5 buffer. Based on the transmittance percentage values obtained from these samples, the absorbance values were calculated. Water samples number six was than run through the spec 20 to compare against the standard values. Using a wavelength of 425 nm, the spec 20 was used to test for the presence of acid orange. Cuvettes were filled with a blank and water sample number six. The transmittance value of the unknown sample was than compared to that of the blank. Given that the contaminants of water sample six were excess iron and acidity, proper remediation techniques were implemented. In order to remove the excess iron, ion-exchange resin was used. The resin was mixed into a small sample of the unknown and a hot plate was used to speed up the reaction. After the ion-exchange resin fully reacted with the sample, the sample was retested for the presence of iron using the spec 20 at a wavelength of 562 nm. Using the new transmittance value, the absorbance and iron concentration of the sample were recalculated. After the concentration of iron was reduced, limestone was added to decrease the acidity of the sample. The calcium carbonate of the limestone reacted with the water sample to turn the water from acidic to basic. Again, a hot plate was used to increase the rate of the reaction. After the reaction ran to completion, the acidity of water sample six 6 was retested using the pH paper. Once both remediation techniques were applied and the water sample was purified, proper clean up procedure followed. Results Table 1 shows the results obtained from the atomic absorption spectrometer. Based upon the absorbance values and the standards of figure 1, the concentrations for both Mg 2+ and Ca 2+ are less than 1 ppm. The results of the AA test suggest that the excess hardness was not one of the two contaminants present in water sample six. Table 1: Atomic Absorption Spectrophotometry Results for Mg 2+ and Ca 2+ Absorbance Values Concentration (ppm) Mg 2+ 0.0019 <1 Ca 2+ 0.0028 <1 Figure 1: Atomic Absorbance Standards for determining the concentration of Ca 2+ and Mg 2+ During the test for acidity, when the pH paper was dipped into water sample six it turned a pink color. Based upon the pH color scale on the container of the pH paper, a 7 pink color indicates a pH between one and two. Such a low pH suggests that excess acidity was one of the two contaminants present in water sample six. Table two contains the results from the spec 20 test for excess Fe 2+ of the unknown sample along with the standard samples. After obtaining the transmittance percentage values, the absorbance values were calculated. A sample calculation for absorbance is shown below table 2. Based upon the results, unknown sample six had an iron concentration between 1.0 and 1.5 ppm. This suggests that excess Fe 2+ was one of the two contaminants in the water sample. A calibration curve of absorbance values versus concentration was than constructed in Graph 1 based upon the standard values. Using the equation of the best-fit line of graph 1, the concentration of iron in the unknown sample was calculated. This equation is listed below graph 1. Table 2: Spec 20 results for Fe 2+ determination Transmittance % Absorbance Blank 100 0 Unknown Sample Six 53 0.276 0.5 ppm 93 0.034 1.0 ppm 71 0.149 1.5 ppm 50 0.301 2.0 ppm 38 0.420 Sample absorbance calculation using transmittance value: Absorbance = -log( For 0.5 ppm: Absorbance = -log( ) = 0.034 8 Sample calculation of iron concentration of unknown sample using the equation of the line in graph 1: y=0.262x-0.1015, where y is equal to the absorbance value and x is equal to the iron concentration in ppm 0.276=0.262x-0.1015 x=1.44 ppm The concentration of Fe 2+ in water sample six was 1.44 ppm. Table 3 contains the results of the spec 20 test for acid orange. Using the equation from table 2, the absorbance value was calculated from the transmittance value. Based upon the results, there was no significant different of absorbance between the blank solution and the unknown water sample. These results suggest that acid orange was not one of the two contaminants present in water sample six. Table 3: Results from spec 20 test for acid orange Transmittance % Absorbance Blank 100 0 Unknown Sample 100 0 After using the ion-exchange resin method to remediate the excess iron present in the water sample, the sample was retested using the spec 20. The new transmittance value y = 0.262x - 0.1015 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0 0.5 1 1.5 2 2.5 A b s o r b a n c e Concentration of Iron (ppm) Graph 1: Calibration Curve of Absorbance vs. Concentration of iron (ppm) 9 after remediation was 20%. Using the absorbance calculation from table 2, the new absorbance value was calculated to be 0.097. Using the equation of the line of graph 1, the new iron concentration in the sample was calculated to be 0.76 ppm. This significant decrease in Fe 2+ concentration indicated that the ion-exchange resin method worked as a remediation technique. After using limestone to decrease the acidity of the water sample, pH paper was used to retest the sample. This time, the pH paper turned green instead of pink. Based on the pH color scale on the container of the pH paper, a green color indicates a pH of eight. This high pH suggests that the water sample went from very acidic to very basic. The major change in acidity indicated that the limestone worked as a remediation technique for excess acidity in water. Discussion: The results of this study suggested that excess iron and acidity were the two contaminants of water sample six. In atomic absorption spectrometry, emission spectrum of a specific element is produced. The sample being tested then absorbs the radiation of the element in question. If the reduction in radiation produced measured by the AA spectrometer is low, than the concentration of the element being tested for is low. 7 In the study conducted, the absorbance values for both Ca 2+ and Mg 2+ were significantly low. This indicated that these elements were not present in any significant amount in the sample and thus could not absorb a great amount of the radiation being emitted. When water sample six was tested with pH paper, it turned a pink color. In general, samples with low pHs turn pH paper pink while samples with high pHs turn the 10 paper green. The pink color of the pH paper indicated a pH of between one and two. The lower the pH of the sample, the more acidic that sample is. Water sample six caused the pink color change of the pH paper due to its high acidity. A spec 20 works by measuring the amount of light that passes through a sample. Transmission is the amount of light that passes through the sample while absorbance is the amount of light the solution absorbs. When set to the wavelength that corresponds to the element of interest, the absorbance values will increase with the concentration of that element in the sample. 8 The absorbance value obtained from water sample six when testing for the presence of Fe 2+ was 0.276. This implied that there was enough iron for the sample to absorb a significant amount of the light that was shone through it. The calculated concentration of the iron present was 1.44 ppm. According to the United States Environmental Protection Agency (EPA), the standards for safe drinking water are 0.3ppm iron 5 . The concentration of iron in water sample six is significantly greater than the safe drinking water standards and suggests that excess iron was one of the two contaminants found in the sample. The spec 20 test used to determine the concentration of acid orange worked in the same way it did for the Fe 2+ test. The only difference was that the spec 20 was set to a wavelength that corresponded with acid orange rather than iron. When tested for acid orange, the absorbance value of water sample six remained around zero as it did when a blank solution was tested. This indicated that there was no acid orange to absorb the light being shone through the water sample. Ion-exchange resin and limestone were chosen as the remediation techniques to purify water sample six. Ion-exchange resin works to remove unwanted metals from 11 solution due to its high attraction towards the metal ions. The resin beads thus retain the metal ions and release H + and OH - , creating water. When the water sample was retested using the spec 20 after the ion-exchange resin was used, the new absorbance value was 0.097. Using this new absorbance, the iron concentration was calculated to be 0.76 ppm. This value is a lot closer to the safe drinking water standard of 0.3 ppm than the original concentration of 1.44 ppm prior to remediation. Due to the calcium carbonate present in limestone, it was used to remediate the excess acidity in water sample six. During this reaction, the H + ions in the acid react with the calcium carbonate to produce hydrogen carbonate. This causes the limestone to dissolve and the pH of the water sample to be neutralized. After reacting limestone with water sample six, the sample was retested using pH paper. This time, the paper changed to a green color indicating a pH of 8. The significant increase in pH suggests that the limestone worked to turn water sample six from acidic to basic. Conclusion: During this study, different techniques on identifying contaminants in a water sample and remediating those contaminants were employed. Using atomic absorption spectrometry, spec 20 machines, and pH paper, the contaminants present found in water sample six were documented to be excess iron and acidity. Using the techniques of ion- exchange resin and limestone, the contaminated water sample was properly remediated to be closer to safe drinking water standards. Water quality control is vital to our health as well as daily tasks such as cleaning and doing laundry. Water hardness, acidity, metal concentration, and organic contaminant concentration are important to monitor and remediate if they rise to a dangerous level. 12 Knowing remediation techniques such as ion-exchange resin as well as limestone can be important in aiding in the purification of water sources. Identifying what contaminants are present allows the deduction of where the water sample came from and why the contaminants are present. Locating where water contaminants come from is the first step in remediating the contaminated water samples. 13 Works Cited [1] – Dong, J. et. al. Chemistry 113E Laboratory Manual, spring 2014; Hayden-McNeil a Publishing: Plymouth, MI, 2014; Apendix A pp. 2- [2] – "Wellcare Information for You About Hardness in Drinking Water."Watersystemcouncil.org. Environmental Protection Agency, n.d. Web. 20 Mar. 2014. <http://www.watersystemscouncil.org/VAiWebDocs/WSCDocs/1683274HARDNESS.P DF>. [3] – "Raleigh Plumbers Blog." Raleigh Plumbers Blog. N.p., n.d. Web. 20 Mar. 2014. <http://raleighplumberplus.com/raleighplumber/water-acidity-and-your-health- easywater/>. [4] – "Acid Water Conditions on Residential Water Wells." Acid Water Conditions on Residential Water Wells. N.p., n.d. Web. 22 Mar. 2014. <http://www.advanced-water- systems.com/technical/guides/tech_acid_water.html>. [5] – "Minnesota Department of Health." Iron in Well Water. N.p., n.d. Web. 20 Mar. 2014. <http://www.health.state.mn.us/divs/eh/wells/waterquality/iron.html>. [6] – "Drinking Water Contaminants." Home. N.p., n.d. Web. 20 Mar. 2014. <http://water.epa.gov/drink/contaminants/>. [7] – "Atomic Absorption Spectroscopy - Springer." Atomic Absorption Spectroscopy - Springer. N.p., 01 Nov. 1968. Web. 20 Mar. 2014. <http://link.springer.com/article/10.1007/BF02631956#page-1>. [8] – "Spec 20 Instructions." Spec 20 Instructions. N.p., n.d. Web. 20 Mar. 2014. <http://academics.wellesley.edu/Biology/Concepts/Html/spec20instructions.html>. 14