Final Report: Novel Natural Water Filters for Nagcarlan, PhilippinesEPA Grant Number: SU834743
Title: Novel Natural Water Filters for Nagcarlan, Philippines
Investigators: Abulencia, James Patrick , Gallardo, Susan , O’Brien, Shannon , Tanala, Francis Narvin
Institution: Manhattan College , De La Salle University-Manila
EPA Project Officer: Nolt-Helms, Cynthia
Project Period: August 15, 2010 through August 14, 2011
Project Amount: $9,900
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2010) RFA Text | Recipients Lists
Research Category: P3 Challenge Area - Water , Pollution Prevention/Sustainable Development , P3 Awards , Sustainability
The proposed project of the Manhattan College and De La Salle University Research Team is to create a personal water purification solution for the citizens of the Philippines that effectively treats contaminated water, yet is also simple, low cost, and sustainable. The main objective of the research team is to help decrease the incidence of waterborne diseases through the design and manufacture a recyclable personal water purification device constructed from indigenous natural resources. The filter is designed to perform the following functions: remove heavy metals and pesticides (e.g. methomyl), and disinfect.
Activated Carbon Characterization - FTIR Results
The functional groups present at the surface of the activated carbon were determined through Fourier Transform Infrared (FTIR) Spectroscopy using Thermo-Nicolet 6700 Magna-IR Spectrometer. Figure 1 shows the FTIR spectra of the original AC sample. The spectral peaks indicate the presence of surface phenol groups because it both contains both aromatic and alcohol stretching vibrations. Preliminary experiments have also been performed on thermallytreated AC under both nitrogen and hydrogen atmospheres (data not shown). The results have supported the spectra of the untreated AC, but additional experiments will be performed to confirm this.
Figure 1: FTIR Spectra for the Original AC Samples
Figure 2: Results of pH Drift Tests for Original AC Samples
Activated Carbon Characterization - PZC Results
The pH drift test was conducted in order to determine its point of zero charge. This is important in adsorption because it will have a bearing on the interaction between the adsorbate and the surface of the adsorbent, especially in aqueous-phase adsorption. In Figure 2, the intersection of the data with the diagonal is the pH value of the point of zero charge. Taken together, the average value of pHPZC of the AC sample was calculated to be 7.875.
Correlating the results of the pH drift tests and FTIR analysis, the reduction of the O–H stretching vibration band (between 3600 cm-1 and 3100 cm-1) when thermally treating AC under nitrogen suggests the presence of surface hydroxyl groups. This means that the results of FTIR analysis are consistent with that of pH drift tests, indicating that the surface is basic.
Adsorption Studies - Hexavalent Chromium Removal Results - Adsorbent Dosage Analysis
Batch testing methods were employed to analyze the effect of adsorbent dosage on hexavalent chromium removal. The purpose of this part of the investigation was to obtain an optimal carbon dosage in which contaminant removal per mass of activated carbon was maximized. Figure 3 demonstrates that with an adsorbent dosage of 0.9 grams per 100 mL solution, a removal efficiency of 30% can be attained. However, it appears that the optimal range for the adsorbent dose per 100 mL of solution is between 0.5 and 0.9 grams. This range of carbon dosage results in 28-30% removal of chromium.
Figure 3: Batch Test Results on Effect of Adsorbent Dosage
Figure 4: Continuous Test Results on the Effect of Contact Time
Adsorption Studies - Hexavalent Chromium Removal Results - Contact Time Analysis
Continuous column testing methods were utilized to investigate the effect of contact time on hexavalent chromium removal. A series of rapid small-scale column tests (RSSCT) were used to analyze and obtain the breakthrough curve for the adsorption process of hexavalent chromium on coconut shell derived AC.
Figure 4 illustrates the effect of contact time on the removal of hexavalent chromium using coconut shell derived AC. As shown, the percent removal of hexavalent chromium decreases with an increase in contact time. The percent removal is much greater at lower contact times because the activated carbon has uninhabited pore sites and much more surface area for adsorption. However, as contact time increases, the availability of these active pore sites diminishes as more and more of the pore sites are occupied by the hexavalent chromium from the aqueous solution.
The tepid result obtained may be attributed to the natural pH of this solution (pH = 5.1). More specifically, the solution was run at pH < pHPZC, which means that the surface charge is positive, and will attract more negatively-charged adsorbates. Because hexavalent chromium is positively charged, there will be a low affinity between the AC surface with the adsorbate. These results are consistent with the results suggested by the PZC. Additional experiments will be conducted to evaluate the efficacy of hexavalent chromium removal at a pH > pHPZC.
Adsorption Studies - Methomyl Removal Results
The effect of adsorbent dosage on methomyl removal was also determined using batch adsorption. The particle size of AC used was 0.5-0.6 mm. The initial concentration of the methomyl solution was maintained at a constant value of 100 mg/L. This was based on the pesticide concentration actually used by the farmers on crop application. The method of analysis uses HPLC, and is adopted from the protocol from Chang et al. (2008).
Figure 5: Effect of Adsorbent Dosage on Methomyl Removal
Figure 5 shows the results of the batch adsorption tests in determining the effect of adsorbent dosage on methomyl removal. As can be seen, approximately 76% removal was achieved when using 600 mg of AC. Moreover, it can be seen that higher adsorbent dosage would mean a higher percent removal for methomyl. The relationship between the adsorbent dosage and percent methomyl removal can be observed to be linear and directly proportional. It can be recommended that the adsorbent dosage can be increased in order to achieve 100 percent removal of methomyl. The adsorption percentage achieved when using marine sediments was only 2% for an equilibrium time of 10 hours (Yang et al., 2005). This means that the activated carbon sample used for the adsorption of methomyl is a better adsorbent than marine sediments.
Preliminary experiments testsed citricidal (i.e. Vitamin D Extract) and lemon juice as candidate natural disinfectants for the filter. Citricidal demonstrated a greater efficacy, and was chosen for further study (data not shown). Subsequent experiments were conducted using citricidal powder using the aforementioned rapid small scale column testing apparatus in the hexavalent chromium adsorption study. Powder was selected because it is desired to employ citricidal in-situ with coconut shell derived AC, which is granular in form as well. In this approach, both citricidal and activated carbon can be combined together in one column to remove contaminants in a single step with only one device.
In order to analyze the inhibition activity of citricidal and to determine proper scale-up for larger volumes of water, a breakthrough curve was generated. As shown in Figure 6, only 30 milligrams of citricidal were required to produce 100% e-coli inhibition for at least 50 milliliters of contaminated water, with a fecal coliform count of 2,000 colonies per 100 milliliters.
Figure 6: E-Coli Inhibition vs. Water Volume Treated with 0.3 grams AC and 30 mg Citricidal
The design of a sustainable water filtration system for the Philippines by Manhattan College and De La Salle University has been exceptionally successful thus far. The primary goals of heavy metal/pesticide removal, and disinfection have been achieved in laboratory testing using a column composed of coconut shell derived activated carbon and citricidal powder. The proposed water filter presents a promising solution in terms of economic feasibility and effectiveness for purifying contaminated water sources. The filters will be delivered to families in Nagcarlan in June 2011.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
|Other project views:||All 5 publications||1 publications in selected types||All 1 journal articles|
||Abulencia JP, Gallardo S, Abraham N, Caraccio A, Ruffini N, McDonnell K, Tanala F. Sustainability of water resources for the poor. Consilience: The Journal of Sustainable Development 2010;4(1):155-166.||