This thesis has three related elements for organics control in drinking water. First, coagulation chemistry for Alum and Aluminum Chlorohydrate (ACH) was optimized for significant organics removal to address membrane fouling issue at a local municipal water treatment plant in Arizona. Second, Rapid Small Scale Column Tests were conducted for removal of Perfluorinated compounds (PFC), PFC were present in groundwater at a local site in Arizona at trace levels with combined concentration of Perfluorooctaneoic Acid (PFOA) and Perfloorooctanesulfonic Acid (PFOS) up to 245 ng/L. Groundwater from the concerned site is used as drinking water source by a private utility. PFC Removal was evaluated for different GAC, influent concentrations and particle sizes. Third, a new testing protocol (Mini Carbon Block (MCB)) for bench scale study of POU water treatment device, specifically carbon block filter was developed and evaluated. The new bench scale decreased the hydraulic requirements by 60 times approximately, which increases the feasibility to test POU at a lab scale. It was evaluated for a common POU organic contaminant: Chloroform, and other model contaminants.
10 mg/L of ACH and 30 mg/L of Alum with pH adjustment were determined as optimal coagulant doses. Bituminous coal based GAC was almost three times better than coconut shell based GAC for removing PFC. Multiple tests with MCB suggested no short circuiting and consistent performance for methylene blue though chloroform removal tests underestimated full scale carbon block performance but all these tests creates a good theoretical and practical fundament for this new approach and provides directions for future researchers.
First, I found that fermentation, not anode respiration, was the rate-limiting step for achieving complete organics removal, along with high current densities and CE. The best performance was achieved by doing most of the fermentation in an independent reactor that preceded the MXC. I also outlined how the efficiency of fermentation inside MXCs can be enhanced in order to make MXCs-based technologies cost-competitive with other anaerobic environmental biotechnologies. I revealed that the carbohydrate and protein contents and the BOD5/COD ratio governed the efficiency of organic-matter fermentation: high protein content and low BOD5/COD ratio were the main causes for low fermentation efficiency.
Next, I showed how a high ammonium concentration can provide kinetic and metabolic advantages or disadvantages for anode-respiring bacteria (ARB) over their competitors, particularly methanogens. When exposed to a relatively high ammonium concentration (i.e., > 2.2 g total ammonia-nitrogen (TAN)/L), the ARB were forced to divert a greater electron flow toward current generation and, consequently, had lower net biomass yield. However, the ARB were relatively more resistant to high free ammonia-nitrogen (FAN) concentrations, up to 200 mg FAN/L. I used FAN to manage ecological interactions among ARB and non-ARB in an MXC fed with fermentable substrate (glucose). Utilizing a combination of chemical, electrochemical, and genomic tools, I found that increased FAN led to higher CE and lower methane (CH4) production by suppressing methanogens. Thus, managing FAN offers a practical means to suppress methanogenesis, instead of using expensive and unrealistic inhibitors. My research findings open up new opportunities for more efficient operation of MXCs; this will enhance MXC scale-up and commercial applications, particularly for energy-positive treatment of waste streams containing recalcitrant organics.
Much of Nepal lacks access to clean drinking water, and many water sources are contaminated with arsenic at concentrations above both World Health Organization and local Nepalese guidelines. While many water treatment technologies exist, it is necessary to identify those that are easily implementable in developing areas. One simple treatment that has gained popularity is biochar—a porous, carbon-based substance produced through pyrolysis of biomass in an oxygen-free environment. Arizona State University’s Engineering Projects in Community Service (EPICS) has partnered with communities in Nepal in an attempt to increase biochar production in the area, as it has several valuable applications including water treatment. Biochar’s arsenic adsorption capability will be investigated in this project with the goal of using the biochar that Nepalese communities produce to remove water contaminants. It has been found in scientific literature that biochar is effective in removing heavy metal contaminants from water with the addition of iron through surface activation. Thus, the specific goal of this research was to compare the arsenic adsorption disparity between raw biochar and iron-impregnated biochar. It was hypothesized that after numerous bed volumes pass through a water treatment column, iron from the source water will accumulate on the surface of raw biochar, mimicking the intentionally iron-impregnated biochar and further increasing contaminant uptake. It is thus an additional goal of this project to compare biochar loaded with iron through an iron-spiked water column and biochar impregnated with iron through surface oxidation. For this investigation, the biochar was crushed and sieved to a size between 90 and 100 micrometers. Two samples were prepared: raw biochar and oxidized biochar. The oxidized biochar was impregnated with iron through surface oxidation with potassium permanganate and iron loading. Then, X-ray fluorescence was used to compare the composition of the oxidized biochar with its raw counterpart, indicating approximately 0.5% iron in the raw and 1% iron in the oxidized biochar. The biochar samples were then added to batches of arsenic-spiked water at iron to arsenic concentration ratios of 20 mg/L:1 mg/L and 50 mg/L:1 mg/L to determine adsorption efficiency. Inductively coupled plasma mass spectrometry (ICP-MS) analysis indicated an 86% removal of arsenic using a 50:1 ratio of iron to arsenic (1.25 g biochar required in 40 mL solution), and 75% removal with a 20:1 ratio (0.5 g biochar required in 40 mL solution). Additional samples were then inserted into a column process apparatus for further adsorption analysis. Again, ICP-MS analysis was performed and the results showed that while both raw and treated biochars were capable of adsorbing arsenic, they were exhausted after less than 70 bed volumes (234 mL), with raw biochar lasting 60 bed volumes (201 mL) and oxidized about 70 bed volumes (234 mL). Further research should be conducted to investigate more affordable and less laboratory-intensive processes to prepare biochar for water treatment.
As educational tactics circulate globally, so too does the prospect of understanding sustainability amongst informed individuals and what it means for our society. Just in the past few decades, the environmental movement has changed the way in which people think about their own impact upon the planet. It is becoming a facet of common knowledge for society to realize the potential detriment of their actions, and for this, we should be grateful. However, there is much work to be done regarding all aspects of sustainability and environmental crises. This paper offers a look into the world of sustainable sunscreen usage, something that is not often thought about as an aspect of sustainable consideration. The task of this research opportunity was to examine a sample of survey respondents and connect their responses from 15 questions to different hypotheses. Alongside the discussion of sunscreen filters damaging sensitive ocean ecosystems, this research also looks into the overall importance of sunscreen for one’s health and the ways in which it can be used safely. My hope is that readers will realize the value of using sunscreen on a daily basis and become better informed of sustainability challenges and healthcare disparities.