Latorre Andújar, Isomar

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    Feasibility of open pit restoration with coal ash aggregates: ground water quality assessment
    (2010) Latorre Andújar, Isomar; Hwang, Sangchul; College of Engineering; Bogere, Mosés; Deng, Yang; Department of Civil Engineering; Gutierrez, Gustavo
    Coal ash aggregates (CAAs) are a by-product or waste of coal-fired power plants. Generally, CAAs are a solidified mixture of fly ash and bottom ash. CAAs from AES power plant in PR was studied and evaluated as a potential backfilling amendment material for restoration of open pit quarries in Puerto Rico. Physiochemical influence of CAAs on water quality parameters, including water infiltrated, pH, turbidity, conductivity, hardness, alkalinity, lead, cadmium, and phosphate and nitrate concentrations, in subsurface soils and groundwater was evaluated. Experimental results confirmed the feasibility of CAAs as backfilling amendments for an open pit restoration without detrimental effects to soil and groundwater qualities. This provides a new alternative reutilization of CAAs in the area of environmental engineering. If this approach is implemented, it should lead to utility of additional land for agricultural purposes in PR where land is almost always a limiting natural resource. A statistical screening test using a 2³ factorial design was performed to determine the worst case scenario (WCS) and the best case scenario (BCS) of backfilling design that took into consideration of CAA/topsoil ratio, rain intensity, and CAA size as treatment factors and water quality parameters as responses. Low rainfall intensity, large CAA capacity and more CAA dosage resulted in WCS. On the other hand, high rainfall intensity, small CAA size, and less CAA dosage presented BCS effects with respect to pH, turbidity, conductivity, hardness and water infiltration. In addition, WCS and BCS restoration was further assessed in terms of influence of each backfilling component on water quality parameters, temperature effect and CAA influence on responses. Increments in several parameter values (i.e. pH, hardness and conductivity) were observed due to CAA amendment. However, the responses of parameters such as turbidity, conductivity and hardness clearly validated WCS and BCS. Individual soils and CAA columns contribution to overall water qualities was also evaluated and validated the results obtained from the initial statistical screening test. The potential capacity of CAAs to remove nitrate and phosphate was also evaluated. It was observed that CAAs did not reduce nitrate concentrations, while there were substantial reductions in phosphate concentrations. The efficiency of phosphate removal was observed with high CAA dosage, increase in CAA size, and low flow. The effect on groundwater quality was assessed by BCS restoration in conjunction with parameter responses in an aquifer system. Good results were obtained for all measured parameters.
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    Biodeterioration of PVC plastics, biochemical fate of DEHP, and bioreactor landfills for DEHP-containing leachate management
    (2014-12) Latorre Andújar, Isomar; Hwang, Sangchul; College of Engineering; Bogere, Mosés; Montalvo, Rafael; Tarafa, Pedro J.; Department of Civil Engineering; Parés-Matos, Elsíe I.
    Di-(2-ethylhexyl) phthalate (DEHP), a widely used plasticizer in the manufacture of polymeric materials such as polyvinyl chloride, was studied in order to understand its fate and transport in complex environments such as landfills. Towards this effort, several experiments were conducted to assess the fate and biological and physicochemical processes that promote leaching and degradation of DEHP, and also to evaluate possible treatment methods. Biodegradation as well as advance oxidation, using an adsorption process to a mesoporous material (SBA-15) and Fenton regeneration, were the treatments evaluated to increase the waste decomposition rate and simultaneously removed DEHP and arsenic, respectively. Landfill leachates contained multiple organic and inorganic compounds making it difficult to treat them. Despite this, adsorption-Fenton process removed efficiently organic and inorganic contaminants. Arsenic was utilized as the inorganic model for its toxicity and frequency in landfill leachates. The first task was to isolate bacteria that metabolize DEHP from landfill leachate and then identify it. The second task was to test the rate and extent of DEHP biodegradation. Then, the third task was to evaluate the bacteria potential for plastic biodeterioration using shower curtains as the model DEHP-containing plastic waste. The fourth task was to evaluate a series of biochemical DEHP leaching using the model plastic wastes of shower curtains, cable insulations and floorings in batch and column settings. The fifth task was to evaluate DEHP fate and plastic deterioration in lab-scale monofills with the mixed of plastic wastes mentioned above. In addition, leachate treatment by adsorption and Fenton regeneration with mesoporous SBA-15 was performed and it was established that this enhanced waste decomposition via leachate recirculation after simultaneous removal of DEHP and arsenic in leachate. Two bacteria strains, LHM1 and LHM2 (S2), able to metabolize DEHP as their primary carbon source to an extent of 75 to 90% were successfully isolated from a local landfill. Di-butyl phthalate (0.010-0.126 mg L-1 ) and di-ethyl phthalate (0.145-0.280 mg L-1 ) were detected as intermediates of the DEHP biodegradation. Molecular identification of 16S rRNA gene showed that the strains were closely related to Gram-positive Chryseomicrobium spp. and Lysinibacillus spp., respectively. Physicochemical experiments showed that DEHP could fortuitously be leached out of PVC polymeric materials (as demonstrated in shower curtains, floorings and cable insulations as models) to the leachate even at a higher concentration than its water solubility especially at a greater humic acid concentration and higher temperatures. Biodeterioration and LSBM experiments showed that LHM1 and LHM2 (S2) were able to enhance biodeterioration of PVC shower curtains, floorings and cable insulations resulting in development of thicker biofilm on the surface of the materials and changes in thermogravimetric stability. As result, less amount of DEHP was present in a weaker bonding with the polymeric matrix of the materials biodeteriorated. Despite LHM1 and LHM2 (S2) capability of metabolizing DEHP, the strains also utilize other readily available carbonaceous compounds present in the monofill leachate. Adsorption-Fenton process was optimized in regard SBA-15 amount and Fe, As and H2O2 concentrations by response surface methodology to simultaneously remediate DEHP and As. During the adsorption, the optimum region was found at 1.1591 mM Fe, 18.74 mg SBA-15 and 3.71 mg L-1 As such 40-95 % and 90-95% of As(III) and DEHP were adsorbed onto SBA-15, respectively. For the Fenton regeneration, optimum treatment combinations were obtained at 0.5025 mM Fe, 22 mg SBA-15, 3.02 mg L-1 As and 22.50 mM H2O2. Removal efficiency of As(III) and DEHP fluctuates from 78 to 99% and 90 to 97%, respectively. This study has provided an understanding of the fate and transport of DEHP and how is biodegraded in landfill environments. Several studies demonstrated that DEHP could be linked to hepatocellular tumors, pre-term birth and may be a developmental and reproductive toxicant. It is believed that one of the main sources of DEHP exposure to the environment is through landfills with poor operation and maintenance. Most solid waste materials containing DEHP are disposed of in landfills and may migrate to groundwater and soil environments representing a threat to human receptors.