Journal of Hazardous, Toxic, and Radioactive Waste

This study was conducted to characterize the adsorption of ${\mathrm{Cd}}^{2+}$ and ${\mathrm{Pb}}^{2+}$ by raw coconut husk (RCH) and humic acid–treated coconut husk (HACH). Grounded and sieved coconut husk (CH) from Sri Lanka was treated with humic acid to use as the adsorbent in laboratory experiments. Capacities of HACH and RCH for adsorption of ${\mathrm{Cd}}^{2+}$ and ${\mathrm{Pb}}^{2+}$ at different pH, ionic strengths, initial metal concentrations, and contact times between adsorbent and adsorbate were measured. The effects of binary metal solution, anions, and cations on adsorptions of ${\mathrm{Cd}}^{2+}$ and ${\mathrm{Pb}}^{2+}$ by treated and nontreated CH in batch experiments were also examined. The surface characteristics of HACH and RCH were investigated by scanning electron micrography (SEM), X-ray energy dispersion analysis (EDAX), methylene blue (MB), and the Brunauer, Emmett, and Teller (BET) methods to explain the results. Results showed that adsorption of ${\mathrm{Cd}}^{2+}$ and ${\mathrm{Pb}}^{2+}$ ions by HACH was independent of pH and ionic strength. The maximum adsorption capacities of ${\mathrm{Cd}}^{2+}$ and ${\mathrm{Pb}}^{2+}$ of HACH were 47.28 and $66.26\mathrm{mg}{\mathrm{g}}^{-1}$ and were greater than 24.24 and $21.21\mathrm{mg}{\mathrm{g}}^{-1}$ for RCH. The adsorption of both ${\mathrm{Cd}}^{2+}$ and ${\mathrm{Pb}}^{2+}$ onto HACH was a chemical sorption, and ${\mathrm{Pb}}^{2+}$ adsorption needed a longer reaction time than ${\mathrm{Cd}}^{2+}$ adsorption. The adsorption reaction rates of ${\mathrm{Cd}}^{2+}$ and ${\mathrm{Pb}}^{2+}$ of HACH were 0.056 and $3.17\mathrm{mg}{\mathrm{g}}^{-1}{\min }^{-1}$. Some anions and cations affected the adsorption of ${\mathrm{Cd}}^{2+}$ and ${\mathrm{Pb}}^{2+}$ onto HACH. Based on the results from adsorption tests under different conditions, RCH and HACH are effective for individual removal of ${\mathrm{Cd}}^{2+}$ and ${\mathrm{Pb}}^{2+}$ from aqueous solutions. However, humic acid treatment effectively removes metal ions from single metal solutions, although the removal of metal ions in the presence of coexisting ions and other anions and cations could be retarded.

The fundamental process involved in the operation of bioreactor landfills is the addition of water and/or the recirculation of leachate into the landfill’s waste mass for rapid waste stabilization, waste decomposition, and increased rate of gas generation. However, operating a landfill as a bioreactor landfill requires the availability of a sufficient amount of fresh water in close proximity to the landfill facility. In coastal regions, where freshwater supplies may be scarce, available saline water can be considered for bioreactor operation. However, limited studies are available on the effect of using saline water for the biodegradation of municipal solid waste (MSW). The objective of the current research is to investigate the effects of adding and/or recirculating saline water for the biodegradation and landfill gas generation of MSW at the Cefe Valenzuela Landfill, Corpus Christi, Texas. To accomplish this objective, two sets of bioreactor cells were simulated in the laboratory. Each set of reactor consisted of two 22.7 L (6 gal.) reactors. The first set of reactors was filled with fresh MSW collected from the Cefe Valenzuela Landfill and operated with fresh water (control reactors); the second set of reactors was operated with saline water collected from the landfill site. To assess the effect of salinity on biodegradation, the composition and volume of generated gas and the pH of generated leachate were regularly monitored. According to the experimental results, the utilization of saline water for bioreactor operation may delay the methane generation of landfills. However, once the methane production starts, the gas generation rate and volume were similar to bioreactor operation using deionized water. Therefore, the addition of saline water for bioreactor operation is considered suitable for the Cefe Valenzuela Landfill at Corpus Christi, Texas.

Solute transport is an important factor governing soil environmental processes, such as effective fertilizer application or dispersion areas of remediation chemicals for contaminated soils. Macropores are ubiquitous in soils. In unsaturated conditions, they enhance air intrusion into soils, thus reducing the chances of clogging and surface ponding. However, their structure is hard to maintain, and they tend to collapse during long-term infiltration. In this experiment, macropore fillings were introduced into the pores to maintain their structure. Solute transport experiments were conducted for four soils with no macropores, empty macropores, macropores with paper towel fillings, and macropores with glass fiber fillings. The macropores with fillings worked as water pathways that conducted solutions to the deeper profile without saturation at the surface, thus avoiding clogging. When bio-remediation experiments were conducted using these four soil columns, soil columns with glass fiber fillings maintained 0.6–0.8 of the saturated water content, which was found to enhance biological activity. The resultant bio-remediation was best for glass fiber fillings because artificial macropores with fibrous fillings maintained a macropore structure, which gave a stable infiltration rate for 30 days.

Pump and treat (P&T) is a technology that has been extensively used to remove and/or contain contaminated groundwater. P&T systems conventionally operate continuously, which requires significant amounts of energy. The use of renewable energies to meet power demands of remedial systems may reduce a project’s carbon dioxide emissions. This paper analyzes the performance of a hypothetical photovoltaic (PV)–powered P&T system that operates both intermittently by assuming that the system does not include an energy storage component and continuously by assuming that the system includes a relatively small capacity energy storage component using widely available Typical Meteorological Year 3 (TMY3) data. The results are compared against a baseline case of continuous pumping at a constant rate using volume of groundwater removed and capture zone width. The comparison shows that the cost-benefit of increasing the capture zone widths and volume of extracted groundwater by increasing the rated flow rate is greater than by including a relatively small-capacity energy storage component. PV-powered P&T system performance, without or with limited relatively small-capacity energy storage, is conditioned to site-specific hydrologic and seasonal characteristics. The methodology presented in this paper can be used to assess and compare the performance of each alternative.

Decolorization of anaerobically digested and polyaluminium chloride (PAC) treated distillery spentwash was studied in a fungal sequencing batch aerobic reactor (FSBAR). Pellets of isolated Aspergillus niger IITB-V8 species were used in the experiments. In continuous/sequencing batch reactors, decolorization of distillery spentwash cannot be maintained for a longer duration as efficiency decreases after 5–6 days; therefore, effects of hydraulic retention time (HRT), cellular retention time (CRT), and biomass renovation on the decolorization were studied in FSBAR. The HRT for maximum decolorization of 69% was found out to be 2.5 days while the optimum CRT for maximum decolorization of 69% was obtained as 7.5 days. But at this CRT also, maximum decolorization could not be maintained after 7.5 days. Decrease in decolorization was observed due to change in fungal pellet morphology over time. Biomass renovations were undertaken to maintain satisfactory decolorization percentages for a longer period (30 days) and it was found that partial biomass renovation ($1/3$) every 2.5 days resulted in consistent decolorization of 69% with overall decolorization of 87%.

Groundwater at many existing and former industrial areas and disposal sites is contaminated by halogenated organic compounds that were released into the environment. One cost-effective approach for the remediation of the chlorinated solvent contaminated aquifers is the installation of biobarriers within aquifers. The objective of this study was to assess the potential of using an in situ biobarrier system containing the emulsified substrate (ES) to bioremediate and contain the trichloroethylene (TCE) plume. The ES contained soybean oil, lactate, biodegradable surfactant, and nutrients, and thus it was able to provide carbon sources for the enhancement of the reductive dechlorination of TCE. A field-scale study was operated at a TCE-contaminated site, and 150 L of ES solution was pressure-injected into three remediation wells located in the upgradient area of the plume to form a biobarrier. Results show that the total organic carbon (TOC) went up from $12\mathrm{mg}/\mathrm{L}$ (before ES injection) to $\mathrm{9,800}\mathrm{mg}/\mathrm{L}$ after 45 days of ES injection, and slowly declined to $\mathrm{1,500}\mathrm{mg}/\mathrm{L}$ after 230 days of operation. The increased TOC caused the complete consumption of groundwater dissolved oxygen in the injection wells (dropped from 0.6 to $0\mathrm{mg}/\mathrm{L}$) after 5 days of the ES injection. Results also show that the TCE concentrations dropped from 140 to below $1\mu g/\mathrm{L}$ after 10 days of ES injection in the biobarrier. The TCE degradation byproducts [e.g., 1,1-dichloroethene (1,1-DCE), vinyl chloride (VC)] were also observed in the injection and downgradient monitor wells. Results of microbial analyses show that various TCE-degrading bacteria exist in the subsurface, including Ralstonia sp., Clostridium sp., uncultured Burkholderiales bacterium, Hydrogenophaga sp., Acidovorax sp., Hydrocarboniphaga sp., uncultured Curvibacter sp., Pseudomonas sp., Comamonas sp., Aquabacterium sp., and Variovorax strains. Results indicate that the injected ES enhanced the anaerobic dechlorination of TCE, and the developed biobarrier could contain the TCE plume effectively. The biobarrier has the potential to be developed into an environmentally and economically acceptable remedial system.

Recently, carbon capture and storage by soils is recognized as an important function of agricultural fields. When discussing global warming mitigation such as proper agricultural practices and/or an appropriate depth of composting in agricultural lands for soil carbon storage, not only ${\mathrm{CO}}_2$ efflux, but also profiles of ${\mathrm{CO}}_2$ concentrations in soil air, are important. This study evaluated the performance of the SOILCO2 model in predicting soil ${\mathrm{CO}}_2$ dynamics, especially ${\mathrm{CO}}_2$ concentrations at various depths in an arable bare land of Andisol. We attempted to experimentally determine two soil parameters required for the ${\mathrm{CO}}_2$ production model, the optimal ${\mathrm{CO}}_2$ production rate and the parameter of a depth-dependent ${\mathrm{CO}}_2$ production function by measuring ${\mathrm{CO}}_2$ efflux from the surface and a vertical distribution of concentration of dissolved organic carbon, respectively. Soil ${\mathrm{CO}}_2$ concentrations, water contents and temperatures were continuously monitored for approximately one year at three different depths, and simulated results were compared with the observed data for model validation. We concluded that, for the upper soil layer (from the surface to approximately 20 cm in depth), the two soil parameters were properly determined, and soil ${\mathrm{CO}}_2$ dynamics in arable bare land could be well predicted by using the SOILCO2 model. To improve simulation results of ${\mathrm{CO}}_2$ concentrations, especially in deeper layers, it may be necessary to consider the biodegradability of dissolved organic carbon.

Urban storm water runoff is contaminated as deleterious materials wash from roadways, parking lots, and open spaces, and the subsequent discharge into surface water sources, such as lakes, can pose adverse effects on public health and the environment. Oil leaks and spills on roadways and parking lots can contain toxic polycyclic aromatic hydrocarbons (PAHs) that can be washed by storm water runoff. Although many best management practices have been developed to treat urban storm water, in-ground filter systems can be best suited in urban site-constrained settings. This paper investigates the effectiveness of different permeable inorganic materials as filter media for the removal of PAHs from storm water runoff. Several series of batch experiments were conducted using four different filter media (calcite, zeolite, sand, and iron filings) and synthetic storm water containing representative PAHs (naphthalene or phenanthrene) at different initial concentrations. The PAH removal and system chemistry in terms of pH, oxidation-reduction potential (ORP), and electrical conductivity (EC) were determined. All of the filter media possessed porous structure and surface characteristics that allowed adsorption and removal of the selected PAHs from the storm water runoff to more than 90%. Calcite and zeolite increased the pH and reduced the ORP and EC significantly as compared with sand and iron filings. Overall, this study demonstrated that the selected filter media have great potential to remove PAHs from urban storm water runoff.

A vapor intrusion investigation was conducted at a New Jersey site contaminated with tetrachloroethene (PCE) and trichloroethene (TCE). Several residential and commercial buildings are nearby and may be impacted, including a middle school, a learning center, and a church. Groundwater water samples were collected from the site and analyzed for volatile organic compounds (VOCs). Based on the results of the groundwater samples, subslab soil gas and indoor samples were collected from the buildings located in the area surrounding the site and analyzed for VOCs by using the U.S. Environmental Protection Agency Method TO-15. The analytical data were compared against background ambient air data and the soil gas and indoor air data were compared against New Jersey state screening levels. Both PCE and TCE were found above screening levels in groundwater and subslab soil gas samples. It is recommended that further groundwater and vapor intrusion investigations be performed at the nearby buildings and an appropriate remediation technology be used to remediate vapor intrusion at the affected buildings.