Journal of Hazardous, Toxic, and Radioactive Waste

The authors study two species of plant—water hyacinth (Eichhornia crassipes) and water spinach (Ipomoea aquatica). These plants are commonly found in aquatic bodies such as lakes, ponds, and rivers. Both plants are grown in a plant growth chamber and introduced to various pH levels and concentrations of fluoride for 10–15 days. Defluoridation efficiency of Eichhornia crassipes and Ipomoea aquatica are 58.9 and 40.9%, respectively. The fluoride removal efficiency of Eichhornia crassipes is greater than that of Ipomoea aquatica. The pH results for both plants are varied. The removal efficiency for fluoride decreases for both plants under both increasing and decreasing the pH. The roots play a major role in the defluoridation process because they accumulate the major part of the total fluoride accumulated by plant. Fluoride removal capacity of the roots of Eichhornia crassipes is found to be $\mathrm{1,148.479}\mathrm{\mu g}/\mathrm{g}{D}_W$ (dry weight of taken sample) whereas that of the roots of Ipomoea aquatica is $872.866\mathrm{\mu gm}/g{D}_W$. Because of exposure to fluoride, degradation in biomass substance is observed in both plants.

Precipitated Cs tetraphenylborate, along with K tetraphenylborate and aqueous alkaline supernate, is present in certain high-level waste tanks at the Savannah River Site. Two possible processes for transferring the ${\mathrm{Cs}}^{+}$ (and ${\mathrm{K}}^{+}$) into the aqueous phase are described. One consists of displacement of the heavy alkalis from the solid tetraphenylborate by adding a tetraalkylammonium hydroxide. Almost 100% solubilization is obtained at ambient temperature using tetra-$n$-butylammonium hydroxide. The other consists of oxidative decomposition of the tetraphenylborate using persulfate. The extent of solubilization is found to increase with increasing temperature and persulfate:tetraphenylborate ratio. High yields of tetraphenylborate decomposition are obtained at elevated temperatures (55–90°C), and these yields increase with rising persulfate:tetraphenylborate ratios. The decomposition yields are lowered in the presence of nitrite, which is a component of the alkaline supernate, but are still significant, especially at elevated temperatures and high persulfate:tetraphenylborate ratios. The adverse effect of nitrite can be greatly reduced by lowering the pH.

Most closed landfills in Illinois are inadequately lined former dumps with thin earthen covers. Customary walkover inspections of these legacy landfills can overlook defects in the cover and surrounding area that increase threats to human health and water resource quality. Publicly available aerial orthophotography and light detection and ranging (lidar) data were interpreted for 10 closed, managed landfills in Illinois. Visible and near-infrared data were enhanced by histogram stretching, normalized difference vegetation index, iron oxide index, and images draped over lidar data to improve recognition of defects and features of interest. Image interpretation keys were used and confidence levels assigned to create previsit maps showing deformation features, including depressions and dimples that collect runoff, gullies eroding into earthen covers, slope instability, wet and barren spots that may be outlets for leachate seeps, and vegetation anomalies that can indicate outgassing. Defects on inspection maps were ordered for on-site reconnaissance. Changes observed from comparing historical and current imagery and geographic information system–based defect-tracking databases can provide a basis for scheduling maintenance and prioritizing repairs for sustainable postclosure and custodial landfill management.

This research was conducted in a laboratory-scale setup to study (1) the biodegradation of laundry and dishwashing detergents under aerobic and anaerobic conditions and to quantify the degradation at steady state in terms of kinetic parameters degradation at steady state in terms of kinetic parameters and (2) the inhibition caused by the laundry and dishwashing detergents on growth-substrate utilization by unacclimated ethanol-enriched aerobic and anaerobic microbial cultures. The test reactors were monitored for chemical oxygen demand (COD), total organic carbon (TOC), and surfactant removal at different solid retention times (SRTs). Very high COD and surfactant removal were obtained within the tested range under aerobic conditions. The removal efficiency progressively deteriorated with decreasing SRT. However, even at an SRT as low as 3 days, COD removal was above 85%. The detergents had a severely detrimental effect on anaerobic microorganisms. Biogas production stopped completely after the first 10 days of the experiment. The detergents caused competitive inhibition to aerobic microorganisms at doses above $200\mathrm{mg}/\mathrm{L}$ and to anaerobic microorganisms at doses above $25\mathrm{mg}/\mathrm{L}$.

A newly developed and validated numerical model that accounts for the coupled hydro-bio-mechanical processes in municipal solid waste (MSW) landfills, was employed to assess influence of various field conditions and system variables on the performance of bioreactor landfills. The numerical model integrates a hydraulic two-phase flow model which assumes landfill leachate and gas as two immiscible phases, a mechanical model based on plain-strain formulation of Mohr-Coulomb constitutive law, and a first-order decay biodegradation model for modeling coupled hydro-bio-mechanical processes in bioreactor landfills. The influence of typical field conditions and system variables, namely, the landfill slope configuration, geometric configuration of the leachate recirculation system, and the mode of leachate injection on the bioreactor landfill performance were evaluated. The bioreactor landfill performance was investigated with regards to hydraulic behavior (e.g., moisture distribution, waste saturation, pore water and capillary pressures), extent of biodegradation and mechanical response (e.g., slope stability, landfill settlement, in-plane shear behavior of composite liner system) during the operation of leachate injection. Overall, this parametric study concluded that various field conditions and system variables significantly influence the performance of bioreactor landfills. Therefore, these system variables must be properly accounted for when optimizing the performance of bioreactor landfills undergoing coupled hydro-bio-mechanical processes during the leachate injection operations.