Journal of Hazardous, Toxic, and Radioactive Waste

This paper presents two rule-based models based on fuzzy set theory, which can be used to approximately predict the adsorption of nickel and zinc in soils. The models consider organic matter content, cation exchange capacity, and pH as the input parameters and provide the partition coefficients of nickel and zinc. The rule-based models were developed using data available in literature. The models were validated using data obtained from laboratory experiments conducted using six different soil types. The calibrated models were then used to generate plots that can be used to obtain approximate partition coefficients for nickel and zinc.

A two-step process for the removal of phenol and benzenediols, namely catechol, resorcinol, and hydroquinone, from buffered synthetic wastewater was investigated. The proposed process comprised laccase catalyzed conversion of these substrates using laccase from Trametes villosa followed by the removal of products generated using alum as coagulant. The effects of pH, laccase concentration, substrate concentration, and the presence of a hydrophilic polymer additive [polyethylene glycol (PEG)] to achieve $⩾95\mathrm{\%}$ removal of the substrate in a 3-h reaction period at room temperature were determined. The parent compound, phenol, required the most enzyme, followed by resorcinol, catechol, and hydroquinone. PEG showed no effect on any of the substrate conversions. Substrate conversion and enzyme inactivation were monitored over the reaction period. As phenol and benzenediols might coexist in industrial effluents, enzymatic treatment of an equimolar mixture of these four substrates was examined. Except for hydroquinone, the proposed enzymatic treatment method is a viable alternative means to remove phenol and benzenediols from industrial wastewaters.

Cetyltrimethyl ammonium chloride (CTAC), linear alkylbenzene sulfonate (LAS), and t-octylphenoxypolyethoxyethanol (Triton X-100) were selected to investigate their ability and corresponding physiological mechanisms to control turbulent biofilm formed by Chlorella vulgaris. Significant algicidal activity of CTAC was observed, in contrast to the minor inhibition on algae biomass generated by LAS and Triton X-100. CTAC-treated sample appeared to plasmolyze the algae cell, while LAS treated and Triton X-100-treated sample did not show obvious alteration. The increase in surfactant concentration led to the inhibition efficiency increase in acid phosphatase (ACP) activity. The ACP activities of CTAC-treated sample were restrained most among the tested surfactants. These results indicated the possible mechanisms of surfactants on the growth of algae and the potential application of cationic surfactants in controlling algae blooms.

This paper compares three current state-of-the-practice models, ALOHA, EPICode, and SCIPUFF for use in safety evaluations using data from a unique full-scale field experiment under low-wind speed conditions. The experiment included the release and transport of three gases: ammonia (buoyant), ethylene (neutral buoyant), and propylene (dense) in low-wind speed (diffusion) conditions, less than 2 m/s. In total there were 30 releases ranging from 6 to 30 min in duration. The diagnostics included nine meteorology stations on 100-m centers and 36 photo ionization detectors in a radial pattern. Diffusive conditions are difficult to model, and all of the models had difficulty replicating the field measurements. However, the work does show that these models, if used correctly, are conservative (overpredict concentrations) and can be used for safety and emergency planning.

The behavior of the ammonia $\left({\text{NH}}_3\right)$ oxidation was studied by selective catalytic oxidation (SCO) over a Pt-Pd-Rh nanocomposite cordierite catalyst in a tubular fixed-bed flow quartz reactor at temperatures between 423 and 623 K. The catalysts’ surface properties were characterized using scanning transmission electron microscopy-energy-dispersive X-ray, optical microscopy, and ultraviolet visible. The experimental results show that high activities for ${\text{NH}}_3$ removal were achieved during catalytic oxidation over the Pt-Pd-Rh cordierite catalyst at 623 K with an oxygen content of 4%. ${\text{N}}_2$ was the main product in the ${\text{NH}}_3$ -SCO process over the Pt-Pd-Rh nanocomposite cordierite catalyst. These results also verify the Pt-Pd-Rh metals on cordierite surfaces, resulting in the formation of catalytically active sites at the metal-support interface in the reduction of ${\text{NH}}_3$ in this process. In addition, the Pt-Pd-Rh nanocomposite cordierite-induced cytotoxicity testing was mainly applied to the human lung MRC-5 cell line, and the percentage of cell survival was determined by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium analysis in vitro. For Pt-Pd-Rh nanocomposite cordierite, only minor cytotoxicity was observed when human lung cells were exposed.

The impact of chemical oxygen demand/nitrogen (COD/N) values of feed wastewater on COD and nitrogen removal and biomass growth in a sequencing fed-batch reactor (SFBR) operation was investigated. The multiple microbial reactions involved in the simultaneous removal process of carbonaceous and nitrogenous components in the SFBR system were analyzed using a set of kinetics mathematical model. The results indicate that COD/N ratios strongly influence COD and total nitrogen removal efficiency. The COD removal efficiency per gram microorganism changed from 64.3 to 78.1% at $\text{COD}/\text{N}=11.9–2.5$ . The total nitrogen removal efficiency changed from 10.3 to 34.2% at $\text{COD}/\text{N}=2.5–11.9$ . However, variable COD/N ratios of feed wastewater are not marked for biomass growth rate.

Model was developed by two-level five-factor full-factorial designed-experiment to predict arsenic removal from contaminated water by electrocoagulation. Five factors, namely arsenic concentration (As), solution volume $\left(V\right)$ ; current $\left(I\right)$ , electrode area $\left(A\right)$ , and current processing time $\left(t\right)$ were investigated. Among the factors, arsenic concentration (As) and volume $\left(V\right)$ have negative effect, and area $\left(A\right)$ , time $\left(t\right)$ , and current $\left(I\right)$ have positive effect on arsenic removal. Within the studied levels of the factors, variance analysis at 5% significance level indicated that electrode area is not significant in arsenic removal by electrocoagulation. The model predicted reasonably good arsenic removal $\left(\text{error}<2\mathrm{\%}\right)$ from low (0.288 mg/L) and high (0.882 mg/L) initial arsenic concentrations in presence of naturally cooccurring solutes in the groundwater. For the range of operating variables studied, optimum removal of arsenic (98.56%) is obtained at higher arsenic concentration (1.18 mg/L), lower volume (1 L), higher current (3 A), and higher current processing time (120 s).

Effects of groundwater cooccurring solutes such as phosphate $\left({\text{PO}}_4\right)$ , silicate $\left({\text{SiO}}_3\right)$ , bicarbonate $\left({\text{HCO}}_3\right)$ , calcium (Ca), and iron (Fe) on arsenic removal were investigated in this study. Investigation by two-level full-factorial designed experiments revealed that ${\text{PO}}_4$ and ${\text{SiO}}_3$ have negative effect on arsenic removal, whereas ${\text{HCO}}_3$ has negligible positive effect. The effects of Ca and Fe present in groundwater have positive effect on arsenic removal by electrocoagulation (EC). Hypothesis testing at 5% significance level suggests that alkalinity $\left({\text{HCO}}_3\right)$ is not an important parameter in arsenic removal by EC in naturally occurring pH range of water.