Desorption technologies for remediation of cesium-contaminated soils: a short review

Environmental Geochemistry and Health - This review summarizes the mechanisms for desorbing and extracting cesium (Cs+) from clay minerals and soil. Most techniques use ion exchange with acids,...     

Development of an empirical equation for the transverse dispersion coefficient in natural streams

In this study, a new empirical equation for the transverse dispersion coefficient has been developed based on the hydraulic and geometric parameters in natural streams using a regression technique. First, a total of 32 data sets in 16 streams were collected. Among those sets, 16 sets were used for deriving the new equation, and the other 16 sets were used for verifying the equation. Then, through dimensional analysis, it was found that the normalized transverse dispersion coefficient is associated with several parameters such as sinuosity, aspect ratio, and a friction term. The robust least square method was applied to estimate regression coefficients. The newly proposed equation was proven to be superior in explaining the dispersion characteristics of natural streams more precisely compared to the existing equations.     

Longevity of organic layers of vertical flow ponds for sulfate reduction in treating mine drainages in South Korea

This study was carried out to evaluate longevity of available organic materials used for sulfate-reducing bacteria (SRB) activity in vertical flow ponds (VFPs) to treat mine drainage in South Korea. Spent mushroom compost samples (SMC) were tested as substrates in VFPs and analyzed for total organic carbon in VFPs, and were collected to analyze total organic carbon (TOC), T-N, T-P, K, metals and residual cellulose to check the longevity assessment. Chemical analysis revealed that the average contents of Fe, Al and Mn in SMC of VFPs were 19,907, 32,137 and 434 mg/kg, respectively. The contents of Fe and Al in SMC of VFPs were much higher than those of the unused SMC (control), but to the contrary, those of Mn showed a reversed tendency. Average TOC content of the controls was 64.19% but in one of the VFP substrates was as low as 15.92%. This might be resulted from SRB consumed the available organic carbon in SMC as VFPs system aged. Contents of T-N in VFPs tended to decrease as VFPs aged. The residual cellulose ranged from 3.88 to 6.72% (g/g). There existed a negative relationship between residual cellulose contents and ages of VFPs. Assuming that SMC in all VFPs had similar compositions when the VFPs were initially established, trend analysis predicted that the amount of carbon source for SRB might be available for 12–15 years further, depending on VFPs.     

Development and Application of Green Composites: Using Coffee Ground and Bamboo Flour

Environmental degradation and global warming are increasing as a result of the use of petroleum. Therefore, many industries are seeking more eco-friendly materials that will decrease the level of environmental contamination and economic cost. Recently, the level of coffee consumption has increased rapidly. Therefore, the amount of coffee grounds discarded is increasing. In this study, polylactic acid, coffee grounds and bamboo flour were compounded for green composites. Coffee grounds are used in the recycling of food waste. In addition, 4,4-methylene diphenyl diisocyanate (MDI) was used as a coupling agent. The mechanical strength of green composites decreased with increasing natural filler content. However, mechanical and thermal properties were increased by the addition of MDI as a coupling agent. The hydroxyl groups of natural fillers reacted with the isocyanate group of MDI, and a urethane linkage was created between the polymer and natural fillers.     

Immobilization of lead in contaminated firing range soil using biochar

Soybean stover-derived biochar was used to immobilize lead (Pb) in military firing range soil at a mass application rate of 0 to 20 wt.% and a curing period of 7 days. The toxicity characteristic leaching procedure (TCLP) was performed to evaluate the effectiveness of the treatment. The mechanism responsible for Pb immobilization in military firing range soil was evaluated by scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDX) and x-ray absorption fine structure (XAFS) spectroscopy analyses. The treatment results showed that TCLP Pb leachability decreased with increasing biochar content. A reduction of over 90 % in Pb leachability was achieved upon treatment with 20 wt.% soybean stover-derived biochar. SEM-EDX, elemental dot mapping and XAFS results in conjunction with TCLP leachability revealed that effective Pb immobilization was probably associated with the pozzolanic reaction products, chloropyromorphite and Pb-phosphate. The results of this study demonstrated that soybean stover-derived biochar was effective in immobilizing Pb in contaminated firing range soil.     

Simultaneous removal of chlorinated aromatic hydrocarbons, nitrate, and chromate using micellar-enhanced ultrafiltration

Feasibility of micellar-enhanced ultrafiltration for the mixed waste that is consisted of chlorinated aromatic hydrocarbons, nitrate, and chromate was investigated using a cationic surfactant. The co-presence of nitrate and chromate did not significantly affect the removal of chlorobenzenes, and the co-presence of chlorobenzenes did not affect the removal of nitrate and chromate because chlorobenzenes were solubilized at the hydrophobic interior of the micelles by hydrophobic interaction, but nitrate and chromate were bound to the outer shell by electrostatic interaction. Micellar-enhanced ultrafiltration can be applied to treat the mixed wastes.     

Growth of non-English-language literature on biodiversity conservation

English is widely recognized as the language of science, and English-language publications (ELPs) are rapidly increasing. It is often assumed that the number of non-ELPs is decreasing. This assumption contributes to the underuse of non-ELPs in conservation science, practice, and policy, especially at the international level. However, the number of conservation articles published in different languages is poorly documented. Using local and international search systems, we searched for scientific articles on biodiversity conservation published from 1980 to 2018 in English and 15 non-English languages. We compared the growth rate in publications across languages. In 12 of the 15 non-English languages, published conservation articles significantly increased every year over the past 39 years, at a rate similar to English-language articles. The other three languages showed contrasting results, depending on the search system. Since the 1990s, conservation science articles in most languages increased exponentially. The variation in the number of non-English-language articles identified among the search systems differed markedly (e.g., for simplified Chinese, 11,148 articles returned with local search system and 803 with Scopus). Google Scholar and local literature search systems returned the most articles for 11 and 4 non-English languages, respectively. However, the proportion of peer-reviewed conservation articles published in non-English languages was highest in Scopus, followed by Web of Science and local search systems, and lowest in Google Scholar. About 20% of the sampled non-English-language articles provided no title or abstract in English; thus, in theory, they were undiscoverable with English keywords. Possible reasons for this include language barriers and the need to disseminate research in countries where English is not widely spoken. Given the known biases in statistical methods and study characteristics between English- and non-English-language studies, non-English-language articles will continue to play an important role in improving the understanding of biodiversity and its conservation.     

Simultaneous nitrification and denitrification of municipal wastewater in aerobic membrane bioreactors.

Simultaneous nitrification-denitrification (SND) of municipal wastewater was investigated in a laboratory-scale membrane bioreactor (MBR) operated at two different hydraulic retention times (HRTs), 0.5 and 1 day, dissolved oxygen 3.0 to 0.5 mg/L, and solids retention time (SRT) between 28 and 120 days. The organic loading rate (OLR) (0.11 to 0.64 kg chemical oxygen demand [COD]/m3/d) and influent soluble COD (SCOD)/ total Kjeldahl nitrogen (TKN) ratio (5 to 19) were varied by the addition of glucose. The ammonia-nitrogen and TKN removals were over 97%, and total nitrogen removal was approximately 89% in the MBR. The maximum specific nitrification rates (98 mg N/d/g VSS) and specific denitrification rates (81 mg N/d/g VSS) occurred at an SCOD/TKN ratio of 9.1. The optimum conditions for maximum total nitrogen removal by SND in a single reactor MBR have been found to be low dissolved oxygen (< 0.6 mg/L) and high OLR (approximately 0.64 kg COD/m3/d) at an HRT of 0.5 day and SRT of approximately 85 days.     

Effect of influent nitrogen speciation on organic nitrogen occurrence in activated sludge process effluents

The effect of influent nitrogen composition on organic nitrogen production in a sequencing batch reactor (SBR) activated sludge process was investigated. A laboratory-scale SBR was fed with three different type synthetic wastewaters with varying nitrogen compositions (phase I = nitriloacetic acid + ammonium [NH4-N], phase II = NH(4-)N, and phase III = amino acid mixture + NH(4-)N) was operated. The effluent contained approximately 1 to 2 mg N/L organic nitrogen, even though there was no organic nitrogen in influent. The effluent organic nitrogen increased to approximately 4 mg N/L when the influent composition was changed and then stabilized at <2 mg N/L. The maximum nitrifier growth rate constants (microN) were calculated as 0.91+/-0.10 to 1.14+/-0.08 day-1, 0.82 +/-0.13 day-1, and 0.89+/-0.08 day-1 at 20 degrees C for the three different influent compositions. The effluent colloidal organic nitrogen (CON) was negligible, suggesting that the effluent CON found in full-scale plants may be the result of influent-derived suspended matter.