The major obstacle to biological denitrification is the cost of the carbon source used as electron donor. Therefore, it is desirable to identify inexpensive alternatives to enable efficient denitrification. Corn husk, a type of agroforestrial waste, has the potential to release organic materials. This study investigated the possibility of enhancing aerobic denitrification by thermophilic Chelatococcus daeguensis TAD1 when corn husk that had been pretreated with hydrolysate was employed as the carbon source. The results showed that the particle size of 10–40 mesh, the NaOH dose of 0.01 mol L⁻¹, the loading dose of 60 g L⁻¹, the temperature of 40 °C, and pretreatment time of 24 h were appropriate to release available carbon source for denitrification by TAD1. Additionally, an initial pH of 8.5 was optimal for denitrification with maximum N₂O production as low as 0.053 % of denitrified NO₃ ⁻-N, which was the least at pH 6.0–9.0, taking advantage of corn husk hydrolysate (CHH). At an initial NO₃ ⁻-N of 253.36 mg L⁻¹, the denitrification rate and removal efficiency reached 24.55 mg L⁻¹ h⁻¹ and 96.91 %, respectively, without accumulation of nitrite and N₂O utilizing CHH as a sole carbon source. To sum up, CHH was an economical and efficient carbon source for aerobic denitrification by TAD1 with low levels of N₂O, capable of tolerating the fluctuation of pH and the high nitrate load.

Thermophile microorganisms play an important role in hydrocarbon degradation due to being adapted to extreme conditions of temperature, and different species are capable of resisting thermophile conditions. In this study, we evaluated the oil-degrading capacity of seven thermophilic bacterial strains. Maya crude oil, a type of Mexican heavy oil, was selected as carbon source, and residual hydrocarbon concentration (TRH) was used as indicator of microbial degradation crude oil. Only four strains presented could degrade hydrocarbons, and these strains were molecularly identified using 16s region amplification and showed homology with Bacillus licheniformis. Using a bubble column reactor, the identified strains were evaluated (together in a consortium) for hydrocarbon degradation at 45, 50 and 55 °C. Concentration of TRH was decreased to 77.70, 58.19 and 51.90 % at 50, 45 and 55 °C, respectively. The consortium showed substantial potential for degrading Maya crude oil at 50 °C.

In this study, the effect of flue gas CO₂ on growth, lipid production, and fatty acid composition of a green microalga Acutodesmus obliquus KGE 30 was investigated. The highest growth rate (0.46 g L⁻¹ and μₘₐₓ = 1.09 day⁻¹), total inorganic carbon removal (95.9 mg L⁻¹), and lipid productivity (20.1 mg L⁻¹ day L⁻¹) was obtained at 14.1 % CO₂ after 4 days of cultivation. In a semicontinuous batch reactor, the highest biomass production (1.19 g L⁻¹) was achieved after 12 days with continuous injection of flue gas CO₂. Compared with synthetic CO₂, fatty acid methyl ester analysis showed that the amount of unsaturated fatty acid increased by 19.2 % with 14.1 % flue gas CO₂. The application of flue gas CO₂ improved biomass production and lipid productivity in A. obliquus. The current investigation demonstrated that the use of flue gas CO₂ could reduce the cost of microalgae biomass production for better biofuel generation.

This paper attempts to investigate the emissions embodied in Australia’s economic growth and disaggregate primary energy sources used for electricity production. Using time series data over the period of 1990–2012, the ARDL bounds test approach to cointegration technique is applied to test the long-run association among the underlying variables. The regression results validate the long-run equilibrium relationship among all vectors and confirm that CO₂ emissions, economic growth, and disaggregate primary energy consumption impact each other in the long-run path. Afterwards, the long- and short-run analyses are conducted using error correction model. The results show that economic growth, coal, oil, gas, and hydro energy sources have positive and statistically significant impact on CO₂ emissions both in long and short run, with an exception of renewables which has negative impact only in the long run. The results conclude that Australia faces wide gap between emission abatement policies and targets. The country still relies on emission intensive fossil fuels (i.e., coal and oil) to meet the indigenous electricity demand.

Chlorine added to drinking water as a disinfectant is a concern of this generation. This is because chlorine reacts with dissolved organic compounds to form polychlorinated complexes that are carcinogenic. Available methods for the removal of chlorine and chlorinated compounds include adsorption, precipitation, electrolysis and ozonation, but some result in the generation of more toxic compounds. This study explored the use of zero-valent bimetals Fe/Zn for the degradation of chlorinated compounds in water which did not generate toxic by-products. The zero-valent bimetallic material was anchored on a polystyrene waste material as a green method of cleaning the environment. It was prepared through nitration, amination, complexation and reduction. The resulting solid material was characterised using Fourier transform infrared (FTIR). The material was also characterised using XPS which confirmed the presence of metals anchored on the material through complexation. The metals were also found to be present upon reduction to zero valence and even after the degradation process of the chlorinated organic compounds. It was then applied for the removal process. Optimization parameters such initial halide concentration, effect of time and bimetal dosage variation were established using synthetic water samples. It was found that the substrate-anchored ZVB material had a degradation capacity of 4.532, 5.362 and 4.513 μmol l⁻¹ for 1,2-dichloroethane, 2-chloro-2-methylpropane and 1-chlorobutane, respectively. The material was then applied on real samples sourced from Nairobi. Quantification of chlorine was done using potentiometric methods and the results confirmed that the degradation was first order. The degradation capacities were found to be 2.37 ± 0.01, 3.55 ± 0.01 and 3.72 ± 0.01 in that order.

This study aims at understanding characteristics of current traffic pollution at roadsides and to assess the use of magnetic parameters for a cost-efficient monitoring concept. We conducted a systematic monitoring study of roadside pollution at three sites in southern Germany and one site at Lanzhou/China. For this purpose, we installed ground-based monitoring boxes filled with clean quartz sand at different distances (1, 2, and 4 m) from the road. Mass-specific magnetic susceptibility (χ), heavy metal (HM) contents, and polycyclic aromatic hydrocarbon (PAH) concentrations all showed decreasing values with distance to the roadside. The temporal variations over 2 years of monitoring reveal an overall increasing trend but differences in depth migration due to seasonal effects (i.e., precipitation). A magnetite-like phase turned out to be responsible for the enhancement of χ. Significant positive correlations between χ and total PAHs as well as HMs for the German sites suggest that χ—which can be measured fast and convenient—can be used as a proxy for traffic-derived PAH and HM pollution. However, in the much drier region of Lanzhou, the relationship of χ with HMs is much weaker, which might be caused by specific materials used in road construction and heavy vehicles. From the obtained results, we conclude that an appropriate roadside monitoring procedure based on magnetic signatures should best use a single thin (1–2 cm) layer of clean quartz sand protected against lateral material translocation.

The surface morphology of biocathode was one of the limiting factors for microbial fuel cell (MFC) design. Up-flow membrane-less single-chambered MFC (UFML MFC) was used to investigate the effect of surface morphology of carbon material as aqueous biocathode. Pt-loaded carbon paper, carbon felt, and carbon plate were examined and compared on the power output, surface morphology for biofilm formation, Coulombic efficiency (CE), and chemical oxygen demand (COD) reduction. The COD reduction was up to 90 % in UFML MFC with Pt-loaded carbon paper, carbon felt, and carbon plate as aqueous biocathodes. The results obtained showed that the performance in voltage output was not related to internal resistance but mainly due to the ability of cathode material in oxygen reduction process. The performance of voltage output with different materials as aqueous biocathode was mainly based on to the surface morphology as it was related to the ability of biofilm formation. Roughness of aqueous biocathode’s surface morphology could prompt the biofilm growth, while biofilm overgrowth on aqueous biocathode could decrease voltage output. Therefore, smoother surface morphology of aqueous biocathode is more suitable for long-term operation.

Olive-oil production has a vital impact on the socioeconomic development in most Mediterranean countries, where 97.5 % of the world oil is produced. However, the olive-oil extraction process generates considerable quantities of an agro-industrial effluent, olive mill wastewater (OMW), which has negative impact on the environment and biological life. The objective of this study was to evaluate the potential use of OMW treated by different technologies in irrigation and determine its effect on the plant growth and soil quality parameters. Different technologies were used to treat the OMW, the resultant treated OMW was used to irrigate the maize planted in the pot experiment. The results indicated that UOMW increased soil salinity and reduced plant growth, while the treated OMW by different technologies improved plant growth and resulted in lower soil pH. The impact on other soil properties varied depending on the techniques used for treatments. Although treated OMW enhanced plant growth compared with the untreated, the plant growth remained lower than that obtained using the potable water with fertilizers, indicating lack of some essential plant nutrients.

Global warming and pollution are the twin crises experienced globally. Biological offset of these crises are gaining importance because of its zero waste production and the ability of the organisms to thrive under extreme or polluted condition. In this context, this review highlights the recent developments in carbon dioxide (CO₂) capture from flue gas using microalgae and finding the best microalgal remediation strategy through contrast and comparison of different strategies. Different flue gas microalgal remediation strategies discussed are as follows: (i) Flue gas to CO₂ gas segregation using adsorbents for microalgal mitigation, (ii) CO₂ separation from flue gas using absorbents and later regeneration for microalgal mitigation, (iii) Flue gas to liquid conversion for direct microalgal mitigation, and (iv) direct flue gas mitigation using microalgae. This work also studies the economic feasibility of microalgal production. The study discloses that the direct convening of flue gas with high carbon dioxide content, into microalgal system is cost-effective.

Agricultural practices are the main source of water contamination in rural areas. Rainfall events, and subsequently, soil leaching and storm runoff are mainly controlling the transfer of pollutants from diffuse sources in watersheds during floods. These periods are also very important to better understand their dynamics, particularly their different soil-river transfer pathways (surface runoff SR, subsurface runoff SSR, and groundwater flow GF). This study focuses on riverine transfers of both pesticides and trace elements. High-resolution monitoring of water discharge and water sampling were performed during a flood event that occured in May 2010 in an agricultural catchment of SW France. Chemical composition of major and trace elements, silica, alkalinity, pH and conductivity, DOC and POC, TSM, and commonly used pesticides were analyzed with a high sampling frequency. The different stream flow components (SR, SSR, and GF) were assessed using two independent hydrograph separation methods: a hydrological approach based on Maillet’s formula (1905) for the recession period and a chemical approach based on physico-chemical tracers, TSM for SR and PO₄³⁻ for GF. Both methods exhibited important contributions of SR (33 %) and SSR (40 %) to the total riverine pollutant transfers. The contribution of different components was also visible using concentration-discharge relationships which exhibited hysteresis phenomenon between the rising and the falling limbs of the hydrograph. Higher concentrations during the rising period (clockwise hysteresis) were characteristic of pollutants mainly exported by SR (trifluralin, Cd). Anticlockwise hysteresis with higher concentration during the recession period showed pollutants mainly exported by SSR (metolachlor, Cu). Moreover, significant relationships were highlighted between the controlling factors (DOC, POC, and TSM) and SR, SSR, and GF contributions: DOC and the complexed pollutants were highly correlated to SSR while POC, TSM, and the adsorbed pollutants were linked to SR. During the flood, K d of most pollutants increased, particularly at the beginning, and therefore, future studies should investigate their availability to living organisms and thus their toxicity. An additional characteristic equation between K d and K ₒw of the different pesticides was proposed to help future management, modelling, and estimation of pollutant transfers during floods.