The effects of using reprocessable material on the durability and mechanical properties of landfill leachate collection HDPE pipes

This paper investigated the durability and mechanical properties of landfill leachate collection HDPE pipes which had been made of different weight percent amounts of virgin and reprocessable HDPE compounds (VC and RC). Durability is reported base on the chemical properties, obtained through oxidative induction time (OIT) and melt flow index (MFI) measurements, at the temperature of 50 °C and over a period of 12 months immersion in a synthetic leachate. Mechanical properties are also described according to tensile and pressure tests which had been conducted on the pipes samples. All of the factors were examined had been affected by the addition of RC, but for the special combination the antioxidant depletion was significantly affected by the experimental aging condition and no important changes had been observed in the other pipe properties. The results from OIT tests indicate that the rate of antioxidant depletion is reduced by an increase in the weight percent amounts of RC, during the experimental aging condition. This reduction is probably attributed to the extraction of antioxidants from RC in their recovery process. Finally, although these results are related to the particular HDPE compound, antioxidant formulation and condition examined, but it can be said that the use of clean own reprocessable material for the production of landfill leachate pipes shall be permitted without limitations.     

Nitrogen fertility and abiotic stresses management in cotton crop: a review

This review outlines nitrogen (N) responses in crop production and potential management decisions to ameliorate abiotic stresses for better crop production. N is a primary constituent of the nucleotides and proteins that are essential for life. Production and application of N fertilizers consume huge amounts of energy, and excess is detrimental to the environment. Therefore, increasing plant N use efficiency (NUE) is important for the development of sustainable agriculture. NUE has a key role in crop yield and can be enhanced by controlling loss of fertilizers by application of humic acid and natural polymers (hydrogels), having high water-holding capacity which can improve plant performance under field conditions. Abiotic stresses such as waterlogging, drought, heat, and salinity are the major limitations for successful crop production. Therefore, integrated management approaches such as addition of aminoethoxyvinylglycine (AVG), the film antitranspirant (di-1-p-menthene and pinolene) nutrients, hydrogels, and phytohormones may provide novel approaches to improve plant tolerance against abiotic stress-induced damage. Moreover, for plant breeders and molecular biologists, it is a challenge to develop cotton cultivars that can tolerate plant abiotic stresses while having high potential NUE for the future.     

Soil carbon and nitrogen dynamics in the first year following herbicide and scalping in a revegetation trial in south-east Queensland,Australia

During revegetation, the maintenance of soil carbon (C) pools and nitrogen (N) availability is considered essential for soil fertility and this study aimed to evaluate contrasting methods of site preparation (herbicide and scalping) with respect to the effects on soil organic matter (SOM) during the critical early establishment phase. Soil total C (TC), total N (TN), hot-water extractable organic C (HWEOC), hot-water extractable total N (HWETN), microbial biomass C and N (MBC and MBN), total inorganic N (TIN) and potentially mineralizable N (PMN) were measured over 53 weeks. MBC and MBN were the only variables affected by herbicide application. Scalping caused an immediate reduction in all variables, and the values remained low without any sign of recovery for the period of the study. The impact of scalping on HWETN and TIN lasted 22 weeks and stabilised afterwards. MBC and MBN were affected by both herbicide and scalping after initial treatment application and remained lower than control during the period of the study but did not decrease over time. While scalping had an inevitable impact on all soil properties that were measured, that impact did not worsen over time, and actually improved plant growth (unpublished data) while reducing site establishment costs. Therefore, it provides a useful alternative for weed control in revegetation projects where it is applied only once at site establishment and where SOM would be expected to recover as canopy closure is obtained and nutrient cycling through litterfall commences.     

Seasonal variation of pharmaceutically active compounds in surface (Tagus River) and tap water (Central Spain)

Numerous studies have shown the presence of pharmaceutically active compounds (PhACs) in different environmental compartments, for example, in surface water or wastewater ranging from nanograms per litre to micrograms per litre. Likewise, some recent studies have pointed to seasonal variability, thus indicating that PhAcs concentrations in the aquatic environment may depend on the time of year. This work intended to find out (1) whether Tagus fluvial and drinking water were polluted with different groups of PhACs and (2) if their concentrations differed between winter and summer seasons. From the 58 substances analysed, 41 were found belonging to the main therapeutic groups. Statistical differences were seen for antibacterials, antidepressants, anxiolytics, antiepileptics, and cardiovascular drugs, with higher concentrations being detected in winter than in summer. These results might indicate that the PhACs analysed in this study undergo lower environmental degradation in winter than in summer. In order to confirm these initial results, a continuous monitoring should be performed especially on those PhACs that either because of an elevated consumption or an intrinsic chemical persistence are poorly degraded during winter months due to low temperatures and solar irradiation. It is especially important to identify which of these specific PhACs are in order to recommend their substitution by equally effective and safe substances but also environmentally friendly.     

Laboratory scale studies on removal of chromium from industrial wastes

Chromium being one of the major toxic pollutants is discharged from electroplating and chrome tanning processes and is also found in the effluents of dyes,paint pigments,manufacturing units etc.Chromium exists in aqueous systems in both trivalent(Cr^3 )and hexavalent (Cr^6 )forms.The hexavalent form is carcinogenic and toxic to aquatic life,whereas Cr^3 is however comparatively less toxic.This study was undertaken to investigate the total chromium removal from industial effluents by chemical means in order to achieve the Pakistan NEQS level of 1 mg/L by the methods of reduction and precipitation.The study was conducted in four phase Ⅰ,the optimum pH and cost effective reducing agent among the four popular commercial chemicals was selected.As a result,pH of 2 was found to be most suitable and sodium meta bisulfate was found to be the most cost effective reducing agent respectively.Phase Ⅱ showed that lower dose of sodium meta hisulfate was sufficient to obtain 100% efficiency in reducing Cr^6 to Cr^3 ,and it was noted that reaction time had no significance in the whole process.A design curve for reduction process was established which can act as a tool for treatment of industrial effluents.Phase Ⅲ studies indicated the best pH was 8.5 for precipitation of Cr^3 to chromium hydroxide by using lime.An efficiency of 100% was achievable and a settling time of 30 minutes produced clear effluent.Finally in Phase Ⅳ actual waste samples from chrome tanning and electroplating industries,when precipitated at pH of 12 gave 100% efficiency at a settling time of 30 minutes and confirmed that chemical means of reduction and precipitation is a feasible and viable solution for treating chromium wastes from industries.     

Characteristics of biotic and abiotic removals of dissolved organic carbon in wastewater effluents using soil batch reactors.

Biodegradable dissolved organic carbon (BDOC) analyses and abiotic adsorption of dissolved organic carbon (DOC) from different wastewater effluent were conducted to evaluate biotic and abiotic removal mechanisms as a function of the initial DOC concentration and source of DOC using soil batch reactors. To obtain high DOC concentrations, a laboratory-scale reverse osmosis unit was used. It was found that BDOC fraction was independent of the initial DOC concentration and was dependent on the source of wastewater and/or the types of wastewater treatment. The BDOC fractions varied from 9 to 73%. Trickling filter effluent (Tucson, Arizona) showed the highest BDOC, ranging from 65 to 73% biodegradable, while wastewater treated by the soil aquifer treatment (SAT) (NW-4) was found to be most refractory, with DOC removals of 9 to 14%. For nitrified/denitrified tertiary effluent (Mesa, Arizona) and secondary effluent (Scottsdale, Arizona), 36 to 42% removal of DOC was observed during the BDOC test. The amount of BDOC in the wastewater depended not on the concentration of DOC, but on the effectiveness of pretreatment. Abiotic adsorption capacity of wastewater effluent varied from 6 to 18%. Molecular weight distribution analyses showed that more than 50% of DOC in the Scottsdale concentrate had a molecular weight of less than 1000 Da, and no significant change in distribution profiles occurred after approximately 12% abiotic adsorption with both soils with acclimated microorganisms (SAT soil) and soils without acclimated microorganisms (non-SAT soils). Hence, preferential adsorption was not observed and the presence of acclimated microbes did not influence adsorption.     

Applications of nanomaterials in water treatment and environmental remediation

Nanotechnology has revolutionized plethora of scientific and technological fields; environmental safety is no exception. One of the most promising and well- developed environmental applications of nanotechnology has been in water remediation and treatment where different nanomaterials can help purify water through different mechanisms including adsorption of heavy metals and other pollutants, removal and inactivation of patho- gens and transformation of toxic materials into less toxic compounds. For this purpose, nanomaterials have been produced in different shapes, integrated into various composites and functionalized with active components. Nanomaterials have also been incorporated in nanostructured catalytic membranes which can in turn help enhance water treatment. In this article, we have provided a succinct review of the most common and popular nanomaterials （titania, carbon nanotubes （CNTs）, zero-valent iron, dendrimers and silver nanomaterials） which are currently used in environmental remediation and particularly in water purification. The catalytic properties and functionalities of the mentioned materials have also been discussed.     

Improved power density and Cr/Pb removal using ozone in a microbial desalination cell

Environmental Chemistry Letters - Microbial desalination cells are promising bio-electrochemical technologies for water desalination, treating wastewater and bioelectricity production. In this...