Use of rubber and bentonite added fly ash as a liner material

In many countries regulations require all hazardous waste disposal facilities to be lined with suitable impermeable barriers to protect against contamination. In this study, a series of laboratory tests on rubber and bentonite added fly ash were conducted. The aim of the tests was to evaluate the feasibility of utilizing fly ash, rubber and bentonite as a low hydraulic conductivity liner material. Type C fly ash was obtained from Soma thermal power plant in Turkey; rubber in pulverized form was waste from the retreading industry. To investigate the properties of rubber and bentonite added fly ash, hydraulic conductivity, leachate analysis, unconfined compression, split tensile strength, one-dimensional consolidation, swell and freeze/thaw cycle tests were performed. The overall evaluation of results have revealed that rubber and bentonite added fly ash showed good promise and a candidate for construction of a liner.     

Subcritical water oxidation of propham by H2O2 using response surface methodology (RSM)

This study was conducted to investigate the degradation of propham, which is a compound that pollutes water and seriously threatens human health, by subcritical water oxidation and using H₂O₂ as an oxidising agent. The maximum total organic carbon removal rate of propham was obtained as 73.65% at 40 min of treatment time and 60 mM of H₂O₂ concentration and 373 K of temperature. In addition, response surface method based on the Box-Behnken design was applied to design the degradation experiments of propham for determination of the combined effects of process variables, namely temperature, concentration of oxidising agent and treatment time. The proposed quadratic model of propham degradation, which was examined with the analysis of variance, was used for navigating the design space. The R² and adjusted R² values of the model were determined as 0.9921 and 0.9819 respectively. It was shown that propham was effectively degraded, thus could be removed from the water by using an environmentally friendly method.     

Generation pattern of sulfur containing gases from anaerobically digested sludge cakes.

Eleven dewatered sludge cakes collected from anaerobic digesters at different treatment plants were evaluated for the amount, type, and pattern of odorous gas production. All but one of the sludge cakes were from mesophilic anaerobic digesters. One was from a thermophilic digester. The pattern and quantities of sulfur gases were found to be unique for each of the samples with regard to the products produced, magnitude, and subsequent decline. The main odor-causing chemicals were volatile sulfur compounds, which included hydrogen sulfide, methanethiol, and dimethyl sulfide. Volatile sulfur compound production peaked in 3 to 8 days and then declined. The decline was a result of conversion of organic sulfur compounds to sulfide. In one side-by-side test, a high-solids centrifuge cake generated more odorous compounds than the low-solids centrifuge cake. The data show that anaerobic digestion does not eliminate the odor potential of anaerobically digested dewatered cakes.     

The relationship between carbon dioxide emission and crop and livestock production indexes: a dynamic common correlated effects approach

Rapid increase in carbon dioxide emission triggers climate change, while climate change poses a threat to food security. On the other hand, emission increase as a result of agricultural production continues. Considering this cycle, it is thought that examining the relationship between agricultural production and carbon dioxide emissions can help countries take emission-reducing measures and develop policies to ensure food safety. With this thought, a common correlated effect estimator was used in this study to explain the relationship between crop and livestock production index and carbon dioxide emission of 184 countries with the use of data for the period of 1998–2014. Countries were classified under four categories: low-income countries, lower middle–income countries, upper middle–income countries and high-income countries. According to DCCE test results, it was reported that a 1% increase in crop production index had effect on CO₂ emission only in lower middle–income countries. A 1% increase in livestock production index, on the other hand, was reported to increase CO₂ emission rates by 0.28, 0.49, and 0.39 in lower middle–income, upper middle–income, and high-income countries, respectively. When evaluated in general, it could be stated that livestock breeding has a higher effect on CO₂ emission in agricultural production. The findings of the present study revealed that countries need to improve agricultural production methods in ways to minimize the positive association between vegetative and livestock production in accordance with their level of development, to adopt more environment-friendly agricultural technologies and to endorse international environmental policies.

     

Evaluation of non-carcinogenic health risks of thallium in grapevine exposed to mine waters of an abandoned mining region in Turkey

Environment, Development and Sustainability - In this study, non-carcinogenic health risks of thallium in grapevine exposed to mine waters of an abandoned mining region in Turkey were evaluated....     

Immobilization of radioactive waste by cementation with purified kaolin clay

A study is undertaken to determine the waste immobilization performance of low-level wastes in cement-clay mixtures. Liquid low-level wastes are precipitated using chemical methods, followed by solidification in drums. Solidification is done using cementation processes. Long-term leaching rates of the radionuclides are used as indicators of immobilization performance of solidified waste forms. In addition to evaluating the effects of kaolin clay on the leaching properties of the cemented waste forms, the effect of addition of kaolin on the strength of the cemented waste form is also investigated. The long term leaching tests show that inclusion of kaolin in cement reduces the leaching rates of the radionuclides significantly. However, clay additions in excess of 15 wt.% causes a significant decrease in the hydrolytic stability of cemented waste form. It is found that the best waste isolation, without causing a loss in the mechanical strength, is obtained when the kaolin content in cement is 5%.     

The mechanism of enhanced biological phosphorus removal washout and temperature relationships.

In this study, the combined effects of temperature and solids retention time (SRT) on enhanced biological phosphorus removal (EBPR) performance and the mechanism of EBPR washout were investigated. Two pilot-scale University of Cape Town (South Africa) systems fed with synthetic wastewater were operated at 5 and 10 degrees C. The results showed that the phosphorus removal performance was optimum at total SRT ranges of 16 to 24 days and 12 to 17 days for 5 and 10 degrees C, respectively, and steady-state phosphorus removal was greater at the lower temperature. Higher SRT values of up to 32 days at 5 degrees C and 25 days at 10 degrees C slightly reduced EBPR performance as a result of increased extent of endogenous respiration, which consumed internally stored glycogen, leaving less reducing power for poly-hydroxy alkanoate (PHA) formation in anaerobic stages. The phosphorus-accumulating organism (PAO) washout SRTs of the systems were determined as 3.5 days at 5 degrees C and 1.8 days at 10 degrees C, considerably less than the washout SRTs of nitrifiers. Polyphosphorus, the main energy reserve of the EBPR bacterial consortium, was not completely depleted, even at washout points. The inability of EBPR biomass to use glycogen to generate reducing power for PHA formation was the major reason for washout. The results not only suggest that glycogen mechanism is the most rate-limiting step in EBPR systems, but also that it is an integral part of EBPR biochemistry, as proposed originally by Mino et al. (1987), and later others (Pereira et al., 1996, Erdal et al., 2002; Erdal, Z. K., 2002). The aerobic washout SRT values (2.1 and 1.2 days for 5 and 10 degrees C, respectively) of this study did not fit the linear line for PAO washout developed by Mamais and Jenkins (1992). Perhaps this was because the feeds used during this study were chemical-oxygen-demand-limited (acetate-based synthetic feed), whereas the feeds used for their study were phosphorus-limited (external acetate added to domestic wastewater), resulting in different ratios of PAOs and nonPAOs in the biomass.     

Role of protein, amino acids, and enzyme activity on odor production from anaerobically digested and dewatered biosolids.

The main objective of this research was to test the hypothesis that bioavailable protein and, more specifically, the sulfur-containing amino acids within the protein, can be degraded by proteolytic enzymes to produce odor-causing compounds--mainly volatile sulfur compounds (VSCs)--during biosolids storage. To achieve these objectives, samples of digester effluent and cake solids were collected at 11 different wastewater treatment plants in North America, and the samples were analyzed for protein and amino acid content and general protein-degrading enzyme activity. At the same time, cake samples were stored using headspace bottles, the concentration of VSCs were measured using gas chromatography, and olfactometry measurements were made by a trained odor panel. The results showed that the bound cake protein content and methionine content was well-correlated with VSC production and the detection threshold measured by the odor panel.     

Demolition of high-rise public housing increases particulate matter air pollution in communities of high-risk asthmatics

Public housing developments across the United States are being demolished, potentially increasing local concentrations of particulate matter (PM) in communities with high burdens of severe asthma. Little is known about the impact of demolition on local air quality. At three public housing developments in Chicago, IL, PM with an aerodynamic diameter < 10 microm (PM10) and < 2.5 microm were measured before and during high-rise demolition. Additionally, size-selective sampling and real-time monitoring were concurrently performed upwind and downwind of one demolition site. The concentration of particulates attributable to demolition was estimated after accounting for background urban air pollution. Particle microscopy was performed on a small number of samples. Substantial increases of PM10 occurred during demolition, with the magnitude of that increase varying based on sampler distance, wind direction, and averaging time. During structural demolition, local concentrations of PM10 42 m downwind of a demolition site increased 4- to 9-fold above upwind concentrations (6-hr averaging time). After adjusting for background PM10, the presence of dusty conditions was associated with a 74% increase in PM10 100 m downwind of demolition sites (24-hr averaging times). During structural demolition, short-term peaks in real-time PM10 (30-sec averaging time) occasionally exceeded 500 microg/m(3). The median particle size downwind of a demolition site (17.3 microm) was significantly larger than background (3 microm). Specific activities are associated with realtime particulate measures. Microscopy did not identify asbestos or high concentrations of mold spores. In conclusion, individuals living near sites of public housing demolition are at risk for exposure to high particulate concentrations. This increase is characterized by relatively large particles and high short-term peaks in PM concentration.