Managing physicochemical parameters in compost systems to enhance degradation of petroleum wastes from a sludge dam

Physical, chemical and biological parameters were optimized during composting to enhance degradation of oil sludge. Mixtures of oil sludge, garden soil, poultry manure and the bulking agents were co-composted in static piles of about 1 m3 on wooden pallets overlaid with nylon fibre sheets. Temperature, moisture, electrical conductivity (EC), pH, total carbon, total N, heterotrophs and respiration of compost microorganisms were monitored in each pile. Moisture was maintained at between 60 and 70% field capacity. Temperatures reached a mean of 63°C in the compost containing manure and sawdust. The C:N ratio of composts changed significantly during the composting process, reaching 100:41 (sawdust+manure) 100:39 (hay+manure) and 100:31 (woodchips+manure). Respiration of compost organisms rose from 1490 to 3850 CO2 (μg)/dwt/day in the sawdust+manure compost. Total petroleum hydrocarbons (TPH) decreased by between 52 and 66% in the composts and concentrations of selected polycyclic aromatic hydrocarbons (PAH) by between 78 and 100%. The Bacillus, Pseudomonas, Arthrobacter and Staphylococcus species were predominant in all the experiments and all temperature regimes.Keywords: Bulking agents, compost bioremediation, crude oil sludge, microorganism, polycyclic aromatic hydrocarbons (PAH), total petroleum hydrocarbons (TPH)

Students’ anxiety towards the learning of chemistry in some Ethiopian Universities

Chemistry is a human endeavor that relies on basic human qualities like creativity, insights, reasoning, and skills. It depends on habits of the mind: skepticism, tolerance of ambiguity, openness to new ideas, intellectual honesty, and curiosity. The study was thus designed to find out students’ anxiety towards the learning of chemistry, identify the factors that cause the anxiety, examine the disposition of sex towards the learning of chemistry and suggest ways to increase their taste towards the learning of the subject. Data for the study were obtained by administering a questionnaire to 300 respondents. The data obtained were analyzed using frequency counts, percentages and stanine test. The finding of the study revealed that the students, whether male or female, urban or rural based, show great anxiety towards the learning of chemistry and that the anxiety is higher in female and rural based students than male andurban based students. The cause of students’ anxiety as revealed by the study includes; redundancy of the curriculum, low awareness of career opportunities, the teachers and their teaching methods and lack of teaching aids/laboratories. [AJCE, 3(2), June 2013

What makes chemistry difficult?

According to many students, introductory chemistry is difficult. We are  investigating what makes students believe Chemistry is difficult and what can be done to overcome these difficulties. Our investigation includes an initial  Free-response survey given to approximately 100 students in an introductory chemistry course and a second survey, which was given to approximately 93 students in another semester, distilled from the  responses to the first survey. Also Department members and technical assistants (TAs) for chemistry  courses were asked to complete the second survey. Our findings show that the perceptions of the students and department members are different in terms of difficulties which students have in a chemistry course. The perceptions of teachers and TAs are mostly the same. Both students and department  members agree that student-related factors, such as scientific language literacy have the most influence on students’ successes in chemistry. [AJCE 4(2), Special Issue, May 2014

Biological degradation of oil sludge: A review of the current state of development

Oil sludge is a thick viscous mixture of sediments, water, oil and hydrocarbons, encountered during crude oil refining, cleaning of oil storage vessels and waste treatment. Polycyclic aromatic hydrocarbons (PAHs), which are components of crude oil sludge, constitute serious environmental concerns, as many of them are cytotoxic, mutagenic and potentially carcinogenic. Improper management and disposal of oil sludge causes environmental pollution. The adverse effects of oil sludge on soil ecology and fertility have been of growing interest among environmental scientist and an important consideration in the development of efficient technologies for remediation of contaminated land, with a view to making such land available for further use. Oil sludge can be treated by several methods such as physical, chemical and biological processes. The biological processes are mostly cost effective and environmentally friendly, as they are easy to design and implement, as such they are more acceptable to the public. Compost, the product of biological breakdown of organic matter is a rich source of hydrocarbon-degrading microorganisms such as bacteria and fungi. These microorganisms can degrade the oil sludge to less toxic compounds such as carbon dioxide, water and salts. Compost bioremediation, the application of composting in remediation of contaminated environment, is beginning to gain popularity among remediation scientists. The success or failure of compost bioremediation depends on a number of factors such as nutrients, pH, moisture, aeration and temperature within the compost pile. The bioavailability and biodegradability of the substrate to the degrading microorganisms also contributes to the success of the bioremediation process. This is a review on the biological remediation technologies employed in the treatment oil sludge. It further assesses the feasibility of using compost technology for the treatment of oil sludge, as a better, faster and more cost effective option.Key words: Biodegradation, bioremediation, composting, oil sludge, polycyclic aromatic hydrocarbons (PAHs)

Designing a Teacher Development Programme for improving the Content Knowledge of Grade 12 Mathematics and Science Teachers

This paper profiles a community engaged initiative that is in a form of a teacher development programme (TDP) offered by the Institute for Science and Technology Education (ISTE). The programme sought to improve grade 12 mathematics and science teachers’ content knowledge. The ISTE TDP adopts an iterative approach where feedback from participating teachers informed the planning and design of the following year’s edition. ISTE TDP is based on the teachers’ needs; conducted by facilitators who are significantly versed in the teaching and learning conditions in schools; has interactive sessions that are largely participant-centred; and takes place over 5days of 8hours each. The benefit of ISTE TDP is a capacitated community of teachers with more confidence and enthusiasm.Institute for Science and Technology Education (ISTE

Zaštitno djelovanje selenija protiv prekomjerne ekspresije apoptotskih gena povezanih s karcinomom u štakora izloženih o-krezolu

Cresols are monomethyl derivatives of phenol frequently used as solvents and intermediates in the production of disinfectants, fragrances, pesticides, dyes, and explosives, which is probably why they are widely distributed in the environment. General population may be exposed to cresols mainly through inhalation of contaminated air. In this study we evaluated the toxicological effects of o-cresol on differential gene expression profile of rat liver and prostate. Experiments were conducted on 80 male rats, 60 of which were exposed to o-cresol (1.5 g kg-1, 5 g kg-1, or 15 g kg-1) through feed for 8 weeks. Three groups of rats were supplemented with 0.1 mg kg-1 selenium (Se, in the form of, sodium selenite) in addition to o-cresol to evaluate its effectiveness against o-cresol toxicity. Control group received neither o-cresol nor Se, while one group received Se alone. Survival was similar between the exposed and control animals. Rats exposed to 15 g kg-1 of o-cresol showed a 16 % loss in body weight by the end of the study, which may have been related to o-cresol making feed unpalatable at this concentration. Liver and prostate tissue samples were collected at the end of the treatment. mRNA analysis revealed that apoptotic genes (CYP3A, COX-2, PPARγ, BAX, BCL2, AKT-1, and PKCα) related to cancer were up-regulated in liver and prostate tissues isolated from groups exposed to 5 g kg-1 and 15 g kg-1 o-cresol in comparison to control. Changes in gene expression profile were prevented when rats were supplemented with Se. The exact mechanisms underlying its protective effect remain to be clarified by future studies.Krezoli su monometilni derivati fenola koji se često rabe kao otapala te kao posrednici u proizvodnji dezinfekcijskih sredstava, mirisa, pesticida, boja i eksploziva. Otuda i njihova rasprostranjenost u okolišu. Opća je populacija izložena krezolima uglavnom putem zraka. U ovome se toksikološkom istraživanju ocijenilo djelovanje o-krezola, jednoga od tri krezolova izomera, na ekspresiju gena u tkivima jetre i prostate mužjaka štakora. Istraživanje je provedeno na 80 mužjaka, od kojih je 60 tijekom osam tjedana bilo izloženo o-krezolu (1,5 g kg-1, 5 g kg-1, odnosno 15 g kg-1) preko krmiva. Tri skupine štakora primale su uz o-krezol nadomjestak selenija u dozi od 0.1 mg kg-1 (Se, u obliku natrijeva selenita) radi ocjene njegove djelotvornosti protiv toksičnosti o-krezola. Kontrolna skupina nije primala ni o-krezol ni Se, dok je jedna skupina primala samo Se. Preživljenje je bilo podjednako u svih skupina životinja. Štakori izloženi najvišoj dozi o-krezola (15 g kg-1) imali su 16 % manju tjelesnu masu od kontrolne skupine na kraju ispitivanja, što može biti povezano s lošim okusom krmiva zbog primjese visoke doze o-krezola. S istekom osmotjednoga izlaganja o-krezolu životinje su eutanazirane te su prikupljeni uzorci tkiva jetre i prostate. Analiza m-RNA pokazala je značajno povišenu ekspresiju apoptotskih gena CYP3A, COX-2, PPARγ, BAX, BCL2, AKT-1 i PKCα, koji su povezani s nastankom karcinoma u skupinama štakora izloženim o-krezolu (5 g kg-1 i 15 g kg-1 u odnosu na kontrolu. Ova je prekomjerna ekspresija poništena u štakora koji su primali selenij. Još nisu jasni mehanizmi iza ovoga zaštitnog djelovanja, na što će odgovoriti buduća istraživanja

Spatial patterns of microbial diversity and activity in an aged creosote-contaminated site

Restoration of polluted sites via in situ bioremediation relies heavily on the indigenous microbes and their activities. Spatial heterogeneity of microbial populations, contaminants and soil chemical parameters on such sites is a major hurdle in optimizing and implementing an appropriate bioremediation regime. We performed a grid-based sampling of an aged creosote-contaminated site followed by geostatistical modelling to illustrate the spatial patterns of microbial diversity and activity and to relate these patterns to the distribution of pollutants. Spatial distribution of bacterial groups unveiled patterns of niche differentiation regulated by patchy distribution of pollutants and an east-to-west pH gradient at the studied site. Proteobacteria clearly dominated in the hot spots of creosote pollution, whereas the abundance of Actinobacteria, TM7 and Planctomycetes was considerably reduced from the hot spots. The pH preferences of proteobacterial groups dominating in pollution could be recognized by examining the order and family-level responses. Acidobacterial classes came across as generalists in hydrocarbon pollution whose spatial distribution seemed to be regulated solely by the pH gradient. Although the community evenness decreased in the heavily polluted zones, basal respiration and fluorescein diacetate hydrolysis rates were higher, indicating the adaptation of specific indigenous microbial populations to hydrocarbon pollution. Combining the information from the kriged maps of microbial and soil chemistry data provided a comprehensive understanding of the long-term impacts of creosote pollution on the subsurface microbial communities. This study also highlighted the prospect of interpreting taxa-specific spatial patterns and applying them as indicators or proxies for monitoring polluted sites