Removal of chromium from synthetic plating waste by zero-valent iron and sulfate-reducing bacteria.

Experiments were conducted to evaluate the potential of zero-valent iron and sulfate-reducing bacteria (SRB) for reduction and removal of chromium from synthetic electroplating waste. The zero-valent iron shows promising results as a reductant of hexavalent chromium (Cr+6) to trivalent chromium (Cr+3), capable of 100% reduction. The required iron concentration was a function of chromium concentration in the waste stream. Removal of Cr+3 by adsorption or precipitation on iron leads to complete removal of chromium from the waste and was a slower process than the reduction of Cr+6. Presence SRB in a completely mixed batch reactor inhibited the reduction of Cr+6. In a fixed-bed column reactor, SRB enhanced chromium removal and showed promising results for the treatment of wastes with low chromium concentrations. It is proposed that, for waste with high chromium concentration, zero-valent iron is an efficient reductant and can be used for reduction of Cr+6. For low chromium concentrations, a SRB augmented zero-valent iron and sand column is capable of removing chromium completely.     

Sludge age, stability, and safety factor for the biofilm-activated sludge process reactor

The average sludge age (theta(c)) of the activated sludge process (ASP)-biofilm were developed and verified experimentally. In addition, the stability and safety factor were investigated against theta(c). through a series of curves. These curves are important to explain, in concept, the function of the hybrid system under different values of theta(c). The proposed curves of this study are simple and can be modified for any specified wastewater. The definition of theta(c) of ASP was found to be applicable to the hybrid system after including the biofilm. A ratio ranging from 70 to 80% of the total mass of biofilm may be used in the definition of theta(c). to give close results with the experimental values. Furthermore, the minimum sludge age (theta(c)(M)) does not exist in the hybrid reactor because of the presence of biofilm; however, theta(c) should come down to a critical value under some specific conditions of the reactor.     

Accumulation and translocation of heavy metals in soil and plants from fly ash contaminated area

The present investigation deals with the accumulation of heavy metals in fields contaminated with fly ash from a thermal power plant and subsequent uptake in different parts of naturally grown plants. Results revealed that in the contaminated site, the mean level of all the metals (Cd, Zn, Cr, Pb, Cu, Ni, Mn and Fe) in soil and different parts (root and shoots) of plant species were found to be significantly (p<0.01) higher than the uncontaminated site. The enrichment factor (EF) of these metals in contaminated soil was found to be in the sequence of Cd (2.33) > Fe (1.88) > Ni (1.58) > Pb (1.42) > Zn (1.31) > Mn (1.27) > Cr (1.11) > Cu (1.10). Whereas, enrichment factor of metals in root and shoot parts, were found to be in the order of Cd (7.56) > Fe (4.75) > Zn (2.79) > Ni (2.22) > Cu (1.69) > Mn (1.53) > Pb (1.31) > Cr (1.02) and Cd (6.06) approximately equal Fe (6.06) > Zn (2.65) > Ni (2.57) > Mn (2.19) > Cu (1.58) > Pb (1.37) > Cr (1.01) respectively. In contaminated site, translocation factor (TF) of metals from root to shoot was found to be in the order of Mn (1.38) > Fe (1.27) > Pb (1.03) > Ni (0.94) > Zn (0.85) > Cd (0.82) > Cr (0.73) and that of the metals Cd with Cr, Cu, Mn, Fe; Cr with Pb, Mn, Fe and Pb with Fe were found to be significantly correlated. The present findings provide us a clue for the selection of plant species, which show natural resistance against toxic metals and are efficient metal accumulators.     

Vermistabilization and nutrient enhancement of anaerobic digestate through earthworm species Perionyx excavatus and Perionyx sansibaricus

The aim of the study was to examine safe reuse and recycling of organic waste digestate obtained from a biogas plant (5 % total solid) with enhanced nutrient value through vermitechnology. Two indigenous epigeic earthworm species Perionyx excavates and Perionyx sansibaricus were tried individually for this purpose. The results clearly show a significant increase in pH values from 6.5–7.4, electrical conductivity (21.3–21.7 %), total N (84.5–94.6 %), total P (35.9–47.1 %), total K (49.8–52.6 %), Ca (41.9–41.9 %) and a significant decrease in total organic C (17.1–22.4 %), C/N ratio (7.2–6.9), C/P ratio (20.3–20.6), COD (51.9–55.7 %), BOD (85.5–91.2 %). Similarly, indicator organisms (fecal coliforms and fecal streptococci) showed decrement at the end of the composting period (60 days). Fecal Coliforms reduce to nil, while in fecal streptococci a 6 log reduction was observed. Oxygen uptake rate dropped to 67.4–70 % for vermireactors. Overall, the aforementioned findings highlighted that the indigenous earthworm species could enhance the nutrient value of the anaerobic digestate, which could be utilized as an efficient soil conditioner.     

Pharmacological evaluation of Thuja occidentalis for the attenuation of neuropathy via AGEs and TNF-α inhibition in diabetic neuropathic rats

Environmental Science and Pollution Research - When diabetes neuropathy occurs, the oxidative stress caused by chronic hyperglycemia may result in chronic neuronal damage. To mitigate the effects...     

Simplified DO sag models for rapid BOD removal

Predictive models for dissolved oxygen deficit have been developed based on an exponential form of expression for the equivalent linear removal of the settleable component of biochemical oxygen demand. These models are more convenient to use than other models because they are applicable for any distance from the outfall and for point and non-point wastewater discharge conditions.     

Environmental impact of noise levels in and around opencast bauxite mine

Until recently, noise pollution has not been paid adequate attention as air, water and land pollution. In order to assess (predict) the impact of bauxite mine noise on employees health and in and around bauxite mine environment, general noise sources and equipment noise were monitored. All these noise sources were compared with prescribed standard noise levels laid down by Central Pollution Control Board (CPCB). Data has also been compared with reference site, north block hill top which is barren and virgin plateau/top covered with grass only and free from human interference. Equipment noise levels were much higher than the other zone of the mine which does not have the corresponding standards. Rock breaker recorded the highest noise level with 73.1 +/- 14.2 to 89.5 +/- 10.1 dB (A) while from ripper dozer it was least with 61.0 +/- 17.3 to 76.2 +/- 6.2 dB (A). Meteorological parameters did not have much influence upon equipment noise up to 100 feet from the source.     

Towards environmentally sustainable industrialization: a case study of some mini iron and steel industries in India

Summary Iron and steel have been used in India since ancient times (possibly as early as 5000 BC). There are several references to the use of iron and steel in the Vedic literatures. The rust and corrosionfree iron pillar of Qutub Minar in Delhi, built 1500 years ago and the steel girders used in the temples of Orissa around AD 700–1200 still bear the testimony of these early industries. Steels are in great demand today but the large steel plants provide a limited range of steel mostly consumed in building and construction activities. In India, heavy machine tools, locomotives, automobiles, aviation, ship building and engineering tools require super grade steels with various specifications and these are met by mini iron and steel industrial plants. There are approximately 160 such plants mostly situated in big cities and towns. There are several economic and ecological advantages of these mini steel plants. They mostly use iron and steel scrap and other kinds of iron wastes from large industries as their raw material, contrary to the large plants which use iron ores as primary raw materials, the extraction processing and utilization of which involves severe environmental damage by way of deforestation and air and water pollution. Mini steel plants consume much less water and energy. The government of India has given a number of incentives to the mini steel industries by way of exemption from income tax, custom and excise duties, depreciation and investment allowances and rebates on charges for consumption of water and electricity.Dr Rajiv K. Sinha is an assistant professor in human ecology at the University of Rajasthan. Mr V.N. Bhargava is an engineer employed at the Research and Development Division of National Engineering Industries, Khatipura Road, Jaipur 302006, India.     

Effects of adsorbent dose and size on phosphate-removal from wastewaters

Laboratory scale production of rinsed tamarind nutshell activated carbon (TNSAC) was done by the method of single stage chemical activation, with zinc chloride as an activation agent. Using this adsorbent, adsorption studies were conducted in agitated batch flow reactors with a fixed initial phosphate concentration and with varying adsorbent particle sizes and doses, The highest percentages adsorbed, for an adsorbent dose of 4 g litre(-1), were 57% and 44%, respectively, for adsorbent particle sizes of 106.1 microm and 232.4 microm. Two different models have been developed for predicting the percentage of phosphates adsorbed. Both models manifested high coefficients of correlation, indicating their robustness. The adsorption isotherms developed were observed to resemble the form of Freundlich isotherms. A generalized model has been developed for predicting the adsorptive capacity with respect to the stated test conditions. This model exhibited good coefficients of correlation.     

Synthesis of graphitic carbon nitride/cadmium sulfide core-shell nanofibers for enhanced photocatalysis

Environmental Science and Pollution Research - The synthesis of graphitic carbon nitride/cadmium sulfide core-shell nanofibers has been studied for the improved photodegradation of methylene blue...