Carcinogenic risks and chemical composition of particulate matter recovered by two methods: wet and dry extraction

Wet and dry extraction methods are two main methods used in toxicological in vitro and in vivo studies to recover particulate matter (PM) from filter papers. The aim of this study was to extract PM by wet and dry extraction methods and compare the elemental content and carcinogenic risks of extracts. PM10 samples were collected using fiberglass filters and a high-volume air sampler. For wet extraction, the method involved agitation in water, sonication in water bath, and agitation again. For dry extraction, the filters were sonicated and the PM was recovered using sweeping by a brush. Elemental composition of extracts was determined by inductively coupled plasma-optical emission spectrometry (ICP-OES). Excess lifetime cancer risks (ELCR) of As, Cd, Cr, Ni, and Pb in extracts were estimated. The average recovery efficiency () of dry and wet extraction methods were 36.8 and 58.5, respectively. The average elemental concentration that resulted from dry and wet methods was calculated to be 2.27 and 1.26 μg/m3, respectively. The total ELCR of all heavy metals in both methods exceeds the 1 � 10�6 limit. However, the total ELCR of heavy metals that resulted from the dry method was higher than that from the wet method. In conclusion, the dry method showed to be more effective to recover a representative extract from the filter. This can ultimately lead to a realistic and robust response in toxicological studies. However, a toxicological comparison between the extracts of these two methods is required. © 2020, Springer Nature Switzerland AG

Degradation and toxicity reduction of phenol by ultrasound waves

The effects of parameters such as pH, kinetic constants and initial phenol concentration on the sonochemical degradation of phenol and toxicity assay were studied. The experimental results showed that lower pH and lower concentration of phenol favor the phenol degradation. But the rates of phenol degradation under sonication have always been quite low. It is found that the rate of ultrasonic degradation of phenol for initial concentration of 1 mg/L is 0.018 min-1 but later it reduces with increasing of phenol initial concentration substantially and the experimental data fitted well with pseudo first-order reaction rate equation. Bioassay tests showed that phenol was toxic to Daphnia magna and so resulted in quite low LC50 values. Comparison of toxicity units (TU) between phenol and effluent toxicity showed that the TU value for effluent was 1.21 times lower than that obtained for phenol solely. Thus, the toxicity of metabolites formed during the degradation of phenol is lower than the toxicity of phenol itself. KEY WORDS: Phenol, Ultrasound, Sonochemistry, Toxicity assay  Bull. Chem. Soc. Ethiop. 2007, 21(1), 33-38

Heavy metals (Cd, Cu, Ni and Pb) content in two fish species of Persian Gulf in Bushehr Port, Iran

Heavy metal (HMs) pollution of aquatic environment has become a great concern in recent years. In this study, cadmium (Cd), copper (Cu), nickel (Ni) and lead (Pb) levels were determined in muscle and skin of two important consumed fishes (Indo-Pacific king mackerel and Tigertooth croaker) in Bushehr Province in the Southwestern of Iran. Heavy metal concentrations were analyzed by using inductively coupled plasma (ICP). The mean contents of metal, expressed in mg/kg wet weight, varied from 0.17 to 0.26 for Cd, 1.25 to 1.84 for Cu, 0.6 to 0.84 for Ni and 0.31 to 0.7 for Pb. Results showed that the highest and lowest contents of heavy metals in muscle and skin of both fish samples were related to Cu and Cd concentration, respectively, and heavy metal contents in both skin fish samples and muscle of Tigertooth croaker were found to decrease in sequence as Cu>Pb>Ni>Cd.Key words: Heavy metal, fish, Bushehr, Iran

Feasibility study of organic matter and Ammonium removal using loofa sponge as a supporting medium in an aerated submerged fixed-film reactor (ASFFR)

Biofilm systems are efficient in the removal of organic matter and ammonium from wastewaters. In this study, loofa sponge, a natural product, was used as a supporting medium in an aerated submerged fixed-film reactor to evaluate its performance in removing organic matter and nitrogen from wastewater. Four pilot runs were performed with chemical oxygen demand (COD) concentrations of 100, 200, 300 and 400 mg l-1 to provide an organic loading rate of 0.6, 1.2, 1.8, and 2.4 kg m-3d-1 respectively. In these pilot runs, the influent ammonium nitrogen concentrations were justified to 5, 10, 15 and 20 mg l-1 as N to provide an influent nitrogen loading of 30, 60, 90 and 120 g m-3.d-1 respectively. Although soluble COD removal efficiency greater than 80 percent was achieved up to a loading rate of 2.4 kg m-3d-1, loofa deformation and clogging after 72 days of application might be considered a serious shortcoming during use in full-scale applications. Nitrogen removal efficiency decreased from 85.6% at an organic loading rate of 0.6 kg m-3d-1 to 56.1% at an organic loading rate of 2.4 kg m-3d-1

Technical and economic investigation of chemical scrubber and bio-filtration in removal of H 2 S and NH 3 from wastewater treatment plant

A detailed techno-economic comparison of a chemical scrubber (CS) and a bio-filter (BF) was conducted over a 45-day time period at a municipal wastewater treatment plant (WWTP), Yazd city. The assessment of emissions quantity indicated that odor emissions from the Yazd WWPT mainly consist of hydrogen sulfide (H 2 S) and ammonia (NH 3 ). It was also found that odor gaseous loading changes corresponding to water consumption pattern in society (R 2 = 0.922) for H 2 S and (R 2 = 0.978) for NH 3 . The highest level of 25 and 3 ppm for H 2 S and NH 3 , respectively were detected at specific times during the day. The BF system was continuously supplied with Yazd WWPT's off-gas treatment while the CS was only examined at the times during the day when the gas emissions are at the highest level. The removal efficiency of NH 3 and H 2 S were found to be affected by their respective loading rate. Additionally, among the various oxidants examined in the CS, the NaOCl solution showed the best results in terms of removal efficiency and compatibility. The experiment revealed almost complete removal of NH 3 while the H 2 S removal efficiency remained above 95 for both systems regardless of the operating conditions. This study clearly demonstrates the effectiveness of both systems in treating actual waste gases containing H 2 S and NH 3 . By comparing the gas loading rate of both systems and considering limitations of the BF system, the CS seems to be more efficient applicable odor control technology from a technical viewpoint. From the economic viewpoint, comparisons revealed that chemical usage and operating expenses were costly parts of the CS and the BF, respectively. The economic indexes of 1.58 �.m �3 . h �1 and 2.57 �.m �3 . h �1 were obtained for the BF and CS, respectively, reflecting cost-effectiveness of the BF system. © 201