Performance of a pilot scale up-flow septic tank for on-site decentralized treatment of residential wastewater

The aim of this research was to study the on-site anaerobic treatment of a medium-strength residential wastewater in a pilot-scale up-flow septic tank (UST). The effects of three different hydraulic retention times (HRTs) of 24, 12 and 6 h on the UST performance were investigated. The UST removed 85, 77, and 86% of biochemical oxygen demand (BOD₅), chemical oxygen demand (COD) and total suspended solids (TSS), respectively, at steady state operation and with a 24 h HRT. Decreasing the HRT to 12 and then 6 h resulted in deteriorated effluent quality and significantly reduced reactor performance. The sludge showed a high specific methanogenic activity (SMA) of 15.2 mL CH₄ g^?1 VSS d^?1 with raw wastewater substrate. The solids accumulated in the tank by the end of the experiment had a VSS/TSS of 0.57, demonstrating significant stabilization. Overall, the UST is concluded to be a technically and economically promising alternative to conventional septic tanks for the on-site decentralized treatment of residential wastewater, particularly in the rural communities of developing countries.     

Removal of hinosan from underground water using NH4Cl-modified activated carbon from rice husk

Environmental Science and Pollution Research - In the present study, NH4Cl-modified activated carbon was synthesized from rice husk and used as an adsorbent for removal of hinosan from underground...     

Revealing empirical association among ecological footprints,renewable energy consumption,real income,and financial development: a global perspective

Environmental Science and Pollution Research - This study quantifies the effect of real income, financial development, trade openness, and renewable energy consumption on the ecological footprint...     

Synthesis of Chitosan@activated Carbon Beads with Abundant Amino Groups for Capture of Cu(II) and Cd(II) from Aqueous Solutions

In this study, chitosan and bio-based activated carbon obtained from sugarcane bagasse biowaste were used for the synthesis of efficient sorbent for Cu(II) and Cd(II) ion via precipitation method. The prepared material was enriched with amino groups through grafting tetraethylenepentamine and tested for heavy metal remediation from water samples. The influence of pH was investigated showing optimum sorption at pH 6 for Cu(II) and Cd(II). Sorption tests, explained by means of the most common sorption models, evidenced that the best performances were reached pointing out the promising application of the prepared sorbent for water purification treatments: Uptake kinetics are relatively fast: the equilibrium was reached within 140 min; and the kinetic profiles were preferentially fitted by the pseudo-second order rate equation. Sorption isotherms are fitted by Langmuir equation. The sorbent showed high metal ion sorption capacity with negligible influence of ion strength. The maximum sorption capacities reached 3.44 and 2.38 mmol g^??1 for Cu(II) and Cd(II), respectively at 298 K. Thermodynamic parameters were evaluated through variation of temperature. The sorption is unfavorable at elevated temperatures. Metal ions were successfully desorbed using 1 M HNO₃ solution.     

Urinary arsenic,cadmium, manganese,nickel, and vanadium levels of schoolchildren in the vicinity of the industrialised area of Asaluyeh,Iran

Asaluyeh is one of the most heavily industrialised areas in the world where gas, petrochemical, and many downstream industries are located. This study aims to survey the biomonitoring of four metals and one metalloid in children living in the vicinity of Asaluyeh area. To do this, we analysed the creatinine-adjusted urinary levels of arsenic (As), cadmium (Cd), vanadium (V), manganese (Mn), and nickel (Ni) in 184 elementary schoolchildren (99 boys and 85 girls) living in Asaluyeh and compared them with a reference population. The comparisons were done for two seasons (spring and fall). The results showed that in the case area (Asaluyeh), the levels of As, V, Mn, and Ni were significantly higher and that of Cd was not significantly higher than the reference city for both seasons. The mean concentration of metal(loid)s in Asaluyeh (case) and Sadabad (reference) area as μg g^?1 creatinine was As 2.90 and 2.24, V 0.06 and 0.03, Mn 0.28 and 0.25, Ni 0.54 and 0.29, and Cd 0.31 and 0.28 in spring and As 3.08 and 2.28, V 0.07 and 0.03, Mn 0.30 and 0.26, Ni 0.91 and 0.30, and Cd 0.36 and 0.31 in the fall. Seasonal variations played a key role in determining urinary metal(loid) concentration, as we saw the significant level of As, Cd, V, and Ni in fall than in spring. With regard to the impact of gender on the absorption and accumulation of urinary metal(loid)s, boys showed higher levels of the studied elements, especially for As, than girls as outdoor activities are more popular among boys. Due to the values being lower than those reported in literature, more research is needed on various population groups and other exposure sources in order to judge whether living in the vicinity of the gas and petrochemical industries in Asaluyeh is a threat to nearby residents.     

Cadmium removal from Cd-contaminated soils using some natural and synthetic chelates for enhancing phytoextraction

The influence of a natural (citric acid) and two synthetic chelates (HEDTA, EGTA) on Cd phytoextraction with radish was studied. The experiment was conducted with Cd treatments including 0 (control), 5, 20, 60 and 100?mg?Cd?kg^?1 soil. When plants were fully developed, the designated HEDTA, EGTA and citric acid were applied to establish experimental treatments. Ten days after chelate applications, soil and plant samples were taken. Results indicated that synthetic chelates can considerably increase Cd concentration in soil solution compared with citric acid. Among the applied chelates, HEDTA provided more significant influences on soil solution. Cadmium concentration in both shoots and roots of radish was increased due to enhancing influence of chelate applications on Cd concentration in soil solution. Cadmium concentration in radish shoots was more than that of roots. This can be attributed to higher bioavailability and solubility of Cd in soil solution. In all treatments which received HEDTA, the cadmium concentration in both shoots and roots of radish was increased more than that of other applied chelates. Although HEDTA is more efficient in phytoextracting Cd than other chelates, due to durability of synthetic chelates toxic effects on soils, we recommend using larger amounts of light acids.     

The depositional setting of the Late Quaternary sedimentary fill in southern Bannu basin,Northwest Himalayan fold and thrust belt,Pakistan

Geostatistical variogram and inversion techniques combined with modern visualization tools have made it possible to re-model one-dimensional electrical resistivity data into two-dimensional (2D) models of the near subsurface. The resultant models are capable of extending the original interpretation of the data to depict alluvium layers as individual lithological units within the 2D space. By tuning the variogram parameters used in this approach, it is then possible to visualize individual lithofacies and geomorphological features for these lithologic units. The study re-examines an electrical resistivity dataset collected as part of a groundwater study in an area of the Bannu basin in Pakistan. Additional lithological logs from boreholes throughout the area have been combined with the existing resistivity data for calibration. Tectonic activity during the Himalayan orogeny uplifted and generated significant faulting in the rocks resulting in the formation of a depression which subsequently has been filled with clay-silt and dirty sand facies typical of lacustrine and flood plain environments. Streams arising from adjacent mountains have reworked these facies which have been eroded and replaced by gravel-sand facies along channels. It is concluded that the sediments have been deposited as prograding fan shaped bodies, flood plain, and lacustrine deposits. Clay-silt facies mark the locations of paleo depressions or lake environments, which have changed position over time due to local tectonic activity and sedimentation. The Lakki plain alluvial system has thus formed as a result of local tectonic activity with fluvial erosion and deposition characterized by coarse sediments with high electrical resistivities near the mountain ranges and fine sediments with medium to low electrical resistivities towards the basin center.     

Source identification of polycyclic aromatic hydrocarbons (PAHs) in sediment samples from the northern part of the Persian Gulf,Iran

Samples of surface sediments from the Iranian coast of the Persian Gulf were examined to determine the levels and sources of 15 polycyclic aromatic hydrocarbons (PAHs). Samples were collected from 30 sampling sites and analyzed for PAHs by gas chromatography–mass spectrometry (GC-MS). Total concentrations of PAHs ranged from 93 to 4,077 ng g^?1 dry weight. The PAH composition from 30 sampling sites was dominated by four-ring PAH compounds. Molecular indices based on the ratios of PAH concentrations were used to differentiate PAHs from pyrolitic to petrogenic and mixed origins. The results suggested that the main sources of PAHs in sediments from the studied region were mixed pyrolitic and petrogenic. Furthermore, benthic organisms in most of the investigated areas were not at ecotoxicological risk, according to the results from the effects range low (ERL)/effects range median (ERM) techniques suggested by the US Sediment Quality Guidelines (SQGs).     

Investigation on diazinon and oxydemeton-methyl residues in cucumbers grown in Kerman greenhouses

Pesticides are considered as the most polluting substances. The residue of pesticides in agricultural crops, especially in greenhouse harvests, has been reported critical. Cucumber, considered as a vegetable, is an agricultural product which is commonly found in the Iranian food basket. The current study aims to assess the level of diazinon and oxydemeton-methyl existing in cucumbers sampled from Kerman greenhouses. The pesticide residue was extracted by acetone and dichloromethane. The extracts were cleaned up according to the solid-phase extraction method. The pesticide residues were then determined by capillary gas chromatography with nitrogen-phosphorus detection. The recoveries were 83 and 85 %, the limit of detection was 0.028 and 0.034 mg/kg, and the limits of qualification were 0.093 and 0.113 mg/kg for diazinon and oxydemeton-methyl in cucumber samples, respectively. The median of diazinon residue was detected 0.582 mg/kg, which was 11.64 times the national maximum residue limit (MRL) (0.05 mg/kg), and the median for oxydemeton-methyl was 1.910 mg/kg, being 1.91 times the MRL (1 mg/kg).     

Beta-normal distribution in dose–response modeling and risk assessment for quantitative responses

To establish allowable daily intakes for humans from animal bioassay experiments, benchmark doses corresponding to low levels of risk have been proposed to replace the no-observed-adverse-effect level for non-cancer endpoints. When the experimental outcomes are quantal, each animal can be classified with or without the disease. The proportion of affected animals is observed as a function of dose and calculation of the benchmark dose is relatively simple. For quantitative responses, on the other hand, one method is to convert the continuous data to quantal data and proceed with benchmark dose estimation. Another method which has found more popularity (Crump, Risk Anal 15:79–89; 1995) is to fit an appropriate dose–response model to the continuous data, and directly estimate the risk and benchmark doses. The normal distribution has often been used in the past as a dose–response model. However, for non-symmetric data, the normal distribution can lead to erroneous results. Here, we propose the use of the class of beta-normal distribution and demonstrate its application in risk assessment for quantitative responses. The most important feature of this class of distributions is its generality, encompassing a wide range of distributional shapes including the normal distribution as a special case. The properties of the model are briefly discussed and risk estimates are derived based on the asymptotic properties of the maximum likelihood estimates. An example is used for illustration.