a b s t r a c tRelease of nitrogen and phosphorus into effluent of activated sludge process was reported in the recent researches of sludge reduction induced by oligochaetes. In this study, batch test and radioisotope 32 P tracer test were therefore carried out to further investigate nutrients release and phosphorus distribution among supernatant, sludge and worm during predation of oligochaetes on sludge. Results showed that more nutrients release into supernatant occurred in the tests of worms with sterilized sludge than that of worms with activated sludge, and release of nitrogen and phosphorus was few in the tests of worms with activated sludge. Statistical analysis showed that no factor was significantly correlated with phosphorus concentration in the supernatant, but time and worm were only two factors significantly affecting total nitrogen (TN) concentration in the supernatant in the test of worms with activated sludge. Through test of radioisotope 32 P tracer, 32 P mainly distributed in activated sludge and supernatant, and more release of 32 P into the supernatant occurred in the test of sludge with worms. After 24 h, 32 P concentration of supernatant in the test of sludge with worms was 9% higher than that in the test of sludge without worms, and 32 P concentration of worm increased by 2.7%. Additionally, the release rate of phosphorus into supernatant caused by worm's predation on activated sludge was 0.1211 mgTP/gWorm (wet weight) h.
A quantitative structure property relationship (QSPR) study was performed in this work to develop models for predicting reaction rate constants for reductive debromination of polybrominated diphenyl ethers (PBDEs) by zero-valent iron (ZVI). Both multiple linear regression (MLR) and artificial neural network (ANN) methods were employed for QSPR studies based on the experimental kinetic data of the fourteen PBDE congeners. Both the developed MLR and ANN models could give satisfactory prediction abilities, and the performance of the ANN model seems slightly better than that of the MLR model. In addition, energy of lowest unoccupied molecular orbital (ELUMO) and total energy (TE) were found to be the two relatively important variables in the ANN model via the assessment using both the Garson’s algorithm and connection weight approach.
The concentration of ammonia nitrogen in a slaughterhouse wastewater sample was determined using Nessler's reagent spectrophotometry with four different pretreatment approaches. Comparison of the results shows that the concentrations increased in the following order: coagulation sedimentation < boric acid absorption < filtration < acidifying filtration. Boric acid absorption method is more favorable, and standard curve method (SCM) should be considered superior to standard addition method (SAM) in the present research.
The quantitative structure property relationship (QSPR) study was performed in this work to develop models to predict the normalized reaction rate constants for the reductive debromination of polybrominated diphenyl ethers (PBDEs) by zero-valent iron (ZVI). In order to consider the solvent effect, conductor-like polarizable continuum model (CPCM) was applied to optimize the geometries and obtain the molecular descriptors using the pseudopotential basis set. The prediction results with the inclusion of solvent effect are slightly better than that of the corresponding gas-phase calculations. The artificial neural network (ANN) model could be more satisfactory to predict the rate constants than the partial least squares regression (PLSR) and principal component analysis-multiple linear regression analysis (PCA-MLR) models.
Heavy metals (Hg, As, Pb, Cd, Cr, Cu) pollution in soil samples of Rosa sterilis planting areas located in Wudang District in Guiyang and Pingba County in Anshun was studied using a new evaluation theory of pollution loss rate, and following a series of methods for Rosa sterilis leaf including over standard rate, enrichment coefficient, single pollution index and comprehensive pollution index, the heavy metals pollution of the two Rosa sterilis planting areas was analyzed and evaluated. The results showed that the soil comprehensive pollution loss rate ranged from 12.73% to 28.26% in Wudang District samples, most of which belong to light pollution level. The comprehensive soil pollution loss rate of the sampling points in Pingba County varied from 9.68% to 16.10%, which belong to fairly clean level. Meanwhile, the experimental results for the Rosa sterilis leaf showed that the contents of Cr and Pb in both planting areas exceeded the permissible limit, while other elements were below the safe limit. The six heavy metal elements in Rosa sterilis leaf did not accumulate.
Adsorption effects of three kinds of activated carbons and a type of machine-made charcoal on the removal of antimony from acidic aqueous solution were investigated and compared. With an initial antimony solution concentration of 1000 μgL-1, the antimony adsorption by selected adsorbents were found to descend in the following order: machine-made charcoal (52.4%) > coconut activated carbon (42.6%) > coal based activated carbon (31.1%) > apricot stone based activated carbon (24.6%). The machine-made charcoal has the best adsorption capacity with a maximum adsorption values of 523.76 μgL-1. Five kinetic models were used for the fitting of the process of antimony adsorption, including Elovich, parabola diffusion, second order, first order and double-constant. Results showed that parabola diffusion and double-constant rate equation were the most suitable models in describing the relationship of antimony adsorption with time in acidic aqueous solution, implying that the adsorption kinetics of the antimony by the selected adsorbents in water might be a surface diffusion. Three adsorptive capacity indicators (iodine number, methylene blue number and phenol number) were determined in this paper. However, machine-made charcoal, which has a relatively high adsorption capacity, is of the lowest levels of the adsorptive capacity indicators. Thus, some complex mechanisms might be involved for the antimony adsorption by the machine-made charcoal, consequently considering the mechanism for the adsorption of antimony by the charcoal has not been verified, a further study still needs to be done.
The affecting factors and kinetic characteristics of antimony (Sb) adsoption onto a type of the coconut shell activated carbon were investigated in this study. The results showed that: the Sb adsorption obeyed the pseudo-second-order kinetics equation, and the coefficients of determination (R2) were higher than 0.97, inferring that this process was mainly the monolayer chemical adsorption. With the reduction of the particle size, the adsorption capacity of activated carbon gradually increased. With the increase of temperature, activated carbon adsorption of antimony content increased gradually, but on the whole the temperature had a limited effect on the adsorption of activated carbon. Effect of the solution pH on antimony adsorption onto the activated carbon was mainly divided into the following two stages: with a pH value of 1 to 3, antimony removal rate was about 60%, and with a pH value of 5 to 11, the removal rate was about 20%.
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