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.

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.

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.

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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.