This study investigates the occurrence and sources of fecal contamination along the Texas Gulf Coast, focusing on two barrier islands: Sargent Beach and Matagorda Peninsula. Surface water samples from six sites were c...
详细信息
Levels of total organic hallde (TOX) in a Kraft mill wastewater ranged from 26,000 to 60,000 g/l. An aerated stabilization basin (ASB) proved capable of removing one-third to one-half of both the total TOX as well as ...
详细信息
Levels of total organic hallde (TOX) in a Kraft mill wastewater ranged from 26,000 to 60,000 g/l. An aerated stabilization basin (ASB) proved capable of removing one-third to one-half of both the total TOX as well as lower molecular weight (
Differences in the nature of soluble organic matter were measured for various full-scale wastewater treatment processes. Conventional activated sludge, pure oxygen activated sludge, biofiltration, granular activated c...
详细信息
Differences in the nature of soluble organic matter were measured for various full-scale wastewater treatment processes. Conventional activated sludge, pure oxygen activated sludge, biofiltration, granular activated carbon, and tertiary sand filtration were evaluated. Effluent soluble organic matter was analyzed by ultrafiltration for the apparent molecular weight distribution of soluble organic carbon and UV-absorbing material. The effects of annual season, secondary treatment process, and tertiary treatment process upon the properties of the effluent soluble organic matter were statistically significant at the 99% level. Effluent properties from the various treatments were sufficiently different to support the concept of the selection of appropriate treatments to minimize the effluent concentration of specific fractions of the soluble organic material as required for specific water reuse applications.
The degradation of trichloroethylene (TCE), chloroform (CF), and 1,2-dichloroethane (1,2-DCA) by four aerobic mixed cultures (methane, propane, toluene, and phenol oxidizers) grown under similar chemostat conditions w...
详细信息
The degradation of trichloroethylene (TCE), chloroform (CF), and 1,2-dichloroethane (1,2-DCA) by four aerobic mixed cultures (methane, propane, toluene, and phenol oxidizers) grown under similar chemostat conditions was measured. Methane and propane oxidizers were capable of degrading both saturated and unsaturated chlorinated organics (TCE, CF, and 1,2-DCA). Toluene and phenol oxidizers degraded TCE but were not able to degrade CF, 1,2-DCA, or other saturated organics. None of the cultures tested were able to degrade perchloroethylene (PCE) or carbon tetrachloride (CCl4). For the four cultures tested, degradation of each of the chlorinated organics resulted in cell inactivation due to product toxicity. In all cases, the toxic products were rapidly depleted, leaving no toxic residues in solution. Among the four tested cultures, the resting cells of methane oxidizers exhibited the highest transformation capacities (T-c) for TCE, CF, and 1,2-DCA. The T-c for each chlorinated organic was observed to be inversely proportional to the chlorine carbon ratio (Cl/C). The addition of low concentrations of growth substrate or some catabolic intermediates enhanced TCE transformation capacities and degradation rates, presumably due to the regeneration of reducing energy (NADH);however, addition of higher concentrations of most amendments reduced TCE transformation capacities and degradation rates. Reducing energy limitations and amendment toxicity may significantly affect T-c measurements, causing a masking of the toxicity associated with chlorinated organic degradation. (C) 1995 John Wiley and Sons, Inc.
Ceramic membranes have emerged as a promising solution for microfiltration processes, offering advantages such as cost-effectiveness, environmental benefits, and the utilization of abundant raw materials derived from ...
详细信息
Nets, screens, and filters are used to sieve out particles larger than the pore sizes. However, during separation a significant fraction of particles smaller than the pore diameters will also be removed by collision a...
详细信息
Nets, screens, and filters are used to sieve out particles larger than the pore sizes. However, during separation a significant fraction of particles smaller than the pore diameters will also be removed by collision and adhesion to the mesh fibers. Two filtration models were used to predict the size and mass distributions of particles during size separation. A capillary tube model was used to calculate particle removal by different screens, and a fibrous filter model was used for glass-fiber filters. The extent of particle removal was modeled assuming a size distribution of 3,100 particles evenly distributed at logarithmic intervals over 31 size classes ranging from 0.1 to 100 mum. As many as 8% of the particles and 50% of the total particle mass could be retained by a 210-mum (pore diam) mesh even though all particles were < 100 mum. This high retention of particles implies that when size distributions are prepared with screens and filters, the mass concentration in smaller size fractions will be considerably underestimated.
Contamination of aquatic and terrestrial organisms by Perfluoroalkyl substances (PFAS), emerging contaminants, is widespread, as these compounds are present in water, soil, air, and food, owing to their environmental ...
详细信息
Five filtration models were used to predict the effect of particle size on removal in several types of laboratory filters (nylon, cellulose and glass fiber). All, models predicted similar trends in removal with partic...
详细信息
Five filtration models were used to predict the effect of particle size on removal in several types of laboratory filters (nylon, cellulose and glass fiber). All, models predicted similar trends in removal with particle size, although the capillary-pore model predicted substantially lower removals than the other four fibrous filtration models. These models indicated that bacterium-size (approximately 1 mum) particles are removed in filters primarily through the filtration mechanism of particle interception. Based on advertised pore sizes, removal of bacterium-size particles was a function of filter material in the order cellulose > nylon > glass fiber. The percent of bacteria removed in a nylon filter (5 mum pore diameter) was similar to removal in GF/C filters (1.2 mum pore diameter) as a result of a higher sticking coefficient of bacteria with nylon than with glass. The average sticking coefficients of three bacteria, Pseudomonas sp. JS6, Pseudomonas fluorescens P17 and Bacillus pumilus, in glass fiber (GF/C) filters, were 0.01, 0.24 and 0.20, respectively. These results indicate that filtration models can be used to describe particle removal during laboratory filtration of water and wastewater samples, and that bacteria have relatively high sticking coefficients for filter materials.
Fiber-reinforced self-compacting concrete(FRSCC)is a typical construction material,and its compressive strength(CS)is a critical mechanical property that must be adequately *** the machine learning(ML)approach to esti...
详细信息
Fiber-reinforced self-compacting concrete(FRSCC)is a typical construction material,and its compressive strength(CS)is a critical mechanical property that must be adequately *** the machine learning(ML)approach to estimating the CS of FRSCC,the current research gaps include the limitations of samples in databases,the applicability constraints of models owing to limited mixture components,and the possibility of applying recently proposed *** study developed different ML models for predicting the CS of FRSCC to address these *** neural network,random forest,and categorical gradient boosting(CatBoost)models were optimized to derive the best predictive model with the aid of a 10-fold cross-validation technique.A database of 381 samples was created,representing the most significant FRSCC dataset compared with previous studies,and it was used for model *** findings indicated that CatBoost outperformed the other two models with excellent predictive abilities(root mean square error of 2.639 MPa,mean absolute error of 1.669 MPa,and coefficient of determination of 0.986 for the test dataset).Finally,a sensitivity analysis using a partial dependence plot was conducted to obtain a thorough understanding of the effect of each input variable on the predicted CS of *** results showed that the cement content,testing age,and superplasticizer content are the most critical factors affecting the CS.
The degradation of concrete structure in the marine environment is often related to chloride-induced corrosion of reinforcement ***,the chloride concentration in concrete is a vital parameter for estimating the corros...
详细信息
The degradation of concrete structure in the marine environment is often related to chloride-induced corrosion of reinforcement ***,the chloride concentration in concrete is a vital parameter for estimating the corrosion level of reinforcement *** research aims at predicting the chloride content in concrete using three hybrid models of gradient boosting(GB),artificial neural network(ANN),and random forest(RF)in combination with particle swarm optimization(PSO).The input variables for modeling include exposure condition,water/binder ratio(W/B),cement content,silica fume,time exposure,and depth of *** results indicate that three models performed well with high accuracy of prediction(R2⩾0.90).Among three hybrid models,the model using GB_PSO achieved the highest prediction accuracy(R2=0.9551,RMSE=0.0327,and MAE=0.0181).Based on the results of sensitivity analysis using SHapley Additive exPlanation(SHAP)and partial dependence plots 1D(PDP-1D),it was found that the exposure condition and depth of measurement were the two most vital variables affecting the prediction of chloride *** the number of different exposure conditions is larger than two,the exposure significantly impacted the chloride content of concrete because the chloride ion ingress is affected by both chemical and physical *** study provides an insight into the evaluation and prediction of the chloride content of concrete in the marine environment.
暂无评论