Removal of Heavy Metal Ions by Waste Biomass of Saccharomyces Cerevisiae

The kinetics, equilibriums, and thermodynamics of metal ion (Pb2+, Ag2+, Cu2+, Zn2+, Co2+, Sr2+, and Cs+) biosorption by the waste yeast cells of Saccharomyces cerevisiae from a local brewery were investigated. The results showed that the biosorption of these metal ions on the biomass was a very rapid process, following the pseudo-second-order equation gave the better fitting results in describing the kinetic data than the pseudo-first-order equation. The equilibrium data could be fitted well with the Langmuir model. The maximum sorption capacity obtained from the Langmuir model followed Pb>Ag>Cu>Zn>Co>Sr>Cs (based on mmol?g?1). The biosorption process by the yeast was favorable for these metal ions removal according to the constant separation factor (0相似文献   

Heavy Metal Biosorption Properties of Four Harvested Macrophytes

The biosorption mechanism of metal removal [copper (Cu) and zinc (Zn)] by four phytoremediation macrophytes biomasses including sunflower (Helianthus annuus), Chinese cabbage (Brassica campestris), cattail (Typha latifolia), and reed (Phragmites communis), was investigated in this study. The primary objective was exploring the potential of reusing these biowfastes after harvesting from phytoremediation operations. Based on the surface area, zeta potential, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) investigations, Chinese cabbage biomass presented the highest metal adsorption property whereas both cattail and reed revealed a lower adsorption capability for both metals tested. The equilibrium adsorption rate between biomass and metal occurred very fast during the first 10?min. The metal adsorption data were fitted with the Langmuir and Freundlich isotherms and presented that the Langmuir isotherm was the best fitted model for all biomass tested. All tested biomasses are fast-growing plants with fairly high biomass production that are able to accumulate metals. The Langmuir model was used to calculate maximum adsorption capacity and related adsorption parameters in this study. The results revealed that the maximum metal adsorption capacity Qmax? was in the following order: Chinese cabbage (Cu:2000;Zn:1111??mg/kg)>sunflower?(Cu:1482;Zn:769??mg/kg)>reed?(Cu:238;Zn:161??mg/kg)>cattail?(Cu:200;Zn:133??mg/kg). The harvested sunflower, Chinese cabbage, cattail, and reed biomass can potentially be employed as biosorbents to remove Cu and Zn from aqueous solutions. Adsorption isotherms derived in this study may provide crucial information for practical design and operation of adsorption engineering processes, and prediction of relation between reused macrophyte biosorbents and heavy metal adsorbates.     

Storm-Water Bioretention for Runoff Quality and Quantity Mitigation

In response to water quality and quantity issues within the Stroubles Creek watershed in Blacksburg, Virginia, a retrofit bioretention cell (BRC) was installed to collect and treat runoff from an existing parking lot. The BRC was completed in July 2007, and 28 precipitation events were monitored between October 2007 and June 2008. For each storm, inflow and outflow flow-weighted composite samples were collected and analyzed for suspended sediment, total nitrogen, and total phosphorus. The inflow and outflow concentrations and loads, as well as total inflow and outflow volumes and peak flow rates, were analyzed to evaluate BRC efficiency. Overall, the BRC successfully reduced flow volumes and peak flow rates leaving the parking lot by 97 and 99%, respectively. Cumulative mass reductions for sediment, total nitrogen, and total phosphorus all exceeded 99% by mass. The findings of this study have significant implications for areas with karst geology: (1)?current design recommendations of lining the bottom of BRCs with clay may not be sufficient to prevent large amounts of water from infiltrating into surrounding soils; and (2)?in areas with significant elevation changes, designing BRCs deeper than the typical 0.6–1.2?m increases the feasibility of retrofits and provides substantial water quality and quantity benefits.     

Storm Water Detention Ponds: Modeling Heavy Metal Removal by Plant Species and Sediments

Laboratory and field studies were conducted to elucidate heavy metal removal by three wetland grasses and sediments in storm water detention pond. The removal of heavy metals including Cd, Cu, Pb, and Zn was mediated by fluid-flow intensity in the reactors. The growth of plants and the removal rates of contaminants were plant species dependent. All three wetland grasses removed contaminants from the spiked nutrient solutions. A first-order kinetic model adequately represented the removal of contaminants by plants. The analyses of undisturbed sediment cores in detention pond revealed strong stratification of heavy metal concentrations at the sediment–water interface. A simple model that integrates heavy metal removal by aquatic plants and sediments in storm water detention ponds is proposed. The model provides an estimate of contaminant residence time which can be related to hydraulic residence time in storm water detention ponds.     

On Parameter Estimation of Urban Storm-Water Runoff Model

An existing accumulation and wash-off model was applied and calibrated on a standard asphalt parking lot located in the northeastern United States. The field measured data consisted of rainfall, flow, and runoff samples taken from over 26 storm events monitored from 2004 to 2006. The contaminants under consideration include: total suspended solids, total petroleum hydrocarbons-diesel range hydrocarbons (TPH-D), dissolved inorganic nitrogen (DIN) (comprised of nitrate, nitrite, and ammonia), and zinc (Zn). The objective of the study was to provide probability distributions of model parameters for contaminants that have not been documented much (TPH-D, DIN, and Zn). The best fitting parameter values were found on a storm by storm basis. Subsequently, the range and variability of these parameters are provided for modeling purposes and other urban storm-water quality applications. A normal distribution was fitted to the optimized model parameter values to describe their distributions. A simulated annealing algorithm was used as the parameter optimization technique. Several examples are given to illustrate the methodology and the performance of the model. Finally, a Monte Carlo simulation was performed to assess the capability of the model to predict contaminant concentrations at the watershed’s outlet.     

Selective Removal of Heavy Metals from Industrial Wastewater Using Maghemite Nanoparticle: Performance and Mechanisms

This study investigated the applicability of maghemite (γ-Fe2O3) nanoparticles for the selective removal of toxic heavy metals from electroplating wastewater. The maghemite nanoparticles of 10?nm were synthesized using a sol–gel method and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The surface area of the nanoparticles was determined to be 198?m2/g using the Brunauer–Emmett–Teller method. Batch experiments were carried out to determine the adsorption kinetics and mechanisms of Cr(VI), Cu(II), and Ni(II) by maghemite nanoparticles. The adsorption process was found to be highly pH dependent, which made the nanoparticles selectively adsorb these three metals from wastewater. The adsorption of heavy metals reached equilibrium rapidly within 10?min and the adsorption data were well fitted with the Langmuir isotherm. Regeneration studies indicated that the maghemite nanoparticles undergoing successive adsorption–desorption processes retained original metal removal capacity. Mechanism studies using TEM, XRD, and X-ray photoelectron spectroscopy suggested that the adsorption of Cr(VI) and Cu(II) could be due to electrostatic attraction and ion exchange, and the adsorption of Ni(II) could be as a result of electrostatic attraction only.     

Characterizing Physicochemical Quality of Storm-Water Runoff from an Urban Area in Calgary, Alberta

Understanding storm-water runoff quality is required to develop effective urban storm-water runoff management for regions of semiarid climate. In this study, the quality of storm-water runoff from a semiarid, urban residential catchment, draining through separated storm-water sewers was investigated in 2006 and 2007. Water temperature, conductivity, pH, dissolved oxygen, and turbidity were continuously measured during 16 storm events. Storm-water runoff quality was characterized in terms of event mean values (EMVs), loads, and first flush (FF) loads and their relationships with rainfall characteristics. Discharge of total suspended solids (TSSs) is in general governed by the flow magnitude in storms and no significant relationships exist between the FF loads of TSS and rainfall intensity. The discharge of dissolved solids is independent of the flow magnitude. Strong FF effect for dissolved solids and weak FF effect for TSS were observed. This semiarid region provided no relationship between the EMVs of both TSS and conductivity and the antecedent dry period. This raises doubts on storm-water runoff being more heavily loaded with pollutants after a longer dry period in semiarid regions.     

Orthophosphate Adsorption Equilibrium and Breakthrough on Filtration Media for Storm-Water Runoff Treatment

Total phosphorus (TP) in storm-water runoff is a common regulatory target for maintaining the quality of receiving surface water. Previous storm-water treatment studies show that it is difficult to consistently achieve TP removal higher than 40%, whereas regulatory goals of 50–65% removal are becoming common. To meet these goals, storm-water filtration technologies utilizing an expanding array of filtration media are being deployed, especially in areas with protected water bodies such as Puget Sound and Chesapeake Bay. One challenge is that if the media has no adsorption capacity, particulate phosphorus can redissolve into solution and form liberal orthophosphate (Ortho-P), resulting in lower overall TP removal. Therefore, effective Ortho-P adsorption capacity in filtration media is crucial to meet more stringent TP removal goals. Additional media characteristics that should be considered include gradation, permeability, surface area, morphology, cost, and toxicity. In response to these requirements, an engineered media (EM) was developed and evaluated by Ortho-P adsorption isotherms and breakthrough in typical storm-water runoff conditions. Three other media, perlite, zeolite, and granular activated carbon (GAC), widely used in storm-water treatment, were also investigated under the same experimental conditions. With adsorption isotherms, EM showed the highest adsorption capacity of 7.82??mg/g, nearly seven times that of GAC (1.16??mg/g). In adsorption breakthrough testing, overall removal efficiency decreases as the number of treated empty bed volumes (EBVs) increases. To reach 50% overall removal, EM provided 838 EBVs, whereas GAC could only treat 12 EBVs. In addition, for the lifetime of media, EM outlasted GAC with 2,297 EBVs, compared to 1,000 EBVs, respectively. Results indicate that EM is an adsorptive filtration media for treating storm-water phosphorus.     

Parametric Evaluation of Batch Equilibria for Storm-Water Phosphorus Adsorption on Aluminum Oxide Media

Elevated and variable aqueous and granulometric concentrations of phosphate species (P) are commonly observed in urban rainfall runoff. Though physical operations such as sedimentation can potentially separate particulate P, aqueous P requires a unit process approach such as adsorption. Therefore, adsorption of aqueous P on aluminum oxide coated media (AOCM), a porous soil-type substrate coated with aluminum oxide, is investigated. Parameters studied include media size, phosphate concentration as total dissolved phosphorus (0–25 mg/L), pH (5–9), ionic strength (0.000?5–0.2 M as KCl), and the presence of coexisting ions such as Ca2+, SO42?, and NO31?. Results indicate that adsorption (mg/g) increased with decreasing AOCM size and decreasing pH. Ca2+ enhanced P adsorption by forming ternary complexes; SO42? inhibited P adsorption by competing for available adsorption sites. Ionic strength and NO31? had minor to negligible effects on adsorption equilibrium, respectively. Chemical adsorption between P and AOCM resulted in low desorption potential. Adsorption data were modeled with Freundlich isotherms. After batch adsorption by AOCM, results indicate that P could be significantly reduced, meeting most surface water discharge requirements.     

Pollutant Mass Flushing Characterization of Highway Stormwater Runoff from an Ultra-Urban Area

Water quality of highway stormwater runoff from an ultra-urban area was characterized by determining the event mean concentration (EMC) for several pollutants and by evaluating pollutant flushing. Thirty-two storm events were monitored between June 2002 and October 2003. Mean EMCs in mg/L were 0.035, 0.11, 0.22, 1.18, 420, 3.4, 0.14, 1.0, and 0.56 for Cd, Cu, Pb, Zn, total suspended solids (TSS), total Kjeldahl nitrogen (TKN), NO2–N, NO3–N, and TP. First flush as defined by flushing of 50% of the total pollutant mass load in the first 25% of the event runoff volume occurred in 33% of the storm events for NO2?, 27% for TP, 22% for NO3? and TKN, 21% for Cu, 17% for TSS, 14% for Zn, and 13% for Pb. Median values for the mass flushed in the first 25% of runoff volume were greater than the mass flushed in any 25% portion beyond the first for all pollutants. The mass in later 25% volume portions were greater than in the first 25% volume in at least 17% of the events for all pollutants, indicating that a significant amount of the pollutant load can be contained in later portions of the runoff volume. Nonetheless, management of the first 1.3?mm (1/2?in.) of runoff was able to capture 81–86% of the total pollutant mass.     

Prediction of Effluent Quality from Retention Ponds and Constructed Wetlands for Managing Bacterial Stressors in Storm-Water Runoff

Microbial indicator organisms make up the greatest number of reported receiving water impairments, resulting in many questions on the fate of indicator bacteria passing through storm-water best management practices (BMPs). Storm-water BMPs are often considered effective tools to mitigate the effects of urbanization on receiving waters. The USEPA’s, Office of Research and Development investigated the processes occurring within two commonly used BMPs, constructed wetlands and retention ponds. This research focused on creating pilot-scale systems to determine the environmental mechanisms that affect effluent indicator bacteria concentrations and to provide better information for the prediction of bacterial indicators for models when developing and meeting total maximum daily loads. Research results indicate water temperature, light, and a combination of other environmental factors influence bacteria indicator concentrations. Results from this research suggest that both constructed wetlands and retention ponds lower microbial concentrations in urban storm-water runoff. Bacteria inactivation generally followed the first-order, KC* model, which includes irreducible or background concentrations of a stressor. Sediment analyses indicate bacteria accumulated in sediments which may maintain background concentrations could be reintroduced into the effluent of these BMPs by turbulent flow causing resuspension or by accumulation through lack of maintenance. First-order models that do not consider irreducible concentrations may underestimate actual bacterial concentrations. The relationship between turbidity and bacteria suggests storm-water management practices that substantially reduce turbidity may also provide the greatest improvement in reducing concentrations of bacteria in storm-water runoff.     

Effect of Roof Surface Type on Storm-Water Runoff from Full-Scale Roofs in a Temperate Climate

Roof surfaces represent a significant portion of the impervious area associated with urban development. Storm-water runoff from those surfaces causes stream degradation in receiving waters attributable to excess volume of water runoff. This paper investigates the influence of roof surface type on storm-water runoff and specifically considers the benefits of a vegetated roof, or green roof, as a storm-water best management practice (BMP). Runoff data were collected over a 6-month period from three full-scale roofs, which were retrofitted with flow meters and automated water-quality samplers. The roof surfaces included an asphalt roof (for control purposes), a vegetated extensive green roof, and a stone ballasted roof. Both the green roof and stone roof were effective at reducing runoff volume and attenuating peak discharge, with the green roof being more efficient for rainfall events less than 2.54?cm. Overall, the green roof retained 68.25% of rainfall volume and reduced peak discharge by an average of 88.86%. Water-quality results were inconclusive, but did provide some indication that green roof systems could reduce nutrient loadings.     

Metal Contamination Characteristics of Lepidium sativum in a Phosphate-, Saline-, and Nitrate-Contaminated Media

In this research we investigated the ability of cress seeds (Lepidium sativum L.) to grow in an aqueous media with metal toxicities. The toxicity of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn ions were examined in blank, nitrate (N–NO3)–, phosphate (KH2PO4)–, and saline (NaCl)–contaminated media. The acute toxicity of the tested metal ions in the blank media according to their IC50 (50% inhibitory concentration) values increased on the order of Pb相似文献   

New Approach: Waste Materials as Sorbents for Arsenic Removal from Water

The sorption of inorganic arsenic species (arsenite and arsenate) from aqueous solutions onto steel-mill waste and waste filter sand, under neutral conditions, was investigated in this study. Additionally, the steel-mill waste material was modified in order to minimize its deteriorating impact on the initial water quality and to meet the drinking water standards. The influence of contact time and initial arsenic concentration was investigated using batch system techniques. To evaluate the application for real groundwater treatment, the capacities of the obtained waste materials were further compared to those exhibited by commercial sorbents, which were examined under the same experimental conditions. Kinetic studies revealed that waste slag materials are the most efficient in arsenic removal, reaching equilibrium arsenic sorption capacities in the range 47.6–55.2?μg/g, while waste filter sand exhibited capacities of 25.4–29.8?μg/g (for an initial arsenic concentration Co = 0.5?mg/L). The higher iron content in the slag materials was considered to be responsible for the better removal efficiencies, and the specific arsenic removal efficiency was estimated to be 220?μgAs/gFe. The specific arsenic removal efficiency of the second active substance found in waste filter sand, manganese, was estimated to be 115?μgAs/gMn. Equilibrium studies revealed the occurrence of both chemisorption and physical sorption processes. All the waste materials exhibited higher performances for As(V). The highest maximum sorption capacity was obtained by waste iron slag: 4040?μg/g for As(V). The waste materials reached the arsenic removal capacities of the examined commercial materials, suggesting the feasibility of their application in real groundwater treatment.     

Use of Phosphate Rock for the Removal of Ni2+ from Aqueous Solutions: Kinetic and Thermodynamics Studies

A study was carried out in batch conditions to examine the removal of nickel ions from an aqueous solution by phosphate rock. The effect of different sorption parameters, such as initial metal concentration, equilibration time, solution pH, and temperature on the amount of Ni2+ sorbed was studied and discussed. The sorption process followed pseudo-second-order kinetics with necessary time of 2?h to reach equilibrium. The maximum removal obtained is at initial pH around 8. Nickel uptake was quantitatively evaluated using the Langmuir and Dubinin–Kaganer–Radushkevich model. The Langmuir adsorption isotherm constant corresponding to adsorption capacity, Q0, was found to be 7.63?mg/g. The possibility of metal recovery was investigated using several eluting agents. The desorbed amount of nickel decreased continuously with increasing pH, and increased with increasing Ca2+ concentration in leaching solution.     

Heavy Metal and PAH Concentrations in Highway Runoff Deposits Fractionated on Settling Velocities

The correlation between settling velocity and associated pollutant concentrations is of major importance for best management practice in designing, redesigning, or evaluation of the efficiency of existing pond facilities for retaining unwanted pollutants. The prospect of this note is to state the relationship between the settling velocity of the runoff particles and the corresponding metal and polyaromatic hydrocarbon (PAH) concentration directly instead of dealing with two unknowns—the density and the shape of a single particle fraction in a settling velocity calculations. The measurements show that the highest cadmium, chromium, zinc, and nickel concentrations is associated with the most slowly falling particles and the lowest concentration associated within the faster falling fraction. This tendency is not clear for some of the sediments due to high content of organic matter and clearly not for lead and copper and there is no significant correlation between PAH concentration and settling velocity. The largest mass of metals and PAH within each pond can be found on the particle fraction with a settling velocity of 5.5–2.5 mm/s.     

Removal of Heavy Metals from Automotive Wastewater by Sulfide Precipitation

The United States Environmental Protection Agency has proposed new categorical pretreatment effluent standards for the Metal Products and Machinery Industry, which are more stringent than current discharge limits in the automotive industry. Therefore, this study was conducted to evaluate metal-sulfide precipitation chemistry as an alternative to metal-hydroxide precipitation chemistry for removing Cu, Ni, Pb, and Zn. There were three aspects of this study: (1) theoretical analysis of both metal–hydroxide and metal–sulfide chemistry; (2) experimental evaluation of commercially available sulfur-containing precipitants using deionized water; and (3) experimental evaluation of the precipitants using wastewater samples from three automotive manufacturing plants (transmission, engine, and assembly plants). The primary findings are: (1) In theory, metal–hydroxide chemistry can achieve the proposed standards when no chelating agents are present. This is not true when as small as 1 mg/L of ethylenediaminetetra-acetic acid (EDTA) is present. (2) Metal–sulfide precipitation chemistry could achieve solubility limits lower than those of metal–hydroxide chemistry over a wide range of pH. However, EDTA could still inhibit precipitation of Ni, Pb, and Zn to concentrations above the proposed standards. (3) The experiments with wastewater samples showed all precipitants removed Cu well while Ni and Zn were not well removed. The sample from transmission and engine plants were more difficult to treat than from an assembly plant, suggesting that it might have had more chelating agents. The commercially available precipitants did not perform any better than sodium sulfide. (4) Costs for using the precipitants were estimated to range from <$1/1,000 gal to >$5/1,000 gal depending on the precipitant.     

Trace Metal Pollutant Load in Urban Runoff from a Southern California Watershed

In order to implement efficient and effective management strategies for coastal water quality in Southern California, it is important to consider the relative pollutant contributions from urban dry-weather flow (DWF) and wet-weather flow (WWF). This study uses both historical flow coupled with water quality monitoring data and computer modeling to characterize the annual DWF and WWF discharges from an urban catchment in Los Angeles, Calif. The DWF and WWF pollutant loading of the trace metals copper, lead, nickel, and chromium for 6 water years dating from 1991 to 1996 is predicted. The results indicate that DWF contributes a considerable amount of flow and pollutants. Approximately, 9–25% of the total annual Ballona Creek flow volume is DWF. The simulations indicate DWF accounts for 54, 19, 33, and 44% of the average annual load of total chromium, copper, lead, and nickel, respectively. In the dry season, the simulations indicate DWF accounts for 89, 59, 58, and 90% of the load of total chromium, copper, lead, and nickel, respectively. This research suggests DWF controls may be an important part of pollution mitigation plans for urban stormwater drainage systems in Southern California.     

Modeling Flow and Pollutant Removal of Wet Detention Pond Treating Stormwater Runoff

A mathematical model of pollutant removal by wet ponds was developed based on the mass balance principle and the release–storage equation. The release–storage equation can be linear or nonlinear depending on the wet pond shape and the spillway crest features. If the exponent index of the storage relationship (d) is equal to the index of the outflow equation (b), the wet pond hydrological routing model is linear. Otherwise, the model is nonlinear. Substituting the release–storage equation into the continuity equation produces a nonlinear ordinary differential equation (ODE). A Runge–Kutta method was used to solve the resulting nonlinear ODE. When the ratio of indexes d/b = 2/3, the hydrologic wet pond model reduces to a special case that leads to an implicit analytical solution. The pollutant removal and flow routing models were tested with data obtained from an actual wet pond for treating highway runoff. The predicted flow discharges and pollutant concentrations compared well with the observed data.     

Field Study of the Ability of Two Grassed Bioretention Cells to Reduce Storm-Water Runoff Pollution

Two grassed bioretention cells including internal storage zones (ISZs) were monitored for 16?months in central North Carolina. Each cell had a surface area of 106?m2 and fill media depths were 0.75 and 1.05?m for the north (North) and the south (South) cells, respectively. Asphalt parking lot inflow and outflows were analyzed for nitrogen and phosphorus forms and fecal coliform (FC). Outflow volumes and peak flows for individual storms were generally less than those of inflow. Overall, except for NO2,3–N, effluent nitrogen species event mean concentrations (EMCs) and loads were significantly (α = 0.05) lower than those of the inflow, and nitrogen species load reductions ranged from 47 to 88%. Apart from fall and winter, during which a longer hydraulic contact time seemed to be needed, the ISZs appeared to improve denitrification. Total phosphorus (TP) and OPO4-P EMCs were significantly lower than those of the inlet. Reductions were 58% (South) and 63% (North) for TP and 78% (North) and 74% (South) for OPO4–P. There was no significant difference in TP and OPO4–P loads between the inlet and the two outlets. Moreover, effluent concentrations for both phosphorus species were low, relative to other studies. The best nutrient EMC and load reductions occurred during the warm and humid seasons. When considering effluent concentrations in addition to removal rates, the grassed cells showed promising results for FC and nutrient pollution abatement when compared to conventionally vegetated bioretention (trees, shrubs, and mulch) previously studied in North Carolina.