ISSN:1061-4303    

DOI:10.1002/j.1554-7531.1996.tb00169.x

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

In this study, a wetland system was created and managed to increase plant removal of influent phosphorus (P). This was accomplished by making P the most limiting nutrient, by enhancing mass transfer of P to the root surface and by harvesting the shoot biomass to regenerate the nutrient removal capacity of the wetland. A mixture of grass species that are tolerant of wet conditions (66% Reed canary grass) was grown in long (3.66‐m) and narrow (0.l‐m) troughs containing silica sand. Four replicates of three depths of sand (1.3, 2.5, and 5.1 cm) were investigated at a hydraulic loading rate between 1 500 and 1 800 m3/ha · d. Removal of P was greater than 90% in all treatments, and P was reduced from 0.480 mg/L to less than 0.001 mg/L in the 5.1‐cm‐deep sand treatment. The treatments removed approximately 40% of the influent nitrate (22 mg/L in; 13 mg/L out). Nutrient removal occurred 24 hours a day with small diurnal fluctuations. Grass was harvested biweekly by cutting to a uniform 7.6‐cm height. Comparison of the actual amount of nutrients removed in the harvested biomass with that calculated from differences between influent and effluent concentrations showed that approximately 50% of the N and approximately 80% of the P were removed from the effluent in the biweekly grass clippings.

ISSN:1061-4303    

DOI:10.2175/106143096X127839

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

A key element in establishing efficient reactor designs for wastewater treatment is the ability to define, collectively rather than individually, the kinetic and mechanistic roles of numerous components in wastewater. One approach to resolve this complex problem is to consolidate the experimental data. Traditionally, the design and operation of waste treatment processes have relied on the use of lumped parameters, such as biochemical oxygen demand, chemical oxygen demand, total organic carbon, and total Kjeldahl nitrogen. In doing so, lumping has proven to be a practical tool for kinetic modeling. With the advent of theoretical foundations for kinetic lumping developed in the 1960s, there has been a growing interest in applying this methodology for modeling multicomponent mixtures. As an example, kinetic lumping was first successfully used for modeling the refining of complex hydrocarbon mixtures. These mathematical tools and proven lumping strategies are now available to systematically explore the use of lumped kinetic models for wastewater treatment systems. This study has demonstrated that existing kinetic lumping strategies can be adapted for modeling wastewater treatment processes. Specifically, kinetic lumping strategies and models suitable for wastewater treatment applications have been developed. Examples are provided to illustrate how to select and evaluate lumping schemes and how to calculate lumped rate constants involving reactions starting with single organic constituents and organic mixtures, subjected to hydrothermal oxidation (supercritical water oxidation). The application of kinetic lumping to traditional waste treatment processes is also demonstrated through discussion and examples involving aerobic and anaerobic biodegradation.

ISSN:1061-4303    

DOI:10.2175/106143096X127848

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

The spatial and transient behavior of the coupled mechanism of saltwater and freshwater flow throughout the Erzin, Turkey, groundwater basin was analyzed to forecast the position of the interface under a particular set of recharge and discharge conditions. The density‐driven saltwater intrusion process was simulated with the use of a finite element model. Physical parameters, initial heads, and boundary conditions of the basin were defined on the basis of available field data, and an areal, steady‐state groundwater model was constructed to calibrate the observed head values corresponding to the initial development phase of the aquifer. Initial and boundary conditions determined from the areal calibration were used to evaluate the aquifer's dispersivities and the porosity in a steady‐state, cross‐sectional analysis. Consequently, the initial position of the salt concentration distribution was calibrated under steady‐state conditions. The initial concentration distribution was then marched through time under discharge and recharge conditions, and the present‐day position of the interface was predicted. In the cross‐sectional simulation, the saltwater front was predicted to move inland during the discharge period, whereas in the recharge period the heads were predicted to recover to their initial positions with no significant movement of saltwater. The present‐day distribution of salt concentrations was estimated via a 25‐year simulation. Results indicate that the width of the dispersion zone has increased during this period and the saltwater encroachment has gradually been slowed down, tending toward a new steady‐state position.

ISSN:1061-4303    

DOI:10.2175/106143096X127857

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

Nonvolatile dissolved organic carbon (DOC) in reclaimed wastewaters and groundwater was characterized and indicators of wastewater origin were identified. Over 50% of the DOC in activated carbon and reverse osmosis effluents was classified as hydrophilic, and no humic acid was isolated. In groundwater partially recharged by the reclaimed wastewaters, only 16% of the DOC was hydrophilic, 50% of the DOC was fulvic acid, and humic acid was recovered. The H:C ratios of the isolated fulvic acids were higher in the wastewaters and recharged groundwater than in deep well water not affected by recharge. N:C ratios in the wastewater and recharged groundwater fulvic and humic acid fractions were also higher than in the deep well water. The1H NMR spectra of the effluent and recharged groundwater fulvic acid fractions exhibited a characteristic fingerprint pattern, indicating a correlation between origin and spectral appearance. Gas chromatography‐mass spectrometry analysis confirmed the presence of specific trace organic compounds, including EDTA and alkylphenol polyethoxylate residues, in the wastewaters and recharged groundwater.

ISSN:1061-4303    

DOI:10.2175/106143096X127866

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

Batch and column studies were performed to determine the effect of pH, empty bed contact time (EBCT), and hydraulic loading rate (HLR) on lead removal by granular activated carbon (GAC) columns. Lead removal increased with increasing pH, and for the majority of the adsorbate:adsorbent ratios investigated, was 100 % at pHs

ISSN:1061-4303    

DOI:10.2175/106143096X127875

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

The phenomenon of granulation was studied in anaerobic sequencing batch reactors (ASBRs) treating a synthetic sucrose wastewater. The objective was to study methods of minimizing the time typically required for start‐up of anaerobic processes, such as the ASBR. Specifically, it was hypothesized that development of a granular biomass soon after initial start‐up of the ASBR would significantly decrease the overall time required to achieve given organic and hydraulic loading rates.
Laboratory‐scale ASBRs were seeded with anaerobically digested municipal biosolids and operated until granulation was observed or for a period of 5 months without granule development, whichever occurred first. Granule development was measured by determination of the average particle diameter of a representative sample of biosolids from the ASBRs.
Granulation enhancements were added to the ASBRs to initiate early granule development and to aid in start‐up. Enhancements included powdered activated carbon, granular activated carbon, silica sand, garnet, polymers, and ferric chloride. The cationic polymer had the most beneficial effects on granulation enhancement, reducing the time required to form granules by approximately 75% compared to an un enhanced control ASBR.

ISSN:1061-4303    

DOI:10.2175/106143096X127893

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

Wastewater generated by a chemical manufacturing facility required a significant reduction in the bis(2‐ethylhexyl) phthalate, di‐n‐octyl phthalate, and di‐n‐butyl phthalate ester concentration before discharge to a publicly owned treatment works (POTW). These three phthalate esters along with other esters and alcohols make up a dispersed phase in the wastewater that has lower density than water. Centrifugation was evaluated as a pretreatment process for the removal of the phthalate esters to within the effluent limits set by the POTW.
The wastewater was treated by a fun‐scale commercial centrifuge at different operating conditions (effluent back pressure and flow rate) to determine the optimum conditions for phthalate ester removal. The results of this study suggest that the degree of phthalate esters removal is independent of wastewater flow rate and centrifuge effluent back pressure but depends solely on the stability of the phthalate ester emulsion that appears to be directly related to the concentration of emulsifying agent (sodium monoester salts) in the wastewater.
Centrifugation provided better phthalate ester separation from the wastewater than gravity separation alone; however, the periodic occurrence of heavily emulsified phthalate esters in the wastewater necessitates the use of an equalization tank downstream of the centrifuge to consistently meet the effluent limit of 5.0 mg/L of the three phthalate esters.
In addition to the wastewater effluent, the centrifuge produces a light‐phase effluent and a sludge effluent. The light‐phase effluent contains esters, alcohol, and water and can be recycled back to the ester facility for reprocessing into salable product. The sludge effluent contains a dilute concentration of solids with a significant amount of adsorbed phthalate esters. The phthalate esters can be separated from the solids into an oily layer under acidic conditions. The oily layer can then be removed by reprocessing the acidified solids stream in the centrifuge, thereby enabling the disposal of the solids with the treated wastewater. This integrated waste management process would eliminate the need for additional solids processing equipment.

ISSN:1061-4303    

DOI:10.2175/106143096X127901

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

An empirical ultraviolet (UV) disinfection model was developed to predict coliform inactivation in unfiltered secondary wastewater effluent. The model was developed in the tailing region of the UV dose‐response curve for log survival values less than −3. Input parameters to the model include the suspended solids concentration, the unfiltered UV transmittance measured at a wavelength of 253.7 nm, the influent coliform concentration before exposure to UV light, and the applied UV dose. In the model, UV dose is calculated as the average UV intensity within the reactor (using the point source summation method) multiplied by the exposure time (based on the assumption of approximate plug flow conditions). Because the model is empirical, it should be calibrated to establish the statistical significance of each input parameter before use in a particular situation and to implicitly account for other factors influencing disinfection performance. The model was calibrated with data collected from a small‐scale UV reactor operated at two northern California wastewater treatment plants. The values of suspended solids concentration, unfiltered UV transmittance, and UV dose were found to be statistically significant with the water quality data set considered. The correlation coefficient (R2) of the calibrated model was 0.79. The calibrated model was then used to illustrate a design approach that integrates model uncertainty, wastewater variability, and variable permit requirements. In this approach, the number of UV lamps, modules, banks, and channels can be optimized to provide cost‐effective designs. Several design examples are used to illustrate both disinfection and headloss considerations in the recommended design approach.

ISSN:1061-4303    

DOI:10.2175/106143096X127910

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

A batch respirometric test was developed to measure the response of activated sludge communities degrading low concentrations of organic chemicals. The low substrate concentrations used in the assay ensure that minimal changes occur in the physiological state of the degrading community. The estimated kinetic parameters are, therefore, extant, that is, representative of the existing condition of the biomass in the continuous bioreactor. Monte Carlo and sensitivity analyses were performed to verify the robustness of the technique for determining unique and accurate estimates of the parameters describing Monod and Andrews kinetics. Application of the technique to a laboratory‐scale activated sludge system showed that kinetic parameter estimates were reproducible and independent of the substrate concentration within the range tested (0.2–4.0 mg/L as chemical oxygen demand [COD]). LowKsvalues (<0.1 mg/L as COD) were measured by the assay for the biodegradation of phenol and 4‐chlorophenol, both of which exhibited an inhibitory response (Andrews kinetics). The biodegradation of ethylene glycol, acrylamide, and acetate exhibited Monod kinetics.

ISSN:1061-4303    

DOI:10.2175/106143096X127929

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY