ISSN:1061-4303    

DOI:10.1002/j.1554-7531.1996.tb00165.x

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

This research determined the removal and fate of 11 selected RCRA compounds in a pilot‐scale activated sludge system with a 4‐day SRT and 7.5‐hour HRT. Screened and degritted raw wastewater from a Cincinnati, OH, wastewater treatment plant was used for this study at the U.S. EPA's Test and Evaluation (T&E) Facility. A continuous feed of spike toxic cocktail of 0.25 mg/L each of acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, carbon tetrachloride, 1,1,1‐trichloroethane, 1,1,2‐trichloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, and ethylbenzene was used to produce an acclimated biomass. The test was run for 7 weeks. Volatilization losses in primary sedimentation exceeded 10% for carbon tetrachloride, 1,1,1‐trichloroethane, 1,1,2‐trichloroethane, and tetrachloroethylene. Sorption of the 11 compounds to primary and secondary sludge ranged from 0.6 to 5.1%. Nine of the 11 test compounds were removed>94% with estimated biodegradation ranging from 0 to 93.4%.

ISSN:1061-4303    

DOI:10.2175/106143096X127695

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

A field test of a solar photocatalytic process for detoxification of water was conducted at Tyndall Air Force Base, Florida, where benzene, toluene, ethylbenzene, and xylene (BTEX) compounds were found in the fuel‐contaminated groundwater. Platinized titanium dioxide supported on silica gel is packed in tubular photoreactors and used for single‐pass operations. Catalyst fouling, destruction inhibition, and water pretreatment are investigated in addition to BTEX destruction. Ionic species were found to be primarily responsible for photocatalyst fouling and destruction inhibition. A simple pretreatment unit was developed for removing turbidity, adding oxidant, and ionic species. By using pretreatment, the reactor system operated efficiently, and no loss in catalyst photoactivity was found during the month‐long test. On a rainy day, BTEX compounds of a total influent concentration of more than 2 mg/L were destroyed within 6.5 minutes of empty‐bed contact time. Test results with various flow rates, reactor diameters, influent concentrations, solar irradiances, and weather conditions confirm the application potential of the process.

ISSN:1061-4303    

DOI:10.2175/106143096X127703

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

Stock (fill‐and‐draw) reactors and chemostats (CSTR) fed acetate and glucose were used to investigate the production of soluble microbial products (SMP) during anaerobic treatment. These reactors were maintained at solids retention times (SRT) from 15 to 56 days with organic loading rates (OLR) from 0.18 to 0.50 g chemical oxygen demand (COD)/L · d. Results showed that longer SRTs resulted in higher levels of SMP, with SMP ranging from 17 to 59 mg COD/L when acetate was the sole carbon and energy source and 50 to 291 mg COD/L when glucose was the substrate. Normalized production of SMP (SMP/influent COD = SMP/S0) ranged from 0.2% to 1.0% for acetate reactors and 0.6% to 2.5% for glucose reactors. Steady‐state results from chemostats fed glucose showed that as SRT increased, SMP/S0decreased to a minimum and then increased, indicating the existence of an optimal operating SRT that would result in a minimum normalized production of SMP. Effluent soluble COD was mostly SMP; the fraction of effluent soluble COD made up of SMP increased with increasing SRT. Production of SMP from glucose reactors was modeled. Normalized production of SMP during anaerobic treatment appears to be lower when compared with aerobic production of SMP reported in the literature.

ISSN:1061-4303    

DOI:10.2175/106143096X127712

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

EPA's 1979 and 1993 sludge regulations require that sewage sludge be reduced in vector attraction before it can be applied to the land. In the 1979 regulation, satisfactory vector attraction reduction (VAR) could be demonstrated if treatment processes reduced the volatile solids content of sludge by 38%. The 1993 regulation adds two alternative test methods for aerobic sludges for determining whether VAR has been adequate. In the first method, specific oxygen uptake rate (SOUR) of the sludge must be<1.5 mg O2/hr/g total solids, and in the second method, the additional volatile solids reduction (AVSR) that occurs when the sludge is further digested for 30 days must be<15%. Experimentation with the new tests is described. Comparisons among the three methods showed that the 38% VSR requirement and the SOUR test were equivalent only near 20°C. The AVSR test was more conservative than either of the other tests.

ISSN:1061-4303    

DOI:10.2175/106143096X127721

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

A lanthanum‐impregnated silica gel has been developed for the removal of fluoride, phosphate, and arsenate ions by adsorption. The interaction between silica gel and lanthanum ion was maximum at a final pH of 6. The removal of fluoride and arsenate ions by adsorption on the lanthanum‐impregnated silica gel was more than 99.9% at neutral pH from initial concentration of 0.55 and 0.2 mmol/L, respectively. The removal of phosphate ion was 95% at an initial concentration of 0.5 mmol/L at neutral pH. Arsenite ion was not adsorbed on the material. The rate of adsorption of the anions followed the first‐order reaction and fit in the Lagergren equation. The adsorption of each anion followed the Langmuir isotherm. Other anions such as Cl−Br−, I−, NO3−, and SO42−did not interfere with the adsorption. A column study was conducted for the removal of these anions at a fixed flow rate of 0.5 mL/min at pH approximately 7. These anions were removed by more than 99.9% at initial first or second fraction, and the column was regenerated at pH 8.5. The method was applied for the removal of these anions from synthetic and high‐tech industrial wastewaters.

ISSN:1061-4303    

DOI:10.2175/106143096X127730

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

An understanding of the fate of metals in the activated sludge process is necessary. Such knowledge is needed to assess the potential adverse effects of metals that may be associated with activated sludge and ultimately discharged into the natural environment. As an example, an equilibrium approach was developed to quantify the distribution of trivalent chromium, Cr(III) in activated sludge. Cr(III) adsorption on activated sludge exhibited linear characteristics. Cr(III) formed a 1:2 complex with soluble organic compounds remaining in wastewater treatment plant effluents. Both pH and the mean cell retention time significantly affected Cr(III) adsorption and complexation. Intracellular Cr(III) uptake was estimated by comparing the observed overall Cr(III) uptake with the predicted Cr(III) adsorption. This comparison revealed that more Cr(III) is transported to the solid phase than predicted. The predicted speciation of Cr(III) suggested that intracellular Cr(III) accounted for more than 70% of the total Cr(III) in activated sludge. Thus, intracellular uptake was an important consideration.

ISSN:1061-4303    

DOI:10.2175/106143096X127749

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

Eleven stations in six rivers in the Comunidad Autonoma de Madrid (Spain) were studied during February 1993 to describe the protozoan communities and analyze the presence of lead and cadmium. The most polluted areas were Fuente del Fresno (Jarama River), where the levels of dissolved heavy metals were 10μg/L of cadmium and 1 140μg/L of lead acid, Torrej6n de Ardoz (Henares River) where there was 15μg cadmium and 1 140μg/L of lead. These two areas showed the greatest amount of industrial effluents, and the protozoan response expressed itself by the presence of resistant species suchEuglena gracilis; density and biomass were not affected, although there were changes in the trophic structure, with a predominance of bacterivore and nonselective protozoans. The effects of the heavy metals were masked by the organic pollution. In the stations in well‐oxygenated waters, there was a predominance of photoautotrophs and diatoms. In all zones a significant correlation between the density of bacteria and protozoans was observed. The trophic structure of the protozoan communities in the different water courses was influenced by the amount of food available and by organic pollution.

ISSN:1061-4303    

DOI:10.2175/106143096X127758

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

A significant problem encountered with anaerobic reductive dechlorination of polychlorinated ethylenes during groundwater remediation is accumulation of vinyl chloride (VC). Even when reduction of VC proceeds to ethylene and/or ethane, low levels of VC may persist. The purpose of this study was to examine use of ethylene and ethane as primary substrates for aerobic cometabolism of VC. Both ethylene‐ and ethane‐grown enrichment cultures (developed with activated sludge inoculum) readily consumed VC. The ethylene culture exhibited an initial preference for VC over ethylene but then switched after several weeks. This culture was unable to use ethane or VC as sole substrates. Although VC inhibited ethylene use, growth on ethylene still occurred in the presence of VC. The ethane‐grown culture was able to use both VC and ethylene as sole substrates. When all three compounds were present, ethylene was consumed first, followed by VC and ethane. Thus, the presence of ethylene and/or ethane with VC may eliminate the need to add a primary substrate (for example, methane, toluene, or phenol) to sustain cometabolism of VC below the regulatory limit.

ISSN:1061-4303    

DOI:10.2175/106143096X127767

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY

摘要:

Clarifier hydrodynamics plays an important role in the activated sludge process. Attention has long been focused on the biological behavior of the aeration basin in the secondary treatment system. One‐dimensional settler models or empirical relationships have typically been coupled in wastewater treatment plant simulation systems to represent the clarifier. The research on the hydrodynamic aspects of the process are currently restricted to a clarifier uncoupled from the aeration basin. In this paper, a dynamic model of the activated sludge process is presented in which balanced emphasis is put on the hydrodynamic aspect of the system. The model integrates a biological reaction submodel for an aeration basin with a two‐dimensional hydrodynamic solids transport submodel for the secondary clarifier. A verification of the model is carried out against a set of field data and shows good agreement. The model has been used to investigate the response and the interdependency of the aerator and clarifier in the activated sludge system.

ISSN:1061-4303    

DOI:10.2175/106143096X127776

出版商:Water Environment Federation    

年代:1996

数据来源: WILEY