ISSN:1061-4303    

DOI:10.2175/WER.64.3.1

出版商:Water Environment Research Foundation (WERF)    

年代:1992

数据来源: WILEY

ISSN:1061-4303    

DOI:10.2175/WER.64.3.14

出版商:Water Environment Research Foundation (WERF)    

年代:1992

数据来源: WILEY

ISSN:1061-4303    

DOI:10.2175/WER.64.3.15

出版商:Water Environment Research Foundation (WERF)    

年代:1992

数据来源: WILEY

摘要:

ABSTRACT:
The use of arsenic in agriculture, industry, and domestic endeavors since the last century has increased the concentration of arsenic in the environment.
During cleanup activities at a former pesticide facility, water that was collected during various operations was contaminated with arsenic and required treatment before discharge. Chemical precipitation was identified as being the most effective means of treatment.
Bench‐scale treatability testing was completed to determine the effectiveness of various coagulants, including ferric chloride, hydrated lime, sodium sulfide, and alum. A combination of hydrated lime and ferric chloride was able to remove more than 99% of the original arsenic concentration.
Contaminated water to be treated by the full‐scale system had arsenic concentrations up to 48 mg/L. The discharge limitation required that the arsenic concentration be reduced to less than 1 mg/L. More than 605 000 L (160 000 gal) of water were treated using a combination of chemical precipitation, filtration, and carbon absorption.

ISSN:1061-4303    

DOI:10.2175/WER.64.3.2

出版商:Water Environment Research Foundation (WERF)    

年代:1992

数据来源: WILEY

摘要:

ABSTRACT:
Previous work by the authors suggested that activated sludge sedimentation might be highly sensitive to underflow geometry. Field, physical model, and stratified flow numerical model tests were conducted to evaluate this hypothesis. Field work included solids settling velocity, dye dispersion, and flow pattern/solids distribution tests. Physical tests included operation of a pie‐shaped 1:12.5 scale model of a circular, center‐feed tank with sludge withdrawal simulating countercurrent, uniform, and cocurrent geometries. A stratified flow numerical model that simulated the effects of density currents was calibrated to the results of the full‐scale testing. The results failed to confirm the experimental hypothesis. Model performance was relatively insensitive to underflow geometry in a circular tank when density effects were simulated.

ISSN:1061-4303    

DOI:10.2175/WER.64.3.3

出版商:Water Environment Research Foundation (WERF)    

年代:1992

数据来源: WILEY

摘要:

ABSTRACT:
Acquired Immune Deficiency Syndrome (AIDS) is one of the major health concerns in the world today. The Human Immunodeficiency Virus (HIV), the virus that causes AIDS, has been identified in body fluids and excretions from infected individuals. These body fluids and excretions may result in the presence of HIV in raw wastewater.
The objective of this research was to determine the survivability of HIV in raw wastewater and wastewater that had been subjected to various degrees of treatment. To accomplish this objective, wastewater samples were collected, inoculated with known concentrations of HIV, and held at room temperature for up to 72 hours before concentration and assay.
Results presented in this paper indicate that infectious HIV is fairly stable in wastewater for up to 12 hours but experiences a 2 to 3‐log reduction in infectivity after 48 hours. When compared to poliovirus under similar conditions, HIV survival was significantly less.

ISSN:1061-4303    

DOI:10.2175/WER.64.3.4

出版商:Water Environment Research Foundation (WERF)    

年代:1992

数据来源: WILEY

摘要:

ABSTRACT:
The treatment of metal‐cutting‐fluid wastewater was investigated using an anaerobic, granular activated carbon, fluidized‐bed process. During 900 days of operation, three influent COD concentrations were tested: 1029, 3343, and 5324 mg/L. For each influent COD concentration, a series of influent flow rates was used to test a range of unexpanded empty‐bed contact times from 0.9 to 7.5 hours. The findings include the following: (1) the reactor removed biodegradable COD effectively and efficiently at relatively high loading rates (more than 70 kg/m3· d); (2) approximately 35% of the influent COD was nonbiodegradable—more than approximately 65% of the nonbiodegradable COD was aerobically biodegradable; (3) approximately 68% of the COD biodegraded was converted to methane, showing potential for energy recovery; (4) a relatively low biomass production (a yield coefficient of approximately 0.09 g biomass produced/g COD degraded) was observed; and (5) the overall removal rate of biodegradable COD followed firstorder kinetics.

ISSN:1061-4303    

DOI:10.2175/WER.64.3.5

出版商:Water Environment Research Foundation (WERF)    

年代:1992

数据来源: WILEY

摘要:

ABSTRACT:
Available growth kinetic models and a combined growth kinetic and mass transport model were applied to describe the performance of bench‐scale rotating biological contactors (RBCs) in treating low‐BOD, high‐ammonia landfill leachate. The growth kinetic models could describe the observed organic carbon and ammonia removals individually, but as currently formulated they are not capable of describing the simultaneous removal of multiple substrates. Moreover, these models assume that substrate removal is not oxygen limited, an assumption that renders them of little use for prediction of substrate removal under high loading conditions where oxygen deficiency may occur. Such conditions occurred in the first stages of the bench‐scale RBC units as has been observed at full‐scale in various wastewater treatment applications. To examine the effect of oxygen transfer on the simultaneous removal of organic carbon and ammonia, a combined growth kinetic and mass transport model, RBC Sector, was developed. RBC Sector described successfully the observed substrate removal rates and was useful in identifying the tank dissolved oxygen concentration (1.8 mg/L) at which RBC performance started to decline as a result of oxygen limitation. Because RBC Sector can predict the simultaneous removal of multiple substrates under oxygen‐limiting conditions, it is potentially useful as a scale‐up tool. Investigation of a key scale‐up issue, namely the radial variation of biomass thickness and density, would improve the utility of the model for scale‐up.

ISSN:1061-4303    

DOI:10.2175/WER.64.3.6

出版商:Water Environment Research Foundation (WERF)    

年代:1992

数据来源: WILEY

摘要:

ABSTRACT:
The liquid flow through activated sludge floes from fullscale conventional treatment plants was evaluated on the basis of the information obtained from settling tests. In the samples of the mixed liquors studied, only a part of the activated sludge flocs was found permeable to fluid drainage. Basically, small flocs were not permeable but all the flocs in the size range from 100‐150 μm showed different degrees of permeability. The permeability of flocs increased with an increase in the dynamic sludge age and decreased with an increase in the shear rate measured as the mean velocity gradient in the aeration tanks. The most sensitive assumption for the estimation of the permeability of the flocs was the size of the primary particles in the aggregates, with the sphericity of the flocs being less important. It was also found that the CarmanKozeny model reflected well the porosity‐permeability relationship of most activated sludge flocs, except those that contained substantial amounts of filamentous growth. During free gravitational settling, flocs with the longest dimensions in the size range of 50 to 1000 showed a drainage rate in the range of 102to 107μm3/s, which followed the Carman‐Kozeny model with a power relationship of 4.08.

ISSN:1061-4303    

DOI:10.2175/WER.64.3.7

出版商:Water Environment Research Foundation (WERF)    

年代:1992

数据来源: WILEY

摘要:

ABSTRACT:
The Hydrological Simulation Program in FORTRAN (HSPF) was used to evaluate the proposed implementation of various best management practices (BMPs) to reduce erosion and sedimentation. The nonpoint source model, which was previously calibrated and verified, was adjusted to account for changes in model parameters affected by proposed BMP scenarios. BMPs included conversion of cropland to grassland (BMP #1), conservation tillage systems (BMP #9), and reservoir construction (BMP #12). BMP #1 achieved the greatest reduction in watershed erosion and stream sediment loads, while BMP #9 provided only moderate reductions. Construction of three new reservoirs in the 146‐km2 basin provided approximately 50% of the reduction in stream sediment loads as BMP #1. The most cost‐effective approach was BMP #1.

ISSN:1061-4303    

DOI:10.2175/WER.64.3.8

出版商:Water Environment Research Foundation (WERF)    

年代:1992

数据来源: WILEY