ISSN:1061-4303    

DOI:10.2175/WER.66.6.1

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT:
Hydrogen sulfide corrosion can occur in sewage force mains in places where the sewage does not continuously contact the top of the pipe. This situation can occur because air is drawn into the pipe when the hydraulic grade line is below the pipe, or a gas pocket cannot be dragged down a downward slope because of the buoyancy of the pocket. This paper presents and verifies methods for predicting when each of these situations can occur and applies the results to an existing force main.

ISSN:1061-4303    

DOI:10.2175/WER.66.6.2

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT:
The success of gravity separation of activated sludge from a treated effluent depends on the flocculent nature of the mixed liquor entering the secondary clarifier. Despite its importance to the overall effectiveness of the activated sludge process, flocculation phenomena are not routinely considered in the design and operation of the process. Further optimization of the activated sludge process to meet higher performance demands requires that the competing reactions of floc aggregation and breakup be maximized and minimized, respectively. Accordingly, the goal of this study was to develop an improved understanding of activated sludge flocculation.
A theoretically based and easily performed batch flocculation procedure was developed. The procedure enabled the quantification of the flocculation characteristics of activated sludges. The procedure was field applied, testing 30 activated sludges obtained at 21 full‐scale facilities. Results obtained during the field study indicated that the equilibrium concentration of supernatant suspended solids following batch flocculation and settling is comparable for a wide variety of activated sludges regardless of the initial aggregative state of the mixed liquors or the aeration device employed. The results indicated that flocculation of activated sludge cannot be used to reduce supernatant suspended solids below a certain limit. Moreover, the results indicated that attainment of equilibrium is rapid; the activated sludge flocculation reaction in batch reactors was 99% complete within 10 minutes for all but six of the activated sludges studied. Field‐determined estimates of activated sludge flocculation characteristics can be used to predict the performance of flocculators placed either upstream of or in secondary clarifiers. These estimates also can be used to determine the impact of altering process variables on flocculation, thereby affording a procedure for optimizing an activated sludge's flocculation potential.

ISSN:1061-4303    

DOI:10.2175/WER.66.6.3

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT:
This paper presents a probabilistic approach to develop initial dilution criteria or standards for ocean outfall design and environmental impact assessment of effluent discharges. In contrast to a currently used worst case approach, in which a particular combination of parameters affecting initial dilution is specified and an associated initial dilution is calculated using a deterministic dilution model, the probabilistic approach provides a framework for combining data for the parameters which are often available in the form of time series or described in statistics. The result of the probabilistic approach is a description of initial dilution as a function of cumulative or exceedance probability, from which the exposure risk level for the marine environment can be estimated and criteria or standards can be defined. The proposed methodology basically consists of implementing a probabilistic method with a deterministic initial dilution model. The probabilistic method could be time domain simulation, Monte Carlo simulation, or first‐order uncertainty analysis; while the deterministic initial dilution model could be a mathematical model, a physical model, or an empirical equation. A case study is presented of the Miami‐Central Outfall on the east coast of South Florida to compare the probabilistic approach with the worst case approach. In this case study, time domain simulation using actual data sets was employed to generate a time series of initial dilution (dilutions were calculated using a semi‐empirical equation). Some statistics of initial dilution were then obtained from the simulated dilution time series. For this case study, the worst case dilution is 17.3 (minimum surface or near‐surface dilution) and the associated cumulative probability is 5.4%.

ISSN:1061-4303    

DOI:10.2175/WER.66.6.4

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT:
Sludge taken from a recirculated upflow anaerobic sludge blanket (RUASB) treating phenolic wastewater at organic loadings of 6, 12, 16, and 20 kg COD/m3day was tested by the biochemical methane potential (BMP) method at intervals over a three‐year period for an accurate determination of the specific gas production rate. A modified version of the Haldane equation was used in the selection of a statistically significant model describing this process. Statistical diagnosis was carried out with studentt‐test, Durbin‐Watson test for two‐tail distribution and Kalmogorov‐Smirmov statistical approach. The estimated ranges of the maximum specific reaction rate,K; saturation constant,Ksinhibitor constant,Ki; and the order of inhibition,nwere as follows: 280–764 mL biogas/gVSS‐day, 202–398 mg phenol/L, 516–880 mg phenol/L, and 1.47–2.51, respectively. The physical meaning of these parameters is explained. BMP tests with sludge taken from the recirculating upflow anaerobic sludge blanket (RUASB) bioreactor running at a loading of 14 kg COD/m3day validated the effectiveness of the selected model through comparisons of experimental data and predictions. The results indicate that model predictions accurately reflect experimental data within one standard deviation.

ISSN:1061-4303    

DOI:10.2175/WER.66.6.5

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT:
This paper describes a laboratory and field study of the behavior of sewage oil and grease after discharge to an ocean environment. The laboratory program was used to study the factors affecting coagulation and to determine if discharge through an ocean outfall enhances coagulation leading to an increase in concentration of floatable material on the ocean surface. A field study was conducted at Burwood Beach near Newcastle on the New South Wales coast to quantify the amount of oil and grease reaching the ocean surface from the outfall, to measure the size of particles of grease on the surface near the outfall, and to determine the conditions that lead to the formation of visible slicks and observable floatable material for an outfall discharging primary treated sewage.

ISSN:1061-4303    

DOI:10.2175/WER.66.6.6

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT:
The contribution of heavy metals from sources including household washing products, other residential sources, water supply and permitted industry to influent wastewater and treated effluent was determined for the wastewater treatment plants of the cities of San Jose/Santa Clara, Palo Alto and Sunnyvale, which are located in the Southern San Francisco Bay Area of Calif.
The heavy metals studied were arsenic, cadmium, chromium, copper, lead, mercury, nickel, silver, and zinc. In no case were household washing products the major heavy metal contributor to influent wastewater or wastewater effluents. The highest heavy metal contribution from household washing products was from arsenic. It accounted for 13% of the influent and effluent wastewater arsenic content. All other household washing product heavy metals contributions to influent and effluent wastewater were below 0.5% of the total metal present.

ISSN:1061-4303    

DOI:10.2175/WER.66.6.7

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT:
Conventional microbiological surveys, relying on periodic sampling of the water column, were unable to identify sources of fecal contamination at a local beach in North Vancouver, B.C., Canada. Many sources of human and/or animal wastes to the cove were evident (for example, storm sewers, animal feces on the beach, urban streams, discharges from boats, leaking sanitary sewers) but it was not possible to identify any one source as the cause of the pollution by sampling the water column since the contaminant source was likely episodic (that is, discharging for only brief periods). It was unlikely that any conventional sampling survey would coincide with a pollution event and thereby reveal a pattern of contamination. As a result, a novel sampling strategy was devised using sediment bags (porous bags filled with sand) suspended from buoys and deployed in a grid pattern around the beach. The sand in these bags accumulated fecal bacteria during pollution events and retained them long enough so that they could be analyzed during weekly sampling surveys; in this way, the true pattern of the pollution plume was documented and the source was revealed. Results from an analysis of the sediment bag grid indicated that storm sewers were the principal contaminant sources. The subsequent clean‐up was inexpensive compared with other proposed remedies (for example, diversion of urban creeks, replacement of sanitary sewers).

ISSN:1061-4303    

DOI:10.2175/WER.66.6.8

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT:
Bench‐scale experiments were conducted to investigate the effectiveness of an extraction and washing technique for the cleanup of contaminated soil using surfactants. The organics studied as model contaminants were 1,2,4‐trichlorobenzene (TCB), aniline, phenol, and 2,4‐dichlorophenol (DCP). A sandy loam was used as a model field soil. The results demonstrated the effectiveness of the extraction and washing process for decontamination of the sandy loam soil. As much as 99% of the organic contaminants studied were removed by the process depending upon the compound and the number of washes and rinses. The hydrophilic compounds—aniline, DCP, and phenol—were removed effectively from the soil by washing with deionized water alone. Surfactant washing had no advantage over water washing for these compounds. For the removal of TCB, a combination of washing with surfactant and rinsing with water was required. Alum coagulation was effective in separating clay and colloidal particles from the wash liquid but a relatively high alum dose was required and was observed to enhance adsorption of the contaminants on the clay particles. A small residual contaminant concentration remained in the soil.

ISSN:1061-4303    

DOI:10.2175/WER.66.6.9

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT:
Laboratory‐scale completely‐mixed and batch experiments investigated the fate and foaming potential ofNocardiaduring mesophilic anaerobic sludge digestion.Nocardiafilament concentration was measured by an immunofluorescent technique (Hernandezet al,1993); filament viability was by dehydrogenase activity staining (Awonget al.,1986). Continuous flow digesters, fed with waste activated sludge (WAS) containing highNocardialevels were operated at solids retention times (SRT's) of 10, 14, and 28 days to determine SRT effects onNocardiasurvival. In two‐phase digestion experiments, the digestion was divided into an initial acid phase (4‐day SRT; pH 5.4 to 6.4) and a second methanogenic phase (11‐ and 24‐day SRT's; pH 7.2). Batch digestion experiments determined effects of pH, TS concentrations, andNocardiafilament mass on digesting sludge foaming potential. None of the digestion systems completely removed or rendered non‐viable all influentNocardiafilaments. In single‐phase digestersNocardiafilament viable fraction decayed with a first order rate coefficient of approximately 0.02 day−1, so that with an SRT of 14 days, the viability decreased by approximately 37%. In two‐phase digestion viability decreased more rapidly; for a 14‐day total SRT, reductions were approximately 54%. In batch foaming tests on digested sludge, foam production levels increased in proportion toNocardiafilament concentration over the range of 0.01 to 0.2 gNocardia/g TS.

ISSN:1061-4303    

DOI:10.2175/WER.66.6.10

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY