ISSN:1061-4303    

DOI:10.2175/WER.65.5.1

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:
Triplicate wastewater sludge samples, from three small municipal facilities that received no industrial inputs, were analyzed by the Extraction Procedure Toxicity Test (EP) and Toxicity Characteristic Leaching Procedure (TCLP). These tests evaluate the potential for organic and inorganic chemicals to leach from the sludge. Six surrogate chemicals were spiked into the sludges to monitor recoveries of specific chemicals by the two procedures. The recoveries for the surrogate chemical spiked into the sludges were low (0.1‐33%) and variable for both tests. EP and TCLP tests performed similarly in that both tests yielded highly variable results in terms of the number of chemicals and the concentrations detected in the replicate samples. Only four organic pollutants (p‐cresol, dichlorodimethoxybenzene, dimethylpentanol, and tetramethylbutylphenol), at microgram per kilogram concentrations, were identified in the sludge samples. Based on this research, few organic pollutants appear to be leached from municipal‐only wastewater sludges.

ISSN:1061-4303    

DOI:10.2175/WER.65.5.2

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:
Many problems in environmental quality require measurements on chemicals that are expected to be absent or to exist at very low concentrations. Test specimens delivered to the laboratory for analysis will contain literally “next to nothing” which may lead to some observations being reported as “below the limit of detection.” The limit of detection is a statistical concept that is intended to reflect the magnitude of unavoidable random fluctuations in measurements at these low concentrations.
The purpose of this study was to generate a collection of measurements on samples that have low concentrations, at or near the limit of detection. The results show the magnitude of measurement variability at low concentrations and have some important implications regarding the utility of the limit of detection concept in compliance monitoring.
An interlaboratory study involving eight laboratories, each of which measured lead on 50 test specimens, provides a large collection of measurements on lead at low concentrations, including concentrations below the laboratories' stated limits of detection. The data show that the variability of measurements at low concentrations was not greater than at the higher concentrations. Lead was not only detected in low concentration specimens, it was also quantified, even at concentrations near and below the limit of detection as it is usually defined, especially when data are interpreted collectively instead of as isolated individual values. The accuracy of measurements may be affected more by bias than by poor precision.
The method detection limit (MDL) is a misunderstood and often misused concept. The concept of an MDL does not deal with bias; it is only concerned with precision. It is a quantity that cannot be estimated with great precision. Throwing away measured values because they are “below the limit of detection” discards much useful information and it is recommended that this practice be discontinued.

ISSN:1061-4303    

DOI:10.2175/WER.65.5.3

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:
A radiotracer study was conducted to determine removal efficiencies for cobalt, cesium, and iodine in a conventional municipal wastewater treatment plant. The study was conducted in a full‐scale facility that provides primary treatment through physical settling and secondary treatment using activated sludge. The radiotracers,58Co and134Cs as chlorides, and131I as Nal, were equilibrated in raw wastewater and introduced to the treatment system as a pulse in the incoming raw wastewater. Samples of wastewater and sludge were collected and analyzed to quantify primary treatment, secondary treatment, and overall removal efficiencies. Selected samples were filtered to determine the partitioning of the tracers between the solid and liquid phases of the wastewater and sludge throughout the treatment process. In the incoming wastewater, approximately 10% of the58Co, 7% of the134Cs, and 3% of theI31I were associated with suspended solids. The suspended tracer fractions decreased across the treatment plant. Primary treatment resulted in the partial removal of the incoming suspended fraction with observed removal efficiencies of 8.1% and 3.0% for58Co and134Cs, respectively, and an estimated removal of 2% for131I. Approximately 80% of the radiotracers in the primary treatment sludge were associated with the sludge solids. The affinity of the radiotracers for the activated sludge solids was in the following order:58Co>134Cs>131I. Secondary treatment removal efficiencies of 25% and 9.4% were observed for58Co and134Cs, respectively. The secondary treatment removal efficiency for131I was estimated to be 2‐3%. Overall removal efficiencies were 31%, 12%, and 3‐5% for58Co,134Cs, and131I, respectively. The remaining fractions of the radiotracers remained within the soluble phase of the wastewater and were discharged in the treatment plant effluent.

ISSN:1061-4303    

DOI:10.2175/WER.65.5.4

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:
The sorption of cyanide at levels ≤ 1 mg/L in solution by granular activated carbon (GAC) was investigated in order to define the conditions required to reduce residual levels to below the maximum acceptable concentration value specified in the Guidelines for Canadian Drinking Water Quality. The sorption process proceeded slowly with uptake continuing over a 30‐hour mixing period. The initial rate of adsorption increased with decreasing particle size of the activated carbon. In general, uptake was independent of pH except for a slight increase in the pH range of 8‐9, but increased linearly with increasing adsorbent density until the concentration of cyanide was lowered to approximately 0.3 mg/L; below 0.3 mg/L, the amount sorbed became proportional to a power‐law term of the adsorbent density. The effect of cyanide concentration on the uptake could be described by a Freundlich isotherm with the amount sorbed per unit weight of granular activated carbon being proportional to (Ce)0.13. Addition of up to 10 mg/L nitrilotriacetic acid had little effect on the amount of cyanide adsorbed; however, humic acid, Ca(II), Mg(II), Al(III), and Fe(III) reduced the cyanide uptake by 30‐50%. Possible mechanisms for cyanide sorption by GAC and their implications for water treatment have been considered. The mechanisms considered include CN−uptake by ion exchange, and sorption of cyanide as HCN molecules through formation of H‐bonds with oxygenated functional groups such as — COH.

ISSN:1061-4303    

DOI:10.2175/WER.65.5.5

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:
Organic wastes of high concentration and containing high concentrations of metals have generally been treated by a preliminary metal removal process (for example, precipitation) followed by biological treatment of the degradable component of the organic matter. It was the objective of this study to determine if a high strength waste containing metals could be treated by a precipitation‐anaerobic digestion process in which the precipitant was sulfide generated by the digestion step itself. To answer these questions, laboratory reactors were fed a synthetic medium (containing copper as the metal of interest and glucose and acetate as primary organic substrates) and operated in a semicontinuous draw and fill manner. Overall, the results of this study are encouraging and point to the potential feasibility of the process.

ISSN:1061-4303    

DOI:10.2175/WER.65.5.6

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:
Zooplankton filter feed small suspended solids (SS) while filter‐feeding fish (Hypophthalmichthys molitrix) feed on large suspended particles. The combination should control SS and nutrients in wastewater stabilization ponds. The technique proposed herein maintains coexistence of zooplankton and filter‐feeding fish by excluding the fish from part of the water column. A series of 1‐m3tanks was stocked with channel catfish (Ictalurus punctatus) alone, catfish and silver carp, or catfish and silver carp that were excluded from one‐half of the water column. The refuge permitted coexistence of high densities of zooplankton with the silver carp, and the combination of filter feeders reduced algal biomass by as much as 99% compared to controls. SS and nutrients were presumably likewise controlled. Application to stabilization ponds in series would be straightforward.

ISSN:1061-4303    

DOI:10.2175/WER.65.5.7

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:
A discussion of the current understanding of the competition between sulfate‐reducing bacteria and methanogens is presented. The effect of artificially elevated sulfate and sulfide levels on anaerobic utilization of lactate was investigated using acclimated and unacclimated inoculum. The lactate degradation pathway was observed to be dependent upon the degree of acclimation to various chemical oxygen demand (COD):sulfate ratios. A ratio of 3.7 g/g resulted in a nonsulfate reducing pathway producing propionate and acetate as products, while a ratio of 1.6 g/g resulted in a sulfate reducing pathway producing only acetate as an organic product. The change in metabolic pathways dramatically changed the relative sulfide sensitivity of the methanogens and the sulfate reducers.

ISSN:1061-4303    

DOI:10.2175/WER.65.5.8

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:
Photoactive catalysts, when illuminated with UV‐light, generate highly reactive radicals that can oxidize the organic contaminants in water. One method to increase the efficiency of the process, and thereby reduce the light energy requirements, is by developing more active catalysts. Several catalysts that were obtained commercially and/or prepared in the laboratory were examined for their photoactivity, and they are: Ti02, Pt‐Ti02with platinum loading varying from 0.5% to 10% by weight, SrTi03, and 1.5% NiO‐SrTi03. The organic compounds used to identify the best catalyst were trichloroethylene (TCE), toluene, methyl ethyl ketone (MEK), salicylic acid, and 2,4‐dichlorophenol, with initial concentration varying from 0.1 to 10.0 mg/L. This study also examined the impact of catalyst dosage, organic compound and its initial concentration, and electron acceptor concentration on the reaction kinetics. The process efficiency for mineralization of organic compounds is also evaluated. The results demonstrate that the activity of photocatalysts can be improved by approximately 2–4 times over commercially available catalysts.

ISSN:1061-4303    

DOI:10.2175/WER.65.5.9

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY

摘要:

ABSTRACT:
This paper presents the results of a study (Larry Walker Associates, 1990) to determine the nature of additional controls necessary for the Sacramento Regional Wastewater Treatment Plant (Regional Plant) to comply with the numeric water quality objectives for metals recently adopted by the State of California. In addition, the impact of Regional Plant effluent on Sacramento River metals concentrations is examined, and the costs of compliance with the new objectives are estimated.
Monte Carlo techniques are used to determine the ability of the Regional Plant to achieve the metals objectives and the effects of treatment plant discharge on receiving water metal concentrations. Frequency distributions of advanced treatment efficiencies, such as lime precipitation and reverse osmosis, are used to simulate effluent concentration reductions that are potentially achievable. The costs associated with the additional treatment required to meet objectives are estimated using published cost estimates for advanced treatment plants of similar size. Results show that currently, the Regional Plant does not meet objectives for cadmium, copper, mercury, and zinc. Furthermore, the additional treatments evaluated would not completely eliminate violations of the copper and mercury objectives.

ISSN:1061-4303    

DOI:10.2175/WER.65.5.10

出版商:Water Environment Research Foundation (WERF)    

年代:1993

数据来源: WILEY