ISSN:1061-4303    

DOI:10.2175/WER.66.3.1

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT:
This paper outlines the increasing need for effluent polishing in the United Kingdom. It puts that need in the context of the more than 700 sewage treatment works serving populations of less than 2 000 in Severn Trent Water's area of the English Midlands. Constructed reed beds have their place in a design selection matrix. At the end of 1991, they were in use at 12 sites and more than 60 are programmed for completion in 1992. The design and construction of reed beds used for effluent polishing is described. Detailed results are given for five of the works commissioned between 1987 and late 1991. All produce high quality effluents in terms of BOD5and total suspended solids. A cost comparison between reed beds and modular sandfilters, based on recent contract prices, is shown. Estimates of maintenance, labor costs, and asset life are included.

ISSN:1061-4303    

DOI:10.2175/WER.66.3.2

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT:
Density, taxa richness, and composition of macroinvertebrates collected by three types of samplers were compared to determine their relative effectiveness for sampling in large rivers. Three multiplate samplers and three gravel basket samplers were deployed in the water column, and three large‐cobble basket samplers were deployed on the river bottom. Two sites were sampled at monthly intervals from October 1988 to November 1989. Macroinvertebrate densities were significantly (p<0.05) different among the three sampler types. Mean monthly macroinvertebrate density was highest on the multiplate samplers at both sites—1 742 and 1 239 macroinvertebrates/m2and was lowest on the large‐cobble basket samplers at both sites—174 and 266 macroinvertebrates/m2. Mean monthly macroinvertebrate density was moderate on the gravel basket samplers at both sites—278 and 472 macroinvertebrates/m2. Mean monthly taxa richness was generally higher on the gravel basket and large‐cobble basket samplers than on the multiplate samplers. Multiplate samplers collected larger numbers ofChironomidae, Oligochaeta, Trichoptera,andEphemeroptera,but were least effective at collectingTurbellaria,burrowingEphemeroptera, Odonata,andMollusca. Gravel basket samplers collected larger numbers ofChironomidae, Oligochaeta, Crustacea,andEphemeroptera,and in addition collected moreOdonataandMollusca. Large‐cobble basket samplers collected more burrowingEphemeroptera.

ISSN:1061-4303    

DOI:10.2175/WER.66.3.3

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT:
The thermal regeneration of spent granular activated carbon (GAC) at the Upper Occoquan Sewage Authority (UOSA) was investigated as a function of time, temperature, and the amount of applied oxidants. The GAC was also acid‐washed to remove metals and then regenerated to study acid‐washing's effect on adsorption. The regenerations were conducted with a batch‐feed, fluidized‐bed furnace. GAC quality was evaluated by measuring apparent density, pore size distribution, surface area, and adsorption capacity. Spent and regenerated GAC from UOSA's system and virgin carbon of the same type were studied. Isotherms for system GAC regenerated to various apparent densities showed little difference in dissolved organic carbon (DOC) capacity. Regeneration of acid‐washed GAC resulted in lower mass and volume losses without sacrificing adsorption capacity, but a longer regeneration time was necessary to achieve a desired apparent density. Based on DOC adsorption behavior, recovering the virgin GAC apparent density does not appear to be a beneficial regeneration strategy for UOSA.

ISSN:1061-4303    

DOI:10.2175/WER.66.3.4

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT:
A relationship developed previously to estimate emissions from surface aerated reactors that accounts for both gas and liquid phase mass transfer resistances is extended to reactors with diffused aeration systems. The method accurately predicts the observed emission rate of twenty volatile organic compounds with a wide range of Henry's coefficients over a wide range of hydrodynamic conditions. The liquid‐and gas‐phase mass transfer coefficients are estimated.

ISSN:1061-4303    

DOI:10.2175/WER.66.3.5

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT:
Currently, over 99% of all photoprocessing laboratories in the U.S. discharge directly to publicly owned treatment works (POTWs) after using various recovery methods. The purpose of this research was to investigate any potential adverse effects of photoprocessing effluents on the activated sludge process. Effluents from two commonly used photoprocesses were tested. These effluents were simulated in the laboratory and fed to fill‐and‐draw activated sludge reactors at loading levels less than or equal to 20% by volume along with a synthetic base feed. Conventional wastewater treatment parameters along with major photoeffluent constituents, such as ethylene diamine tetraacetate (EDTA), sulfur, and nitrogen species, were monitored. Results indicate that EDTA was recalcitrant and accounted for a significant fraction of the effluent COD. A significant fraction of the reduced sulfur species were oxidized to sulfate resulting in alkalinity consumption and a pH reduction. All activated sludge reactors showed a decrease in influent ammonia concentration and production of nitrate or nitrite. Up to 61% photoeffluent COD removal was achieved by the fill‐and‐draw activated sludge reactors. Such results demonstrate the potential of aerobic biological processes in the treatment of photoprocessing wastewaters and warrant further study.

ISSN:1061-4303    

DOI:10.2175/WER.66.3.6

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT:
The anaerobic biodegradation potential of photoprocessing effluents and their effect on the anaerobic digestion of biological sludge generated from the aerobic treatment of photoprocessing wastewaters were investigated. Simulated C‐41 photoprocessing wastewaters were subjected to an anaerobic toxicity test using the serum bottle technique. Unacclimated, anaerobic sludge inocula were used and the test solutions consisted of photoprocessing wastewaters and readily degradable organic substrates. Concentrations of photoeffluents considerably higher than those expected to reach municipal wastewater treatment plants initially depressed the production of methane, mainly because of competition between sulfate reducing and methanogenic bacteria. After prolonged incubation, methanogenesis recovered.
Biological sludge generated by laboratory‐scale activated sludge reactors with and without photoeffluents was fed to anaerobic digesters without adverse effects. The digesters fed sludge from the aerobic treatment of photoeffluents achieved about 14% higher digestibility than did the digester fed with sludge never exposed to the photoeffluents. For photoeffluent levels expected to reach municipal wastewater treatment plants, no adverse effects on anaerobic digestion are expected.

ISSN:1061-4303    

DOI:10.2175/WER.66.3.7

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT:
Each year, billions of gallons of wastewaters containing high concentrations of salt (>3.5% w/v) and waste organics are generated by industry. Biological treatment of these hypersaline waste brines to remove organics could reduce the environmental impact and cost of waste disposal. Unfortunately, the salinity of many waste brines makes them difficult to treat with conventional waste treatment cultures.
This paper demonstrates that heterotrophic, halophilic organisms can be used to remove phenol from a synthetic waste brine containing 15% salt. The reactor system used in this study was a novel periodically operated biofilm reactor, the Sequencing Batch Biofilm Reactor (SBBR). The SBBR uses permeable silicone tubing to supply oxygen to the reactor. A biofilm of halophiles isolated from the Great Salt Lake, Utah, ecosystem readily developed on the tubing surface and degraded waste organics. The experimental results presented herein demonstrate that the SBBR can produce a stable, high‐quality effluent despite fluctuations in influent phenol concentration. The results of periodic track studies illustrate that biomass accumulation increases oxygen demand but does not significantly improve overall reactor performance

ISSN:1061-4303    

DOI:10.2175/WER.66.3.8

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT:
The installation of continuous on‐line measurements of ammonium and nitrate in the aeration tanks of a nitrogen removing activated sludge plant has reduced the nitrate amount in the effluent by 60%. This corresponds to a drop in the average total nitrogen concentration in the effluent from 7.8 mg/L to 5.1 mg/L. The operation of the nitrogen removal process and thereby the effluent concentrations has become more stable. By combining operational changes in the biosorption with on‐line control of the process, it is possible to maintain full and stable denitrification at a BOD/N ratio of 3 to 4 without the use of any external carbon source, despite great variations in the loading of the plant. Monitoring of the microscopic characteristics of the sludge can be closely correlated with macroscopic characteristics such as sludge volume index.

ISSN:1061-4303    

DOI:10.2175/WER.66.3.9

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY

摘要:

ABSTRACT:
This research demonstrated the feasibility of a two‐phase anaerobic sludge digestion process. Process failure and maximum system loading capacity were also investigated. Three‐dimensional plots of chemical oxygen demand (sol), volatile fatty acids (VFA), and mixed liquor volatile suspended soils (MLVSS) profiles of both reactors during maximization and recovery periods (after failure) were made to evaluate the system feasibility. Hydrolysis‐acidification and acetogenesis‐methanogenesis dominated in the acid and methane phase reactors, respectively. Most of the reactions inside the methane‐phase reactor (M‐UASB) occurred in the lower part of the reactor (sludge bed and blanket). A combination of hydraulic and organic overloading of the M‐UASB reactor was a major cause of process failure; this was indicated by MLVSS washout, increase in total VFA concentration, reduction of the system removal efficiency, a drop in pH, an increase in total VFA/alkalinity ratio, a reduction of methane gas production, and an increase in the effluent total VFA. Because of system overloading, there was a shift in the metabolic pathway to a less favorable one, resulting in a shift of VFA producers (acidogens and acetogens) and consumers (methanogens, SRB, and NRB) ratio inside the reactor; this possibly led to a significant accumulation of carbon dioxide and hydrogen gas production. As a result, the partial pressure of hydrogen gas inside the system increased to a certain level, causing a shift in the metabolic pathway and accumulation of propionic acid. The maximum hydraulic loading rates achieved were 1.6 and 0.90 m3/m3d, equivalent to hydraulic retention times of less than 0.63 and 1.13 days, for the M‐UASB and the whole system, respectively.

ISSN:1061-4303    

DOI:10.2175/WER.66.3.10

出版商:Water Environment Research Foundation (WERF)    

年代:1994

数据来源: WILEY