ISSN:0003-150X    

DOI:10.1002/j.1551-8833.1994.tb06277.x

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

The author answers the question: What can US drinking water suppliers do to protect consumers from cryptosporidium? He suggests the following as steps to take in protecting consumers: recognize that cryptosporidium oocysts are present in all surface water supplies; protect our watersheds; consider using ozone as a primary disinfectant; monitor raw water; optimize coagulant dosages; produce filtered water with low turbidity; evaluate and optimize filter media; evaluate backwash practices; advise people who may be at risk; and establish a policy making cryptosporidiosis a reportable disease.

ISSN:0003-150X    

DOI:10.1002/j.1551-8833.1994.tb06278.x

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

Holland, Vermont, appealed a trial court judgment that exempted the underground pipes of the International Water Company (IWC) from real property taxes. The town argued that IWC's property did not meet the criteria of the “public‐use” test for exemption because the pipes that passed through town were not dedicated unconditionally to public use. The town said the pipes merely transported water to IWC's reservoir for later distribution to other municipalities. The town also said there was no public benefit until the water actually reached the municipalities that used it.

ISSN:0003-150X    

DOI:10.1002/j.1551-8833.1994.tb06280.x

出版商:Wiley    

年代:1994

数据来源: WILEY

ISSN:0003-150X    

DOI:10.1002/j.1551-8833.1994.tb06282.x

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

Mysterious short‐term pressure drops at the top of Cat Mountain prompted an investigation that revealed hydraulic transients as the culprit.Most engineers are familiar with hydraulic transients that cause problems with excessive pressure in water distribution systems. However, transients can also cause short‐lived low‐pressure problems. This article describes the analysis conducted by the Austin (Texas) Water and Wastewater Utility that identified transients as the source of low pressures in a portion of the city. Pressures recorded during controlled conditions provided the key in identifying pump and valve operation as the source of the problem.

ISSN:0003-150X    

DOI:10.1002/j.1551-8833.1994.tb06283.x

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

Membrane processes may offer small facilities a less expensive alternative for the removal of particles and organic materials.Costs of several ultrafiltration and nanofiltration processes are compared with the cost of conventional liquid‐solid separation with and without GAC adsorption for small facilities. Data on raw‐water quality, permeate flux, recovery, frequency of backflushing, and chemical dosage obtained from a pilot study were used with a previously developed model for membrane costs to calculate anticipated capital and operating costs for each instance. Data from the US Environmental Protection Agency were used to estimate conventional treatment costs. All of the membrane process calculations showed comparable or lower total costs per unit volume treated compared with conventional treatment for small facilities (<200,000 m3/d or about 5 mgd).

ISSN:0003-150X    

DOI:10.1002/j.1551-8833.1994.tb06284.x

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

Feedwaters with TDS concentrations up to 6,500 mg/L are being treated by membrane processes to drinking water standards.The objectives of this survey were to determine the number of membrane plants currently operating in North America, assess industry growth, and identify trends. In December 1993, the combined capacity of the more than 190 plants was>215 mgd. Approximately 80 percent are reverse osmosis (RO) units, and 20 percent are electrodialysis reversal (EDR). Recovery rates as high as 85 percent for RO and 94 percent for EDR systems are being used for normal operation. The blending of raw water with the membrane product water is common practice. Different membranes are sometimes being used for plants with two or more stages.

ISSN:0003-150X    

DOI:10.1002/j.1551-8833.1994.tb06285.x

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

A high‐permeability, charged nanofiltration membrane was successfully operated for organics removal under conditions of higher‐than‐normal recovery and flux rate.A membrane filtration pilot plant was operated for one year to evaluate the removal of natural organic matter and disinfection by‐product precursors from a highly colored groundwater in Orange County, Calif. Two nanofiltration (NF) membranes—a traditional softening membrane and a high‐permeability, charged membrane—were selected for pilot‐scale testing based on bench‐scale tests of eight NF and ultrafiltration membranes. The high‐permeability NF membrane demonstrated superior organics removal at very high recovery and flux. It also allowed most inorganic constituents to pass through. The concentrate of low total dissolved solids reduced inorganic fouling and made concentrate reuse possible. The article also presents preliminary design criteria and a cost opinion for full‐scale treatment facilities.

ISSN:0003-150X    

DOI:10.1002/j.1551-8833.1994.tb06286.x

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

Under conditions typical of drinking water, copper demonstrates a tendency toward increased corrosion that is inhibited only by the presence of chloride or bicarbonate at certain pH values.Copper passivation was examined in simple solutions that contained bicarbonate, chloride, perchlorate, nitrate, or sulfate at pH 5.5, 7.0, 8.5, and 10. Copper corrosion rates increased with aging in the presence of sulfate, nitrate, or perchlorate at all pH values, whereas copper passivated in the presence of chloride at pH ≥7.0. Bicarbonate ion was discovered to have a dual nature that was pH‐dependent, causing activation (increased corrosion rates) after aging at pH ≤7.0 and passivation at pH ≥8.5. Activation in the presence of bicarbonate was due to catalysis of oxygen reduction (cathodic) reactions, whereas sulfate, nitrate, and perchlorate increased the copper oxidation (anodic) reaction rates after aging.

ISSN:0003-150X    

DOI:10.1002/j.1551-8833.1994.tb06287.x

出版商:Wiley    

年代:1994

数据来源: WILEY

ISSN:0003-150X    

DOI:10.1002/j.1551-8833.1994.tb06288.x

出版商:Wiley    

年代:1994

数据来源: WILEY