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At least 73 records · Page 4Linked to original sources
PubMed1999

Water purification systems: a comparative analysis based on the occurrence of disinfection by-products.

Trihalomethanes (THMs) are halogenated hydrocarbons, and are by-products of the chlorination of drinking water. Most THMs are formed in drinking water when chlorine reacts with naturally occurring organic substances such as decomposing plant and animal materials. Risks for certain types of cancer are now being correlated with the presence of disinfection by-products (DBPs). The present research uses gas chromatography to analyze the presence and levels of THMs in drinking water samples from a variety of sources. These include (1) municipal drinking water from two south Florida counties; (2) two brands of bottled water; (3) untreated residential well water; and (4) municipal tap water passed through additional water purification systems. The results are summarized in a tabular format, and the compliance of each water with existing US EPA-mandated standards is examined. General conclusions from this study are that all the waters tested complied with federal regulations regarding THM levels, properly functioning home filtration units may be quite effective in further reducing DBP concentrations and, as expected, non-chlorinated waters such as bottled water and residential well water contain lower THM levels.

Journal Article↗
PubMed1983

Generation of dimethylnitrosamine in water purification systems. Detection in human blood samples during hemodialysis.

Dimethylnitrosamine (DMNA), a carcinogen, was detected at levels up to 32 micrograms/L in dialysate from five of 16 dialysis units surveyed. Blood drawn from patients at one of these units in which DMNA was raised in the dialysate showed a significant increase in the amount of DMNA in the patient's blood when predialysis levels were compared with 15-minute intradialysis levels. The presence of a mixed-bed deionizer without an antecedent carbon filter appeared to be necessary for DMNA production. These data suggest that DMNA is generated in certain water purification systems and may then diffuse into the patient's blood. Guidelines for deionizer-treated water should be revised to include an activated carbon filter.

Adolescent↗
PubMed1964

USE OF CHEMICAL OXYGEN DEMAND VALUES OF BACTERIAL CELLS IN WASTE-WATER PURIFICATION.

Four methods for determining substrate recoveries in studies concerned with the partition of substrate between sludge synthesis and respiration were investigated. An energy balance comparing chemical oxygen demand (COD) removed with the summation of oxygen uptake and the COD of the cells produced yielded average recoveries closer to 100% than any of the other three methods tested. The standard COD test was shown to yield highly reproducible values when used to determine the COD of activated sludge. Although the protein and carbohydrate content of the cells varied with cell age, a concomitant variation in cell COD was not noted.

Bacteria↗
PubMedDate not supplied

[Water purification for hemodialysis].

An electrodialysis system has been designed to purify water. It comprises two units: a preliminary preparation unit and an electrodialysis one. The system consists of columns containing zeolite, activated carbon, and ion-exchange resins. Zeolite makes water free from mechanical impurities and iron, activated carbon adsorbs organic matter and chlorine ions, ion-exchange resins soften water. The electrodialysis unit is noted for its original design. Mathematical simulation has allowed the authors to optimize the design and to make a block that makes the process continuous without repolarization, which can decant the minimum levels of salt concentrates, thus decreasing energy supply to 2 W per liter. The unit is made as a pressure filter design having the platinum-titanium electrodes and membranes MK-40 and MK-45 made in Russia. The system operates automatically. Its all components are made in Russia.

Charcoal↗
PubMed1997

Efficacy of iodine water purification tablets against Cryptosporidium oocysts and Giardia cysts.

The ability to control water-borne diseases is critical for soldiers, hikers, and others who may need to drink directly from an outdoor source. Water-borne protozoan parasites that are specifically of concern are Giardia and Cryptosporidium because of their resistance to halogen disinfection. The purpose of this study was to determine the effectiveness of iodine tablets against Giardia and Cryptosporidium under general- and worst-case water conditions that might be found in the field. Giardia cysts and Cryptosporidium oocysts were exposed to iodine according to manufacturer's instructions (two tablets/L = 13-18 mg/L for 20 minutes). This dose inactivated 3-log10 of Giardia in general-case water and pH 9. In worst-case water, however, only about 35% of cysts were inactivated at pH 5. Fifty minutes were required to achieve a 3-log10 reduction at pH 5. Cryptosporidium oocysts were more difficult to inactivate. Only 10% were inactivated after a 20-minute exposure to iodine according to manufacturer's instructions; even after 240 minutes of exposure to iodine only 66-81% oocysts were inactivated. These data strongly suggest that iodine disinfection is not effective in inactivating Cryptosporidium oocysts in water. Because this organism is common in all surface waters, it is recommended that another method of treatment be used before ingestion.

Animals↗
PubMed2000

Microbiological water purification without the use of chemical disinfection.

OBJECTIVE: Point-of-use (POU) water treatment systems are self-contained units that can be used by recreational enthusiasts who normally obtain drinking water from untreated sources (i.e., rivers, lakes, etc). Microbiological water purifier units are capable of removing all waterborne pathogens. The purpose of this study was to evaluate a new technology (Structured Matrix) capable of micro-biologically purifying the water without the use of chemical disinfectants or an external power requirement. METHODS: Each of 3 identical portable water filtration units were evaluated for their ability to remove Klebsiella terrigena, poliovirus type 1, rotavirus SA-11, and Cryptosporidium parvum oocysts. Units were operated according to the manufacturer's instructions to process 378 L of water. Each unit was challenged with test organisms after 0, 94, 190, 227, 284, 340, and 378 L had passed through it. For the 227-L and 284-L challenges, a "worst-case" water quality (4 degrees C, pH 9, and turbidity 30 NTU) was used that contained 1500 mg/L dissolved solids and 10 mg/L humid acid. At 340-L and 378-L challenges, worst-case water quality was adjusted to pH 5.0. Units were tested after stagnation for 48 hours following passage of 190, 340, and 378 L of water. RESULTS: The geometric average removal exceeded 99.9999% for bacteria, 99.99% for viruses, and 99.9% for Cryptosporidium parvum oocysts. CONCLUSION: These units comply with the criteria guidelines for microbial removal under the United States Environmental Protection Agency's "Guide Standard and Protocol for Testing Microbiological Water Purifiers."

Animals↗