Drinking water standard

The quality of drinking water is kept safe by a set of regulations that define the maximum concentration of an extended list of compounds—these are the drinking water standards. 

Issuing regulations for safe drinking water may at a first glance seem as a simple and straightforward task. In reality it turns out to be rather complicated and a continuous operation. Let us have a glimpse at the process  

Marcel Dekker, Inc. 270 Madison Avenue, New York, New York 10016 

A long list of compounds is treated by the drinking water regularities. They include the following groups of compounds  

The values and lists of regulated parameters have to be acquired from local authorities, as they differ from one country to another and are frequently updated. 

A total of 83 contaminants are currently required to be regulated under the SDWA of 1986, and 77 substances or classes of substances make up a priority list of contaminants for regulation after the EPA completes standards for the initial list of 83. Although the EPA was required to establish MCLs and maximum contaminant level goals (MCLGs) for 25 of the contaminants by January, 1991, and every 3 years thereafter, the EPA has not kept up with this pace. 

In the United States, current Stage 1 Major Contaminant Level (MCL) of total trihalomethanes (THMs) and five haloacetic acids (Hv A5) are at 80 and 60 4gL, respectively. At Stage 2 this will be lowered to 40 and 30 igL- (US EPA (1998), Dal-Cin et al, (1995)). In Germany maximum admissible THM concentrations are as low as 10 pmL (McCann (1999)). 

However, drinking water standards do not exist in Australia and the 1996 guidelines are currently being reviewed, including THMs for the first time. The 1987 guidelines are still not commonly applied (Vitanage et al (1996)). 

This results in higher treated water qualities in countries like the US or Europe, where standards are generally very high and source waters of poor quality due to high population densities. 

Treatment aims to meet drinking water guidelines. The removal of disinfection by-products (DBPs) and biodegradable organics are primary targets. Taste and odour compounds are also important. 

A variety of hybrid processes can also be used, such as pretreatment of powdered activated carbon (PAC), coagulation, conventional treatment, resin or cartridge filtration followed by ion exchange, adsorption, or membranes. 

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In 1980, the EPA pubHshed ambient water quaHty criteria for silver. An upper limit of 50 f-lg/L in natural waters was set to provide adequate protection against adverse health effects (38). In 1992, EPA deleted the human health criteria for silver from the ambient water quaHty criteria to be consistent with the drinking water standards (39). 

At the Taylor Road landfill (originally intended for the disposal of municipal refuse only), unknown quantities of hazardous wastes from industrial and residential sources were deposited. During the period when the landfill was active, soil and groundwater samples collected at the site were found to contain concentrations of volatile organic compounds and metals above acceptable safe drinking water standards. Analysis of samples collected from private drinking water wells indicated that contamination... 

Today resource limitations have caused the United States Environmental Protection Agency (USEPA) to reassess schedules for new rules. A 1987 USEPA survey indicated there were approximately 202,000 public water systems in the United States. About 29 percent of these were community water systems, which serve approximately 90 percent of the population. Of the 58,908 community systems that serve about 226 million people, 51,552 were classified as "small" or "very small." Each of these systems at an average serves a population of fewer than 3300 people. The total population served by these systems is approximately 25 million people. These figures provide us with a magnitude of scale in meeting drinking water demands in the United States. Compliance with drinking water standards is not... 

Secondary Drinking Water Standards Contaminant SMCL... 

Water sample collection techniques differ depending on the source being tested. The minimum number of water samples collected from a distribution system which are examined each month for coliforms is a function of the population. For example, the minimum number required for populations of 1,000 and 100,000 are 2 and 100, respectively. To ascertain compliance with the bacteriological requirements of drinking water standards, a certain number of positive tests must not be exceeded. When 10-ml standard portions are examined, not more than 10 percent in any month should be positive (that is, the upper limit of coliform density is an average of one per 100 ml). 

A water meeting drinking water standard quality. 

DHS. 1999. California drinking water standards. Department of Health Services.. httD //www.dhs.cahwnet.gov/ps/ddwem/chemicals/mcl/mclindex.htm Table 1. May 10, 1999. 

EPA. 2000a. Drinking water standards and health advisories. Office of Water. U.S. Environmental Protection Agency. EPA 822-B-OO-OO1. 

FSTRAC. 1988. Federal-State Toxicology and Regulatory Alliance Committee (FSTRAC) (database). Chemical Communication Subcommittee. Summary of state and federal drinking water standards and guidelines. March, 1988. 

EPA has set a drinking water standard of 5 parts of trichloroethylene per one billion parts of water (ppb). One ppb is 1,000 times less than 1 ppm. This standard became effective on January 9, 1989, and applies to community water systems and those that serve the same 25 or more persons for at least 6 months. EPA requires industries to report spills of 1,000 pounds or more of trichloroethylene. It has been proposed that this level be reduced to 100 pounds. 

Cotruvo JA. 1988. Drinking water standards and risk assessment. Regul Toxicol Pharmacol 8 288-299. 

There is a discrepancy between the cyanide criteria for both aquatic and drinking water standards and the current analytical technology. The criteria are stated for free cyanide (which Includes hydrocyanic acid and the cyanide ion), but the EPA approved analytical methodology for total cyanide measures the free and combined forms (11). This test probably overestimates the potential toxicity. An alternative method (cyanides amenable to chlorination) measures those cyanide complexes which are readily dissociated, but does not measure the iron cyanide complexes which dissociate in sunlight. This method probably tends to underestimate the potential toxicity. Other methods have been proposed, but similar problems exist (12). The Department of Ecology used the EPA-approved APHA procedure which includes a distillation step for the quantification of total cyanide (13,14). A modification of the procedure which omits the distillation step was used for estimation of free cyanide. Later in the study, the Company used a microdiffusion method for free cyanide (15). 

Federal drinking water standards for cyanide have been withdrawn and are not included in the latest publication. The Public Health Service limit for drinking water had been 200 ppb. Whether the limit was expressed as free or total cyanide was in question at the time. The fresh water aquatic cyanide criterion is 3.5 ppb as a 24-hour average, not to exceed 52 ppb at any time. 

Cyanide contamination creates special public information problems, e.g. it is difficult to explain why cyanide is not included in the current drinking water standards but that aquatic organisms are affected at relatively low cyanide concentration. There is confusion on whether fresh water standards are based on free or complexed cyanides. Fortunately, the provision of a permanent drinking water supply to each affected household removed risk assessment as a major issue. 

EPA 822-B-OO-OOl, US Environmental Protection Agency, Drinking Water Standards and Health Advisories, Office of Water, Washington, DC (2000). 

Water for injection (WFI) is the most widely used solvent for parenteral preparations. The USP requirements for WFI and purified water have been recently updated to replace the traditional wet and colorimetric analytical methods with the more modern and cost-effective methods of conductivity and total organic carbon. Water for injection must be prepared and stored in a manner to ensure purity and freedom from pyrogens. The most common means of obtaining WFI is by the distillation of deionized water. This is the only method of preparation permitted by the European Pharmacopoeia (EP). In contrast, the USP and the Japanese Pharmacopeias also permit reverse osmosis to be used. The USP has also recently broadened its definition of source water to include not only the U.S. Environmental Protection Agency National Primary Drinking Water Standards, but also comparable regulations of the European Union or Japan. 

Besides providing an environment for aquatic organisms, surface water is often used as a source of drinking water. The National Primary Drinking Water Standards are based on total chromium, the limit being 0.1 mg/L.19... 

CDHS database, MTBE Drinking Water Standards and Monitoring Results, California Department of Health Services. Available at www.dhs.ca.gov/ps/ddwem/chemicals/MTBE/mtbeindex.htm, April 2006. 

Interim primary drinking water standards 401 KAR 35 31 NREPC 1988... 

Fig. 32.2. Remediation of the aquifer shown in Figure 32.1, as the simulation continues. After water contaminated with Pb++ displaces half of the aquifer s pore volume, clean water is flushed through the aquifer until a total of 30 pore volumes have been replaced. Flushing attenuates Pb++ concentration in the groundwater (top), so that it gradually approaches drinking water standards (MCL, or Maximum Contamination Level), and slowly displaces most of the sorbed metal from the Fe(OH)3 surface, primarily from the weak surface sites.

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