5.1 There is increasing concern regarding water quality. The first national-scale U.S. examination of these organic wastewater contaminants in streams, conducted by the Toxic Substances Hydrology Program of the U.S. Geological Survey (USGS), indicated that a broad range of chemicals found in residential, industrial, and agricultural wastewaters commonly occurs in mixtures at low concentrations downstream from areas of intense urbanization and animal production. The chemicals include pharmaceuticals, natural and synthetic hormones, detergent metabolites, plasticizers, insecticides, and fire retardants. One or more of these chemicals were found in 80 % of the streams sampled.6

5.2 This practice may be used by building owners and design professionals to assess water stewardship impacts of a residence. In particular, it is intended to inform design decisions and operation decisions regarding estimated wastewater quality impacts of a building.

5.3 This practice may be used by planners and water treatment professionals to assess water stewardship impacts of a residential area. In particular, it is intended to inform infrastructure decisions regarding estimated wastewater quality impacts of a residential service area.

5.3.1 This practice may be used to estimate the types and amounts of non-biological wastes entering a wastewater system. Such knowledge is becoming increasingly important in developing sustainable approaches to water stewardship.

5.4 Table 2, Environmental Load for Average U.S. Single-Family Home, does not list all chemicals used in homes; in order to obtain a more accurate estimation, the chemicals used in specific homes should be listed. In addition, it may be helpful to monitor wastewater to determine variances, if any, from the estimated environmental load.

1.1 This practice provides a set of instructions for estimating the environmental load of residential water, as it is discharged from a residence. The environmental load is calculated based on the number and type of fixtures in the home, the common household chemicals used, and the number of people in the home. While the format is broadly applied internationally, the parameters stated herein reflect North American averages and would need to be modified if used elsewhere.

1.1.1 Averages Method—The Averages Method provides an estimate of the annual environmental load for the average U.S. single-family home based on 2000 U.S. Census2 and 2007 U.S. Census Data3 and U.S. EPA/625/R-00/008 characterization of residential wastewater flows.4

Note 1: Census 2000, taken April 1, 2000, counted 281 421 906 people in the 50 states and the District of Columbia. The questionnaire included seven questions for each household: name, sex, age, relationship, Hispanic origin, race, and whether the housing unit was owned or rented. In addition to these seven questions, about 17 percent of the households got a much longer questionnaire including questions about ancestry, income, mortgage, and size of the housing unit.

1.1.2 Unique Product Parameters Method—The Unique Product Parameters Method provides an estimate of the annual environmental load, where the home/product parameter values are the same as those used for the Averages Method except for estimated amounts of chemical contaminants listed in Table 1 or average total annual use of products as listed in Table 1, or both.

1.1.3 Adjusted Averages Method—The Adjusted Averages Method provides an estimate of the annual environmental load, where home/product parameter values differ from those used for the Averages Method, except that chemical contaminants associated with products do not vary. (Table 1 remains the same for: Typical Water Contaminants, Estimated Amount of Contaminant in Product (%), and the Percent Waste.)

1.1.4 Additional/Alternative Chemicals Method—The Additional/Alternative Chemicals Method provides an estimate of the annual environmental load, of chemicals used that are not listed in Table 1.

1.1.5 The Unique Product Parameters Method, Adjusted Averages Method, and Additional Chemicals Method may be used in combination with each other.

1.2 Instructions are provided for a single-family home. Estimates may be expanded to an aggregate number of single-family homes by assuming an average home size and multiplying by the number of homes. Estimates may be adapted to multi-unit residential buildings by factoring the home parameters for size, occupancy, and fixtures as necessary.

1.3 For the purpose of this practice, environmental load refers to chemical contaminants that may be dissolved or suspended in water.

1.3.1 Estimates of environmental load do not include organic matter common for urine, feces, and vomit.

1.3.2 Estimates of environmental load do not include bulk food waste such as kitchen scraps.

1.3.3 Estimates of environmental load do not include bulk cellulose waste such as toilet paper.

1.3.4 Estimates of environmental load do not include other solid wastes, such as wrappers, not covered by the waste groups covered in 1.3.1 through 1.3.3.

1.3.5 Actual environmental load may vary depending on types and amounts of chemicals used in a specific home and the number of people in the home.

1.4 The values stated in inch-pound units are to be regarded as standard. No other units of measurement are included in this standard.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.