B-28 (Buildings) / B-10 (Products) Accounting of different types of waste water treatment

Aspect B-28 (Buildings) / B-10 (Products) Accounting of different types of waste water treatment
Description
The environmental impacts are different for the various methods of waste water treatment. The system boundaries for waste water treatment considered within the studies (e.g. public sewage system, on-site treated water) and the classification of waste water treatment need to be consistent.

related study objective

stand-alone LCA comparative assertion

related study phase

goal and scope definition inventory analysis (LCI) impact assessment (LCIA) interpretation reporting

relevant for

new buildings existing buildings construction products screening LCA simplified LCA complete LCA
Provisions This aspect should be modelled only when it is a special focus of the study, or for a complete LCA, unless it is believed to be a dominant contributor to the environmental impacts of the assessed system. In this case, the real situation should be modelled, and alternative scenarios can be developed as sensitivity analyses. These scenarios should be documented as transparently as possible.
Rules from:

EN 15978

8.6.6 Scenarios for operational water use (Module B7)According to EN 15978, For building studies, water use (treatment and supply) and waste water treatment should be considered in Module B7.  Energy to heat or cool water used would be included in Module B6.

EN 15804

6.3.4.4.3 B6 – B7 use stage information modules related to the operation of the building:According to EN 15804, Module B7 deals with operational water use within the building.  As such, in product LCA it would be included only where building integrated technical system products have an operational water demand. Additionally, the impacts of waste water treatment should be considered for the water used.Product-related water use and waste water treatment during the extraction or manufacturing process should be included in Modules A1–A3, during construction in Module A5 and from maintenance (e.g. cleaning) in Module B2.
Guidance
In general, waste water treatment as part of material production is included in background datasets. The use of generic waste water treatment data from background databases may ease the assessment of this aspect, and should typically be sufficient for construction-related LCA studies (except for studies that include processes with significant pollution of waste water, such as varnishing processes with high waste water runoff).Regarding the way to treat wastewater in an improved model e.g. for a complete LCA, all types of wastewater treatment should be considered: 1) on-site treatment (different technologies); 2) public sewage system (combined sewer system, both rain and grey/blackwater or separate sewer system); 3) combined technologies (e.g. one technology for on-site treatment and one technology for the  public sewage system). Specific LCA data representative of each technology should be used (if available).

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