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ISO/NP 25446 Guidelines for Gray Water Reuse in Building

Source:
ISO
Committee:
B/505/50 - Water reuse
Categories:
Information management | Standardization. General rules
Comment period start date:
Comment period end date:

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Scope

This document provides guidelines for the design and management of gray water reuse system in buildings. This document is applicable to newly built, expanded, or renovated residential buildings, hotels, apartments and similar structures, with the aim of achieving advanced technology, safety, health, and economic efficiency. This document covers gray water reuse including both standard and high grade gray water. It provides the recommendations on specific design methods, process, and parameters, and can be directly used to guide engineering design. This document includes: (1) Scope of the guidelines; (2) Normative references; (3) Terms, definitions, and abbreviations; (4) Raw-water, quantity and quality of gray water; (5) Collection system of gray water; (6) Treatment process of gray water; (7) Reuse system of gray water; (8) Safe guarding and monitoring control.

Purpose

Affected by factors such as population growth, pollution, and climate change, the pressure of global
water scarcity is constantly increasing. Over the past 20 years, the global per capita freshwater supply
has decreased by more than 20%. Faced with the challenge of water scarcity, many countries have
successfully improved their water resource management practices. Enhancing comprehensive water
resource management strategies and technologies have become the top priority in addressing water
resource crises.
Treated urban sewage, available nearby with a stable and reliable quantity, is an important secondary
water source for cities. It is basically unaffected by seasonal, climatic, flood and other conditions.
Internationally, wastewater recycling has become a key strategy for many countries and regions to
alleviate water resource crises. Sewage is a mixture of black water and gray water. Black water refers
to wastewater from toilets, containing high pollutant concentrations and incurring high treatment costs.
Gray water, however, refers to less polluted wastewater from showers, laundry, hand washing, and
kitchens.
The reuse graywater in building has gradually developed in recent years as a method for wastewater
recycling. The volume of graywater in buildings is large, but the concentration of pollutants is low. It can
be collected, treated, and reused nearby on a single building or household. This method features low
construction and treatment costs and flexible usage. The reclaimed water can be reused for toilet
flushing, irrigation, road cleaning, and other purposes. It is a low-cost, efficient, and reliable
technological approach that has gradually gained recognition from experts and engineers worldwide.
In recent years, many countries have developed innovative cases and applications of greywater reuse
in building, including China, Japan, Israel, United States, and Australia etc. China for example has
made original innovations and engineering practices of the reuse of gray water in buildings across the
country, forming a reliable and stable comprehensive system for indoor collection, treatment, and
reuse.
However, there is currently a lack of international standards and specifications for the reuse of
graywater in buildings. The absence of global, universal technical solutions for reuse system forms,
treatment methods, and reuse applications greatly limits the widespread promotion and application of
graywater reuse technology in buildings. This document aims to develop technical guidelines for
graywater reuse approach in building applicable to different countries worldwide, providing reliable
technical solutions to address the global water crisis 

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