Use of rainwater and gray water in buildings.
Technical standards and specifications
Armando Silva Afonso | Carla Pimentel Rodrigues
Associação Nacional para a Qualidade nas Instalações Prediais
(ANQIP), Polo Operacional da Universidade de Aveiro
Due to not only demographic growth but, fundamentally, to economic development and lifestyle, drinking water is now a scarce resource that, from being a community and heritage asset, has become an economic good over the past decades. Climate change has aggravated this scenario and it is expected that in some countries, such as Portugal, the predictable reduction of precipitation or the change in its regime may, in the short/medium term, create situations of water stress.
As a scarce good, essential to life, its efficient use should be a priority at all levels. The need for the efficient use of water was already recognized as a national priority in 2001, through the publication of PNUEA – Programa Nacional para o Uso Eficiente da Água. Among the actions proposed in this program, several measures applicable in the building water cycle (indoor and outdoor uses) can be mentioned in the scope of rainwater use and grey water reuse. Unfortunately, this program was never implemented, although it was updated in 2012.
The use of rainwater or grey water in buildings can avoid the supply of drinking water for some specific uses, allowing, in addition to the reduction of water abstracted (and the pressure on water bodies), a reduction in energy consumption and GHG emissions. With specific reference to rainwater harvesting (collection) in buildings, it can also contribute to the reduction of flood peaks in urban areas, which is why it has seen a growing interest in many countries, even without water scarcity or water stress.
In Berlin, for example, rainwater harvesting (collection) systems have been successfully introduced on an urban scale in the rehabilitation of large spaces such as Potsdamer Platz, where rainwater collected from the roofs of 19 buildings (32,000 m2) is stored in a 3,500 m3 tank.
In Tokyo, more than 750 public and private buildings have introduced rainwater collection and utilization systems. In Brazil, the Brazilian technical standard ABNT NBR 15527 was published in 2007, and rainwater harvesting (collection) is mandatory, for example, in S. Paulo. In Spain, some local authorities require new buildings to have greywater reuse systems as part of a strategy to deal with water scarcity.
However, the reuse of rainwater and grey water in buildings carries environmental and health risks that should require appropriate controls. This recommendation is included in the “Blueprint Water” of the European Commission. It is therefore considered that the development and dissemination of technical specifications for the use of rainwater and grey water reuse is essential to encourage the voluntary use of these systems, but the need to reduce health risks also requires mandatory certification of these systems.
In Portugal, ANQIP (Associação Nacional para a Qualidade nas Instalações Prediais), a sector association for water and sewage building installations, whose members include companies, universities and managing entities has developed a broad technical and scientific base in the field of rainwater harvesting (collection) and grey water reuse in buildings, which includes the preparation and publication of technical specifications and the creation of voluntary certification systems for installations. In this last aspect, ANQIP was even the first European entity to respond to the demands of the “Blueprint Water”.
In 2007, ANQIP established a Technical Committee (CTA 0701), which produced, based on the Brazilian and German experiences, among others, and on their adaptation to the national reality, two Technical Specifications: ETA 0701, aimed at the design, sizing, installation and maintenance of rainwater treatment systems, and ETA 0702, aimed at the technical and sanitary certification of these systems. Note that ETA 0702 (for the certification of facilities) was preceded by extensive field work, with monitoring of pilot facilities over several months and in terms of numerous parameters, including legionella.
Recently, in 2018, a European Standard (EN 16941-1) for these rainwater harvesting (collection) systems in buildings was finally published, which was very much based on German standards, but did not take into account the necessary adaptation of these systems to different climatic realities, as is the case of southern countries.
This is one of the reasons that justify the planned revision, soon, of this standard, in a process that will include the participation of ANQIP. Note that the European Standard also did not contemplate, in its initial version, the issues of certification of facilities. For this reason, The ANQIP ETA 0701 and 0702 continue to be the reference used in Portugal for these systems.
Regarding building systems for grey water reuse in buildings, ANQIP followed a similar procedure, having published, already in 2009, the Technical Specification 0905, for design, sizing, installation, control and maintenance of these systems, and the ETA 0906, for the technical and sanitary certification of the installations. Meanwhile, in 2021, a European Standard for these systems was also published (EN 16941-2), which added nothing, however, to what was already established 12 years earlier in Portugal, through ANQIP and ETA, keeping these technical specifications, more complete, demanding, and exhaustive than the European Standard, as a reference among us.
It should be noted that ETA 0905 and 0906, like EN 16941-2, are aimed at the so-called collective or long retention time installations. In addition to these systems, there are also
small individual facilities for grey water reuse on the market, such as washbasins coupled to toilets, where the water used in the washbasin is then used to flush the toilet. These compact appliances, to which ETA 0905 and 0906 do not apply, are subject to individual certification by ANQIP, in the category “efficient products” (catalog available at www.anqip.pt). In addition to these products, small compact grey water regeneration plants have recently appeared on the market, which are an intermediate solution between individual plants and large collective plants and have also been subject to technical and sanitary certification by ANQIP, for the safety of users.
