Addressing Water Challenges with the Zero Water Building
～Kurita Innovation Hub～

Japan has a high rate of water supply and sewage system coverage, clean water is readily available from taps, and wastewater is efficiently managed. Consequently, people do not often experience water-related issues, making it difficult for them to perceive the immediacy of water challenges. Data shows that Japan consumes more water per capita relative to its water resources than many other countries.

It may seem that issues like water resource depletion and pollution are distant concerns that do not affect our daily lives. However, Japan significantly depends on foreign water resources. The country imports a large number of food items and industrial products, which utilize substantial amounts of water during their production. Should there be any disruption in these imports, necessitating a shift to domestic production, the required water for agriculture, livestock, and industry would exceed domestic supplies. Thus, the global water crisis is indeed a close concern.

Japan’s water and sewage systems, originally constructed during the period of rapid economic growth, are confronted with challenges such as aging infrastructure and increasing regional disparities in maintenance costs due to demographic decline. Additionally, the rising frequency of sudden heavy rains and flooding increases the strain on sewage systems. In urban areas, the challenge of expanding water infrastructure for large-scale redevelopment projects is exacerbated by the limited space available under narrow roads, already crowded with existing structures. For these reasons, it is vital not to increase the load on our infrastructure.

Recently, the architectural industry has begun to focus on the concept of the Zero Water Building (ZWB). A ZWB is a “self-sustaining water recycling building” designed to minimize infrastructure strain by optimizing water conservation and wastewater reuse within the building and allowing rainwater to permeate the soil on the premises to return back to the original water source. A building qualifies as a ZWB when the total volume of water consumed, minus the volume of water reused and returned, is zero or negative.

While installing water treatment facilities for ZWB may increase the energy usage and CO2 emissions of the building itself, it has the potential to reduce these impacts across the wider community. ZWBs, which recycle water, contribute to energy conservation and CO2 reduction when compared to conventional water treatment at municipal facilities. It is needless to say that these systems are also critical for Business Continuity Planning (BCP) and Life Continuity Planning (LCP) during disasters. In situations where infrastructure failures disrupt water supply and drainage, businesses and daily living conditions can quickly deteriorate. A ZWB, equipped with facilities for utilizing rainwater and well water, can more easily secure essential water resources until recovery.

Internationally, there are several certification systems that evaluate ZWBs, including the LEED Zero water certification in the United States and the Net Zero Water Rating System in India. High ratings can enhance real estate values and serve as attractive assets for ESG investment. To promote the efficient utilization of water resources, the establishment of an evaluation index in Japan is anticipated.

Located in Akishima City, Tokyo, the “Kurita Innovation Hub” serves as a research and development center for Kurita, a leader in water treatment technology. Nikken Sekkei pioneered the application of the ZWB concept in Japan, optimizing water use in the architectural design. Akishima City, unique in Tokyo for sourcing its water exclusively from groundwater, is recognized as a “city of water recycling.” This is due to regulations promoting the infiltration of rainwater into the soil instead of discharging it into sewage systems. The facility is divided by a public road, with R&D facilities to the north and a multifunctional building to the south, connected by a bridge.

In an effort to reduce potable water usage across the entire facility, ultra-water-efficient toilets and faucets have been installed. Reclaimed water is used for all needs except for drinking and hand washing. The R&D building includes both a wastewater treatment plant and a pure water production plant. By segregating the wastewater and fine-tuning the treatment process for each type, high rates of water recovery and energy efficiency are achieved with minimal strain on equipment.

Befitting of a water-focused company, numerous metal pipes designed with a water pipe motif have been attached to the building’s exterior to function like louvers. These metal pipes are not only aesthetically pleasing but also serve as rain gutters, effectively collecting rainwater. A large rainwater retention and infiltration tank installed on the site, approximately 1,600 square meters in size, temporarily stores rainwater conveyed from the metal pipes and allows it to permeate the soil. This enhances the effective use of water resources, contributes to the replenishment of groundwater aquifers, and reduces the impact of water-related disasters.

While awareness of water issues is not yet fully integrated into daily life in Japan, there may soon come a time when water is not taken for granted. As public understanding of water challenges and the importance of water cycles improves, we can expect the promotion and implementation of the ZWB concept. Utilizing its extensive experience in energy-efficient architecture, Nikken Sekkei will continue to offer ZWB solutions tailored to various conditions, actively addressing water issues through architectural innovation.

Photos TOP, 2, 3: Takuya Seki