From the theory to the practice in water symbiosis, lessons learned and future research challenges

IntroductionThe ICTA-ICP building in the Universitat Autònoma de Barcelona (UAB) campus is a research center designed with the highest standards of sustainability. The building has 7,500 m2 (six floors) and holds a covered... [ view full abstract ]

Introduction

The ICTA-ICP building in the Universitat Autònoma de Barcelona (UAB) campus is a research center designed with the highest standards of sustainability. The building has 7,500 m² (six floors) and holds a covered rooftop with four areas designed for vertical farming purposes. The design aims to be efficient in terms of resource consumption. An important vector in saving resources is water because the region of Barcelona has water scarcity. The building has several systems and devices for minimizing water demand. The most notable is the rainwater collection, with a total storage capacity of 135 m³, among others such as recirculation of greywater from the sinks in the toilets or sensors for the activation of faucets. The rainwater collection system stores rainwater in one with 35 m³ for the building users’ purposes and another with 100 m³ tank used for irrigation in the building.

In this context, the water consumption of the building should be low. The goal of the study is to measure and evaluate the water flows of the building to see if these goals are being met and to propose improvements for the future.

Methodology

The main water flows of the building have been experimentally measured during a period of about 11 months, from 21/05/2015 to 15/04/2016. The measured flows are the following: water from conventional network supplied, greywater reused, rainwater used in the greenhouse and rainwater used for domestic uses (toilets, cleaning, etc.).

Some minor flows such as water used in the kitchen did not hold a flow meter and had to be estimated. Estimations were done in accordance with information from the building layouts, interviews with managers, building workers and architects and according to author’s expertise.

Results and discussion

Results show that the largest water consumption comes from conventional network, with a demand of 1,050 m³, more than half of which was generated in toilets (which are already efficiently designed) for flushing. Other important water flows are water consumption for cleaning and maintenance of the installations, labs or the kitchen (each of them between 6 and 11% of the water demand from the conventional network).

Although building greywater from washbasins was reused for flushing toilets (along with greywater from other uses), the total amount of grey water generated was 139 m³, which only covered 20% of the toilets demand. The rest (530 m³) had to be covered with network water.

Regarding the rooftop greenhouse, 80% of the water demand for irrigation (76 m³) was covered using rainwater.

Conclusions

Future building projects should foresee the amount of water consumed for each use and consider alternative systems to efficiently cover the demand. For instance, the demand of water for flushing toilets might have been covered with a combination of greywater and rainwater, also including eco-design for its construction. The authors propose the installation of flowmeters on certain strategic points of the water and rainwater networks for a better assessment of the hydric metabolism.