Environmental performance of a hybrid rainwater harvesting and greywater reuse system: A case study on a high water consumption household in Colombia

Rainwater harvesting systems (RWHS) and greywater reuse systems (GWRS) are prominent alternatives for urban water management, which contribute to improving water use efficiency and conservation. The evaluation of these systems has been based mainly on technical, social and financial aspects. Recently, some studies have analyzed the environmental performance of RWHS and GWRS separately, showing promising results associated with lower impacts in comparison to conventional centralized water distribution systems. However, from an environmental perspective, limited research has been done to evaluate hybrid systems that integrate RWHS and GWRS. This study aims to analyse and compare the environmental performance of a hybrid system with a centralized system in a high water consumption household located in Bucaramanga Metropolitan Area, Colombia. The Life Cycle Assessment methodology, using the GaBi software, was applied to quantify the environmental impacts of the two water system options. The implementation of the hybrid system saves about 131 m3/year of potable water, 42.5% of total potable water consumption and reduces flows to the wastewater treatment plant by 20%. The hybrid system has better environmental performance compared to the centralized system, with lower impacts observed for 12 out of the 13 midpoint impact categories considered and all 3 endpoint impact categories in the ReCiPe impact assessment method used. The operational phase causes greater environmental impacts compared to the construction phase and the processes involved in the treatment of potable water and wastewater significantly affect the environmental impacts in both water system options compared to other life cycle phases. Overall, our study confirms the environmental benefits of the hybrid system and provides evidence useful for decision-makers regarding alternative water systems. However, further study is needed to refine the input data used for some of the processes to reflect the specific context in Colombia.

Automated summary

Rainwater harvesting systems and greywater reuse systems are important alternatives for urban water management, improving water efficiency and conservation. This study evaluates and compares the environmental performance of a hybrid system with a centralized system, finding that the hybrid system saves water and reduces wastewater flow, resulting in better environmental impacts overall.