Water and wastewater sector actively participates in circular economy (CE) transition; however, there is no official CE monitoring framework to measure the level of progress toward the CE model in this sector. The paper presents a set of environmental indicators that could support water and wastewater treatment companies in the assessment of CE implementation. CE indicators were grouped into six areas of CE implementation in this sector: reduction—prevention of wastewater generation; reclamation (removal)—contamination removal from water and wastewater; reuse—water reuse for nonpotable usage; recycling—water reuse for potable usage; recovery—recovery of raw materials and energy from water‐based waste; and rethink—rethinking use of raw materials. The following indicators were proposed in specific CE areas: reduction—tap water consumption reduction, wastewater generation reduction, waste reduction, sewage sludge generation reduction, and water footprint; reclamation—pollutants removal from water and pollutants removal from wastewater; reuse—water reuse from wastewater for nonpotable usage and recycling of technical water for nonpotable usage; recycling—water reuse from wastewater for potable usage; recovery—raw materials recovery, bio‐based fertilizers, energy recovery, processing of sewage sludge, composting of sewage sludge, biogas production, and processing of ashes; and rethink—CE technologies, life cycle assessment reports, CE products, and CE business models, industrial symbiosis, and carbon footprint. The proposed CE indicators can be used not only to assess the level of transformation toward CE but also to support further policies on strategic CE initiatives in organizations operating in the water and wastewater sector. Moreover, they could support the strategic planning of further CE initiatives in organizations. The proposed list of CE indicators is not closed because in the coming years, more and more CE solutions are expected to be developed and implemented in water and wastewater treatment plant companies, involving also economic and social aspects, in order to support the sustainable development.
