Annotation: Introduction. The article explores conceptual approaches to building a system for accounting and analyzing costs associated with the design of modern water treatment module ecosystems. Contemporary environmental challenges require the implementation of innovative technologies that enhance water purification efficiency and promote sustainable development. The focus is on the development and improvement of module systems that ensure maximum water treatment process efficiency, cost minimization, and harmonious integration into the overall ecosystem of the enterprise. Current environmental conditions and increasing water quality demands make the water treatment technology market one of the most critical sectors for the global economy. Globalization in this sphere and the development of a competitive environment compel businesses to seek new approaches to designing and implementing water treatment systems. This drives the need for innovative solutions that combine environmental safety, economic efficiency, and long-term operational sustainability. Objective. The objective of this study is to reveal conceptual approaches to the design of modern water treatment module ecosystems, analyze their efficiency, and their implementation in enterprises. The study also addresses the systematization of costs associated with module implementation and their integration into the overall environmental management system. Materials and Methods. The study materials include: 1) modern technological solutions and regulatory acts related to water treatment; 2) scientific works of domestic and foreign authors exploring the design and operation of water treatment systems. The analysis involved methods of theoretical generalization, formalization, and synthesis to build a functional scheme for modular water treatment systems within the enterprise ecosystem. Results. The article reveals the sequence of designing the water treatment module ecosystem that ensures the effective operation of an enterprise under modern conditions. Key components of the water treatment system and their role in the overall cost structure of the enterprise are presented. A typology of costs associated with the implementation of water treatment modules is also proposed, and their place in the management and accounting systems is defined. Prospects. Further research may focus on developing methodologies for analyzing the operational costs of water treatment modules, as well as their documentation in accounting.