Water is a vital resource for sustainable economic and social development. Water over-abstraction is one of the main threats to the environment. Most of the past works considered intra- and inter-plant integrations, in which reused water has been exchanged within a single plant before being transported to the centralised network. Excess wastewater that would be sent to the centralised system likely had the same quality and segregation was not necessary. For this study, only inter-plant and indirect water integration is considered. Water data generated by industries are considered to be directly transported to the centralised network with different wastewater qualities. This paper presents a mathematical programming formulation for centralised water reuse exchange in Eco-Industrial Park (EIP) considering wastewater segregation before centralised treatment with a single contaminant. The mathematical formulations are based on a superstructure that segregates wastewater based on quality before being transported to the centralised utility provider using water header. The main objective is to minimize freshwater consumption in the industry by utilizing regenerated water from the centralised utility provider. The model is coded and solved by using the General Algebraic Modeling System (GAMS) software with non-linear programming (NLP). The model is tested with a case study of three scenarios, each with different numbers of water headers. The results obtained show a significant freshwater saving of 98 % from the inter-plant indirect water integration in Scenario 3, which had the highest number of water headers and regeneration units.