Water resource management, circular economy, wastewater treatment, and recovery have become necessary in climate, economic, and socio-environmental change and decreasing precipitation. State services, local authorities, and economic actors worldwide are making great efforts to integrate wastewater treatment plants into recycling treated water in irrigation and industry. This will allow concrete and adapted solutions for developing and developed countries to emerge. Indeed, well-adapted treatment channels must be optimized to meet rigorous standards. This makes it possible to improve the quality of treated water, reduce the environmental impacts of treatment activities, and enhance the value of wastewater resources, as well as, subsequently, the application of the circular economy. Indeed, scientists must support public and private actors in the design, sizing, operation, and optimization of wastewater treatment and recovery facilities. To address drought problems, water treatment with recycling is necessary. This requires the integration of a practical methodology to help treatment plant managers properly operate the treatment lines to produce recyclable water. This chapter aims to establish a coherent methodology that constitutes a decision-making aid to improve the operation of treatment plants increasingly. This chapter remains very interesting by specifying the methodology to follow to operate the treatment lines in particular properly: • Collection of essential data at the plant level (assessments already carried out) • Conduct an assessment of the current state • Conduct a report on the current state of the plant based on the database and the assessment carried out at the current state • Proposal of an action plan • Implementation of the action plan • Monitoring of the action plan. In addition, several points should be highlighted in practice to assess a methodology to follow, in particular for: • The rate of chemical reagents to be integrated during physico-chemical treatment • The aeration rate which makes it possible to minimize the cost of producing well-treated water • The rate of recycling of water from one stage to another • The rate of sludge extraction at the primary and secondary treatment level • Assess the decontamination efficiency by different stages of the plant • Assess the decontamination efficiency of the plant between the inlet and the outlet • Equipment operating time • Waste production rate, compared to the treated flow rate (daily, monthly) • Electricity and reagent consumption rate compared to the treated flow rate (daily, monthly) • Hydraulic operating parameters: • Retention time along the different treatment stages • Operating parameters of the biological process (volume load, mass load, etc.) • Malfunction of the station and proposed solutions. Finally, this allows for the proper optimization of the conditioning of the treatment by using an apparent and practical methodology to produce water that meets industrial standards for irrigation or recycling.