Due to increasingly strict environmental regulations, the cost of handling various waste streams is gradually rising. Therefore, it is crucial to minimize unnecessary stream merging when designing distributed wastewater treatment systems, to reduce the overall treatment flow rate whenever possible. In a distributed wastewater treatment system, the wastewater streams are separated for treatment and only combined when necessary. This results in a significant reduction in the total treatment flow rate compared to traditional centralized treatment systems where all the streams are merged before treatment. Design of a distributed wastewater treatment system can be accomplished using pinch analysis and mathematical programming approaches. This paper suggests a straightforward approach for designing such networks, with the following steps in the design process: First, the primary function of each treatment unit is determined. Next, using the pinch method, the lowest treatment quantity is determined for the primary pollutant for each unit. Finally, a three-unit group is selected, with the pinch stream partially treated, the streams above the pinch completely treated, and the stream below the pinch completely bypassed. Two literature case studies demonstrate the viability and effectiveness of this strategy.