The contamination of canals and rivers by wastewater is a growing environmental concern that threatens aquatic ecosystems and human health. This study employed a pre-post experimental design, alongside research and development methodologies, to analyze and design a small-scale solar-powered wastewater treatment system. The system was installed and demonstrated in the study area to assess its effectiveness. This research aims to analyze the quality of domestic wastewater sources and monitor the water quality in Samwang Canal, located in Bangbuathong Sub-district, Nonthaburi province, Thailand. It explores the use of alternative energy solutions in designing a small-scale wastewater treatment model for demonstration purposes, specifically assessing the effectiveness of this treatment model. Results indicated that the water quality across the community’s two main canals was below the surface water quality standards set by the National Environment Board (No. 8, 2537 BE). Key findings include Average dissolved oxygen levels ranged from 0.45 to 0.60 mg/L, Biochemical Oxygen Demand (BOD) levels were between 77.48 to 92.29 mg/L, Oil and fat concentrations were between 32.50 to 96.9 mg/L. The small wastewater treatment system effectively reduced pollutants, achieving reductions of: Oil and fat by up to 94.26%, BOD by 71.93%, and Total dissolved solids by 54.09%. Additionally, oxygen levels (DO) in the canal improved from 0.88 mg/L to 3.98 mg/L over a 100-meter stretch. These results demonstrate that the solar-powered system is an effective and viable solution for treating wastewater in similar canal systems. To address water quality issues further, it is recommended to reduce organic loads at primary sources by installing on-site treatment systems. Local authorities should also conduct regular training and community education on wastewater management, while community-led monitoring activities are essential for continuous water quality improvement.