Both rectangular and circular configurations have been commonly used in clarifier basins. The relative merits of the two have been discussed at length for decades. Historically, the selection of rectangular versus circular clarifiers has been based on past experience and the preference of the design engineer or design company. Initial wastewater treatment plant designs in the United States were reasonably balanced between rectangular and circular when collector or scraper systems were designed from steel. With the introduction of biological treatment, corrosion became more of a concern and circular clarifiers became more popular. Non‐metallic chain and flight sludge collection systems for rectangular clarifiers (like our Polychem system) were introduced more than 20 years ago and have overcome the corrosion problem, leading to a resurgence of rectangular clarifiers, particularly for large wastewater treatment plants. Let’s compare the benefits of each configuration.