Introduction

Tamil Nadu has around 50 functional Sewage Treatment Plants (STP), of which 31 STPs co-treat Fecal Sludge (FS) from Onsite Sanitation Systems along with sewage. There are multiple challenges involved in the co-treatment of FS. Some of the challenges are due to the difference in characteristics of sewage and FS which includes parameters such as Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), and solids content. Based on field observations by the TSU, handling of grit has turned out to be one among the key challenges for co-treatment. This paper discusses in detail the challenges caused by grit on co-treatment infrastructure, operation and maintenance practices as well as the potential solutions for addressing the same. It will further discuss the limitations and practical considerations required while implementing the same based on ongoing field studies.