Effective wastewater management is a crucial component of sustainable development, public health, and environmental protection worldwide. As urban populations grow and industrial activities expand, the demand for reliable and cost-efficient wastewater treatment solutions has intensified. Among various biological treatment methods, trickling filter technologies have emerged as a robust and adaptable approach particularly suited for decentralized and medium-scale applications. This chapter explores the design, cost, and development of trickling filter technologies in wastewater treatment. The chapter covers the fundamentals of trickle filter design, including essential aspects such as media selection and calculation of the required dimensions and spaces. Cost estimates of capital and operating costs of trickle filter technologies are given, and these are compared to other technologies of wastewater treatment. Other advances in this field are also discussed, for example, the application of modern technologies and innovations in technological processing to enhance efficiency and cut expenses. The chapter also consists of real-life examples and case studies for the purpose of explaining and leading the readers to learn and implement the trickling filter technologies in the field of wastewater treatment.