Small towns in low- and middle-income countries are growing rapidly and struggling to meet the increased demands of wastewater collection and treatment. To avert public health crises and continued environmental degradation, small towns are actively seeking safely managed sanitation solutions, appropriate for their scale, institutional capacity, financial resources, and overarching needs. This document is designed to provide a guide of small-town wastewater treatment processes in order to assist engineers, managers and other stakeholders responsible for wastewater service provision in identifying and selecting appropriate wastewater treatment processes for small towns. This guide is part of a World Bank suite of tools and other material to support World Bank teams and their government counterparts in the planning, design, and implementation of sanitation projects in urbanizing areas. Addressing the specific context of small towns, the format of this guide begins with an introduction of key concepts for a decision maker to understand and then applies a suggested five-step approach to exploring appropriate wastewater treatment technologies, culminating with case studies from three regions applying this approach. It delves into the unique considerations for small-town wastewater treatment and the exploration of corresponding technologies. Before demonstrating the application of the approach, the guide also navigates: (a) factors external to the technologies that define the characteristics and environment of a given small town and that will affect technology choice
and (b) technology-specific information that will ultimately influence decision making. Before embarking on the formal planning and design process, the user is highly encouraged to become familiar with the guide methodology in its entirety while drawing on the principles of the Citywide Inclusive Sanitation approach.