This report provides general information on the design and selection of wastewater systems with capacities for populations up to 2500. This information is intended for use by individuals with limited experience in wastewater treatment and disposal as a source of available alternatives in small systems, as well as an outline of the steps and procedures to undertake when selecting a particular wastewater management scheme for a small community. Material covered includes: measurement and estimation of wastewater flows; physical, chemical and biological characteristics of domestic wastewater; on-site wastewater treatment and disposal processes; central wastewater collection and treatment systems; operating problems associated with small treatment systems; disposal of liquid effluents and waste sludges; and procedures employed in the selection and approval of wastewater systems. A case history is provided to illustrate the selection procedures discussed within the text.

Step-by-step procedures for planning, design, construction and operation: * Health and environment * Process improvements * Stormwater and combined sewer control and treatment * Effluent disposal and reuse * Biosolids disposal and reuse * On-site treatment and disposal of small flows * Wastewater treatment plants should be designed so that the effluent standards and reuse objectives, and biosolids regulations can be met with reasonable ease and cost. The design should incorporate flexibility for dealing with seasonal changes, as well as long-term changes in wastewater quality and future regulations. Good planning and design, therefore, must be based on five major steps: characterization of the raw wastewater quality and effluent, pre-design studies to develop alternative processes and selection of final process train, detailed design of the selected alternative, contraction, and operation and maintenance of the completed facility. Engineers, scientists, and financial analysts must utilize principles from a wide range of disciplines: engineering, chemistry, microbiology, geology, architecture, and economics to carry out the responsibilities of designing a wastewater treatment plant. The objective of this book is to present the technical and nontechnical issues that are most commonly addressed in the planning and design reports for wastewater treatment facilities prepared by practicing engineers. Topics discussed include facility planning, process description, process selection logic, mass balance calculations, design calculations, and concepts for equipment sizing. Theory, design, operation and maintenance, trouble shooting, equipment selection and specifications are integrated for each treatment process. Thus delineation of such information for use by students and practicing engineers is the main purpose of this book.

"This manual contains overview information on treatment technologies, installation practices, and past performance."--Introduction.

This manual is intended to provide guidance and criteria for the design and selection of small-scale wastewater treatment facilities. It provides both the information necessary to select, size, and design such wastewater treatment unit processes, and guidance to generally available and accepted references for such information. For the purpose of this manual, small-scale wastewater treatment systems are those with average daily design flows less than 379 000 liters per day (L/d) or 100,000 gallons per day (gal/d), including septic tanks for flows less than 18 900 L/d (5000 gal/d), small prefabricated or package plants for flows between 18 900 L/d (5000 gal/d) and 190 000 L/d (50,000 gal/d), and larger prefabricated treatment systems with capacities of no more than 379 000 L/d (100,000 gal/d).

This is a practical handbook providing a step-by-step approach to the techniques used for characterizing wastewater sources and investigating sites where collection, treatment and reuse/disposal technologies will be installed. It is intended to help enable local implementation of on-site and decentralized wastewater management system (DWMS)for wide scale use in development settings. How to Design Wastewater Systems for Local Conditions in Developing Countries helps local service providers and regulatory officials make informed decisions through the use of tools, checklists and case studies. It includes a link to a web based community of on-site and decentralized wastewater professionals, which contains related tools and case studies. This handbook serves as a reference for training classes, certification programs, and higher education programs in civil and sanitary engineering. There is an increasing interest on the part of local government officials and private sector service providers to implement wastewater treatment systems to solve sanitation problems. The model presented in this handbook promotes activities that first generate data related to source and site conditions that represent critical inputs, and then applies this information to the technology selection process. Matching the most appropriate technologies to the specific needs of the wastewater project is the key that leads to long term sustainability. How to Design Wastewater Systems for Local Conditions in Developing Countries is an invaluable resource for public sector decision makers and private sector service providers in developing countries. It is also a useful text for students at engineering colleges in developing countries interested in taking a class that teaches the methods of decentralized wastewater management system (DWMS) development.