Selecting the wrong screw press capacity is one of the most costly mistakes in sludge dewatering design — yet most sizing errors are entirely preventable. This guide presents a 4-step methodology: estimating your daily DS load, converting it to required press throughput, applying the right safety factor for your application, and verifying hydraulic loading. Includes a full worked example, press capacity reference tables, and a guide to the 7 most common sizing mistakes.