This manual is intended as a source document for individuals responsible for improving the performance of an existing, non-complying wastewater treatment facility. Described are: 1) methods to evaluate an existing facility's capability to achieve improved performance, 2) a process for systematically improving its performance, and 3) details on how to modify the facility to achieve the required levels of performance. The manual emphasizes meeting National Pollutant Discharge Elimination System (NPDES) permit requirements for secondary treatment facilities (30 mg/L BODs and TSS). Though the manual is not intended to describe cost saving options or to present alternatives for designing new facilities for expansion purposes (i.e., to provide increased hydraulic and/or BOD loading capacity), in some cases the approach and modifications described may result in cost savings and/or increased capacity.
The need for better treatment performance from existing facilities is widespread. Usually the most cost effective approach for owners to achieve compliance is to optimize existing facilities either in terms of capital or operational improvements. Recent events have provided impetus to this approach by increasing incentives for improving existing plant performance.