Extreme value analysis of wastewater treatment plant flows

摘要

The implenetation of the Clean Water Act has resulted in the provision of enhanced astewater treatment facilities throughout this country. The initial effort focused upon providing a minimum of secondary treatment (or higher-order treatent if needed) to meet surface water quality standards under dry weather flow conditions. Since 1987, increased emphasis has been placed by both federal and state regulatory agencies upon meeting effluent limits from these treatment facilities under wet weatherflow conditions. In communities served by combined sanitary and stomwater sewers, the treatment plant may experience very significant variations in flows to be treated at the facility. This paper will present both a Gumbel Type I extreme value distribution and a Gumbel Type II extreme value distribution to examine the problability of high flow exceedance at a treatment facility. This type of analysis provides a preliminary framework for consideration of the trade-off between fully cpaturing extreme value flows vs.occasionally by-passig extreme value flows with less than full treatment.