Status of Declining Rate Filtration Design

Abstract

Declining rate filtration is one of several flow control alternatives available for gravity filtration plants with four or more filters. Experimental and theoretical studies of declining rate filtration have provided the foundation for rational design procedures. This paper presents design procedures for estimating the filter system head needed for a declining rate filtration plant, and to predict the water level variations that will occur during operation. The paper also discusses the choice between inlet versus outlet rate limitation, the choice of type of rate limitation device, and the impact of operation of a declining rate filtration plant below full design load.