5.0 Introduction

The fundamental objective of all wastewater treatment plant operations is to remove pollutants from wastewater and to consolidate them for further processing and/or disposal. Depending on the characteristics of the influent wastewater and the type of wastewater treatment to which it is subjected, the volume of the solids generated can vary significantly. Within the publicly owned treatment works (POTWs), several types of solids accumulate and must be collected periodically and transported, including screenings, grit, scum, and biosolids/sludge. Since the collection and transportation of these various types of solids from point to point within a POTW for treatment, storage, and disposal, as well as the transport of biosolids to beneficial-use sites, represents a significant cost to overall POTW operations, transportation options must be evaluated thoroughly prior to both construction of wastewater treatment plants and implementation of a biosolids beneficial-use system. Although all the information in this chapter pertains to the transport of biosolids/sludge within and outside the POTW, much of the information is also applicable to the transport of screenings, grit, and scum [37].

5.1 Transportation of Biosolids/Sludges

Transportation of biosolids/sludges is accomplished primarily by the use of pumps, conveyors, or hauling equipment. Within a wastewater treatment plant, liquid biosolids/sludges must be transported during various operations including (1) primary and secondary wastewater treatment, (2) thickening operations, (3) stabilization processing, and (4) dewatering operations.

The transport of liquid biosolids/sludges within the wastewater treatment plant normally is accomplished through the use of pipelines under pressurized (i.e., pumped) or gravity flow...