Improving the hydraulics of drinking water contact tanks using random packing material

Abstract

This study investigated the use of industrial packing material for increasing the hydraulic efficiency of small‐scale, chlorine contact tanks used in drinking water treatment. The packing material used in this study was spherical, with porosities between 0.9 and 0.95 and a density less than that of water. A total of 67 tracer studies, conducted on laboratory‐scale chlorine contact tank systems, examined three sizes of packing material, two tank sizes, and two flow rates. Sodium chloride solution was injected as a continuous tracer at the inlet and was monitored in the tank outflow through electrical conductivity. Several studies were validated with the use and direct measurement of a lithium ion tracer. Hydraulic efficiency was measured by determining the baffling factor as outlined by the US Environmental Protection Agency. Results suggest that the use of packing material in small drinking water contact tanks can significantly increase the baffling factor, improving the disinfection efficiency obtained from existing tanks.

Assessing flow segregation and mixing by modeling residual disinfectant conversion

“…Although segregated flows are expected to achieve more disinfection than mixed flows, it is not readily apparent how traditional baffling or inlet/outlet modifications could encourage flow segregation. Random packing has recently been proposed as a method to reduce dispersion in water treatment reactors (Barnett, Kattnig, Venayagamoorthy, & Whittaker, ; Kattnig & Venayagamoorthy, ). A similar concept could be applied using structured, tubular packing.…”

Random packing material in disinfection contactors: Effects on final drinking water quality

“…spherical RPM (polypropylene NSF/ANSI61-certified, with 90% void fraction [Raschig USA, Inc., Arlington, TX]). At 5 gpm, this contact system has a BF of 0.94 (Barnett et al, 2014), providing 10 min of retention (or contact) time. According to USEPA standards, 10 min is sufficient for log-4 removal of bacteria and log-3 removal of viruses (USEPA, 2003).…”

“…RPMs are constructed from different materials, some of which are NSF/ANSI 61 certified, and therefore, safe for use in drinking water systems (NSF, 2016). Recently a lab-scale study was conducted demonstrating that filling a cylindrical tank with RPM created near-plug flow conditions (BF 0.9) (Barnett, Kattnig, Venayagamoorthy, & Whittaker, 2014), which are ideal for chemical disinfection purposes in terms of microbe inactivation as well as reduction of DBPs (Wilson & Venayagamoorthy, 2010).…”

A Hybrid Approach for Increasing Baffling Factors in Contact Tanks

“…Packing material is traditionally used in vapor separation towers to facilitate the stripping of volatile organic compounds from contaminated liquids, but it has also been applied in wastewater treatment applications, such as trickling filters, where it is used to facilitate biofilm growth (Pilling & Holden 2009, USDOE 2001, Richards & Rienhart 1986, Kavanaugh & Trussell 1980). Its use in this study has been motivated by research conducted by Barnett et al (2014), which suggests spherical packing material has the potential for improving the hydraulic residence time of small drinking water systems. Spherical packing material with a 2‐in.…”

“…Spherical packing material with a 2‐in. diameter was the only material considered in this study in part because of its superior performance in the study conducted on small‐scale cylindrical contact tanks (Barnett et al 2014) and in the interest of simplicity (refer to Barnett et al 2014 for additional information regarding applied packing material). Other available shapes of random packing material include disks, cylinders, and saddles (Raschig Jaeger Technologies 2006).…”