Date of Award

Winter 2016

Project Type

Thesis

Program or Major

Civil Engineering

Degree Name

Master of Science

First Advisor

M. Robin Collins

Second Advisor

Thomas P Ballestero

Third Advisor

James P Malley

Abstract

Gravel roughing filtration (GRF) is often used to pretreat marginal source waters prior to the main filtration process. GRF is a proven way to consistently improve water quality and reduce the effects of low water quality spikes such as during a precipitation event. This research is aimed at improving GRF performance through the application of various forms of algae. Research was broken down into four components: culturing and transferring algae, growing filamentous algae on the filter bed of a downflow GRF, applying an algae coating to the surface of gravel media, and testing a field-scale horizontal roughing filter (HRF) to evaluate filter performance and operational characteristics.

Culturing algae in a laboratory setting proved to be very difficult and inconsistent during the course of study. Filamentous algae cultures grew most effectively, while relatively slowly, in quiescent water while suspended algae grew rapidly in highly turbulent and aerated water. Culturing filamentous algae in situ on a GRF was also problematic on all but one attempt resulting in limited filter challenge data. However, an experiment using an oscillating platform shaker showed large removals of suspended E. coli supporting the theory that filamentous algae can entrap particulate matter. Gravel media coated with algae performed better than clean media when removing turbidity from water, but did not significantly impact NOM levels. Enhancing trends were seen with Scenedesmus sp. coated media and should be further investigated. The HRF were allowed to ripen for two months prior to a turbidity spike challenge. The filters removed approximately 93% of the turbidity from the water, supporting the notion that a well ripened roughing filter can significantly reduce the effects of water quality spikes on a primary treatment filter. More research is needed to test of the feasibility and practicality of using algae to enhance gravel roughing filtration.

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