Date of Award

Fall 2020

Project Type

Thesis

Program or Major

Civil Engineering

Degree Name

Master of Science

First Advisor

James P Malley

Second Advisor

Nancy Kinner

Third Advisor

Abraham J Martijn

Abstract

Globally drinking water sources are under pressure. In many places, there is unintended closure of the water cycle. This means that the wastewater treatment plant effluent with all its pollutants ends up in the source of drinking water treatment plants that are not designed to treat this type of water. Impacts on water sources from factors such as climate change and high population density make unintended reuse, indirect reuse, and potable reuse more accepted and explored. Known reuse schemes use high end treatment technologies such as ceramic microfiltration. While ceramic microfiltration is a beneficial treatment option, its effectiveness can be limited due to membrane fouling causing increases in energy consumption, increases in operating costs, and a loss in permeability. Coagulation and ozonation are pretreatment options that can help mitigate membrane fouling.

Using a secondary wastewater effluent reuse pilot at RWZI Wervershoof in the Netherlands, this research project evaluated the abilities of coagulation and ozonation pretreatment to improve ceramic microfiltration performance in comparison with control runs without pretreatment. This evaluation was based on performance parameters such as critical flux and sustainable flux based on a transmembrane pressure (TMP) criterion. Critical flux was defined as the flux level at which the detection of membrane fouling initially appeared, and sustainable flux was defined as the flux level directly (25 Lmh) below the critical flux. Water quality samples were analyzed on NOM characteristics to explain ceramic microfiltration fouling

Twenty-four-hour constant flux tests were performed to determine the critical and sustainable fluxes for the three treatment options. For the coagulation pretreatment tests, two dosages of ferric chloride, 20 and 6 mg/L as Fe3+, were tested to determine the more appropriate dosage to restrict ceramic microfiltration fouling. Based on the constant flux test results, a ferric chloride dosage of 6 mg/L as Fe3+ was chosen. For the ozonation pretreatment tests, a bench-scale ozone uptake test was conducted to determine the ozone dosage for the constant flux tests. Based on this test, the selected ozone dosage was 8 mg/L as O3.

Without pretreatment, the critical flux was 145 Lmh. Coagulation and ozonation pretreatment increased the critical flux to 195 and 270 Lmh, respectively. During coagulation pretreatment, the critical flux increase was based on NOM removal. During ozonation pretreatment, the critical flux increase was based on changing the NOM characteristics.

The results illustrated that compared to no pretreatment, coagulation pretreatment improved and ozonation pretreatment strongly improved ceramic microfiltration performance. Overall, coagulation or ozonation pretreatment enables a more economical application of ceramic microfiltration for water reuse.

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