M.Sc.Eng. thesis about urine microfiltration / ultrafiltration

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M.Sc.Eng. thesis about urine microfiltration / ultrafiltration (to download here)

Title of the thesis: Microfiltration / ultrafiltration of stored urine and urine diluted with water

Date of publication: 2016

Author: Joyce Ouma

Affiliation: Pollution Research Group, University of KwaZulu-Natal

Supervisors: Dr. Santiago Septien Stringel; Dr. Jon Pocock; Pr. Chris Buckley

Abstract: Sanitation is a major challenge for developing countries. According to World Health Organization (WHO) and United Nations International Emergency Children’s Fund (UNICEF), approximately 2.5 billion people in developing countries lack access to proper sanitation facilities (WHO and UNICEF (2013). This has led to the spread of water borne diseases and reduction of the quality of life of the affected people. The “Reinvent the Toilet Challenge” (RTTC) which is an initiative of the Bill & Melinda Gates Foundation aims is to setup novel sanitation systems and find a hygienic and sustainable disposal route for human waste. Membrane technology such as microfiltration/ultrafiltration, nanofiltration, reverse osmosis and forward osmosis can be used for this purpose.
The main objective of this study was to explore the use of microfiltration/Ultrafiltration membranes to determine the parameters that affect the performance of the membranes when filtering two types of urine: stored urine representing the stored feedstock which could be obtained from Urine Diversion Dry Toilets (UDDT); diluted stored urine representing the feedstock which could be obtained from urinals. This was based on the study of flux, permeability, fouling potential and rejection. This study was limited to stored urine which is more stable than fresh urine.
A stirred Amicon® cell in dead-end filtration mode was used in a range of constant transmembrane pressures (TMP) between 10 and 60 kPa. All the membranes used in this study were similar with the same material and molecular weight cut off (MWCO) of 500 kilo Daltons (kDa). Permeability of the membrane before and after filtration, and after cleaning was determined by measuring flux against transmembrane pressure using deionised water. Fouling potential was determined using the modified fouling index (MFI). Physico-chemical characteristics, including particle size distribution analysis, of diluted and undiluted urine before and after filtration were also determined for the purpose of determining membrane rejection. Three cases were studied during these experiments. Case 1 and case 2 involved filtration of undiluted urine while case 3 using diluted urine (at 1:5 ratio of urine to water). For case 1, the experiment was set to start from low to high transmembrane pressure while in the opposite direction for case 2. Case 3 pressure was operated in a similar manner as case 1.
The results indicated that diluted urine had flux significantly higher than undiluted urine with maximum values of 43 and 26 L.m-2.h-1 respectively. Water recovery after a filtration duration of one hour was approximately 40% and 20% for diluted urine and undiluted urine respectively. Permeability of the membranes was lowered significantly, after filtration up to 95%. After cleaning, approximately 80% of permeability was recovered for case 1 and case 3 while approximately 40% was recovered for case 2. Higher membrane resistance due to the cake and irreversible fouling were observed for case 2 (up to 50% higher) compared to case 1 and case 3. It was speculated that particulate matter (larger than 0.1 μm) and colloidal organic matter were the important foulants. According to the modified fouling index, undiluted urine had a higher fouling potential (volume flowrate of 0.089 L.h-1) compared to diluted urine (volume flowrate 0.16 L.h-1). As expected, the specific cake resistance was lower for undiluted urine compared to diluted urine The permeate obtained after urine microfiltration/ultrafiltration was much less loaded in suspended solids compared to the feedstock, but the concentration of the ionic species remained similar.

Keywords: urine; filtration; membrane; flux; fouling; rejection; reuse.

Dr. Santiago Septien Stringel
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