Scale-up of Moringa Oleifera coated sand filters to remove pathogens from wastewater
Open Access
- Author:
- Dickey, Roman
- Area of Honors:
- Chemical Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Stephanie Butler Velegol, Thesis Supervisor
Wayne Roger Curtis, Thesis Honors Advisor - Keywords:
- Moringa Oleifa
E.coli removal
water purifcation
f-sand
biochar
clean bed filtration model - Abstract:
- The World Health Organization (WHO) has reported that waterborne infectious diseases cause more than 2.2 million deaths in 2016.1 It is estimated by 2025, half of the world’s population will be living in water-stressed areas.2 In 2015, 884 million people worldwide lacked access to a basic drinking water service, while 2.3 billion people lacked even basic sanitation facilities such as toilets or latrines.3 Point of use household technologies are able to significantly reduce diarrheal diseases using boiling, chlorination, bio-sand filters and ceramic filters.4 This study explores the use of functionalized sand filter (f-sand) created with the seeds of a Moringa oleifera (MO) tree to offer a potential adsorbent for the removal of E. coli. MO grows widely in many equatorial regions of the world where people are threatened by diarrheal diseases caused by drinking water contamination. The seeds of MO contain cationic proteins that have antimicrobial, antifungal, and coagulant properties. The use of clean bed filtration model led to the scaled-up design of a lab-scale f-sand column. E. coli strain TG1 containing plasmids that express red fluorescent protein (pCA24N-rfp-lasR) were used as model pathogens at an influent concentration of 108 colony-forming units (CFU)/mL suspended in 10-fold diluted phosphate buffered saline (PBS) buffer (0.016 M). Initial scale-up results showed no enhanced removal using the f-sand columns due to an increase in collector size. The use of binary mixtures of collector sizes (≤106 μm and 212-300 μm glass beads) showed the need for a critical percentage of >55% small collector sizes for f-sand columns to see enhancement from that of a bare sand column. Experiments were performed using different ranges of collector sizes and illustrated that the critical collector diameter in order to create an effective f-sand column is ~ 175 μm given a flow rate of 1.6mL/min and a column with a 1.5 cm diameter and 10cm length. An additional scale-up was made using glass powder (140-210 μm) with a 5 cm diameter and 10 cm length 2 with an average flow rate of 12 mL/min resulting in a >6.5 LRE for 80 PV with a sharp breakthrough at PV 85. We also report on the use of biochar pre-filter to remove organic matter from pond water to yield an effective log removal efficiency (LRE) for f-sand columns. Organic matter can block potential bacterial removal sites in f-sand columns. Biochar was used as an inexpensive, readily available and environmentally friendly adsorbent that has been used to treat wastewater effluents. The biochar used was generated from cotton gin waste feedstock with pyrolysis conditions of 700 °C for 2 hours. The biochar f-sand filters used in series produced a >8 LRE