Turbidity Removal from Kaolin Suspensions and Wastewater using Moringa oliefera

Open Access
Neal, Andrew Seth
Area of Honors:
Biological Engineering
Bachelor of Science
Document Type:
Thesis Supervisors:
  • Herschel Adams Elliott, Thesis Supervisor
  • Stephanie Butler Velegol, Thesis Supervisor
  • Ali Demirci, Honors Advisor
  • Moringa
  • oleifera
  • turbidity
  • reduction
  • removal
  • water treatment
  • developing world
  • kaolin
  • coagulation
  • micro scale jar test
Moringa oleifera (Moringa or MO) is a tropical tree containing seeds that possess a cationic protein (MOCP) that has both antimicrobial and coagulation properties potentially useful in water treatment in developing countries. Since pathogen removal is correlated with turbidity removal in water supplies, this research investigated turbidity removal with time from kaolin suspensions and primary municipal wastewater effluent using extracted MOCP contained in the Moringa seeds. This research also focused on what effect seed maturity had on turbidity removal with time. In an effort to save seeds, micro-scale jar tests were used to evaluate the coagulation effectiveness of MOCP as exhibited by turbidity removal in two kaolin suspensions (initial turbidities of 100 and 500 NTU) and one 100 NTU primary effluent wastewater. For the 100 NTU kaolin suspensions, the presence of MOCP moderately increased turbidity removal compared to the control samples after 1 hour of sedimentation(MOCP absent). This finding was consistent with previous studies documenting the less effective coagulation ability of MOCP for low turbidity waters. However, for 500 NTU kaolin, turbidity removal after 1 hour was 86.4% in the presence of MOCP compared to 19.1for the control samples. Assuming turbidity was proportional to the concentration of particles in solution, the data was analyzed for conformance to perikinetic flocculation which assumes that the rate of change of the concentration of particles with time is a second-order process. Plots of the integrated form of a second-order process (1/turbidity versus time) were highly linear (R2 = 0.97 and 0.99 for 100 NTU and 500 NTU kaolin, respectively). Perikinetic flocculation dictates that the rate of turbidity removal depends on the initial particle concentration and explains the observed greater rate of turbidity removal for the 500 NTU versus the 100 NTU kaolin suspensions. The same micro-scale jar tests were performed using 100 NTU primary effluent wastewater. After one hour, the turbidity removal was 60.6% in the presence of MOCP and 20.1% in the control samples. Compared to the 100 NTU kaolin suspension, the wastewater initially had greater turbidity removal, but after 24 hours regrowth in the wastewater began to increase the turbidity. After 24 hours the turbidity removal in 100 NTU kaolin was 98.2% whereas the turbidity removal in wastewater was 73.3%. Regrowth of the wastewater over time competed with turbidity removal, and perikinetic flocculation theory alone was not sufficient in describing the wastewater results. Micro-scale jar tests were also conducted using less mature medium-sized MO seeds. Contrary to current Moringa literature, a major finding was that the less mature, partially green seeds still were effective at reducing turbidity. Further research is needed to clarify the relationship between seed maturity and effectiveness as a natural coagulant for water treatment. Using a newly developed percent turbidity removal calculation, the turbidity removal after 24 hours for the medium and large seeds was 79.9% and 92.7%, respectively. The research demonstrates that extracts of MO can serve as natural coagulants for treatment of turbid waters, although the effectiveness depends on many factors including the initial turbidity of the water, sedimentation time, and maturity of the MO seeds. Further research is needed to define the conditions under which MO should be implemented as a low cost, point-of-use water treatment method in communities lacking access to clean drinking water.