Application of nano zero valent iron (NZVI) for pathogenic inactivation and odor control of septic tank effluent | |
| Author | Wichuda Tassanasuwan |
| Call Number | AIT Thesis no.EV-15-31 |
| Subject(s) | Septic tanks Disinfection Nanoparticles Nanotechnology Water--Purification--Disinfection |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. EV-15-31 |
| Abstract | Pathogens inactivation and odor control of the septic tank effluent are needed to be improved due to pathogens outbreaks could be a potential threat to user of the decentralized wastewater treatment systems with insufficient treatment. Historically, the application of nano zero valent iron (NZVI) focuses on the toxic substances removal in the groundwater treatment. The nano iron is found to be effective in removing variety of chemical and pathogenic contaminants from the water supplies. The application of NZVI coated on granular activated carbon (GAC) for post-treatment of the effluent from septic tank was studied in this research. The experiments were conducted with the synthesized NZVI/GAC column feeding with effluent samples in up-flow pattern at different HRT to determine the treatment performance for the E.coli, fecal coliform, total coliform and sulfide removals. The surface characteristic analysis of the synthesized NZVI/GAC using Inductively Coupled Plasma (ICP), Scanning Electron Microscope (SEM), Brunauer-Emmett-Teller (BET) surface area and X-ray diffraction (XRD) indicated formation of iron particles on the GAC. The characteristics of synthesized NZVI/GAC by SEM analysis found platy crystal growth texture or botryoidal texture and this showed in particles size of synthesized ≈ 100 nm. SEM-EDS instrument illustrated iron compound of NZVI on GAC surface. For iron elements quantity which analyzed by inductively coupled plasma (ICP),comparing between NZVI/GAC with and without binding agent were found to be about 0.9% and 0.7% wt, respectively. Thus, this study decided to use the binder for NZVI coated on GAC as ICP results described Fe0 completely dispersed and attached on GAC. BET analysis of initial GAC and synthesized NZVI/GAC were about 836.05 m²/g and 549.45 m²/g, respectively. In batch scale experiment, actual septic tank effluent was fed for comparing treatment performance with synthetic wastewater. The results of synthetic wastewater showed of pathogens were inactivated about 8 log reduction at 60 minutes. For actual septic tank effluent, more than 4-5 log reduction of E.coli and Total coliform were found at retention time 1 hour to 4 hours while granular activated carbon (as a control) cannot removed Total coliform and E.coli. For Sulfide removal efficiency in batch scale with actual septic tank effluent, NZVI/GAC can remove sulfide more than 99% within at 30 minutes. For continuous experiment conducted in columns, NZVI/GAC column of HRT 30 and 60 minutes can remove E.coli concentration only 1 log. Effluents of NZVI/GAC column operating at a HRT 120 minutes was about 7 log until 6 hours and decrease to 1 log at 45 hours, while operating at HRT 180 minutes with 10^7-10^8 CFU/ can removed concentration of E.coli about 2-7 log (figure 4.11) within 48 hours. To determine the performance of NZVI/GAC column with actual septic tank effluent in long term operation, breakthrough points of NZVI/GAC column operating at varied HRTs. HRT 3 hours was found inactivated E.coli after 1 day operation, while sulfide was found within 9 days. HRT of 6 hours, the concentration of total coliform and E.coli in the effluent of this system was found at 4 days operation. Breakthrough point of NZVI/GAC column operating at HRT 12 hours was found at about 7 days. In addition, bacteriophage analysis was achieved of HRT 12 hours which reduced bacteriophage accounting 110 PFU/mL within 3 days. According to regeneration method, the crystal growth of the regenerated NZVI/GAC by heating-air and adding reducing agent method presented dendritic crystal growth texture with the average iron particle diameter less than 100 nanometers that showed in SEM analysis. |
| Year | 2015 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Thammarat Koottatep; |
| Examination Committee(s) | Shipin, Oleg V.;Chongrak Polprasert; |
| Scholarship Donor(s) | Bill & Melinda Gates Foundation Sustainable Decentralized Wastewater Management in Developing Countries Project;Royal Thai Government Fellowship; |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 2015 |