Effects of CeO2 and ZnO nanoparticles on anaerobic digestion and toxicity of digested sludge | |
| Author | Nguyen Minh Duc |
| Call Number | AIT Thesis no.EV-13-18 |
| Subject(s) | Nanoparticles Sewage--Purification--Anaerobic treatment |
| 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-13-18 |
| Abstract | With the rapid growth of nanotechnology in past decade, nanoparticles, such as CeO₂ and ZnO, are now widely commercialized in many products. The industrialization and commercialization of NPs have made the release of these compounds to the environment and wastewater treatment plants become inevitable. However, many researchers have found that conventional WWTPs can effectively remove NPs from the wastewater. It means that the higher the removal efficiency of NPs, the higher NPs exist in the waste sludge. Therefore, NPs can accumulate to a very high concentration in the waste sludge. However, information about impact and toxicity of NPs on sludge treatment stream is still very restricted. As a result, this research aimed to study about effects of CeO₂ and ZnO NPs on sludge anaerobic digestion process, sludge dewatering process, and toxicity of sludge to bacteria and plants. The result showed that CeO₂ and ZnO NPs could cause inhibition to the biogas production of anaerobic digestion system. The exposure concentration of ZnO at 1,000 mg/L caused greatest inhibition to the biogas volume (65.3%) and the methane composition (40.7%), as compared with controlled sample. In addition, at tolerable exposure concentration of ZnO, the system could overcome the inhibition effect after 14 days of incubation. In the other hand, CeO₂ at low concentration of 10 mg/L could increase the generated biogas volume by 11%. The positive effect of CeO₂ at low concentration was also observed on bacterial toxicity test. The ZnO NPs was more toxic to bacteria than CeO₂ NPs at same exposure concentration. However, the bacterial toxicity of both nanoparticles were reduced when they were applied on the sludge. Moreover, after went through anaerobic digestion process, the bacterial toxicity was again lessen. Additionally, required time to dewater the digested sludge was increased proportionally with the exposure concentration of nanoparticles. Finally, the accumulation of CeO₂ and ZnO NPs on sludge made the digested sludge become unsuitable to be used as biosolid, since the contaminated digested sludge caused great inhibition on root growth and seed germination of plants. In conclusion, CeO₂ and ZnO nanoparticles greatly impacted the anaerobic digestion system by inhibiting the biogas production process. Moreover, they made digested sludge become difficult to dewater. Besides, the toxicity of nanoparticles still remained even after anaerobic digestion process that could inhibit the bacterial viability and seed germination and root growth of plants. |
| Year | 2013 |
| 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) | Visvanathan, C.; |
| Examination Committee(s) | Shipin, Oleg V.;Hornyak, Gabor; |
| Scholarship Donor(s) | Deutscher Akademischer Austausch Dienst (DAAD), Germany;Asian Institute of Technology Fellowship; |
| Degree | Thesis (M.Sc.) - Asian Institute of Technology, 2013 |