Comparative study of integrated constructed wetland systems employing oyster shells and alum sludge as filter media for phosphorus removal | |
| Author | Woo Ha, Park |
| Call Number | AIT Diss. no.EV-08-7 |
| Subject(s) | Phosphorus--Toxicology Constructed wetlands Oyster shell |
| Note | A dissertation submitted in partial fulfillment of requirements for the degree of Doctor of Engineering in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. EV-08-7 |
| Abstract | This research aimed to evaluate the technical feasibility of employing some locally available oyster shells (OS) and alum sludge (AS) as media of constructed wetland beds for P adsorption and removal from wastewaters. All investigations of P in this research were measured as PO₄-P. Batch and column tests were conducted with different sizes of OS and AS to observe the P adsorption characteristics and breakthrough, while P adsorption rates were determined from jar tests. From the batch test, the ability to adsorb the amount of added P was different considerably between OS and AS media and sizes. At the same size, the P adsorption capacities of OS were higher than those of alum sludge. The P adsorption capacities of AS with 0.3-0.6 mm and >0.6mm sizes were similar, but those of 0.3-0.6 mm OS was higher than >0.6 mm OS. Jar test results revealed the first-order P removal rates (k) to be 11.4, 4.5, 1.7 and 1.0 d⁻¹ for the 0.3-0.6 mm AS, >0.6 mm AS, 0.3-0.6 mm OS, and >0.6 mm OS, respectively. From the column tests, the adsorption capacities were found to be more than 26 and 24.5 g/kg for the OS media sizes of 0.3-0.6 and >0.6mm, respectively; and 12 g/kg for the AS media. Although AS was able to adsorb P faster than the oyster shells, due to its low adsorption capacity, the periods of P breakthrough in the effluent of the AS columns were shorter than those of the oyster shell columns. Three integrated constructed wetland (ICONWEP) systems were operated to investigate technical feasibility of applying a constructed wetland with post- or pre- filter unit for P removal from domestic wastewaters. Based on 240 days of operation under the overall hydraulic retention time of 3.5 days, the ICONWEP I consisting of a constructed wetland and post-filter unit (OS media), in series, was found to be effective in removing BOD₅ (92.7 %), N (92.1 %), P (99.4 %) and TSS (91.6 %) compounds. The constructed wetland unit was responsible for most of the treatment performance, while the post-filter unit served as a polishing unit, especially in the removal of the remaining N, P and TSS. The ICONWEP II system consisting of a pre-filter (AS media) and constructed wetland unit, in series, had poor plant growth because most P was removed by the pre-filter unit. However, the ICONWEP II was effective in removing BOD₅, N, P and TSS compounds which were found to be 89.5, 68.8, 99.4 and 89.9 %, respectively, based on the 240 days of operation from November 2006 to August 2007. The ICONWEP III system consisting of a CW and post-filter unit (AS media), in series, which was modified by taking the pre-filter unit of ICONWEP II as the post-filter unit at the end of experimental runs for ICONWEP II, was also effective in removing BOD₅, TN, PO₄-P and TSS in which the removal efficiencies were found to be 88.5, 53.4, 99.4 and 78.4 %, respectively, during 120 days operation from September to December 2007 |
| Year | 2008 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. EV-08-7 |
| Type | Dissertation |
| 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 (EV) |
| Chairperson(s) | Chongrak Polprasert ;Visvanathan, C. (Co-Chairperson) |
| Examination Committee(s) | Thammarat Koottatep ;Clemente, R.S. |
| Scholarship Donor(s) | External (K-WATER) |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2008 |