Developing modified multi-soil layer-based constructed wetlands for the treatment of septic tank effluent | |
| Author | Le Gia Ky |
| Call Number | AIT Thesis no.EV-21-27 |
| Subject(s) | Septic tanks Wetlands--Design and construction Sewage--Purification |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Abstract | While on-site treatments for black water was unable to have effluent quality that meet the standard discharge, constructed wetlands was considered as secondary treatment due to its advantages on operation cost and removal efficiency. Combining the multi-soil-layer system with constructed wetland would improve its performance in various aspects such as land area requirement, hydraulic retention time (HRT), etc. Moreover, another important advantage of multi-soil-layer system based constructed wetland (MSL-CW) is its flexibility. This research focused on developing two customized MSL-CWs to improve model’s performance on some specific parameter. In the first MSL-CW (reactor 2), iron slag was added in soil-mixed block (SMB) to have composition of lateritic soil (70%), sawdust (10 %), iron slag (10%) and charcoal (10 %). The main purpose of adding iron slag was improving Phosphorus removal. In second MSL-CW (reactor 3), SMB composition was Lateritic soil (70%), sawdust (15 %) and charcoal (15 %) but a 7cm soil layer was added on the top of reactor. The addition soil layer could enhance the microbial community on the surface of MSL-CW and plant growth potentially. The models were operated in 3 different retention time (36h, 24h and 12h). The results showed were high TSS removal rates of three reactors from the start (>99%) but still reactor 3 had slightly better efficient removal. Reactor 3 effluent also had the lowest concentration in both TCOD and SCOD at any HRT. Similar pattern was showed with BOD5 treatment, reactor 3 consistently had highest removal efficiencies. For TKN and NH3-N, Zeolite layer and its ion-exchange mechanism to remove ammonium ion made reactor 2 had the lowest concentration of all reactors regardless HRT. Moreover, a notable improvement in phosphorus removal in reactor 2 indicated that adding iron in SMB can promote phosphorus assimilation. One-way ANOVA results also confirmed the advantages of these modified MSL-CWs as the results showed the significant differences in all reaction rates at any HRT. Kinetic model validation test demonstrated that both TCOD and TKN removal follow first order kinetic in all three reactors while TP removal in reactor 2 and reactor 3 did not approach first order kinetic. |
| Year | 2021 |
| Type | Thesis |
| School | School of Environment, Resources, and Development |
| 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 Kootattep |
| Examination Committee(s) | Ekbordin Winijkul;Tatchai Pussayanavin |
| Scholarship Donor(s) | AITCV Silver Anniversary Scholarships;AIT Fellowship |
| Degree | Thesis (M. Eng.) - Asian Institute of Technology, 2021 |