Clogging in vertical flow constructed wetland treating under intermittent feeding patterns | |
| Author | Kim, Won Kwon |
| Call Number | AIT Thesis no.EV-12-28 |
| Subject(s) | Sewage--Purification--Biological treatment Constructed wetlands |
| 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 |
| Series Statement | Thesis ; no. EV-12-28 |
| Abstract | Vertical flow constructed wetland systems (VFCWs) has become a preferred method for wastewater treatment for rural areas and other decentralized wastewater applications. However, these systems usually have displayed clogging problem by increasing hydraulic conductivity based on the constant supply of organic and inorganic pollutant to this system. The attributed factor to clogging was phased depending on the composition of wastewater and operating periods. The compound of wastewater this study applied was molasses and soil particles to lab-scale VFCWs units which could be used as factor causing clogging within bed media, and two different operating conditions (continuous flow and intermittent flow) were chosen in this case whereby clogging occurrence and its occasion could have been identified by statistical analysis. To demonstrate this experiment, five lab-scale VFCWs of dimensions 1.3 m in height and 0.25 m in diameter were operated under intermittent feeding mode. Intermittent feeding mode was set as two group each of which were set as 5days on/ 2days off and 3days on/ 4days off respectively. The HLRs in order to simulate clogging phenomena to the lab-scale VFCWs units were set as 15 m³/m²d as maximized. The media arrangement was set as an order of sand, small and large gravel layer that each of height was 0.1, 0.15 and 0.35m, respectively. The concentration of synthesized wastewater was constant at 360 mg/L in terms of COD and 260mg/L in terms of SS and additionally 19.5 mg/L NH4-N as nutrient was also added in control unit and 39 mg/L in COD and SS units. To analyze the treatment efficiencies and its variation to clogging occurrence, chemical oxygen demand (COD) and suspended solid (SS) and dissolved oxygen (DO) from influent and effluent sample were measured. For the mechanistic measurement section of clogging occurrence, hydraulic conductivity and effective porosity and reduction of porosity were also measured to compare with treatment efficiency variation. Clogging was occurred regardless of choosing IF or CF system however, its extent of occurrence and occasion was different from each other. Clogging occurrence in both of systems was characterized into two different phase pre and post-clogging stage. In the pre clogging stage, clogging impact triggered by organic pollutant was prevailed against inorganic pollutant along the operating period whereas in post-clogging inorganic pollutant was vice versa. To the clogging occasion, reduction of porosity in IF 3days on/ 4days off showed a less dwindle pattern than IF 5days on/2 days off system. Bivariate analysis of all data amongst hydraulic conductivity and effective porosity and treatment efficiency variation was measured to indicate that clogging in CF system was more prominent than IF system regardless of any operating bias factors and solid accumulation was conclude to be more attributed to clogging in both of system. As a conclusion, this study suggested that clogging problem could be alleviated by having an interval period as to 3 days on/ 4days off in VFCWs. |
| Year | 2012 |
| 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) | Visvanathan, C.;Preeda Pakpian; |
| Scholarship Donor(s) | Asian Institute of Technology Fellowship; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2012 |