| Author | Seni Karnchanawong |
| Call Number | AIT Diss. no. EV-89-03 |
| Subject(s) | Sewage--Purification--Nitrogen removal
|
| Note | A dissertation submitted in partial fulfillment of the requirements for
the degree of Doctor of Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | Experiments on attached-growth circulating reactor (AGCR) were
conducted to investigate its efficiencies on organic carbon and nitrogen
removal (through denitrification). A laboratory-scale AGCR, made of
serpentine channel with the dimensions of 0.05 x 0.20 x 180.00 m (width
x depth x length), was fed with synthetic wastewater at the chemical
oxygen demand (COD) and total nitrogen (TN) loading rates of 3.6-10.2 and
0.30-0.91 g/(m2 .d), respectively. The reactor effluent was recycled back
to the influent feeding point and the dissolved oxygen (DO) concentrations
along the channel length were controlled by means of air diffusion. It
was found that the COD loading rate of 5 g/ (m2.d) corresponding to the
TN loading rate of 0. 54 g/ (m2. d) gave the optimum COD and TN removal rates
of 4.8 and 0.43 g/(m2 .d), respectively. The overall AGCR performance was
limited by the nitrification efficiency at the high TN loading rates. The
biofilm accumulation and thickness were found to be distinctly higher in
the first-half portion than the second-half portion of the channel length.
A pilot-scale AGCR with the dimensions of 0.30 x 1.00 x 62.25 m
(width x depth x length) was operated at the COD and TN loading rates of
3.9-6.1 and 0.59-0.93 g/(m2 .d), respectively, using campus sewage as an
influent feed. For removal of settleable solids, the AGCR effluent was
partially directed to a square sedimentation tank with the dimensions of
0. 50 x 0. 50 x 0. 70 m (width x length x depth). It was found that the
overall TN removal efficiency was limited by denitrification because
there was no DO sag-curve profile occurring during the pilot-scale
experiments. The COD loading rate of 4.6 g/(m2 .d) corresponding to the
TN loading rate of 0. 69 g/(m2•d) gave the optimum COD and TN removal rates
(at the effluent of the sedimentation tank) of 3.8 and 0.45 g/(m2.d),
respectively. The biofilm accumulation and thickness did not
significantly vary along the channel length.
Batch experiments were conducted under suspended conditions to
determine the maximum substrate utilization rates (k) of the biofilms.
It was found that the k values varied along the AGCR laboratory-scale
channel length according to the DO concentration profile and the
predominant biochemical reactions. The similar trends of k values
variation were observed in the pilot-scale unit, but the extent of
variation was not so large as that of the laboratory-scale unit.
A mathematical model was proposed to include and simulate all three
biofilm reactions (carbon oxidation, nitrification, denitrification)
along the channel length. It was found that for the laboratory-scale AGCR
unit operated at low COD and TN loading rates, DO concentration was the
limiting factor for carbon oxidation and nitrification in the first-half
portion, and biofilm thickness was the limiting factor for the second-half
portion of the channel length (where denitrification did not exist). For
the pilot-scale and laboratory-scale AGCR (operating at high loading
rates), denitrification occurred throughout the channel length and DO
concentration was the limiting factor for carbon oxidation and
nitrification activites. |
| Year | 1989 |
| 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 and Management (EV) |
| Chairperson(s) | Chongrak Polprasert; |
| Examination Committee(s) | Vigneswaran, S.;Verink, Johan;Huynh, Ngoc Phien;Harremoes, Poul; |
| Scholarship Donor(s) | Royal Norwegian Government; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 1989 |