| Author | Udomphon Puetpaiboon |
| Call Number | AIT Diss no. EV-96-2 |
| Subject(s) | Sewage--Purification--Nitrogen removal
|
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of f Engineering |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. EV-96-2 |
| Abstract | This study evaluated nitrogen and organic carbon removal in Baffled Waste Stabilization
Ponds (BWSPs) comprised oflaboratory and pilot-scale BWSPs with different biofilm surface area
and number of baffles. The aim was to promote the waste stabilization pond practice for wastewater
treatment in tropical countries by reducing the land area requirement through the use of baffles which
increased the biofilm biomass concentrations in the pond water.
The experiments started with a tracer study to find out the hydraulic characteristics of each
pond. The dispersion number from the laboratory and pilot-scale experiments was in the range of
0.0887-0.1761 and 0.1428-0.1853, respectively. It was shown that the dispersion number decreased
with increasing flow length and number of baffles which indicated more plug flow conditions. The
large amount of dispersion occurred in the control pond and the amount of dispersion was reduced
with an increasing number of baffles in the ponds.
The investigations further showed that TN, NH3-N, COD and BOD5 removal efficiencies
increased with an increasing biofilm surface area or increasing number of baffles in the ponds. There
was not much difference of SS concentration in the effluent from the control pond to the 6 baffled
pond from the pilot-scale experiments. No significant removal efficiency of TP and faecal coliform
with an increasing biofilm surface area was observed within the range of the biofilm surface area in
the experiments.
The principal mechanism ofNH3-N removal was due to the biological uptake ofNH3-N by
the attached and dispersed biomass that eventually settled to the pond bottom or overflowed in the
pond effluent. Nitrification processes were increased remarkably from the pond with biofilm surface
area of 166 m2 to the pond with biofilm surface area of 1126 m2 which were mainly due to an
increasing of biofilm surface area, high DO and water temperature in the actual condition. Combined
algal/bacterial biofilm grown on the baffles immersed in the ponds showed potential for increasing
the extent of nitrification. NH3-N volatilization also played major roles in NHr N removal, especially
when operated at long HRT.
The computed COD and BOD5 removaf efficiencies encompassed the first-order reactions of
both the suspended and biofilm biomass were higher than that without the biofilm biomass activity
and agreed well with the observed data. The kinetic coefficients of organic carbon removal
determined from the experiments can be summarized as follows:
Average biofilm thickness from the laboratory-scale experiments were in the range of
44-603 µm, whereas from pilot-scale experiments that were in the range of 86-209
µm.
-11-
First-order rate constant of biofilm biomass, Kra, from the laboratory-scale
experiments were in the range of 123-490 d-1, whereas from pilot-scale experiments
that were in the range of 107-197 d-1
.
The installation of 6 baffles in WSPs which corresponded to the biofilm surface area of 1126
m2 resulted in land reduction of about 30, 60 and 48% in terms of BOD5, TN and NH3-N removal
efficiencies, respectively. The land savings which could be achieved would depend on the eflluent
quality standards which were allowed. |
| Year | 1996 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. EV-96-2 |
| 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) | Samorn Muttamara |
| Examination Committee(s) | Chongrak Polprasert; Visvanathan, C.;Vongvisessomjai, S.;Pescod, M.B. |
| Scholarship Donor(s) | Royal Thai Government |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 1996 |