| Author | Parameshwaran, Kathiravelu |
| Call Number | AIT Thesis no. EV-97-32 |
| Subject(s) | Sewage--Purification--Reverse osmosis process
|
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. EV-97-32 |
| Abstract | The possibility of using microfiltration hollow fiber membrane modules as air diffusers
and solid/liquid separator in an alternative cycle for activated sludge process treating domestic
wastewater was studied. The activated sludge system consist of anoxic and oxic zone for better
nitrogen removal. Two hollow fiber microfiltration modules with the pore size of 0.2 µm were
immersed in a 80 L oxic tank (.MBR) to effect the direct solid/liquid separation. Filtration and
high pressure air backwashing were employed in an alternative cycle to have improved flux
rate. Back washing of membrane with air in turn aerate the activated sludge in the reactor. By
doing so, distinct advantages of declogging of membranes as well as aerating reactor contents
were achieved simultaneously.
In a short term experimental runs, it was found membrane modules are better air
diffusers than stone air diffusers. It was also found that the increased back wash air pressure
lead to an improved flux rate.
In long term experiments, efficiency of membrane coupled bioreactor system at
different hydraulic retention times (HRT) of 15, 10, 6 and 3 hours were studied. Wastewater
was fed to the anoxic tank which in turn pass into the .MBR. Content of the .MBR was recycled
to anoxic tank to effect denitrification. The average IvfLSS concentration in the system was
varying between 12,000 to 14,000 mg/Land the sludge age in the .MBR was maintained at 50
days through out the study. Though the desired HRT could be maintained at 15, 10 and 6 h
with a moderate transmembrane pressure only ( < 42 kPa) it was not possible in the case of 3
h. After two weeks operation in later case, stable HRT of 8.5 h at 96 kPa transmembrane
pressure, could be obtained.
Irrespective of the operating conditions, in all experiments COD, BOD, TKN and total
nitrogen removal of more than 95, 98, 95 and 80 % respectively were achieved. This study
establishes that using hollow fiber membrane capable of air backwashing to solid/liquid
separation will lead to a situation of aeration of mixed liquor and declogging of membrane
modules simultaneously, so conventional aerators can be eliminated. By using anoxic/oxic
system efficient total nitrogen removal also can be achieved. |
| Year | 1997 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. EV-97-32 |
| Type | Thesis |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Environmental Engineering and Management (EV) |
| Chairperson(s) | Visvanathan, C. |
| Examination Committee(s) | Eckhardt, Ing. Heinz;
Sompol Boonthanon |
| Scholarship Donor(s) | Swedish International Development Cooperation Agency (Sida) |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1997 |