| Author | Krishna, Manandhar Uttam |
| Call Number | AIT Thesis no.EV-90-2 |
| Subject(s) | Water--Purification--Filtration
|
| Note | A thesis submitted in partial fulfillment of the requirements of Master of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Abstract | Most of the mathematical models of deep bed filtration had
been restricted t o s ingle layered media of uniform size operating
with constant influent concentration and single influent particle
size at constant filtration rate. But this is not t h e case in
reality. Therefore , in this study, modified O ' Melia-Ali mode l
based on particle collector concept and detachment mech an ism has
been extended to incorporate these factors.
Media size gradation was considered in the model by assuming
that media size varies l in early with the depth in the direction
o f flow. The removal efficiency equations were solved numerically
by dividing the filter into infinitesimal depth increments. and
making time increments to cover the who l e filter r un time. For
each depth increment, it is checked which me di a layer of t h e
multi media filter it lies in , and the corresponding media
characteristics were considered. Th u s the multi media
characteristics has been incorporated in the model. Similarly,
the model has been modified to varying influent concentration
based on two basic assumptions that the variation in influent
concentration is negligible during short time interval, and the
retention time of the f1uid in the fi1ter media is . negligible
compared to the total filtration time. Also the suspended
particle size distribution was considered. The improvement of
removal efficiency of finer particles in presence of coarser ones
in suspension was assumed to be due to the fact that some of the
retained coarser particles ·in addition to finer particles act as
"particle collectors " in the removal of finer particles. This
study gives an approach which reduces the number of model
parameters to be estimated by grouping different values of t he
model coefficients for particles of different sizes with
relations of the form, ap= APB1*dp APB2 and 2= BET1*dp BET2.
The model has been teste d with extensive experimental data
obtained from pilot scale filtration studies in Bangkhaen Water
Treatment Plant for the case of media size gradation and varying
influent concentration . The predicted results fit reasonably well
with the experimental one. For the case of particle size
distribution, data from Antwerp Water Works (Center for Water
Research, Belgium) has been used. The prediction was better for
the case of finer particles compared to the bigger ones; the
predicted curves having more similar trends as the experiment a l
ones during the ripening stage t h a n during the breakthrough. For
the case of declining rate , the water balance equation was
included to solve for unknown filtration rate. The model could
not be verified for the case of declining rate filtration due to
unavailability of experimental data in p roper format. Th is has
been used to see the behaviour of a hypothetical case formulated ,
which indicated two major advantages of declining rate filtration
over constant rate filtration. They are , prolonged working period
and better filtrate quality for the same terminal headless
development.
Finally, the empirical relations developed for Bangkhaen
Water Treatment Plant pilot scale filter data were used to
illustrate its applicability for the filter optimization. |
| Year | 1990 |
| 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) | Vigneswaran, Saravanamuthu |
| Examination Committee(s) | Verink, Johan ;Schroder, Hans
|
| Scholarship Donor(s) | The Royal Danish Government |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1990 |