| Author | Werellagama, D. R. Induka B. |
| Call Number | AIT Thesis no.EV-93-26 |
| Subject(s) | Water--Purification--Filtration
|
| Note | A thesis submitted in partial fulfillment of the requirement for the degree of Master of
Engineering |
| Publisher | Asian Institute of Technology |
| Abstract | Laboratory scale experiments were carried out in contact flocculation filtration using
a dual media filter. The objective of the research was to find an optimum synthetic media
combination which would give acceptable quality water under varying conditions while
maintaining a low headloss. The media was lighter than water hence the bed was floating.
Since coarse media remained at the bottom the flow direction was upflow which had the
added advantage that the flow was in the direction of grain compression. Polypropylene and
Polystyrene were selected as the optimum combination of media which due to their large
. density difference did not intermix even under severe agitation. Spherical fine media
performed better than angular fine media giving lower headloss and better effluent quality.
The dual media combination and the higher rates of filtration are in line with the current
trends in the water industry. The influent concentrations were kept constant and the flow
velocity and filter media size were varied. The headloss variation along the filter, the influent
quality to the two filter layers and the effluent quality were studied.
The filter performed for over 40 hours producing acceptable quality water at
conventional rapid sand filtration rates, also having low headloss development. Another
major advantage was the ease and economy in backwashing. The filter media did not mix
even during or after backwashing, thereby eliminating the most common problem
encountered in conventional multi media filters.
The Floto Filter operation was compared with upflow sand filtration. The headloss
development curves for Floto filter showed a characteristic shape easily identifiable from that
for sand.
The existing mathematical model was able to predict the headloss profile but the
concentration profile was not predicted. The necessity of particle size data for mathematical
modelling of filtration of heterodisperse suspensions is emphasized. |
| Year | 1993 |
| 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 (EV) |
| Chairperson(s) | Visvanathan, C.; |
| Examination Committee(s) | Fujii, Shigeo;Samorn Muttamara; |
| Scholarship Donor(s) | Swedish International Development Agency (SIDA); |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 1993 |