| dc.description.abstract | In,general, it has been observed from past
experience that there are numerous limitations and
operational problems associated with the conventional
downflow filters. Intensive research in many parts
of the world, particularly in Europe, America, and
Russia lead to the introduction of many improvements
on the operation and design of filters. An upward
flow filter is one such innovation which was found
to offer many advantages over the conventional
downflow filters; in terms of compactness of plant,
turbidity removal, higher filtration rates and the
generally low operational and maintenance costs.
It has been identified that one of the
major causes of slow sand filter failures, in Kenya
is high raw water turbidity. There is therefore a
need for research to alleviate this problem.
TWo pl10t plants were set up. One was at the
Environmental Health Engineering Laboratory. 'I'h i s
pilot plant utilised?artificially prepared turbid
raw water. The parameters of t.urbidity, colour I
headloss development and pH variations were monitored.
Nine test runs were carried out in all using
vari ab Le f LLt.r at Lcn rat.es of C.? m/hr to 1 m/hr. The
influent turbjdity varied from 10 FTU to 170 FTU.
No pretreatment of the raw water was provided.
The second pilot plant was set up at Kabete
water works with naturally turbid water. No pretreatment
was also provided. The parameters of turbidity colour
and pH were monitored. An attempt on microscopic
investigation into the presence or absence of
Plankt~life in the filter was eventually aband6ned
when the slides inserted into the filter became
constantly covered with sand. Four test runs were
made using this filter.
Experiments with fille sand media of effective
size 0.22 rom and coefficient of uniformity of 2.46
gave unsatisfactory results. The sarid media was
too fine and lower depth of the filter media tended
to clog rapidly with high values of raw water
turcidity.
Recomendations on areas of future research
have been made. | en |
