Environmental Engineering Reference
In-Depth Information
iltration technology superior to dual media sand/anthracite ilters. In conventional medium,
the large grains settle irst and the ine grains settle last, thus clogging the ilters. This is con-
trary to the situation in crumb rubber media. A conventional ideal ilter medium consists of a
coarse media at the top, a medium-sized media in the middle, and a ine media at the bottom.
The disadvantage is that it causes plugging of ilters and reduction of iltration time. Unlike
crumb rubbers, conventional ilters like anthracite/sand do not exhibit an elastic behavior.
The spread of dengue in Pakistan, Vietnam, and other south Asian countries took a
heavy toll of lives, and junk rubber tires were a major component in the transmission of
the virus as the tires act as containers for breeding of the mosquito species
Aedes aegypti
.
Three factors, namely crumb rubber's elasticity and favorable porosity gradient for iniltra-
tion, its antipathogenic properties, and the development of green technology (recycling),
were the major factors that motivated the use of crumb rubber technology for iltration. To
strengthen the technology, it is believed that this technology could be applied in combi-
nation with UV exposure to provide cleaner water to lood victims, where the loodwater
is highly contaminated and turbid. To provide cleaner water, this technology could be
combined with a photocatalytic treatment. The effect of ultraine particles of rubber (nano-
rubber) on the iltration rate was also investigated; however, they adversely affected the
iltration rate, unlike crumb rubber.
1.3 Experimental
Sizes of crumb rubber ranging from 0.8 to 1.5 mm, 1.5 to 2.5 mm, and 2.5 to 5 mm were
selected for the iltration column. The sizes were determined by sieve analysis using
ASTM method 136-01. The density of the crumb rubber is 1130 kg/ml. The design of
crumb rubber reactor constructed is shown in Figure 1.1. The iltration column was con-
structed from polytetraluoroethylene, to provide a reasonably strong transparent and
nonsticky surface. It was 1.5 m long and 10 cm in diameter. The inluent turbid water
was supplied by a water pump from a reservoir. For backwashing, an air pump was
connected to the bottom. The rate of iltration was controlled by a low meter installed
at the outlet pipe. The crumb rubber media was washed and dried before pouring in
the column. The depth of the ine medium and coarse media was 0.2, 0.4, and 0.6 m, to
provide different contact times for the media to remove suspended and total dissolved
solids (TDS), after a series of experiments. Experiments were conducted at 30, 50, and
70 m
3
/h m
2
(h = hours). The principle of the design was similar to that reported by
Al-Anbari [16] and Xie [17].
A stainless-steel mesh dish was used as a support. For head loss measurements, ports
at equal distances were drilled throughout the column. A constant water head was main-
tained for the inluent. For head loss measurement, the difference between the water level
above the ilter and the water level in the glass tube was measured.
A turbidity meter was used to measure turbidity in NTU (nephelometric turbidity unit).
The light scattering of particles by a focused beam is measured using a nephelometer with
a detector. Head loss was measured in meters.
For biological analysis, all equipment, including autoclaves, glassware, and Petri dishes,
were sterilized. The sample size was 100 ml. The grid side of the micron ilter paper was
placed upward. The iltering apparatus had a magnet at the bottom. The unit was placed
on top of the iltration unit. A hose was connected to a vacuum pump. The samples were
