Page 24 - Materials Chemistry, Second Edition

Ch001-P373623.qxd 3/22/07 5:25 PM Page 5
5
Current Practice and Future Sustainability
to recover the raw material in order to conserve the natural resources on the
condition that there is a full utilization or recycling of all effluents from the
treatment facility”. The first example of sustainable treatment is through
mechanical treatment or recycling to convert waste into raw material and
produce other products as explained above and will be explained in detail later
on. The second example of sustainable treatment is through biological treat-
ment to convert organic waste into a safe byproduct such as composting.
Composting is an aerobic biological treatment process to convert organic
waste into soil conditioner or organic fertilizer as will be discussed in detail
in Chapters 5 and 7. The third example of sustainable treatment is through
physical treatment to separate the waste streams from each other, for exam-
ple the gravity oil separator (GOS) separates the oil and grease from oily water
by gravity. The oil and grease can be recycled into the industrial process and
the water with some remaining oil can be further treated physically through
a dissolved air flotation (DAF) unit to separate the remaining oil and recycle
both the remaining oil and water into the industrial process. The fourth
example of sustainable treatment is through chemical treatment to separate
raw material from waste by precipitation such as chromium recovery from
liquid waste effluent produced by the tanning industry through pH control.
It is necessary for any establishment to treat its waste so that it com-
plies with environmental protection regulations. Some industries resisted
compliance in order to avoid costs. Now, new industries are accepting waste
treatment as an integrated part of production cost. The added costs must
then be passed on to consumers or deducted from the profits of the firm
depending on market competition.
Through the traditional waste management hierarchy, hazardous waste
should be treated before final disposal according to international regula-
tions. Therefore, treatment means converting harmful waste into less harm-
ful waste. In other words, treatment means converting waste from one form
to waste in another form. The direct cost of waste treatment is more than just
the expense of capital equipment and running cost (maintenance, operation
and labor). This direct cost represents only a portion of the total cost. The
other indirect cost may not be as easily identified and quantified. This includes
the disposal cost and the cost related to adverse impact of the waste on the
environment – contaminating air, water and land – as well as the equivalent
cost of depleting the natural resources.
Some industries claim that it is not possible to have both jobs and capital
spending for growth and at the same time, clean air and water. This statement
is not true for industry, because wastes and emissions were originally raw mate-
rial and should be treated as a byproduct not as a waste through reusing, recy-
cling or recovery techniques – or sustainable treatment, a more generic term.
Treatment should be modified in the hierarchy of waste management
for conservation of natural resources to sustainable treatment such as mate-
rial recovery through physical treatment or biological treatment, etc., as
explained above. In other words, what degree of treatment is required to