Page 95 - Industrial Wastewater Treatment, Recycling and Reuse

70 Industrial Wastewater Treatment, Recycling, and Reuse

chemical and petrochemical industries. The cost of treating wastewaters is also
quite significant, requiring complex design and operations apart from main-
tenance. Thus, separation science and technology in wastewater treatment is
no longer just an operation to purify/recover products but also an important
tool for improving cost competitiveness, boosting energy efficiency, and
increasing productivity with the ultimate goal of addressing environmental
concerns. Separations from dilute solutions have been receiving wide
attention recently because of the need for recovery of small quantities
of high-value materials (e.g., in the pharmaceutical industry) and removal of
contaminants from dilute aqueous and organic streams. In the case of high-
value materials, it becomes value addition to the existing process, while for
low-value chemicals, it is challenging to find economically feasible separation
processes to recover materials or to address environmental concerns.
Cost calculations in most wastewater treatments are not straightforward.
They require not just an understanding of the process operations but also of
upstream fallouts of the process modifications and further effects down the
line after effluent discharge/recycling/reuse. It is easy to calculate the cost of
processing for a specific pollution problem involving a particular stream con-
taining defined pollutants with known concentrations, volumes for treat-
ment, and method of treatment. However, often there are process
changes that alter the composition of the wastewaters. Further, a number
of separation processes compete with each other, and outlet water charac-
teristics of each are very different. It can be said that employing a much
cleaner process using environmentally friendly reactions and separations
would provide a much simpler and cost-effective option in environmental
pollution control rather that allowing pollutants to get discharged into the
water pools/rivers and affect people and the environment, the cost of which
is incalculable. The situation can be disastrous with toxic pollutants.
A common belief in wastewater treatment relates to only considering
treating wastewater to make it suitable for discharge in surface waters/rivers/
water ponds. The fact that wastewater can be considered as a useful and
potential resource is grossly ignored. Some important recommendations
in this regard are:
1. Wastewater treatment, recycling, and reuse for the purpose of agriculture
can be quite straightforward for many industrial and sewage wastewaters.
The cost benefits include reduced freshwater requirements and thus low-
ered costs of obtaining water, conserving fresh water resources, improv-
ing soil conditioning through nitrogen/phosphates in the recycled water,
and preventing discharge of pollutants to surface and groundwater. The