Page 466 - Industrial Wastewater Treatment, Recycling and Reuse

436 Industrial Wastewater Treatment, Recycling, and Reuse

developed to automatically handle such dynamic variations and ensure effi-
cient system operation. One of these technologies is specific to the sugar
industry, while the other can be applied across several industries wherever
a critical reverse osmosis (RO) operation is used. These technologies have
demonstrated significant water savings, energy savings, and asset protection
and will be described in the following sections.
The sugar industry is under increasing pressure from the environmental
regulatory bodies to reduce its fresh water consumption and effluent dis-
charge. Also, several sugar mills are located in regions where the raw water
has become scarce and poor in quality over the past several years. It is also
interesting to observe that sugar mills can generate power using bagasse, which
is a byproduct of the sugarcane milling process. For setting up and operating
such co-generation power plants, sugar mills receive subsidies. The surplus
power generated is sold back to the central power grid, providing an addi-
tional source of revenue for the mills. Most of these co-generation power
plants utilize condensing turbines, which require additional water for the
cooling water circuits needed for running the condensers. Therefore, in view
of the imposed regulations, unavailability of good-quality raw water, and
increased water requirements, the mills are pressed to recycle the wastewater.
In the sugar industry, a large amount of water is generated in the form of
vapor condensate in the evaporation processes. This vapor condensate is of
good quality most of the time and can be reused in low- to medium-pressure
boilers and co-generation cooling towers. However, this vapor condensate
is largely discarded due to dynamic variation in its quality because of sugar
contamination, which cannot be predicted. Wet chemistry tests are still the
most widely used methods for detection of juice contamination in the con-
densates. These are done manually once or a few times per shift and are labor
intensive. Another major limitation of relying on these tests is that if a con-
tamination event occurs in between the successive testing, it would most
likely be missed. For this reason, many sites have added online conductivity
analyzers in conjunction with the manual wet chemistry tests. However,
conductivity analyzers are not sensitive toward the detection of trace levels
of contamination. The 3D TRASAR Technology for Sugar is a unique
online, fluorescence-based monitoring technology that is able to detect
these variations with high sensitivity and selectivity, thus providing early
detection. This has enabled mill owners to automatically and reliably reuse
these condensate streams in their boilers and cooling towers.
Membrane filtration processes are integral to several of the recycling sys-
tems. Nanofiltration (NF) and RO filtration systems are being increasingly