Page 469 - Industrial Wastewater Treatment, Recycling and Reuse

3D TRASAR™ Technologies for Reliable Wastewater Recycling, and Reuse 439

of 5000 tons (cane crushing capacity per day) could generate about 1000
cubic meters per day of process condensate from the second effect alone.
This is a large amount of water that could be reused. These higher effect
condensates (second effect and higher) could be returned to low-pressure
boilers, because there is a threefold benefit in reusing these condensates:
• Process condensate in a sugar mill represents a large quantity of water.
• Most often the quality of process condensate is very good.
• Process condensate contains valuable heat energy.
In regions where water is scarce and power co-generation is practiced by
sugar mills, the condensates could also be reused in the co-generation cool-
ing towers. However, many mills send these process condensates to ETPs or
are not able to maximize the utilization of these condensates because they do
not have online monitoring technologies that can help them reuse these
streams reliably.
As this condensate is being generated during an evaporation process, it
has heat content and is generally of a quality that is much better than the
raw water quality. It is also low in dissolved solids, with conductivity gen-
erally in the range 50–250 mS/cm. It has low levels of organics (mostly vol-
atiles), with total organic carbon (TOC) ranging between 30 and 200 ppm.
Based on how the mill is set up, the contribution of the process condensate
to the total effluent going to the ETP could be as high as 40%. However, the
quality of process condensate is much better in comparison with the other
wastewater streams, in terms of inorganic as well as organic contaminants.
Therefore, if this condensate is sent to the ETP, it results in a high hydraulic
but low contaminants load, which makes its treatment in the ETP difficult.
Also, if this is directly sent for drainage, it may result in high discharge costs
due to the large quantity involved.

11.2.2 Challenges in Reusing Process Condensate
To improve the water efficiency of the sugar mill, it is desirable to reuse the
process condensate in boilers or cooling towers. However, the biggest chal-
lenge in reusing these condensates is the unpredictable variation in their
quality. Occasionally, thin juice will mechanically carry over into the pro-
cess condensate stream. This event is known as a “sugar shot” and can hap-
pen when, for example, the juice levels in the evaporators are high or there
are pressure imbalances. The frequency and severity of the sugar shots is
unpredictable. The frequency could be as low as 1 or 2 sugars shots per sea-
son or as high as 1–2 per day depending upon how well the mill is being