Page 480 - Industrial Wastewater Treatment, Recycling and Reuse

450 Industrial Wastewater Treatment, Recycling, and Reuse

Often necessary sensors, such as the interstage pressure transducers,
are not installed. Even if all the necessary sensors are in place, if the reg-
ular maintenance and calibration required is neglected, data that is not
representative of actual conditions is generated and cannot be used for
assessing the health of the system.
c. Insufficient resources to make the proper changes.
The RO system might only be allocated minimal operator time with
limited operator expertise.
d. Change in operation or water source since the original installation.
The performance of an RO system can get significantly affected by a
variety of changes in the system, its operation, or in water sources. But
often due to lack of expertise, these changes get overlooked or ignored,
resulting in poor performance.
e. Mechanical limitations of equipment.
Occasionally, the installed equipment has limitations, such as pumps
having inadequate capacity, resulting in insufficient flow or pressure, or
sensors having improper range, resulting in erroneous data.
f. Bad design.
The key parameters that go into the design of an RO system include
the feed water composition, feed temperature, feed pressure, and recov-
ery. Sometimes, in order to reduce costs, system designs are compro-
mised, leading to poor performance. RO membranes need to be
protected from contaminants that can cause scaling or fouling. Therefore,
a good pretreatment section comprising appropriately selected filters is a
must. When designing, it is equally important to consider all details such
as the selection of dosing points for the chemicals. The system designers
should not compromise on any of these aspects.
Years of learning, gathered from practical experience in running RO sys-
tems, have helped in bringing some best practices (Kucera, 2010) to surface,
which should be followed when operating any RO system (Table 11.1). The
most essential aspect for ensuring that an RO system operates well is to mea-
sure proper parameters and use normalization before interpreting the data.
Table 11.2 lists the parameters for which the data should be collected, at the
minimum (Flynn, 2009). The collected data should then be normalized
before it can be used for comparison with previous data or for trending.
As mentioned earlier, these parameters are functions of temperature, solute
concentrations, and pressure. As these conditions vary continuously, it is
impossible to interpret any useful information by directly comparing data
collected at different times.