Page 235 - Membranes for Industrial Wastewater Recovery and Re-Use

204 Membranesfor Industrial Wastewater Recovery and Re-use

Table 4.8 Maximum influent concentration for the processes in textile manufacturing
ss Colour BOD COD Salt Temp.
(PPm) (Pt-Co) (PPm) (PP4 ("C)
Steam production 5 10 5 10 0 25
Cooling" 5 10 5 10 0 12
Desizing 5 100 100 200 0 60
Prewashing 50 2000 100 400 2 40
Bleaching 5 10 5 10 0 60
Mercerising 5 10 5 10 0 60
Dyeing 5 10 5 10 0 60
Printing 5 10 5 10 0 60
Final hot washing 5 10 5 10 1 60
Final cold washing 5 10 5 10 1 25
Maintenance 100 2500 200 400 4 60

a The influent concentrations for cooling are set this strict to allow for later reuse of the resulting hot
water for all steps in the manufacturing process.

Water discharged to the sewer system is set at a cost of €1 per m3, and to
surface water (on meeting discharge consents) cost of €0.1 per m3. In reality the
levies for discharge both on the sewer system and the surface water depend on
the pollutant load in the effluent. Such a complex relationship cannot, however,
be used in the software and instead fixed values must be used. Recalculation after
optimisation is necessary to properly account for this.
The concentrated stream from the central wastewater treatment plant and the
concentrated polluted streams from individual purification techniques can be
treated separately in dedicated treatment facilities outside the textile company at
a cost price of €1 00 per m3.

Purification techniques
Amongst the purification techniques (Schonberger, 1998) two important
groups can be distinguished:

0 processes capable of recovering of one or more of the reagents for reuse in
the manufacturing processes, many of them also producing a highly
purified effluent water which can easily be reused, and
0 processes capable of recovering water for reuse purposes.
Data are summarised in Tables 4.9 and 4.10.
Selected purification techniques and cost data for these comprise the
following.
Ultrafiltration for recovery of sizing agent (European Commission, 2001). The
process is assumed to recover both the sizing agent, which can be reused in
the process, and good-quality effluent water for reuse. Capital cost for a
100 m3 day-' plant is around €1.2 million, including the UF plant, an
equalisation tank, start-up and miscellaneous. Eventually a prefiltration step has
to be accounted for. Savings up to €0.7 million per year due to product recovery