Page 237 - Membranes for Industrial Wastewater Recovery and Re-Use
P. 237
206 Membranes for Industrial Wastewater Recovery and Re-use
sizing agent. Operating cost is assumed to be €0.1 per m3, based on the same
assumption of a cost recovery as the IJF plant.
Membrane treatment for recovery of wastewater from printing paste (European
Commission, 2001). Capital cost for a 60 m3 day-l plant is €0.82 per m3 based
on a 10-year depreciation period at an interest rate of 0%. The installation
comprises coagulation/precipitation pretreatment followed by a microfiltration
unit using a polypropylene membrane and a tube settler to remove the
suspended solids. Operating cost, including external disposal of the concentrate,
the principal contribution to opex, is about €4 per m3.
Membrane treatment for recovery of wastewater fromfinal washing. Capital cost is
assumed to be €0.33 per m3 for an ultrafiltration installation of 250 m3 dayp1.
Operating cost is assumed to be €0.25 per m3.
Centralised biological wastewater treatment plant (European Commission, 2001).
Capital cost is taken at €1.25 per m3 for a 2500 m3 dayp1 plant (10-year
depreciation at an interest rate of 6.88%). The investment cost given in the paper
(European Commission, 2001) was €1.50 per m3, although this included
further purification (by reverse osmosis) of the effluent for reuse. The plant
comprises equalisation, neutralisation, and activated sludge treatment in a
special system of loop reactors and clarifiers, adsorption to remove dyestuffs,
flocculation/precipitation and removal of sludge, and filtration in a fixed-bed
gravel filter to remove suspended solids. Also included is the treatment of the
sludge in a thickener and decanter and thermal regeneration in a rotary kiln.
Operating cost is taken at €0.6 per m3, based on the above, including ash disposal
and ignoring heat recovery.
Reverse osmosis for polishing the treated wastewater (European Commission,
2001). Capitalcostistakenat€0.2Sperm3 fora 1500m3 day-' plant.Investment
comprises the reverse osmosis plant consisting of 10 modules containing 4 spiral
membrane elements each. Included is a storage tank conditioned with ozone to
control biological growth. Operatingcost is taken at €0.1 per m3.
Results
Base case: targeted minimum flow rate, discharge to sewer. For the base case it is
assumed the company is required to meet stricter consents for discharge to
sewer. In the first instance a large central wastewater treatment plant can be
envisaged for the treatment of the overall wastewater.
The result of the base case reveals that 12 10 m3 day-l of fresh water is needed
with all effluent from the cooling process being recycled (350 m3 day-l waste
from a 1560 m3 dayp1 feed). No other effluents are identified for reuse taking into
account minimum operating cost. The effluent of the central wastewater
treatment plant meets the strict discharge consents for both SS and BOD. Only
378 m3 day-' needs to be treated in the central plant, the remaining effluents
being discharged directly to sewer. The daily cost of this base case is €6387,60%
of this being due to the external treatment of the concentrated waste.
Scenario I: targeted minimum flow rate, all purification techniques permitted. For this
case it is presumed the company was seeking alternative ways of minimising the