The MBR Book: Principles and Applications of Membrane

262 The MBR Book
Table 5.24 Data for various Wehrle leachate and food effluent treatment plant
Customer/site: Units Freiburg Bilbao Kellogg Dairy Crest Dairy Gold
Application: Leachate Leachate Food Dairy Dairy
Airlift Pumped Pumped Pumped Pumped
Flow rate MLD 0.12 1.8 1.8 1.2 2.0
Membrane area m 2 88 700 864 486 648
Flux (year average) LMH 54 102 71 98 125
Flux (day average) LMH 57 107 87 103 129
Membrane price total € 19 360 189 000 198 400 111 600 163 200
Membrane life years 6 4 4.50 5.00 6.00
Membrane replacement €/a 3227 47 250 44 089 22 320 27 200
cost
Specific energy demand b kWh/m 3 3 5 3.75 3.18 2.14
Specific energy cost €/kWh 0.06 0.06 0.06 0.06 0.06
Total energy cost €/a 7490 187 245 121 564 79 347 91 264
Total operating cost c €/a 10 716 234 495 165 653 101 667 118 464
Total specific operating €/m 3 0.26 0.38 0.31 0.24 0.17
cost
aMembrane � Biology � Civils
bUF stage
cSum of energy and membrane replacement
Robinson (2005).
Banknote paper is made from cotton combers bleached with sodium hydroxide and
hydrogen peroxide. The project concerned the use of an MBR, originally developed
for landfill leachate treatment, operating under thermophilic conditions for removing
colloidal and high molecular weight dissolved material to allow the reuse of
wastewater from the bleaching plant. The process, based on 8 mm diameter MT
polyvinyllidene difluoride (PVDF) membranes, has been piloted on a variety of highstrength
recalcitrant industrial effluents.
A trial was originally conducted between June and October 1999 for the clarification
of wastewater from the bleaching plant. Wastewater from the bleaching process
has a mean COD of 4500 mg/L, a pH of �12 and a temperature of 75–85°C. The
quality of the effluent from these trials, which has a COD of around 400 mg/L, was
sufficient to allow it to be reused in the bleaching vessels and led to the decision to
install a full-scale plant (Fig. 5.45) with a capacity of 0.24 MLD in November 2000.
The system comprises a buffer tank followed by a dual-chamber DAF process for
the removal of cotton flocks and fibres. In the second chamber, waste carbon dioxide
from the boiler house is introduced to lower the pH of the solution from �12 to 8–9,
an ingenious use of waste gas which reduces CO 2 emissions. The pH-adjusted clarified
effluent is then transferred to the MBR aeration tank, 250 m 3 in volume and thus
providing an HRT of �24 h. The MBR operates at between 55°C and 60°C and an
MLSS of 20 g/L. Three sidestream MT membrane units are employed (Fig. 5.46), each
comprising 6 � 3 m-long modules in series with each module having a membrane
area of 4 m 2 and hence providing a total area of 72 m 2 . The membrane units operate
at a mean flux of �120 LMH, an average TMP of 4 bar, and a mean crossflow velocity
of �4.5 m/s. The permeate COD concentration is 400–500 mg/L, and it is
reheated by passing it through a heat exchanger with the influent before being reused