Page 263 - Membranes for Industrial Wastewater Recovery and Re-Use

232 Membranesfor lndustrial Wastewater Recoverg and Re-use

5.2 Erarin Power Station: purification of secondary sewage for
boiler fee 8 water (Australia)

5.2.1 Background
Pacific Power's Eraring plant is a 4 x 660 MW coal-fired power station,
situated on Lake Macquarie which provides about 25% of the power
requirement to New South Wales. The power station utilises salt water from the
lake for condenser cooling with all other water supplied as potable by
Hunter Water Corporation. Prior to 1988 potable water usage was almost
8.5 M1 d-l and represented one of the three largest costs to the power
station. To reduce costs a water audit was conducted to identify the major
areas of use. After engineering modifications the water use was reduced to
4 MI d-l:

0 In the chemical control room, where various water samples are
automatically analysed, the supply was modified from using potable water
to using recirculating auxiliary cooling water.
0 In the ash and dust system, gland sealing water was changed over
from potable water to salt water. This increased costs in the ash and dust
area but the saving in water costs overshadowed the increased
maintenance.
0 The wash down systems were modified to small high pressure nozzles.
The audit indicated that significant savings could be made if another supply of
process water could be found. A source became available when the Hunter
Sewage Project upgrade of the local Dora Creek sewage treatment plant was
initiated. As part of the upgrade a new wastewater treatment plant was to be
built at Dora Creek which is approximately 6 km south of the power station. The
sewage effluent was to be pumped under Lake Macquarie to an extended ocean
outfall. The discharge pipeline was due to pass close to the power station and so
reuse became an option.
Following a detailed review period, a deed of agreement was signed between
Pacific Power and Hunter Water Corporation for a guaranteed 15-year period.
During this period Pacific Power must accept all secondary effluent up to a
maximum of 5.2 M1 d-l. The effluent quality from the Dora Creek sewage works
(Table 5.2) means that additional treatment is required prior to use at the power
plant. The principal use of processed water is for demineraliser feed with the
remaining flow being used for other water applications on site:

0 Demineralising plant (1.5 M1 d-l)
0 Auxiliary cooling towers (1 MI d-l)
0 Wash down water
0 Fire services
0 Ash disposal system (1-1.5 MI d-l)