Page 269 - Membranes for Industrial Wastewater Recovery and Re-Use

238 Membranesfor lndustrial Wastewater Recovery and Re-use

membrane technologies. Ultimately, a combination of electrodialysis reversal
(EDR) and reverse osmosis was adopted to pretreat the waste flows prior to
evaporation.

5.3.2 Description of system
The water treatment plant is made up of three integrated treatment systems
designed to meet boiler feed water/steampurity and aZLDrequirement (Fig. 5.5):

0 Raw water pretreatment
0 Boiler feedwater (make up water) treatment
0 Wastewater treatment

The plant takes water from both the wastewater and potable water facilities at
Hanover county and discharges only solids in the form of filter cakes from both
the pretreatment and wastewater treatment plants.

Raw water pretreatment
The raw water pretreatment plant is designed principally for solids removal from
the incoming Hanover county sewage effluent (grey water), backwash water and
wastewater from the oily water collection system. Raw water enters a
coagulation/flocculation chamber followed by a clarifier and dual media depth
filters. Backwash water from the filters is periodically returned to the clarifier.
Clarifier sludge is dosed with polymer before being thickened and then sent to the
filter press for dewatering. The cake is sent to landfill and the recovered water
returned to the clarifier.

Make up water treatment
Treated raw water is mixed with potable water and pumped to the boiler
feedwater treatment system. The system is designed to remove 99% of the

Hanover
county
Potable water
Hanover
county
effluent Raw mter Make up Make up water
treatment To Dower block
Oiltwater treatment
0
Filter solids
To landfill
astemter
treatment

4
Filter solids
Figure 5.5 ZLDstrategy at Doswell combinedcyclepowerplant