Page 23 - Membranes for Industrial Wastewater Recovery and Re-Use

4 Membranes for Industrial Wastewater Recovery and Re-use

works have the capacity to treat these industrial waters simply by virtue of
blending with domestic water, significantly dampening the effects of broad
temporal variations in quality and the concomitant shock loads of specific
problem contaminants that arise. In other words, existing municipal wastewater
treatment works are often able to cope with industrial effluents at a cost that is
considered reasonable. The loss of the industrial effluent biological and hydraulic
load from a sewage treatment works designed to accept it may even cause
operational problems. Moreover, a municipal water supplier is able to provide
mains water of a quality consistent enough to be reliably employed in most
industrial processes. A reduction in mains water consumption and efnuent
discharge has a negative impact on the revenue of the water supplier and sewer
operator companies, who are often one and the same company. Given these
implications, it is prudent to consider industrial water usage and discharge as a
whole.

1.2 Industrial water
Industry accounts for about a quarter of all water consumption, and there is
hardly any industry that does not use large volumes of water (Table 1.1).
Although some industries abstract water from rivers and boreholes, much of the
water used by industry is taken from public water supplies, and has therefore
been treated to potable quality standards. This means that it is often of better
quality with respect to microbial levels but nonetheless requires further
purification to reduce the mineral and organic materials content according to
the specific duty to which it is to be put (Tables 1.2 and 1.3). Although water
consumption has actually decreased over the last 15 years in some regions of the
world (Table 1.4), the price of supply and discharge has risen substantially over
the same period. According to figures for the UK, the average cost of water supply
and sewerage services to unmetered customers has more than trebled in the last

Table 1.1 Approximate water demand for various industrial sectors
Industry Water demand
Paper 29 m3/t paper produceda
Newspaper 9 m3/t paper producedb
Brewing 10-1 5 m3/m3 beerb
Dairy 140 m3/m3 milkh
Sugar 8 m3/t sugarb
Automotive 450 m3/car (metalproduction)h
Automotive 760 m3/car (tyre production)b
Dying 100 m3/t fabric processed
Soap 2 m3/t soap produced
Power 3 m3/MWh for steam;
60 m3/MWh for cooling
aEU figure (Pauly 2001).
bGleick, 2000.