Page 133 - Sustainability in the Process Industry Integration and Optimization

110 Cha p te r F i v e

Product Virtual water (L)
1 glass of beer (250 mL) 75
1 glass of milk (200 mL) 200
1 cup of coffee (125 mL) 140
1 cup of tea (250 mL) 35
1 slice of bread (30 g) 40
1 slice of bread (30 g) with cheese (10 g) 90
1 potato (100 g) 25
1 apple (100 g) 70
1 glass of wine (125 mL) 120
1 glass of apple juice (200 mL) 190
1 glass of orange juice (200 mL) 170
1 bag of potato crisps (200 g) 185
1 egg (40 g) 135
1 hamburger (150 g) 2400
1 tomato (70 g) 13
1 orange (100 g) 50

TABLE 5.1 Virtual Water Consumed while Processing Selected Food
Industry Products (after Hoekstra and Chapagain, 2007)

factors will affect the choice of technologies to be adopted, including
those that involve water and wastewater.
A comprehensive survey of water and wastewater applications
for the processing industry can be found in the books of Smith (2005)
and Klemeš, Smith, and Kim (2008). Most of these techniques for
water minimization fall into one of two groups:
1. Process changes: This category groups fundamental changes
in unit operations that consume fresh water. Examples
include increasing the number of stages in an extraction
process to reduce its consumption of water, changing from
wet cooling towers to air coolers, improving energy efficiency
to reduce steam demand, increasing the condensate return
from steam systems, and improved housekeeping. Good
housekeeping practices include analyzing and measuring
water use and wastage, reducing water wastage, regular
cleaning operations, and equipment maintenance.
2. Reuse, recycling, and regeneration: These options enable the
reuse of wastewater between water-consuming operations. Of
course, the presence of pollutants in wastewater streams