Industrial water use accounts for approximately 20% of global freshwater withdrawals. So industries should be encouraged to invest in better water efficiency, more recycling and management for freshwater conservation. Industrial water reuse has the following specific benefits, in addition to reduction in water consumption and pollution load to the environment.
- Potential reduction in production costs from recovery of raw materials in the wastewater
- Less permitting and administrative burden from the reduction in wastewater toxicity and volume
- Heat recovery and reduced impacts from high temperature effluent to the ecosystem
2) Outline of Industrial Process Water Reuse
Industrial Process Water Reuse can be through internal recycling and cascading use of industrial process water. It can also be utilized for heating in production process or making hot water for domestic use through recovering its thermal energy.
Figure 6 Cost reduction potential from wastewater reuse
Water quality concerns for industrial water reuse include scaling, corrosion, biological growth, and fouling. These concerns are often interrelated one another. These problems can be prevented by reduction of dissolved suspended solids, salts, ammonia, phosphorous and residual organics through treatment like flocculation and filtration.
4) Example of Industrial Process Water Reuse
(Recycling of Part Wash and Rinse Water)
The automated process utilizes various membrane technologies, as shown in the flow diagram below. For example, oil and dirt are separated from the rinse water by an ultra filtration membrane. The detergent is then removed from the water by reverse osmosis, and reused in the washing process. The ion-exchange resin can be used to treat water to be recycled as rinse water as needed.
Figure 7 Flow diagram of washing process
(UF: Ultra filtration, RO: Reverse Osmosis, AC: Activated Carbon, IE: Ion Exchange resin)The environmental and economic benefits of this process are significant. For example, the volume of water usage and discharge is 0.5% of the previous process. The running cost is one-tenth of an alternative, adsorption treatment that uses activated carbon and ion-exchange resin. The maintenance requirement is once a month or less. (Asahi Engineering, 1999)
Source: GESAP http://nett21.gec.jp/gesap/themes/themes2.html
