Clean Water and Wastewater in Industrial Plants
The main industrial use of water is the transfer of energy: heating, cooling or production of steam to drive turbines. But it is also used as a reaction medium, as a means of transport, in the composition of products, as a cleaning agent, etc.
Unfortunately, in most cases, these processes are designed and applied with the certainty that water is cheap and abundant. This practice has occurred for several reasons: the low cost of water (compared to its value) and its easy availability; the high cost and complexity of Clean water Treatment; and the often mistaken belief that reusing water would have a detrimental impact on production.
If efficient water use is to be adopted voluntarily in industry, rather than being required by legislation, taxes, pricing policy or supply rationing, this must be taken into account in reuse technologies and practices and recycling.
The practices must be easy to manage, the technologies used must not be intrusive and the net present value (NPV) must be positive to compete with other investment requirements.
Principles of water reuse and recycling
The ideal factory would reuse all water. But this closed-loop situation can only be achieved by using excess energy to evaporate excess water, generating solids that must be removed. It is better to approach the reduction of water use as a journey in stages that are sustainable, both from an environmental and an economic point of view. The reuse and recycling of water must be paramount in the design of the plant, since the subsequent remodeling of the infrastructure is often difficult and expensive.
Of course, the wastewater could be redirected to the start of the process and replace the fresh water supply. However the quality of the water would inevitably be insufficient without costly treatment, which in turn could produce too good water for certain lower quality tasks. A more acceptable solution is a distributed water reuse and recycling system in which all available waste water can be recovered and reused (untreated) or recycled (reused after essential treatment), thus ensuring the protection of certain tasks critical, that is, those that require specific characteristics of the water. This principle is known as Distributed Effluent Treatment (or DET).
Elaboration of a reuse and recycling methodology
Before being able to define equipment specifications, it is essential to know the total flow of water and its composition, as well as the quality required by the function that will receive it. Furthermore, as reuse and recycling are introduced, they will inevitably influence these aspects. Therefore, it is essential that any plan be executed logically and progressively, starting at the Clean Water Solution end and progressing to the dirty water end. This leads to a logical hierarchy of activities from which typical savings can be deduced
Will it be economically viable?
In addition to the cost of water, other factors often decide the viability of reuse and recycling projects:
- Greater availability of water for future plant extensions.
- Reduction of wastewater evacuation costs and the possibility of recovering products and raw materials.
- Reliable compliance with discharge authorizations.
- Simplification of wastewater treatment technology.
- Greater capacity of the wastewater treatment plant to allow longer residence times and greater operational stability.
- Reduction of the capital necessary for the expansion of the wastewater treatment plant due to the lower quantity produced.
- Improvement of the image of the company.
- Extension of the operating permits for the plant, etc.
Some real examples can show the advantages of reusing and recycling water.
Real
Examples There are more and more examples of improving water consumption:
- Electric companies that only use wastewater subjected to tertiary treatment as a complement.
- Large chemical plants and industrial complexes that only receive wastewater with tertiary treatment for all their functions.
- Paper industries that have reduced water consumption by a factor of more than 20 over the last 30 years.
- Clean chemical plants that have reduced their net water consumption by more than 60 percent.
- Brewing industries that together have reduced their specific water consumption by more than 30 percent through efficiency measures.
Usually the determinants of these improvements have been the threat of local water scarcity, the pressure from the industries themselves to acquire an image of responsibility and concern for the environment and, perhaps most importantly, the simple economic benefit.