The Brazilian legislation is very strict with the industries with respect to environmental responsibility and the treatment of effluents from industrial production. Not least: industries are the largest pollutants in the country and annually discharge thousands of tons of toxic wastes in the waters of rivers and streams, as well as reaching groundwater.

All this seriously damages the quality of water that will be collected at other points for treatment and distribution, as well as the quality of life of the population bringing a multitude of waterborne diseases. These problems can be solved in large part by the correct treatment of industrial effluents.

Effluents are liquid and gaseous wastes from industrial production. Liquids and gases used in production are contaminated by toxicants (metals, chemicals, etc.) and require treatment before being disposed of in the receiving body.

There are several ways to treat industrial effluents. The treatment processes are basically three: physical, biological and chemical. Physical processes are those that separate the solids by decanting, grading, sieving, filtration, among others.

The biological processes have the objective of separating the solids and remove them by an acceleration of the processes of nature (decantation or flotation, for example), using biological organisms for this purpose.

The chemical processes, finally, are those that use coagulation agents, pH neutralization, oxidation or flocculation, among others, to expedite the treatment. This process is able to remove toxics by chemical reactions, in addition to conditioning the effluent mixture that will be treated in later processes.

The design of the treatment plants and the technologies employed in the process, aiming at the adequacy of treated effluent for disposal in the receiving body or reuse must be carried out with a very technical knowledge base, so that the investment is not in vain.

It is not uncommon to find inoperative or inefficient treatment stations, due to the lack of professionalism and lack of technical knowledge and experience of those who have dimensioned or implanted them. Currently there are appropriate technologies for the treatment of effluents, it is crucial to know how to design them.

There are several technologies for treatment of effluents, and it is possible to classify them into different groups: passive and intensive systems, biological or physico-chemical, compact or extensive, natural or mechanized are some of the possible divisions. In qualitative terms, we can affirm that all of them are suitable for the treatment of effluents, and it is not possible to segregate them between “good” and “more”. The best treatment technology will be the one that best matches the conditions and criteria of the socio-environmental, technical and economic application context.

Author of: Renildo Júnior de Sousa Alves
Chemical engineering student at UNIVERSITY CENTER OF PATOS DE MINAS (UNIPAM) – Patos de Minas