Antifoaming agents for sewage water treatment

The use of water is necessary in many of the activities carried out by human beings and, often, in the processes in which it is used, waste is inevitably poured into the water, altering its composition hindering its later use or recycling and polluting the liquid with serious consequences for health and the environment. Sewage water treatment consists of a series of physical, chemical and biological processes that aim to eliminate the pollutants present in both industrial and urban effluents.

There are mainly 3 types of sewage water treatments: primary treatment or physical-chemical treatment, secondary treatment or biological treatment and tertiary treatment. Some consider a fourth type of treatment prior to the primary one that includes the preliminary stages for the correct processing of water.

The physical-chemical or primary treatment is carried out to reduce the elements suspended in the liquid by precipitation or by means of chemical oxidation and is of common application in purification of water of industrial origin. Among the most common methods of such treatment are flotation and coagulation-flocculation. When the matter suspended in water has a density less than or equal to that of water, such as oils, fats or emulsions that do not settle, the flotation method is applied, which consists of generating a large amount of air bubbles that will displace the suspended elements towards the surface, remaining concentrated and easily removable. If the size of the particles mixed with the water is very small and do not sediment or do it too slowly, the coagulation-flocculation process is used, which consists of adding chemical substances that cause the coagulation of the particles to be removed, favouring their flocculation and sedimentation. Other options to eliminate harmful substances from sewage water are precipitation, ion exchange and UV treatment.

The biological or secondary treatment is often applied, not necessarily, after physical-chemical treatments and makes use of microorganisms that are responsible for actively degrading the organic matter or biological content so that the elements to be eliminated are released from the aqueous medium. Two different processes are distinguished depending on whether we treat the matter with oxidants or not, the aerobic and the anaerobic processes. The first one incorporates aerobic microorganisms whose objective is to increase the oxygen content in the liquid by means of irrigation of solid surfaces, agitation and submerged aeration. In this treatment the dissolved biodegradable substances serve as food to the incorporated microorganisms becoming biomass of aerobic conditions, carbon dioxide and water. Next, the removal of nitrogenous compounds from the water that is being treated through nitrification and denitrification is carried out. Nitrification uses microorganisms to convert ammonium from sewage water into nitrates, denitrification reduces nitrate to nitrogen, allowing the product to escape into the atmosphere in a gaseous state. On the other hand, anaerobic processes, also considered fermentative or degrading, are characterized by converting the organic matter processed into methane compounds and carbon dioxide through bacteria that are responsible for the degradation of the solids that reach this stage. In this treatment there is no compound based on oxidants, so the chemical reactions resulting from these processes release a small part of the energy while the remaining energy remains in the methane compound.

Finally the tertiary treatment is carried out, which may be of a physical-chemical or biological nature, and to refine the result of the composition of the effluent the methods applied will be very variable depending on the origin and destination of the water to be treated.

In all the aforementioned treatments the formation of foam in the liquid is common, by agitation of the medium in hydraulic or mechanical processes as well as by intentional aeration. If out of control, said foam can generate irregularities in the processes as well as damage the machinery used or produce alterations in the biological purification systems increasing the associated costs and decreasing the productivity of the processes. For this reason it is necessary to incorporate auxiliary agents in the processes known as antifoaming agents.

Antifoaming agents, or defoamers, are chemical products that allow to control and, if necessary, remove foam in treated water to avoid the negative consequences of its appearance or excess in stages in which it is not desired. Defoamers contain surfactants that allow the control of the surface tension of liquids. They quickly diffuse at the liquid-gas interface to destabilize micellar structures, favouring the collapse of bubbles.

Antifoaming agents for water treatment may be necessary in very diverse industrial sectors. Their composition and formulation will depend on the processes to which the water is subjected and the physical-chemical or biological treatments used with agitation or aeration, biological reactors, catch basins and collectors, distillation and vacuum systems, etc. The selection of each chemical will depend on the surfactants present in the water, the engineering and the water quality required.

Concentrol is a chemical company with a long track record and experience in multiple industrial sectors that has developed the EMULTROL DFM antifoaming range that includes solutions designed specifically for the treatment of sewage water in different industrial sectors. The wide range of sectors in which we work provides an extensive knowledge of the nature of water and engineering of water treatment processes in most industries. Thus, Concentrol’s technical team works together with the experts of each industry to learn in depth the specific requirements in order to provide the solution that best suits the needs, optimizing the costs and the desired result.

The range of EMULTROL DFM defoamers is formulated based on mineral oils, vegetable oils or silicones. They have a high percentage of active material being very effective in the control of foam with very small dosages. Their antifoaming and defoaming efficacy is applicable in both physical-chemical and biological treatments, being compatible in a wide range of pH. The quality of the defoamers and the technical support to configure each solution according to the particularities of each client lead to achieving a correct operation of the facilities, optimizing the processes with the economic benefit derived from that.

Concentrol’s extensive track record and experience in additives for sewage water treatment enable the possibility of offering personalized solutions for each client based on tests, studies and piloting in their laboratories. Contact us for more information.