Chemicals to treat wastewater
Sewage
Water participates in the industry in many different ways and in most cases essential in the production system. In the different industrial sectors are given many wet processes, which implies higher consumption of that item.
Some of the water supply is drawn from their own (wells) or the network of drinking water evaporates during the process and is lost, another percentage is in the product being manufactured, but a large percentage is generated as waste water.
Should be considered on the other hand semi water systems involving substantial flows. At this point we include the cooling of equipment and processes.
Industrial waste water
Classification of sub-sector industrial wastewater
The water resulting from all processes can be summarized in the following types:
- Industrial wastewater, as a result of the various stages of manufacture.
- Wastewater treated as urban health are the consequence of the population of workers involved in the processes.
- Water cooling circuits that are responsible for heat exchange equipment (presses, motors, cogeneration, ..) and coolant (water).
- Process waters.
The characteristics of each of these types of waters are very different from each other, resulting in very different and specific problems.
Production systems, points that originate wastewater
Industrial wastewater and process
Come from the production line cleaning, containers and reservoirs as well as cleaning of the machinery employed in various industrial process (milling drums, tanks agitation, reactors, etc. ...).
The main features and most important problems are the waters of this type are:
- Presence of heavy metals from the raw materials used in the manufacturing process, forming soluble cations or metal complexes. A major pollutant is boron, which is a regular feature in the composition of frits and glazes, detergents, etc ... and that in solution is presented as borate anion very soluble, it is impossible to remove with conventional treatments. So if you are in the waste water remains in contaminating aquifers.
- Organic solids and dissolved that is responsible for the occurrence of odors, foams and biomass. This organic matter comes from the cleaning of containers, tanks, agitation, reactors, etc ... It is responsible for increasing the chemical oxygen demand (COD). The decomposition of the organic matter producing odors and fouling or biomass inside the pipes leading to the proliferation of bacterial flora.
- Generating a large volume of sludge as a result of the treatment process, to be transported to the point of management.
This type of industrial waste waters are purified by physico-chemical procedure by decantation or flotation.
Sanitary wastewater
Arise as a consequence of the presence of workers in plants. They come from the toilets, showers, toilets and kitchens. This is comparable to urban water. They contain high concentrations of organic matter and nitrogen compounds.
Its purification process has nothing to do with industrial water and must be submitted to a biological treatment, to prepare them and to make a discharge under controlled conditions.
Cooling water circuit
These are a special section within the industry, since it is not sewage, but sometimes have water volumes and flow very important.
The use of water as cooling fluid is widely practiced in either a one-step systems or in systems and semi-closed. Water is considered the universal solvent because it solubilizes both a rock as the steel itself, in turn salt components present in the water can produce very significant changes in the behavior thereof.
Process water
Is the water that is reused in the manufacturing process. Its main function is to cool a process (such as grinding wheels or cutting saws). Like the cooling water circuit, are not considered sewage.
The main features are:
- High salinity caused by the continuous supply of salts from different processes.
- The high conductivity values ??do appear problems of corrosion and fouling on the machines and tubes, greatly reducing their average life.
In this type of water is essential to establish an adequate system of purges within the circuit to keep the salt content in appropriate values.
That is why the use of this liquid refrigerant is always accompanied corrective action on the quality of the same or about the effects of its use occurs on contact surfaces.
The water often causes problems of corrosion and / or scaling on process water systems, these problems are usually associated with the onset of fouling and biofouling, or what the proper water treatment should address all these aspects, for eliminate or reduce them to maximum effectiveness.
In any case the proposed treatments should always be accompanied by an effective system of drains to keep the salinity within adequate margins.
Industrial Wastewater Treatment
Treatment systems, sewage
Treatment systems, wastewater can be classified according to the traditional classification:
- Physico-chemical or primary: Roughing, coagulation, flocculation, sedimentation, flotation, etc. ..
- Biological or secondary treatment: biological fixed bed (percolaladores filters, rotating biological discs, ..) and mobile biological bed (conventional activated sludge, SBR, Membrane bioreactors ...).
- Tertiary treatments: Ion Exchange, treatment of membranes (reverse osmosis, microfiltration, ..), chemical oxidation, ultraviolet light treatments, treatments of ozonation, filtration bed, etc. ...
Chemical processes in the wastewater treatment
Decantation achieves efficient removal of pollutants from wastewater. Decantation is carried out in purification plants through application of chemical reagents and subsequent decantation under gravity or by flotation. This provides purified water for later use or disposal. The manufacture of these chemicals meet current legislation.
The general process for the chemical treatment of wastewater comprises:
- PH adjustment
- Coagulation
- Flocculation
Then we will see each process separately.
Chemicals for pH adjustment
The adjustment of pH is a very important physical-chemical treatment. The pH must be found in certain values ??for the process is optimal because:
- Favors the action of the coagulant-flocculant.
- It allows the precipitation of dissolved metals as hydroxides.
The optimum value, and depending on the coagulant used, should be between 6 and 8. A direct relationship between the pH values ??compared to the solubility of the metal hydroxides. So that the working pH should be selected depending on the presence of such metals. In general forms, at pH values ??between 7.5 to 8.5 such removal occurs by precipitation from water. Exceeding the maximum value of 8.5 may occur redissolution of the precipitated components.
As a reagent for pH adjustment is generally used water 50% sodium hydroxide, although it is also possible to use sodium hydroxide in other concentrations (25, 35%) or even other hydroxides, such as calcium hydroxide, etc. .. . The dosage is controlled by a pH probe connected to a dosing pump.
The pH meter has a pH of reference from which activates the pump for dosing the pH and the pH rises product. Once reached the predetermined pH value stop dosing. This process also comes with a homogenization system. It is desirable that the flow of the metering pump is medium or low to prevent large fluctuations in pH.
One of the major drawbacks of using 50% sodium hydroxide as a product to increase the pH is that it forms crystals on cold days.
- Soda crystals prevent proper dosing.
- The pumps stop working and break the suction and discharge pipes.
- The freezing of soda to 50% occurs below 8 ° C.
To avoid these problems has SERVYECO has a range of sodium hydroxide at different concentrations in order to lower the freezing point. It is also possible to surround the tanks with electric heaters that raise the temperature. Once the temperature rises, the soda does not lose its properties.
Clotting products
Coagulants have evolved over the ages. As coagulants used:
- Mineral inorganic salts of polyvalent cations. The most effective are trivalent, especially Fe (III) and Al (III).
- Synthetic coagulants new generation Polidacmacs, polyamines, etc ...
- Combination of inorganic salts with synthetic coagulants.
The fine particles or colloids in natural waters are generally negatively charged and in wastewater happens often the same. This is why they are used trivalent iron salts or aluminum, and electric charges which give the water and break the electrostatic equilibrium.
However these coagulants due to hydrolysis in water suffering modify the physical-chemical characteristics thereof, since it is highly acidic substances, which therefore alter the pH and increasing the conductivity salts incorporated. Therefore the pH correction is performed in the same reaction vessel to the coagulation process, thus establishing the necessary corrections.
Synthetic coagulants
Synthetic coagulants are based on the incorporation of organic components in their formulation, presenting many advantages and no disadvantages.
- Highly effective in its dosage form polymeric species due to stable, non-hydrolyzed, high cationic density can work with broader ranges of pH with an inorganic coagulant which does not affect it classic or alkalinity or temperature.
- High rate of coagulation. INSTANT therefore need not be a pre-dilution.
- Smaller volume of sludge produced, because the dosage is reduced greatly, leaving the more compressed and compact mud.
- Microfloculo produced larger of which is sometimes enough to decant in terms of installation variables, flow to be treated and the nature of the solids to settle.
The synthetic coagulants SINTEC series are products that have been developed as primary flocculants for water treatment residuals are free from sulphates products and processes designed primarily for physical separation by decantation chemical industries listed in the table below . These products are used in waters with high solids content and high turbidity.
Synthetic coagulants ECOMIX series are products which have been developed as primary flocculant for wastewater treatment, are chloride-free products, and designed for chemical processes physical separation by settling or flotation in industries which are detailed in the following table.
The synthetic coagulants ECOTEC series are products that have been developed exclusively for specific applications.
Natural plant coagulants/span>
The natural plant coagulants are formulated based on natural organic products. Because of its salt-free formulation, presenting numerous advantages and any inconvenience.
Natural coagulants ECOTAN BIO series are products that have been developed as primary coagulants for wastewater treatment. For more information, visit: natural plant coagulants.
Specific coagulants for the removal of fluoride
Fluoride does not exist in nature in its elemental form for your state, the diatomic molecule has a high reactivity and is almost always in combination. Because fluorine is the most electronegative element, is very reactive and forms compounds with virtually all other elements, reaching even to form compounds with noble gases such as xenon and radon. In the crust is in a concentration between 0.06 and 0.07% by weight, with the thirteenth element on the scale of abundance.
Inorganic compounds containing fluorine are extremely numerous. However, only three families Industrial products represent potential economically exploitable raw materials to industrial scale: natural cryolite (sodium aluminum fluoride), fluorite or fluorspar (calcium fluoride) and fluorapatite (calcium fluoro phosphate). The high presence of fluorine in many minerals and its leachate natural waters originates that 0.2 mg / L of fluoride ions, with the exception of rainwater. Note that sea water has concentrations between 1 and 1.4 mg / L.
The main industries generate fluoride in their effluents are those who use it in their processes, to name a few fine chemical products for air conditioners, metal processing, oil refining, carbon gasification combined cycle power plants, semiconductor electronics products for anesthesia (propellants), manufacturing of high performance batteries (lithium ion batteries), making glazes, frits and glass, among others.
Their extreme reactivity, mentioned above, makes the purification of such fluoride ions in the effluent is extremely complicated. One of the main techniques for flue-gas scrubbing is to make them react with calcium compounds, usually hydroxide, calcium fluoride obtained is collected in filter bags. This technique is similar to that used for the purification of effluents containing fluorides. However, it raises a number of drawbacks such as poor performance in total elimination of fluoride and generation of a bulky sludge and very fluffy, very difficult to compact.
To solve this problem, SERVYECO has developed a new innovative product, the ECOFLUOR, capable of removing fluoride present in the wastewater, reaching levels of over 95% efficiency. It also presents the advantage of producing a very compact sludge, treatable by decantation and subsequent filtration, thereby considerably reducing its volume.
The synthetic coagulants ECOFLUOR series are innovative products, being able to remove the fluoride present in industrial effluents, reaching levels above 95% efficiency. Also has the advantage of producing a very compact sludge and can be made later treated by decantation and filtration, thus reducing its volume considerably.
Coagulation process
Coagulation is a process of destabilization of the electrical charges of colloidal suspensions or colloidal suspensions. The colloids are kept in suspension causing turbidity, due to electrostatic repulsion between particles occurs in one direction, and that around each one of them generates an alternating electric charges generated ZETA potential.
Coagulation is composed of two phases:
- PHASE ONE: Destabilization. The charged particles superficially by deionization absorption bands and small molecular mass ions, balanced by counterions introduced by the coagulant. There are two layers: Stratum surface and diffuse layer. Zeta potential is the difference between the electric potential of the ion layer and the liquid.
- PHASE TWO: Adsorption. Destabilized particles are absorbed onto the ions introduced by the coagulant, producing the microfloculos.
It is necessary to break the zeta potential or the electrostatic repulsion. To break the Zeta potential, a reagent is added, that through aggregation mechanisms or adsorption, cancels the repulsive forces. To cancel the repulsive forces allows the aggregation of particles larger ones and it is this increased size which promotes the precipitation. This is the mode of operation of a coagulant.
Products flocculants
The products used are long chain macromolecules can have electric charges or ionizable group. According to the electric charge in the active group are classified as:
- Nonionic polyelectrolytes, especially polyacrylamides. Also known as flocculants are nonionic
- Anionic polyelectrolytes of high molecular weights, and exhibiting groups which allow adsorption and negatively ionized groups which cause the extension of the polymer. The most common are partially hydrolyzed polyacrylamides by soda. Are also known as anionic flocculants.
- Cationic polyelectrolytes with positively charged groups. Also known as cationic flocculants.
The way to present it in liquid (emulsions) or solid.
Prior to the application of these products make their preparation by dilution with water under stirring. The solutions are usually prepared at concentrations of 1 to 3 g / l in the case of solid products, and 2 to 6 g / l for liquid or emulsion flocculant.
Anionic Flocculant
The strong anionic flocculant range ECOPOL are products developed for the removal of suspended solids in industries such as chemicals, textiles, paints dry tanning, ceramics, etc ... These products are particularly suitable for water clarification where the separation process is carried out by decantation. Products are arranged in different ionic charges and different molecular weights depending on the characteristics of the water to be purified.
The anionic flocculant range ECOFUX liquid emulsion products are developed for the removal of suspended solids in industries such as chemicals, textiles, paints dry tanning, ceramics, specialmente These products are suitable for the clarification of waters where the separation process is carried out by decantation. Products are arranged in different ionic charges and different molecular weights depending on the characteristics of the water to be purified.
Cationic Flocculant
Solid cationic flocculants are ECOPOL range products developed for sludge dewatering. For centrifugal molecular weight flocculants high provide a high dewatering performance. Filter press for the low molecular weight flocculants prevent clogging of the fabric forming a floc smaller but still resilient, facilitating the pressing of the sludge.
Cationic flocculants high molecular weight are indicated for treatment where the separation must be accomplished by flotation, either by diffusion or by cavitation.
Crosslinked liquid cationic flocculants in the range ECOFUX are products developed for sludge dewatering centrifuge exclusively. The crosslinking can be a very strong floc able to withstand high centrifugal velociadad.
Flocculation process
The flocculation is the stage that is given below of coagulation and is produced by adsorption of polymers on the particle surface so that confer increased size and weight and enhances their decantation. The flocculation is related to the transport phenomena within the medium so that the particles make contact. The product flocculant causes the formation of bridges between two or more chemicals coagulated particles, so as to form a random three dimensional structure, spongy and porous. This structure, through the growth of coagulated particles, eventually forming a floc large enough and heavy (or light) to get settle (or float).
Additive sequence of chemical reagents
The application of the products described above can be performed on pipe, injected directly into the suction pump feeding the filter, in the order described above.
In this case be incorporated into the top of the pipe and the coagulant soda and later and separate from the above, the flocculant.
However the addition is more effective in tanks suitable homogenization. In the first, which will be sized slightly less than the second, pH-neutralizing added, and the coagulant, at this point is the pH meter which controls the dosage of the selected product to adjust the pH. In said tank is also an agitator that gets a correct homogenization of the products and water. It requires rapid agitation (above 100 rpm) for a short period of time (seconds).
In a second flocculant reservoir is incorporated, in this case is a minor agitation to avoid breakage of the flocs (below 100 rpm) and a longer residence time (minutes) obtained with a larger tank.
From this tank water flows into flocculation decanter. In this structure is to be produced in an efficient solid-liquid separation, gravity decanting the solid leading to the sludge, and water devoid of surface contaminants passing through a tank or pond where it is stored.
Other products used in wastewater treatment plants
Defoamers
During debugging, the appearance of foam is an unwanted side effect that causes the increased production time, making the debugging process.
The foam is formed by trapped air bubbles produced during the various stages of purification and agitation. The air-liquid interface of these bubbles is surrounded by the surfactants present in the water due to its low density migrate to the surface. During this process, small bubbles may be combined to form larger more rapidly rising.
To remove the foam stabilizing effects should avoid using an antifoam should have at least one of the following properties:
- be capable of destroying the foam to remove the existing
- be able to prevent the foam to prevent its formation
- be capable of releasing the air to facilitate the foam reaches the surface
The foaming action occurs mainly in the lamella stabilized. Therefore the antifoam should possess sufficient mobility that allows the lamella penetrate and move the surfactant present at their interface. The antifoam agent should have a surface tension lower than the surfactant.
Defoamers may be chemicals with a low surface tension as silicone and mineral oils, fatty acids and fluorocarbon compounds. The type of defoamer to be used depends on the nature of the system.
The Silicone Defoamers ADIFOAM series are easy to use. Defoamers are formulated based on synthetic surfactants art presented in emulsified form, free from mineral oils, making it particularly effective in a wide range of pH, salinity and temperatures up to 90 ° C.
Antifoams aliphatic hydrocarbon mixture series nonionic surfactants ADIFOAM and preventing the formation of foams.
And bacteriostatic algaecide
Because spores airborne algae can form in the wastewater treatment ponds or water accumulation layers of harmful algae and slippery. The algae are not only aesthetically displeasing, but also damage the installation. Over time, algae form a viscous layer, which can only with difficulty be penetrated with a high dosage antidotes.
Algicides based on quaternary ammonium act against all types of algae that may appear in the water. By the high content of active substances are effective even in small quantities. To live, the algae need light, nutrient substances (eg phosphates) and heat. All of this exists in abundance in the treated water rafts. With the addition of a regular and timely algaecide can be prevented from future growth of algae.
An algaecide prevention product attacks the metabolic processes of unicellular algae and prevents cell division. However, prophylaxis of algae only works when there is enough water in the active substance. Since new algicides are deposited in other organic particles, which then produces the so-called "clarifying effect", the content is continuously reduced algicide. Therefore, to secure protection against the growth of algae, it is necessary to periodically add the recommended amount.
If already formed algae, in most cases it is sufficient to add an algicide. In this case you have worked with a biocide.
Algicides BACTEROL series have been formulated to remove algae which are formed in treated waters stagnant, and can be applied continuously or shock dose.
Bacteriostatic products ECOBAC series products that inhibit the proliferation of bacteria. Its active ingredient is a mixture of terpenes.
Inhibitors of odor and bleaches
A sewage treatment plant because the raw material that is, sewage and waste arising has to live with the odors that emerge during treatment. First we must distinguish between odors outside the WWTP and those generated in the treatment itself. In general removing discharges of odorous substances with high potential, odors are generated from the degradation of organic matter in the absence of oxygen. The main products involved are derived from hydrogen sulfide and sulfur, ammonia, amines and VOCs.
Products Series MIRODOR ECOSULF and are designed for removing and masking odors especially sulfide derivatives.
The series products have Series ECOLOR designed to eliminate the significant presence of color when you need to remove it for disposal. Do not depend on the pH or alter it.
