MX2007010311A - Treatment of highly contaminated waters with hydrocarbons. - Google Patents

Abstract

It is depicted a new application for treatment of polluted residual waters with hydrocarbons specifically, with residual waters of washing car businesses. The advantages of the present invention over those of further state-of-the-art systems are that it has a competitive cost, provides satisfactory results regarding the removal of suspended solids, there is no need for a drastic adjustment of the pH, thus respecting the CONAGUA standards and do not increase the amount of ions dissolved in the treated water. The process is characterised in that it consists in the following steps: a) preparing flocculant and coagulant dissolutions; b) preparing the water to be treated in order to reduce the pH thereof to approx. 6.5 by adding a HCI solution at a concentration of 1 mol; c) adding the flocculant and coagulant solutions to the water to be treated; d) stirring the combination resulting from the step c) for 1 minute at 100 RPM; e) reducing the stirring speed down to 30 RPM and maintaining it for 10 minutes; f) allowing the generated floccules to be sedimented and filtrating the same.

Description

ECONOMIC TREATMENT OF HIGHLY CONTAMINATED WATER WITH HYDROCARBONS FIELD OF THE INVENTION The present invention is related to the contaminated water treatment industry, more specifically, to the water treatment industry contaminated with hydrocarbons, such as those generated by the car washes.

BACKGROUND OF THE INVENTION Chitosan is a non-toxic, biodegradable and biocompatible polymer. In recent years, chitin polymers, and especially chitosan, have received a lot of attention as a renewable material because of their wide applications in the pharmaceutical and biomedical industries in the immobilization and purification of enzymes. In wastewater treatment plants and in the food industry as thickeners, gelatants and stabilizers. (Knorr, 1984).

The use of chitosan in wastewater treatment should be in the presence of a free amino group that contributes to the properties such as polycationic flocculant, chelating agent and dispersants, with an easy solubility in dilute acetic or hydrochloric acid. When the amine is protonated, a positive charge is generated that allows interaction with organic compounds present in wastewater, thereby reducing the turbidity of the treated water (No and Meyers, 1992). The treatment of the residual water with the chitosan produces a stable and compact floccule, allowing an easy recovery of the water. Asano et al. (1978) found that chitosan is very efficient for conditioning industrial and municipal sludge mainly due to its rapid biodegradability and economic advantages.

It is known from the state of the art that there are several processes with different for the treatment of contaminated water, there are even processes in which chitosan is used as a flocculant, but the application of this flocculant presents a series of situations that need to be saved to be able to go to the market. Especially in such problematic situations as the wastewater treatment of the car washes.

In view of the concern to meet the needs of a project that will attack the consumption of water treated in the car washes with the use of a polymer that has certain properties capable of rendering the waste water reusable (for example, treated water). gives more fats, dirt, etc.) that discard said establishments, this polymer is chitosan. However, this material is very expensive so a water treatment process that uses it will have serious disadvantages with respect to other processes.

In the previous patent application of the same inventor and applicant of the present one it was determined that using only quito-sano, a removal of the suspended solids exceeding 95% was achieved, with sedimentation times of 10-15 min and formation of large, mechanically resistant flocs. The doses in those cases were in the range of 150-250 ppm.

According to our previous water treatment process, containing only chitosan, it generated water of very good quality, producing compact and stable flocs, easily filterable. However, the problem of the cost of chitosan, due to its high doses, Depending on the quality of the water, chitosan is used in relatively high doses, especially if the water contains organic compounds of the hydrocarbon type, for example generated in the car washes. The turbidities of the water coming from the washing of chassis and motors can reach values as high as 3500 NTU (nephelometric turbidity units) and, therefore, to, require high doses. The price of this product at an international level has been increasing rapidly, which does not favor its use in this industry.

Petr and D or I inska [The 2005 Younger Euro pean Chemists' With faith -renceHighlights of European Chemistry Research and R &D] have used these salts to eliminate the humic substances present as decomposition products of organic products in the soil and in the Water, used iron and aluminum sulfates at pH between 5 and 7 and compared them with the effect of chitosan. The sludge generated with this last coagulant has been able to be biodegraded and minimized the problem of its treatment. When the iron and aluminum salts are used, the sludge is contaminated with residues of these metals, making it difficult to recover any valuable product.

Borovickova et al used a previous coagulation with aluminum and iron salts and subsequent treatment with chitosan from wastewater and drinking water with good characteristics of suspended solids removal. Marcela Borovickova borovickova@fch.vutbr.cz Brno 2005 The Use of Chitosan for Coagulation and Flocculation in Potable and Waste Waters Shon et al (ls semi-flocculation effective as pretreatment to utraf i Imation in wastewater treatment? Shon HK, Vignes-waran S, Ngo HH, Ben Aim R Water Res, 2005 Jan, 39 (1), 147) They used ferric chloride in a flocculation treatment as a pre-treatment to ultrafiltration to remove organic matter from synthetic waters. High doses of F e C 13 (> 500 mgl-1) were necessary to obtain a greater elimination of the organic solids.

Bratskaya (Method of drinking water treatment using chitosan based floc-culation compositions) proposed a method for water treatment using a primary coagulation method with inorganic compounds and the use of chitosan, with a mixture of these components (including antibacterial components) in different proportions, depending on the composition of the water. This mixture produced good quality water at low cost, Cheng et al. (1995) studied the coagulation mechanism using aluminum sulfate, a cationic polymer and ferric chloride. They found two main mechanisms of coagulation: At a relatively high dose of coagulant and high pH, the adsorption of the particles predominates in the aluminum hydroxide or ferric hydroxide flocculation, while at low doses and low pH's, the mechanism predominant is by neutralization of charges forming insoluble complexes.

Jong and collaborators (Decolorization of reactive dyes using inorganic coagulants and synthetic polvmer by Duk Joo, Won Sik Shin, Jeong-Hak Choi, Sang June Choi, Myung-Chul Kim, Myung Ho Han, Tae Wook Ha, Young-Hun Kim (pp. 59-64).) Carried out a coagulation-flocculation process for the treatment of waste water with high dye content. A polymeric flocculant synthesized from cyanoguanidine and formaldehyde was used under acidic conditions with an inorganic coagulant (alumina or ferric salts). The inorganic coagulant (1 g / L) could only remove 20% of the color, but with the help of the polymer almost 100% of the dye was removed depending mainly on the polymer dose.

Many processes of the prior art require a significant change in the pH when using inorganic coagulants, since due to their reaction with water they produce sulfuric acid or hydrochloric acid respectively, which lowers the pH to values lower than those indicated in the standard issued by CONAGUA for treated water, which establishes that these waters must have between 5.5 and 10 as pH.

OBJECTIVES OF THE INVENTION One of the objects of the present invention is to achieve a process of water treatment of competitive cost with the processes of the state of the art with good results in the removal of the suspended solids.

Another objective is to achieve this process without requiring significant changes in the pH of the water to respect the CONAGUA standards.

Still another objective was to determine this procedure without increasing the amount of dissolved ions in the treated water.

And all those objectives that will become apparent with the present description and the annexes included.

BRIEF DESCRIPTION OF THE INVENTION In a few words, the present invention consists of a water treatment process in which two effect mechanisms are combined in the suspended particles. On the one hand, a physicochemical mechanism of coagulation is applied, accompanied by a physical-chemical mechanism of locution.

Pollutants are considered as those parameters or compounds that, in certain concentrations, can produce negative effects on human health and the environment, damage hydraulic infrastructure or inhibit wastewater treatment processes.

The maximum permissible limits for pollutants from wastewater discharges to urban or municipal sewerage systems, should not be higher for the case of fats and oils at 50 ppm (average monthly value) and the allowable pH range (hydrogen potential) in wastewater discharges it is 10 (ten) and 5.5 (five point five) units, determining for each of the simple samples.

For all the above, the water that is generated in the self-washes can not be drained (according to Mexican Standard 002-1997), therefore the contaminants that this water has dispersed must be eliminated, so it is necessary to have water treatment systems for this type of waste. Generally, in these self-washes there are traps that allow, by density difference, to mechanically eliminate surface fats. However, fats emulsified by the presence of surfactants (soap used in the process) are not eliminated. There is a process known as electro-flotation, through which fats are also eliminated, but it is expensive and requires a special infrastructure.

For a better understanding of the invention, a detailed description will be made of some of the modalities thereof, shown in the examples that are annexed to the present description with non-limiting illustrative purposes.

DETAILED DESCRIPTION OF THE INVENTION For the determination of the process object of the present description a series of experiments was carried out that are narrated next.

Samples of water from a car wash were treated where they also wash the engines and chassis. The initial turboths of this water were between 800 and 2000 NTU.

All the solutions used were prepared at 2% and the samples were one liter for jar tests.

These combinations between the polymer and the salts were tested in different types of water, that is, water was obtained from different days to observe the different characteristics of these, since they vary according to the number and type of services performed per day, as well as the type of detergents and / or substances required for these services.

First of all, the water of the autowash was adjusted to a pH of 6, 6.5 or 7 since initially the water had a pH between 9 and 10, with a conductivity between 1280 and 1528 μe and turbidity of 765 or more NTU. The substances in different proportions were added to observe their efficiency.

The combinations that presented the best results are shown in Table I, with the different output parameters. The speed and sedimentation time were determined, which for both combinations of the iron salts flocculated in 1m minutes. The tests were carried out three times to observe the quality of the flocculum by considering its sedimentation rate and that it was sufficiently resistant. The tests were repetitive confirming the mechanical stability of the same and also the amount of suspended solids removed during flocculation, obtained by filtration and drying at constant weight, as shown in Table I.

Table I. Results of the combinations of chitosan and ferric sulfate chitosan and ferric chloride Table I. Results of the combinations of chitosan and ferric sulfate In Table I we observed that there is a considerable impact in terms of pH as it decreases at high concentrations of sulfate or ferric chloride, however the final turbidity if it is below 10 NTU, so it was decided that the pH to which the water of the carwash would be adjusted should be between 6.5 and 7 and not 6 as previously worked.

Under these conditions, removals greater than 95% with pH greater than 5.6 were achieved Table II. Jar test data with a volume of 1 liter. Chemicals uses Chitosan FeCl3 * (g) Fe2 (S04) 3 * (g) two Total sludge 1.4531 1.3991 1.3267 generated (g)% removal 99.77% 99.59 98.98% recovery 93.12% 96.25 93.75 of treated water For the 225 ppm doses of the ferric salts and 50 ppm of quito-sano.

EXAMPLES EXAMPLE 1 The chitosan was dissolved in a 0.1 M HCl solution at a concentration of 20 g / l and a solution of ferric chloride was prepared by dissolving it in water at a concentration of 20 g / 1. The chitosan solution was added in a concentration of 25 g / l. ppm and 225 ppm of FeCh to a water obtained from a car wash agency, with a turbidity of 610 NTU, an initial pH of 9.33 and acidified with 1 M HCl solution to a pH of 6.5 and at room temperature. It was stirred at 100 RPM for 1 minute and at 30 RPM for 10 minutes. After 10 minutes of sedimentation, there was an efficiency of flocculation of 99.9% when the water had a final turbidity of 0.69 NTU. The formation of flocs is less than 1 minute. The sedimentation rate of them was high enough and in less than 10 minutes the flocs generated are sedimented. The amount of mud removed was 1.4 g / L, which were filtered on Whatman type paper number 41 EXAMPLE 2 The chitosan was dissolved in a 0.1 M HCl solution at a concentration of 20 g / l and a solution of ferric sulfate was prepared by dissolving it in water at a concentration of 20 g / l. The solution of chitosan in a concentration of 50 ppm and 225 ppm of Fe2 (S0) 3 was added to a guide obtained from an autowashing agency, with a turbidity of 610 NTU, an initial pH of 9.33 and acidified with solution 1 M HCl until a pH of 6.5 and at room temperature. It was stirred at 100 RPM for 1 minute and at 30 RPM for 10 minutes. After 10 minutes of sedimentation, a flocculation efficiency of 99.5% was obtained when the water had a final turbidity of 4 NTU. The formation of flocs is less than 1 minute. The sedimentation rate of them was high enough and in less than 10 minutes the flocs generated are sedimented.

The amount of mud removed was 1.4 g / L, which were filtered on Whatman type paper number 41 The invention has been sufficiently described so that a person with average skill in the art can reproduce and obtain the results that we mentioned in the present invention. However, any person skilled in the art field of the present invention may be able to make modifications not described in the present application, however, if for the application of these modifications in a certain process or in a particular solution, the matter claimed in the following claims is required, said processes and solutions should be understood within the scope of the invention.

Claims (7)

R E I V I N D I C A C I O N S Having sufficiently described the invention, the content of the following claim clauses is claimed as property.

1. Process of treatment of waters heavily contaminated with hydrocarbons, of the type that are generated in the car washes, characterized by consisting of the following steps: a) preparation of flocculant and coagulant solutions; b) preparation of the water to be treated to reduce the pH to around 6.5, adding an HCl solution at a concentration of 1 molar; c) add flocculant and coagulant solutions to the prepared water; d) keeping the combination resulting from step c) stirred for one minute at 100 RPM; e) d i s m i n u i r the agitation speed up to 30 RPM and keep it for 10 minutes; f) allow the flocs to settle and filter.

2. Process of treatment of waters heavily contaminated with hydrocarbons, as claimed in the preceding claim, further characterized in that the flocculant solution of step a) is chitosan in a concentration of 20 g / 1.

3. Process of treatment of waters heavily contaminated with hydrocarbons, as claimed in claim 1 or 2, further characterized in that the dissolution of the coagulant of step a) is ferric chloride at a concentration of 20 g / 1.

4. Process of treatment of waters heavily contaminated with hydrocarbons, as claimed in claim 1 or 2, further characterized in that the dissolution of the coagulant of step a) is ferric sulfate in a concentration of 20 g / 1.

5. Process of treatment of waters heavily contaminated with hydrocarbons, as claimed in any of claims 1 to 4, also characterized in that in step c) the amount of dissolved flocculant solution is such that the concentration of chitosan in the water to try is between 25 and 50ppm.

6. Process of treatment of waters heavily contaminated with hydrocarbons, as claimed in any of claims 1 to 5, also characterized in that in step c) the amount of aggregate coagulant solution is such that the concentration of ferric sulfate in the water to be treated is between 225 and 750ppm.

7. Process of treatment of waters heavily contaminated with hydrocarbons, as claimed in any of claims 1 to 5, characterized also in that in step c) the amount of dissolved coagulant solution is such that the concentration of ferric chloride in the water to be treated is between 125 and 375ppm. SUMMARY The present invention is related to the contaminated water treatment industry, more specifically, to the industry of treatment of water polluted with hydrocarbons, such as those generated by the car washes. The advantages of the present process with respect to those of the state of the art, lie in that our is carried out at a competitive cost, with good results in the removal of suspended solids; It does not require major modifications in the pH of the water to respect CONAGUA standards and does not increase the amount of dissolved ions in the treated water. The process is characterized because it consists of the following steps: a) preparation of flocculant and coagulant solutions; b) preparation of the water to be treated to reduce the pH to around 6.5, adding an HCl solution at a concentration of 1 molar; c) add flocculant and coagulant solutions to the prepared water; d) keeping the combination resulting from step c) stirred for one minute at 100 RPM; e) decrease the agitation speed to 30 RPM and maintain it for 10 minutes; f) let the generated ones settle and filter.