RU2094383C1 - Method of regenerating detergent solutions - Google Patents

Abstract

FIELD: detergent solutions. SUBSTANCE: invention relates to regeneration of exhausted detergent solutions containing petroleum products and suspended materials produced in the process of washing automobile and rail-way transport parts and aims at lessening technogenous environmental effect through waste waters when the same solution is repeatedly utilized. Regeneration method involves electrocoagulation with dissolving iron or aluminum anodes. Novelty consists in carrying out electrocoagulation in dynamic mode in which liquid being purified is pumped through between electrodes followed by separation of solid phase from solution, overall process being carried out in closed space wherein detergent solution is repeatedly passed through interelectrode gap until required purification degree is attained. EFFECT: improved environmental condition. 1 dwg , 1 tbl

Description

 The invention relates to methods for the regeneration of spent detergent solutions containing oil products and suspended solids generated during the washing of parts of automobile and railway vehicles, is intended to reduce the environmental impact through wastewater by reusing the same detergent solution.

 Currently, one of the environmental pollutants is the numerous small washing machines of a railway depot, machine and tractor fleet, and car washes, which, being unable to provide expensive wastewater treatment equipment from oil-containing effluents of enterprises, prefer to discharge them into open water or sewers.

 From the point of view of environmental ecology, given the sharp increase in the number of vehicles, this may become one of the main sources of wastewater pollution with irreversible consequences.

 A number of stringent requirements are imposed on modern local autonomous wastewater treatment systems. Firstly, such systems should ensure the quality of wastewater treatment, similar to stationary treatment facilities in terms of basic indicators and maximum permissible concentrations of contaminants in treated water. Secondly, these cleaning systems should be accessible from an economic point of view, which means that they can be really demanded by various small enterprises. Thirdly, the products of utilization should not be dangerous for the environment and humans during their subsequent destruction.

A known method of wastewater treatment from oils (ed. St. USSR N 709566, class C 02 F 1/46, 1980), including acidification of wastewater to a pH of 6.8-7.4, followed by settling for 15-20 minutes and electrocoagulation at a current density of 0.009-0.1 A / cm ² for 5-10 minutes

 This method is simple and affordable to implement even in small enterprises and can be fully automated. The quality of purification by the content of petroleum products is 10-20 mg / l.

 However, the known method has several significant disadvantages. Firstly, the content of oil products significantly (ten times) exceeds the maximum permissible concentration for discharge into the sewers or open water bodies. Secondly, the purified solution cannot be reused as a detergent, since salt content in it increases significantly after treatment, and detergents must be reintroduced into the solution, bringing its pH to 13-14.

 A known method of electrochemical wastewater treatment using coagulants obtained by dissolving iron or aluminum anodes (Scientific Works of the Academy of Public Utilities named after KD Panfilov, N 5, issue 12, 1969, S. 64).

 The method is simple and affordable, however, a significant drawback of this method is the clogging of the interelectrode space, especially with heavily contaminated washing solutions, which reduces the cleaning effect due to the voltage drop across the electrodes.

 In addition, for the subsequent purification of the liquid from flakes of metal hydroxide with sorbed impurities on them, a long settling is required.

 The purpose of the proposed method for the regeneration of washing solutions to address these disadvantages.

 This is achieved by the fact that in the method of regeneration of washing solutions, including electrocoagulation when dissolving iron or aluminum anodes, electrocoagulation is carried out in a dynamic mode, in the flow of the liquid being pumped between the electrodes, followed by separation of the solid phase from the solution, while the whole process is carried out in a closed volume with by repeatedly passing the washing solution through the interelectrode space until the required degree of solution cleaning is achieved.

 Carrying out the process of cleaning the washing solution from oil-containing products and suspended solids in the electrocoagulation mode with dissolved anodes allows cleaning by means available for any small enterprise, since this only requires a source of electricity and anodes from improvised material (aluminum or iron). There is also no need for any expensive reagents.

 Due to the fact that the process of electrocoagulation takes place in a dynamic mode, coagulation products are carried out by a rapid fluid flow from the reaction zone and there is no contamination of the interelectrode space, in contrast to the stationary mode of electrocoagulation. After leaving the coagulation zone, the reaction products are separated from the solution, and the remaining solution is again fed into the electrocoagulation zone. The cleaning rate of the washing solution is determined by the rate of separation of the solid phase. The easiest to implement are the deposition systems in which, under the action of gravity, the solution separates from the precipitate.

 To intensify the process of separation of the solid phase, filter systems can be used, for example, with the loading of filters with sand.

 For maximum acceleration of the process of separation of the solid phase, the flotation process can be used.

 The necessary degree of purification is achieved due to the multiplicity of the processing process.

 A significant advantage of the proposed method is the preservation of the pH of the initial solution, which not only does not require the introduction of additional reagents that increase the salt content of the washing solution, but also retains its washing properties after regeneration, and this is important to increase the economic efficiency of the method.

 Thus, the implementation of the proposed method has no analogues among the methods of regeneration of washing solutions, and therefore meets the criterion of "inventive step".

 The drawing shows a diagram of the implementation of the proposed method (1 - working capacity with spent detergent solution 2; 3 electrocoagulator; 4 - chamber for separating the solid phase; 5 purified solution; 6 solid precipitate; 7 circulation system).

 The method of regeneration of the washing solution is as follows.

 The spent solution 2 from the tank 1 passes between the aluminum or iron electrodes of the electrocoagulator 3, is saturated with metal hydroxides adsorbing oil products and fine suspension, and enters the chamber 4 to separate the solid phase 6. The purified solution 5 using the solution circulation system 7 after the first the cleaning cycle is recycled to tank 1, the treatment cycle is carried out again until the required degree of cleaning is achieved.

Example. As the spent washing solution was used a solution from the washing machine MMD-12 from washing parts of railway vehicles with an oil content of 9305 mg / l and suspended solids of 24180 mg / l. A capacity of 5.6 liters with vertical plates of iron with a gap between the electrodes of 5 mm was used as an electrocoagulator. The current density at the electrodes is 1 A / dm ² . The rate of passage of the solution through the electrocoagulator is 10.2 l / min.

 The results of cleaning the washing solution according to the treatment cycles are shown in the table.

 It can be seen from the table that, as a result of a four-cycle cycle of the washing solution, the oil content decreased from 9305 mg / l to 0.2, and the amount of suspended particles from 24180 mg / l to 6.0. After this treatment, the treated solution corresponds to the maximum permissible concentration for discharge into the sewer.

 If the purified solution is again used as a detergent, the degree of its purification can be limited to only 2-3 cycles.

 Thus, the claimed method of regeneration of the washing solution, providing the necessary degree of cleaning solution, which is available for implementation in almost any conditions and does not require special expensive equipment.

Claims (4)

 1. The method of regeneration of washing solutions, including electrocoagulation when dissolving iron or aluminum anodes, characterized in that the entire cleaning process is carried out cyclically in a closed circulating volume by passing the washing solution between the electrodes with continuous separation of the solid phase, and the number of cycles is determined by the degree of solution cleaning.  2. The method according to claim 1, characterized in that the separation of the solid phase from the solution is carried out by its deposition.  3. The method according to claim 1, characterized in that the separation of the solid phase from the solution is carried out by filtering it.  4. The method according to claim 1, characterized in that the separation of the solid phase from the solution is carried out by flotation.

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