Experiment application of technology for cleaning industrial sewage

A.N. Zolotnikov, A.A. Fomin
Mediana-Eco, Moscow, Russia
 
Qualitative and quantitative composition of industrial waste water is various and depends on the type of production, technological process, quality and form of the used raw materials, etc. Every year, in Russia more than 50 (fifty) million m3 (cubic metre)  waste water discarded in the surface water systems in to discard, from them more than 60 % falls at waste water of industrial enterprises. The high pollution of the water sources and ineffective technology of the water treatment are the basic reasons for the unsatisfactory quality of the drinking water. From total volume of waste water, entering through the municipal networks to surface water systems, and more than 90% are discarded by those contaminated. [1]
It is obvious that to the quality of the water an effect has the substances which are found in the water in different concentrations and the phase states. Excess concentration of many of them can have a negative effect both to the man and to the biological situation in the natural reservoir (basin). And so it is necessary to pay considerable attention to the extraction of pollutants.
The pollution, which present in the waste water can be divided into the inorganic and organic compounds and also it is possible to classify according to their phase state in the solution. In according to see pollution it is possible to determine the basic methods of the purification of industrial waste water.
Methods of the purification of industrial waste waters:
1.      Mechanical: settling and precipitation, cleaning in the sand cones, filtration, micro-filtration and other.
2.      Chemical: oxidation, restoration, neutralization, precipitation, complexing.
3.      Physical chemistry: coagulation, flocculation, flotation and electroflotation, ion exchange, absorption, extraction, distillation, freezing, electrocoagulation, electrolysis, ultra and nano-filtration, reverse osmosis.
4.      Physical: magnetic working, ultrasonic working, vibration, pulsation, ionizes the irradiation.
5.      Biochemical: the fields of filtration, biological ponds, aeration and anaerobic tanks, trickling filters and oxidizing channels.
The selection optimal flow charts of cleaning industrial waste waters it is complex problem caused by the variety of admixture and by the high demands, presented to the quality of the expendable water.
Today there are specific types of equipment for the cleaning waste waters which in most cases are working out a different problems. For example, the sumps are used for the deposition or settling, different separators, centrifuge are used for the separation of suspensions, bioreactors are used for processing of the organic compounds.
For industrial waste water of some types of the productions appeared (there were) already the standard solutions with the identical collection of equipment, which is characterized only by productivity. However, taking into account a constant stiffening of the requirements the presented to the quality to waste water of industrial enterprises the standard collection of equipment it is not always sufficient for the solution of problem in complex. On the enterprises is in many instances established the equipment for waste water treatment removing the basic pollution, are worked out by methods and ways. But the part of the pollution to defy on cleaning and remains in the conditionally- purified water. Quite often many enterprises reconcile to an existing problem and prefer to pay payments or fines. Introduction of perspective and innovation technologies in standard solutions are often working out a different problems of entire technological chain as a whole, and also give the chance of the purified waste waters. Requirements to quality of water for a reuse as a rule very high. The content of small impurity, hard to remove from the waste water at the expense of their good solubility it does not allow to use water repeatedly. Application of membrane technologies helps to solve the given problems. A variety of membrane technologies beginning from the microfiltration and finishing the reverse osmosis, can provide at necessary stages of a technological line of waste water treatment, achievement of desirable results with a high probability.
The concrete example can be resulted on one of the projects of our company. The project on cleaning of drains from the section of etching of glass of one glass factories.
The main causative substance in sewage from section of etching of glass is fluoric acid and products of process of etching. Special complexity of a drain was made by its structure used for reception of dull glass. Except the high maintenance of fluoric acid at sewage also there were salts of barium, sodium and ammonium. The principal pollutants were fluorides to 10g/l and ions of ammonium to 2.5 g/l. Requirements to the cleared water ordered concentration of fluorides  no more than 0.3 mg/l and no more 16 mg/l of ions of ammonium.
 For working out of the technology guaranteeing the effective decision of a problem, laboratory researches on the basis of research laboratory Mendeleev university of chemical technology have been spent. As a result of tests the technology of processing bath drain, including some stages has been developed. This technology basis on chemical binding  of the dissolved fluorides by calcium ions was necessary. Calcium fluoride, insoluble in water as a result turns out. Surplus of ions of ammonium leaves by blow-off of ammonium at high values . Long time of contact provides the greatest possible binding of ions of fluorine. As a result after processing of sewage by calcium the residual maintenance of ions of fluorine at level of 10-15 mg/l has been received. The given concentration did not satisfy with the requirement on concentration of fluorine in the cleared water. For finishing of demanded indicators to the specification it has been decided to use every possible innovative technologies. First of all have been tested ion-exchange technologies. Use of an ionic exchange has not brought expected result. Water with high content of salt was released from fluorides to the minimum concentration of 0.6 mg/l. In this case, filtrocircle of ion-exchange installations were irrationally small. For the problem decision has been offered a membrane way on the basis of the reverse of osmosis. Recycling osmosis installation represents the high-pressure two-stage construction with high selective membrane elements. On an exit from installation residual concentration of fluorides has made less than 0.3 mg/l and ions of ammonium no more than 2 mg/l. Use of such installation has allowed to solve a problem not only with fluorides, but also to receive the water, satisfying to quality for a reuse. In the industrial performance the technological plan has taken the following form.
-    At the first stage after averaging, the drain moves in a reactor of mixture with calcium. After a reactor the stream passes a neutralisation stage where holding time make it possible to pass the reactions of the binding of fluorides most fully.
-    At the following stage, after preliminary processing of coagulant the drain arrives in the camera of the flocculation, from where it will be given to the station of dehydration, presented by dewatering press. The filtrate from dewatering press moves on the further clearing, and the wrung out deposit on recycling. Along the way into the dewatering press the drain is processed by flocculant for an improvement in the department of sediment. Filtrate from the dehydrator will be given for further cleaning, and filter cake to the utilization.
-    The filtrate moves at first on mechanical clearing in a hydro cyclone. The clarified part moves on the further filtration, and the sludge from a hydro cyclone comes back in the camera of the flocculation.
-    The clarified flow, after traversing the pressure filters of mechanical cleaning, moves to the reverse  osmosis for deep clearing. The concentrate from reverse osmosis returns to the head of the treatment plant.
  For a constructive embodiment of technology was developed a number of the innovation solutions, which do not have analogs in the world today. It is exclusive because of the use of a membrane method it became possible of obtaining the required parameters.
In conclusion it is possible to tell the following. The list of dangerous and other polluting substances is defined on the basis of the list of substances, characteristic for the given kind of economic and other activity and used technological processes, taking into account the analysis of negative influence of technological processes and by results of laboratory researches of quality of entering the systems of canalization and dumped water.
In this connection it should be noted that in accordance with the federal law from 27.12.2002 184 On the technical regulation are established required requirements for the safety of production, processes of production, operation, storage, transportation, realization and utilization in the form of the technical regulations, which find the force of law. In the number of these requirements are provided for required technical measures for providing of safety of industrial effluents for the man and the environment. Thus, during working out and coming into force of technical regulations it is necessary to expect really achievable safety requirements, including to structure of waste water of the enterprises of various industries. [3]
In process of introduction of new effective technologies of production and perfection of processes of the waste water treatment, the mentioned requirements gradually will become more and more rigid at preservation of technical possibility of their achievement by each enterprise.
 
The list of literature
 
[1] O.A.Trifonova. (2006). Sewage treatment by a method of pressure head flotation.
Ecology of production, page 42.
[2] V.A.Kolesnikov, . V.Menshutina. (2005). Analysis, designing of technologies and the equipment for industrial sewage. Publishing house Deli print, Moscow.
[3] V.Kvashnin. (2008). Features of assignment of industrial sewage in city systems of the water drain. Ecology of production, pages 36-39. 
 
 

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