DD238035B5 - Process for the purification of waste water - Google Patents

Description

Field of application of the invention

The invention relates to a method for the purification of wastewater using lignite fly ash (BFA), which is applicable to waste water from industry, agriculture and from the municipal area.

Characteristic of the known technical solutions

It has already been described a variety of methods for wastewater treatment. Depending on the type of wastewater and the required degree of purity, certain cleaning methods are preferred.

An essential method of purifying waters whose constituents are present in colloidal distribution is the coagulation, flocculation, precipitation and subsequent mechanical separation of the pollutants. This is usually done in settling pits, settling tanks or settling lakes with the addition of flocculants such. As water-soluble polymers, aluminum and iron salts, etc.

It is also known that fly ash or pretreated fly ash is used as a coagulating and flocculating agent.

Although flocculation and precipitation are more economical than most other processes, but for the very lengthy sedimentation process and the large surface area of the plants, a high expenditure on equipment for conveying, circulating and discharging the wastewater is needed.

Of particular importance is the question of neutralizing polluted sewage sludge. In the interests of hygiene and cleanliness of the groundwater, questions of profitability of this process have not yet been put in the foreground, but due to the high energy expenditure, efforts are increasingly being made for cost and energy-efficient processes.

So far, the thick sludge (especially chemical wastewater) had to be dewatered, dried and burned due to its low digestibility with high equipment and energy costs.

DD-WP 120590 describes a process in which hydrophobic organic substances, in particular oils and / or fats, containing industrial effluents with the help of electrostatic precipitator ash with a Feinkorhanteil less than 0.09 mm of at least 50 wt .-% are cleaned. When using electrostatic filter ash with a hydrolyzable lime content of more than 10% (calculated as CaO), a strong bottom body results. Although this method is quite economical, it also achieves a nearly 100% de-oiling of the wastewater, but it still has some disadvantages. Thus, the process is limited to oil and greasy wastewater, for the execution of agitator or cascades are required, the separation of H ₂ O and sediment is carried out by filtration, and the bottom body is only cheap to transport, if the recovery or deposition point no larger Routes are to be mastered. So falls z. As the combustible soil body at an oil and / or fat content about 15% in the wastewater in the form of an oily paste, which can be difficult to transport to a remote recovery point.

Object of the invention

It is the object of the invention to develop a process for the purification of wastewater using the waste lignite fly ash, which is to be realized with extremely low technical effort for a wide range of waste water containing waste and leaves a well transportable waste product.

Explanation of the essence of the invention The technical problem which is solved by the invention

It is an object of the invention to develop a process for the purification of wastewater by sedimentation of the ingredients with brown coal fly ash, which is largely feasible with existing technical means and ensures transport and / or recovery of Sedimentationsschlämme cost clean and hygienic way.

Features of the invention

The object of the invention is achieved in that waste waters containing both dissolved colloidal, fine and coarse floating components by means of conveyors such. B. screw conveyor or conveyor belt lignite fly ash (BFA) is added continuously before they get into the receiving water.

By the z. B. turbulent flow achieved on steep slopes, the BFA is intimately mixed with the wastewater. Thereafter, the wastewater stream enters a rest basin or a rest container.

As a result of the addition of ash, a faster settling of the colloidal and other suspended particles together with the ash is achieved by the already known effects of agglomeration and coagulation. When sedimentation has precipitated thin sludge, it is continuously withdrawn simultaneously with the purified, waste-free effluent. The thin sludge is directed into a thickening basin. There a chemical and physical reaction of the BfA sets in, which causes the thin sludge thickening not by protracted water evaporation, but by hydration of the gypsum portion of the BFA and hydration of their hydraulic components. This thickening process takes about 24 hours. Thereafter, the thickened sludge of BFA and sewage ballast is fed to a forced-flow mixer (eg, concrete-rotor mixer), and dry BFA is added by a conveyor (eg, cement screw conveyor) during rotation of the mixing-stirring tools. This results in granules in spherical shape, but with different sizes, but which plays no role for landfill purposes.

With coarser ashes or coarser precipitated suspended particles it does not come to the spherical shape, but it creates only a free-flowing dry mass.

The granulation process and thus the addition of BFA is complete when no more bonds occur in the mixer interior and on the mixer coulters and the mixer itself cleans itself when emptying without foreign intervention. The same applies to the conveyors. The bulk material is now either transported to landfill or for further utilization. During transport or on landfill, the granules continue to harden, which contributes to the fact that the angle of repose and the trafficability are also protected at high tipping. The proposed method has the following advantages over the previously described methods for wastewater treatment:

- Many different types of wastewater can be purified in the manner described, such. As industrial (including oil-contaminated) wastewater and acidic, pulverized, fatty acid-containing and also municipal as well as industriemuellhaltige wastewater;

- There are completely freed from suspended wastewater;

- the constantly fluctuating concentration of dietary fiber in the effluents, as well as the varying composition of the ash, can be easily compensated for by varying the dose of BFA; This makes it possible to precipitate even weakly polluted wastewater; Wastewater with a very high pollutant and ballast concentration can be completely bound with lignite fly ash and fed to a dry landfill;

- the physical and chemical water-binding capacity of the BFA is optimally exploited by its application to two processes, thickening and granulation, consuming only as much ash as is necessary for both processes;

- In addition to the purification process by coagulation and agglomeration also runs a chemical precipitation reaction by the use of BFA, namely the precipitation of fatty acids to sparingly soluble calcium soaps and sulfate ions to only slightly soluble calcium sulfates, which also contributes to wastewater treatment; mixing with BFA leads, in addition to the purification of the effluents, if they represent an acidic medium, also to their neutralization;

- When mixing charcoal-containing BFA with fatty acid-containing, pulverized coal and other waste water with an increased content of organic substances resulting in masses that can be supplied to combustion plants; Industrial waste, too, when granulated with the thick sludge, leads to caloric masses;

- The easily manageable form of the waste products allows their utilization for other than combustion purposes, so arise in the purification of a number of municipal wastewater by the method described granules, which can be used as lime-nitrogen fertilizer;

- the transport costs for BFA are considerably reduced, since the ash producer and the wastewater ejector are mostly located close to each other, but a clean, non-hazardous transport of the waste products is also possible if required.

embodiment

The invention will be explained in more detail below by means of an example (FIG. 1). The various wastewaters z. B. 1,2,3 are brought together in a mixing trough 4. By a steep slope, a high flow rate is achieved, so that the supplied with a cement conveyor screw 5 BFA 6 intimately with the wastewater

is mixed.

This mixture enters the sedimentation tank 7, where in addition to the cleaned of suspended solids to be pumped or overflowed wastewater 8 thin sludge 9. This is constantly pumped into the thickening tank 10. From there, the thick sludge 11 is continuously and / or periodically (basin acts as a buffer storage) conveyed into the concrete rotor mixer 12 and

granulated with BFA 6 13.

With a conveyor belt 14, the transport of the granules takes place for landfill or for further utilization. During transport or landfill, the granules continue to harden.

The partition wall 15 serves to separate the floating coal particles, which are always contained in the ash, and to pump it into the thickening basin.

List of reference signs

(different J wastewater

4 mixing trough

5 cement conveyor screw

6 lignite fly ash

7 sedimentation tanks

8 cleaned wastewaters

9 thin sludge 10 thickening tank

11 thick mud

12 concrete rotary mixers

13 granules

14 conveyor belt

15 partition wall

Claims (1)

Invention claim: Process for the purification of waste water by coagulation, agglomeration and sedimentation of suspended particles with the addition of brown coal fly ash by intimate mixing, characterized in that the thin sludge resulting from the sedimentation withdrawn continuously and simultaneously with the purified wastewater, passed into a thickening basin, there by the chemical water binding capacity the lignite fly ash thickened, the thick sludge continuously and / or periodically withdrawn and fed into a forced mixing mixer and transformed by further addition of lignite fly ash into a free-flowing mass. For this 1 page drawing