Liquid purification or separation – Processes – Making an insoluble substance or accreting suspended...
Reexamination Certificate
2000-11-14
2003-05-27
Hruskoci, Peter A. (Department: 1724)
Liquid purification or separation
Processes
Making an insoluble substance or accreting suspended...
C071S011000, C071S012000, C071S042000, C071S901000, C210S717000, C210S721000, C210S723000, C210S726000, C210S738000, C210S747300, C210S759000, C210S906000, C210S912000, C405S128100, C405S128750
Reexamination Certificate
active
06569342
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a process for treating waters, such as standing and flowing waters and waste waters, soils, sediments and/or silts.
Water bodies, soils, sediments and/or silts always comprise a certain proportion of organic matter. Especially in the case of waters, that is to say both water bodies and waste waters, the organic compound content, inter alia, determines the water quality. The organic matter firstly increases the COD and BOD values and secondly leads in the course of time to the formation of detritus, that is to say to silting and, in the extreme case, to accretion.
High COD and BOD values mean that material is present which has a high oxygen demand and leads to oxygen deficit for the microorganisms and other forms of life, and finally to their dying off. The degraded material is present in the water as additional organic matter, for example as suspended particles, which is accompanied by a further decrease in water quality.
To prevent accretion in water bodies, in particular ponds, the silts formed must be mechanically removed at regular intervals. However, this mechanical removal of silts requires an adequate particle size. Suspended particles generally cannot be removed.
Also, the fouling of waters, soils, sediments and/or silts impairs the activity of the microorganisms living therein, which in turn leads to an interference in the natural equilibrium.
A further problem, especially in the case of inland water bodies, is the phosphate contents, which are responsible for eutrophication of water bodies. The reduction in phosphate concentration in eutrophied water bodies is generally the key to successful remediation, that is to say to improving the water quality and possibilities for use. Therefore, for more than two decades, attempts have been and are being made with varying degrees of success to decrease the phosphate concentration in particular in lakes and sewage treatment plant effluents. Established processes employ iron salts and aluminum salts as precipitants. Recent developments relate to the optimization of biological phosphate elimination and technical control of biogenic calcite precipitation and flushing lacustrine chalk deposits as potential methods of ecotechnological water body remediation.
The known processes for phosphate removal, however, have the disadvantage that the precipitation of phosphate proceeds only incompletely and is also sometimes technically complex. By adding Al compounds or Fe compounds, furthermore, aluminum ions and iron ions are also introduced into the water, which does not always have beneficial consequences on water quality.
From the prior art it is known to treat fouled water with a mixture of Ca(OH)
2
and H
2
O
2
. In processes of this type the existing phosphate is precipitated as calcium hydrogen phosphate, whose solubility product is highly dependent on the pH. An equilibrium state forms with the components present in the aqueous environment. In some cases, the hydrogen phosphate even redissolves. Such a process does not permit permanent mineral phosphate binding in the treated systems and does not ensure a balanced oxygen environment which can be tolerated by water organisms and sediment dwellers.
The object underlying the present invention is thus to provide a process for treating waters, soils, sediments and/or silts which enables organic matter which is present as silt or suspended matter to be degraded and thus to reduce the content of oxygen-consuming substances and simultaneously to improve the nitrification and enzyme activity of the microorganisms present.
A further object was to provide a process which enables phosphate to be removed from waters, soils, sediments and/or silts such that the phosphate content is decreased below the ecologically required maximum content and the phosphate is bound in such a manner that it is not re-released by the water by dissolution or leaching. A further object is to reduce the content of other pollutants present in such systems simultaneously with the phosphate elimination.
SUMMARY OF THE INVENTION
The present invention relates to a process for treating waters, such as standing and flowing waters and waste waters, soils, sediments and/or silts, characterized in that the waters or sediments are treated with alkaline earth metal peroxides.
Surprisingly, it has been found that by using alkaline earth metal peroxides for treating waters, soils, sediments and/or silts, the content of organic, matter which is present as silt or suspended matter, can be greatly reduced and the microbial degradation performance can also be promoted. It is assumed that when alkaline earth metal peroxides are added to waters, soils, sediments and/or silts a mineralization of the organic matter takes place, that is to say conversion of organic matter to inorganic matter. At the same time other harmful substances can be immobilized, for example if these are precipitated together with other solids. Experiments have found that odor and flavor substances are also degraded and nitrification is promoted.
In the treatment of phosphate-containing waters, soils, sediments and/or silts with alkaline earth metal peroxides, phosphate can be eliminated so excellently that the phosphate concentration is far below 30 &mgr;g of P/L after treatment. The currently available experimental results have found a decrease in orthophosphate concentration of 3.26 and 0.33 mg of P/L to 6 and 3 &mgr;g of P/L, respectively, within a very short time.
It has further been found that the pH of the system treated according to the invention increases in the alkaline region and elemental oxygen is released. This action must generally be assessed as positive in aquatic systems, since it counteracts the oxygen deficit due to oxygen-consuming degradation processes.
The advantage over biological phosphate elimination is the reliable elimination of the phosphate. The advantage over other chemical phosphate elimination processes is the high efficacy, that is to say the great reduction in orthophosphate concentration with relatively low use of alkaline earth metal peroxide used according to the invention. The inventive process can prevent development of algal mass and thus avoid the associated water body problems. The alkaline earth metal peroxide, used in equimolar amounts, can remove phosphate from the waters. In addition, the precipitation product is suitable as mineral fertilizer raw material and thus capable of being recycled.
After use of the inventive process, it is not necessary to remove any precipitated material from the waters or soils, sediments and/or silts, it can remain in the water or in the sediment. The precipitated material essentially consists of mineralized substances to which substances impairing water quality are also bound by absorption or else can be incorporated into the solid. The present process is therefore to be used advantageously, in particular in what are termed passive water treatment systems.
Alkaline earth metal peroxides have been previously used, inter alia, as additives in bread, in toothpastes, in the cosmetics industry and as oxygen donors in composting. Alkaline earth metal peroxides are obtained from aqueous alkaline earth metal hydroxide solutions and H
2
O
2
in a specific process. It is known that simple mixing of the hydroxide solutions and H
2
O
2
does not lead to alkaline earth metal peroxides, but only to the decomposition of the H
2
O
2
used.
When this process is used for waste water clean-up, there is additionally the advantage that, depending on the properties of the waste water, this may be cleaned up in a short time in a very simple single-stage process. This involves comparatively less outlay on equipment and is thus less costly.
It has been found that the inventive use of alkaline earth metal peroxides for treating water body sediments, silts and soils removes the phosphates as sparingly soluble compounds and permanently binds them, so that remobilization or leaching of the phosphates on contact with water is effectively suppressed.
The obse
Jakobson Gerald
Nowicki Stefan
Ulrich Kai-Uwe
Willuweit Thomas
Becker R W
Hruskoci Peter A.
R W Becker & Associates
Willuweit Thomas
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