HU198897B - Process for production of mud for compostation - Google Patents

Abstract

The process according to the invention is characterized in that the denitrification bacteria present in sludge and / or organic matter are promoted by the addition of an organic reducing agent, preferably methanol, and the nitrogen content of the sludge is reduced after the sludge is thickened but dehydrated. EN 198897 Scope of description B.4: .3 pages without drawing -1-

Description

The present invention relates to a process for the preparation of composting materials from sewage sludge and / or organic matter of various origins, in particular from municipal sewage sludge, by adding a reducing agent, preferably methanol, to the sludge after compaction, but in any case before dewatering.

It is known that the disposal and utilization of sludge from wastewater treatment plants worldwide is not a satisfactory solution. In many cases, the sludge, once it has been dewatered as far as possible, is deposited in storage sites, occupying land and losing its reusable materials to society. In other embodiments, organic matter of various origins is added to the sludge and composted. Many solutions are known, such as mixing with household, household rubbish, and other materials of agricultural and / or natural origin, e.g. straw, etc.

The large amount of material added is necessary for the smooth and good quality of the composting process, which is mainly determined by the amount of carbon needed for the nitrogen in the sewage sludge.

The basic problem with sewage sludge treatment is that the carbon-to-nitrogen ratio should be set to a specific ratio.

According to Hungarian Patent No. 177,689, straw is added to the sewage sludge to adjust the carbon to nitrogen ratio, and the material is rotated during the composting process,

According to Hungarian Patent Application No. 187,195, the carbon: nitrogen ratio is adjusted to 35-40: 1 by the addition of carbonaceous wastes and an aeration system is used.

According to page 504 of Benedek-Wallo's pocketbook of Water Purification and Wastewater Treatment (1976, Bp. Technical Publisher), denitrifying bacteria use the oxygen of nitrate for their metabolism and release nitrogen gas. This process also requires the addition of a carbon source and is recommended at the above ratio.

According to European Patent Application No. 099 052, organic fertilizers are mixed with clay minerals, composting bacteria and plant growth promoters. No. 2,571,717. According to the disclosure document of the Federal Republic of Germany, dewatered sewage sludge of industrial origin is given carbohydrates to provide favorable conditions for composting microorganisms.

Prior art processes have necessitated the addition of large quantities of carbonaceous sources, resulting in so much treated sludge that it is difficult to dispose of.

It is an object of the present invention to reduce the amount of organic matter containing carbon to be added to the sludge. This allows us to dispose of the sludge with a minimum of material and to ensure the least amount of sewage compost can be disposed of.

The realization of the object of the present invention has been achieved by the discovery that the amount of organic material to be added may be independent of the nitrogen content condition. This can be achieved by adding an organic reducing agent, preferably methanol, to the sludge treatment process.

According to the invention, as a phase of the wastewater treatment technology, excess sludge from the purification process is prepared for composting before dewatering as follows:

- To improve the unfavorable C / N ratio, we do not add C directly into the system, but reduce the N content. Partial nitrogen removal is done by denitrifying bacteria. To reduce denitrifying bacteria, add a reducing agent, e.g. methanol, but can also be ethanol, vinasse, etc.

The reducing agent does not increase the carbon content of the sludge, but indirectly reduces the N content, even though the reducing agent itself contains carbon. The solution is based on the principle that the amount of carbon added to the chemical can be absorbed into the body by the denitrifying bacteria, which can digest the nitrate in the sludge, producing nitrogen gas at the deep end. This gas is removed from the sludge. Based on this principle, the C / N ratio (min. 30: 1) required for composting is set at a lower absolute value of the elements compared to the known methods.

Preferably, the organic reducing agent is added continuously and the slurry is mixed cyclically or continuously.

Thus, according to the invention, the growth of denitrifying bacteria present in the sludge and / or organic material after thickening of the sludge but before dewatering is promoted by the addition of an organic reducing agent, preferably methanol, and the nitrogen content of the sludge is reduced.

Preferably, the reducing agent is methanol, the preferred amount being 25-150 mg per liter of wastewater.

The reducing agent provides the carbon source necessary for the biological activity of the denitrifying bacteria. In this way, the appropriate carbon to nitrogen ratio does not occur by adding large amounts of carbon but by reducing the nitrogen content.

The invention is illustrated by way of example.

-2HU 198897 B

Example

The sewage sludge is concentrated by gravity or on a stick press and its dry matter content is increased to 3-5%. Prior to mechanical dewatering, the slurry is transferred to a buffer and homogenizer pit, where methanol (150 mg / liter) is added. The slurry is stirred periodically and allowed to stand. In addition to homogenizing the chemical being added, stirring also helps to reduce accumulated nitrogen. The treated sludge is then dewatered, preferably on a vacuum filter bed, where nitrogen reduction is complete.

The composting slurry thus obtained has a C / N ratio of 32: 1.

Claims (2)

PATENT CLAIMS A process for the production of composting sludge, characterized in that the sludge is concentrated After 5 but before dewatering, the growth of denitrifying bacteria in the sludge and / or organic matter is promoted by the addition of an organic reducing agent, preferably melanol, and the nitrogen content of the sludge is reduced. 2. A process according to claim 1, wherein the methanol is added to the sludge in an amount of 25-150 mg / l of nitrogen (sludge). Process according to claim 1 or 2, characterized in that the methanol is added continuously and the slurry is mixed cyclically.