HU217325B - Method for recycling communal sludges - Google Patents

Abstract

The present invention relates to a method for utilizing stone sludge sludge. The process involves mixing 100 parts by weight of sludge with a moisture content of between 20 and 45 wt. - 20 parts by weight of zeolite, and evenly spread on the surface of the ground, 0.1 to 0.3 parts by weight of Bacillus megateri, is put in a prism and matured for 60-90 days under constant dressing. ŕ

Description

The present invention relates to a process for the utilization of municipal sewage sludge.

Deposition of municipal sewage sludge, due to the high volume of sludge generated, is a very serious problem.

Significant organic matter content in the sludge should be utilized, but contaminants in the sewage sludge, such as heavy metals or phosphates from surfactants in the sewage, should be prevented.

Sewage sludge, due to its valuable organic matter content, is best used for soil improvement, such as sand soil and crop enhancers.

Hungarian Patent No. 192,591 proposes a solution for the agricultural utilization of mineral oil-containing sewage sludge.

The process involves spreading the sewage sludge on matured organic fertilizer and then adding a mixture of fertilizer, rhyolite tuff and milk powder. The mixture is stirred and matured under aerobic conditions and at a given humidity (40-50% RH).

The bacteria in the soil then spontaneously degrade the mineral oil derivatives.

According to another Hungarian patent, Hungarian Patent No. 174,531, soil contaminated with mineral oil is directly inoculated with bacterial cultures. Municipal sewage sludge contains no petroleum derivatives, but the presence of heavy metals and non-degradable phosphate compounds is a problem.

Our aim is to develop a method for the agricultural utilization of municipal sewage sludge.

In our experiments we have found that the sewage sludge must be treated with a special adsorbent and a special bacterium that results in phosphate decomposition.

Bacillus megaterium is a suitable bacterium for this purpose.

So far, according to our knowledge, soil improvement can be achieved by adding rhyolite tuff to the sewage sludge.

However, in our experiments we found that the amount of phosphate decomposition in the sewage sludge inoculated with Bacillus megaterium, and the binding of heavy metal content, and thus the soil improvement by mixing the sewage sludge with rhyolite tuff alone is inappropriate.

However, a solution is to disperse the Bacillus megaterium on the surface of a special carrier which also serves as an excellent adsorbent. We have found that a mixture of ground rhyolite tuff and ground bauxite is excellent for this purpose.

The presence of milled bauxite greatly increased the adsorbent effect, while the milled rhyolite tuffite mixture also enhanced the phosphate degradation efficiency of Bacillus megaterium.

If desired, this effect can be enhanced by the addition of zeolite to the rhyolite tuffabauxite mixture.

The present invention therefore relates to a process for the utilization of municipal sewage sludge.

The process is characterized by mixing 100 parts by weight of dewatered municipal sewage sludge with a moisture content of 20-45% by weight with 10-30 parts by weight of a mixture of 70-95 parts by weight of ground rhyolite tuff, 5-30 parts by weight of bauxite and optionally 5-20 parts by weight of zeolite. and consisting in a medium of 0.1-0.3 parts by weight of Bacillus megaterium medium, evenly distributed on the surface of the flour, then the homogenized mixture is placed in a prism and matured for 60-90 days with constant irrigation.

The experimental results show that the soil improvers produced according to the invention should be mixed in the following amounts in the soil, preferably in the upper soil layer, in the case of field crops 20-30 t / ha, grapes, apples, other fruits 70 t / ha, seedlings, 20 kg / pit for ornamental trees, 30-40 t / ha for replanting before grassland planting.

The size of the prisms is preferably as follows: height 60-70 cm, width 200-250 cm.

The prisms were watered with a 20-25 mm water layer and repeated twice a week.

Advantages of the soil improvement mixture according to the invention are as follows:

- Supports the soil's need for organic matter.

- The fertilizer demand of the soil so treated is reduced.

- The heavy metal content of the soil remains unchanged or does not increase.

- The phosphorus content of soils sold by plants is increasing.

- The average yield of arable crops planted in the soils so treated does not increase with the accumulation of harmful substances such as heavy metals.

The following examples illustrate the process of the invention.

Example 1

Bacillus megaterium was grown on a medium containing 1000 ml broth, 10 g peptone, 5 g NaCl, 5 g yeast extract and 5 g glucose, and the pH of the medium was adjusted to pH 6.8 with Na ₂ CO ₃ . in.

The following medium containing Bacillus megaterium contains 2 · 10 ¹⁰ bacteria per liter.

From the municipal sewage we settle the sludge by settling. This is transported to a digestion tower where the resulting biogas is discharged and the slurry containing 5 to 8% by weight of dry matter is dried in a sludge basin.

The 40% moisture by weight slurry is then transported to ground basins. Meanwhile, 100 parts by weight of ground rhyolite tuff and 20 parts by weight of ground bauxite are mixed in a mixer. The mixture was spread on trays and sprayed with 0.3 parts by weight of the Bacillus megaterium solution prepared above.

HU 217 325 A

100 parts by weight of the dewatered sludge in the ground basin are mixed with 25 parts by weight of the above spray mixture.

From the homogenized mixture, prisms 65 cm high and 220 cm wide are built on which water is sprayed to a thickness of 20 mm.

The prisms are aged for 80 days and watered twice a week as described above.

During this time, the bacteria in the prisms multiply and the phosphate is degraded.

The prisms are dismantled and the soil improvers are transported to the field. The mixture water content of ⁰ to 35 wt / ».

The soil improvement mixture is applied to the topsoil at a dose of 45 t / ha.

Example 2

In each case, the procedure of Example 1 was followed, but 10 parts by weight of ground zeolite were also added to the ground rhyolite tuff bauxite mixture.

Further, 15 parts by weight of a sprayed mixture of Bacillus megaterium are added to 100 parts by weight of a 30% by weight dehydrated sludge.

The maturation is carried out in prisms for 90 days.

The soil improvement mixture is used at a dose of 70 t / ha for the cultivation of garden plants.

Example 3

Examined with the soil improvers of Example 1, the analysis gave the following result.

heavy metal content of treated soil at a depth of 0-60 cm. 30 Values are in ppm.

The soil was a humusy sandy soil on sandy bedrock. It has a lime content of 5.6% by weight and a pH of 7.38.

T oxic element content ppm (average) pb 9.7 Co 5.4 Dig 10.2 Ni 12.2 cr 5.0

As a control experiment, sewage sludge without bacterial rhyolite tuffauxite mixture was mixed into the soil in equal amounts.

The measured heavy metal content of the soil showed an average increase of 30%.

Further, the possible accumulation of heavy metals and toxic elements in silage sunflower grown on treated soil was measured.

The following limit values are known for toxic elements:

CD < 0.5 ppm pb < 5.0 ppm Dig < 2.0 ppm hg < 0.1 ppm

During the experiments, silage sunflower grown on a parcel treated with the soil improvement mixture of Example 1

Treatment Cu Zn Mn CD B Ni cr 1 12.86 33.67 17.36 0,045 20.04 0.58 0.59 2 12.08 34.87 16.40 <0.04 22.63 0.66 0.35 3 13.06 33.49 14,73 0.062 14,16 0.69 0.58 4 15.77 41.90 15.34 <0.04 16.63 0.60 0.49 Average 13.63 35.98 15.95 0,047 18.35 0.63 0.50 Pb = <0.500 Co = <0.07 Mo = <0.09 As = <0.1 Se = <0.8 Uniformly for all treatments.

The results show that there is no or no significant accumulation of toxic elements in the plant, the values are far below the allowable limit.

In contrast, yields increased by 20%.

Claims (2)

PATENT CLAIMS A process for the utilization of municipal sewage sludge, characterized in that the dewatered municipal sewage sludge has a moisture content of 20-45% by weight. 100 parts by weight are mixed with 10 to 30 parts by weight of a mixture of 70 to 95 parts by weight of ground rhyolite tuff, 5 to 30 parts by weight of bauxite and optionally 5 to 20 parts by weight of zeolite and evenly distributed over the surface of 0.1 to 0.3 parts by weight From Bacillus megaterium medium 50, then the homogenized mixture is placed in a prism and matured for 60-90 days with constant irrigation. The method of claim 1, wherein the culture medium containing Bacillus megaterium contains from 1 to 10 parts by weight of 10 ^{9 to} 3 ^{9 9} bacteria.