RU2293070C2 - Method of complex processing and utilization of waste water sediments - Google Patents

Abstract

FIELD: processing of waste water sediments in public water purification works.

SUBSTANCE: proposed method consists in preliminary dehydration of sediments of primary settlers and activated sludge, mixing with sand taken from sand traps, decontamination by means of reagent, thus obtaining utilization product by means of additional decontamination of sediments with the aid of decontaminant in form of complex powder reagent of the following composition, mass-%: clay, 40.0-60.0; lime, 5.0-40.0; cement, 5.0-40.0; complexing agent selected from the following series: mixture of metal oxides, ash, crushed slag, dolomite flour, ground limestone, 5.0-10.0. Amount of reagent is 10.0-30,0 mass-% of mass of mixture.

EFFECT: enhanced efficiency of processing and decontamination of sediments; possibility of obtaining ecologically pure utilization products.

3 cl, 4 tbl, 2 ex

Description

The invention relates to the field of processing sewage sludge generated in municipal wastewater treatment plants, and is intended to provide waste-free technology for the disposal of processed products.

Sewage sludge from a municipal wastewater treatment plant (WWTP) is a complex mixture with a high water content, in which biologically harmless substances are firmly bound to polluting toxic components of an organic and inorganic nature.

There are various methods of processing WWTP sludge, partially solving the problems of their neutralization and processing with subsequent disposal of the resulting substances.

The most common methods for the disposal of sewage sludge through the manufacture of fuel or through pyrolysis.

A known method of disposal of sludge from biological wastewater treatment plants to obtain fuel after mixing the filtered sludge with 40-50 wt.% Coal dust, or sawdust, or shavings, or peat (FR No. 2497520, C 10 L 5/46, 5 / 48, 1982).

A known method of processing wastewater treatment plants to obtain fuel or additives to compost, in which the sediment is mixed with flocculants and carbon carriers and subjected to dehydration to achieve a dry matter ratio of 15-20% (EP No. 0271628, C 10 L 5/40, 1988).

Similar methods for the disposal of wastewater treatment plants include the method for producing molded fuel based on a mixture of condensed sludge from sewage treatment plants and a dried mixture of ground solid fuel selected from the group consisting of wood and vegetable wastes, peat, lignin, coal fines, textile wastes, or mixtures thereof (RU No. 2131449, C 10 L 5/14, 5/44, 5/46, 5/48, 1999).

However, all of these methods only partially solve the problem of utilizing WWTP and reducing environmental pollution by waste, as they cannot be used for the disposal of wastes containing toxic substances.

There are also known methods of disposal of sludge from wastewater treatment plants to obtain a sorbent after mixing the sludge with peat and calcination (Utilization of sludge from biological wastewater treatment. Water supply and sanitary equipment, 1965, No. 5, pp. 10-11) and a method based on the introduction into processed activated sludge of crushed expanded clay before pyrolysis to increase the efficiency of the resulting sorbent (SU No. 1742227, C 02 F 11/00, 1990).

The formation of toxic gases in the pyrolysis process, as well as the presence of heavy metals in the resulting sorbents are significant disadvantages of these methods, which prevents their widespread use.

There is a method of complex processing of technogenic precipitation, in particular WWTP, providing for the separation of precipitation into fractions, followed by treatment of each fraction separately and obtaining the target utilized products. First, the sandy component of the sediment is separated, then, depending on the ratio of organic and inorganic substances, the sludge component of the sediment is divided into fractions and their separate processing is carried out. Treatment with sulfuric acid allows the preparation of a coagulant from the precipitate. Pyrolysis and activation of the precipitate ensure its processing into a sorbent, with a high content of organics, the precipitate is subjected to biotechnological decomposition (RU No. 2057777, C 02 F 11/10, C 02 F 11/14, 1996).

The disadvantages of this method include the uncertainty of the criteria for the separation of the silt component into fractions depending on the ratio of the content of organic and inorganic substances and the methods for their separation, as well as the declarative nature of obtaining a "clean" sand component after undergoing treatment on a drum screen or in a hydrocyclone. This is explained by the fact that in the autogenous films contained in the sand particles, organic and inorganic contaminants are sorbed, which cannot be completely removed by the indicated treatment. In addition, the pyrolysis of one of the fractions of the sludge component requires sophisticated technological equipment for the purification of smoke emissions, and the treatment of the other fraction with sulfuric acid is hazardous, costly, and requires special corrosion-resistant equipment. Based on the foregoing, we can conclude that it is possible to use the known method only for cleaning bottom sediments of rivers and lakes and the impossibility of using it for complex processing and disposal of sewage sludge from WWTP.

The closest to the present invention is a method for the treatment of sewage sludge, in which the sediment of primary sedimentation tanks and activated sludge after preliminary dehydration are mixed with filler material with sand and a disinfecting reagent, additionally dehydrated to a product with 60% humidity and disposed of as fertilizer (SU No. 842057, С 02 F 11/006 1981). This method, according to the authors, provides the processing of all waste generated on WWTP: sludge, excess activated sludge, sand. However, in addition to the indicated types of wastewater treatment plants, the authors do not take into account superlattice wastes consisting of solid large-sized inclusions, which also need to be disposed of. Moreover, in the case of the content of toxic organic and inorganic substances in sewage sludge, this method of disposal is not applicable. The use of thiazone or ammonia water as a disinfecting reagent increases the cost of operations and makes the disposal products environmentally unsafe, that is, the waste is decontaminated, but not neutralized.

The task to which the creation of the invention is directed is a deep integrated processing of sewage sludge, ensuring their neutralization, disinfection and disposal with the receipt of environmentally friendly products.

The problem is solved in that in a method for the integrated processing and disposal of sewage sludge, including preliminary dewatering of sludge from primary sedimentation tanks and activated sludge, mixing with sand and a disinfecting reagent, and obtaining a disposal product, according to the invention, decontamination of sewage sludge is carried out simultaneously with the decontamination powder reagent of the following composition: clay 40.0-60.0 wt.%, lime 5.0-40.0 wt.%, cement 5.0-40.0 wt.%, complexing agent selected from the range: a mixture of metal oxides, ash, crushed slag, dolomite flour, ground limestone 5.0-10.0 wt.%, and the amount of reagent is 10.0-30.0 wt.% by weight of the mixture, the specified reagent, dehydrated sedimentation of primary sedimentation tanks and activated sludge is fed into the mixer at the same time as sand from sand traps and, in addition, with pre-ground superlattice wastes of primary settlers, where they are processed until a homogeneous mixture is obtained, which is placed in a storage hopper.

To obtain technogenic fortified soil, the amount of powder reagent can be 20.0-30.0 wt.%, With clay content of 40.0-50.0 wt.%, Lime 5.0-20.0 wt.%, Cement 30.0-40.0 wt.%, Complexing agents, which are selected as metal oxides, or ash, or crushed slag 5.0-10.0 wt.%.

To obtain a technogenic soil, the amount of reagent can be 10.0-15.0 wt.%, With clay content of 40.0-50.0 wt.%, Lime 20.0-40.0 wt.%, Cement 5, 0-10.0 wt.%, Complexing agent, which can be selected dolomite flour or ground limestone - 5.0-10.0 wt.%, The exposure time in the storage hopper can be at least 24 hours, after which the mixture is additionally injected with a leaching additive in the form of plant soil, in a ratio of 1.0: 0.4 to 1.0: 0.6, or peat, in a ratio of 1.0: 0.15 to 1.0: 0.25 .

The applicant has not identified sources of information containing information about technical solutions identical to the claimed invention, which allows us to conclude that it meets the criterion of "novelty."

The use of the proposed reagent in the method of complex processing and utilization of wastewater treatment plants provides not only disinfection, but also the neutralization of all components of sewage sludge.

It is known that sludge sediments and excess activated sludge in large quantities contain various microorganisms, including pathogens. Their amount is estimated by the total protein content, for example, by the Bradford method (Quantitative effect of the vital activity of microorganisms on the physicomechanical properties of gley rocks. Guidelines, Leningrad, Leningrad State University, 1988) and can range from 100 to 300 mg / g dry matter. With the introduction of the proposed reagent, the reaction of the medium in the mixture of wastewater from CBS varies from pH 6.0-6.5 to pH 11.0-12.0. Under the indicated sharply alkaline conditions, alkaline hydrolysis of fats, protein membranes of microorganisms and hydrocarbons results in the saponification of these substances, the death of microorganisms and the formation of sodium, potassium and calcium salts of organic acids.

At the same time, the present invention provides for the neutralization of WWTP sediments from various ecotoxicants, primarily heavy metals and their toxic complexes. This is achieved through the formation of an aluminosilicate sorption-active mineral matrix formed during the interaction of alkaline components of the reagent (lime, cement) with clay, the amount of which in the reagent can be 40.0-60.0 wt.%. The specified number of clay aluminosilicates provides a fairly complete course of chemisorption processes. With a decrease in clay content in the reagent of less than 40.0 wt.%, The amount of aluminosilicates may be insufficient for reliable interaction with dispersed components of activated sludge, while an increase in clay content is irrational, due to the fact that it leads to a decrease in the share of hydrolyzing components and complexing agents, thereby reducing most effective hydrolysis reactions. The introduction of lime into the composition of the reagent provides, first of all, a highly alkaline reaction of the medium in the mixture of sediment components and overcoming their acid buffering. Therefore, the consumption of lime in the production of anthropogenic soil is selected from the conditions for ensuring the reaction of the medium pH 11.0-12.0, that is, cannot be less than 20 wt.%, Since the amount of powder reagent in this case is less than in the production of reinforced anthropogenic soil. In addition, lime, interacting with hydrolyzed clay aluminosilicates, participates in the formation of cementing or aggregating neoplasms in the form of hydrosilicates, aluminates, calcium ferrites, and facilitates the lithification of colloidal dispersed components of the mixture. The introduction of a complexing agent into the reagent provides an intensification of the processes of neoplasms, which have an astringent ability and hydro-character of the formed organo-mineral aggregates. The choice of a specific complexing agent is determined by the type of final disposal product. So, to obtain technogenic hardened soil, metal oxides, ash or crushed slag can be used as a complexing agent, and its share should be at least 10.0 wt.%, While to obtain technogenic soil, the share of complexing agent can be 5.0 wt. % and in this capacity they already use dolomite flour or ground limestone, which are environmentally friendly components.

The proposed method also provides for the disposal of fragmented and crushed superlattice wastes, which perform the function of a reinforcing fraction or coarse aggregate component in the production of man-made fortified soil, which contributes to aeration in the production of man-made soil.

The introduction of contaminated sand from the sand traps into the mixer together with other processed components of the sludge and reagent also ensures its disinfection and neutralization, while the sand acts as an inert skeletal additive, useful for all types of disposal products.

The exposure time of the homogeneous mixture of the components of precipitation of WWTP and powder reagent obtained in the mixer during the preparation of technogenic fortified soil is not regulated, that is, the resulting mixture can be used for its production immediately after unloading. And in the production of man-made soil, exposure to the mixture in the storage hopper is necessary for the complete implementation of the processes of neutralization and disinfection in a highly alkaline environment. At the same time, not earlier than one day later, it is recommended to add a leaching additive in the form of natural plant soil in a ratio of 1.0: 0.4 to 1.0: 0.6, or peat, in a ratio of 1.0 to the prepared mixture of technogenic soil. : 0.15 to 1.0: 0.25.

These circumstances, according to the applicant, confirm the conformity of the claimed technical solution with the criterion of "inventive step".

The feasibility of the invention is confirmed by experiments and is illustrated by the following examples.

Example 1

In this example, we consider the implementation of the invention to obtain a reinforced man-made soil. According to SNiP 2.04.03-85, the weight ratio of the WWTP components located at the treatment plant has the following composition (in fractions of a unit):

- 75% sludge dehydrated to moisture content and excessively activated sludge - 0.9;

- sand from sand traps with a moisture content of 10-12% - 0.09;

- crushed to particles less than 5 mm oversize waste with a moisture content of 25.0% - 0.01.

The mixture of WWTP of the specified composition prepared in a batch mixer of the VSML (2 × 100) grade had a viscous-flowing consistency, and after adding a powder reagent of the following composition: clay - 45.0%, cement - 30.0%, lime - 15, 0%, complexing agent (ash) - 10.0%, the mixture acquired a refractory state suitable for forming samples. Samples of fortified industrial soil were made with the introduction of a complex powder reagent in an amount of 10.0; 20.0; 30.0; 40.0 wt.%. Cylindrical samples, the diameter and height of which was 5 cm, were molded under a static load of 30 kg / cm and kept in a chamber of 100% humidity for 3, 7, 14, and 28 days, after which they were tested for strength and water resistance. The results are presented in table 1.

Studies have shown that the strength of the fortified man-made soil increases with the increase in the proportion of powder reagent in the WWTP waste mixture. The obtained strength indicators meet the requirements of GOST 23558-94 “Mixtures of crushed stone, gravel and sand and soils treated with inorganic binders for road and airfield construction”.

In order to assess the degree of disinfection of wastewater treatment plants with the introduction of a complex powder reagent, analyzes of the total protein content in the resulting reinforced man-made soil were carried out.

Before the powder reagent was introduced into the BOC waste mixture, the total protein content in it was 110-115 mg / g dry matter, and an hour after the mixture was alkalized with the addition of powder reagent, the total protein content decreased to 30-45 mg / g. After daily aging of the prepared mixture (wastewater treatment plants and powder reagent), the total protein content was not detected. In addition, it should be noted that when a powder reagent of the proposed composition is introduced into the WWTP waste mixture, its unpleasant putrefactive odor immediately disappears, which indicates the cessation of putrefactive processes caused by the activity of microorganisms.

To determine the degree of neutralization of the wastewater treatment mixture, experiments were conducted to evaluate the chemisorption absorption of heavy metals and other ecotoxicants of the aluminosilicate mineral matrix formed as a result of alkaline hydrolysis of the clay component of the powder reagent. The processes of desorption of heavy metals from the initial mixture of wastewater from wastewater treatment plants and the resulting reinforced man-made soil were evaluated by the results of aqueous extracts after 1 and 3 days of the excimer aging of the samples. The results are presented in table 2. The output of these ecotoxicants does not exceed the MPC.

The content of mobile forms of ecotoxicants was determined using the study of acetate-ammonium extracts. The results of these studies are shown in table 3. The content of mobile forms of ecotoxicants in samples of technogenic fortified soil also does not exceed permissible MPC.

Based on this, it can be concluded that the resulting man-made fortified soil is ecologically safe.

Example 2

To obtain a technogenic soil in the mixture of wastewater treatment plants (similar in composition to example 1) were added powder reagent in an amount of 5.0; 10.0; 15.0; and 20.0 wt.%. The complex powder reagent had the following composition: clay - 50.0 wt.%, Lime 35.0 wt.%, Cement - 5.0 wt.%, Complexing agent (dolomite flour) 10.0 wt.%.

After the reagent was introduced into the wastewater treatment mixture, it was mixed for 5 minutes using a VSML vibro-mixer (2 × 100). Then, the resulting mixture was kept for 1 day in a chamber of 100% humidity, after which the reaction of the soil medium was determined. Since the reaction of the medium was in the alkaline range (pH 10.0-11.0) as a result of the additives of the powder reagent, vegetable soil additives (pH 6.2) were added to the mixture in a weight ratio of the mixture to the alkalizing additive of vegetable soil from 1.0: 0.3 to 1.0: 0.6.

For the preparation of soil samples, ground (humus) peat (pH <5.0) in a ratio of 1.0: 0.2 to 1.0-0.25 was also used as a leaching additive.

The obtained samples of artificial soil were kept for 1 day in a chamber of 100% humidity, after which control determinations of the reaction of the medium were carried out. The results show that the pH of the samples made in accordance with the declared quantitative ratios of the components is less than 8.5, that is, the leaching of the medium is sufficient and the man-made soil can be recommended both for lawn construction and for other public utilities. The research results are shown in table 4. Total protein in the manufactured soil samples was not detected.

Thus, the present invention provides a comprehensive treatment of sewage sludge from treatment plants with their disinfection and neutralization and obtaining environmentally friendly recycling products using available materials and standard equipment, which confirms its compliance with the criterion of "industrial applicability".

Table 1 No. p / p The amount of powder reagent, wt.% The compressive strength of the samples (MPa) after exsiccator storage, days Water resistance of samples, Kv = Rv / Re 3 7 fourteen 28 Re Re Re Re Rв one 10.0 0.17 0.22 0.36 0.51 0.34 0.67 2 20,0 0.39 0.51 0.72 0.89 0.83 0.93 3 30,0 0.54 0.78 0.95 1.47 1.42 0.95 four 40,0 0.87 0.98 1,58 2.25 2.21 0.98 Re is the compressive strength of the samples of desiccation storage, MPa;
Rв - compressive strength of samples of desiccation storage after water saturation, MPa

table 2 No. p / p Composition characteristics The concentration of ecotoxicants in an aqueous extract, mg / g a) the concentration of ecotoxicans was determined 1 day after the introduction of the reagent, b) the same, after 3 days Pb Cu Zn Ni Cd With Cr total Fe Mn Hg Al one. CBS waste mix 0.15 0.27 0.96 0,087 0.008 0.019 0.18 23 1.10 0.0014 8.9 2 but) The same, after the introduction of the reagent - 10 wt.% 0.016 0.09 0.31 0.017 <0.005 <0.002 0.02 2,3 0,03 <0.001 0.36 b) 0.02 0.005 0.013 0.001 <0.005 <0.001 0.01 0.19 0.01 <0.001 0.01 3 but) Also after the introduction of the reagent - 20 wt.% 0.01 0,03 0.06 0.003 <0.002 <0.001 0.01 0.27 0.02 <0.001 0.23 b) 0.005 0.01 0.004 <0.001 <0.001 <0.001 0.003 0.05 0.01 <0.001 0.11 3 but) Also after the introduction of the reagent - 30 wt.% 0.005 0.01 0.01 0.001 <0.001 <0.001 0.003 0,07 0.01 <0.001 0.12 b) <0.001 0.002 0.001 <0.001 <0.001 <0.001 <0.001 <0.01 <0.001 <0.001 0.01 four but) Also after maintaining the reagent - 40 wt.% 0.001 0.003 0.001 <0.001 <0.001 <0.001 0.001 0,03 <0.001 <0.001 0.06 b) <0.001 0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.01 <0.001 <0.001 0.01 MPC 0,03 1,0 1,0 1,0 0.001 0.01 0.05 - 0.1 0.002 -

Table 3 No. p / p Composition characteristics The concentration of ecotoxicants in the acetate-ammonium extract, mg / g Pb Cu Zn Ni Cd Co Cr total Fe Mn Hg Al one CBS waste mix 0.37 0.43 1.82 1.05 0,045 0.75 1,02 33.1 3.41 0.007 13.6 2 The same, after the introduction of the reagent - 10 wt.% 0.02 0.14 0.47 0.02 <0.001 0.001 0,03 3,1 0,07 <0.001 0.41 3 The same, after the introduction of the reagent - 20 wt.% 0,07 0,061 0,035 0.001 <0.001 <0.001 0.02 0.15 0,03 <0.001 0.06 four The same, after the introduction of the reagent - 30 wt.% <0.001 0.003 0.005 <0.001 <0.001 <0.001 <0.001 0.001 0.01 <0.001 0.01 the concentration of ecotoxicans was determined 1 day after the introduction of the reagent

Table 4 No. p / p The name of the technological operation of the production of technogenic soil. Introduction of complex powder reagent Mixture leaching Control assessment of the reaction of the medium after 3 days The amount of powder reagent, wt.% mixture pH Type of additive, amount, wt.% mixture pH PH medium Degree of alkalization After 1 hour after 24 hours After 1 hour after 24 hours one 5,0 9.5 8.3 grows up. soil - 30.0 7.0 6.7 6.4 disadvantages. peat - 5.0 6.9 6.5 6.3 2 10.0 11.6 10,2 grows up. soil - 40.0 9.1 7.8 7.7 enough. peat -15.0% 8.7 7.6 7.5 3 15.0 12.1 11.0 grows up. soil - 50.0 9.7 8.4 8.2 enough. peat - 20.0 9,4 8.2 7.9 four 20,0 12.5 11,4 grows up. soil - 60.0 10.7 8.9 8.7 excess. peat - 25.0 10.3 8.7 8.6

Claims (3)

1. The method of complex processing and disposal of sewage sludge, including preliminary dewatering of sludge from primary sedimentation tanks and activated sludge, mixing with sand from sand traps, disinfection by means of a reagent and obtaining a recycling product, characterized in that it additionally conducts decontamination of sludges, moreover, as a disinfecting and neutralizing the reagent use a complex powder reagent of the following composition: clay 40.0-60.0 wt.%, lime 5.0-40.0 wt.%, cement 5.0-40.0 wt.%, complexing agent, selected from the range: a mixture of metal oxides, ash, crushed slag, dolomite flour, ground limestone 5.0-10.0 wt.%, the amount of reagent is 10.0-30.0% by weight of the mixture, the specified reagent, dehydrated primary sediments sedimentation tanks and activated sludge are fed into the mixer simultaneously with sand from sand traps and additionally with pre-ground superlattice wastes of primary settlers, where they are processed until a homogeneous mixture is obtained, which is placed in a storage hopper. 2. The method of complex processing and disposal of sewage sludge according to claim 1, characterized in that for the production of man-made fortified soil, the amount of powder reagent is 20.0-30.0 wt.% When the clay content is 40.0-50.0 wt.%, lime 5.0-20.0 wt.%, cement 30.0-40.0 wt.%, complexing agents, which are selected as metal oxides, or ash, or crushed slag, 5.0-10, 0 wt.%. 3. The method of complex processing and disposal of sewage sludge according to claim 1, characterized in that for the production of technogenic soil, the amount of reagent is 10.0-15.0 wt.% When the clay content is 40.0-50.0 wt. %, lime 20.0-40.0 wt.%, cement 5.0-10.0 wt.%, complexing agents, which are selected dolomite flour or ground limestone, 5.0-10.0 wt.%, with this, the exposure time of the resulting mixture in the storage hopper is at least 24 hours, after which a leaching additive in the form of plant soil is added to it in a ratio of 1.0: 0.4 to 1 , 0: 0.6 or peat in a ratio of 1.0: 0.15 to 1.0: 0.25.