SU1733477A1 - Method for preparation of flocculant from activated sludge - Google Patents

Abstract

Usage: enterprises of the microbiological industry, in hydrolyzed yeast production. The essence of the invention: hydrolysis of the suspension of active sludge is carried out at 150-180 ° C. C in the presence of sulfuric acid with a concentration of not less than 0.4% for 2 hours. 4 Il., 4 tab.

Description

The invention relates to methods of flocculants from activated sludge (AI), which can be used to precipitate suspended substances of aqueous suspensions, in particular, to clarify the hydrolysates of vegetable raw materials from lignohumic substances in the microbiological industry,

It is known to use as flocculant for water purification of biomass of microbial cells.

Such flocculants are consumed in large quantities due to low efficiency.

Of interest is the use of biomass of microorganisms, which are waste products or by-products.

As flocculant, excess AI can be used that is formed during biochemical wastewater treatment (CB).

A known method of obtaining flocculate from AI is by extracting the latter with a solution of a complexing agent (EDTA, nitrilotriacetic acid) by adding to the extract a 1% solution of NaCl in ethanol. A product is precipitated from which nucleic acids are isolated.

The complex of extracellular biopolymers obtained by the indicated method cannot be effective flocculant, since the isolated proteins are denatured in the process of deproteinization of nucleic acids.

A known method for producing water insoluble flocculating biopolymers from AI. In this method, the AI is extracted with a solution of a complexing agent, for example, 2% ethylene diamine tetraacetate, the extract

treated with 2% NaCl solution in isopropyl alcohol, the separated precipitate is dissolved in water and treated with a saline solution containing polyvalent metal ions, such as MD2 +, Ca2, in an amount of 0.05-0.1525 mEq / mg of precipitate precipitate the desired product at 4 -20 ° C. The yield of flocculating biopolymers is 30% of the dry weight of the sludge used.

One of the drawbacks of this method is the treatment with an extractant of biomass AI.

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In addition, the method is based on multistage technology.

To implement the individual stages, it is necessary to develop special equipment, for example, an extractor, a cooling unit.

Reagents for extraction and salting out are produced by the industry in a limited quantity, which is not enough to implement the method even in one plant.

The precursor recovered from the extract is a colloidal precipitate and is characterized by low sedimentary and filtration properties, and e. It is difficult to isolate the precipitate from the extract.

Thus, flocculation from AI is preceded by a complex process of thickening the AI, processing biomass with chemical reagents and multiple excretion of the forming precipitates.

The disadvantage of this method is that it provides only partial use of AI biomass. Only extracellular flocculating polymers are recovered by a known extraction method. The product yield is 30% of the dry weight of the activated sludge used, i.e. 30% AI solids are used, and 70% are waste.

In addition, reagents that generate additional waste are used in the flocculation process. At the same time, the AI biomass does not undergo heat treatment either before extraction or after extraction, i.e. no ecological cleanliness.

The purpose of the invention is to increase the flocculating ability of the target product and simplify the method.

This goal is achieved by acid hydrolysis of an AI suspension (1.5% a.s.c.) after secondary clarification tanks of wastewater treatment plants in the presence of sulfuric acid with a concentration of at least 0.4% at 150-180 ° C.

Conducting hydrolysis of the AI according to the indicated regime allows obtaining biopolymer substances in the hydrolysis of the AI, which contribute to the precipitation of lignohuminic substances in the neutralized hydrolysis of plant raw materials.

The AI is complex in composition and is an association of microorganisms, the biomass of which mainly contains proteins, fats and fat-like substances, trace elements and minerals, and vitamins are found.

Characteristics of the AI suspension from secondary settlers of the treatment facilities of the Kirov Biochemical Plant are given in Table 1.

In the course of thermo-acid treatment of an AI suspension, degradation of biomass components takes place more deeply, proteins are degraded to amino acids and peptides.

0 In the process of acid hydrolysis of AI, destruction of cell walls of microorganisms with high mechanical strength also occurs. As a result of the thermochemical factors, the permeability of cell walls is greatly increased, which leads to the release of intracellular biopolymers with a large mol. by weight. A complex of biopolymer flocculating compounds is obtained which

0 provide a high degree of purification from a dispersed system of suspended substances from various types.

Such a result cannot be achieved by an extraction method, in which only extracellular biopolymers are attracted from 5. Obtaining effective flocculant from the AI according to the proposed method is achieved by the correct choice of temperature, amount of acid and duration of hydrolysis for destruction of the cell walls and macromolecules of the AI.

Different modes of hydrolysis of AI were investigated with various combinations of parameters. The effect of parameters on the degree of destruction of AI biomass and flocculating abilities of traffic police, obtained under the following conditions, was studied: temperature 120-180 ° C; HaSCM concentration of 0.1-1.0%; the duration of hydrolysis of 1-4 hours

The depth of hydrolysis of the biomass of the AI was estimated by the amount of suspended particles (a.s.s., g / l) before and after hydrolysis. The required degree of splitting of the biomass of the AI was evaluated both by the depth of hydrolysis and

5 according to the effectiveness of the action of AI hydrolysates (GAI) in the process of clarifying the neutralizer of vegetable raw materials.

FIG. 1 and 2 show the dependences of the amount of hydrolyzed AI mass.

0 from the conditions of hydrolysis.

From the graphs it can be seen that, at an acidity of 0.2-0.25%, heat treatment for 2 hours at 130 ° C is sufficient for maximum hydrolysis of the AI biomass (78-80%). Further

5 an increase in temperature has no significant effect on the degree of hydrolysis of biomass. The higher the temperature, the closer the location of the curves at 170 and 180 ° C, they almost coincide. Therefore, the upper temperature limit in the process of hydrolysis of the AI is 180 ° C. A further increase in temperature is economically inefficient.

When the acidity is 0.4-0.5%, heat treatment for 1 hour at 130-180 ° C is sufficient for maximum hydrolysis of the AI biomass.

The greatest degree of destruction of AI biomass is 80-83% and the maximum amino acid content of 64-102 mg% is obtained by GAI obtained during hydrolysis at 130-180 ° C with an acid concentration of at least 0.4% within 2 hours.

Characteristics of the traffic police are given in table. 2. Given in Table. 2 the number of amino acids reflects the total content of 17 amino acids.

Under the same conditions, the flotation properties of traffic police were evaluated.

FIG. 3 shows the dependences of the amount of non-precipitated substances of neutralized hydrolyzates of vegetable raw materials on the conditions for obtaining the traffic police.

The higher the hydrolysis temperature, the fewer non-precipitated substances. Curve 1 (value 130 ° C) lies above curves 3 and 5 (values 150 and 180 ° C). Curves 3 and 5 are located close to each other. Therefore, a value of 150 ° C is the lower limit, and 180 ° C is the upper limit.

Fracture of the curves is observed at an acidity of 0.4-0.5%. A further increase in acidity does not affect the deposition rate of lignohumic substances. Therefore, this concentration is the lower limit. Increasing the dose of traffic police also contributes to an increase in the rate of sedimentation of ligmogumin substances.

FIG. Figure 4 shows the dependence of flocculation properties of traffic police on the time of hydrolysis.

Checking the flocculation properties of traffic police, obtained under these heat treatment conditions, but with a longer time (2 hours) showed that an increase in the processing time of AI biomass contributes to an increase in flocculation properties.

A comparative assessment of the effectiveness of flocculants obtained by the proposed and known methods has been carried out. The research results are presented in Table. 3

From tab. 3, it follows that the flocculant according to the proposed method is more effective when using neutralized hydrolysates of vegetable raw materials in the clarification process. Within 1 h, the number of non-precipitated lignohumic substances in the control experiment was 8.6%, when using GAI 2.8% and flocculant obtained by a known method, 6.7%.

The amount of traffic policeman added to the neutralized agent affects not only the effectiveness of its action, but also the good quality of the neutralized agent. The clarified neutralizer is sent for biochemical processing, being a nutrient medium (wort) for growing fodder yeast.

The traffic police itself is a nutrient medium containing not only proteins, but also sugars, amino acids, peptides, vitamins, marco and trace elements necessary for

growth and development of various microorganisms.

In its composition, the traffic police are very close to the composition of the neutralized vegetable raw materials. Therefore, the addition of GAI to the neutralizer for flocculation of lignohumic substances cannot significantly change its characteristics, but only increases the nutritional value. In addition, the traffic police contain biostimulators of microbial growth

(vitamins, amino acids, microelements). The data of Table 4 reflect the yield of protein fodder yeast in the process of growing the latter on medium with and without GAI.

The medium was prepared on the basis of the production wort diluted with water to a content of reducing substances (PB) of 1.2%. 5, 10% and 15% GAI of the total nutrient

substrate.

750 ml bottles were poured into 50 ml of the test medium in the shaker flasks, and the same amount of biomass was seeded. The culture was grown for 18–20 hours at 36–38 ° C on rocking chairs in triplicate. The biomass concentration was determined by the gravimetric method using pressed yeast with subsequent determination of dry matter in them.

Research results show that, in addition to the flocculation properties, traffic police increases the nutritional value of clarified neutralisates.

The addition of traffic police in the amount of 5-10% to the nutrient substrate allows to increase the biomass yield from a given substrate (Table 4) by 1.2-11.1%.

Increasing the dose to 15% does not give a positive effect.

From the data table. 4 shows that the traffic police obtained at 150-180 ° C with an acidity of 0.4-0.5% and entered in a volume of 5-10 from the substrate, leads to an increase in the yield of absolutely dry yeast from PB, contributes more

full disposal of radioactive substances and do not reduce the good quality of purified neutralizers,

In order to effectively clarify the neutralizer, the amount of traffic police should be equal to 10 vol.% Of the substrate (nutrient medium).

The proposed method of producing flocculant from AI, as well as its application for more efficient clarification of the substrate, is technologically simple and allows the use of known equipment for hydrolysis, neutralization and clarification, as well as chemicals used in hydrolysis-yeast production.

The proposed method allows to fully utilize the large-tonnage waste.

When implementing the method, no pre-concentration of the AI suspension is required, and therefore additional costs.

The proposed method for the utilization of AI in hydrolyzed yeast production is the most promising and cheapest.

Example 1. The AI suspension is hydrolyzed in the presence of sulfuric acid with a concentration of 0.4% at 150 ° C for 2 hours.

GAI was added to the hydrolyzate of plant raw material diluted at 88-90 ° C with a bio-oxidized mash up to PB of 1.8% l in an amount of 10% of the total mixture. The mixture at 75-80 ° C is neutralized with a 25% aqueous solution of ammonia to a pH of 4.1-4.2 and aerated at 45-50 ° C for 30 minutes.

The mixture is stirred, poured into cylinders with a capacity of 250 cm3, placed in a thermostat at 40 ° C for 60 minutes, then the supernatant is decanted.

The efficiency of flocculation is characterized by clarification of the supernatant, expressed by the amount of suspended solids above the precipitate.

In parallel, a control experiment was carried out without the addition of traffic policemen.

The amount of non-suspended suspended matter in the supernatant: with flocculation, 4.6%; without flocculant 13.8%.

Example 2. AI suspension is hydrolyzed in the presence of sulfuric acid with a concentration of 0.4% at 180 ° C for 2 hours.

The mixing and neutralization of the traffic police with the hydrolyzate of plant raw materials is carried out analogously to example 1, adding the traffic police in the amount of 10% by volume of the substrate. The neutralized mixture is defended.

The amount of non-suspended suspended solids in the supernatant: with the introduction of flocculation, 4.2%; without flocculant 11.7%.

Claims (1)

Invention Formula The method of producing flocculant from activated sludge, characterized in that, in order to increase the flocculating ability of the target product and simplify the process, flocculant is obtained by treating the activated sludge with sulfuric acid with a concentration of at least 0.4% at 150-180 ° for 2 hours . Physico-chemical characteristics of the suspension of active sludge from the Kirov biochemical plant Table 1 5, jkl.G l B ,, 03 83 265 1.3 770 . 30066KkO 12.2 12.1. 3380 132.63.3 1.5 290 120b. NEP 20.7 E3.7 272.2 163102 -J SO with J -J J Acidity 0,% - 0.5 YAP i g eight I four 60 60ПО180 Hydrolysis time, min Phie.1  H § | And 1 that 6060POMO Hydrolysis time, min 2 No. ° C 170 ° C 150 ° G L 130 ° C 120 ° C 240 180 ° C 240 " $ 72 $ 5 in Is V Ј 2 0. 25 55 0.75 Acidity,% Fig.Z 76 / oo 6 The temperature of hydrolysis AI, ° C FIG L ten