RU2531931C1 - Method of physical and chemical wastewater treatment - Google Patents

Abstract

FIELD: agriculture.

SUBSTANCE: invention may be used for treatment of waste waters containing substances of organic nature, in the enterprises of food and fishing industry with the disposal of the isolated product. When implementing the method, the coagulant was used as surplus activated sludge concentrated to the dry matter content of 7-10 g/l. Then, the activated sludge is subjected to acoustic cavitation treatment. The mode of stiffness of the acoustic cavitation treatment is 2.5-3.5 kHz·hour. The stiffness of the mode is determined by the formula Θ=τ׃, where τ is the treatment time, hour, ƒ is the frequency of ultrasonic vibrations of the piezoelectric generator, kHz. The treated sludge is directed into the waste water in a ratio of 1:2, and the deposition is carried out. The precipitate is isolated and disposed.

EFFECT: method provides substantial simplification of purification technology while maintaining its efficiency.

2 cl, 4 dwg, 2 ex

Description

The invention relates to regenerative methods for treating wastewater containing substances of an organic nature, and can be used in food and fishing enterprises with the disposal of the selected product.

Wastewater of food and fish processing industries is a polydisperse system of complex composition, which is characterized by a high content of valuable components of organic and inorganic nature - protein and lipid compounds, their hydrolysis products, biologically active substances, vitamins and minerals.

At the treatment facilities of fishing industry enterprises, reagent wastewater treatment methods are widely used. But coagulants traditionally used in reagent treatment lead to a high residual content of metal ions in the water (Al ³⁺ , Fe ³⁺ ), the use of synthetic flocculants in reagent treatment carries the danger of a high residual toxic monomers in the treated waste water. The coagulants and flocculants used irrevocably convert the biologically active components of fish raw materials contained in the wastewater of fish processing plants into a bioacceptable form and exclude the subsequent use of sewage sludge.

The solution to the problem is the search for new forms of reagents for physical and chemical purification, devoid of the following disadvantages: high cost, residual concentration in purified water, low degree of purification, secondary contamination of the sediment.

In this regard, it is promising to use natural bioflocculants as potentially biologically acceptable reagents, in particular, excess activated sludge formed during biological wastewater treatment. It is known that activated sludge independently produces flocculants for its own flocculation, which are extracellular biopolymers, metabolic products of activated sludge. The use of excess activated sludge as a reagent for physicochemical treatment allows the use of reserve biopolymers to flocculate wastewater pollution (1,2,3). In addition, the use of excess activated sludge for reagent wastewater treatment of food production allows not only wastewater treatment, but also to ensure the extraction of valuable components of wastewater from food production without reducing their quality to produce a high-quality protein mineral product.

However, it is known that the release of bioflocculants by microorganisms of activated sludge depends on factors such as temperature, the phase of the vital activity of microorganisms, environmental conditions, and some others. Thus, it is relevant to find a method that allows you to remove biopolymers of activated sludge from the cell membrane, regardless of the above factors, without violating or not destroying the native properties of its biopolymers, which determine their flocculation abilities. The most promising is the use of acoustic cavitation treatment of activated sludge, implemented in the present method.

Closest to the claimed method is a method of separating suspended solids from the original wastewater during aerobic biological wastewater treatment (US Pat. RF No. 2073649, publ. 1997.02.20). The method consists in introducing excess activated sludge, which is in the endogenous phase of metabolism and subjected to preliminary physical and mechanical treatment by various modes of hydrodynamic cavitation exposure or disintegration of microorganism cells, into the initial waste fluid as a coagulant, after which the resulting mixture is precipitated. Moreover, the endogenous phase of the metabolism of activated sludge is provided by creating modes of cultivation of microorganisms during aerobic biological treatment. In all examples of wastewater treatment according to the invention indicated that the deposition efficiency compared with traditional methods increased by an average of 15-30%.

But this method has inherent disadvantages, which are as follows:

- the known method provides wastewater treatment only from suspended particles;

- the known method provides wastewater treatment only when using activated sludge located in the endogenous phase of metabolism in the process of aerobic biological wastewater treatment;

- the endogenous phase of metabolism must be ensured by creating regimes for the cultivation of microorganisms during aerobic biological treatment, ensuring a consistent change in their nutritional conditions from excess nutrient substrate to deep aging microorganisms;

- the composition of the activated sludge biocenosis in the process of aerobic biological treatment is specially formed by introducing a pre-grown consortium into wastewater, which provides a shift in the process of biocenosis formation towards suppressing the growth of filamentous and non-flocculating microorganisms;

- and, finally, the known method can only be used to separate suspended solids from the original wastewater during aerobic biological wastewater treatment and obviously cannot be used in such technological treatment schemes in which there are no aerobic biological treatment facilities.

Thus, to ensure the maximum isolation of bioflocculants by cells, laborious, long and complex processes of cultivation of activated sludge with a specially formed biocenosis are used, processes of providing special cultivation regimes, including successive changes in their nutrition conditions, as well as monitoring and ensuring a special state of activated sludge - the endogenous phase of metabolism . The above disadvantages, including the availability of special biological treatment plants for the cultivation of microorganisms, lead to the complexity, duration, complexity and high cost of the process of the known cleaning method. These disadvantages, in addition, lead to a rise in the cost of the disposed product.

The task of the invention is to provide a method that allows:

1) carry out wastewater treatment from suspended, colloidal and dissolved substances;

2) to exclude time-consuming, lengthy, complex and expensive processes of cultivation of activated sludge with a specially formed biocenosis and the processes of providing special cultivation regimes and thus carry out biofloculation wastewater treatment using activated sludge regardless of the stage of metabolism.

The technical result, to which the claimed invention is directed, consists in simplifying the cleaning method while maintaining its effectiveness.

To achieve the technical result in the inventive method of physico-chemical wastewater treatment, the excess activated sludge is concentrated by sedimentation, or decantation, or thickening, or centrifugation, or filter pressing to a dry sludge content of at least 7-10 g / l, then acoustic cavitation treatment of activated sludge is carried out by regime hardness determined by the formula:

, $$\sout{O}=\tau \times \sout{\int }$$

,

Where

- жесткость режима, кГц·час, $$\sout{O}$$

- stiffness of the mode, kHz · hour,

τ - processing time, hour,

ƒ is the frequency of ultrasonic vibrations of the piezoelectric generator, kHz, and a component of 2.5-3.5 kHz · hour,

treated activated sludge is added to the wastewater in a ratio of 1: 2, after which the mixture is sent to flocculation and sedimentation. The sludge is separated from the treated wastewater, dehydrated, then the protein-mineral sludge is sent for further use as a protein component for starter and production feeds for fish, agricultural animals and birds.

Distinctive features of the proposed method for wastewater treatment (W) are the following. First, the concentration of excess activated sludge is carried out to a sludge dry matter content of 7-10 g / l, then it is treated with acoustic cavitation mode hardness determined by the formula:

, $$\sout{O}=\tau \times \sout{\int }$$

,

Where

- жесткость режима, кГц · час, $$\sout{O}$$

- stiffness of the mode, kHz · hour,

τ - processing time, hour,

ƒ is the frequency of ultrasonic vibrations of the piezoelectric generator, kHz. The stiffness of the mode is in the range of 2.5-3.5 kHz-hour. The introduction of condensed and treated by acoustic cavitation of activated sludge to the treated waste water is carried out in a ratio of 1: 2.

Due to the presence of these signs, it is possible to achieve the specified technical result.

The proposed method of wastewater treatment is illustrated by the drawings shown in figures 1-4.

Figure 1 presents the scheme for the treatment of CB with activated sludge (AI) treated with acoustic cavitation, figure 2 - average indicators of wastewater treatment using activated sludge with different dry matter contents, figure 3 - average indicators of wastewater treatment (CB ) when using condensed activated sludge treated with acoustic cavitation of different hardness conditions, figure 4 - indicators of wastewater treatment in the conditions of example 2.

The need to concentrate the excess activated sludge by sedimentation, or decantation, or thickening, or centrifugation, or filter pressing so that the dry matter content of sludge is at least 7-10 g / l, is dictated by the following research results (figure 2).

It was shown that an increase in the dry matter content of activated sludge (AI) from 1.5-3.5 g / l to 7.0-10.0 g / l significantly increases the efficiency of wastewater treatment, so the BOD of ₅ treated wastewater decreased from 160.44 to 111.24 mg / dm ³ . The values of the indicators of the content of suspended solids, solids, protein substances decreased, respectively, from 891 to 503 mg / dm ³ , from 480 to 240 mg / dm ³ , from 13.125 to 8.75 mg / dm ³ , thus leading to a significant improvement in quality sewage treatment.

The results of the experiments indicate an increase in the degree of wastewater treatment with an increase in the dry matter content of sludge, however, an increase in the intensity of biosorption of pollution is limited by the dry matter content of activated sludge of 7-10 g / l. With a further increase in the dry matter content of activated sludge to 15-30 g / l, the biosorption of wastewater contaminants is less active than with the current AI dose of 7-10 g / l, which is confirmed by some deterioration in the quality of wastewater treatment. So, indicators of BOD5, residual content of suspended solids, solids, protein substances increase from 111.24 to 126.28; from 503 to 736; from 240 to 360 mg / dm ^3, respectively. Thus, the optimal AI dry matter content for effective wastewater treatment should be 7-10 g / l.

The use of acoustic treatment of condensed activated sludge is due to the following.

When ultrasonic sludge is processed by ultrasound from a transmitter of a piezoelectric generator in the zones of local pressure decrease, discontinuities are formed in the form of cavities, which are filled with saturated vapor of a given liquid, short-lived, so-called cavitation bubbles arise, which begin to pulsate and collapse in the positive pressure phase. When gas bubbles collapse, large local pressures of the order of thousands of atmospheres arise, spherical shock waves form.

Acoustic microflows form near pulsating bubbles (4). Such intense impacts in the cavitation field lead to the destruction of bacterial cells and covers and the release of bioflocculants of activated sludge microorganisms, which we use for reagent (physico-chemical) wastewater treatment.

The effect of the release of bioflocculants during sonication, expressed by an increase in the efficiency of wastewater treatment, depends on the duration of the treatment and the frequency of acoustic vibrations.

So, when using a piezoelectric generator with a radiation frequency of 22.0 kHz, activated sludge was treated for 3; 3.5; 4; 5; 5.5; 6; 7; 8; 9; 9.5; 10; eleven; 11.5; 12; 13; fourteen; fifteen; 16; 17; eighteen; 19; twenty; 21; 22 etc. 30 minutes. When using a piezoelectric generator with a radiation frequency of 28.0 kHz, activated sludge was treated for the same time intervals except for an interval of 3.5 minutes. As a result, it was found that the duration of AI treatment to achieve the maximum effect of the release of bioflocculants varies depending on the frequency. Thus, the maximum effect of the release of bioflocculants, assessed by the efficiency of wastewater treatment, when using radiation with a frequency of 22.0 kHz was observed during treatment lasting 7-9.5 minutes, and when using radiation with a frequency of 28.0 kHz, the same effect was observed with a shorter treatment time 5.5-7.5 minutes. A significant deterioration in the quality of wastewater treatment was observed when using activated sludge treated for 14 minutes or more at a frequency of 22.0 kHz or treated for 11.0 minutes or more at a frequency of 28.0 kHz. A combination of factors affecting the degree of isolation of bioflocculants and cleaning efficiency was characterized by the concept of rigidity of the cavitation treatment mode, which determines the combination of the duration of exposure with the frequency of ultrasonic vibrations of the piezoelectric generator. Under the stiffness of the mode, a parameter is adopted that relates the frequency of the ultrasonic vibrations of the generator and the processing time and is determined by the formula

, $$\sout{O}=\tau \times \sout{\int }$$

,

Where

- жесткость обработки, кГц·час; $$\sout{O}$$

- processing hardness, kHz · hour;

τ - processing time, hour;

ƒ - frequency of ultrasonic oscillations of the generator, kHz.

The notion of regime rigidity was taken by analogy with the term sterilization rigidity (heat treatment rigidity), which is taken as the product of the treatment duration and the heating intensity (temperature), or treatment rigidity = treatment duration, hour × temperature, ° C (5.6).

The notion accepted by the authors of the rigidity of the cavitation treatment mode adequately describes and determines the necessary treatment regime for activated sludge by ultrasound, regardless of the availability of the piezoelectric generator and its frequency. So, in our case, the rigidity of the processing mode corresponded to the following values of the frequency of ultrasonic vibrations and duration:

Processing rigidity * Processing time **, min 22.0 kHz 28.0 kHz 1.1-2.0 kHz 3,5-6,5 2.5-4.5 2.5-3.5 kHz 7.0-9.5 5.5-7.5 4.0-4.7 kHz 11.0-13.0 8.5-10.0 5.1-11.0 kHz 14.0-30.0 11.0-24.0

* The calculation of the stiffness of the regime was carried out as described below:

For processing at 22.0 kHz

- 22.0 × 3.5: 60 = 1.3 kHz

- 22.0 × 4.0: 60 = 1.5 kHz

-22.0 × 5.5: 60 = 2.0 kHz · hour and so on

For processing at 28.0 kHz

- 28.0 × 3.0: 60 = 1.4 kHz

- 28.0 × 4.0: 60 = 1.9 kHz

- 28.0 × 5.5: 60 = 2.56 kHz · hour and so on

** The calculation of the necessary duration of exposure, taking into account the necessary rigidity, was performed in the opposite way:

- to obtain a stiffness of 3.3 kHz · hour, it is necessary to process with ultrasound at a frequency of 22.0 kHz - 3.3: 22.0 × 60 = 9 minutes,

- to obtain the same stiffness of 3.3 kHz · hour, it is necessary to process with ultrasound at a frequency of 28.0 kHz - 3.3: 28.0 × 60 = 7 minutes.

The adequacy of the use of the concept of regime stiffness was observed in all studied ranges of treatment duration and frequency of ultrasonic vibrations, the calculated stiffness parameters of acoustic cavitation treatment of activated sludge determined identical cleaning indicators within the same regime stiffness range for different frequencies and duration of wastewater ultrasonic treatment in accordance with the above a table.

The choice and use of acoustic cavitation treatment of activated sludge with a regime hardness of 2.5-3.5 kHz · hour is due to the results of experiments on wastewater treatment with activated sludge treated with acoustic cavitation with different regime hardness (Fig. 3).

It was noted that the treatment of activated sludge by cavitation with a regime hardness of 1.1–2.0 kHz · hour; 2.5-3.5 kHz · hour; 4.0-4.7 kHz · hr generally improved wastewater treatment performance. However, the best results were achieved using activated sludge cavitation treatment with a regime hardness of 2.5–3.5 kHz · h, which gave maximum wastewater treatment indicators of 93.1% for suspended solids; 46.5% by protein concentration and 62.8% by BOD ₅ (Fig. 3). Acoustic cavitation treatment of activated sludge with a regime hardness of 1.1–2.0 kHz · h, 4.0–4.7 kHz · h and 5.1–11.0 kHz · h led to unsatisfactory wastewater treatment results, which explains apparently, in one case, insufficient time for destruction of the cell wall (in the case of 1.1-2.0 kHz kHz · hour and 5.1-11.0 kHz · hour).

Moreover, acoustic cavitation treatment, the rigidity of which exceeded 5.1 kHz · h, in all cases showed cleaning results that were worse or comparable with the results of cleaning with untreated activated sludge, which is obviously due to the onset of processes of destruction, denaturation and loss of native properties of activated sludge biopolymers as a result of such cavitation treatment. The data obtained indicate that the acoustic cavitation treatment of activated sludge must be normalized by the severity of the regime to achieve the planned technical result, otherwise it can lead to results that level the feasibility of its use.

In addition, it was found that the use of reagent-treated AI cavities treated with acoustic cavitation is not limited to the effects associated with clarification of a suspension of wastewater and the deposition of suspended solids CB. It was noted (Fig. 3) a decrease not only in terms of the presence of a precipitated fraction in water, but also in terms of the content of dissolved substances and protein in the system due to exopolymers effectively released by bacteria. Moreover, the best values of the extraction of dissolved substances and nitrogen-containing components are achieved using activated sludge treated with a hardness of 2.5-3.5 kHz · hour.

Thus, the proposed method of physico-chemical wastewater treatment allows not only to separate suspended wastewater substances, but also to carry out the biosorption of dissolved substances and nitrogen-containing wastewater components. At the same time, a rather high cleaning efficiency was achieved for a number of indicators, an additional high-quality protein product was obtained, the feed value of which is due to the extracted valuable components of the wastewater of food production.

The method is as follows. First, activated sludge (AI) is concentrated to a dry matter content of 7-10 g / l, for this, AI is sent to apparatus 1. In apparatus 1, the AI is concentrated by settling, or decantation, or thickening, or centrifugation, or filter pressing. Then, acoustic cavitation AI processing is carried out in chamber 2 using a piezoelectric generator 3 mounted at the bottom of chamber 2 and generating ultrasonic vibrations (Fig. 1). The processing of AI by acoustic cavitation is carried out by the stiffness of the regime, which is in the range of 2.5-3.5 kHz · hour. The processed AI through the dispenser 4 enters the mixing chamber 5, where untreated wastewater (SV) also enters, and the AI: SV ratio is 1: 2. In the mixing chamber 5, the CB and AI are mixed; for this, hydraulic and mechanical mixers are used. Then carry out the deposition in the chamber 6 flocculation with the release of sediment. Purified water (OM) is supplied for purification, and the sediment is dehydrated and sent for further use as a protein component for starter and production feeds for fish, agricultural animals and birds.

Example 1

500 ml of pre-decanted activated sludge with a dry matter content of 9.1 g / l is treated with acoustic cavitation with a mode hardness of 2.9 kHz · hour (for 8.0 minutes at a frequency of ultrasonic vibrations of 22 kHz). The treated suspension is mixed with 1000 ml of wastewater from a fish processing enterprise with BOD5 values of 169.3 mgO ₂ / L and 5880.0 mg / L for suspended solids. Mixing a mixture of wastewater and activated sludge is mechanical. The resulting precipitate is separated by settling for 60-120 minutes. BOD _{5 of} purified water is 64.8 mgO ₂ / L and 542.1 mg / L for suspended solids, i.e. the degree of purification was 61.7% for BOD ₅ and 90.8% for suspended solids.

Example 2

Wastewater with BOD ₅ 197.7 mgO ₂ / l and a suspended solids concentration of 6150 mg / dm ³ are mixed separately with pre-decanted activated sludge with a dry matter content of 8.0 g / l, treated with acoustic cavitation with different hardness of 3.5 kHz · Hour (within 9.5 minutes at a frequency of ultrasonic vibrations of 22 kHz), 7.3 kHz · hours (within 20.3 minutes at a frequency of ultrasonic vibrations of 22 kHz), as well as at 9.1 kHz · hour ( for 19.5 minutes at a frequency of ultrasonic vibrations of 28 KHz). The purified water was characterized by BOD ₅ 63.5 mgO ₂ / l (for hardness 3.5 kHz · h), 112.7 mgO ₂ / l (for hardness 7.3 kHz · h) and 117.5 mgO ₂ / l (for hardness 9.1 kHz · h). The residual concentrations of suspended solids were 485.0 mg / dm ³ (for hardness 3.5 kHz · h), 2970 mg / dm ³ (for hardness 7.3 kHz · h) and 3210 mg / dm ³ (for hardness 9.1 kHz · hour). Thus, the best cleaning performance was observed in the implemented method when using activated sludge treated with a cavitation regime of hardness 3.5 kHz · h, for which the degree of purification was 67.9% for BOD ₅ , 92.1% for suspended solids. The cleaning indicators are presented in the table (figure 4).

Literature

1. Technical reference for water treatment: in 2 tons. T 1: Trans. with fr. - St. Petersburg: New Journal, 2007.

2. Xenophon B.S. Intensification of wastewater treatment in chemical industries using bioflocculants. // Life safety, No. 10, 2009 - p. 18-20.

3. Gvozdev V.D., Ksenofontov B.S. Industrial wastewater treatment and sludge recovery. - M.: Chemistry, 1988, 112 p.

4. The Great Soviet Encyclopedia: In 30 vols. - M.: ″ Soviet Encyclopedia ″, 1969-1978.

5. Soklakov VV Optimization of sterilization regimes for canned fish according to nutritional indicators. Diss ... cand. tech. sciences. - Kaliningrad, 2002.188 s.

6. Shvidkaya 3.P. The effect of heat treatment rigidity on the structural properties of muscle tissue of fish with a high moisture content. // Research. by technol. new objects of fishing. Vladivostok, 1980 .-- P. 45 - 48.

Claims (2)

1. A method of physico-chemical wastewater treatment, including the introduction into the wastewater as a coagulant of excess activated sludge pretreated with cavitation, precipitation, characterized in that the activated sludge is concentrated to a dry matter content of 7-10 g / l, then it is treated acoustic cavitation mode rigidity, determined by the formula:

,
Where

- stiffness of the mode, kHz · hour,
τ - processing time, hour,
ƒ is the frequency of ultrasonic vibrations of the piezoelectric generator, kHz, and a component of 2.5-3.5 kHz · hour,
the introduction of activated sludge into wastewater is carried out in a ratio of 1: 2. 2. The method according to claim 1, characterized in that the concentration of activated sludge is carried out by sedimentation, or by decantation, or by thickening, or centrifugation, or by filter pressing.

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