RU2156749C1 - Method of treating fat-containing waste waters - Google Patents

Abstract

FIELD: waste water treatment. SUBSTANCE: waste water coming from small meat- processing enterprises is passed through grate and fat trap. Then, vegetable sorbent is added, mixture floated, filtered through sorption charge and subjected to biological purification. Resulting precipitates, flotation concentrate, polluted sorption charge, and regeneration water are subjected to anaerobic and aerobic treatment procedures. Biocenosis in biological treatment unit is fixed using special type of charge. EFFECT: reduced investment and operational expenses and enabled production of organic fertilizers. 5 cl, 1 dwg, 5 tbl, 6 ex

Description

 The invention relates to methods for treating wastewater (CB) containing fat and can be used in small enterprises that process meat and meat products.

 A known method of cleaning industrial CB enterprises of the food industry, with the possibility of recycling the selected product. The method includes the separation of mechanical impurities, electroflotation, electrocoagulation, and before electroflotation, crushed crab shell in the amount of 1.5-2 g / l is introduced into the water and mixed. [USSR author's certificate N 1680636 A1 cl. C 02 F 1/465].

 The disadvantages of the method are: the inability to completely utilize the precipitation formed due to the metal ions contained in it; the impossibility of widespread use of crab shell as a sorbent throughout Ukraine; as well as the high cost of the cleaning process, which makes it difficult to use this method in small meat processing plants.

 The closest in technical essence to the proposed invention and the achieved result is a method of cleaning industrial CB from emulsified fats, including filtration, flotation with feathers and sedimentation. [Application EPO N 0353314 CL MKI 4 C 02 F 1/40, 01 D 17/02, 33/073, 21/24, 1990].

 The disadvantages of this method are the unresolved issue of utilization and further use of precipitation formed in the cleaning process, as well as the use of a valuable product (pen) as a sorbent.

 The basis of the invention is the task of improving the method of purification of fat-containing wastewater, in which by replacing the sorbent, filter media and further multi-stage biological treatment of CB before dumping them into the pond, the utilization of the formed precipitation is ensured, thereby creating a waste-free production process for the treatment of fat-containing wastewater of small meat processing enterprises, there is a decrease in capital, operating and energy costs.

The problem is solved in that in the method of purification of fat-containing wastewater, including filtration, flotation with a sorbent and sedimentation, according to the invention, the following differences are provided:
a plant sorbent is introduced into the runoff, which has passed through a grate and a grease trap, as a sorbent;
the mixture is subjected to pneumatic flotation or electroflotation, filtered through a sorption charge and sent to the averager, and then to the multistage biological treatment unit by the communities of attached and free-floating microorganisms;
sediment formed at all stages of the treatment of fat-containing wastewater, flotation concentrate, regeneration water, used sorption charge are sent to the sediment recovery unit, where after anaerobic-aerobic treatment, thickening, and exposure to vermiculture, the worms are converted into organic fertilizer for farmland.

In addition, according to the proposed method as a sorption charge in the filter column using a vegetable sorbent; only sediments, flotator flotation concentrate and filtration mixture are subjected to anaerobic treatment; then the filtrate from the thickening of aerobically stabilized sediments is sent to the averager; and vermiculture exposure to worms of aerobically stabilized and thickened sediments is carried out in beds with a load of not more than 0.02 m ³ / m ^{2 of} surface per day.

 The method is illustrated by the technological scheme for the purification of fat-containing CB (see drawing).

 The scheme includes: a source water supply pipe 1, a grill 2, a grease trap 47, a SV supply pump 3 for flotation treatment, a pressure pipe 4, an air duct 5, a flotator 6 containing scrapers 7 for removing flotation concentrate 8, a perforated device 9 for uniform distribution of air, pockets for collecting grease mass 10, a drain pipe for grease mass 11, a drain pipe for profiled water 12, a mixer 13, into which vegetable sorbent is fed through a pipe 14 from a metering unit 15, a sediment drain pipe from a flotator 16, a filter column 17, the filtrate discharge pipe 18, the used sorption charge discharge pipe 19, the cost averager 20, the biological treatment water supply pipe 21, the biological treatment unit 22, the thin-layer module 23, the biological treatment unit 24, the recovery water and sediment discharge pipe 25, a contact tank 26, bleach lime supply pipe 27, purified water drainage pipe 28, sediment discharge pipe from contact reservoir 29, decanter 30, decanted water drainage pipe 31, grease discharge pipe mass 32, anaerobic bioreactor 33, fermentation sediment discharge pipe 34, aerobic stabilizer 35, stabilized precipitation discharge pipe 36, sludge compactor 37, gravity water discharge piping 38, compacted sediment discharge piping 39, vacuum sludge pad 40, centrate discharge piping 41, container for collection of dehydrated sludge 42, biological treatment tank 43, furnace 44, crusher 45, discharge pipe for waste crushed in the crusher 46, grease mass processing unit.

 The proposed scheme works as follows.

 SV by gravity through the pipeline for supplying the cleaned liquid 1 enters the hand grate 2, where there is a delay of large waste: paper, rags, confiscated items, scraps of twine, fragments of bones, hooves, etc. The detained waste is crushed in a crusher 45, followed by their discharge through pipeline 46 into the head of the structures.

 After the grate, the SWs are sent to the grease trap 47. The grease mass enters the processing unit 48, and the SW goes to the mixer 13 of the flotator 6 via the pressure pipe 4. The plant sorbent is fed from the gravimetric batcher 15 through the pipe 14, which is captured by water and goes directly to the flotator body .

Plant sorbent with a grain size of 0.5-2.5 mm in dry form is fed to a weight type 15 dispenser. The dose of plant sorbent entering the flotator, C _opil is: 40 mg _opil / mg _fat > C _opil ≥ 10 mg _opil / mg _fat , at a concentration of fats in CB 60 mg / L ≤ C _fat <6200 mg / L, respectively. In the flotator, part of the fat and proteins floats to the surface, swallowing on air bubbles (about 90% of the total amount of extracted fats and proteins), and the other part (about 10%) is adsorbed on the surface of the sorbent remaining in the SW. Units made of sorbent and fats tend to rise up due to their buoyancy. In the resulting flotation concentrate, the plant sorbent acts as a “supporting grid”, contributing to a more rapid dehydration of the foam compared to conventional flotation. The volume of the resulting flotomass is from 8 to 40% of the total amount of liquid being cleaned.

 Flotation concentrate 8 (with a humidity of 80-98%) is scrapped by scraper 7 into pocket 10 and discharged via line 11 to decanter 30. After settling for 60 minutes, the resulting fat mass with vegetable sorbent from the decanter is sent for aerobic digestion to the bioreactor 33, and the decanted liquid is returned to the head of the structures.

 Suspended substances with a density greater than the density of water are deposited at the bottom of the structure, dragging along a small portion of the fat. The percentage of sediment is 0.5-1% of the total amount of cleaned liquid. The precipitate is periodically (2-3 times a day) removed into the bioreactor 33 through a pipe 16.

 The flotator is equipped with a perforated device (for air supply) 9 - when using pneumatic flotation, or the cathode and anode - when electroflotation.

 Profiled water is discharged from the top of the flotator through line 12 to the filtration column 17. The column has a removable bottom, which simplifies unloading of the load. As a load, a vegetable sorbent is used. In the column there is a retention of fat and suspended solids, as well as the sorbent carried out from the flotator. Column filter cycle - 24 - 30 hours

The processed load is replaced daily (to prevent desorption, as a result of decay of the retained organic substances). Therefore, at low SV costs (up to 20 m ³ / day) due to the fact that the flow rate supplied to the filtration column decreases, and the sorption capacity of the charge remains the same (1 kg of the filter charge retains up to 80 g of contaminants), from the technological scheme it is possible exclude the flotator. In this case, SWs are fed directly to the filtration column after the grate and grease trap (the effect of filtrational purification of SWs is 98%).

 A mixed sorbent is cheap and its regeneration is impractical; moreover, it is a valuable component for obtaining fertilizer. Therefore, the spent load is sent to the sediment processing unit.

 Purified water, having passed the node 17, flows by gravity through the pipe 18 to the flow averager 20.

 Subsequent water treatment is carried out in units of biological treatment and post-treatment. Each block consists of three bio-drums with a ruff type aggregate. The treated effluents are discharged into a reservoir or for use via pipeline 28 after disinfection with a solution of bleach in a contact tank 26.

The step-by-step treatment of CB in the pre-treatment unit and the biological treatment plant is characterized by the following indicators:
1. Initial SV: suspended solids - 190-3800 mg / l, COD - 380-4800 mg O ₂ / l, fats - 100-6200 mg / l.

2. After flotation and filtration through a sorbent: suspended solids - 60-120 mg / l, COD - 300-500 mg O ₂ / l, fats - 30-110 mg / l.

3. After installing biological treatment: suspended solids - up to 10 mg / l, COD <40 mg O ₂ / l, fats - 0.

 In the sediment processing unit, the plant sorbent, as well as sewage impurities, fatty substances and suspensions are subjected to anaerobic digestion (33), with the possible production of biogas. Fermented sludge, as well as regenerated water and sludge from biological treatment units, pass through the pipes 34 and 25 to the aerobic stabilizer 35. Stabilized sediments are sent after compaction in the sludge compactor 37 (for 4-6 hours) through the pipe 42 to the vacuum sludge pads 40. Nadilova water through line 38 is returned to the head of the facilities or to the cost averager as biogenic feed. For biogenic recharge, household CBs can also be used.

Further processing of dehydrated sludge can be done in three ways:
1 method includes thermal drying in an oven 44. The precipitate obtained according to this method can be used as fertilizer.

2, the method includes biological treatment with worms 43, to obtain biohumus. The biohumus obtained after processing amounts to 1/20 of the initial sediment volume. Biohumus can be used as fertilizer for agricultural land;
3 method involves fermentation with biohumus.

Example 1. A sample of wood sawdust with a particle size of 0.5-2.5 mm was mixed with SV meat processing plant. The initial SV contained: suspended solids - 3400 mg / l, fat - 2700 mg / l, BOD ₂₀ - 1700 mg / O ₂ / l. The dose of sawdust was 9 mg _sawdust / mg of _fat .

 A mixture of runoff with sawdust at a rate of 50 l / h was fed to pneumatic flotation. A fabric aerator was used as aerators in a pneumatic flotator. Flotation was carried out for 40 min; in parallel, a comparative experiment was performed on the cleaning of CB in an electroflotator. In the electroflotator there are vertical carbon-iron electrodes. The flotators are also equipped with a central pipe, which is a mixer 13, and scrapers 7 for removing foam 8 in a pocket 10 (see diagram).

Similar experiments were carried out with a dose of sawdust: 3 mg _sawdust / mg _fat ; 11.7 mg _opil / mg _fat ; 18 mg _opil / mg _fat . The results of the analyzes are presented in table. 1.

As can be seen from the data presented, the dose of sawdust - 9 mg _opil / mg of _fat is the lowest dose at which a significant cleaning effect is observed. With a dose of sawdust of 11.7 mg _descriptions / mg of _fat , the maximum degree of purification from suspended solids and fats is achieved. A further increase in the dose of sawdust practically does not increase the degree of purification.

 From the table. 1 it can be seen that the use of electroflotation allows you to increase the cleaning effect from 92 to 95% and to obtain a foam product of lower humidity (80%) than with pneumatic flotation (98%), which reduces the amount of sediment processing facilities.

 Removal of sawdust from the flotation unit with pneumatic flotation -5%, with electroflotation - 2%.

Example 2. Carried out under the conditions of example 1. In this case, the initial stock has the following composition: fat - 100 mg / l, suspended solids - 190 mg / l, BOD ₂₀ - 130 mg O ₂ / l. The dose of sawdust was 30 mg of _sawdust / mg of _fat .

To determine the optimal dose of sawdust for DM with an initial fat concentration of 100 mg / l, similar experiments were conducted with a dose of sawdust of 40 mg _opil / mg of _fat and 60 mg of _opil / mg of _fat . The results of the analyzes are given in table. 2.

The maximum effect is observed with a dose of sawdust 40 mg _opil / mg _fat . With a dose of sawdust over 40 mg _opil / mg _fat, the cleaning effect is reduced.

The degree of purification from fats at a dose of sawdust of 40 mg _opil / mg of _fats and an initial concentration of fats of 100 mg / l is 52%, which is significantly lower than with pneumatic flotation in example 1 (92%). This is due to the fact that in Example 2, almost all fats are in a dissolved and emulsified state and it is very difficult to isolate them from water.

 The use of electroflotation gives a significant improvement in fat removal (61%), compared with pneumatic flotation (52%).

 The moisture content of the flotation concentrate is 98% and 96.7% for pneumatic flotation and electroflotation, respectively.

Example 3. Carried out under the conditions of example 1. The initial wastewater has the following indicators: fats - 6200 mg / l, suspended solids - 3800 mg / l, BOD ₂₀ - 2500 mg O ₂ / l. The dose of sawdust is - 3 mg _sawdust / mg of _fat .

Similar results were carried out with doses of sawdust 10 mg _opil / mg _fat , 20 mg _opil / mg _fat . The results of the analyzes are given in table. 3.

The optimal dose is sawdust, equal to 10 mg _opil / mg of _fat . The degree of purification from fats is: with pneumatic flotation - 96%, with electroflotation - 97.6%.

It can be seen from the above examples that, to achieve a cleaning effect of at least 50%, the optimal dose of sawdust is different and depends on the initial concentration of fats and corresponds to the range of 40 mg _opil / mg of _fat > C _opil ≥ 10 mg _opil / mg of _fat at a concentration of fat of 60 mg / l ≤ C _w <6200 mg / L, respectively.

Example 4. CB, purified in a pneumatic flotator, is fed into a filtration column with a diameter of 70 mm and a height of 25 cm. The waste liquid has the following parameters: fats - 240 mg / l, suspended solids - 179 mg / l, BOD ₂₀ - 500 mg O ₂ / l The filtration rate is - 4.5 m / h. Consumption - 0.29 l / min.

 As a filter load, a material is used consisting of a mixture of sawdust (particle size 0.5-2.5 mm) and coal ash (particle size 0.08-2 mm). All components are mixed until a uniformly distributed sorbent is obtained. Water is supplied to the column from top to bottom. The filter cycle was 24 hours.

 The results of the cleaning of CB in the filtration column are given in table. 4.

 As can be seen from the table. 4, the optimal ratio is 2.5: 1 (sawdust and ash, respectively).

Example 5. According to the technological scheme (see the diagram), CBs are supplied to mechanical grill 2 in an amount of 24 m ³ / day, having the following composition: BOD ₂₀ - 2500 mt O ₂ / l, fats - 6200 mg / l, suspended solids - 3800 mg / l. After detaining large suspensions on the grates, the drain enters the mixer 13 of the flotator 6, and the delayed suspension is crushed in a crusher 46 and sent to the tray in front of the grate.

 A tissue aerator 9 is installed in the pneumatic flotator.

In the mixer 13 of the flotator, the effluent is mixed with sawdust, which is fed through dispenser 14. The dose of sawdust is 10 mg _opil / mg of _fat .

 The resulting mixture was floated for 45 minutes. At the same time, the foam leaves: fat - 89%, sawdust - 92%, suspended solids - 5%; precipitates in the sediment: fat -7%, sawdust - 5%, suspended solids - 90%; it is taken to the next cleaning stage: fat - 4%, sawdust - 3%, suspended solids - 5% (for 100%, the initial concentration of each parameter is taken, respectively).

After flotation, purified water enters the filtration column. The flotation concentrate formed in the flotator, in an amount of 7.1 m ³ / day, enters the decanter 30, and the sediment with a flow rate of 0.1 m ³ / day is daily discharged through line 16 to aerobic digestion. If the flotation concentrate and sediment are not timely removed, secondary water pollution occurs.

After 60 minutes of settling from the decanter, decanted water with a flow rate of 6.8 m ³ / day is returned to the head of the structures via pipeline 31, and the fat mass with sawdust of 0.3 m ³ / day is sent to anaerobic digestion.

SV after flotation have the following indicators: suspended solids -179 mg / l; fats - 240 mg / l; BOD ₂₀ - 500 mg O ₂ / L.

 The loading of the filter column is a mixture of sawdust (particle size 0.5-2.5 mm) and ash from the combustion of coal (particle size 0.08-2 mm), taken in a ratio of 2.5-1, respectively. Filtration speed - 4.5 m / h. The filter cycle time is 24 hours. After the completion of the filter cycle, the load was removed or sent to anaerobic digestion 33.

Anaerobic bioreactor 33 is a metal tank swinging digester with a volume of 3.5 m ³ . The swinging digester works as follows:
sludge loading and unloading are carried out simultaneously once or twice a day. To do this, the tank is fixed in the "dead" position of the swing point and the loading and unloading hoses are connected. The sediment loaded into the upper end displaces by hydrostatic pressure the sediment discharged from the lower end in an amount equal to the volume of the loaded sediment. The drive of the digester is reversible with phase reversal at the “dead” rocking points. The transmission of rotation is carried out by a worm gear transmission with a washout of the power supply in the "dead" points for braking.

In the bioreactor 33 are subjected to fermentation of sediment and grease from the flotator, as well as loading sorption from the column 17 for 8 days. After completion of the anaerobic treatment, BOD _{20 of the} mixture is reduced by 83%.

 Fermented sediments are directed to aerobic stabilization and then to vacuum sludge pads 40 (pad size a x b = 1 x 1 m). The moisture content of dehydrated precipitation is 86%. Precipitation after silt sites are sent to prefabricated boxes, where they are processed by worms.

After filtering SW in the amount of 23.3 m ³ / day with a concentration of suspended solids - 22 mg / l, BOD ₂₀ - 150 mg O ₂ / l, fats - 1087 mg / l were sent (after the cost averager) to the biological treatment plant. The installation consists of three bio-drums of purification 22, a thin-layer module 23 and three bio-drums of post-treatment 24. The residence time at the first stage of the plant is 22–8 hours. The composition of SV at the output is as follows: suspended solids - 10 mg / l, fats - 2 mg / l, BOD ₂₀ - 20 mg O ₂ / l.

 The next stage of wastewater treatment — tertiary treatment and disinfection — is carried out in the tertiary treatment unit 24, made in the form of three bio-drums with a ruff loading, and the contact device 26. The residence time in the tertiary treatment unit is 10 hours.

 In the contact device, the treated effluent is mixed with a solution of bleach for 30 minutes.

Purified CB has the following composition: suspended solids - 3 mg / l, BOD ₂₀ - 3 mg O ₂ / l, fats - 0 mg / l; water is colorless, transparent, odor is at the threshold of sensitivity.

 Precipitation from a biological treatment plant, as well as regeneration water and fermented precipitation, was sent to an aerobic mineralizer 35. After three days of stabilization, the sludge contained 60% ash-free substance and 50% of suspended solids from their initial concentration.

 Stabilized sludge after compaction for 4-6 hours in the sludge compactor 37 was sent via line 39 to the vacuum sludge pads 40. The moisture content of the dehydrated sludge was 86%.

 Nadilovaya water from the seal 37 and the vacuum sludge pads 40 through the pipe 38 was sent to the flow averager.

Example 6. The sediment dehydrated on a vacuum sludge pad was loaded into a worm bed. The load was 0.02 m ³ / m ^{2 of} surface per day. Indicators of biohumus after a three-week treatment are given in table. 5.

Similar experiments were carried out with a load on the bed - 0.005 and 0.05 m ³ / m ² surface per day. The results are shown in table. 5.

From the table. Figure 5 shows that the optimum load is 0.02 m ³ / m ^{2 of} surface per day.

 Using the proposed method allows to increase the cleaning effect of SV meat processing plants without the use of special reagents, chemical additives, as well as to reduce the volume of structures as a whole, to solve the problem of utilization of precipitation, to reduce capital, operational and energy costs compared to the prototype by 20-60%.

Claims (5)

 1. The method of purification of fat-containing wastewater, including filtration, flotation with a sorbent and sedimentation, characterized in that a vegetable sorbent is introduced into the drain passing through a grate and a grease trap, the mixture is subjected to pneumatic flotation or electroflotation, filtered through a sorption charge and sent to the averager and further into the multistage biological treatment unit by the communities of attached and free-floating microorganisms; Precipitates formed at all stages of water purification, flotation concentrate, regeneration water, used filtration charge are sent to the sediment recovery unit, where after anaerobic-aerobic treatment, thickening, as well as exposure to vermiculture of worms, they are converted into organic-mineral fertilizer for farmland.  2. The method according to claim 1, characterized in that the sediment is fermented to produce biohumus.  3. The method according to claim 1, characterized in that only sediment, flotation concentrator of flotators, as well as the filtration mixture, are subjected to anaerobic treatment.  4. The method according to claim 1, characterized in that the filtrate from the thickening of aerobically stabilized sediments is sent to the averager. 5. The method according to p. 1, characterized in that the vermiculture of the worms of aerobically stabilized and thickened sediments is carried out in the beds with a load of 0.02 m ³ / m ² surface per day.

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