Wastewater from the starch and syrup industry. Wastewater treatment of potato-starch factories

Hydrocyclones GP-100, GP-300 have proved to be positive for separating sand from water. With a corresponding increase in their size, they can purify transport-washing water from sand, thus eliminating expensive sand traps and settling tanks.

Wastewater treatment of potato-starch factories in aerotanks is rare. Job Research different types aeration tanks indicated the feasibility of using aero< тенков-смесителей. Так при дозе активного ила 4 г/л п периоде аэрирования 6—8 ч снижение БПК гарантируется па 95% без снижения рН поступающих сточных вод. Метод биосорбции дает снижение ХПК на 80% при продолжительности контакта 1 ч и времени реаэрации 6—8 ч.

The mechanism of starch removal using activated sludge was investigated in a pilot plant under contact conditions. The active PL was adapted to starch and some other substrates. The activated sludge and starch solution were poured into an aerated vessel and aerated for 7 hours. The initial starch concentrations and sludge activity in the waste liquid varied within wide limits.

The installation systematically determined changes in the concentration of COD, starch, activated sludge, as well as the rate of decrease in the COD of the substrate without activated sludge. In the latter case, after some time of contact of the substrate with activated sludge, the sludge water was filtered and incubated without aeration. The decrease in the COD of the filtrate was due to the action of starch-degrading exoenzymes released by activated sludge. As a result of the carried out complex of studies, the following was established:

a) the rate of decrease in the COD of the substrate with activated sludge adapted to starch was in the range of 0.25-0.70 g, COD / g of activated sludge in 1 hour;

b) the rate of decrease in COD with activated sludge adapted to glucose, maltose and albumin was significantly lower and amounted to 0.1-0.27 g / g per hour;

c) the rate of decrease in COD without activated sludge was insignificant and amounted to 0.2-9% of the rate of decrease in COD with activated sludge. This is due to the fact that only an insignificant part of exoenzymes is released from the sludge water, and most of them are sorbed on bacterial cells;

d) in all experiments, it was noted that after mixing the substrate with activated sludge, a part of the substrate was immediately adsorbed on the activated sludge, and the amount of sorbed starch was in direct proportion to the temperature, the amount of activated sludge and its acclimatization.

The most effective way to treat wastewater from potato-starch enterprises is to utilize it in filtration fields. However, the increased concentration of pollutants in potato-starch wastewater used for irrigation in filtration fields requires a decrease in the load on these types of structures in comparison with domestic wastewater by 1.5-2 times.

When using wastewater from enterprises of the starch and syrup industry in irrigation fields, it is recommended to load 12,000-15,000 m3 of wastewater per hectare for the period of operation of enterprises (about 120 days). Thus, the daily load per hectare will be 100-125 m3 / day. In this case, waste water used for irrigation of crops must be pre-treated. When using wastewater from a starch plant for irrigation during the growing season, it must be averaged, neutralized, and diluted by a factor of 1.5-2. When organizing irrigation fields, it is necessary to select the most effective neutralizing substances and provide for the construction of mixing tanks with a neutralization installation and supply river water for dilution. For dilution, conveyor wash water can be used. If wastewater is used during the non-growing season, dilution is not necessary.

Due to the fact that the juice waters contain nutrients necessary for plants, these waters can be recommended for irrigation as liquid fertilizers. Comparative characteristics nutrients of juice water and manure are given in table. 29.

Table 29. Comparative characteristics of fertilizing qualities of juice water and manure

Compared to mineral fertilizers 100 m3 of juice water in terms of nutrient content is equivalent to about 17 centners of ammonium sulfate, 5 centners of superphosphate and 10 centners of calcium chloride. Characteristic feature these wastewaters are rapidly decaying, so their accumulation and storage is impossible.

Watering of herbs is the most rational. When watering grasses, along with an increase in yield, an increase in the protein content in hay from 12.3 to 20.3% (without the introduction of additional fertilizers into the soil) is also noted. When watering other crops, an increase in protein content was observed in fodder beets, corn, and carrots. Although the starch content in potatoes and sugar in beets irrigated with juice wastewater did not increase in percentage terms, and in some cases even decreased, the absolute yield of starch and sugar per hectare of irrigated area increased due to the high yield.

The use of juice water for irrigation has shown high efficiency in watering potatoes and oats. At the same time, the optimal irrigation rates were determined: for potatoes - 500 m3, for oats - 300 m3 of juice water per 1 ha.

Optimum irrigation irrigation rates in light sandy loam soils when watering starch plants with juice water, m3 / ha:

1. Perennial herbs - 8000
2. Corn and sunflower for silage - 4000-8000
3. Sugar and fodder beets - 4000
4. Cabbage - 4000
5. Potatoes - 2000
6. Cereals - 1000

Wastewater from the enterprises of the starch and syrup industry, even with satisfactory mechanical treatment when discharged into water bodies, creates conditions under which the oxygen regime is disturbed, and, as a result, the multiplication of fungi, their growth, decay with intensive formation and release of hydrogen sulfide.

The negative effect of potato-starch factories discharged into water bodies is expressed in the intensive absorption of oxygen from the water of reservoirs due to organic, biochemically oxidizing contaminants, in the formation of a sediment that easily turns into a putrefactive state, with the release of hydrogen sulfide, mercaptan, the development of fungal fouling on the bed reservoir and deterioration of the organoleptic properties of water.

There are cases when, due to intensive pollution of water bodies, they came to a state unsuitable for water supply and cultural and domestic purposes.

Bacti - Bio 9500 (Bacti Bio 9500) - granular bacterial concentrate for complete and intensive decomposition of organic matter and sediments.

APPLICATION:

Wastewater treatment systems - septic tanks, sand traps, sludge tanks, wastewater treatment plants Sewage networks and sanitary systems - sinks, toilets commercial enterprises - restaurants, bistros, canteens, shops

DESCRIPTION:

Bacti-Bio 9500 is a powder concentrate formulated for the degradation of a wide range of substrates. Numerous microbial strains of Bacti-Bio 9500 are uncultivated and non-pathogenic. Selected strains are active producers of enzymes: amylase (decomposition of starch), protease (decomposition of proteins), cellulase (decomposition of cellulose), keratinase (decomposition of keratin), lipase (decomposition of oils and fats), etc. Several cultures synthesize biological surfactants ...

CHARACTERISTICS:
Bacti-Bio 9500 is a white powder. The pH range is 6.0 to 9.0 with an optimum of 7.5. The most effective temperature range is 25oC. up to 55oC (77oF - 131oF) with an optimum temperature of about 30oC. Bacti-Bio 9500 also contains biodegradable surfactants that aid in the cleaning process. Bacti-Bio 9500 contains at least 2 billion cells per gram.

BENEFITS:
Fast and deep action due to the combined action of bacteria, enzymes and nutrients. Complete removal of fats and other organic deposits from sewerage networks and treatment facilities. Fast start-up of treatment facilities. Enables cleaning systems to run better and longer without maintenance. Keeps sewer networks clean. Controls gas evolution (eliminates unpleasant odors). Long independent existence in cleaning systems.
Non-toxic and safe in contact with skin. Fats and organics

STANDARD DOSAGE

Dose of biological product Bacti-Bio 9500 (ratio 1: 100) 5-7 min. dissolves in a bucket of warm water (+30 + 40 ° C) and kept for 10-15 minutes. to reactivate bacteria. After that, the contents are poured into the processed system.

1. Septic tanks, sand traps, sediment containers. Application of the first dose: 50 g / m3 is applied directly to the container. Regular maintenance: 6 g per 1 m3 of septic chamber volume every two weeks. We recommend injecting the biological product more often or increasing the dose if an unpleasant odor appears or the sediment does not decompose sufficiently.

2. Sewer networks. In order to avoid clogging and unpleasant odors, it is necessary to inject 1 dose (50 g) per 3 drain holes of the sewer network. After a month, repeat the treatment. In the future, apply as the sewer pipes become clogged.

3. Commercial enterprises. Service dose commercial enterprises determined based on the number of meals: up to 250 meals / day 50 g / month, 250 - 500 meals / day 100 g / month, more than 500 meals / day 150 g / month

Treatment facilities:

Drip filters - 1.5 - 3 kg per 3780 m3 of effluent are introduced through the siphon of the structures. If necessary, the initiating dose is re-administered after 48 hours. For service use 0.75 - 1.5 kg of the preparation per 3780 m3 of waste water. In well aerated aeration tanks 0.75-1.5 kg per 3780 m3 of waste water. Due to the high efficiency of the drug, the hydraulic delay time is significantly reduced. Sludge is processed separately. Aerobic digesters - 0.5 kg per week for 330 m3 of sludge. If there is a significant layer of fat, double the dose. Anaerobic reactors, sludge pads - the dosage is about the same as in aerobic ones. The product works in harmony with methanogens and enhances methane production.

Small sewage treatment plants

Sediment tanks - 0.25 - 0.5 kg per week for every 330 m3 capacity.

Two-level sedimentation tanks - 0.25 - 0.5 kg per week for every 330 m3 of capacity. Periodic stirring is recommended.

Lagoons, post-treatment ponds (with and without aeration) - to remove odors, reduce the amount of silt, and accelerate sedimentation, introduce 0.25-1 kg per 200 m3. The powder is sprayed onto the surface of the water and injected through a wet well.

Collector lifting stations, sewer pipes and collector lines
0.4 kg per 165 m3 of effluent is injected directly into the drain holes.

BENEFITS

With anaerobic and anaerobic fermentation of sludge, decomposition will occur more completely, dehydration will be simplified, and the amount of mineralized nutrients will increase.

BIOLOGICAL CLEANING PROGRAM

The success of any biological treatment program depends on favorable operating conditions and activities. During the microbiological cleaning period, ongoing monitoring is required to ensure that necessary conditions action. The dose and frequency of drug administration are specific to each individual biological treatment program.
The specifics of each situation should be analyzed in detail before designing a corrective program.
A cleaning program will typically include a higher startup dose and a maintenance dose. Determination of the optimal dose is usually carried out on site, reducing the frequency of dosing gradually until there is a deterioration in the effectiveness of the drug.

Chapter 15

STARCH AND STARCH PRODUCTS TECHNOLOGY

The modern starch and syrup industry is an important branch of the national economy. Processing potatoes and corn, starch and syrup enterprises produce dry starch, glucose, various types of starch syrups, modified starches, dextrins, glucose-fructose syrups, etc. The range of products produced is dozens of names. Starch and starch products are used in various industries Food Industry: confectionery, bakery, canning, dairy, food concentrate, etc., as well as in other industries (medical, textile, printing, paper, etc.).

TECHNOLOGICAL SCHEME OF OBTAINING RAW POTATO STARCH

The raw material for the production of potato starch is potatoes. The chemical composition of potato tubers varies within fairly wide limits and depends1 on the potato variety, climatic, soil and other conditions. Average chemical composition of potatoes (%): water - 75, dry matter - 25. Of these (%): starch - 18.5, nitrogenous substances - about 2, fiber -

1, minerals - 0.9, sugars - 0.8, fat - 0.2 and other substances (pectin, pentosans, etc.) - 1.6.

The basic technological scheme for obtaining raw potato starch (Fig. 51) consists of the following stages: storage of potatoes; delivery of potatoes to the plant; washing potatoes in washing machines; weighing potatoes; fine grinding of potatoes on grating machines - getting porridge; extraction of potato juice from porridge; the release of free starch from the porridge; separation and washing of the pulp; refining of starch milk; rinsing starch.

Potato storage. Potato processing plants operate seasonally. Before serving for production, the harvested potatoes are stored in piles at a temperature of 2 ... 8 “C. Only healthy tubers are laid for storage. When stored, potatoes breathe. It is impractical to store potatoes for more than 5 ... 7 months, as this leads to significant losses of dry substances, including starch.

Delivery of potatoes to the plant. Potatoes are fed to production using a hydraulic conveyor (feeding is carried out in the same way as feeding sugar beets in sugar beet production), while light impurities, sand and earth are partially separated.

Washing and weighing potatoes. This process is very great importance, since at subsequent stages the potatoes are not peeled, and the presence of mineral impurities in the starch is unacceptable.

Potatoes are washed in combined type washing machines with chambers with a high water level, where straw and other light impurities are separated; chambers with a low water level, in which they scrub the ground well; dry chambers in which water, without lingering, flows into a mud ditch. Washing machines are equipped with tops, sand and stone traps. At large factories, the KMZ-57M washing machine has become widespread. The duration of the washing process is
10 ... 14 minutes, water consumption - 200 ... 400% to the mass of potatoes.

To account for the mass of processed potatoes, the washed tubers are weighed on an automatic scale with a folding bottom.

Grinding potatoes on grating machines - getting porridge... Starch is contained within the cells of potatoes in the form of starch grains. To remove it, it is necessary to open the cell walls. To do this, potatoes are crushed on grating machines, the principle of which is to abrade the tubers with a surface made up of fine-toothed saws. Grinding is carried out twice. For the first grinding, files with a tooth height of 1.5 ... 1.7 mm are used, for repeated (fume) - 1.0 mm. The grinding quality is characterized by the grinding ratio K.

On the modern enterprises the grinding ratio reaches 85 ... 95%, including 79 ... 85% during the first grinding to 6 ... 10% during grinding.

Isolation of potato juice from porridge... The potato gruel obtained after grating machines is a mixture of torn cell walls, starch grains and potato juice. An important task of obtaining potato starch is the fastest extraction of juice from the porridge with minimal dilution. Contact of juice with starch worsens the quality of starch, causing it to darken due to oxidation of tyrosine, reduces the viscosity of starch paste, promotes the formation of foam, mucus and other undesirable phenomena. Potato juice is isolated from the gruel in the settling screw centrifuges.

The OGSh-type auger settling centrifuge (Fig. 52) consists of an outer 2 and an inner 3 drums with a screw 1 welded to the drum 3. Both drums rotate in one direction, and the inner one is 15 ... 25 s-1 ahead of it. The potato drip, passing the centrifuge, through the pipe 6 and the hollow shaft 4 enters the space between the drums through the windows 7. Here, under the action of centrifugal force, it is divided into two fractions.

Potato juice is removed from the centrifuge through the drain windows 8, and the sediment (heavy fraction) due to the difference in the rotation of the drums is removed by the screw 1, diluted with water and removed through the windows 5 in the form of starch milk of a certain density.

Condensed porridge with a dry matter concentration of up to 40% is obtained with minimal losses of starch with potato juice (0.1%).

Rice. 52 Screw sedimentation centrifuge, type OGSh

Isolation of free starch from the porridge, separation and washing of the pulp... After the separation of the potato juice in sedimentation centrifuges, the gruel is sent to the sieve station of the plant. Here, on various sieve machines, coarse and fine pulp is separated and washed from it, starch is precipitated and washed. The use of hydrocyclone units for separating finely ground potato gruel into starch suspension and a mixture of pulp with potato juice is very promising. However, at present, centrifugal sieves are used to isolate the pulp from the gruel: drum-jet (BSS) or centrifugal-blade (CLS).

Drum-jet sieve (Fig. 53) consists of a rotating perforated conical drum 2, on the inner surface of which metal frames are attached in the form of sectors covered with one or two meshes of different sizes. The cup is fed through the pipe / and feeder 8 to the top of the sieve cone. The drum rotates at a frequency of 900 s "1. Under the action of centrifugal force, the gruel is evenly distributed over the inner surface of the drum and moves to its larger base. Water or liquid starch milk is fed towards the movement of the gruel through shaft 5, which rotates inside the shaft 3. Jet rotor-sprinkler consists of a manifold 7 and spray nozzles 6. The drive 4 provides an advance of the rotation of the sprinkler rotor by 50 s-1 in comparison with the speed of rotation of the drum 2. Water under a pressure of 0.2 ... 0.25 MPa forms against the movement of porridge as would be a water speck, delaying its progress on the sieve and contributing to the washing off of free starch.

Rice. 53. Drum-jet sieve

The centrifugal blade sieve CLS (Fig. 54) resembles a centrifugal pump in its structure. The impeller blades are replaced by sieve plates, concave in the direction of rotation. There are three small chambers under each sieve. The cake through the pipe 3 through the slotted holes 1 enters the rotor 2 under pressure, which develops due to centrifugal force, and flows through the sieves 5. The starch milk is filtered, enters the chambers located under the sieves, and is discharged through the holes 6 in the fixed wall 4. Pulp moves along the surface of the sieves from the center of the apparatus and is thrown out under the rotor. To wash the free starch, the gruel is sequentially processed on a drum-jet and centrifugal-blade sieve machines and sent for re-grinding (grinding), after which it is washed again at the BSS and CLS. After the separation of the pulp on sieves or hydrocyclones, the starch suspension contains a certain amount of fine pulp (4 ... 8%), water-soluble substances
(0.1.-0.5%) and highly diluted potato juice. Therefore, it is refined on centrifugal sieves, hydrocyclones or arc sieves. The concentration of the starch suspension entering the refining should be 12 ... 14 and the concentration of the refined suspension should be 7-9%.

Refining starch slurry... Refining on centrifugal sieves is carried out in two stages, after which the starch suspension is fed to a defoaming device, and then to sand hydrocyclones to remove sand. The resulting thickened suspension is fed to hydrocyclones for starch washing, which is carried out in three stages. Next, the starch is dehydrated on vacuum filters and dried.

Hydrocyclones (Fig. 55) are a battery of microhydrocyclones. The principle of operation of these devices is simple. Starch milk under a pressure of 0.15 MPa enters the apparatus tangentially along a tangent along pipe 2, due to which the translational movement of the product is converted into rotational, a large centrifugal force develops, as a result of which heavy particles are thrown onto the inner surface of the cone and slide down to the nozzle of the condensed descent 1. The light fraction of the product (liquid descent) is displaced by the thickened fraction, rises to the nozzle of the liquid descent 3 and is removed from it. The dimensions of microhydrocyclones depend on the size of the particles of the mixture to be separated. In potato starch production, microgmdrocyclones with an inner diameter of a cylindrical part of 20 mm, a cone height of 92 mm and a cone angle of about 12 ° are used. The diameter of the inlet circular nozzle is 3.3 mm. The productivity of one microhydrocyclone is low, therefore they are combined into multicyclones - batteries of hydrocyclones, consisting of a large number of microscopic cyclones operating in parallel. Hydrocyclone stations SG-4M1 (with a capacity of 100 t / day of potatoes) and SG-5 (with a capacity of 200 t / day of potatoes) operate at the production site.

Refining starch slurry
can also be carried out on meadow sieves. A low-pressure meadow sieve of the RZ-PRD brand (Fig. 56) consists of a sieve surface 3, fixed on a frame inserted into the body I Product under low pressure

through the feeder 2 comes from the top to the sieve surface. The starch suspension passes through the sieve and is collected in the housing 1, and the pulp slides into the lower part of the sieve surface and is removed from it.

The starch suspension refining process is carried out in two stages.

Fine pulp is washed on sieves in three stages. To obtain starch milk of a sufficiently high concentration, diluted starch milk is repeatedly used at the sieve station of the plant, and the process is carried out according to the counterflow principle.

Fig. 54. Centrifugal blade sieve CLS

Starch yield and recovery factor... The yield of potato starch is the ratio of the resulting starch to the mass of processed raw materials, expressed as a percentage. The output of starch depends on its content in the processed raw materials and losses with pulp and wastewater. On average, the starch yield is 15.7%, starch losses are 2.8%.

The ratio of the mass of the resulting starch to the mass of starch,

Quality of raw potato starch... Raw potato starch, depending on its moisture content, is divided into two grades: A (moisture content 38 ... 40%) and B (moisture content 50 ... 52%). The starch of each brand is divided into three grades. Its quality must meet the requirements of the industry standard OST 18-158. Starch of I and II grades must have a uniform white color and halls, characteristic of starch, the presence of an extraneous odor is not allowed. Grade III starch can be grayish, without streaks and inclusions, a slightly acidic, but not sour smell is allowed in it. Quality indicators of raw potato starch are given in table. 15.1.

Table 15.1

Due to the high moisture content, raw potato starch cannot be stored for a long time, it sour and therefore it is processed into dry starch, acid-free dextrins, modified starches, molasses, glucose, etc. If necessary, raw potato starch is stored for some time in bulk or in warehouses, ramming and filling it with water. The safest way is to keep it frozen. However, during storage in starch, microbiological processes occur, leading to the appearance of a sour odor, an increase in acidity, an increase in soluble substances and a decrease in starch dry matter.

Use of by-products... The most important tasks facing the starch-syrup industry are the complex and most complete use of potato dry matter in the production of starch from it, a decrease in the consumption of fresh

water for technological needs and, as a result, a decrease in the amount of wastewater that pollutes the environment.

By-products of potato starch production - pulp and potato juice. 15.7% of starch is extracted from 25% of dry matter of potatoes, the remaining 9.3% of dry matter is distributed approximately equally between the pulp and potato juice. Potato juice contains 5 ... 7% dry substances, which include up to 40% nitrogenous substances, 20 ... 25% soluble carbohydrates, 9 ... 12% mineral substances, 3 ... 5% starch, about 3 % fat. The nitrogenous substances of potato juice are 50% proteins, the juice contains up to 20 amino acids, including essential ones (lysine). Ash contains potassium oxide, phosphoric acid, calcium and magnesium salts. Found also iron, sulfur, chlorine, zinc and other elements.

The dry matter of the pulp consists (%): of starch - 45 ... 50, fiber - 25 ... 30, soluble carbohydrates - 25 ... 30, proteins -

5, minerals - 5 ... 6. With the aim of rational use the most promising is to process potato juice and pulp into a carbohydrate-protein hydrolyzate and protein feed. For this, a mixture of pulp and potato juice with a dry matter content of 8 ... 12% is boiled at a temperature above 100 ° C, as a result of which about 30 ... 40% of the protein substances of the juice coagulates. Then the mixture is cooled to a temperature of 62 ... 64 "C, an enzyme preparation is introduced and the starch pulp is saccharified for 2.5 ... 3 hours. The resulting reducing substances pass into the liquid phase. The mixture is filtered. The liquid phase is sent for boiling to a dry matter content of 50%. The resulting carbohydrate-protein hydrolyzate is a thick brown liquid with a pleasant odor. It contains glucose, maltose, sucrose and a number of amino acids. The hydrolyzate can be used in bakery as a substitute for red rye malt when baking certain types of bread, and also as a biostimulator when growing fodder yeast.

Purpose of the study: study the fertilizing value of wastewater from the food industry. This category of wastewater is very diverse; enterprises are located throughout Russia. For the production of their products (sugar, starch, molasses), these enterprises consume a large amount of water. Unlike many enterprises, sugar factories are concentrated in the southern and southwestern parts of the country, in the zone of black earth soils. Wastewater treatment is carried out in most factories in filtration fields. But wastewater treatment is unsatisfactory.

The peculiarity of sugar production is that the resulting wastewater is characterized by a high content of suspended sludge, has an acidic reaction with a high content of sodium salts. Sugar factories have two types of wastewater: conditionally clean and industrial chemically contaminated wastewater.

The first of them are discharged into open water bodies (rivers), the second are sent to treatment facilities (filtration fields or artificial biological treatment facilities). The fertilizing value of unclarified wastewater is average, phosphorus is almost absent.

A huge amount of earthy-lime sediment is formed when lime is used in production technology (clarification of sugar syrup), it easily settles, the water is clarified, and its composition improves. Clarification of wastewater from sugar factories is carried out in earthen ponds - sedimentation tanks. After clarification, wastewater is directed and accumulated in the maps of filtration fields. After settling in the filtration fields, the wastewater becomes alkaline, the reaction of the medium approaches neutral or slightly alkaline. The suspended sediment content is slightly reduced, and the concentration of dissolved substances reaches optimal values.

Wastewater from starch and starch factories

These plants are located in all soil and climatic zones, from the zone of soddy-podzolic soils to chernozems and chestnut soils. The raw materials for production are potatoes and corn. So far, the treatment and disposal of wastewater at these plants has not been fully resolved. Most factories discharge untreated or poorly treated water into rivers, as a result of which they are pollutants of surface and ground waters. At the same time, wastewater from starch factories is a source of fertilizers and, in this regard, is of interest to Agriculture.

Wastewater from potato starch production is characterized by a high content of sludge from various organic substances, including organic acids. This wastewater quickly turns sour. In the production of corn starch, sulfuric acid, sometimes soda alkali, is used to hydrolyze corn grain. As a result, the effluent from corn starch plants is acidic. Wastewater from starch factories and plants is divided, taking into account the technological process, into two types: conveyor-washing and juice-washing. At a number of enterprises, they are combined into a common stock.

As a rule, wastewater from starch factories has a slightly acidic and acidic reaction, they are characterized by an increased content of solutes and a bicarbonate composition. Calcium salts predominate in the composition of salts, but sodium salts are predominant in the production of corn starch by the alkaline method.

All types of wastewater from starch factories, except for conveyor-washing and re-washing, are characterized by a high content of organic substances. The fertilizing value is high in potassium and nitrogen. General runoff and conveyor-washing waters contain significantly less nutrients. The composition of waste water from starch factories varies significantly during the day and day after day. Waste water is suitable for irrigation after averaging and dilution with clean water or conveyor-washing water. The plant's overall flow is usually the best composition for regular irrigation purposes.

Waste water from hydrolysis and biochemical plants.

Hydrolysis and biochemical plants produce fodder yeast. The raw materials for their production are agricultural waste (corn stump, husk) and forestry (wood waste). Hydrolysis plants are located throughout Russia, including the eastern and northern, western and southern regions of the country.

The waste water from these factories is quite distinctive. They are distinguished by their high color (brownish-brown color), the presence of a finely dispersed suspended sediment, an acidic and slightly acidic reaction of the medium, a high content of ammonia nitrogen, sulfates and organic substances. These features are determined by the production technology. To obtain biomass, agricultural waste is hydrolyzed with sulfuric acid. Neutralization of acidic effluents from the main stages of the technological process is carried out ammonia water.High color, the presence of fine sediment, high content of organic matter are caused by the effect of sulfuric acid on the biomass.

Waste waters of these enterprises in their initial state (before treatment) are characterized by an acidic reaction of the environment, a significant content of suspended sediment, a high concentration of dissolved substances, and a sulfate-bicarbonate composition. The composition of the salts is dominated by calcium salts. Wastewater has a high concentration of dissolved substances, which varies widely. More than 50% of the dissolved substances are organic substances.

The reaction of the medium becomes less acidic, the content of solutes in suspended sediment, organic matter, including sulfates and biogenic elements, decreases by more than 50%. This pattern is manifested under the influence of artificial biological treatment. At some enterprises, artificial biological treatment facilities do not ensure that the composition of wastewater is brought to a condition suitable for discharge into water bodies. The cleaning effect reaches 60%. Remains color, high content of biogenic elements, organic matter and sulfates. After biological and mechanical cleaning wastewater from hydrolysis plants becomes suitable for irrigation of crops.

Wastewater from creameries and creameries

Enterprises for the production of butter, cheese and primary milk processing are mainly concentrated in the non-black earth zone of Russia, covering such regions as the central regions, as well as the southern regions of the non-black earth zone of Russia. The bulk of these enterprises are located in the zone of sod-podzolic, gray forest and leached chernozem soils.

Dairy enterprises are extremely diverse in terms of capacity and, therefore, in terms of the volume of wastewater generated. Medium and small enterprises prevail. Medium-sized enterprises annually discharge about 200 250 thousand m 3 / year of untreated or poorly treated waste water into water bodies.

Small enterprises discharge up to 50-70 thousand m3 / year of wastewater. Wastewater from milk processing plants is very unique. They contain many organic substances, including many protein compounds, which quickly rot and lead to air pollution. Wastewater is characterized by a high content of fertilizing elements (nitrogen, potassium). Therefore, they are of interest to agriculture as a source of fertilizers.

No toxic substances are used in the production technology. A certain danger is posed by effluents from salting cheeses, where a highly concentrated solution of sodium chloride (No. 01) from 20-25% is used. These effluents are generated in creameries and are periodically discharged in small volumes into a common wastewater collector. As a result of these discharges, the total runoff is noticeably deteriorating in terms of many agromeliorative indicators. It is advisable to isolate these effluents from the total waste water of a number of dairy enterprises.

Tables 1 and 2 present data on the chemical composition and fertilizing value of wastewater from a number of dairy enterprises. On the example of OJSC "Nadezhda" of the Kovylkinsky oil and cheese plant of the Republic of Mordovia, which is a typical enterprise for the production of butter and cheese, data on the chemical composition of wastewater are given for the main cycles of the technological process and the total flow of the plant. At all stages of the technological process, the generated wastewater (fresh) has an acidic reaction, a high content of organic matter and biogenic elements.

The content of organic matter (COD) varies from 6.5 to 7.7 mgO / l, total nitrogen from 105 to 216 mg / l, potassium from 56 to 223 mg / l (excluding wastewater from salt pools), the amount of phosphorus 18-60 mg / l. Aggressive drains are typical for salt baths. These effluents are highly concentrated. They contain 25 g of dissolved salts, a lot of sodium salts (25.3 g / l) and organic compounds (3 g / l). Such effluents must be removed from the total wastewater volume.

The study of the chemical composition of the waste water of the Kovylka oil and cheese plant showed that the total flow of the plant from the storage ponds, where the waste water is stored and settled for a long time, is characterized by a more favorable composition. It has a neutral or alkaline reaction, a lower concentration of solutes (1.4 g / l), and a bicarbonate-chloride composition. Sodium salts predominate in the composition of salts. The fertilizing value and the content of organic matter are reduced, and the waters become suitable for irrigating crops. At this facility, wastewater from salt baths is removed by mobile transport, therefore, it is isolated from the total volume of wastewater.

Table 1. Chemical composition of waste water of OJSC "Nadezhda" of the Kovylkinsky oil and cheese plant of the Republic of Mordovia by main technological cycles, mg / l

Weigh. sediment

Dry residue

Calcined. remainder

Nitrogen total

Ammach nitrogen.

Waste water from equipment washing

Waste water from the boiler room

Runoff from cheese salting pools

Total runoff on the territory of the plant

Total flow of pump st. on the territory of the plant

Accumulator (total plant flow)

Average data for total stock (drive)

Table 2. Chemical composition and fertilizing value of waste water from dairy industry enterprises

Enterprises

Weigh. sediment

Dry residue

Proc-lostok

Total nitrogen

Nitrogen ammonia.

Torbeevsky

creamery

Krasnoslobod-

skiy creamery

Atashevsky creamery

Stavrovsky dairy plant

Table 2 presents data on waste water from other oil and butter-cheese factories. The table shows the composition of the total runoff of the creameries of the Republic of Mordovia and factories of the Vladimir region.

From the data in the table it can be seen that wastewater in its original state (before cleaning) is characterized by an increased content of suspended sludge, dissolved substances, including organic compounds and sodium salts. Wastewater requires preparation for irrigation before use. During the preparation process, wastewater should not have a high content of suspended sludge, organic compounds and fertilizing elements. Waters require averaging, settling, isolation of sodium salts. Considering that the waters of creameries have a high fertilizing value, it is advisable to use them for irrigation of agricultural crops and, first of all, fodder crops.

Having considered the chemical composition of the main categories and types of wastewater, taking into account the production technology, it can be concluded that wastewater from the food industry in its original state is characterized by a high content of suspended sludge, dissolved substances, organic compounds, an increased content of nutrients and some substances, the ingress of which into waste water is undesirable.

All types and categories of wastewater to one degree or another require preparation for irrigation. The nature and features of their preparation for irrigation are determined by the composition of wastewater, production technology, and the peculiarity of the natural conditions of the irrigated zone. By means of treatment, the waste water must be brought to a condition suitable for irrigation.

Wastewater from the starch and syrup industry

The enterprises of the starch and syrup industry include plants and workshops for the combined processing of potatoes for starch and alcohol, potato starch, corn-syrup and corn-starch plants, plants for processing potatoes for dry starch and corn for dry starch.

Wastewater at the enterprises of the starch and syrup industry is formed as a result of technological processes processing of raw materials from a hydraulic conveyor, washing raw materials and equipment, cooling apparatus, vacuum pumps, blowers, refrigerators, barometric condensers, etc.

The average annual amount of wastewater from the workshops for the combined processing of potatoes for starch and alcohol on mixed raw materials (potatoes and grain) per 1 ton of dry starch with a direct-flow water supply system is 137.7 m3, including 137.0 m3 - industrial and 0.7 m3 economically - household, and when working on potato raw materials costs are 200; 199.3; 0.7 m3, respectively. The coefficient of unevenness of the flow of sewage in summer and winter is equal to one.

At corn-syrup plants with a water reuse system, the average annual amount of wastewater per 1 ton of molasses is 34.06 m3, of which 4.52 m3 is industrial, 0.24 m3 is domestic and 29.3 m3 is relatively clean. The coefficient of unevenness of the flow of sewage in summer and winter is equal to one.

At corn-starch factories in the production of starch with direct-flow water supply systems for 1 ton of starch, the average annual amount of wastewater is 15.0 m3, of which 3.0 m3 of industrial, 1.5 m3 of household, 10.5 m3 of conditionally clean, and in the production of glucose with repeated use of water per 1 ton of glucose, the consumption of wastewater is 262.2 m3, including 5.8 m3 of industrial, 0.4 m3 of household and 256.0 m3 of conditionally clean. The coefficient of unevenness of the flow of sewage in summer and winter is equal to one.

During the processing of potato raw materials, conveyor and washing waters are formed, and during the processing of wheat, corn, rice, waste water from the pre-treatment of grain, i.e., water of locks or swelling as a result of chemical treatment of corn with sulfurous acid, and rice - with caustic soda.

Wastewater from the enterprises of the starch and syrup industry can be divided into four categories: trapsporter-washing, juice, washing and pressing.

Conveyor and washing waters are formed during hydrotransportation and washing of potatoes. Their number depends on the degree of contamination of the potatoes, the type of washing machines and is 1300-1400% of the weight of the processed potatoes. In relation to the total runoff of the plant, these waters account for 55%.

Pollution of the conveyor and washing waters of potato-starch factories consists of soil washed from tubers, small potatoes, tops, potato sprouts, and straw. The amount of contamination is 5-20% of the weight of the potato. When washing healthy potatoes, its dry matter is not washed out and is almost not lost, but it gives off suspended and soluble substances, and rotten and frozen potatoes give up part of the dry matter.

At the beginning of the raw material processing season, starch plants primarily process potatoes that are unsuitable for long-term storage: clogged, wet, frozen, damaged by rot. In winter, potatoes of the best quality are usually processed, and in spring - sprouted, affected by rot. This causes significant wastewater pollution in the autumn and spring periods of potato processing enterprises.

The amount of conveyor and washing wastewater is from 6 to 8 m3 per 1 ton of potatoes with a decrease to 5 in case of reuse on a hydraulic conveyor.

The amount of pollution in the conveyor and washing water, mg / l:

1. Earth (inorganic suspensions) - 750
2. Organic - 230
3. Inorganic soluble - 200
4. Organic soluble - 190
5. Nitrogenous substances - 150
6. BOD5 - 152

The composition of the transport and washing waters in different seasons work is not stable and is characterized by large fluctuations (Table 26).

Table 26. Wastewater composition, mg / l, Shatsk potato-starch plant (Belarus)

The conveyor and washing waters have a yellow-brown color, an earthy-potato smell; pH = 6.5; suspended solids — 950–30600 mg / l in autumn and 600–4700 in spring; BOD5 - 100-500 mg / l in autumn and spring, bichromate oxidizability 500-2000 mg / l in autumn and 300-1300 mg / l in spring.

The conveyor-washing waters and rinsing waters in the general complex of waste waters of potato-starch plants are diluting, since they contain lower concentrations of contaminants in comparison with juice press waters.

Juice waters represent the liquefied cell juice of potatoes. They are formed by separating starch in sediment centrifuges and washing it in hydrocyclones or washing vats. The amount of juice water is 7-12 m3 per 1 ton of processed potatoes and depends on the capacity of the plant.

Pollution consists of a large amount of organic soluble and insoluble substances capable of decay and fermentation, as well as a small amount of inorganic salts of potassium and phosphoric acid. Fermentation is a characteristic feature of this wastewater. In the process of fermentation, lactic, butyric acids are formed and an unpleasant odor is emitted. The fermentation process ends with decay with intense release of hydrogen sulfide.

Depending on the operating conditions of the enterprise, the concentration of juice water ranges from 0.6-1.0% -

The composition of dry substances of juice water includes up to 15% mineral, 35-40% nitrogenous and protein compounds, about 10% starch, 20-25% soluble sugars, 3% fat and up to 15% other substances.

By chemical composition juice water is an organic, mainly nitrogen-potassium fertilizer. According to the content of the main nutrients (nitrogen, potassium, phosphorus) 1000 m3 of juice water is equal to a mixture of 15 centners of ammonium sulfate, 5 superphosphate and 12 centners of 40% potassium salt. In addition to soluble substances, juice water contains no more than 0.015% pulp and starch.

The wash water is generated during the starch washing process. Their quantity is insignificant, 1–3 m3 per 1 ton of processed potatoes. The contamination content of the wash water is insignificant, since most of it leaves with the juice water. Contamination consists of potato soluble substances and relatively small amounts of fine pulp and starch particles.

Pressing water appears as a result of pressing the pulp by washing it. The amount of press waste water is 0.4-0.6 m3 per 1 ton of potatoes. The composition of the pollution of this wastewater is similar to that of the juice water.

The formation of the general flow of the enterprise, the nature and extent of pollution depend on individual technological processes, sources of wastewater formation, and their pollution. For example, the amount of wastewater from potato processing depends mainly on the peeling technology. When cleaning with caustic soda, wastewater has a pH of 10-11.

With the steam or abrasive method, this figure is much lower.

The specific consumption of wastewater per unit of the produced projection for factories operating on mixed raw materials (potatoes, grain) is 140 m3, and for potato plants - 200 m3 per 1 ton of dry starch.

In the production of potato starch, wastewater has suspended solids 1500-5000 mg / l, average mineralization 1800-3500 mg / l, bicarbonate-sulfate composition, acidic reaction of the medium, pH = 4.2-4.8. The average nitrogen content is 120 mg / l, potassium - 300, phosphorus - 15, calcium - 80 mg / l. The composition of wastewater is unstable, with a large amplitude of fluctuations.

The total runoff of enterprises processing potatoes for starch is characterized by the following size of contaminants: suspended solids 2500-18000 mg / l, BODb - 1100-1500 mg / l. In this case, the composition of suspended solids, mg / l, is: total amount 2824, including organic - 1454, total nitrogen - 265, phosphorus - 93, potassium - 486.

Wastewater from starch enterprises has a large amount of organic, biologically (biochemical) purified, contaminants. Their concentration of carbohydrates and proteins is higher than that of domestic wastewater. They are slightly transparent, in a fresh state they have a weakly alkaline and in rare cases acidic reaction of the medium. The decrease in pH can be attributed to the development of lactic and butyric acid fermentation in the wastewater. The decomposition of proteins is accompanied by the release of hydrogen sulfide.

Wastewater from the production of starch from corn, wheat, rice differs from wastewater from potato-starch production by a higher content of sodium salts and organic substances, a less acidic reaction of the environment, and a variable composition.

In the production of starch using corn as a raw material, wastewater is formed in the amount of 24-28 m3 per 1 ton of starch. This amount does not include waste water from grain pretreatment, i.e. from locks and swelling, as they are processed in evaporators with subsequent use for livestock feed or as a raw material for the production of penicillin.