Wastewater from starch and syrup industry enterprises

Enterprises of the starch and syrup industry include factories and workshops for the combined processing of potatoes into starch and alcohol, potato starch, corn syrup and corn starch factories, factories for processing potatoes into dry starch and corn into dry starch.

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

The average annual amount of wastewater from workshops for the combined processing of potatoes into starch and alcohol using 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 for production and 0.7 m3 for economic -household, and when working on potato raw materials the costs are 200; 199.3; 0.7 m3 respectively. The coefficient of unevenness of wastewater flow in summer and winter is equal to one.

At corn-molasses plants with a water reuse system, the average annual amount of wastewater per 1 ton of molasses is 34.06 l3, of which 4.52 m3 is industrial, 0.24 m3 is domestic and 29.3 m3 is conditionally clean. The coefficient of unevenness of wastewater flow in summer and winter is equal to one.

At corn-starch factories in the production of starch with direct-flow water supply systems per 1 ton of starch, the average annual amount of wastewater is 15.0 l3, of which 3.0 m3 is industrial, 1.5 m3 is household, 10.5 m3 is conditionally pure, and in the production of glucose with the reuse of water per 1 ton of glucose, the wastewater consumption is 262.2 l3, including 5.8 m3 industrial, 0.4 l3 household and 256.0 m3 conditionally clean. The coefficient of unevenness of wastewater flow in summer and winter is equal to one.

When processing potato raw materials, conveyor-washing waters are formed, and when processing wheat, corn, rice - wastewater from pre-processing of grain, i.e. soaking or swelling water as a result of chemical treatment of corn with sulfurous acid, and rice with caustic soda.

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

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

Contaminants in the conveyor and washing waters of potato starch factories consist 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, their dry matter is not washed out and is almost not lost, but it gives up suspended and soluble substances, while rotten and frozen potatoes give up some of the dry matter.

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

The amount of conveyor-washing wastewater ranges from 6 to 8 m3 per 1 ton of potatoes, decreasing to 5 in the case of reuse on a hydraulic conveyor.

Amount of contamination of conveyor and washing waters, 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 conveyor-washing waters in different operating seasons is not stable and is characterized by large fluctuations (Table 26).

Table 26. Composition of wastewater, mg/l, Shatsk potato-starch plant (Belarus)

Conveyor-washing waters have a yellow-brown color and an earthy-potato odor; 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, dichromate oxidation 500-2000 mg/l in autumn and 300-1300 mg/l in spring.

Conveyor-washing waters and wash waters in the general wastewater complex of potato-starch factories are diluting, since they contain lower concentrations of contaminants compared to juice press waters.

Juice waters are liquefied cell sap of potatoes. They are formed by isolating starch in sedimentary centrifuges and washing it in hydrocyclones or washing tanks. 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 number of organic soluble and insoluble substances capable of rotting and fermentation, as well as small quantity inorganic salts of potassium and phosphoric acid. Characteristic feature This wastewater is fermented. During the fermentation process, lactic and butyric acids are formed and an unpleasant odor is released. The fermentation process ends with rotting 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 matter in juice water includes up to 15% minerals, 35-40% nitrogenous and protein compounds, approximately 10% starch, 20-25% soluble sugars, 3% fat and up to 15% other substances.

In terms of its chemical composition, juice water is an organic, predominantly nitrogen-potassium fertilizer. In terms of the content of basic nutrients (nitrogen, potassium, phosphorus), 1000 m3 of juice water is equivalent to a mixture of 15 quintals of ammonium sulfate, 5 quintals of superphosphate and 12 quintals of 40% potassium salt. In addition to soluble substances, juice water contains no more than 0.015% pulp and starch.

Wash waters are formed during the starch washing process. Their quantity is insignificant, 1-3 m3 per 1 ton of processed potatoes. The content of contaminants in the rinsing waters is insignificant, since the main part of them leaves with juice waters. The contaminants consist of soluble potato substances and relatively small amounts of small particles of pulp and starch.

Press water appears as a result of pulp pressing by washing it. The amount of press wastewater is 0.4-0.6 m3 per 1 ton of potatoes. The composition of contaminants in these wastewaters is similar to the composition of contaminants in juice waters.

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

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

The specific wastewater consumption per unit of output 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 of 1500-5000 mg/l, average mineralization of 1800-3500 mg/l, bicarbonate-sulfate composition, acidic reaction, 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 variable, with a large amplitude of fluctuations.

The total discharge of enterprises processing potatoes for starch is characterized by the following amount of pollution: suspended solids 2500-18000 mg/l, BODb - 1100-1500 mg/l. At the same time, the composition of suspended substances, mg/l, is: total amount 2824, including organic - 1454, total nitrogen - 265, phosphorus - 93, potassium - 486.

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

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

When producing starch using corn as a raw material, wastewater is generated in the amount of 24-28 m3 per 1 ton of starch. This amount does not include grain pre-treatment wastewater, i.e. from soaking and swelling, as they are processed in evaporators and subsequently used as livestock feed or as feedstock for the production of penicillin.

In addition to starch, refined starch milk contains a certain amount of very fine pulp, coagulated proteins and remnants of potato cell sap. Juice water, when standing in air, quickly turns pink and then becomes darker, and therefore the color of the starch deteriorates. Prolonged contact of starch with juice water reduces its gelatinous ability. Therefore, the old equipment for isolating starch by long-term settling (settling tanks) is now being widely replaced by precipitation centrifuges of various types.

To obtain high quality starch (purity 99.4-99.6%), it is necessary to remove almost all impurities, for which the starch is washed.

Purifiers. Some factories use specially equipped centrifuges called purifiers to separate and wash starch. The purifier (Fig. 1) - a purifier - is a centrifuge with a vertical shaft 1, a drum 2 and a casing 3. The drum has a diameter of 1.2 m, a height of 0.8 m and a rotation speed of 400-500 rpm. Starch milk flows through a stationary funnel 4 onto a rotating turbine wheel 5, which imparts to the milk a peripheral speed equal to the speed of rotation of the drum. Here, under the influence of centrifugal force, the milk is distributed along the vertical generatrix of the drum and is divided into three layers: heavy impurities first settle on the wall, then pure starch, then a layer of mud starch and, finally, wash water, forming a hollow cylinder. The separation occurs for about a minute, after which knife 6 is set in motion, which seems to cut off the layer of juice water. The water loses its speed and flows through the lower hole 7. After removing the water, the knife is slowly brought to the mud layer and carefully cuts it off. This layer is also removed through the lower opening of the zeitrifuge.

Pure starch is diluted with water supplied through a vertical pipe. At this moment, the knife is withdrawn, the knife holder and stirrer are brought to the starch layer with the other side, and the starch is suspended with stirrer 8 at a reduced drum speed. Then the mixer returns to its original position and the starch precipitates again. The wash water and mud layer are removed again and the starch is diluted with clean water. Pure starch milk is removed from the centrifuge drum by inserting a pipe 9 into the milk layer, directed against the rotation of the drum. A thin layer of sediment near the drum wall (3-4 mm) always remains, and the bulk of the sand is concentrated in it, which is removed periodically.

The purifier ensures good quality starch. The disadvantages of the machine include the frequency of the work cycle and the difficulty of maintenance.

Rice. 1 . Purifier.

Hydrocyclone. The most advanced equipment for separating and washing starch suspensions, used both in the USSR and abroad, are hydrocyclones. Starch milk enters the hydrocyclone (Fig. 2) through a pipe / tangentially under pressure, as a result of which the translational movement is converted into rotational and heavy particles are thrown by centrifugal force onto the inner surface of the cone, along which they slide in a flow (thick waste or heavy fraction) to the drain hole 2. The light fraction of the product (liquid discharge) is displaced by the condensed fraction and rises in a vortex to drain device 3, through which it is discharged from the hydrocyclone.

To increase centrifugal force, and therefore for better separation of starch and fine pulp, small hydrocyclones (microcyclones) with an internal diameter of the cylindrical part of 20 mm are used in potato starch production.

In order to increase the throughput of hydrocyclones when separating starch, batteries (packages) are usually used, consisting of a large number of parallel-installed cylindrical-conical elements (microcyclones). Such batteries (multicyclones) are cylinders divided into three parts by two transverse disks. The discs have holes between which microcyclones are inserted. A starch suspension is pumped into the middle chamber by a pump, and with the help of tangentially located nozzles it is distributed among the elements of the hydrocyclone. Condensed wastes are collected in the second chamber, and clarified liquid wastes are collected in the third. The second and third chambers of the multicyclones are equipped with outlet pipes through which the products are transported to the next technological operation.

To completely wash starch from soluble substances and almost completely remove pulp, the starch suspension is usually processed on multicyclones sequentially in three stages. With this treatment, a starch suspension with a concentration of 7% from the source product collection is fed through filters to the first stage of the main chain of hydrocyclones. The condensed product is diluted with liquid waste from stage III and pumped to stage II. After stage II, the condensed waste is diluted with clean water and pumped to stage III, from which a thick starch product with a concentration of 36-40% is collected in a raw starch collection.

Rice. 2. Hydrocyclone.

Liquid waste from stages I and II enters a collection tank and from there is sent to special devices for separating small starch grains (precipitation centrifuges, special hydrocyclones, etc.).

With a decrease in water consumption, wastewater entering treatment plants almost always has an increased amount of contaminants, since with a constant technological process, the total amount of contaminants in the wastewater remains constant. This circumstance can complicate the operation of treatment facilities, especially with the biological method of wastewater treatment. To reduce the concentration of contaminants, it is advisable to provide for their partial removal at local treatment plants, as well as the possibility of subsequent disposal.

During the construction of new and reconstruction of existing industrial enterprises Of great importance is the introduction of new technological processes and the development of recycling water supply systems instead of direct-flow ones. So, for example, with a direct-flow system, 350...400 m 3 of water is required to produce 1 ton of high-quality cellulose, and with a recirculating system - 150...200 m 3.

The most widely used systems are recycling water supply in the presence of wastewater that has only thermal pollution. In this case, these waters pass through cooling structures (cooling towers, spray ponds, ponds) and are again supplied to production. During the wet beneficiation of ores and during hydro-ash removal, water becomes contaminated and must be settled before reuse. Recently recycling water supply implemented in almost all cooling systems. Experience in operating such systems shows that reusing waste water is more economical than developing new sources of water supply. Great importance also has scientific basis norms of water consumption per unit finished products or the raw materials used.

Significant water savings and reduced losses of valuable products are achieved as a result replacing water cooling with air cooling . The use of air cooling units at oil refineries makes it possible to reduce water consumption for production purposes by 3...5 times.

At metallurgical enterprises it is possible to reduce water consumption when replacing a steam drive in oxygen and steam-air stations electric , as well as when replacing water cleaning with air cleaning in gas cleaning of blast furnace and steel-smelting shops. It is advisable to use air cooling in enterprises chemical industry in the production of caprolactam, ammonia, etc. To reduce water consumption at metallurgical plants and non-ferrous metallurgy enterprises, the use of evaporative cooling . It should also be taken into account that the amount of steam coming from evaporative cooling units is quite sufficient for the needs technological process, as well as heating, ventilation and hot water supply of the enterprise.

The use of air coolers minimizes the need for cooling water. In addition, air-cooled units are more reliable than water-cooled units.

One of the ways to dispose of industrial wastewater is to use it in agriculture for irrigation needs. Naturally, it is not advisable to use wastewater, which has predominantly mineral contaminants, for irrigation, since its fertilizing value is low, and the content of toxic substances or salts in it negatively affects the vital activity of soil microflora. In addition, these substances destroy the structure of soils. Wastewater containing organic substances can be used for irrigation independently, as well as together with domestic wastewater after preliminary mechanical treatment. The most suitable for irrigation are wastewater from some food industries (Table 4.3), chemical and light industry. It is advisable to use it for irrigation of wastewater from enterprises producing mineral fertilizers, nitric acid, etc.

Wastewater hazardous for sanitary reasons (for example, from tanneries) is prohibited from being used for irrigation. Waters with high concentrations of organic contaminants from yeast and starch factories must be diluted before use, and those from distilleries must be treated with lime.

Irrigation rates depend on many factors: wastewater concentration, type of crops grown, climatic conditions, soil type. The use of industrial wastewater in irrigation fields must be agreed with the State Sanitary Inspection authorities. The main requirement for industrial wastewater intended for irrigation is to exclude the possibility of its harmful effects on the soil, groundwater, cultivated crops, as well as on human health.

Table 4.3

Enterprises	Fertilizers, g per 1 m 3 of water
	Total nitrogen	Potassium oxide	Phosphoric anhydride
Sugar factories
Dairies
Starch factories
Slaughterhouses and meat processing plants
Yeast factories
Fruit and vegetable factories

Wastewater from starch factories, which can be used in all soil and climatic zones, is very promising for irrigation of agricultural crops; At the same time, wastewater from potato starch production has the greatest fertilizing value.

Due to the high content of nutrients in these waters, soil fertility and agricultural yields increase (the yield of corn and perennial grasses increases by 2–3 times with irrigation).

Wastewater from sugar factories has less fertilizing value. Their use is advisable (after preliminary clarification) for irrigation of chernozem soils. When wastewater is used for irrigation, a significant part of the area of ​​filtration fields, where wastewater from sugar factories was previously treated, can be returned to agricultural land use.

It is also of interest to use alcohol stillage, which is formed during the production of alcohols based on plant raw materials, as an additive to livestock feed. In this regard, it is advisable to locate livestock farms in close proximity to an industrial facility.

An effective way to reduce the pollution of industrial wastewater is to extract from it valuable substances that enter the wastewater as waste during the production process. The extraction of valuable substances is carried out either in workshops immediately after the waste water leaves the technological apparatus, or in on-site local installations. As a rule, valuable substances are extracted from wastewater not only to reduce the concentration of pollutants, but also for their disposal.

Oil and petroleum products are extracted and utilized from wastewater from oil refineries and oil production plants, and cellulose fiber from wastewater from pulp and paper mills. In sulfate pulp production, strong liquors are regenerated after pulping; Cellulose sulfite liquors are used to produce alcohol and yeast. From factory wastewater primary processing Wool mills (WSP) extract wool fat, which is used to make lanolin, a valuable product used in medical, electronics, perfume and other industries.

In mechanical wastewater treatment facilities for the production of mineral pigments, almost pure pigment is retained.

To remove hydrogen sulfide from drainage waters of contoured wells and waters from in-quarry drainage of mining and chemical plants, a physico-chemical method of purification can be used, followed by aeration in scrubber-degassers (at a hydrogen sulfide concentration of 50...100 mg/l). The released hydrogen sulfide is used to produce sulfur paste.

To neutralize sulfur-alkaline wastewater from oil refineries, it is recommended to carbonize it with carbon dioxide contained in flue gases to obtain a soda ash solution. The electrolysis method, in which the alkali is regenerated, can also be used.

Wastewater treatment from viscose fiber plants involves the use of regenerative methods to return zinc to production.

Tanneries are designing installations for the extraction and recycling of chromium and wool.

Methods for extracting valuable impurities from industrial wastewater can be different, and their use is justified by many factors.

To extract heavy metals Chemical and physical-chemical methods are used. During the production of photographic and film materials, water is formed whose silver content is 20...70 mg/l. In a local silver recovery plant, wastewater is collected in a reservoir, from which it is pumped into a container and heated with live steam to a temperature of 35...45 °C. A 10% solution of ferrous sulfate is supplied to the same container. Then the water flows by gravity into the reactor, in which, at pH = 9.2...10.2, a precipitate containing silver is formed. Together with water, the sediment enters the settling tank, from where it is pumped to the dryer. The dried sludge is sent to a plant where it is disposed of. Water freed from silver is sent from the settling tank to treatment facilities. During the year, the installation processes 25 thousand m 3 of water containing silver, and about 500 kg of silver is recycled.

In the production of potassium nitrate, the waste product is brine with a sodium chloride content of 220...250 g/l. With the introduction of a sodium chloride recycling workshop at the plant, the content of the latter in the total drain decreased from 4,800 to 1,200 mg/l. At the same time, over 3,500 tons are recycled annually sodium chloride, 40% which is produced in the form of chemical products of reactive purity.

Thus, wastewater from industrial enterprises is a complex aqueous solutions. Methods of their processing, ways of using and the possibility of recycling the valuable substances contained in them must be justified taking into account production technology, economic factors, sanitary requirements and local conditions.

Due to the diversity of its properties and the ability to change them, starch is used in different food production(confectionery, bakery, sausage, etc.), in cooking, for the production of starch products, in non-food industries (perfume, textile, etc.).

Calorie content of 100g of starch is 350 kcal. In plant cells, starch is found in the form of dense structures called starch grains. Starch grains of different plants are characterized by a certain shape, structure, and size. Based on these characteristics, the type of starch can be determined. Starch can be made using various plant materials. However, the production technology is slightly different. In this article we will describe the technology for producing starch from potatoes and corn.

Potato starch production

The potatoes are washed to remove dirt and foreign inclusions in a potato washer, then served for chopping. The more it is crushed, the more complete the release of starch from the cells will be, but it is important not to damage the starch grains themselves. First, the potatoes are crushed twice on high-speed potato graters. The principle of their operation is to abrade the tubers between the working surfaces formed by saws with fine teeth mounted on a rotating drum. On the first grinding graters, the files protrude above the surface of the drum by 1.5...1.7 mm, on the second grinding graters - no more than 1 mm. During the second grinding, an additional 3...5% of starch is extracted. The quality of chopping also depends on the condition of the potatoes (fresh potatoes shred better than frozen or limp ones).

After crushing the tubers, ensuring the opening of most of the cells, a mixture is obtained consisting of starch, almost completely destroyed cell membranes, a certain amount of undestroyed cells and potato juice. This mixture is called potato porridge. Starch remaining in unbroken cells is lost as a by-product of production - potato pulp. This starch is usually called bound, and that isolated from potato tubers is called free. The degree of potato grinding is assessed reduction ratio, which characterizes the completeness of cell destruction and the amount of starch extraction. It is determined by the ratio of free starch in the porridge to the total starch content in potatoes. At normal operation it should not be less than 90%. To improve the quality of starch, its whiteness and prevent the development of microorganisms, sulfur dioxide or sulfurous acid is added to potato porridge.

The nitrogenous substances in juice include tyrosine, which is oxidized under the action of the enzyme tyrosinase to form colored compounds that can be sorbed by starch grains and reduce the whiteness of the finished product. Therefore, the juice is separated from the porridge immediately after grinding. Hydrocyclones are used to separate sand from the starch suspension and separate the pulp from potato juice. The principle of their operation is based on the centrifugal force generated during rotation. As a result of processing, a starch suspension with a concentration of 37...40% is obtained. They call her raw potato starch.

Continuous pneumatic dryers are most often used to dry starch. different designs. Their work is based on the principle of drying loosened starch in a moving stream of hot air. The yield of finished starch depends on its content in the processed potatoes and on the loss of starch with by-products and wastewater. In this regard, the starch content in potatoes supplied for processing is standardized by the standard and should be at least 13...15%, depending on the cultivation zone.

When producing starch, it is produced in two forms: dry and raw potato starch. The amount of raw potato starch is determined in accordance with OST 10-103-88. There are raw starch grade A and grade B with a moisture content of 38 and 50%, respectively. Depending on the quality (color, presence of inclusions, foreign odor), raw starch is divided into three grades - first, second and third. Raw starch is a perishable product and long-term storage cannot be used; 0.05% concentration of sulfur dioxide can be used for preservation.

Dry starch is packaged in bags and small packages. Potato starch is packaged in double fabric or paper bags, as well as bags with polyethylene liners weighing no more than 50 kg. In terms of quality, starch, in accordance with the requirements of GOST 7699-78 “Potato starch” is divided into the following grades: “Extra”, highest, first and second. Starch moisture content should be 17...20%, ash content 0.3...1.0%, acidity 6...20° depending on the variety. The content of sulfur dioxide is not more than 0.005%. Important indicator, characterizing the purity and whiteness of starch, is the number of specks per 1 square dm when viewed with the naked eye. For “Extra” - 80, for the highest - 280, for the first - 700, for the second it is not standardized. Second grade starch is intended only for technical purposes and industrial processing. Guarantee period storage of starch for 2 years from the date of production at a relative air humidity of no more than 75%.

Corn starch production

In general terms, the corn processing process can be described as follows: the shelled corn is softened in hot water containing sulfur. With coarse grinding, the germ is separated, and with fine grinding, fiber and starch are separated. The mill effluent is cleared of gluten and washed repeatedly in hydrocyclones to remove the last traces of protein and obtain high-quality starch.

CLEANING.The raw material for wet grinding is threshed corn. The grain is inspected and cobs, straw, dust and foreign materials are removed. Typically cleaning is done twice before grinding. After the second cleaning, the corn is divided into portions by weight and placed in bins. From the bunkers it is hydraulically fed into the locking vats.

SOAK.Proper soaking is a necessary condition high output and good quality starch. Soaking is carried out in a continuous counter-current process. The shelled corn is loaded into a battery of large locking containers (tanks), where it swells in hot water for about fifty hours. In fact, soaking is a controlled fermentation, and adding 1000-2000 ppm of sulfur dioxide to the steep water helps control this fermentation. Soaking in the presence of sulfur dioxide directs fermentation by accelerating the growth of beneficial microorganisms, preferably lactobacilli, while inhibiting harmful bacteria, mold, fungi and yeast. The soluble substances are extracted and the grains are softened. The grains more than double in volume and their moisture content increases from approximately 15% to 45%.

Scheme of grain soaking at a plant with a capacity of 150 tons of corn per day

EVAPORATION OF SOAP WATER. The steep water is drained from the grain and condensed in a multi-stage evaporation plant. Most organic acids formed during fermentation are volatile and evaporate along with the water. Consequently, condensate from the first stage of the evaporation plant must be neutralized after heat recovery by heating the water supplied for soaking. The depleted steep water, containing 6-7% dry matter, is continuously withdrawn for subsequent concentration. The steep water condenses into a self-sterile product - a nutrient for microbiological industry, or concentrated to approximately 48% solids and mixed and dried with the fiber.

SO2 PRODUCTION.Sulfurous acid is used to soak and soften the corn grain and control microbiological activity during the process. Sulfur dioxide is produced by burning sulfur and absorbing the resulting gas with water. Absorption occurs in absorption columns where the gas is sprayed with water. Sulfurous acid is collected in intermediate containers. Sulfur dioxide can also be stored in pressurized steel cylinders.

SEPARATION OF THE EMBER . The softened grains are destroyed in abrasive mills to remove the shell and destroy the bonds between the germ and the endosperm. Water is added to support the wet grinding process. Good soaking ensures free separation of the intact germ from the grains during the soft grinding process without releasing oil. Oil constitutes half the weight of the embryo at this stage, and the embryo is easily separated by centrifugal force. Light embryos are separated from the main suspension using hydrocyclones designed to separate the primary embryo. For complete separation, the product stream with the remaining germ is subjected to re-grinding, followed by separation on hydrocyclones, which effectively removes the residual - secondary - germ. The germs are washed repeatedly in countercurrent on a three-stage sieve to remove starch. Clean water is added at the last stage.

Separating the germ at a plant with a capacity of 150 tons of corn per day

Wastewater from starch and syrup industry enterprises. Wastewater treatment from potato starch factories

Hydroclones GP-100 and GP-300 have proven themselves to be good for separating sand from water. With a corresponding increase in their size, they can purify conveyor and washing waters from sand, thus eliminating expensive sand traps and settling tanks.

Treatment of wastewater from potato starch factories using aeration tanks is rare. Job Research different types aeration tanks indicated the feasibility of using aerotanks< 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 studied in a pilot plant under contact conditions. Active pl has been adapted to starch and to some other substrates. The activated sludge and starch solution were poured into an aerated vessel and aerated for 7 hours. The initial concentrations of starch and sludge activity in the waste liquid varied widely.

The installation systematically determined changes in the concentration of COD, starch, activated sludge, as well as the rate of decrease in 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 filtrate COD was due to the action of starch-degrading exoenzymes released by activated sludge. As a result of the complex of studies, the following was established:

a) the rate of decrease in 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 1 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 explained by the fact that only a small part of the exoenzymes is released from the silt water, and the main part of them is sorbed on bacterial cells;

d) in all experiments it was noted that after mixing the substrate with activated sludge, immediate adsorption of part of the substrate on activated sludge occurred, and the amount of sorbed starch was directly dependent on temperature, the amount of activated sludge and its acclimatization.

Most effective way Treatment of wastewater from potato-starch enterprises is their disposal in filtration fields. However, the increased concentration of pollutants in potato-starch wastewater used for irrigation in filtration fields requires a reduction in the load on these types of structures compared to domestic wastewater by 1.5-2 times.

When using wastewater from starch and syrup industry enterprises in irrigation fields, a load of 12,000–15,000 m3 of wastewater per 1 hectare is recommended for the period of operation of the enterprises (about 120 days). Thus, the daily load per 1 hectare will be 100–125 m3/day. In this case, wastewater used for irrigation of agricultural crops must be subjected to preliminary treatment. When using starch plant wastewater for irrigation during the growing season, it requires averaging, neutralization and dilution by 1.5-2 times. 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 the supply of river water for dilution. Conveyor and washing water can be used for dilution. If wastewater is used during the non-growing season, dilution is not necessary.

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

Table 29. Comparative characteristics of the fertilizing qualities of juice waters and manure

In comparison with mineral fertilizers, 100 m3 of juice water is equivalent in nutrient content to approximately 17 quintals of ammonium sulfate, 5 quintals of superphosphate and 10 quintals of calcium chloride. Characteristic feature This wastewater decays quickly, so its accumulation and storage is impossible.

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

The use of juice waters for irrigation has shown high efficiency when 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.

Optimal irrigation rates in conditions of light sandy loam soils when irrigating starch factories with juice water, m3/ha:

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

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

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

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