Powder wastewater is corn, potato, wheat, rice and other agricultural products as raw materials for the production of starch or starch deep-processed products (amylose, glucose, starch derivatives, etc.) of the wastewater generated by the industry, generally belongs to the high-concentration organic wastewater, is caused by one of the main sources of pollution, in this article, we will analyze the wastewater treatment process of starch wastewater in detail in the hope that it can help you.
Main treatment process selection
Recently, the Ministry of Environmental Protection has issued a new technical specification for starch wastewater treatment engineering (HJ 2043-2014). This standard is based on China's current pollutant discharge standards and pollution control technology, and stipulates the technical requirements for the design, construction, acceptance and operation and maintenance of production wastewater treatment projects for the production of starch and subsequent products from raw materials such as corn, wheat and potatoes.
The starch wastewater treatment engineering technical specifications (HJ 2043-2014) standard is issued for the first time. It specifies the sources of starch production wastewater and the main treatment process selection:
Sources of starch production wastewater
When producing starch from corn, the wastewater mainly comes from the drainage water after the recovery of protein in the sections of corn soaking, germ separation and washing, fiber washing, flotation and concentration, and protein filtering, as well as evaporation condensation water generated during the recovery of water resources from corn soaking.
When raw tea starch is produced from potatoes, the wastewater mainly comes from the drainage water after protein recovery in the stages of juice removal, separation and dehydration, as well as the wastewater from raw material transportation and cleaning.
When producing starch from wheat, the wastewater consists of two parts: the supernatant in the settling tank and the yellow slurry water produced after centrifugation.
When starch is used as raw material for the production of starch sugar, the wastewater mainly comes from the rinsing water of ion-exchange columns, the rinsing water and washing water of various equipments, and the cooling water of liquefied saccharification process.
The main pollutants in starch wastewater are suspended solids (SS), chemical oxygen demand (COD), ammonia nitrogen (NH3-N), total nitrogen (TN) and total phosphorus (TP).
The selection of starch wastewater treatment process route should be based on the current national and local emission standards, the source and nature of pollutants, drainage to determine the degree of starch wastewater treatment, the selection of the appropriate treatment process.
The overall treatment of starch wastewater should be "pretreatment + anaerobic biological treatment + aerobic biological treatment + depth treatment" of the pollution management process, the process flow diagram is as follows: starch enterprises according to the starch production of raw materials and product types, the nature of wastewater to choose the appropriate wastewater process route and unit technology.
Pre-treatment process, starch production wastewater should be removed by grating, sedimentation, air flotation and other processes to remove suspended solids into the regulator, water regulation; potato starch production wastewater should be set up in front of the sedimentation tank defoaming facilities; potato starch wastewater in the raw material conveyor clear wastewater should be removed through the process of sand sedimentation and other sand particles in the sewage after entering the regulator.
Anaerobic biological treatment can choose rising flow anaerobic sludge bed reactor (UASB), anaerobic granular sludge expansion bed reactor (EGSB), internal circulation anaerobic reactor (IC) and other processes; wastewater in the anaerobic reactor should be adjusted before entering the PH adjustment and temperature adjustment; amylose and modified starch production wastewater need to be injected with nutrient salts to regulate carbon and nitrogen ratios in the anaerobic biological reaction.
Aerobic biological treatment can choose sequential batch activated sludge (SBR), anoxic - aerobic (A/O) + two sedimentation tanks, oxidation ditch + two sedimentation tanks and other processes.
Depth treatment can choose coagulation and sedimentation, sand filtration, membrane bioreactor (MBR) and other processes; according to the water demand can be treated by nanofiltration, reverse osmosis reuse. According to the different purposes of reuse, reuse can choose ultrafiltration, ultrafiltration + reverse osmosis (RO), ultrafiltration + RO + mixed ion exchange bed process. Among them, MBR can be used instead of aerobic biological treatment (nitrogen and phosphorus removal) + depth treatment, or MBR as a depth treatment process.
Starch wastewater treatment program
I. Project Overview
(I) Project Background
Something and something limited company in the sweet potato starch processing process produces a large number of high concentration acidic organic wastewater, wastewater mainly from the starch processing process of washing, filtering, concentration and other process sections. Wastewater contains a large number of dissolved organic pollutants, such as starch, proteins, sugars, carbohydrates, fats, amino acids, etc., followed by inorganic compounds containing N, P, in addition to a certain amount of volatile acids, ash, etc., belonging to the biochemistry of the high concentration of organic wastewater, but due to the ammonia and nitrogen and salt content, it is difficult to deal with. These organic wastewater discharged into the water body to consume a large amount of dissolved oxygen, such as direct discharge without treatment, will cause pollution to the environment.
Starch production is about 80% of the sweet potato as raw materials, the rest of corn, wheat, barley, oats and other starch-rich plant roots as raw materials. Raw materials contain starch in addition to a variety of other components - protein, cellulose, organic salts and so on. In starch production by raw material treatment, soaking, crushing, sieving, separating starch, washing, drying and other major processes. However, the specific operation of the raw materials due to the existence of a number of differences, the main source of wastewater is also due to the different raw materials for starch production.
(II) Sewage Discharge
Water volume and discharge pattern
According to the owner's requirements, with reference to the design information accumulated over the years on the domestic units and the successful experience in food sewage treatment, and taking into account the rainfall backflow and the peak of the production, the community sewage treatment is designed according to the volume of 2m3/H. The community sewage treatment is designed according to the volume of 2m3/H, and the water is discharged into the water.
The sewage treatment station equipment operation is fully automatic and manned operation, working 24 hours a day, annual production by 365 days.
Located in a rural community in Pingding County, Shanxi Province, this food enterprise treats production wastewater containing high COD, SS and BOD5. The wastewater is discharged intermittently, with a discharge of about 20 m3/d, and the average daily water quality fluctuates greatly. And the production wastewater contains a variety of high indicators of organic pollutants, but the sewage B / C is 0.5, biochemical performance is better, so the use of hydrolysis acidification tank + biological contact oxidation + MBR membrane process for the main process, disinfection treatment for auxiliary treatment. This combination of treatment processes for such production of wastewater treatment effect is stable, simple operation, less residual sludge production, and has a strong shock load capacity. The final effluent quality of treated wastewater is required to implement the "Comprehensive Wastewater Emission Standards" (GB8978-1996) in the first level of standards, and the original wastewater quality and discharge standard requirements are shown in Table 1.
Table 1 wastewater quality and discharge standards
(C) wastewater water quality conditions
Based on the general food production wastewater quality monitoring report and the actual situation, the wastewater water quality conditions are as follows:
Two, the basis for the preparation of this program, the principles and scope of the program
(A) the basis for the preparation of
1, "Chinese People's Republic of China*** and the country of Water Pollution Prevention and Control Law";
2, water quality, water quantity and related information provided by the enterprise;
3, the national "Comprehensive Wastewater Emission Standards" GB8978-1996 in the first level of discharge standards;
4, "Outdoor Drainage Design Code" GBJ14-47;
5, the country's current relevant engineering design specifications.
(B) the principle of preparation
1, seriously implement the national guidelines and policies on environmental protection, in line with the relevant national regulations, norms, standards;
2, strict implementation of the national laws and regulations relating to environmental protection, to ensure that the quality of water to meet the national and local standards for the discharge of pollutants.
3, actively and steadily adopt advanced and reliable treatment technology, in order to save construction funds and rational use of funds to create conditions.
4, the implementation of the economy and reliability of the design principles, in order to minimize the cost of the project and operating costs at the same time, a reasonable balance between the operating conditions and management and maintenance conditions.
5, the need for a combination of the principle of possible, give full consideration to the actual situation of the local and considerable conditions, according to local conditions, actively and steadily using advanced technology, so that the project indicators can achieve the desired purpose.
6, the quality of water after treatment by the wastewater treatment works, should be able to meet the relevant national and local environmental protection department standards.
7, the scale of wastewater treatment should leave some room to meet the needs of production development, compact layout, as little as possible to occupy land, the implementation of scientific management.
8, the selected process has a good treatment effect, advanced and mature technology is stable and reliable, adaptable, economically rational, under the premise of ensuring that discharge standards, and strive to be simple and practical in order to facilitate the management of the operation;
9, to minimize the one-time investment, and strive to reduce the operating costs, and has a sustainable development;
10, to create a good environment for production and living, and strive to create a modern garden-style sewage treatment project. Strive to create a modern garden-style sewage treatment works.
(3) Scope of preparation
1, this program only involves the design and construction estimates within the wastewater treatment station;
2, fire protection design, winter warming and pipeline network design outside the wastewater treatment station, power supply system design and budget estimates by the enterprise's own arrangements.
Three, the discharge of wastewater characteristics of the overview
The food enterprise's production of wastewater discharges is a medium low concentration of organic wastewater, mainly containing organic pollutants, does not contain toxic substances, wastewater BOD5/CODcr is about 0.6, good biochemical properties, easy to biochemical treatment. Production wastewater generated in the starch production process contains starch, sugars, proteins, organic acids and other dissolved organic substances, small particles of starch, fibers and other insoluble fine particles of organic matter and inorganic substances such as mud and sand. In order to reduce the processing load of the subsequent treatment structures, to protect the subsequent treatment facilities, should be transported, cleaned and discharged wastewater pre-treatment treatment facilities at the back end of the installation of air-floatation equipment in order to retain the original sewage in the larger suspended or floating debris, removal of wastewater precipitates.
The enterprise wastewater is a high concentration of biochemical organic wastewater, so biochemical treatment methods can be used. Due to the high BOD of the raw water, the required treatment effect is also high, anaerobic and aerobic treatment route is proposed. The difficult to degrade COD in the wastewater is converted into easier to degrade COD after anaerobic treatment, and the high molecular organic matter is converted into low molecular organic matter, and the aerobic biological treatment method is mature, stable, and the effluent water quality is better. Therefore, the use of anaerobic and aerobic treatment route is more reasonable.
Four, wastewater treatment process selection
(a) process selection
According to the actual site of the enterprise, it is recommended to use the integration of steel structure, with a small footprint, flexible, durable, basically no noise and low operating costs, etc., the relative investment is not large, the treatment process is still using biochemical treatment.
Integrated starch wastewater treatment equipment, the use of anaerobic process, aerobic process-based treatment process. Preliminary pretreatment process, should be set up grating, regulating pool or sedimentation tank, etc., in order to minimize the suspended solids into the biological treatment structure, to ensure the normal operation of subsequent processes. Comprehensive analysis and consideration, determined the use of air flotation + hydrolysis acidification tank + biological contact oxidation + MBR membrane process treatment + disinfection treatment process to treat the wastewater.
The wastewater is elevated into the coagulation and flocculation device by the regulating pool grease trap regulating pool, and PAC and PAM are added sequentially to fully carry out the coagulation and flocculation reaction. After coagulation and flocculation reaction, the wastewater enters into high efficiency combined air flotation to remove most of the oil and SS, and the effluent basically meets the standard, and then passes through the integrated wastewater treatment equipment to remove COD, BOD, ammonia nitrogen and PH value in the water, and then finally disinfects it with chlorine dioxide in the last process and the effluent meets the standard and is discharged.
Air flotation device to remove parameters:
Wastewater treated by the air flotation equipment flows into the regulating pool for initial homogenization, homogenization, mainly because of the pre-aeration and mixing of wastewater in the regulating pool can be avoided as far as possible, a large number of SS in the regulating pool build-up and fermentation, while also being able to oxidize the wastewater blowing off low molecular organic pollutants. Subsequently, it is lifted to the hydrolysis acidification tank by submersible sewage pump. In the hydrolysis acidification pool to get domesticated, cultivated a large number of anaerobic microorganisms, the wastewater contained in most of the high molecular organic pollutants broken degradation of small molecule organic pollutants, and thus improve the biochemical properties of wastewater, and effectively alleviate the subsequent aerobic biochemical treatment process of the treatment pressure. Wastewater by hydrolysis acidification treatment into the contact oxidation pool, contact oxidation pool of aerobic microbial populations and nitrifying bacteria in the pool Roots blower aeration and oxygenation, a large number of organic pollutants are aerobic microbial populations oxidative degradation of CO2 and H2O, wastewater ammonia and nitrogen oxidation into nitrate and nitrite can be removed. After the contact oxidation pool treatment of the effluent for the final coagulation and precipitation reaction, the role is to make the wastewater is not easy to precipitate the fine particles of floc cohesion to form large particles of flocs, the mixture then enters the second sedimentation tank for solid-liquid separation, to ensure that the final effluent water quality and stability of the discharge standard requirements. After solid-liquid separation, the supernatant overflow into the effluent flow weir can be discharged, and the remaining sludge is discharged into the sludge thickening tank for sludge thickening treatment.
Membrane - Bioreactor (MBR)
Main function: the use of microorganisms to remove a large number of soluble organic matter in the wastewater, a large number of COD and ammonia nitrogen to reduce the wastewater, due to the high degree of separation of the membrane characteristics of the discharge water basically does not contain suspended solids. After MBR treatment to make the wastewater completely meet the discharge standards, the quality of its effluent due to the national requirements of the sewage discharge standards.
Brief description of the sludge treatment process
Sedimentation sludge in the sludge collection hopper at the bottom of the sedimentation tank is pumped into the sludge thickening tank by the pneumatic lifting device, and then sludge gravity thickening is disposed of in the sludge thickening tank, and the sludge thickened after coagulation and thickening in the sludge hopper is pressurized by the sludge pump and pumped to the chamber-type filter press, and then the subsequent filter press and dewatering is carried out. The supernatant of the sludge thickening tank and the filtrate of the chamber filter press are returned to the conditioning tank for treatment. The dewatered sludge is collected and then transported to the sanitary landfill for treatment by special sludge transportation trucks.
(II) Biological treatment technology
In the biological treatment technology, we chose an aerobic biological treatment technology that has developed most rapidly in recent years - biological contact oxidation + MBR membrane process.
This method belongs to one kind of biofilm method, and the bio-carrier of this method is mainly the high-quality bio-filler installed in the tank. Compared with other biological treatment methods, its main features are:
1. Due to the large specific surface area of the filler, the oxygenation conditions in the pool are good, and the biosolids per unit volume in the biological contact oxidation pool (10-20g/L) are much higher than the biomass of the aeration pool of the activated sludge method (1.5-3.0g/L). Therefore, the biological contact oxidation tank has a high volumetric load (3.0~6.0kgBOD5/m3˙d), which is 6~7 times higher than that of activated sludge method.
2. Because a considerable part of microorganisms solid growth on the surface of the filler, there is no headache of sludge expansion problem, convenient operation and management.
3. Due to the biological contact oxidation tank biosolids, water quality is completely mixed, so the biological contact oxidation tank of water quality and water quality of the sudden change has a strong adaptability.
4. Due to the biological contact oxidation tank biosolids, organic volume load is higher, its F/M (organic substrate F and microbial M ratio) can be maintained at a certain level, so the sludge production is lower than the activated sludge method.
5. Large treatment capacity, small footprint, high volumetric load, small pool volume, equivalent to one-fourth to one-fifth of the activated sludge method and oxidation ditch.
6. High oxygen utilization rate (more than 15%) operating power saving.
In the biological contact oxidation process, there are two types of oxygen supply, one is the blast aeration, a jet aeration. Compared with these two ways, blast aeration has a high oxygen utilization rate, energy saving and other characteristics, so the program decided to use the "blast aeration biological contact oxidation" process for biochemical treatment of wastewater in the enterprise.
This technology is characterized by low investment, high efficiency, low operating costs, easy operation and management, and strong shock load resistance.
7. MBR membrane cleaning method is generally determined according to the nature of the membrane and the nature of the treatment fluid. Inorganic membrane separation object is activated sludge mixture. Microorganisms in the bioreactor degradation of organic matter in the restaurant sewage is a dynamic, continuous process. The nutrients in the catering wastewater are mainly oil, starch, protein, etc., which are converted into energy and a part of themselves through the decomposition and absorption of microorganisms. The normal metabolism of microorganisms produces sticky polysaccharides, sticky peptide molecules and protein molecules, etc. . After the death of bacteria, part of these substances can be utilized by other microorganisms, and part of them may exist in the activated sludge mixture. Similarly, a small amount of inorganic salts from restaurant wastewater can be partially ingested by microorganisms such as bacteria, and the remaining portion is also present in the activated sludge mixture. These components remaining in the sludge mix eventually reach the membrane surface and form a gel layer that clogs the membrane.
V. Technical solutions for the design of sewage treatment stations
(a) Project location
Vacant area to the right of the cesspool drain.
(II) design parameters
1. Design capacity: Q = 20m3 / d, 24 hours a day operation, design: 1m3 / h.
2. Design of water quality of influent (see Table 1)
Table 1 - design of water quality of influent - into the integrated sewage pond
3. Design of water quality (using GB8978- 1996 "Comprehensive Sewage Discharge Standards" in the primary standard). (See Table 2)
Table 2-Designed effluent water quality
(C) Process Flow Description
Wastewater through the air-floatation equipment to remove floating debris and floating oil, flow into the regulating pool for the adjustment of water quality and quantity of water pre-treatment, and then into the primary and secondary contact oxidation tank for biochemical treatment, and at the same time, the primary and secondary contact oxidation tank of water aeration with a blower. After two contact oxidation tank for biochemical treatment of water containing residual biofilm, must be carried out by the sedimentation, MBR membrane process, the supernatant discharged by the sedimentation, this time the effluent water quality reaches GB8978-1996 level one standard. The sludge generated after the sedimentation tank is returned to the septic tank for anaerobic treatment. After the septic tank for anaerobic treatment of supernatant flow into the regulating tank for treatment, and so on.
(D) The characteristic technology adopted in this process
1. The sludge generated by this process is cleverly designed to be anaerobically digested instead of being discharged for treatment. This greatly improves the environment of the sewage treatment station. As the entire sewage treatment implementation is buried underground, basically do not occupy land.
2. Biological contact oxidation tank: the device for the entire wastewater treatment process in the key technology, where the application of the most advanced aeration device will not be clogged - variable hole aeration hose and a new combination of porous ring biological filler. Ensure the efficient operation of the biochemical system.
(E) Wastewater treatment effect prediction
Table 2 Project operation monitoring results
This shows that , the treated water quality reaches the GB8978-1996 level 1 standard. The treated water can be reused for flushing toilets, watering plants, irrigating farmland, etc. in office buildings and residential buildings after filtration.
(F) Overview of the main structures and equipment
Integrated wastewater treatment equipment:
1, grille: in the integrated sewage into the regulating pool before setting a grille to remove the production of sewage in the soft tangles, larger solid particles of debris and floating objects, thereby protecting the subsequent work of the pump life and reduce the system to deal with the workload.
2, regulating pool: comprehensive sewage grating treatment into the regulating pool for water, water quality adjustment homogenization, to ensure that the subsequent biochemical treatment system water, water quality balance, stability, and set up a pre-aeration system for the oxygenation and mixing, in order to prevent the sewage in the suspended particles precipitation and odor, but also on the sewage in the organic matter to play a certain degree of effectiveness of degradation, and to improve the whole system's impact resistance and treatment effect.
3
3, lifting pumps; regulating pool set up submersible pumps, by the average amount of homogeneous sewage lifting to the back stage of treatment.
4, A-class biological pool: further mixing of sewage, make full use of the pool of high-efficiency bio-elastic filler as a bacterial carrier, relying on partially oxygenated microorganisms in the sewage insoluble organic matter into soluble organic matter, large organic matter hydrolyzed into small molecules of organic matter, in order to facilitate further oxidation and decomposition of the back channel O-class biological treatment pool, while through the return flow of nitrate nitrogen in the nitrifying bacteria can be partially nitrification and denitrification. Part of the nitrification and denitrification to remove ammonia nitrogen.
5, O-level biological pool: the pool for the core part of the sewage treatment, divided into two sections, the first section of the higher organic load, through the attachment of a large number of different species of microbial communities on the filler *** with the participation of biochemical degradation and adsorption, to remove a variety of organic substances in the wastewater, so that the sewage content of organic matter has been greatly reduced. After the section in the case of low organic load, through the role of nitrifying bacteria, in the conditions of sufficient oxygen degradation of ammonia nitrogen in the sewage, but also the COD value in the sewage is reduced to a lower level, so that the sewage can be purified.
6, the second sedimentation tank; solid-liquid separation to remove biofilm and suspended sludge stripped off in the biochemical tank, so that the sewage is really purified
7, disinfection tank: the second sedimentation tank effluent into the filtration and disinfection tank for disinfection, so that the effluent quality of water in line with the requirements of health indicators, qualified for discharge.
8, blower: for the A/O level biochemical tank, regulating pool in the oxygenation and aeration, mixing, and sludge lifting, sludge digestion.
9, sludge lifting pump: submerged pumps are set up in the regulating tank to lift the homogenized sewage to the backstage treatment.
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