Glass fiber production has a certain amount of wastewater discharge, and due to the differences in product types and varieties of various enterprises, the water quality of wastewater discharge is quite different, such as kiln cooling, wire drawing washing, ground washing, production miscellaneous water, domestic water, etc. With the continuous improvement of production level and environmental protection requirements, large fiberglass enterprises in various places have basically set up certain sewage facilities. However, due to different backgrounds such as preliminary design and selection process, water treatment facilities are also different.
The electronic yarn pool kiln sewage treatment facility introduced in this paper, the operation of the traditional water treatment process is analyzed. Summarizing the existing conditions and layout, production enterprises need to combine the environmental protection discharge requirements of various places, make priority preparations for standard upgrading or rectification, and achieve stable discharge of sewage and comprehensive utilization of water resources.
1.1 Current Situation Analysis
With the stable development of the glass fiber industry, the production scale increases, and the production of sewage increases accordingly. The sewage treatment facilities built by most enterprises in the past can no longer meet the requirements of environmental protection treatment. According to the daily sewage discharge of electronic yarn and glass fiber production enterprises, the sewage generated in the production process mainly comes from the preparation of sizing agents and the cleaning water in the drawing and forming area, the circulating water in the production system, and domestic sewage.
Therefore, enterprises should comprehensively consider their environmental protection and production needs, adapt to my country’s continuously improving sewage discharge standards, stably treat and discharge domestic and production sewage, and maximize the protection of the surrounding water ecological environment.
1.2 Comprehensive discharge water quality and discharge point
The water quality of the sewage source in a glass fiber enterprise is shown in Table 1.
Enterprise sewage mainly comes from domestic sewage and production wastewater such as wetting agent preparation and wire drawing area cleaning water. The main pollutants of mixed sewage are organic matter and glass fiber (SS), and the biodegradability of raw water is average.
1.3 Emission Standards
According to the requirements of environmental protection, the treated sewage of glass fiber enterprises should generally meet the comprehensive sewage discharge standards. The specific indicators are shown in Table 2.
The sewage in the sewage treatment station is mainly composed of domestic sewage and production wastewater.
The main pollutants in domestic sewage can be divided into:
(1) Insoluble substances account for about 40% of the total pollutants, and they are either deposited on the bottom of the water (such as food residues, etc.) or suspended in the water (such as oil slicks, etc.).
(2) Dissolved substances account for about 50% of the total pollutants. Most of these substances are non-toxic and contain inorganic salts such as chloride, sulfate, phosphoric acid, and bicarbonate such as sodium, potassium, calcium, and magnesium, as well as some organic substances.
(3) In addition, it also contains some colloidal substances, various trace metals, detergents, microorganisms, etc.
It can be seen from the composition of the main pollutants in the domestic sewage that the domestic sewage has a certain organic load and good biodegradability. The C/N meets the needs of denitrification and is suitable for biochemical degradation treatment.
The production wastewater mainly comes from the preparation of the sizing agent and the cleaning water in the drawing and forming area. The main pollutants are high organic matter and a large amount of glass fiber (SS); Mainly saltwater.
1.4 Brief description of the process
(1) The sewage in the plant area flows into the grid well along the sewage pipeline. The grid well has a built-in pollution-retaining grid to intercept large suspended solids and floating substances in the sewage.
(2) 2. The effluent from the grid well flows into the adjustment tank by itself. Balance and adjust the quality and quantity of wastewater in the regulating tank.
(3) The effluent from the adjustment tank is pumped into the coagulation sedimentation tank, and the coagulation process is an extremely important treatment process in treatment process.
(4) Air flotation device, through the treatment of the air flotation device, a large amount of scum and colloid can be removed.
(5) The sewage after air flotation treatment enters the hydrolysis tank. The hydrolysis tank converts the refractory macromolecular organic matter into small molecular organic matter through the synergistic action of facultative bacteria, and removes a large amount of CODcr in the sewage.
(6) The effluent from the hydrolysis and acidification tank flows into the biological contact oxidation tank for treatment. The biological contact oxidation tank is equipped with special combined packing and efficient aeration device, which can greatly degrade the organic matter in the sewage, and at the same time use the nitrifying bacteria to nitrify the ammonia nitrogen in the sewage. The contact oxidation tank has the advantages of high volume load, short treatment time, high biological activity, high microbial concentration, strong shock load resistance, stable effluent quality, and low sludge yield.
(7) The effluent from the biological contact oxidation tank flows into the secondary sedimentation tank, and the mud and water are separated by gravity sedimentation. The clear liquid is discharged up to the standard, part of the bottom sludge is returned to the biological contact oxidation tank, and part of it is discharged to the sludge storage tank.
(8) Disinfection refers to the process of killing pathogenic microorganisms in water through disinfectants or other disinfection methods.
(9) The amount of sludge produced by each unit of this treatment process is small. After the sludge is dehydrated by the centrifugal dehydrator, the filtrate is returned to the adjustment tank.
1.5 Process Analysis
The source of sewage is the production and domestic sewage. Generally, the amount of water varies greatly. A regulating tank is set up to homogenize the water quality and quantity.
The domestic sewage comes from the drainage of the domestic sewage septic tank in the factory area. The coder and ammonia nitrogen in this sewage is relatively high, which can usually be removed by hydrolysis acidification + contact oxidation method.
At present, most glass fiber enterprises adopt the process of “regulating tank + coagulation sedimentation + air flotation + hydrolysis acidification + contact oxidation + secondary sedimentation + disinfection” according to past experience and habits. The process flow and its unit combination can basically achieve efficient removal of organic matter in water.
In the coagulation and sedimentation treatment unit, by adding chemicals into the water, the glass fiber short fibers and organic particles that are difficult to precipitate in the water can polymerize with each other to form a colloid, and then combine with the impurities in the water to form a larger floc. The floc has a strong adsorption force, which can not only absorb suspended solids but also absorb some bacteria and dissolved substances.
Air flotation is used as a pretreatment before biological treatment. The influent water contains a certain amount of flocs, etc. After air flotation treatment, SS and organic matter can be reduced. The wastewater flows into the dissolved air tank. In the state of pressurized air, the air is supersaturated and dissolved and then mixed with the raw water added with flocculant at the inlet of the air flotation tank. It quickly attaches to the suspension and lifts it to the surface of the flotation tank. This forms a sludge floating layer that is easy to remove, and the heavier solids settle at the bottom of the tank and are also removed.
Hydrolysis and acidification utilize the reaction of hydrolysis and acid-producing bacteria to hydrolyze insoluble organic matter into soluble organic matter and decompose macromolecular substances into small molecular substances, making sewage more suitable for subsequent aerobic treatment. Low power consumption completes the purification process.
The contact oxidation method is an important core unit in the water treatment process and has a high volume load. The initiation of the biological contact oxidation pool generally includes asynchronous culture acclimation and synchronous culture acclimation. During the domestication period in the contact oxidation tank, the species of microorganisms gradually increased, and the number increased logarithmically. After entering the stable period, the number of bacteria was maintained at 100/mL; the thickness of the biofilm was finally between 1.0 and 2.0 mm; Protozoa appeared in the early stage of film hanging, and metazoans appeared after film hanging mature, thus forming a complex and stable ecosystem.
According to different operating conditions, filter units can be set up as needed, which are mainly used to remove suspended solids in the effluent of the secondary sedimentation tank, improve the effluent quality of wastewater treatment, and ensure that the effluent is stable and up to standard. The final sterilized drainage can meet the environmental protection discharge requirements.
Results and discussion
It can be seen from Table 3 that after the long-term stable operation, the main indicators are in the range of 200-260mg/L, which can meet the third-level emission standards and local standards in some areas, but it is not consistent with the continuous improvement of There will be many gaps in the environmental requirements. From the analysis of the design and operation of each process unit in the treatment process, if further investment in professional management and facility maintenance can be maintained, there is still room for the reduction of water effluent indicators. However, from the perspective of achieving long-term and stable emission standards, for regions and production enterprises with higher emission standards, this treatment process has been difficult to meet the current environmental protection requirements for continuous monitoring of emissions, and further standards need to be raised to meet higher emission standards. environmental requirements.
At present, at the beginning of the construction of environmental protection facilities, many production enterprises have relatively limited investment in manpower and material resources due to the complexity of glass fiber projects. As a result, in the early stage of operation after completion, they can still barely meet the requirements. After running, there are different degrees of running problems. Therefore, although the water quality indicators of wastewater treatment and discharge of this process route can still meet the requirements for up-to-standard discharge in some areas, it is difficult to adapt to the increasingly strict and high standards in my country. Therefore, fully combining the situation of each enterprise and the existing conditions of sewage facilities, by adopting a scientific and reasonable standard upgrading process plan, the applicability transformation is carried out to improve the treatment standard. At the same time, the principle of “three-part construction and seven-part management” is also applicable to wastewater treatment. In addition to ensuring a certain amount of capital investment in the construction of sewage treatment plants, the manpower and cost input for operation and maintenance management are also important guarantees for normal operation. Only through these measures can the development of the glass fiber industry in wastewater treatment and water resources utilization be promoted.