Industrial wastewater is diverse and complex in composition, including:
Industrial wastewater containing suspended matter: such as papermaking wastewater, printing and dyeing wastewater, pig farm wastewater, fertilizer plant wastewater, traditional Chinese medicine wastewater, food processing wastewater, etc.
Industrial wastewater containing inorganic matter: including salt wastewater, heavy metal wastewater, acid and alkali wastewater, etc., mainly from the discharge of electronics, power industry, chemical pharmaceuticals, fine chemicals and other industries.
Industrial wastewater containing organic matter: such as chemical wastewater, pharmaceutical wastewater, pesticide wastewater, printing and dyeing wastewater, etc., this type of wastewater usually contains a large amount of organic matter and is difficult to treat.
Characteristics of desulfurization wastewater from coal-fired power plants
1. Complex composition
Contains heavy metals such as mercury and lead.
2. Highly corrosive
pH 4-6
3. Scaling risk
Calcium carbonate and other scaling materials > 3%
4. Treatment method 1:
Desulfurization wastewater → wastewater tank → wastewater pump → pH neutralization tank → sedimentation tank → flocculation tank → clarifier → outlet tank → outlet pump → standard discharge
The desulfurization wastewater treatment system includes three parts: wastewater treatment, dosing, and sludge treatment.
The wastewater treatment system is mainly composed of wastewater tanks, triple tanks, clarifiers, sludge pumps, outlet tanks, clean water pumps, fans, dehydrators and other equipment. In addition to a large amount of Cl- and Mg2+, the impurities in desulfurization wastewater also include heavy metal ions such as fluoride and nitrite, such as Cu2+, Hg2+, etc. In order to meet the wastewater discharge standards, corresponding wastewater treatment equipment must be equipped.
5. Treatment method 2:
Desulfurization wastewater → pre-sedimentation tank (remove 60% of suspended solids) → [pH adjustment tank (add calcium hydroxide to pH 9-9.5)] → sedimentation tank (add organic sulfur + coagulant) → [tubular microfiltration membrane (replace traditional clarifier, SS removal rate > 95%)] → clean water tank (pH adjusted to 6-9) → [DTRO membrane (dechlorination rate > 95%)] → discharge up to standard
Characteristics of chemical industry wastewater
1. Complex composition
Contains a variety of organic and inorganic substances, such as aromatic compounds, heavy metals, etc.;
2. High toxicity
Often contains toxic and harmful substances, which are very harmful to organisms
3. Large changes in pH
May be strongly acidic or alkaline; many difficult-to-degrade substances, and some organic substances are difficult to degrade by conventional methods;
3. Many difficult-to-degrade substances
Some organic substances are difficult to degrade by conventional methods; high salt content, some chemical wastewater has a high salt content.
4. Treatment method 1:
The primary treatment mainly separates suspended solids, colloids, floating oil or heavy oil in the water, and can adopt water quality and water quantity adjustment, natural sedimentation, floating and oil separation methods.
The secondary treatment mainly removes organic dissolved substances and some colloids that can be biodegraded, reduces the biochemical oxygen demand and some chemical oxygen demand in the wastewater, and usually adopts biological treatment. A considerable amount of COD remains in the wastewater after biological treatment, sometimes with high color, smell and taste, or due to high environmental sanitation standards, so a tertiary treatment method is required for further purification.
Tertiary treatment is mainly to remove organic pollutants and soluble inorganic pollutants that are difficult to biodegrade in wastewater. Commonly used methods include activated carbon adsorption and ozone oxidation, and ion exchange and membrane separation technologies can also be used.
5. Treatment method 2:
Pretreatment: Advanced oxidation: Fenton reagent to treat difficult-to-degrade COD, with a removal rate of 40-70%, electrocatalytic oxidation: BDD electrode to treat cyanide-containing wastewater, with a current efficiency of 85%
Biological treatment: Anaerobic process: IC reactor, aerobic process: MBBR filler biofilm method, sludge concentration 8-12 g/L.
Characteristics of printing and dyeing industrial wastewater
1. Main characteristics
The water consumption is large, and the wastewater produced is large. The dye makes the wastewater appear very dark in color, and the high chroma is difficult to remove.
2. Treatment method: Wastewater can be recycled and reused according to the characteristics of water quality.
Harmless treatment: physical treatment, chemical treatment, biological treatment, etc.
Physical treatment method
Adsorption materials: activated carbon, bentonite, industrial waste residue (such as fly ash) or new adsorbents (such as MOFs materials).
Function: Remove dye molecules (especially cationic dyes) and some heavy metals.
Membrane separation technology
Type: ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO).
Application: interception of macromolecular dyes (such as active dyes), salt recovery (such as RO concentrate reuse).
Coagulation/flotation method
Reagents: PAC (polyaluminum chloride), PAM (polyacrylamide), iron salts, etc.
Effect: Remove suspended solids, colloidal substances and some hydrophobic dyes (such as disperse dyes).
Chemical treatment method
Advanced oxidation technology (AOPs)
Ozone oxidation: Direct oxidation of chromophores (such as -C=N-, -N=N-), the decolorization rate can reach more than 90%.
Electrochemical oxidation: Mineralization of difficult-to-degrade organic matter through electrode reaction (such as BDD electrode).
Reduction method
Zero-valent iron (ZVI): Reduction of azo dyes (-N=N- cleavage to generate amino compounds).
Biological treatment method
Aerobic biological treatment
Activated sludge method: Targeted at easily degradable organic matter (such as starch slurry), but poor decolorization effect on dyes.
Biofilm method (MBBR): Carrier biofilm increases bacterial abundance and tolerates moderate concentrations of toxic substances.
Anaerobic biological treatment
UASB/EGSB reactor: Hydrolysis and acidification of macromolecular organic matter (such as PVA slurry), coupled with methane production.
Key to decolorization: Azoreductase secreted by anaerobic bacteria cuts off the dye chromophore.
Composite bacterial agent technology
Functional bacteria: white rot fungi (secreting lignin peroxidase), sphingomonas (degrading aniline substances).
Application: For desizing wastewater containing PVA (polyvinyl alcohol) and surfactants.
Characteristics of food industry wastewater
1. Main characteristics
The food industry has a wide range of raw materials and a wide variety of products. The amount and quality of wastewater discharged vary greatly; the content of organic matter and suspended solids is high and easy to corrupt. Its main harm is to eutrophicate the water body, causing the death of aquatic animals and fish, causing the organic matter deposited on the bottom of the water to produce odor, deteriorating water quality and polluting the environment.
2. Treatment method:
In addition to appropriate pretreatment according to the characteristics of water quality, biological treatment is generally recommended. If the effluent quality requirements are very high or the organic content in the wastewater is very high, an aeration tank, a biological filter, or a multi-stage biological rotary disc can be used in combination with two biological treatment devices, or anaerobic and aerobic series can be used.
Characteristics of dye production wastewater
1. Main characteristics
Contains substances such as acids, alkalis, salts, halogens, hydrocarbons, amines, nitro compounds, dyes and their intermediates, and some also contain pyridine, cyanide, phenol, benzidine, and heavy metals such as mercury, cadmium, and chromium. These wastewaters are complex in composition, toxic, and difficult to treat.
2. Treatment methods:
Appropriate treatment methods should be selected according to the characteristics of wastewater and its discharge requirements. For example, coagulation and filtration can be used to remove solid impurities and inorganic matter; chemical oxidation, biological method and reverse osmosis are mainly used to remove organic matter and toxic substances; decolorization can generally adopt a process consisting of coagulation and adsorption, and ion exchange can be used to remove heavy metals.
Characteristics of pesticide wastewater
1. Main characteristics
There are many varieties of pesticides, and the water quality of pesticide wastewater is complex. The concentration of pollutants is high, and the chemical oxygen demand (COD) can reach tens of thousands of mg per liter; the toxicity is high. In addition to pesticides, the wastewater also contains toxic substances such as phenol, arsenic, mercury, and many substances that are difficult to degrade by organisms; there is a foul odor, which is irritating to the human respiratory tract and mucous membranes; the water quality and water volume are unstable.
2. Treatment methods:
There are activated carbon adsorption, wet oxidation, solvent extraction, distillation and activated sludge methods.
Characteristics of cyanide-containing wastewater
1. Main characteristics
Cyanide-containing wastewater Cyanide-containing wastewater mainly comes from electroplating, coal gas, coking, metallurgy, metal processing, chemical fiber, plastics, pesticides, chemical industry and other departments. Cyanide-containing wastewater is a highly toxic industrial wastewater, which is unstable in water and easy to decompose.
2. Treatment method:
Reform the process to reduce or eliminate the discharge of cyanide-containing wastewater. For example, the use of cyanide-free electroplating can eliminate the industrial wastewater in the electroplating workshop. Wastewater with high cyanide content should be recycled, and wastewater with low cyanide content should be purified before discharge. The recycling methods include acid aeration, alkali solution absorption method, steam desorption method, alkaline chlorination method, electrolytic oxidation method, pressurized hydrolysis method, biochemical method, biological iron method, ferrous sulfate method, air stripping method, etc. Among them, alkaline chlorination method is widely used.
Characteristics of phenol-containing wastewater
1. Main characteristics
Phenolic wastewater Characteristics of phenol-containing wastewater: mainly from industrial sectors such as coking plants, gas plants, petrochemical plants, insulation materials plants, and petroleum cracking to produce ethylene, synthetic phenol, polyamide fibers, synthetic dyes, organic pesticides and phenolic resin production processes. It contains phenolic compounds, which are a kind of protoplasmic poison that can coagulate proteins.
2. Treatment methods:
Physical adsorption method, chemical vapor dephenolization method, solvent extraction method, chemical oxidation method, activated sludge method, biofilm method, biological contact oxidation method, etc.
Characteristics of mercury-containing wastewater
1. Main characteristics
Mainly from non-ferrous metal smelters, chemical plants, pesticide plants, paper mills, dye plants and thermal instrumentation plants. Its toxicity varies greatly, such as methylmercury, which is easily absorbed by the human body, not easy to degrade, excreted very slowly, and easily accumulated in the brain.
2. Treatment methods:
Chemical precipitation method, reduction method, ion exchange method, etc.
Characteristics of heavy metal wastewater
1. Main characteristics
Wastewater mainly comes from mining, smelting, electrolysis, electroplating, pesticides, medicines, paints, pigments and other enterprises. It contains a variety of metal ions, such as copper, zinc, etc. The metal toxicity is different. Some are more toxic and harmful. Some metal ions are easy to form insoluble precipitates under certain conditions.
2. Treatment method:
The heavy metals in the wastewater are converted into insoluble metal compounds or elements, and removed from the wastewater by precipitation and flotation. Applicable methods include neutralization precipitation, sulfide precipitation, flotation separation, electrolytic precipitation (or flotation), diaphragm electrolysis, etc.
The heavy metals in the wastewater are concentrated and separated without changing their chemical form. The applicable methods include reverse osmosis, electrodialysis, evaporation and ion exchange. These methods should be used alone or in combination according to the quality and amount of wastewater.
Characteristics of metallurgical wastewater
1. Main characteristics
Large amount of water, many types, complex and changeable water quality. According to the source and characteristics of wastewater, there are mainly cooling water, pickling wastewater, washing wastewater, slag flushing wastewater, coking wastewater, and wastewater condensed, separated or overflowed from production.
2. Treatment methods:
Develop and adopt new processes and technologies that do not use water or use less water and are pollution-free or less polluting, such as dry quenching, coking coal preheating, direct desulfurization and decyanation from coke oven gas, etc.;
Develop comprehensive utilization technologies, such as recovering useful substances and heat energy from wastewater and waste gas to reduce material and fuel loss;
According to different water quality requirements, comprehensive balance, serial use, and at the same time improve water quality stabilization measures to continuously improve the recycling rate of water;
Develop new treatment processes and technologies suitable for the characteristics of metallurgical wastewater, such as using magnetic method to treat steel wastewater. It has the advantages of high efficiency, small footprint, and convenient operation and management.
Characteristics of acid-base wastewater
1. Main characteristics
It mainly comes from steel mills, chemical plants, dye plants, electroplating plants and mines, etc. It contains various harmful substances or heavy metal salts. The mass fraction of acid varies greatly, ranging from less than 1% to more than 10%. Characteristics of alkaline wastewater: It mainly comes from printing and dyeing plants, leather factories, paper mills, oil refineries, etc. It contains organic alkali or inorganic alkali. The mass fraction of alkali is higher than 5% and lower than 1%. In addition to acid and alkali, acid-base wastewater also contains acid salts, basic salts and other inorganic and organic substances. Acid-base wastewater is highly corrosive.
2. Treatment methods:
High-concentration acid-base wastewater should be recycled first; low-concentration acid-base wastewater, such as the washing water of the pickling tank and the rinsing water of the alkali washing tank, should be neutralized. For neutralization treatment, the principle of treating waste with waste should be considered first. For example, acid and alkaline wastewater can be neutralized with each other, or waste alkali (slag) can be used to neutralize acidic wastewater, and waste acid can be used to neutralize alkaline wastewater. In the absence of these conditions, neutralizing agents can be used for treatment.
Characteristics of Ore Dressing Wastewater
1. Main Characteristics
It has a large amount of water, high content of suspended solids, and heavy metal ions and ore dressing agents contain many types of harmful substances. Heavy metal ions contain rare elements such as copper, zinc, lead, nickel, barium, cadmium, and arsenic.
2. Treatment methods:
Heavy metals can be removed by lime neutralization and roasted dolomite adsorption; ore adsorption and activated carbon adsorption can be used to remove flotation agents; cyanide-containing wastewater can be treated by chemical oxidation.
Characteristics of Oily Wastewater
1. Main Characteristics
It mainly comes from industrial sectors such as petroleum, petrochemicals, steel, coking, gas generation stations, and mechanical processing. The relative density of oil pollutants in wastewater is less than 1, except for heavy tar, which has a relative density of more than 1.1.
2. Treatment method:
First, use the oil separator to recover floating oil or heavy oil, with a treatment efficiency of 60%-80%, and the oil content in the effluent is about 100-200 mg/L; emulsified oil and dispersed oil in wastewater are difficult to treat, so the emulsification phenomenon should be prevented or reduced, usually using flotation and demulsification methods.