Integrated sewage treatment equipment

Integrated sewage treatment equipment

National universal equipment, popular and best-selling equipment in the sewage treatment industry.

The integrated equipment adopts new processes, technologies, and materials, and is a new type of heavyweight equipment.

It has been well applied in domestic wastewater, medical wastewater, washing wastewater, slaughter wastewater, spraying wastewater, and similar industrial wastewater.

Biofilm system
Replace the anoxic and aerobic tanks in the A/O system with fixed biofilm reactors to form a biofilm denitrification system. There should be mixed liquid reflux in this system, but sludge reflux is not required. Two sludge systems suitable for denitrification, aerobic oxidation, and nitrification reactions are preserved in the anaerobic aerobic reactor.
Physical and chemical nitrogen removal
The commonly used physical and chemical methods for physical and chemical nitrogen removal include breakpoint chlorination, chemical precipitation, ion exchange, blow off, liquid membrane, electrodialysis, and catalytic wet oxidation.
Breakpoint chlorination method
The discontinuous point chlorination method is a chemical treatment method for treating ammonia nitrogen wastewater by oxidation, which uses the reaction between ammonia and chlorine in water to generate nitrogen gas and remove ammonia from the water. This method can also have a sterilizing effect and make some organic matter inorganic, but there is residual chlorine in the effluent after chlorination treatment, which should be further dechlorinated.

Add hypochlorous acid HClO to water containing ammonia. When the pH value is around neutral, the following main reactions gradually occur with the addition of hypochlorous acid:
NH3+HClO → NH2Cl+H2O ①
NH2Cl+HClO → NHCl2+H2O ②
NH2Cl+NHCl2 → N2+3H++3Cl- ③
When the ratio of chlorine to ammonia nitrogen (referred to as Cl/N) is below 5.07, the first reaction is carried out according to equation ① to generate monochloramine (NH2Cl), and the residual chlorine concentration in the water increases. Then, as the amount of hypochlorous acid increases, monochloramine reacts according to equation ② to generate dichloroamine (NHCl2), and at the same time, equation ③ is carried out to remove N in the water as N2. As a result, the concentration of residual chlorine in water decreases with the increase of Cl/N. When the Cl/N ratio reaches a certain value or above, the amount of unreacted hypochlorous acid (i.e. free residual chlorine) increases, and the concentration of residual chlorine in water increases again. The point at which this minimum value occurs is called a discontinuity point (commonly referred to as a inflection point). The Cl/N ratio at this time is theoretically calculated to be 7.6; In wastewater treatment, due to the reaction between chlorine and organic matter in the wastewater, the C1/N ratio should be higher than the theoretical value of 7.6, usually 10. In addition, when the pH is not within the neutral range, trichloroamine is generated more under acidic conditions, and nitric acid is generated under alkaline conditions, resulting in a decrease in denitrification efficiency.

SBR method, abbreviated as sequencing batch reactor, is an activated sludge wastewater treatment technology that operates in an intermittent aeration mode.
Its main feature is orderly and intermittent operation in operation. The core of SBR technology is the SBR reaction tank, which integrates functions such as homogenization, primary sedimentation, biodegradation, and secondary sedimentation into one tank, without a sludge reflux system. Especially suitable for occasions with intermittent emissions and significant flow changes.

Principle: Continuous air is introduced into wastewater, and after a certain period of time, sludge like flocs are formed due to the proliferation of aerobic microorganisms. It is home to a microbial community mainly composed of microbial clusters, which have strong abilities to adsorb and degrade organic matter.

SBR process: The SBR process consists of reactors that operate intermittently in a certain time sequence. The complete operation process of SBR technology, which includes the following five stages for each batch reactor in treating wastewater: ① inflow period; ② Response period; ③ Sedimentation period; ④ Drainage and mud discharge period; ⑤ Idle period. The operating conditions of SBR are characterized by intermittent operation. The operation cycle includes self inflow, reaction, sedimentation, drainage and sludge discharge until the end of the idle period. In a running cycle, the running time of each stage, changes in the volume of mixed liquid in the reactor, and the operating status can be flexibly controlled according to the specific properties of the sewage, effluent quality, and operational functional requirements.
advantage
(1) The process is relatively simple compared to other processes, and the disposal of excess sludge is less troublesome;
(2) Less land occupation, low operating costs, and investment savings;
(3) Resistant to impacts from organic and toxic loads, with flexible operating modes;
(4) Due to the static sedimentation, the effluent effect is good, the anaerobic and aerobic processes alternate, the mud age is short, and the activity is high;
(5) Has excellent denitrification and phosphorus removal effects.

Disadvantages:
(1) High requirements for automation control.
(2) The drainage time is short (intermittent drainage), and it is required not to stir the sediment layer during drainage, so specialized drainage equipment (decanter) is needed, and the requirements for the decanter are very high.
(3) The post-processing equipment requires large requirements, such as large disinfection equipment, large contact tank capacity, and large drainage facilities such as drainage pipes.
(4) The depth of decanting water is generally 1-2 meters, and this part of the head loss is wasted, increasing the total head.
(5) Due to the absence of a primary sedimentation tank, floating debris is prone to occur, and the problem of floating debris has not been properly resolved.
SBR technology is mainly applied in the following sewage treatment fields: urban sewage, industrial wastewater, mainly including monosodium glutamate, beer, pharmaceuticals, coking, catering, papermaking, printing and dyeing, washing, slaughtering and other industrial wastewater treatment.

The main technologies for treating ammonia nitrogen wastewater
At present, there are various methods for treating ammonia nitrogen wastewater at home and abroad, such as breakpoint chlorination, chemical precipitation, ion exchange, blow off, and biological denitrification. These technologies can be divided into two categories: physical and chemical methods and biological denitrification technologies.
Biological denitrification method
The process of microbial removal of ammonia nitrogen requires two stages. *The stage is the nitrification process, in which nitrifying bacteria and nitrifying bacteria convert ammonia nitrogen into nitrite nitrogen and nitrate nitrogen under aerobic conditions. The second stage is the denitrification process, in which nitrate and nitrite nitrogen in wastewater are reduced and converted into nitrogen by denitrifying bacteria (both heterotrophic and autotrophic microorganisms are found and diverse) under anaerobic or low oxygen conditions. During this process, organic compounds (such as methanol, acetic acid, glucose, etc.) are oxidized as electron donors to provide energy. The common biological denitrification processes can be divided into three categories, namely multi-stage sludge systems, single-stage sludge systems, and biofilm systems.

Multi stage sludge system
This process can achieve quite good BOD5 removal and denitrification effects, but its disadvantages include a long process, multiple structures, high infrastructure costs, the need for additional carbon sources, high operating costs, and residual methanol in the effluent.
Single stage sludge system
The forms of single-stage sludge systems include pre denitrification systems, post denitrification systems, and alternating working systems. The pre denitrification biological denitrification process, commonly known as the A/O process, has the advantages of simple process, fewer structures, lower infrastructure costs, no need for external carbon sources, and higher effluent quality compared to traditional biological denitrification processes. The post denitrification system, due to the lack of organic matter in the mixed solution, generally requires manual addition of carbon sources, but the denitrification effect can be higher than that of the pre denitrification system, theoretically approaching * denitrification. The alternating biological denitrification process mainly consists of two connected tanks, which operate alternately under anaerobic and aerobic conditions by changing the direction of inlet and outlet water. The system is essentially still an A/O system, but it uses an alternating working mode to avoid the reflux of the mixed liquid, resulting in a better denitrification effect than the general A/O process. Its disadvantage is that the operating and management costs are relatively high, and it is generally necessary to configure a computer-controlled automatic operating system.

The structure of the contact oxidation tank consists of an aeration system, packing material, and tank body. The aeration system provides oxygen to microorganisms attached to the packing material, allowing them to fully contact the sewage and decompose organic matter. It can be divided into diversion type and direct type. The diversion type aeration device is located on one side of the tank, and the packing is installed on the other side. It relies on the lifting effect of a pump or air to circulate the water flow in the packing layer and supply oxygen to the biofilm on the packing; The direct method involves blowing air directly at the bottom of the oxidation tank packing for aeration.
The treatment process of contact oxidation tank generally includes two methods: one-stage method (primary biological contact oxidation) and two-stage method (secondary biological contact oxidation).
One stage method: The raw water first passes through the regulating tank, then enters the biological contact oxidation tank, and then flows into the secondary sedimentation tank for sludge water separation.
Two stage method: The purpose of using the two-stage method is to increase the biological oxidation time, improve the efficiency of biochemical treatment, and better adapt to changes in raw water quality, so as to stabilize the treated water quality. After being regulated by the regulating tank, the raw water enters the biological contact oxidation tank and then flows into the intermediate sedimentation tank for mud water separation. The upper layer water continues to enter the second contact oxidation tank and finally flows into the secondary sedimentation tank for mud water separation again. The effluent is discharged, and the sludge in the sedimentation tank is regularly discharged.

With the change of practice, these two processes can also change accordingly: for example, dividing the contact oxidation tank into grids, not setting up an intermediate sedimentation tank, and operating according to the push flow pattern. The one-stage method has a simple and easy process, convenient operation, and lower investment, but its ability to degrade BOD is not as good as the two-stage method. The two-stage process has a good processing effect and can shorten the total time required for biological oxidation, but it increases the processing equipment and maintenance management work, and the investment is also higher than the one-stage process.

Generally speaking, when the organic load is low and the hydraulic load is high, it is better to use a one-stage method. When the organic load is high, it is more appropriate to use two-stage method or push flow method. The experiment shows that in the two-stage method, the volume ratio of the contact oxidation tank to the second contact oxidation tank should be 7:3. In the push flow process, it can be divided into grids according to the conditions of BOD changes (* grid maximum, gradually decreasing thereafter); It can also be divided into grids according to hydraulic load (each grid is of equal size).

contact oxidation tank
The structure includes the tank body, filling material, water distribution device, and aeration device. The working principle is to set up fillers in the aeration tank and use them as carriers for the biofilm. The wastewater to be treated flows through the packing material at a certain flow rate after oxygenation, and comes into contact with the biofilm. The biofilm and suspended activated sludge work together to purify the wastewater.
Contact oxidation method is a new wastewater biochemical treatment method that combines the characteristics of activated sludge method and biofilm method. The main equipment for this method is a biological contact oxidation filter. In an airtight aeration tank, there are fillers such as coke, gravel, and plastic honeycomb. The fillers are submerged in water and are aerated and oxygenated at the bottom of the fillers using a blower. This method is called blower aeration; Air can carry the wastewater to be treated from bottom to top, freely passing through the filter material to reach the ground. After the air escapes, the wastewater returns to the bottom of the pool from top to bottom in the filter material compartment. Activated sludge adheres to the surface of the packing material and does not flow with water. Due to the strong agitation of the rising airflow, the biofilm is constantly renewed, thereby improving the purification effect.

Reaction mechanism: Fill materials are set up in the tank, and aeration is carried out at the bottom of the tank to oxygenate the sewage and keep the sewage in a flowing state to ensure sufficient contact between the sewage and the filling materials in the sewage, avoiding the defect of uneven contact between sewage and filling materials in the biological contact oxidation tank. In this method, the oxygen demand of microorganisms is supplied by air blowing aeration. After the biofilm grows to a certain thickness, the microorganisms on the packing wall will undergo anaerobic metabolism due to hypoxia. The gas produced and the scouring effect formed by aeration will cause the biofilm to fall off and promote the growth of new biofilm. At this time, the fallen biofilm will flow out of the pool with the effluent.
Integrated sewage treatment equipmentPrinciple: Install packing material in the aeration tank as a carrier for the biofilm. Biofilms are composed of bacteria, fungi, and protozoa. These microorganisms rely on the organic matter adsorbed and precipitated on the membrane as nutrients, synthesizing some of the organic matter into cellular substances, which become active substances in cells; The other part is decomposed into metabolites, and the energy released during decomposition metabolism is used for microbial growth.

The concept of hydrolysis (acidification)
Hydrolysis in chemistry refers to a general term for a type of reaction between a compound and water. For example, the reaction of ester substances hydrolyzing to produce alcohols and organic acids. In wastewater biological treatment, hydrolysis refers to the biochemical reaction that occurs outside the cell before organic matter (matrix) enters the cell. The typical feature of this stage is that the site of biological reactions occurs outside the cell, and microorganisms complete the biocatalytic oxidation reaction by releasing extracellular free enzymes or fixed enzymes attached to the outer wall of the cell (mainly including the breaking of chains and water solubility of large molecular substances). Research has shown that many substances in nature, such as proteins, sugars, fats, etc., can be hydrolyzed smoothly under aerobic, anaerobic, or anaerobic conditions.
Acidification is a typical fermentation process. The basic characteristic of this stage is that the metabolic products of microorganisms are mainly various organic acids (such as acetic acid, propionic acid, citric acid, etc.). Hydrolysis bacteria are actually a type of fermentation bacteria with hydrolysis ability. Hydrolysis is an energy consuming process, and the purpose of fermentation bacteria investing energy in hydrolysis is to obtain a water-soluble substrate that can be fermented, and to obtain energy through intracellular biochemical reactions, while eliminating metabolites (mainly various organic acids under anaerobic conditions). In practical engineering, it is hoped that the acid production process can be controlled within the minimum range. Because acidification causes a significant decrease in pH, it is not conducive to hydrolysis.

The difference between hydrolysis (acidification) and anaerobic digestion
In principle, hydrolysis (acidification) is a two-stage anaerobic digestion process, but the goals pursued by hydrolysis (acidification) technology and anaerobic digestion are different, so they are completely different treatment methods. The main purpose of hydrolysis (acidification) system is to convert insoluble organic matter in raw water into dissolved organic matter, especially in industrial wastewater treatment. The main purpose is to convert difficult to biodegrade substances into easily biodegradable substances, improve the biodegradability of wastewater, and facilitate subsequent aerobic biological treatment. Considering the energy consumption issue of subsequent aerobic treatment, hydrolysis (acidification) is mainly used for the pretreatment of low concentration and difficult to degrade wastewater.

Acidification:
(1) Improve the biodegradability of wastewater: it can convert large organic molecules into small molecules.
(2) Removing COD from wastewater: Since it is a heterotrophic microbial bacterium, it must extract nutrients from the environment, so some organic matter must be degraded and synthesized into its own cells.