Industrial technology for sewage treatment

Process technology;

Biological treatment

The treatment processes used in biological treatment are: Oxidation pond method, Carrousel, alternating type, Orbal, Phostrip method, Phoredox method, SBR method, AB method, biological fluidized bed method, ICEAS method, DAT-IAT method, CASS (CAST, CASP) method, UNITANK method, MSBR method, A/O method, A2/O, A3/O, UCT method, ⅥP method, UASB method, integrated biochemical method, aerobic wastewater treatment, biological fluidized bed wastewater treatment, immobilized cell technology wastewater treatment, biological iron method, auxin method, integrated biochemical filtration method, increasing flow carrier method, deep well aeration Gas method, biological filter method, biological turntable method, tower biological filter biofilm method, etc., the first, second and deep treatment method of urban sewage.

Treatment of phosphorus in sewage

The phenomenon of water eutrophication has led to the deterioration of water quality and seriously affected people's production and life. Nitrogen and phosphorus are both important nutrients of water organisms, but aquatic organisms such as algae are more sensitive to phosphorus. To solve the problem of water eutrophication, phosphorus should be removed from sewage first. With the progress of science and the continuous improvement of people's environmental awareness, the sustainable development of phosphorus removal technology has become a development trend in the field of wastewater treatment research.

1. Chemical phosphorus removal technology The basic principle of chemical phosphorus removal is to form insoluble phosphate precipitates by adding chemical agents, and finally remove phosphorus from sewage by solid-liquid separation. His main research direction focuses on the optimal selection of chemical agents. Chemical precipitation method is a practical and effective technology, its advantages are: simple operation, good phosphorus removal effect, treatment efficiency of up to 80% ~ 90%, and the effect is stable, will not re-put phosphorus and lead to secondary pollution, when the influent concentration fluctuation, there is still a good phosphorus removal effect. The disadvantages are that the method uses a large amount of drugs, the treatment cost is high, and a large amount of chemical sludge is produced. Generally divided into two types: chemical precipitation method and chemical flocculation method:

Chemical precipitation method:

Phosphorus removal by chemical precipitation mainly refers to the method of removing phosphorus in wastewater by using metal ions produced by calcium salt, iron salt and aluminum salt and phosphoric acid to generate insoluble phosphate precipitate. The most commonly used are lime, aluminum sulfate, sodium aluminate, ferric chloride, ferric sulfate, ferrous sulfate, and ferrous chloride.

Chemical flocculation method

Phosphorus removal by chemical coagulation is to convert soluble phosphorus into suspended phosphorus and detain it. Most of the phosphorus in the water is dissolved inorganic combined phosphorus, mainly orthophosphate and thick cyclic phosphate of detergent, and the remaining small part is organic combined phosphorus that exists in dissolved and non-dissolved states. Condensed cyclic phosphates and organic combined phosphates are generally converted to orthophosphates in biological processing. Phosphoric acid has the most prominent effect on the hydrolysis behavior of iron ion among various anions, and it can replace part of the hydroxyl group bound with iron ion to form a complex complex of basic iron phosphate and change the hydrolysis path of iron ion.

2. Biological phosphorus removal technology

Biological phosphorus removal process is an economic phosphorus removal method, which can effectively remove phosphorus without affecting the removal of total nitrogen, low operating costs, and can avoid the chemical phosphorus removal method to produce a large amount of chemical sludge. Among them, denitrification and phosphorus removal technology is the focus of current research. The biological uptake/removal of phosphorus by denitrifying bacteria was confirmed in a collaborative study by researchers at the Technical University of Delft and the University of Tokyo, named "Denitrifying phosphorus removal". Denitrifying phosphorus removal bacteria (DPB) can use O2 or NO3 as electron acceptors. Under anaerobic conditions, COD can be degraded into low molecular fatty acids such as acetic acid (HAC) for absorption and propagation by DPB, while hydrolyzing intracellular Poly-P and releasing it in the form of inorganic phosphate. Under hypoxic condition, DPB uses nitric nitrogen as electron acceptor for biological phosphorus uptake, and nitric nitrogen is reduced to nitrogen. The denitrifying phosphorus removal process combined with DPB can save a considerable amount of COD and aeration capacity, but also means less cell synthesis. Compared with conventional biological denitrification and phosphorus removal process, the COD required for denitrification and phosphorus removal is reduced by 30%(calculated by domestic sewage). Denitrification and phosphorus removal technology has been gradually applied from basic research to practical engineering. Typical processes that meet the environment and substrate requirements of DPB are single-stage processes (BCFS) and two-stage processes (A2N).

3 Chemical assisted biological phosphorus removal

Due to the poor stability and flexibility of biological phosphorus removal, easily affected by carbon sources, pH value and other factors, the phosphorus content of the effluent often fails to meet the requirements of the national emission standards, and the stability of the biological phosphorus removal process can be improved by additional chemical precipitation. The research on chemical combined biological phosphorus removal technology is a hot topic. Among them, the research of the side-flow phosphorus removal (Phsostrip) process has attracted much attention, which can ensure that the phosphorus effluent value is below 1mg/L, although it cannot reach the national first-class A standard, but from the perspective of the stability of the phosphorus removal process, phosphorus removal efficiency, the convenience of the final disposal of sludge and the indirect saving of operating costs, there are incomparable advantages of other phosphorus removal processes

4. Recovery of phosphorus from sewage

Guanite (MgNH4PO4·6H20) precipitation method is used for phosphorus removal, this method can remove and recover phosphorus and nitrogen two nutrients, especially in some wastewater containing phosphorus and nitrogen, the application of guanite precipitation method to achieve phosphorus recovery in such wastewater only need to add magnesium source in the wastewater and adjust the pH properly, so it is more convenient. Struvite is a kind of excellent quality phosphate fertilizer, 100m3 sewage can be crystallized 1 kg struvite, if all countries are sewage struvite recovery, you can get 63,000 t of phosphorus (P2O5) per year, thus saving 1.6% of phosphate mining. Studies have shown that phosphorus recovery from sludge can reduce the dry solid mass of sludge, and the ash content generated by sludge incineration after phosphorus recovery will also be significantly reduced, and the sludge volume generated by struvite phosphorus removal process is very small, only 49% of the sludge volume generated by chemical phosphorus removal.

Cyclic intermittent aeration

The level of economic development in China varies greatly from place to place, and the cities with lagging economic development cannot devote a lot of funds to sewage treatment. Therefore, how to use limited funds to reduce environmental pollution is a problem faced by many city governments. In terms of sewage treatment, until recently, some cities also used first-level or first-level enhanced treatment technology, and the effluent did not meet the requirements of the national second-level discharge standards for the removal of organic pollutants. The cyclic intermittent aeration process gives full play to the advantages of high efficiency of high-load oxidation ditch treatment, and makes full use of the good characteristics of the effluent from the sequencing batch activated sludge sewage treatment process to ensure that the effluent of the system meets the requirements of the national sewage discharge standard in removing organic pollutants. The cost of investment and operation is about 30% lower than that of the secondary biological sewage treatment system which usually removes organic pollutants, and it is a process technology suitable for China's current sewage treatment requirements.

Rotary contact oxidation

Rotary contact oxidation wastewater treatment technology is a new generation of aerobic biofilm treatment technology developed on the basis of biological turntable technology and the advantages of biological contact oxidation technology. Rotary contact oxidation wastewater treatment technology and complete equipment provide a simple and reliable wastewater treatment method. The rotating shaft in the whole sewage treatment system is the only rotating part, and once the machine fails, the general mechanical personnel can carry out maintenance. The biomass of the system is automatically compensated according to changes in the organic load. The microorganisms attached to the turntable are living, and when the organic matter in the sewage increases, the microorganisms increase, and conversely, when the organic matter in the sewage decreases, the microorganisms decrease. Therefore, the working effect of this sewage treatment system is not easily affected by sudden changes in flow and load and power outages. Operating costs are low, and only one-eighth to one-third of the power consumption of other aerated sewage treatment systems. The footprint is only half that of the conventional activated sludge process. Because there are many kinds of microorganisms growing in the biological system, it can effectively treat all kinds of difficult to degrade industrial sewage.

Continuous cycle aeration

The Continuous Cycle Aeration System is a continuous water inlet SBR aeration system. The wastewater treatment process CCAS is improved on the basis of SBR (Sequencing Batch Reactor). CCAS wastewater treatment process does not have high requirements for wastewater pretreatment, and only has a mechanical grille with a gap of 15mm and a sand settling pond. The core of biological treatment is the CCAS reaction tank, in which the functions of phosphorus removal, nitrogen removal, degradation of organic matter and suspended matter are completed, and the effluent can be discharged up to the standard.

Unique advantages of CCAS wastewater treatment process:

(1) During aeration, the sewage and sludge treated by CCAS are in a completely ideal mixed state, ensuring the removal rate of BOD and COD, which is as high as 95%.

(2) The repeated operation mode of "aerobic - anoxic" and "aerobic - anaerobic" strengthened the phosphorus absorption and nitrification - denitrification, so that the removal rate of nitrogen and phosphorus reached more than 80%, ensuring that the effluent index was qualified.

(3) When precipitating, the entire CCAS reaction tank is in a completely ideal precipitation state, so that the suspended matter in the effluent is extremely low, and the low value also ensures the removal effect of phosphorus.

The disadvantage of CCAS wastewater treatment process is that the pools run intermittently at the same time, manual control is almost impossible, relying on computer control, and the quality of management personnel of the treatment plant is very high, and the design, training, installation, commissioning and other work requirements are stricter.

Biological aerated filter

Introduction to the sewage treatment process: aerated biological filter, that is, the filler is set in the biological filter treatment device, and a large number of microorganisms grow on the filler through artificial oxygen supply. The sewage treatment process device is composed of a filter bed, a gas distribution device, a water distribution device, a drainage device, etc. The aeration device adopts a special aerator head, and the small and medium-sized bubbles generated are repeatedly cut by the filler to achieve the effect of close to micro-controlled aeration. Due to the high sludge concentration in the reaction tank and the compact treatment facilities, the footprint can be greatly saved and the reaction time can be reduced.

SPR phosphorus removal process

The main reason for water eutrophication is that human beings discharge a large amount of ammonia nitrogen and phosphorus into the water, and phosphorus is the most important factor of water eutrophication. Throughout the domestic sewage treatment process, phosphorus removal technology has always been a difficult problem plaguing the operation of sewage treatment plants. The traditional physicochemical phosphorus removal technology requires a large number of agents, which has the disadvantages of high operating cost and large sludge yield. The pre-anaerobic biological phosphorus removal process has the advantage of low operating cost, but it is difficult to meet the requirements of the national sewage treatment process because it completely depends on the phosphorus uptake and phosphorus release of microorganisms. When the reuse of reclaimed water is considered, it is more difficult to meet the requirements.

Biological filter

Introduction to the sewage treatment process: Due to the scattered residential points of small towns in China, the distribution of sewage sources is more and less, and the scale of urban sewage plants is mostly less than 10,000 tons/day. The sewage treatment processes often used in domestic large and medium-sized urban sewage treatment plants include traditional activated sludge method, A2/O, SBR, oxidation ditch, etc. If these technologies are used to build small town sewage treatment plants, it will cause high operating costs and cannot be continuously operated. It is necessary to adopt the technology of less investment, low operating cost, stable and reliable technology, relatively simple operation and management according to the characteristics of small towns.

MBFB membrane organisms

The MBFB process is used for the advanced treatment of sewage, which can further reduce COD, NH-N, turbidity and other indicators on the basis of the standard discharge of the original sewage through the biological fluidized bed and ceramic membrane separation system. On the one hand, it can be directly reused, on the other hand, it can also be used as a pre-treatment process for RO desalination treatment, replacing the original sand filtration, security filtration, ultrafiltration and other lengthy filtration processes. At the same time, the reduction of organic content greatly improves the service life of RO membrane, reduces the cost of reuse water treatment, inorganic ceramic membrane separation system, is the world's first set of special inorganic membrane separation system for sewage treatment, compared with other organic membranes, inorganic membranes, with large membrane flux, recoil, automatic operation and other advantages.