I. Biological treatment
The treatment processes used in biological treatment are: oxidation pond method, Carrousel, Alternate, Orbal, Phostrip method, Phoredox method, SBR method, AB method, Biofluidized 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, biofluidized bed wastewater treatment, immobilized cellular technology wastewater treatment, bio-iron method, growth hormone injection, integrated biochemistry plus filtration method, addition of flow carriers method, deep well aeration method, biofilter method, biological carousel method, tower biofilter biofilm method and other primary, secondary, deep treatment of municipal wastewater.
Treatment of phosphorus in sewage
The phenomenon of eutrophication of water bodies has led to the deterioration of water quality, seriously affecting people's production and life, nitrogen and phosphorus are the same as the important nutrients for aquatic organisms, but aquatic organisms, such as algae, are more sensitive to phosphorus to solve the problem of eutrophication of water, the first step is to remove the phosphorus from the sewage. With the progress of science and people's environmental awareness, sustainable development of phosphorus removal technology has become the development trend in the field of wastewater treatment research.
1, chemical phosphorus removal technology The basic principle of chemical phosphorus removal is the formation of insoluble phosphate precipitates through the addition of chemicals, and ultimately through the solid-liquid separation method so that phosphorus is removed from the sewage. Its main research direction focuses on the optimization of the selection of chemical agents. Chemical precipitation is a practical and effective technology, the advantages are: simple operation, good phosphorus removal, treatment efficiency of up to 80% to 90%, and the effect is stable, will not re-release of phosphorus and lead to secondary pollution, when the influent concentration fluctuates greatly, there is still a better effect of phosphorus removal. Disadvantages are: the amount of drugs used in this method, treatment costs are higher, and produce a large number of chemical sludge. Generally divided into two kinds: chemical precipitation and chemical flocculation method:
Chemical precipitation method:
Chemical precipitation method of phosphorus removal mainly refers to the application of calcium salts, iron salts and aluminum salts and other metal ions generated by phosphate and phosphate to generate insoluble phosphate precipitates to remove phosphorus from wastewater. The most commonly used are lime, aluminum sulfate, sodium aluminate, ferric chloride, iron sulfate, ferrous sulfate and ferrous chloride.
Chemical flocculation
Chemical coagulation removes phosphorus by converting soluble phosphorus into suspended phosphorus and retaining it. Most of the phosphorus in the water is dissolved inorganic chemosynthetic phosphorus, mainly detergent orthophosphate and thick ring phosphate, the remaining small portion of the organic chemosynthetic phosphorus in a dissolved and non-dissolved state. Thick cyclic phosphates and organically synthesized phosphorus can generally be converted to orthophosphate in biological treatments. Since phosphate has the most prominent effect on the hydrolysis behavior of ferrous ions among the various anions, it can replace some of the hydroxyl groups bound to ferrous ions to form alkaline ferric phosphate complexes and change the hydrolysis path of ferrous ions.
2, biological phosphorus removal technology
Biological phosphorus removal process is an economical method of phosphorus removal, can effectively remove phosphorus, without affecting the removal of total nitrogen, low operating costs, and can avoid the chemical phosphorus removal method produces a large amount of chemical sludge. Among them, denitrification phosphorus removal process is the hot spot of current research. The biological uptake/emission of phosphorus by denitrifying bacteria has been confirmed by researchers from the Delft University of Technology and the University of Tokyo, and is named "denitrification and phosphorus removal". DPB can use O2 or NO3 as electron acceptors. Under anaerobic conditions, COD is degraded to low molecular fatty acids such as acetic acid (HAC), which can be taken up by DPB for reproduction and hydrolysis of intracellular Poly-P, which is released as inorganic phosphate. Under anoxic conditions, DPB utilizes nitrate nitrogen as an electron acceptor for biophosphate uptake, while nitrate nitrogen is reduced to nitrogen gas. The denitrification and phosphorus removal process combined with DPB can save a considerable amount of COD and aeration, which also means less cell synthesis. Foreign research on denitrification phosphorus removal is relatively early, compared with conventional biological denitrification phosphorus removal process, denitrification phosphorus removal requires 30% less COD (calculated as domestic wastewater). Denitrification phosphorus removal technology has been gradually applied from basic research to practical engineering. To meet the environment and substrate required for DPB representative of the process for a single-stage process (BCFS) and two-stage process (A2N).
3 Chemistry-assisted biological phosphorus removal
Biological phosphorus removal due to the stability and flexibility of the poor, susceptible to carbon, pH and other factors, the phosphorus content of the effluent often does not meet the national emission standards, biological phosphorus removal process stability can be improved by additional chemical precipitation. Chemical combined with biological phosphorus removal technology research is relatively hot. One of the side stream phosphorus removal (Phsostrip) process of research is y concerned about, the process can ensure that the phosphorus value of the effluent below 1mg / L, although it is not yet possible to achieve the national level A standard, but from the stability of the phosphorus removal process, phosphorus removal efficiency, the convenience of the final disposal of sludge and indirectly save the operating costs, there are other phosphorus removal process is incomparable to the advantages of the process
4 Phosphorus Recovery of Wastewater Recovery
Guano stone (MgNH4PO4-6H20) precipitation method for phosphorus removal, this method can simultaneously remove and recover phosphorus, nitrogen and two nutrients, especially in some of the same time containing phosphorus, nitrogen wastewater, the application of guano stone precipitation to achieve the recovery of phosphorus in this type of wastewater only need to be added to the wastewater magnesium source and appropriate adjustment of pH, and therefore more convenient. Guano stone is a kind of excellent quality of phosphorus fertilizer, 100m3 sewage can be crystallized out of 1 kg of guano stone, if all countries are carried out sewage guano stone recycling, it can be 63,000t of phosphorus per year (to P2O5), thus saving the mining of phosphorus ore 1.6%. Some studies have shown that sludge recovery of phosphorus can reduce the mass of sludge dry solids, phosphorus recovery after sludge incineration will produce a significant decrease in the amount of ash, and guano stone phosphorus removal process produces a small volume of sludge, only 49% of the volume of sludge produced by chemical phosphorus removal.
Two, the cycle of intermittent aeration
China's level of economic development varies greatly from place to place, economic development lagging behind the city has not been able to come up with a lot of money for sewage treatment, so how to utilize the limited funds to reduce environmental pollution is a problem faced by many city governments. In terms of sewage treatment, until recently, some cities still use a level or a level of enhanced treatment process technology, the water does not meet the national secondary emission standards for the removal of organic pollutants. Cyclic intermittent aeration process to give full play to the advantages of high-load oxidation ditch treatment efficiency, but also make full use of sequential batch activated sludge wastewater treatment process of good water characteristics, to ensure that the system effluent to meet the national sewage discharge standards in the first level of organic pollutants in addition to the requirements of the requirements. In the investment and operating costs than usually to remove organic pollutants mainly in the secondary biological sewage treatment system to reduce about 30%, is suitable for China's current stage of sewage treatment requirements of the technology.
Three, rotary contact oxidation
Rotary contact oxidation wastewater treatment process technology is based on biological turntable technology, combined with the advantages of biological contact oxidation technology developed a new generation of aerobic biofilm treatment technology. Rotary contact oxidation sewage treatment process technology and complete sets of equipment provides a simple and reliable sewage treatment method. The rotating shaft is the only rotating part of the entire wastewater treatment system, and once the machine breaks down, it can be repaired by general mechanical personnel. The system biomass automatically compensates for changes in organic load. The microorganisms attached to the rotor are alive, when the organic matter in the sewage increases, the microorganisms increase with it, and on the contrary, when the organic matter in the sewage decreases, the microorganisms decrease with it. So the working effect of this wastewater treatment system is not easily affected by sudden changes in flow and load and power outages. Operating costs are low, only one-eighth to one-third of the power consumption of other aeration wastewater treatment systems. The footprint is only half that of conventional activated sludge. Due to the variety of microorganisms growing in the biological system, it is able to efficiently treat a variety of difficult to degrade industrial wastewater.
Four, continuous cyclic aeration
Continuous Cycle Aeration System process (Continuous Cycle Aeration System) is a continuous water intake SBR aeration system. Sewage treatment process CCAS is improved on the basis of SBR (Sequencing Batch Reactor, sequencing batch processing method).CCAS sewage treatment process does not require high pretreatment of sewage, only set up a gap of 15mm mechanical grating and sand sedimentation tank. The core of biological treatment is CCAS reaction tank, phosphorus removal, denitrification, degradation of organic matter and suspended solids and other functions are completed in the tank, the effluent can be discharged.
Unique advantages on the sewage treatment process CCAS:
(1) Aeration, CCAS sewage treatment of sewage and sludge is in a completely ideal mixing state, to ensure that the removal rate of BOD, COD, the removal rate of up to 95%.
(2) The repeated operation mode of "aerobic-anoxic" and "aerobic-anaerobic" strengthens the absorption of phosphorus and nitrification-denitrification, so that the removal rate of nitrogen and phosphorus reaches more than 80%, which ensures that the effluent indicators are qualified.
(3) sedimentation, the entire CCAS reaction pool is in a completely ideal precipitation state, so that the effluent suspended solids is very low, low value also ensures the removal of phosphorus.
The disadvantage of CCAS sewage treatment process is that the pools run intermittently at the same time, manual control is almost impossible, all rely on computer control, the quality of management personnel in the treatment plant requires high quality, design, training, installation, commissioning and other work requirements are more stringent.
Five, aeration biofilter
Sewage treatment process introduction: aeration biofilter, that is, in the biofilter treatment device is set up in the filler, through the man-made oxygen supply, so that the filler grows on a large number of microorganisms. This sewage treatment process flow device consists of a filter bed, gas distribution device, water distribution device, drainage device and other components. The aeration device adopts the supporting special aeration head, and the small and medium-sized bubbles produced are repeatedly cut by the packing to achieve the effect of close to micro-controlled aeration. Due to the high concentration of sludge in the reaction tank, the treatment facilities are compact, which can greatly save the floor space and reduce the reaction time.
Six, SPR phosphorus removal process
Sewage treatment process process introduction: the main reason for eutrophication of water bodies is that human beings discharged a large amount of ammonia nitrogen and phosphorus into the water body, phosphorus is the most important factor in the eutrophication of water bodies. Throughout the domestic sewage treatment process technology, phosphorus removal technology has been a problem for the operation of sewage treatment plants. The traditional physical phosphorus removal technology requires a large number of agents, with high operating costs, sludge production shortcomings; anterior anaerobic biological phosphorus removal process has the advantage of low operating costs, but due to the complete reliance on microbial phosphorus uptake, phosphorus release, it is difficult to meet the requirements of the national wastewater treatment process flow. When considering water reuse, it is more difficult to meet the requirements.
Seven, A/O biofilter
Sewage treatment process: due to China's small towns and villages scattered, the distribution of sewage sources more than a small amount of town-level sewage treatment plant scale is less than 10,000 tons / day. Domestic large and medium-sized urban sewage treatment plants often used in sewage treatment processes are traditional activated sludge, A2 / O, SBR, oxidation ditch, etc., if these technologies to build small town sewage treatment plant will result in high operating costs, can not be sustained operation. Must be used for the characteristics of small town investment, low operating costs, stable and reliable technology, operation and management of relatively simple process.
Eight, MBFB membrane biological
MBFB process for deep sewage treatment, the original sewage can meet the discharge standards on the basis of biological fluidized beds and ceramic membrane separation system, to further reduce COD, NH-N, turbidity and other indicators, on the one hand, can be directly reused, on the other hand, can also be used as a RO desalination pre-treatment process, replacing the original sand filter, security filtration, ultrafiltration and other lengthy filtration process. 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, and at the same time, the reduction of the organic content greatly improves the service life of the RO membrane and reduces the cost of reuse water treatment.