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).