Modern wastewater treatment methods are divided into physical treatment, chemical treatment and biological treatment of three categories.

 

Physical treatment by physical separation, recovery of undissolved wastewater was suspended pollutants (including oil film and oil beads) of the wastewater treatment can be divided into gravity separation, centrifugation and screening methods such as screening. Belongs to the gravity separation of the processing unit are: precipitation, floating (flotation), the corresponding processing equipment is grit chamber, sedimentation tank, grease trap, flotation pond and its ancillary devices. Centrifugal separation itself is a processing unit, the processing device used centrifuges and hydrocyclones and so on. Screening and interception of law there are two kinds of grid screen retention and filtration unit, the former processing equipment is the grille, screen, which uses the sand filter and microporous filter and so on. The treatment method based on the principle of heat exchange also belongs to the physical treatment method, and the treatment unit has evaporation and crystallization.

 

Chemical treatment by chemical reaction and mass transfer to separate the role of wastewater was dissolved in the dissolved, colloidal state pollutants or its conversion into harmless substances wastewater treatment. In the chemical treatment method, the treatment units based on the chemical reaction for adding chemical agents are: coagulation, neutralization, redox and the like; while the mass transfer-based treatment units include extraction, stripping and stripping , Adsorption, ion exchange and electrodialysis and reverse osmosis. The latter two processing units are collectively referred to as membrane separation technology. Among them, the processing unit that uses mass transfer has both the chemical action and the related physical action, so it can also be separated from the chemical treatment method and becomes another kind of treatment method, which is called physical chemistry method.

 

Biological treatment through microbial metabolism, the wastewater was in solution, colloidal and fine suspended organic pollutants, into a stable, harmless substances in wastewater treatment. According to the role of different microorganisms, biological treatment can be divided into aerobic biological treatment and anaerobic biological treatment of two types.

 

Biological treatment of wastewater is widely used aerobic biological treatment, according to the traditional, aerobic biological treatment is divided into two types of activated sludge and biofilm. Activated sludge process itself is a processing unit, which has a variety of operating methods. Biofilm process equipment are biofilters, biological rotary plate, biological contact oxidation ponds and the recent development of biological fluidized bed. Biological oxidation pond method, also known as natural biological treatment.

 

Anaerobic biological treatment, also known as biological reduction treatment, mainly for the treatment of high concentrations of organic wastewater and sludge. The main processing equipment used is the digester.

 

Wastewater contaminants are varied and it is not possible to expect all the contaminants to be depleted by one treatment unit, often after having been processed by a treatment system consisting of several methods and several treatment units to meet the requirements . At present, wastewater treatment mainly uses pretreatment (physical + chemical method) - biochemical treatment (activated sludge method, biofilm method) - deep treatment (physical method)