The most complete sewage treatment process introduction

AB process

The sewage enters section A directly from the drainage system through the grille and sand settling basin. This section is the adsorption section with high load, short mud age and short hydraulic residence time (about 30min), which is conducive to the growth and reproduction of microorganisms with fast growth rate. After the wastewater is treated in section A, BOD is removed by 40% ~ 70%, and the biodegradability is improved, which is conducive to the work of Section B. The sludge in Section A has a high yield and strong adsorption capacity, and heavy metals, refractory substances and plant nutrients such as nitrogen and phosphorus may be removed by sludge adsorption.

The sewage flows from section A into section B, which is the biological oxidation section and belongs to the traditional activated sludge method. It generally operates under a low load, with a residence time of about 2 ~ 6h and a longer mud age of 15 ~ 20d. Nitrification and partial denitrification occurred in section B, the activated sludge precipitation efficiency was good, and the effluent SS and BOD were generally less than 10mg/L.

The AB method has the following characteristics: there is no initial sedimentation tank, and the A section composed of adsorption tank and intermediate sedimentation tank is the primary treatment system; Section B is composed of aeration tank and secondary sedimentation tank. The two sections A and B have independent sludge return systems, and the two sections are completely separated, each composed of unique microbial communities, which is conducive to the stability of the function.

Tertiary treatment of sewage

After secondary biological treatment, the effluent generally contains: BOD30mg/L or so, COD60mg/L or so, NH315-25mg/L, P3-8mg/L,SS30mg/L or so, as well as bacteria, heavy metals, etc., must be treated, otherwise it is easy to lead to water eutrophication, and affect fish, crops, freshwater water quality and treatment costs.

The three stage treatment methods include: sand filtration, coagulation, microfiltration, reverse osmosis, electrodialysis, ion exchange, disinfection, activated carbon adsorption, nitrogen and phosphorus removal.

Removal of suspended solids

1. Particle size: secondary effluent SS is a biological flocculant of 1um~1mm and a colloidal substance that is not flocculated. It is generally removed by coagulation, sand filtration, microfiltration and reverse osmosis.

2. Coagulation and precipitation: by adding coagulant, rapid stirring and flocculation, slow stirring flocculation, so that small particles and colloidal substances are destabilized and condensed, and become larger particles and precipitation removal.

Dissolved organic matter removal

1. Activated carbon adsorption: activated carbon has a huge surface area and small pores, can absorb organic matter, heavy metal ions and so on.

2.O3 oxidation treatment: The secondary treatment water is treated for reuse, and strive to remove organic matter, chroma, sterilization and disinfection in the sewage.

Removal of dissolved inorganic salts

Hazard: corrosive, easy to scale, SO42- reduction to produce H2S, resulting in land hardening and salinization. Therefore, desalination is required before water reuse and agricultural use.

Desalination technology: reverse osmosis, electrodialysis, ion exchange.

Disinfection of sewage

Reason: No matter what process, the effluent bacteria will exceed the standard, which will bring harm.

Application occasions: sewage irrigation, upstream of discharge water source, tourist attractions, and epidemic season.

Disinfection methods: liquid chlorine, ozone, sodium hypochlorite and ultraviolet light