In many wastewater treatment processes, the hydrolysis acidification process has been playing an important role in the pretreatment.

Hydrolysis refers to the degradation process of macromolecular organic substances in sewage. In this process, macromolecular organic substances should be hydrolyzed to micromolecular organic substances before further degradation.

Acidification refers to the accelerated degradation of organic substances in sewage. In this process, the hydrolyzed micromolecular organic substances will be further converted into simple compounds.

There are two basic functions of hydrolytic acidification tank:

(1) It can improve the biodegradability of sewage, and transform macromolecular organic substances into micromolecular organic substances.

(2) It can remove COD in sewage and degrade some organic substances.

Generally, elastic filler and combination filler are used in hydrolytic acidification tank. The three-dimensional elastic filler’s filaments are arranged in a three-dimensional uniform way, so that the gas, water and biofilm can be fully mixed and contacted and exchanged.

The microorganisms attached to the fillers in the tank, which can increase the contact area between sewage and microorganisms, so as to improve the treatment efficiency and effect of hydrolytic acidification tank.

The purpose of hydrolysis acidification process in aerobic biological treatment process is mainly to change the insoluble organic substances into the soluble organic substances, and to change the refractory organic substances into the easily biodegradable organic substances, so as to improve the biodegradability of the sewage and facilitate the subsequent aerobic treatment.

But in anaerobic digestion process, the purpose of hydrolysis acidification process is for to provide substrate for methane fermentation.

In the current sewage treatment installation and commissioning stage, hydrolytic acidification tank is used to cultivate the sludge. The cultivation of activated sludge is generally carried out in an intermittent way. Temporary water inlet pipe will be set, and artificial nutrition cultivation will be carried out according to the requirements. The sludge cultivation in the hydrolytic acidification tank will be a long time, so it is necessary to keep the balance of nutrients in the sludge.

Considering the energy consumption of subsequent aerobic treatment, the hydrolysis acidification process is mainly used in the pretreatment of low-concentration refractory wastewater.