Environmental sewage pretreatment process in hard degraded wastewater

Pretreatment is generally placed before primary treatment, including grid, screen, crushing, desanding, pre aeration, acid-base neutralization, etc. The pretreatment here is mainly to remove large volume pollutants, reduce the load of subsequent sewage treatment, improve the effect of subsequent sewage treatment, and reduce the overall cost of sewage treatment. In addition, pre-treatment also includes pre-treatment before biochemistry. The pre-treatment before biochemistry is mainly to reduce, remove or transform substances that are toxic and inhibitory to microorganisms into substances that are harmless or beneficial to microorganisms, so as to ensure the normal operation of the biochemical system.

Common pretreatment process

1. Pre sedimentation: When the raw water contains a large amount of silt, a pre sedimentation tank shall be set when the primary coagulation sedimentation and increased dosage are still difficult to meet the requirements for sedimentation effluent. The pre sedimentation tank can be used for sand setting, sedimentation (natural sedimentation, flocculation sedimentation), clarification, etc. When large sandy particles are mainly suspended in the water, the sedimentation tank can be used, while when clay particles are mainly suspended in the raw water, coagulation sedimentation, clarification and other coagulation sedimentation methods can be used.

2. Acid and alkali regulation: Adjust the pH value of raw water by mixing two streams of wastewater and adding acid and alkali regulators according to the requirements of subsequent water treatment.

3. Biological pretreatment: ammonia nitrogen, organics, etc. in the water are gradually and effectively removed by the comprehensive action of biological flocculation, adsorption, oxidation, biodegradation, nitrification, etc. of microorganisms, using their own life metabolism activities (oxidation, reduction, synthesis, etc.) attached to the filler.

4. Chemical pre oxidation: add oxidant before the coagulation process, which can remove trace organic pollutants, algae, odor, control chlorination by-products, remove iron and manganese, and play a role in coagulation.

In practical application, the wastewater pretreatment process needs to be analyzed and selected according to the actual water quality, and the process with high efficiency and economy should be selected to meet the requirements of stable operation, stable effluent and low cost of the subsequent process.