Characteristics of urban domestic sewage and common treatment chemicals.
1. Characteristics of urban domestic sewage
a. Large changes in water quality:
Due to the different scale and nature of urban industries and the different proportions of domestic sewage, the water quality of urban sewage varies greatly. The quality of urban sewage varies greatly not only due to its different industrial structure, but even in towns with the same industrial structure, the quality of sewage discharged varies greatly. Even in the same town, the quality of sewage discharged will change greatly in different seasons and at different times of the day.
b. Large changes in water volume:
Urban sewage is affected by the local population, especially the large number of migrant workers in economically developed towns, and the mobility is relatively strong. Therefore, the amount of sewage may change greatly with the seasons and holidays within a year, and even the amount of sewage will be different at different times of the same day.
c. The collection system is greatly affected by rainfall:
At present, there are few diversion drainage systems established in built towns, and urban sewage treatment plants are directly affected by the urban drainage system and rainfall.
d. The wastewater contains a large amount of grease, food residues, etc., with high suspended matter and high chromaticity.
e. The wastewater contains a large amount of residual food, etc., which makes the wastewater smell strong and easy to stink.
f. The organic matter concentration of the wastewater is high, and the nitrogen and phosphorus sources are also high. Direct discharge is easy to cause eutrophication of the water body.
2. Urban domestic sewage treatment agents
a. Flocculant: polyaluminum chloride (used for flocculation, which can reduce SS, COD, and total phosphorus)
polyacrylamide (anions are generally used for flocculation and accelerated precipitation, and cations are generally used for sludge dehydration)
b. Phosphorus removal agent: iron salt, aluminum salt, calcium salt.
