Polyaluminum chloride is a widely used flocculant. Many WWTP designs use polyaluminum chloride as a flocculant. The designer determines the residence time of sewage in the flocculation tank through scientific calculation. With the fluctuation of sewage volume and the improvement of drainage standards, some sewage stations have insufficient residence time of flocs, resulting in the effluent easily exceeding the standard.
        For this kind of problem, some suggestions are given.

1. Match the suitable polyacrylamide

The combination of polyaluminum chloride and suitable polyacrylamide can improve the speed of floc sedimentation. Therefore, the residence time of the flocs is insufficient. The first solution that comes to mind is to use polyacrylamide, which can speed up the settling speed.

2. Select the polyaluminum chloride with appropriate salinity

Different sewage components are suitable for polyaluminum chloride with different salinity. Recently, we are debugging a crystal cleaning sewage station. Through the comparison of polyaluminum chloride with different salinity, it is found that polyaluminum chloride with a salinity of about 60 has the best effect. Therefore, polyaluminum chloride with suitable salinity can be selected to improve the flocculation effect of sewage.

3. Add polydimethyldiallyl ammonium chloride to the liquid polyaluminum chloride

Polydimethyldiallyl ammonium chloride is a cation that can exist stably in polyaluminum chloride, and its presence can improve the electrical neutralization performance of polyaluminum chloride. For some particularly difficult wastewater, polydimethyldiallyl ammonium chloride can be added to the liquid polyaluminum chloride, which can greatly improve the performance of polyaluminum chloride.