The sludge buffer tank can be used for a variety of purposes. The most common application is the blending and homogenization of highly concentrated primary, secondary or digested sludge. The solution used to mix the sludge itself, or to mix the sludge with the dosed thickening chemicals, depends on the design and volume of the sludge buffer tank. Submersible mixer types ABS XRW and RW, as well as the agitator type Scaba, can be used to provide highly efficient mixing. Positive displacement, progressing cavity transfer pumps and Muffin Monster™ grinders are used for solids reduction and sludge transfer from sludge feed to sludge dewatering process.

Treated wastewater may occasionally require further treatment. Local discharge rules may pose strict limits that cannot be fulfilled by even the most effective process, or a higher quality of effluent may be requested for its reuse. When tertiary treatment is needed, various levels of filtration can be applied, including very fine filtration. Often, however, a final step of mixing and aeration is sufficient to achieve the target. When this is the case, Sulzer's submersible mixer types ABS XRW and RW can be used, along with submersible aerator type ABS TA–TAK and disc diffuser system types ABS PIK, DS and Sucoflow.