Sometimes it is necessary to mix chemicals into the activated sludge before it enters the secondary sedimentation tank. For example, chemicals may be used to perform phosphorous removal on the effluent from the biological process. Many plants use chemicals to improve sludge thickening just prior to the sludge buffer tank.

Chemicals must sometimes be mixed into the activated sludge before it enters the secondary sedimentation tank. Whenever this done, it is important to achieve an even distribution of the chemicals. Chemicals may be added to perform the chemical removal of phosphorous on effluent from the biological process. In other circumstances, chemicals such as cationic polyelectrolytes with a high molecular weight may be added to improve the quality and settling ability of flocs formed in the activated sludge process.

The task of mixing in the equalization process is to blend the wastewater in order to prevent sedimentation, stratification and odor formation. It may also be necessary to mix and homogenize wastewater streams that arrive from different sources. Because the water level in the equalization tanks varies significantly and can sometimes be very low, high demands are placed upon the mixers.

Sulzer has a deep knowledge in wastewater treatment, and with our wide product portfolio we can now offer energy-efficient and reliable solutions for your water collection, neutralization, flocculation, sedimentation, cooling, aeration, sludge storage, digestion, and dewatering processes.

Inlet pumping stations are somewhat similar to large terminal pumping stations. Depending on the depth of the incoming sewer, the lifting heads can range from around 2 up to 30 meters. To prevent hydraulic shock loads, which negatively impact the biological process, the stations often make use of variable-speed drives and/or several pumps in parallel.

When denitrification is followed by a physically separated nitrification step, the nitrates formed during nitrification must be recirculated. The nitrates are pumped back into the denitrification step, where the anoxic process splits the nitrate molecules into nitrogen and oxygen. This frees the nitrogen into the air. This application is best served by submersible recirculation pump types ABS XRCP and RCP, the submersible mixed flow column pump type ABS AFLX and the submersible propeller pump type ABS VUPX.

Outlet pumping stations are required when the level of the treatment plant is lower than that of the receiving water. This is especially true when discharging into a river, which can rise during heavy rain or flood periods, or into the sea, where the level varies with the tide. Outlet pumping stations may also be needed to compensate for increasing frictional losses in the outgoing pipe at high flows, for example in long sea outfall pipes.

Outlet pumping stations are required when the level of the treatment plant is lower than that of the receiving water. This is especially true when discharging into a river, which can rise during heavy rain or flood periods, or into the sea, where the level varies with the tide.

The purpose of the selector tank is to control and limit the growth of filamentous bacteria, and then to enhance the sedimentation ability of the sludge. Sulzer provides a number of solutions for creating optimal conditions in the selector.

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.

Sulzer pumps, mixers, grinders and agitators are used to condition, transfer, blend and handle sludge. Our progressing cavity, positive displacement pump range, provide a near constant flow rate with suction lift capability, for handling all types of non-Newtonian sludge and cake processes, typically demanded within the wastewater treatment plant. Maintain in place features ensure any process downtime due to the change out of wear components is kept to a minimum. The Muffin Monster™ grinders protect the equipment downstream. The sludge conditioned by grinders will not clog valves, heat exchangers, digesters, centrifuges and other equipment on the sludge line.

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.