The addition of Polytetsu can suppress the generation of hydrogen sulfide and prevent corrosion caused by sulfides. It can also inhibit the growth of filamentous bacteria and prevent sludge bulking. In addition, during sludge treatment, it can improve sludge dewatering efficiency and provide various other benefits.

Effects of Addition at Pumping Stations

Effects of Polytetsu

Taking the addition of Polytetsu at a sewage pumping station as an example. This pumping station is located at the front end of the wastewater treatment plant. The Polytetsu added at the pumping station mixes with the wastewater and flows together into the treatment plant. 
The effect of adding Polytesu at the pumping station, extending all the way to sludge dewatering at the treatment plant is astonishing. Let us refer to the following diagram for illustration.

Inhibition of Hydrogen Sulfide

In the rectangular wastewater channels, the cross section is about 3–4 meters wide and high. During continuous sunny days, the sewage flowing into the pumping station tends to become anaerobic, making hydrogen sulfide easy to form. To prevent the formation of hydrogen sulfide, Polytetsu is added. The hydrogen sulfide generated in the channel reacts with the Polytetsu reagent to form iron sulfide. This reaction continues along the sewage pipeline, protecting both the pumping station and pipelines from corrosion.

Effects on Water Treatment Processes

Inhibition of Filamentous Bacteria Growth

• Filamentous bacteria, which cause sludge bulking, often multiply using sulfides as nutrients. Hydrogen sulfide in wastewater promotes the proliferation of filamentous bacteria.
• In wastewater treated with Polytetsu, hydrogen sulfide is converted into iron sulfide. When entering the wastewater treatment plant, most of the iron sulfide settles into the sludge in the primary sedimentation tank. However, some fine particles (less than 1.5 μm) flow with the wastewater into the aeration tank.
• The iron sulfide in the aeration tank undergoes oxidation reactions to produce ferric hydroxide and sulfur. Sulfur-oxidizing bacteria then react with sulfur to produce sulfate ions. The sulfate ions, being insoluble, are discharged with the clarified liquid. The remaining ferric hydroxide ions attach to activated sludge, improving flocculation and sedimentation.
• The addition of Polytetsu greatly reduces the sulfide content entering the aeration tank, decreasing filamentous bacteria survival. Moreover, the iron component in Polytetsu enhances sludge coagulation and sedimentation, preventing sludge bulking from two aspects.

Effects on Sludge Treatment

Promoting Sludge Settling and Reducing Moisture Content

The Polytetsu added at the pumping station accumulates effectively in the subsequent sludge. It promotes sludge settling and improves sludge thickening efficiency, thereby reducing the water content of the residual sludge. After adding Polytetsu at the pumping station, the residual sludge water content at the wastewater plant was 80%. This shows that the effects of adding Polytetsu at the pumping station extend all the way to the sludge dewatering stage.

Prevention of Pipe Scaling (MAP)

The cause of MAP scaling is the formation of magnesium ammonium phosphate in the pipelines. Because of the iron component in Polytetsu, the phosphate in sludge reacts to form ferric phosphate, preventing MAP formation. For already formed MAP, Polytetsu also has a dissolving effect.

Inhibition of Hydrogen Sulfide in Digesters

The effect of adding Polytetsu at the pumping station continues to the digestion tanks of the wastewater plant. Data show that before adding Polytetsu, hydrogen sulfide concentrations in digester gas reached 5000–8000 ppm. After adding Polytetsu, the hydrogen sulfide concentration in the digester dropped to 80–500 ppm. This significantly reduced the desulfurization cost of the digester gas.

Conclusion

In summary, the effects of adding Polytetsu at the pumping station persists throughout subsequent wastewater and sludge treatment process up to the digestion tank. The dosage of Polytetsu at the pumping station is usually 2–3 times higher than when added only during the sludge dewatering stage. However, its diverse effects include preventing corrosion of wastewater facilities (concrete structures), improving odor throughout the process, inhibiting sludge bulking, preventing MAP formation, and reducing hydrogen sulfide in digester gas. This results in lower desulfurization costs and a higher overall cost-effectiveness, making it highly recommended.