Effect of polymeric substrate on sludge settleability

Area of Science:

• Environmental Microbiology
• Wastewater Treatment Engineering

Background:

• Bulking sludge is a major challenge in wastewater treatment, often linked to substrate utilization.
• The role of polymeric substrates, like starch, in sludge bulking has been understudied.
• Kinetic selection theory suggests low substrate concentrations cause bulking, while a newer theory emphasizes diffusion-limited gradients.

Purpose of the Study:

• To investigate the effect of a polymeric substrate (starch) on sludge settleability.
• To compare the bulking sludge potential of starch versus monomers (glucose).
• To evaluate the validity of diffusion gradient theory in explaining sludge bulking.

Main Methods:

• Experimental comparison of sludge settleability using starch and glucose as substrates.
• Induction and remediation of bulking sludge events.
• Microscopic observation of sludge floc structure.

Main Results:

• Conditions causing bulking sludge with glucose did not induce bulking with starch.
• Substituting glucose with starch successfully cured an existing bulking sludge event.
• Starch-fed flocs were more porous and open than those fed with maltose or glucose.

Conclusions:

• Results support the diffusion gradient theory for bulking sludge.
• Polymeric substrates like starch may mitigate bulking by reducing substrate gradients within flocs.
• Sludge floc structure is influenced by the type of substrate, with implications for settling properties.