Thiotrix

Thiothrix is capable of using reduced sulphur compounds (e.g. hydrogen sulphide) as an energy source and depositing intermediary elemental sulphur under oxygen-depleted conditions. The stored sulphur can be clearly identified in living samples as pale, strongly refractive points. This filament can occur with high sludge loads and in industrial wastewater treatment plants, and causes bulking sludge.

 

Morphology:

Filament position: projecting out of flake
Branching: none
Movement: none
Growth habit: straight / slightly curved
Aufwuchs: absent
Constrictions: none
Sheath: present, but not in all strains
Transverse walls: visible, the S-granule is often hard to identify
Cell form: square to rectangular
Length of filaments: 50 – 500 µm
Filament diameter: 0.8 – 2.5 µm
Gram staining: mostly negative
Neisser staining: negative

 

Factors promoting growth:

  • decaying sewage
  • insufficient oxygen supply
  • high C/N/P ratio, lack of phosphorus and nitrogen deficiency
  • sludge load > 0.1 – 0.6 kg BSB5/ kg TS * d

Countermeasures:

  • improve the oxygen supply
  • pre-ventilation of sewage
  • dosage with precipitants with high share of bivalent iron (FERRACLAR CLASSIC) before biology