Ozonation Treatment Of Spent Sulfite Liquor (SSL)

The sulfite pulping industry produces nearly 2.7 million kg of organic waste material annually in the form of lignin and other water soluble organic compounds. For every 1,000 kg of sulfite pulp manufactured, approximately 8,800 liters of desugared spent sulfite liquor (SSL) are produced. This SSL contains the lignin molecule (lignosulfonate) dissolved from wood fibers during the pulping process. It has been estimated that the calorie value of the organic wastes in the SSL produced annually is about 97 trillion cal or the equivalent of 1.1 billion M3 of natural gas/year (38, 137).

CEBTech has past experience with a project involving the conversion of organics and sulfur in SSL, classified as pollutants from sulfite pulp mills, into synthetic methane and protein by means of a combination chemical-biological process. Ozonation was used to break the high molecular weight lignosulfonate molecules present in SSL into lower weight fractions which could be metabolized by methane-producing bacteria and protein-producing yeast. Ozonation experiments showed that this treatment is effective in partially oxidizing and fragmenting lignosulfonates into fermentable substrates. This process is initiated at low ozone concentrations and proceeds rapidly until nearly 30% of the Chemical Oxygen Demand (COD) has been consumed. The conditions under which ozonation is conducted greatly affect the degree of oxidation and the molecular weight of the cleaved fragments (38, 77, 137).


Ozone Generator
with 1.8 Meter
Reaction Column

Two Flasks Showing
Ozone Reactor
Influent & Effluent

Chemical Engineer
Posing with Four
Anaerobic Reactors

Gram Stain of
Methanobacterium
ruminatium

Methanogens in an
Anaerobic Roll Tube
Under Room Light



Methanogens in an
Anaerobic Roll Tube
Under UV Light


Fig. 1 Process Flow
Diagram of Ozonation &
Fermentation of SSL


Process Table 1
of Ozonation &
Fermentation Results


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References