Carbon source recovery from excess sludge by mechanical disintegration for biological denitrification

The goal of the study was to evaluate the possibility of carbon source recovery from excess sludge by mechanical disintegration for biological denitrification. The total efficiency of denitrification, unit demand for organic compounds for denitrification, unit volume of disintegrated sludge and unit cost of nitrogen removal as a function of energy density used for excess sludge disintegration (70, 140 and 210 kJ/L) were analyzed. In the study a full-scale disc disintegrator was used (motor power: 30 kWh, motor speed: 2,950 rpm). It was shown that the amounts of organic compounds released from the activated sludge flocs at all tested levels of energy density are high enough to be used to intensify the removal of nitrogen compounds from wastewater. It was also documented that the energy density provided during process of disintegration was an important factor determining the characteristics of organic compounds obtained under the disintegration for their use in order to intensify the process of denitrification. The highest value of total efficiency of denitrification (50.5 ± 3.1 mg N/L) was obtained for carbon source recovery from excess sludge at 70 kJ/L, but the lowest unit cost of nitrogen removal occurred for 140 kJ/L (0.0019 ± 0.0011 EUR/g N).