Effect of alkaline addition on anaerobic sludge digestion with combined pretreatment of alkaline and high pressure homogenization

• Combined pretreatment of alkaline and HPH significantly enhanced sludge digestion.
• Alkaline addition greatly improved organic matter degradation.
• Alkaline addition obviously promoted biogas production.
• Sludge disintegration degree was a key factor to improve anaerobic digestion.

To improve anaerobic digestion efficiency, combination pretreatment of alkaline and high pressure homogenization was applied to pretreat sewage sludge. Effect of alkaline dosage on anaerobic sludge digestion was investigated in detail. SCOD of sludge supernatant significantly increased with the alkaline dosage increase after the combined pretreatment because of sludge disintegration. Organics were significantly degraded after the anaerobic digestion, and the maximal SCOD, TCOD and VS removal was 73.5%, 61.3% and 43.5%, respectively. Cumulative biogas production, methane content in biogas and biogas production rate obviously increased with the alkaline dosage increase. Considering both the biogas production and alkaline dosage, the optimal alkaline dosage was selected as 0.04 mol/L. Relationships between biogas production and sludge disintegration showed that the accumulative biogas was mainly enhanced by the sludge disintegration. The methane yield linearly increased with the DDCOD increase as Methane yield (ml/gVS) = 4.66 DDCOD − 9.69.