J Korean Soc Environ Eng. 2015; 37(10): 583-589.
Published online 2015 October 31.
Anaerobic Treatment of Leachate Solubilized from Thermal Hydrolysis of Sludge Cake
1Department of Environmental Engineering, Chungnam National University
2Environmental Research Institute, Hanwha E&C, Korea
Received 2015 October 05; Accepted 2015 October 29.
ABSTRACT
This study was performed to evaluate the feasibility of anaerobic pretreatment for the leachate solubilized from thermal hydrolysis of sewage sludge cake. Overall process for the treatment of sludge cake consists of thermal hydrolysis, crystallization of magnesium, ammonium, and phosphate (MAP) for the leachate and anaerobic digestion of supernatant from MAP crystallization. The experimental evidence showed that the optimum ratio of Mg : P for the struvite crystallization of leachate solubilized from thermal hydrolysis of sludge cake was 1.5 to 1.0 as weight basis at the pH of 9.5. With this operational condition, the removal efficiencies of ammonia nitrogen and phosphorous achieved 50% and 97%, respectively. The mesophilic batch test showed that the ultimate biodegradability of the supernatant from MAP crystallization reached 63% at S/I ratio of 0.5. The readily biodegradable fraction of 90% (S1) of the MAP supernatant BVS (Biodegradable Volatile Solids, S0) degraded with k1 of 0.207 day-1 for the initial 17 days where as the rest slowly biodegradable fraction (S2) of 10% of BVS degraded with k2 of 0.02 day-1 for the rest of the operational period. Semi-Continuously Fed and Mixed Reactor (SCFMR) was chosen as one of the best candidates to treat the MAP supernatant because of its total solids content over 6%. Maximum average biogas production rates reached 0.45 v/v-d and TVS removal efficiency of 37~41% was achieved at an hydraulic retention time (HRT) of 20 days and its corresponding organic loading rate (OLR) of 1.43 g VS/L-d.
Keywords :
Thermal Hydrolysis, Sewage Sludge Cake, Ultimate Biodegradability, MAP Crystallization, Anaerobic Digestion
