Qunbiao He

Biodegradation of polyacrylamide by anaerobic digestion under mesophilic condition and its performance in actual dewatered sludge system

Polyacrylamide (PAM) used in sludge dewatering widely exists in high-solid anaerobic digestion. Degradation of polyacrylamide accompanied with accumulation of its toxic monomer is important to disposition of biogas residues. The potential of anaerobic digestion activity in microbial utilization of PAM was investigated in this study. The results indicated that the utilization rate of PAM (as nitrogen source) was influenced by accumulation of ammonia, while cumulative removal of amide group was accorded with zeroth order reaction in actual dewatered system. The adjoining amide group can combined into ether group after biodegradation. PAM can be broken down in different position of its carbon chain backbone. In actual sludge system, the hydrolytic PAM was liable to combined tyrosine-rich protein to form colloid complex, and then consumed as carbon source to form monomer when easily degradable organics were exhausted. The accumulation of acrylamide was leveled off ultimately, accompanied with the yield of methane.

Treatment of printing and dyeing wastewater using MBBR followed by membrane separation process

AbstractIn this study, an assessment of the performance of combined moving bed biofilm reactors and a membrane filtration system (MBBRs, anaerobic–aerobic in series and MF) for the treatment of azo dye reactive brilliant red X-3B-containing wastewater was performed. Each reactor was filled with 35 vol.% of the suspended biofilm carriers for biological treatment. To assess the performance of the hybrid processes, the removal efficiencies of color, COD, and SS were analyzed by experiments. The average removal efficiencies of color, COD, and SS were 90, 85 and 94% (influent color = 400 Pt–Co unit, COD = 500 mg/L, and SS = 310 mg/L), respectively when the hydraulic retention times in the anaerobic and aerobic reactors are 11 and 5 h, respectively. The combined MBBRs and membrane system was highly efficient for the treatment of azo dye–containing wastewater. The experimental results showed that the combined processes are a viable technique for textile wastewater treatment.

Change of thermal drying characteristics for dewatered sewage sludge based on anaerobic digestion

The moisture distribution and thermal drying characteristics of dewatered sludge in anaerobic digestion were investigated by a thermo-gravimetric analyzer (TG) and the isothermal kinetic characteristics during the drying were developed by an unreacted core model. The TG results showed that the bound water was partly converted to the free water with the invariant interstitial water and surface water after anaerobic digestion, which enhanced the drying performance of sludge. The time required for the complete drying of digestate was less than that of the raw sludge in the same temperature. The moisture evaporative efficiency of digestate was related to the vapor diffusion rate of the outer surface, and the drying efficiency of digested sludge cannot be enhanced by increased temperatures.

Two-phase high solid anaerobic digestion with dewatered sludge: improved volatile solid degradation and specific methane generation by temperature and pH regulation

The effects of temperature and pH on volatile solid (VS) degradation and CH4 production of anaerobic digestion treating high-solid municipal dewatered sludge was studied. There were two single-phase reactors in Group 1: 35 and 55 °C reactors. In Group 2 (G2), acidification phase temperature was 55 °C or 70 °C and digestion phase temperature was 35 °C or 55 °C. G3 was set on the basis of G2 with the initial pH adjusted to 10.0. VS degradation ratio and CH4 generation ratio of G2 and G3 were higher than G1. In G2, acidification reactors did not show much difference on VS degradation and CH4 generation. Higher VS degradation ratio with higher CH4 generation ratio was get in extreme thermophilic/thermophilic-mesophilic systems. In G3, pH adjustment only promoted VS degradation and CH4 generation in acidification reactors when compared to G2, but the two ratios of the whole systems was not further enhanced.