Psychrophilic Anaerobic Treatment Research Articles

Psychrophilic and mesophilic anaerobic treatment of synthetic dairy wastewater with long chain fatty acids: Process performances and microbial community dynamics

Facilitating the anaerobic degradation of long chain fatty acids (LCFA) is the key to unlock the energy potential of lipids-rich wastewater. In this study, the feasibility of psychrophilic anaerobic treatment of LCFA-containing dairy wastewater was assessed and compared to mesophilic anaerobic treatment. The results showed that psychrophilic treatment at 15 ℃ was feasible for LCFA-containing dairy wastewater, with high removal rates of soluble COD (>90%) and LCFA (∼100%). However, efficient long-term treatment required prior acclimation of the biomass to psychrophilic temperatures. The microbial community analysis revealed that putative syntrophic fatty acid bacteria and Methanocorpusculum played a crucial role in LCFA degradation during both mesophilic and psychrophilic treatments. Additionally, a fungal-bacterial biofilm was found to be important during the psychrophilic treatment. Overall, these findings demonstrate the potential of psychrophilic anaerobic treatment for industrial wastewaters and highlight the importance of understanding the microbial communities involved in the process.

Psychrophilic anaerobic treatment of sewage: Biomethane potential, kinetics and importance of inoculum selection

Anaerobic sewage treatment has been proposed as sustainable sanitation technology with the potential to be energy positive. However, there are very few works dealing with anaerobic degradability (i.e. biomethane potential – BMP) of sewage. Until now, no authors systematically studied anaerobic psychrophilic degradation of sewage in sufficient detail, i.e. in batch experiments. In this study, six sewage samples of various origin and quality were tested via BMP experiments with three different samples of inoculum (both adapted and non-adapted), to elucidate the principle kinetics and obtain fundamental engineering data.The anaerobic biodegradability of sewage at 15 °C varied from 50 to 75%, with the average methane yield 0.22 ± 0.03 m3 kg−1 (CH4, CODadded). According to Monod-based calculations, all sewage samples behaved as two component substrate, while no correlation of biodegradability with different raw sewage quality was observed. The same rate constant (rmax) was found for all tested sewage samples. But, rmax was greatly dependent on inoculum source.This study provides a fundamental dataset to understand and predict psychrophilic anaerobic sewage utilization. With this knowledge, novel wastewater treatment plant layouts can be designed even in mild/cold climates as well as already existing facilities intensified in terms of energy optimization and recovery.

Reactor performance and microbial community of an EGSB reactor operated at 20 and 15°C

To investigate the effects of low temperatures on the performance and microbial community of anaerobic wastewater treatment. An expanded granular sludge bed (EGSB) reactor was employed to treat synthetic brewery wastewater at 20 and 15 degrees C. Reactor performance was represented by chemical oxygen demand (COD) removal efficiency, while the microbial community was analysed using denaturing gradient gel electrophoresis (DGGE) and clone technology. When the hydraulic retention time (HRT) was maintained at 18 h, COD removal efficiencies above 85% were obtained at both 20 and 15 degrees C, with influent COD concentrations up to 7300 and 4100 mg l(-1), respectively. At 15 degrees C, the COD removal efficiency was more easily manipulated by increasing the influent COD concentration. DGGE and clone results for both temperatures revealed that Methanosaeta and Methanobacterium were two dominant methanogens, and that the majority of the eubacterial clones were represented by Firmicutes. When the temperature decreased from 20 to 15 degrees C, both archaeal and eubacterial communities had higher diversity, and the proportion of Methanosaeta (acetate-utilizing methanogens) decreased markedly from 60.0% to 49.3%, together with an increase in proportions of hydrogen-utilizing methanogens (especially Methanospirillum). The feasibility of psychrophilic anaerobic treatment of low and medium strength organic wastewaters was demonstrated, although lower temperature could significantly affect both reactor performance and the anaerobic microbial community. The findings enrich the theory involving the microbial community and the application of anaerobic treatment in a psychrophilic environment.

Ultrasonication as a Pre-Treatment Method for the Enhancement of the Psychrophilic Anaerobic Digestion of Aquaculture Effluents

The effectiveness of ultrasonication as a pre-treatment method for the psychrophilic anaerobic treatment of aquaculture effluents was assessed using a 4 l solids digester. Ultrasonication of aquaculture wastewater was found to enhance the removal of chemical oxygen demand by anaerobic digestion by almost 10%. There was also a concurrent increase in total biogas production from 0.29 l day-1 to 0.45 l day-1 with a corresponding 10% increase in methane concentration. Furthermore, there was an increase of 60% in effluent total ammonia nitrogen concentration as a result of sonication in comparison with a 45% increase for untreated digester waste.

Psychrophilic anaerobic treatment of low strength wastewaters

Psychrophilic (2 to 20°C) anaerobic treatment of low strength synthetic and malting wastewater was investigated using a single and two module expanded granular sludge bed (EGSB) reactor system. The chemical oxygen demand (COD) removal efficiencies found in the experiments exceeded 90 % in the single module reactor at an organic loading rate up to 12 g COD dm−3 day−1 and a HRT of 1.6 h at 10-12°C ambient temperature using influent concentrations ranging from 500 to 800 mg COD dm−3. When a two module EGSB system was used at the temperature range 10-15°C, soluble COD removal and volatile fatty acids removal of 67-78% and 90-96% were achieved, respectively, and an OLR between 2.8-12.3 kg COD m−3 day−1 and a HRT of 3.5 h. The second module serves mainly as a scavenger of non-degraded volatile fatty acids (VFA) from the first module. The optimal temperatures for substrate conversion of reactor sludge, after it has been exposed to long term psychrophilic conditions, were similar to those of the original mesophilic inoculum. The specific activities of the sludge in the reactor increased in time by a factor 3, indicating enrichment of methanogens and acetogens even at low temperatures. By adapting the process design to the expected prevailing conditions inside the reactor, the loading potentials and overall stability of the anaerobic high-rate process may be distinctly improved under psychrophilic conditions. The results obtained clearly reveal the big potentials of anaerobic wastewater treatment under low ambient (10-12°C) temperature conditions for low strength wastewaters, very likely including domestic sewage.

Psychrophilic anaerobic treatment of low strength wastewaters

Psychrophilic (2 to 20°C) anaerobic treatment of low strength synthetic and malting wastewater was investigated using a single and hvo module expanded granular sludge bed (EGSB) reactor system. The chemical oxygen demand (COD) removal efftciencies found in the experiments exceeded 90% in the single module reactor at an organic loading rate up to 12 g COD dm −3’ day −1 and a HRT of 1.6 h at 10–12°C ambient temperature using influent concentrations ranging from 500 to 800 mg COD dm −3 When a two module EGSB system was used at the temperature range l0–15°C, soluble COD removal and volatile fatty acids removal of 67–78% and 90–96% were achieved, respectively, and an OLR between 2.8–12.3 kg COD m -3 day −1 and a HRT of 3.5 h. The second module serves mainly as a scavenger of non-degraded volatile fatty acids (VFA) horn the fust module. The optimal temperatures for substrate conversion of reactor sludge, after it has heen exposed to long term psychrophilic conditions, were similar to those of the original mesophilic inoculum. The specific activities of the sludge in the reactor increased in time by a factor 3, indicating enrichment of methanogens and acetogens even at low temperatures. By adapting the process design to the expected prevailing conditions inside the reactor, the loading potentials and overall stability of the anaerobic high-rate process may be distinctly improved under psychrophilic conditious. The results obtained clearly reveal the big potentials of anaerobic wastewater treatment under low ambient (l0–12°C) temperature conditions for low strength wastewaters, very likely including domestic sewage.

Attached-film media performance in psychrophilic anaerobic treatment of dairy cattle wastewater

Retention of microorganisms in anaerobic digesters by providing an attachment medium can potentially increase their productivity at lower operating temperatures. The objective of this work was to investigate the effectiveness of attached-film bioreactors for psychrophilic anaerobic digestion of dairy manure. Eight digesters were maintained in an environmental chamber, with the temperature varied between 37 and 10°C. Two digesters were packed with limestone gravel, two with pieces cut from non-woven polyester matting, two with a combination of limestone gravel and polyester pieces, and two had no packing. Digester operation was initiated at a temperature of 37°C. After the digesters reached stable operation at the initial temperature, the temperature was lowered slowly to 10°C. The temperature was held at 10°C for 5 weeks after stabilizing. The polyester medium with its high porosity and surface to volume ratio had the best overall performance for methane productivity at both 37 and 10°C. The biogas production (ml/d) and methane production (ml/d) were significantly higher for the polyester medium when compared to the limestone and combination media reactors ( p < 0.0001 and 0.0002, respectively). At 10°C, the polyester medium reactors performed significantly better than all others for biogas (ml/d) and methane (ml/d) production ( p < 0.0001). The polyester medium also yielded the maximum reductions in volatile solids (VS) and chemical oxygen demand (COD) at 37°C.