Ajay Kumar Jha

Research advances in dry anaerobic digestion process of solid organic wastes

The dry anaerobic digestion process is an innovative waste-recycling method to treat high-solidcontent bio-wastes. This can be done without dilution with water by microbial consortia in an oxygenfree environment to recover potential renewable energy and nutrient-rich fertilizer for sustainable solid waste management. It generally takes place at solid concentrations higher than 10% and enables a higher volumetric organic loading rate, minimal material handling, lower energy requirements for heating, limited environmental consequences and energetically effective performance. The long retention time, poor startup performance, incomplete mixing and the accumulation of volatile fatty acids (VFAs) are considered as the main disadvantages for the solid-state fermentation process. In order to develop feasible dry anaerobic digestion processes, it is important to review the optimization techniques and suggest possible areas where improvements could be made. These include reactor configuration, mixing, solid retention time, feedstocks, organic loading rate, inoculation, co-digestion, pretreatment, percolation, additives and environmental conditions within the digester such as temperature, pH, buffering capacity and VFAs concentration.

Recent Developments and Future Perspectives of Anaerobic Baffled Bioreactor for Wastewater Treatment and Energy Recovery

Anaerobic baffled reactor (ABR) processes play an increasingly important role in wastewater treatment and resource recycling by its ingenious construction and excellent performance. The authors aim to introduce new research progresses and applications of ABR in the last two decades, focusing mainly on the following aspects: presenting and comparing its development and application instances, discussing the optimization of operating regulation and mathematical models, stating existing problems in current researches, suggesting possible improvements, and proposing future research perspectives. The contributions of this review involve enhancing ABR treatment efficiency and operation stability to provide information for colleagues.

Optimization of Dry Anaerobic Fermentation of Solid Organic Wastes

Dry methane fermentation is an innovative anaerobic digestion technique to treat solid bio-wastes without dilution for potential energy recovery with nutrient rich fertilizer and sustainable waste management. Although dry anaerobic fermentation offers great advantages like utilization of wastes in its produced form, high organic loading rate, no liquid effluent and comparable amount of biogas production with wet fermentation, commercial dry anaerobic digestion is scarcely used so far. In order to develop feasible dry fermentation process, it is important to review the optimization techniques and suggested possible areas where improvements could be made, including the reactor configuration, mixing, feed stocks, co-digestion, pretreatment and environmental conditions within the digester.

Effect of pH and buffer on butyric acid production and microbial community characteristics in bioconversion of rice straw with undefined mixed culture

This study was conducted to identify the optimum pH range and the appropriate buffer for butyric acid production from rice straw by fermentation using an undefined mixed culture. A series of experiments conducted at pH levels of 5.0 ~ 7.0 showed that neutral pH improved rice straw conversion and consequently carboxylic acid production. The highest butyric acid production (up to 6.7 g/L) was achieved at pH of 6.0 ~ 6.5, while it was only 1.7 g/L without pH control or at pH 5.0. Another series of experiments conducted at pH 6.0 ~ 6.5 buffered with CaCO3, NaHCO3, NH4HCO3 and their combinations indicated that different buffers had different effects onthe product spectrum, and that CaCO3 combined with NaHCO3 was an effective buffer for butyric acid production. The highest total volatile fatty acids (about 12.6 g/L) production and one of the two highest butyric acid concentrations (about 7.6 g/L) were obtained by buffering with CaCO3 combined with NaHCO3. PCR-DGGE analysis revealed that different pH and buffers also influenced the microbial population distribution. Bacteria were suppressed at low pH, while the bacterial community structures at higher pH varied slightly. Overall, this study presents an alternative method for butyric acid production from lignocellulosic biomass without supplementary cellulolytic enzyme.

Review of bio-hydrogen production and new application in the pollution control via microbial electrolysis cell

AbstractBreaking through the “fermentation barrier” bottleneck of conventional biological hydrogen production technology, achieving the depth use of carbon source, and obtaining the higher hydrogen production, bioelectrocatalysis technology assisted fermentation process has vast prospective of applications. The main technical route is the microbial electrolysis cell (MEC). Based on the cutting-edge researches carried out by worldwide scholars, this paper focuses on the comprehensive discussion of MEC design, substrate selection, electrode materials, performance optimization, microbiology, as well as the main problems of the corresponding research. The review also presents recommendations and solutions accordingly. Finally, the prospects of microbial electrocatalysis assisted technology in the field of environmental pollution control and energy recovery application have been disclosed.

Response of Syntrophic Propionate Degradation to pH Decrease and Microbial Community Shifts in an UASB Reactor.

The effect of pH on propionate degradation in an upflow anaerobic sludge blanket (UASB) reactor containing propionate as a sole carbon source was studied. Under influent propionate of 2,000 mg/l and 35ºC, propionate removal at pH 7.5-6.8 was above 93.6%. Propionate conversion was significantly inhibited with stepwise pH decrease from pH 6.8 to 6.5, 6.0, 5.5, 5.0, 4.5, and then to 4.0. After long-term operation, the propionate removal at pH 6.5-4.5 maintained an efficiency of 88.5%-70.1%, whereas propionate was hardly decomposed at pH 4.0. Microbial composition analysis showed that propionate-oxidizing bacteria from the genera Pelotomaculum and Smithella likely existed in this system. They were significantly reduced at pH ≤5.5. The methanogens in this UASB reactor belonged to four genera: Methanobacterium, Methanospirillum, Methanofollis, and Methanosaeta. Most detectable hydrogenotrophic methanogens were able to grow at low pH conditions (pH 6.0-4.0), but the acetotrophic methanogens were reduced as pH decreased. These results indicated that propionate-oxidizing bacteria and acetotrophic methanogens were more sensitive to low pH (5.5-4.0) than hydrogenotrophic methanogens.

Survey of Combined Hydrogen-Methane Production in Anaerobic Baffled Reactor (ABR)

Anaerobic fermentative technology is an important route to solving environmental pollution and resources problems. Combined hydrogen and methane production in a two-stage process is a concept which has been developed in recent years Anaerobic biological treatment organic wastewater can produce large amounts of hydrogen and methane，which can be used as energy carrier. At present，the research focusing on the adjustment of fermentation hydrogen-methane production has been conducted. Furthermore, the simultaneous hydrogen-methane production was tested and optimized. However, it lacked combined hydrogen-methane production in an anaerobic reactor in literature so far. Based on preview experiment, the paper studied the simultaneous hydrogen-methane fermentation in an anaerobic baffled reactor (ABR) system. ABR has the advantage of biomass phase separation and integration of acidogenic and methanogenic processes to simultaneously conduct hydrogen-methane production during wastewater treatment. Through deep biohydrogen production, it can enhance the activity of hydrogen-producing acetogens (HPA) and the efficiencies of the combined hydrogen-methane fermentation system. It showed to enhance the activity of HPA was the key to the combined hydrogen-methane production.

Study on Advanced Management of Water Resource

This work introduced water resource management of some developed countries such as the USA, Australia, Japan, Germany, France, etc. The countries developed individual water resources management models based on their own conditions. In America, a coordinative mode between region and river basin was formed. The Japanese muti-flood control mode which clarified the responsibilities of the administration and local government enhanced the management. Singapore owns a unique management mode, which effectively guaranteed the implementation of water resource management. This work offers references to the formation of water resource management modes suitable for different countries.

Research on the Watershed Ecological Risk Management

The risk management of watershed ecology is an important topic in the field of water resources management. To improve the present situation of the water ecological risk management in Songhua River and Liao River watershed, based on the policy of eco-management of the important water function zone in China, and the potential risk source investigation of watershed, investigate hazard components, predict risk probability and the possible negative effects, put forward the mitigation measure on water ecological response in watershed. It is necessary to explore water ecotoxicological variation, resolve biodiversity watershed, establish a suitable ecological evaluation index system, and put forward the multi-objective of optimizing management strategies.

The Advancement of Algal Biomass: A Review

Renewable energy sources such as biomass are becoming more and more important as alternative to fossil fuels. One of the most exciting new sources of biomass is microalgae. One of the major obstacles in the commercial production of microalgae as feedstock for biomass-to-liquid fuels, is the development of energy efficient and cost effective harvesting methods for the separation of micro-algal biomass from its growth medium. The problem of water shortage and lack of energy have become key restricting factors for the economic development of the world. Biomass energy due to its renewability, low pollution and other advantages is considered as the most potential products to alleviate the water pollution and energy crisis. Algae, the third generation of biomass, have many advantages such as wide distribution, high oil content, strong environment adaptability, short growth cycle and low production cost. Thus the use of algae biomass has attracted more and more attention. This paper describes the progress of the algae biomass energy research, the key issues and trends in the industrial process.