Hongzhi Ma

Isolation, identification of sludge-lysing strain and its utilization in thermophilic aerobic digestion for waste activated sludge

A strain of sludge-lysing bacteria was isolated from waste activated sludge (WAS) in this study. The result of 16S rRNA gene analysis demonstrated that it was a species of new genus Brevibacillus (named Brevibacillus sp. KH3). The strain could release the protease with molecule weight of about 40 kDa which could enhance the efficiency of sludge thermophilic aerobic digestion. During the sterilized sludge digestion experiment inoculated with Brevibacillus sp. KH3, the maximum protease activity was 0.41 U/ml at pH 8 and 50 degrees C, and maximum TSS removal ratio achieved 32.8% after 120 h digestion at pH 8 and 50 degrees C. In the case of un-sterilized sludge digestion inoculated with Brevibacillus sp. KH3, TSS removal ratio in inoculated-group was 54.8%, increasing at 11.86% compared with un-inoculation (46.2%). The result demonstrated that inoculation of Brevibacillus sp. KH3 could help to degrade the EPS and promote the collapse of cells and inhibit the growth of certain kinds of microorganisms. It indicated that Brevibacillus sp. KH3 strain had a high potential to enhance WAS-degradation efficiency in thermophilic aerobic digestion.

Stillage reflux in food waste ethanol fermentation and its by-product accumulation

Raw materials and pollution control are key issues for the ethanol fermentation industry. To address these concerns, food waste was selected as fermentation substrate, and stillage reflux was carried out in this study. Reflux was used seven times during fermentation. Corresponding ethanol and reducing sugar were detected. Accumulation of by-products, such as organic acid, sodium chloride, and glycerol, was investigated. Lactic acid was observed to accumulate up to 120g/L, and sodium chloride reached 0.14mol/L. Other by-products did not accumulate. The first five cycles of reflux increased ethanol concentration, which prolonged fermentation time. Further increases in reflux time negatively influenced ethanol fermentation. Single-factor analysis with lactic acid and sodium chloride demonstrated that both factors affected ethanol fermentation, but lactic acid induced more effects.

Phosphate removal from wastewater using aluminium oxide as adsorbent

The development and manufacture of an adsorbent to remove phosphate for the prevention of eutrophication in lakes is very important. The use of aluminium oxide (alumina) as an organic adsorbent to remove phosphate from wastewater has been investigated. The characteristics of this absorption process were investigated to determine the important parameters, such as the pH and the aluminium ion concentration. Moreover, chemical treatment methods to enhance the adsorption capacity of alumina were tested. Dynamic studies and equilibrium adsorption isotherm studies were conducted to determine the adsorption capacity and efficiency. The experimental results indicate that it is necessary to increase the temperature above 500°C in order to obtain a high-capacity adsorbent, and alumina treated with acid or calcium or magnesium has a larger adsorption capacity for phosphate than untreated adsorbent. Moreover, the adsorption of phosphate was enhanced at a lower pH and a higher aluminium ion concentration, and a simple Freundlich isotherm could express the equilibrium adsorption isotherm, and the intragranular diffusion controlling model was used to test the dynamic studies. These findings have important implications for the application and development of aluminium oxide as a prospective adsorbent.

Alleviation of harmful effect in stillage reflux in food waste ethanol fermentation based on metabolic and side-product accumulation regulation

Stillage reflux fermentation in food waste ethanol fermentation could reduce sewage discharge but exert a harmful effect because of side-product accumulation. In this study, regulation methods based on metabolic regulation and side-product alleviation were conducted. Result demonstrated that controlling the proper oxidation-reduction potential value (-150mV to -250mV) could reduce the harmful effect, improve ethanol yield by 21%, and reduce fermentation time by 20%. The methods of adding calcium carbonate to adjust the accumulated lactic acid showed that ethanol yield increased by 17.3%, and fermentation time decreased by 20%. The accumulated glyceal also shows that these two methods can reduce the harmful effect. Fermentation time lasted for seven times without effect, and metabolic regulation had a better effect than side-product regulation.

Research on the Recycling of Distillation Waste in Ethanol Fermentation from Food Waste and Its Influence

Ethanol fermentation from food waste could reduce the solid waste pollution and realize energy utilization. In order to decrease distillation waste, the recycle of such waste was adopted in ethanol fermentation. It demonstrated that such treatment could only last for four times due to the existence of side products. The distillation waste would gradually reduce ethanol concentration and sugar utilization ratio, lactic acid would be accumulated to 8 g/L, and salinity would be accumulated to 10 g/L, pH decreased to less than 3.5. Three-dimensional fluorescence analysis showed protein-type substances, microbial metabolism type substances, and humic substances were accumulated during the recycling. In order to resolve such problems, addition of protease was chosen in this research. The recycling time could enhance to seven times and the highest ethanol concentration was 35 g/L, the lowest ethanol concentration was 20 g/L. The recycling of distillation waste could save water resource, reduce wastewater discharges with high COD lees and reduce the cost. Which provided a new way for the clean production of bioethanol production from food waste.

RESEARCH ON THE ADOPTION OF LACTIC ACID BACTERIA IN FOOD WASTE STORAGE AND ETHANOL PRODUCTION

The preservation and de-odorization of food waste are very important for its utilization in fuel ethanol production as raw materials. In this paper, the inoculation of lactic acid bacteria (LAB) was carried out for food waste storage and its further fermentation for ethanol. Four contamination prevention methods, anaerobic storage, autoclaving, acid usage, the inoculation of LAB, were compared in this study. The optimum conditions for inoculation of LAB into food waste as well as the fermentation characteristic were studied. The optimum inoculum size and storage time of LAB for food waste were 0.5% (V/V) and 2 days, respectively. The quantities of microorganisms such as Escherichia coliform (E. coli) and Methicillin Resistant Staphylococcus aureu (MRSA) could not be detected in the final phase of fermentation. It proved that the inoculation of LAB in food waste could prevent the growth of putrefying bacteria. The low pH or metabolic product by lactic acid (LA) fermentation was the reason for contamination prevention.

Research on Biodiesel and Ethanol Production from Food Waste

In order to solve the pollution caused by food waste, research was carried out to test the feasibility of biodiesel and ethanol production from food waste. With separation process, waste oil and rudimental solid component of food waste were obtained. Chemical synthesis was utilized for biodiesel production with oil and fermentation was chosen for ethanol production from solid parts. The result demonstrated that biodiesel produced from waste oil were mixed fatty acid methyl esters with the main components of Octadecenoic acid methyl ester, Octadecadienoic acid methyl ester and Hexadecanoic acid methyl ester. Since they were similar to the composition to those produced with other traditional raw biodiesel materials, it demonstrated that this was a possible way to utilize waste oil. Furthermore, the solid part of food waste could produce 44 g/L ethanol under 35°C for 3 days with yeast cultured. Ethanol and biodiesel production from food waste could to a large extent save the production cost as well as solve the pollution problem.

Stimulation of methane yield rate from food waste by aerobic pre-treatment

Aerobic pre-treatment (AP) was applied to enhance methane yield from food waste through anaerobic digestion. Different AP durations (i.e. 2, 5 and 8 days) prior to anaerobic digestion were tested. The results indicated that AP of food waste led to no significant differences (p > 0.05) in methane yield potential (ca. 418 mL/g-VS). However, a suitable AP duration (5 days) increased methane yield rates (ca. 18 mL/d/g-VS; 22.0% higher than the control) by anticipating methane generation and shortening the methanogenic phase via volatile fatty acid reduction and pH increase. Although AP induced chemical oxygen demand loss to some extent (i.e. by 2.6%-9.9%) in the AP stage via aerobic degradation, the methane yield potential could be recovered by enhancing organic matter hydrolysis. Therefore, maximisation of hydrolysis should be used as a basis for determining a suitable AP duration for various types of organic matter.

Effect of fermentation stillage of food waste on bioelectricity production and microbial community structure in microbial fuel cells

A single-chamber microbial fuel cell (MFC) was used in this study to treat recycled stillage obtained from food waste ethanol fermentation. Corresponding substrates inside the system were evaluated by fluorescence spectra, and microbial communities were also investigated. Results demonstrated that output voltage and current, respectively, reached 0.29 V and 1.4 mA with an external resistance of 200 Ω. Corresponding total organic carbon and chemical oxygen demand removal efficiency reached more than 50% and 70%, respectively. Results of fluorescence spectra demonstrated that tryptophan-like aromatic, soluble microbial by-product-like and humic acid-like substances accumulated and were not easily degraded. Microbial community analysis by high-throughput sequence indicated that Advenella and Moheibacter occupied the highest proportion among all genera at the anode instead of Geobacter. These results may be due to complicated accumulated stillage, and potential tetracyclines possibly influenced microbial communities. Details on how stillage affects MFC operation should be further studied, and a solution on relieving effects should be established.

Concise review on ethanol production from food waste: development and sustainability

The development of sustainable bioethanol fuel production from food waste has increasingly become an attractive topic. Food waste is recognized as the most available and costless feedstock. Therefore, ethanol production has been adopted as cost-efficient and an ecological way for FW disposal. This paper reviewed the microorganisms utilized for ethanol fermentation, the effect of enzymatic hydrolysis on ethanol concentration, optimization of accurate process parameters, and recycling of huge volumes of stillage for ethanol production towards reducing any incurred environmental burdens and minimizing the cost. The statistical tools which may enhance the process efficiency had been presented. Also, the perspective and the future development were introduced. All these aimed to fully utilize the food waste and also reduce the cost for side-product in this process; proper operation conditions and the control methods for stillage recycling were considered as the methods to improve ethanol fermentation from food waste.