► Korean food waste was found to contain low level of trace elements. ► Stable anaerobic digestion of food waste was achieved by adding trace elements. ► Iron played an important role in anaerobic ...digestion of food waste. ► Cobalt addition further enhanced the process performance in the presence of iron.
The purpose of this study was to examine if long-term anaerobic digestion of food waste in a semi-continuous single-stage reactor could be stabilized by supplementing trace elements. Contrary to the failure of anaerobic digestion of food waste alone, stable anaerobic digestion of food waste was achieved for 368days by supplementing trace elements. Under the conditions of OLR (organic loading rates) of 2.19–6.64g VS (volatile solid)/Lday and 20–30days of HRT (hydraulic retention time), a high methane yield (352–450mLCH4/gVSadded) was obtained, and no significant accumulation of volatile fatty acids was observed. The subsequent investigation on effects of individual trace elements (Co, Fe, Mo and Ni) showed that iron was essential for maintaining stable methane production. These results proved that the food waste used in this study was deficient in trace elements.
The objective of this study was to evaluate the feasibility of anaerobic co-digestion of food waste and piggery wastewater, and to identify the key factors governing the co-digestion performance. The ...analytical results indicated that the food waste contained higher energy potential and lower concentrations of trace elements than the piggery wastewater. Anaerobic co-digestion showed a significantly improved biogas productivity and process stability. The results of co-digestion of the food waste with the different fractions of the piggery wastewater suggested that trace element might be the reason for enhancing the co-digestion performance. By supplementing the trace elements, a long-term anaerobic digestion of the food waste only resulted in a high methane yield of 0.396m3/kg VSadded and 75.6% of VS destruction with no significant volatile fatty acid accumulation. These results suggested that the typical Korean food waste was deficient with some trace elements required for anaerobic digestion.
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•Nitrifiers were enriched from activated sludge of domestic wastewater treatment.•Enriched nitrifiers were used to evaluate oxygen demand of nitrification.•Four species of microalgae ...were able to produce sufficient oxygen for nitrification.•Co-culture of microalgae and nitrifiers achieved full nitrification without aeration.•Electricity consumption of co-culture was lower than that of aerated bacteria culture.
The aim of this study was to investigate the possibility of using microalgae as an oxygen supplier for nitrification. In order to measure oxygen demands of nitrification, the activated sludge were cultured in a selective medium for 150 days, and enriched nitrifying biomass was successfully obtained. The enriched nitrifiers were used to estimate oxygen demands for nitrification and used for co-culturing with microalgae. Oxygen transfer rates (OTR) were also measured for various mixing conditions to determine if mixing without forced aeration could satisfy oxygen demands of nitrification. For all mixing conditions, OTR were lower than the oxygen uptake rates (OUR) of nitrifiers. As a result, nitrification without forced aeration was incomplete due to oxygen deficiency. Meanwhile, oxygen production rates (OPR) of 6 microalgae species were measured, and it was demonstrated that C. vulgaris, S quadricauda, D. communism and C. emersonii could supply sufficient oxygen for nitrification at all mixing modes. Based on these results, 4 species of microalgae with sufficient oxygen supplying capabilities were selected for co-culturing with enriched nitrifiers, and full nitrification was accomplished without forced aeration. Finally, the electric energy of co-culture was estimated and showed that energy consumption by co-culture was lower than that of aerated nitrifiers.
► Ammonia removal by air stripping followed pseudo-first-order kinetic model. ► Enhanced biomethanization of ammonia-stripped piggery wastewater was observed in batch and semi-continuous experiments. ...► It was found that a high concentration of sodium ion originated from sodium hydroxide for pH adjustment inhibited methane production.
In this study, the effects of ammonia removal by air stripping as a pretreatment on the anaerobic digestion of piggery wastewater were investigated. Ammonia stripping results indicated that ammonia removal was strongly dependent on pH and aeration rate, and the ammonia removal rate followed the pseudo-first-order kinetics. A significant enhancement of biomethanization was observed for wastewaters of which ammonia was air-stripped at pH 9.5 and pH 10.0. The methane productivity increased from 0.23
±
0.08
L CH
4/L
d of the control (raw piggery wastewater) to 0.75
±
0.11
L CH
4/L
d (ammonia-stripped at pH 9.5) and 0.57
±
0.04
L CH
4/L
d (ammonia-stripped at pH 10.0). However, the improvement of methane production from the piggery wastewater pretreated at pH 11.0 was negligible compared to the control, which was thought to be due to the high concentration of sodium ions supplied from sodium hydroxide for pH adjustment. From these results, it was concluded that ammonia removal through air stripping at the alkaline pH could be a viable option for preventing the failure of anaerobic digestion of the raw piggery wastewater. Additionally, it was also found that a high concentration of sodium ion originated from sodium hydroxide for pH adjustment inhibited methane production.
For the final disposal and reutilization of organic wastes, reduction of moisture content (MC) is essential because water contained in the organic waste generates leachate, lowers energy content, and ...indirectly causes odor problems. MC also directly determines the drying cost. In this study, MC of sewage sludge was effectively decreased by applying a biodrying process in which the microbial metabolic heat evaporated the water. By controlling the initial MC through air drying and its subsequent biodrying, it was found that 50-70 wt% was the optimal initial MC range for the sludge biodrying process. In this range, 33.7-47.1% of the initial water was removed by consuming 12.3-21.2% of the volatile solids (VS) initially contained in the sludge during 10 days of biodrying. When treating the same amount of raw sludge, air-dried and biodried sludge showed better performance as bulking agents than rubber and sawdust. About 55.1% of the initial water was removed from the mixture with air-dried sludge by consuming 23.8% of the initial VS and 38.3% of the initial water was lost from the sludge mixture with biodried sludge by consuming 14.0% of the initial VS during 12.1 days of biodrying. When rubber and sawdust were used as the bulking agents, only 18.2 and 16.5% of the initial water was removed, respectively. It was thought that the easily biodegradable VS contained in the air-dried sludge produced more heat and consequently removed more water. Although air-dried sludge showed better performance than biodried sludge, the use of biodried sludge as a bulking agent was thought to be more practical than air-dried sludge because biodried sludge can be used as bulking agent for the next round of biodrying in a repeated operation of the biodrying reactor. After biodrying, the lower heating value of the biodried sludge (51.5 wt% of MC) was 14.644 MJ kg
−1
, which was much higher than that of the original wet sludge.
A novel process termed as bioevaporation was established to completely evaporate wastewater by metabolic heat released from the aerobic microbial degradation of the organic matters contained in the ...highly concentrated organic wastewater itself. By adding the glucose solution and ground food waste (FW) into the biodried sludge bed, the activity of the microorganisms in the biodried sludge was stimulated and the water in the glucose solution and FW was evaporated. As the biodegradable volatile solids (BVS) concentration in wastewater increased, more heat was produced and the water removal ratio increased. When the volatile solids (VS) concentrations of both glucose and ground FW were 120 g L−1, 101.7% and 104.3% of the added water was removed, respectively, by completely consuming the glucose and FW BVS. Therefore, the complete removal of water and biodegradable organic contents was achieved simultaneously in the bioevaporation process, which accomplished zero-discharge treatment of highly concentrated organic wastewater.
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•A novel bioevaporation process was established to evaporate wastewater.•The higher the organics in wastewater was, the more the water was removed.•All water was removed when glucose and food waste volatile solids was 120 g L−1.•Complete removal of water and biodegradable organics was achieved.•Accomplish zero-discharge treatment of highly concentrated organic wastewater.
This study elucidated the importance of two critical enzymes in the regulation of butanol production in
Clostridium acetobutylicum
ATCC 824. Overexpression of both the 6-phosphofructokinase (
pfkA
) ...and pyruvate kinase (
pykA
) genes increased intracellular concentrations of ATP and NADH and also resistance to butanol toxicity. Marked increases of butanol and ethanol production, but not acetone, were also observed in batch fermentation. The butanol and ethanol concentrations were 29.4 and 85.5 % higher, respectively, in the fermentation by double-overexpressed
C. acetobutylicum
ATCC 824/
pfkA
+
pykA
than the wild-type strain. Furthermore, when fed-batch fermentation using glucose was carried out, the butanol and total solvent (acetone, butanol, and ethanol) concentrations reached as high as 19.12 and 28.02 g/L, respectively. The reason for improved butanol formation was attributed to the enhanced NADH and ATP concentrations and increased tolerance to butanol in the double-overexpressed strain.
An alternating mesophilic and thermophilic two stage anaerobic digestion （AD） process was conducted. The temperature of the acidogenic （A） and methanogenic （M） reactors was controlled as follows： ...System 1 （S1） mesophilic A-mesophilic M; （S2） mesophilic A-thermophilic M; and （S3） thermophilic A-mesophilic M. Initially, the AD reactor was acclimatized and inoculated with digester sludge. Food waste was added with the soluble chemical oxygen demand （SCOD） concentrations of 41.4-47.0 g/L and volatile fatty acids of 2.0-3.2 g/L. Based on the results, the highest total chemical oxygen demand removal （86.6%） was recorded in S2 while S3 exhibited the highest SCOD removal （96.6%）. Comparing S1 with S2, total solids removal increased by 0.5%;S3 on the other hand decreased by 0.1% as compared to S1. However, volatile solids （VS） removal in S1, S2, and S3 was 78.5%, 81.7%, and 79.2%, respectively. S2 also exhibited the highest CH4 content, yield, and production rate of 70.7%, 0.44 L CH4/g VSadded, and 1.23 L CH4/（L.day）, respectively. Bacterial community structure revealed that the richness, diversity, evenness, and dominance of S2 were high except for the archaeal community. The terminal restriction fragments dendrogram also revealed that the microbial community of the acidogenic and methanogenic reactors in S2 was distinct. Therefore, S2 was the best among the systems for the operation of two-stage AD of food waste in terms of CH4 production, nutrient removal, and microbial community structure.
This study aims to offer insights into how ciprofloxacin (CIP) impact bacterial community structures in the Sponge-MBR process when CIP is spiked into hospital wastewater. We found that the CIP ...toxicity decreased richness critical phylotypes such as phylum class ẟ-, β-, ɣ-proteobacteria, and Flavobacteria that co-respond to suppress denitrification and cake fouling to 37% and 28% respectively. Cluster analysis shows that the different community structures were formed under the influence of CIP toxicity. CIP decreased attached growth biomass by 2.3 times while increasing the concentration of permeate nitrate by 3.8 times, greatly affecting TN removal by up to 26%. Ammonia removal was kept stable by inflating the ammonia removal rate (p < 0.003), with the wealthy Nitrospira genus guaranteeing the nitrification activity. In addition, we observed an increasing richness of Chloroflexi and Planctomycetes, which may play a role in fouling reduction in the Sponge-MBR. Therefore, if the amount of antibiotics in hospital wastewater continues to increase, it is so important to extend biomass retention for denitrification recovery.
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•Alpha diversity rebound from added ciprofloxacin in Sponge membrane bioreactor•Flavobacteria, ẟ, β, and ɣ-proteobacteria co-enhanced fouling and denitrification.•Improved nitrification thanks to the increasingly richness Nitrospira genus•Ciprofloxacin expanded genetic relationship between suspended and attached growth.•The richness of Chloroflexi, Planctomycetes played a vital role in fouling reduction.
This study was aimed to investigate the possibility of using raw and anaerobically-digested piggery wastewater as culture media for a green microalga Chlorella vulgaris (C. vulgaris). Due to high ...concentration of ammonia and dark color, the microalga did not grow well in this wastewater. In order to solve this problem, air stripping and NaOCl-treatment were applied to reduce the concentration of NH3-N and the color intensity from the wastewater. Algal growth was monitored in terms of specific growth rate, biomass productivity, and nutrient removal efficiency. As a result, C. vulgaris grew without any sign of inhibition in air-stripped and 10-folds diluted anaerobically-digested piggery wastewater with enhanced biomass productivity of 0.57 g/L·d and nutrient removal of 98.7–99.8% for NH3-N and 41.0–62.5% for total phosphorus. However, NaOCl-treatment showed no significant effect on growth of C. vulgaris, although dark color was removed greatly. Interestingly, despite that the soluble organic concentration after air stripping was still high, the biomass productivity was 4.4 times higher than BG-11. Moreover, air stripping was identically effective for raw piggery wastewater as for anaerobic digestate. Therefore, it was concluded that air stripping was a very effective method for culturing microalgae and removing nutrients from raw and anaerobically-digested piggery wastewaters. KCI Citation Count: 0
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