Effects of Potassium Ferrate and Low-Temperature Thermal Hydrolysis Co-Pretreatment on the Hydrolysis and Anaerobic Digestion Process of Waste Activated Sludge

This study evaluated the effect of potassium ferrate(PF)and low-temperature thermal hydrolysis co-pretreatment on the promotion of sludge hydrolysis process and the impact on acid production in the subsequent anaerobic digestion process.The analytical investigations showed that co-pretreatment significantly facilitated the hydrolysis process of the sludge and contributed to the accumulation of short-chain fatty acids(SCFAs).The pretreatment conditions under the optimal leaching of organic matter from sludge were hydrothermal temperature of 75℃,hydrothermal treatment time of 12 h,and PF dosage of 0.25 g g^(−1)TSS(total suspended solids),according to the results of orthogonal experiments.By pretreatment under proper conditions,the removal rate of soluble chemical oxygen demand(SCOD)achieved 71.8%at the end of fermentation and the removal rate of total phosphorus(TP)was 69.1%.The maximum yield of SCFAs was 750.3 mg L^(−1),7.45 times greater than that of the blank group.Based on the analysis of the anaerobic digestion mechanism,it was indicated that the co-pretreatment could destroy the floc structure on the sludge surface and improve organic matter dissolving,resulting in more soluble organic substances for the acidification process.Furthermore,microbial community research revealed that the main cause of enhanced SCFAs generation was an increase in acidogenic bacteria and a reduction of methanogenic bacteria.

Effects of Biowaste-Derived Hydrochar on Anaerobic Digestion:Insights into Hydrochar Characteristics

Hydrochar prepared with four typical biowastes,pine wood,food waste,digested sewage sludge,and Chlorella were applied for the promotion of anaerobic digestion.The gas production and substrate composition were analyzed associated with the hydrochar characteristics.The results suggested that Chlorella hydrochar(C-C)showed the highest cumulative yield of methane(approximately 345 mL)with high total organic carbon(TOC)removal efficiency and low volatile fatty acids(VAFs)concentration.Especially,food waste hydrochar(F-C)showed a poor effect on anaerobic digestion and aroused 1.4–1.6 g/L accumulation of VAFs,in which the toxic components may account for the low efficiency.The C-C and sludge hydrochar(S-C)may develop direct interspecific electron transport(DIET)to facilitate the generation of methane by both surface groups and conductivity of the body structure,unlike pinewood hydrochar(P-C),which mainly depended on the aromatic matrix structure of hydrochar body.This work suggested that C-C can be the best candidate for the facilitation of anaerobic digestion,and N-containing biowaste like algae and lignocellulose like pine wood may establish different DIET pathways based on the physicochemical characteristics of hydrochar.

Effects of ultrasonic pretreatment on sludge dewaterability and extracellular polymeric substances distribution in mesophilic anaerobic digestion

Effect of ultrasonic pretreatment on sludge dewaterability was determined and the fate of extracellular polymeric substances （EPS） matrix in mesophilic anaerobic digestion after ultrasonic pretreatment was studied. Characteristics of proteins （PN）, polysaccharides （PS）, excitation-emission matrix （EEM） fluorescence spectroscopy and molecular weight （MW） distribution of dissolved organic matters （DOM） in different EPS fractions were evaluated. The results showed that after ultrasonic pretreatment, the normalized capillary suction time （CST） decreased from 44.4 to 11.1 （sec·L）/g total suspended solids （TSS） during anaerobic digestion, indicating that sludge dewaterability was greatly improved. The normalized CST was significantly correlated with PN concentration （R2 = 0.92, p 〈 0.01） and the PN/PS ratio （R2 = 0.84, p 〈 0.01） in the loosely bound EPS （LB-EPS） fraction. Meanwhile, the average MW of DOM in the LB- EPS and tightly bound EPS （TB-EPS） fractions also had a good correlation with the normalized CST （R2 〉 0.66, p 〈 0.01）. According to EEM fluorescence spectroscopy, tryptophan-like substances intensities in the slime, LB-EPS and TB-EPS fractions were correlated with the normalized CST. The organic matters in the EPS matrix played an important role in influencing sludge dewaterability.

Characteristics of high-sulfate wastewater treatment by two-phase anaerobic digestion process with Jet-loop anaerobic fluidized bed

A new anaerobic reactor, Jet-loop anaerobic fluidized bed （JLAFB）, was designed for treating high-sulfate wastewater. The treatment characteristics, including the effect of influent COD/SO42 ratio and alkalinity and sulfide inhibition in reactors, were discussed for a JLAFB and a general anaerobic fiuidized bed （AFB） reactor used as sulfate-reducing phase and methane-producing phase, respectively, in two-phase anaerobic digestion process. The formation of granules in the two reactors was also examined. The results indicated that COD and sulfate removal had different demand of influent COD/SO4^2- ratios. When total COD removal was up to 85%, the ratio was only required up to 1.2, whereas, total sulfate removal up to 95% required it exceeding 3.0. The alkalinity in the two reactors increased linearly with the growth of influent alkalinity. Moreover, the change of influent alkalinity had no significant effect on pH and volatile fatty acids （VFA） in the two reactors. Influent alkalinity kept at 400-500 mg/L could meet the requirement of the treating process. The JLAFB reactor had great advantage in avoiding sulfide and free-H2S accumulation and toxicity inhibition on microorganisms. When sulfate loading rate was up to 8. 1 kg/（m^3.d）, the sulfide and free-H2S concentrations in JLAFB reactor were 58.6 and 49.7 mg/L, respectively. Furthermore, the granules, with offwhite color, ellipse shape and diameters of 1.0-3.0 mm, could be developed in JLAFB reactor. In granules, different groups of bacteria were distributed in different layers, and some inorganic metal compounds such as Fe, Ca, Mg etc. were found.

Influence of lactic acid on the two-phase anaerobic digestion of kitchen wastes

To evaluate the influence of lactic acid on the methanogenesis, anaerobic digestion of kitchen wastes was firstly conducted in a two-phase anaerobic digestion process, and performance of two digesters fed with lactic acid and glucose was subsequently compared. The results showed that the lactic acid was the main fermentation products of hydrolysis-acidification stage in the two-phase anaerobic digestion process for kitchen wastes. The lactic acid concentration constituted approximately 50% of the chemical oxygen demand （COD） concentration in the hydrolysis-acidification liquid. The maximum organic loading rate was lower in the digester fed with lactic acid than that fed with glucose. Volatile fatty acids （VFAs） and COD removal were deteriorated in the methanogenic reactor fed with lactic acid compared to that fed with glucose. The specific methanogenic activity （SMA） declined to 0.343 g COD/（gVSS-d） when the COD loading were designated as 18.8 g/（L-d） in the digester fed with lactic acid. The propionic acid accumulation occurred due to the high concentration of lactic acid fed. It could be concluded that avoiding the presence of the lactic acid is necessary in the hydrolysis-acidification process for the improvement of the two-phase anaerobic digestion process of kitchen wastes.

Influence of temperature on performance of anaerobic digestion of municipal solid waste

The influence of temperature on the performance of anaerobic reactors for treating the organic fraction of municipal sohd waste （OFMSW） was studied. Batch digestion of OFMSW was carded out for 32 d at different temperature （25℃, 35℃, 45℃ and 55℃） conditions for total solid concentrations （TS） 17% with the ratio of total organic carbon to nitrogen （C/N） being, 25：1 respectively, while keeping other parameters constant such as inoculum, start-up pH, reactor volume （2 L） and so on. Temperature can influence the methanogenic bacteria activity, accordingly inhibiting the OFMSW biodegradation and stabilization efficiency. Anaerobic reactors excelled at TS reduction, total volatile solid reduction, chemical oxygen demand reduction, increasing cumulative biogas production, whose rate was at temperature （35℃ and 55℃） conditions. Methane concentration in the biogas was above 65% in four reactors. In addition, the fluctuation of temperatures resulted in the biogas production variation. The data obtained indicated that temperature had a significant influence on anaerobic process.

Effects of Oxytetracycline on Methane Production and the Microbial Communities During Anaerobic Digestion of Cow Manure

The effects of different concentrations of oxytetracycline （OTC） on the dynamics of bacterial and archaeal communities during the mesophilic anaerobic digestion （37＆#176;C） of cow manure were investigated. Before anaerobic digestion, OTC was added to digesters at concentrations of 20, 50, and 80 mg L-1, respectively. Compared with no-antibiotic control, all methane productions underwent different levels of inhibition at different concentrations of OTC. Changes in the bacterial and archaeal communities were discussed by using PCR-denaturing gradient gel electrophoresis （DGGE）. Results showed that OTC affected the richness and diversity of bacterial and archaeal communities. The bacterial genus Flavobacterium and an uncultured bacterium （JN256083.1） were detected throughout the entire process of anaerobic digestion and seemed to be the functional bacteria. Methanobrevibacter boviskoreani and an uncultured archaeon （FJ230982.1） dominated the archaeal communities during anaerobic digestion. These microorganisms may have high resistance to OTC and may play vital roles in methane production.

Combined pretreatment using CaO and liquid fraction of digestate of rice straw: Anaerobic digestion performance and electron transfer

To improve anaerobic digestion(AD)efficiency of rice straw,solid alkaline CaO and the liquid fraction of digestate(LFD)were used as pretreatment agents of rice straw.The results showed that AD performance of rice straw with CaOLFD pretreatment was optimal in different pretreatment methods of the CaO+LFD,CaOLFD,LFD+CaO,CaO,and LFD.The maximum methane yield(314 ml(g VS)^(-1))and the highest VFAs concentration(14851 mg·L^(-1) on day 3)of the CaOLFD pretreatment group were 81%and 118%higher than that of the control group,respectively.Under the action of solid alkaline CaO,the bacteria of Clostridium,Atopostipes,Sphaerochaeta,Tissierella,Thiopseudomonas,Rikenellaceae,and Sedimentibacter could build up co-cultures with the archaeal of Methanosaeta,Methanobacterium,and Methanosarcina performing direct interspecies electron transfer(DIET)and improving AD performance of rice straw.Therefore,the combined pretreatment using CaO and LFD could not only pretreat rice straw but also stimulate co-cultures of microorganism to establish DIET enhancing AD efficiency.

The Role of Biochar to Enhance Anaerobic Digestion: A Review

Biochar,one of the products of thermochemical conversion of biomass,possesses specific physiochemical properties such as conductivity,pore adsorption,surface functional groups,and cation exchange capacity.Anaerobic digestion(AD)as a classical bio-wastes conversion technology,suffers from inhibitions,process instability,and methanogenic inefficiency which limit its efficiency.With the advantages of pH buffering,functional microbes enrichment,inhibitors alleviating,and direct interspecies electron transfer(DIET)accelerating,biochar suggests a promising application as additives for AD.Herein,this paper reviewed the noting physicochemical properties of biochar,and discussed its roles and related mechanisms in AD.Further,this paper highlighted the advantages and drawbacks,and pointed out the corresponding challenges and prospects for future research and application of biochar amending AD.

Effects of Different States of Fe on Anaerobic Digestion:A Review

Anaerobic digestion is widely used in the treatment of industrial wastewater,excess activated sludge,municipal waste,crop straw and livestock manure,with the functions of environmental protection and energy recovery. This review summarizes and evaluates the present knowledge of effects of different states of Fe( ZVI,Fe( II),Fe( III)) on hydrogen and methane production in anaerobic digestion process. The potential promotion effects of iron oxides nanoparticles( IONPs),especially magnetite nanoparticles on anaerobic digestion are also mentioned. Fe plays important role in transporting electron,stimulating bacterial growth and increasing hydrogen and methane production rate by promoting enzyme activity. Adding Fe with different morphologies and valence states in anaerobic digestion to increase biogas( hydrogen and methane) production and enhance organic matter degradation simultaneously,which has attracted many scientists' attention in recent years. Rapid progress in this area has been made over the last few years,since Fe is essential to the fermentative hydrogen and methane production,while few is known about how Fe affects the fermentative biogas production. This review is significant to maintain the stable operation of the biogas project.

Anaerobic digestion for waste water poultry manure by UBF reactor

In this experiment the performance of UBF process treatment for wastewater chicken manure was tested under the condition of constant temperature of 35℃and the volume of UBF is 4 liters.The experiment covered two stages:the first was start up with phase I and phase II,the second was steady state.The following results average of operation period were obtained:(1)During the period of start up phase I operation the biogas production rate 0.39v/(v.day)at the volumetric COD loading rate of 2.97 kg COD/(m 3.d)with COD removal 76.85%and hydraulic retention time of 10.04 hours and phase II the biogas production rate 3.86 v/(v.day)at the volume loading rate 11.69 kg COD/(m 3.d)have been achieved with COD removal 82.47%and HRT 16.45 hours.UBF process had resistance to the quantitative shock load.(2)During the steady state operation,the biogas production rate 9.83v/(v.day)at loading rate of 28.85 kg COD/(m 3.d)and COD removal efficiency 80.03%and hydraulic retention time of 18.73 hours have been achieved for this reactor.The operation of UBF reactor was very stable.

Effect of ultrasonic assisted KOH pretreatment on physiochemical characteristic and anaerobic digestion performance of wheat straw

In this study,ultrasonic field was applied during potassium hydroxide(KOH) pretreatment of wheat straw(WS).Three concentrations of KOH(2%,4%,and 6%) were tested during pretreatment.The results showed that there was a significant influence of the ultrasonic assisted KOH pretreatment(KOH(Upt)) on physiochemical characteristics of WS during pretreatment as well as on digester performance.The pretreatment time was optimized to 36 h for all KOH concentrations.The highest total volatile fatty acid(TVFA) productions(3189 mg·L^-1) from 6%KOHupt samples were observed.Similarly,the SEM analysis and FTIR observation revealed that KOH(Upt) effectively disrupted the physical morphology of WS and successful breaking of lignin and hemicellulose linkage between carboxyl groups.Moreover,the highest biogasification(555 ml·(g VS(loaded))^-1) and biomethane productions(282 ml·(g VS(loaded))^-1) from 4%KOH(Upt) digesters,with 69% of biodegradability,indicated significant availability of organic matter from KOH(Upt).The R^2 values(0.993-0.998) in Modified Gompertz Model indicated that the model was feasible to predict methane yield for this study.Similarly,the Bo values for 4%KOH(Upt)(283.30±2.74 ml·(gVS(loaded))^-1) were also in agreement to the experimental methane yield.These results suggested that ultrasonic addition during KOH pretreatment of WS can effectively increase the organic yield during pretreatment.Moreover,the increase in methane production from 4% KOH(Upt) suggested that digester performance can be improved with lower KOH concentrations using this pretreatment.

Lower temperature hydrothermal pretreatment improves the anaerobic digestion performance of spent cow bedding

The anaerobic digestion(AD)performance of spent cow bedding was investigated with different hydrothermal pretreatment(HP)conditions.Spent cow bedding was pretreated with low temperatures(50,70,and 90℃)and different pretreatment times(2-72 h)with ammonia and without ammonia.The results showed that spent cow bedding was a good raw material for AD.After pretreatment,the concentration of volatile fatty acids(VFAs)in the group of hydrothermal pretreatments with ammonia(HPA)was higher than that in the HP group at the same pretreatment temperature and time.The optimal pretreatment condition was achieved with an HPA of 50℃ holding for 72 h.At the optimal condition,the highest concentration of VFAs was 1.58-10.85 times higher than that of the other pretreated groups.The highest hemicellulose and lignin removal rates were 58.07%and 10.32%,respectively.The highest methane yield was 163.0 ml(g· VS)^(-1),which was 48.9%higher than that of the untreated group.The VFAs,pH,and reducing sugars showed positive relationships with the methane yield.Therefore,HP at low temperature can enhance the AD performance of spent cow bedding.

Effects of Agitating Intensity on Anaerobic Digestion Performance of Corn Straw Silage

Anaerobic fermentation can increase biomass energy use efficiency of crop straws and realize win-win of energy and environment.This paper explored the biogas generation performance of anaerobic digestion of cow dung liquid as nitrogen source in three different levels of stirring intensity at 30℃ constant temperature condition. Through p H value,biogas production,chemical oxygen demand( COD),methane content,volatile fatty acid( VFA),principal component analysis( PCA) and modified Gompertz model,effects of agitating intensity on anaerobic digestion performance of corn straw silage were evaluated. Results indicate that the COD removal rate of three agitating intensity levels is higher than 85%,and p H value is about 6.5; the cumulative biogas production after 20 days is 2h > 4h > 1h of agitating; in the49 th day,the biogas production is 1.9 Lat 30 min /2h,1.7 L at 30 min /4 h,and 1. 6 Lat 30 min / h; the maximum biogas production rate is 30 min /2h > 30 min /4h > 30 min / h; and the maximum methane production rate is 30 min /4h > 30 min /2h > 30 min / h; in the same energy consumption,the biogas production at 30 min /4h is higher than 1h. In conclusion,overall analysis of energy consumption and economic factors indicate that 30 min /4 h agitating intensity is more suitable for straw biogas fermentation project. This study is expected to provide theoretical foundation for biogas fermentation project.

Research Progress of Anaerobic Digestion Pretreatment of Antibiotic Waste

Anaerobic digestion is one of the effective ways to dispose of antibiotic pharmaceutical waste. However,the inhibition of antibiotics on anaerobic fermentation microorganisms seriously hinders the normal physiological activities of anaerobic microorganisms and then affects the efficiency of anaerobic digestion. In order to solve this problem,related scholars have done a lot of research. It has been found that pretreatment of anaerobic microorganisms and antibiotic pharmaceutical waste can significantly improve the efficiency of anaerobic digestion. In this paper,the current feasible pretreatment methods were summarized,and the application of different pretreatment methods was analyzed to provide reference for improving pretreatment methods and improving anaerobic biological treatment ability of antibiotic waste.

Dimensioning of an Anaerobic Digester for the Treatment of Chicken Manure and for the Production of Biogas: The Case Study of a Chicken Farm in Yaokokoroko (Côte d’Ivoire)

This study allowed us to highlight the level of pollution of a BAYA River water near several poultry farms and the sizing of an anaerobic digester that will be able to treat chicken manure from a poultry farm (BRIN FOUNDATION). To evaluate this pollution, the parameters such as ammonium (NH4+), Phosphate (PO43-), Biochemical Oxygen Demand (DBO5) and Nitrate (NO3-) were determined. For sampling point P1, the concentrations in mg/L of these parameters are (25.00 ± 4.25), (0.40 ± 0.20), (98.00 ± 6.35) and (96.00 ± 5.35), respectively. On the other hand, for sampling point P2, the concentrations in mg/L of these parameters are respectively (33.00 ± 9.05), (0.70 ± 0.12), (123 ± 7.13) and (93 ± 7.10). These values indicate a strong organic pollution of the BAYA River. The determination of the different concentrations of the organic pollution parameters allowed us to evaluate the degradation and the quality of the water of the BAYA River water, by the poultry activity. However, considering the physicochemical properties of the waste (chicken manure), which is the main source of organic pollution, we have considered an energy recovery through the production of biogas. This requires the design, sizing, and implementation of an anaerobic digester in a poultry farm. Therefore, the project would require the construction of an adapted masonry type anaerobic digester with a capacity of 10 m3.

Analysis on Present Situation of Anaerobic Digestion Products of Sludge in Landscaping Application and Market Demand in Chongqing

Taking the anaerobic digestion products of sludge as the object, through the analysis on the development of garden substrate market at home and abroad and the development status of horticultural products from the anaerobic digestion products, the direction for the utilization of the anaerobic digestion products of sludge was pointed out. Based on the demand of Chongqing’s garden market, this paper analyzed the potential utilization of sludge anaerobic digestion products in Chongqing, and briefly introduced the research status of landscaping utilization of sludge anaerobic digestion products in Chongqing, in order to provide reference for the industry.

Optimization of the Production of Biogas in Anaerobic Digestion by the Addition of Hydrolytic Microorganisms

It is well known that fossil fuels are one of the major pollutants that contribute to climate change and there is a need to develop alternatives to their uses.One option is the use of a renewable fuel such as biogas obtained from the breaking down of organic matter in the anaerobic digestion process.When biogas is cleaned up to a certain quality,it can substitute the use of natural gas.However,this slow process requires optimization to increase the amount of gas.There are chemical,physical and biological treatments for organic matter to increase the amount and quality of biogas.In the former research,a biological treatment was tested by adding a selection of microorganisms that showed hydrolytic activity to an anaerobic digester for its optimization.First,a selection of microorganisms with the ability to grow in fresh sewage sludge as only nutrient was selected.Then,the lipolytic,cellulolytic and PA(Proteolytic Activity)of microorganisms was tested using selective growth media.Finally,10 samples with the greatest hydrolytic activity were used to evaluate their effects in the increasing of biogas production in the anaerobic process.The results showed that 83%of the microorganisms with the ability to grow in sewage sludge were proteolytic,while the percentage of lipolytic and cellulolytic microorganisms was smaller.Furthermore,it was found that proteolytic microorganisms are the ones that increase biogas yield in a maximum of 80%with a COD(Chemical Oxygen Demand)reduction of 58%.

Anaerobic Digestion of Liquid Waste from an AttiékéFactory: From the Experimental Scale to the Semi-Industrial Scale

This study focused on the transfer of experimental results of anaerobic digestion of liquid waste from an attiéké (steamed cassava semolina) factory to a 6 m3 pilot digester. The experimental digester and the pilot were powered as follows: Lw + U + C (liquid waste + urine + cow dung). To the results, the experimental digester mesophilic with a progressive elimination of COD. Also, the nitrogen concentrations in the experimental reactor had little removal with alkaline pH. As for the biogas product in this digester, a volume of 3.6 m3 was obtained with a positive flammability test. The transition from the laboratory scale to the semi-industrial scale retains the results of purification and fuel biogas production of the experimental digester.

Comparative Analysis of Conventional Anaerobic Digestion and Bio-Electrochemical Systems in Waste Organics Utilization

Anaerobic digestion is often used as an approach to deal with high COD waste streams. Compared to the aeration systems it allows better energy management due to the biogas production but also has several limitations including inlet waste streams quality and the additional equipment required for energy harvesting. In recent years, the bio-electrochemical systems (BES) and processes are intensively studied as a method for organic waste utilization, including wastewater. They potentially could bring several benefits to the wastewater treatment, mainly due to avoiding aeration (and aeration cost) and direct energy recovering in the form of electricity. Besides their anaerobic nature, the biological processes in BES are respiration-like contrary to the fermentative degradation typical for conventional anaerobic digestion which eventually will provide better mineralization and higher efficiency in terms of COD and BOD removal in such reactors. This study is a direct comparison between conventional anaerobic digestion and Microbial Fuel Cell (as a typical BES reactor) during utilization of wastewater from industrial production of ethanol by fermentation. COD removal rates and dynamics, energy recovery properties and parameters such as secondary sludge production are investigated in order to characterize the feasibility and technological readiness of BES as a step towards their commercialization.