Study on anaerobic co-digestion with distillery wastewater to improve the dewatering property of the secondary sludge

This paper presents the results obtained for the effluent dewatering properties of anaerobic digestion of secondary sludge （SS） and anaerobic co-digestion of mixture of this sludge with the distillery wastewater （DW） under thermophilic （55±1 ℃）, 5 L of working volume, three parallel lab-scale conditions. Its mixtures were prepared with a DW content of 25%and 50% and the C/N ratios of mixtures are 13.1 and 17.6, respectively. The effluent dewatering properties were evaluated under stable conditions which the biogas yield and the effluent pH were steady. The natural settleability, biogas yield, centrifugal dewatering, centrifugal supernatant turbidity and specific resistance filtration （SRF） were investigated. The results showed that the effluent dewatering properties of anaerobic co-digestion of mixtures between SS and DW were better than that of anaerobic digestion of SS alone. In the anaerobic digestion system with the feed were SS, mixture of SS and a DW content of 25%and 50% in order, the net biogas yield of secondary sludge in ADSA,ADSB and ADSC were 0.42 0.507 and 0.511 m3 biogass/kg.VS.d ; compared with the biogas yield in anaerobic digestion system A （ADSA）, the biogas yield in anaerobic digestion system B （ADSB） and anaerobic digestion system C （ADSC） had been increased by more than 20% respectively; the SRF of three digested sludge are（were） from 6.8×10^13, 1. 1×10^13 to 5.1×10^12 m/Kg, natural settling rates of 12 h are 26, 37 and 56% and that of 24 h are 32%, 45% and 59% respectively; the centrifugal dewatering rate of 3 min at speed of 1000 rpm were 16%, 31% and 51% respectively; the turbidity of centrifugal supernatant were 804, 754 and 678FTU simultaneously.

Improvement of Methane Production from Corn Stalk for Whole Slurry Anaerobic Co-digestion Under Hydrothermal Wastewater Pretreatment

Corn stalk hydrothermal wastewater(CSHW)was used as a pretreatment for whole-slurry anaerobic co-digestion instead of conventional acid pretreatment.CSHW pretreatment was conducted at 20℃,35℃and 50℃for 3,6 and 9 h,after which all experimental groups were digested at 35℃for 24 days.This pretreatment method efficiently broke the lignocellulose structure of the corn stalk.Different from the volatile fatty acids(VFAs)content,the pH and RS contents were relatively higher than those of the control during the pretreatment process.Furthermore,the highest methane production[185.03 mL•g-1 VS(volatile solid)]was achieved at 55.46%under 35℃in 6 h,which was higher than that of the normal corn stalk anaerobic digestion.The VFAs contents and pH increased compared to CK upon the addition of NaOH to adjust pH,and the RS content also increased slightly due to the degradability of lignocellulose during the whole-slurry anaerobic co-digestion.This work provided a potential method to sustainably treat wastewater and improve fermentation performance.

Effect of goethite on anaerobic co-digestion process of corn straw and algae biomass

1 Introduction Recently the demand for fossil fuel has grown significantly with the rapid development of the Chinese economy.Renewable energy was developed to replace traditional fossil fuels,which would decrease the

Phylogenetic Analysis of Anaerobic Co-Digestion of Animal Manure and Corn Stover Reveals Linkages between Bacterial Communities and Digestion Performance

Over 3 million tons of manures are produced annually in the United States and pose environmental and health risks if not remediated. Anaerobic digestion is an effective method in treating organic wastes to reduce environmental impacts and produce methane as an alternative energy. Previous studies suggested that optimization of feed composition, hydraulic retention time, and other operational conditions can greatly improve total solids removal and increase methane productivity. These environmental factors improve functionality by altering the microbial community structure but explicit details of how the bacterial community shifts are poorly understood. Our investigations were conducted to investigate the relationship between environmental factors, microbial community structure and bioreactor efficiency by using metagenomic analysis of the microbial communities. Our results indicated that the bioreactor with the greatest methane production, digestion efficiency and reduced levels of E. coli/Shigella had a distinctive community structure at the genus level with unique and abundant uncultivated strains of Bacteroidetes. Moreover the same bioreactor was enriched in Aminomonas paucivorans and Clostridia populations that can utilize secondary metabolites produced during cellulose/hemicellulose degradation to generate hydrogen and acetate. Hence specific digestion conditions that enrich for these populations may provide a route to the optimization of co-digestion systems and control the variability in reactor performance.

Bioenergy Production from Anaerobic Co-Digestion of Sewage Sludge and Abattoir Wastes

Energy is the pillar of human economic development. Several energy sources, renewable and non-renewable, have been exploited to assure and sustain the need for sustainable development. However, depletion of non-renewable energy sources forced researchers to search for alternative cost effective and environmental friendly energy sources. Thus, conversion of waste materials into energy has obtained considerable attention. In line with this, the aim of this study is to investigate the improvement of bio-energy production through anaerobic digestion of mixture of wastes from sewage sludge and abattoir sources. The abattoir waste is functioned as a co-substrate. Laboratory scale batch anaerobic co-digestion of the waste is carried out under mesophilic condition for 20 days. Sewage Sludge (SS) alone, and different mix ratios of SS to Abattoir Waste (AW) were analyzed for bioenergy production. Besides, the nutrient values and reduction in volume of the sewage after digestion were determined. The results show that methane productions of 33.8%, 48.3% and 56.9% were obtained for SS alone and for SS:AW mix ratios of 4:1 and 3:2, respectively. The nutrient values of the slurry increased as mix ratio decreased due to the increase in the amount of AW. The obtained results indicate that bio-energy production can be improved through co-digestion of SS using AW as a co-substrate;thus warranting further investigation for the practical application in the energy production.

High-solid Anaerobic Co-digestion of Food Waste and Rice Straw for Biogas Production

Anaerobic co-digestion of food waste（FW） and rice straw（RS） in continuously stirred tank reactor（CSTR） at high organic loading rate（OLR） was investigated. Co-digestion studies of FW and RS with six different mixing ratios were conducted at an initial volatile solid（VS） concentration of more than 3 g VS · L-1. The biogas production, methane contents, degradation efficiency of VS, chemical oxygen demand（COD） and volatile fatty acids（VFAs） were determined to evaluate the stability and performance of the system. The results showed that the co-digestion process had higher system stability and higher volumetric biogas production than mono-digestions. Increase in FW content in the feedstock could increase the methane yield and shorten retention time. The efficiency of co-digestion systems mainly relied on the mixing ratios of FW and RS to some extent. The highest methane yield was 60.55 m L· g V· S-1 · d-1 at a mass ratio（FW/RS） of 3 ： 1, which was 178% and 70% higher than that of mono-digestions of FW and RS, respectively. Consequently, the anaerobic co-digestion of FW and RS could have superior stability and better performance than monodigestions in higher organic loading system.

Characterization of Digestates from Anaerobic Co-Digestion of Manioc Effluent, Human Urine and Cow Dung

This study focused on the characterization of digestates resulting from anaerobic digestion of manioc effluents from attiéké factories. Two types of digestate were characterized, one consisting of manioc effluent + urine and another composed of manioc effluent + urine + cow dung. As a result, these residues of bio-digestion rich in nutrients (NPK) can be used as agricultural fertilizer. Moreover, the determination of some microorganisms and heavy metals digestates allowed to better appreciate its fertilizing quality. These parameters remained in accordance with the quality standards of a digestate prescribed. These results show that digestates from anaerobic co-digestion of manioc effluents, urine and cow dung can be used without fear as an agricultural biofertilizer.

Bioelectricity from Anaerobic Co-Digestion of Organic Solid Wastes and Sewage Sludge Using Microbial Fuel Cells (MFCs)

Recently microbial fuel cells (MFCs) have been considered as an alternative power generation technique by utilizing organic wastes. In this study, an experiment was carried out to generate bioelectricity from co-digestion of organic waste (kitchen waste) and sewage sludge as a waste management option using microbial fuel cell (MFC) in anaerobic process. A total of five samples with different sludge-waste ratio were used with zinc (Zn) and cupper (Cu) as cell electrodes for the test. The trends of voltage generation were different for each sample in cells such as 350 mV, 263 mV, 416 mV maximum voltage were measured from sample I, II and III respectively. It was observed that the MFC with sewage sludge showed the higher values (around 960 mV) of voltages with time whereas 918 mV obtained with organic waste. Precisely comparing cases with varying the organic waste and sewage sludge ratio helps to find the best bioelectricity generation option. Using MFCs can be appeared as the solution of electricity scarcity along the world as an efficient and eco-friendly manner as well as organic solid waste and sewage sludge management.

Anaerobic Co-digestion Process Efficiency Estimation in Phases as an Alternative for Municipal Waste Treatment

The incorrect disposal of the waste generated in the municipalities contributes to water and soil contamination,resulting in a real concern in order to find an adequate disposal as well as obtain by-products that can be used to reduce CO2 emissions.Anaerobic digestion turns out to be the most efficient treatment,both in environmental and economic terms.The objective of this study is to evaluate the anaerobic co-digestion process in phases as an alternative for the treatment of municipal waste:sludge from water treatment plants and the biodegradable part of Municipal Solid Waste(MSW),for three HRTs(Hydraulic Retention Times).Testing results show up a max elimination of 70.68%in VS(Volatile Solids)and 74.01%in COD(Chemical Oxygen Demand).With these percentages of elimination on average,15.96 L/d of biogas was produced,for each kg of COD eliminated 0.56 m3 of biogas was produced and for each kg of SV 0.85 m3 and methane of 50.10%.

Anaerobic Co-Digestion of Fish Processing Waste with Cow Manure and Waste of Market (Rests of Fruits and Vegetables): A Lab Scale Batch Test

The aim of this work was to use fish processing waste (FW) as main substrate for anaerobic digestion. To enhance the biogas production of FW, co-digestion was done with two other substrates: cow dung (CD) and waste of market (MW). Batch test was carried out in an 1 L glass digester in a temperature controlled chamber at 38°C. The following mixtures were carried out: FW with CD respectively at different ratios 100:0% (A), 80:20% (B) and 60:40% (C);FW with MW at the following ratio 80:20% (D);FW with CD and MW respectively at these ratios 80:10:10% (F) and 60:20:20% (G). The biogas produced was measured using a milligas counter® and the volume of gas was recorded. The gas composition was determined using gas chromatography. With a pH stable for raw substrates and mixtures, TS and VS (%TS) contents for FW were respectively 31.01% and 91.55%. Between 3 to 13 days of experimentation, the highest flow rate was observed. The percentage of methane was more important for mixtures B and D, 61% and 59% respectively. pH and VOA/TIC were stable at the end of the batch test for all mixtures, meaning that the organic matter was already well digested. The highest values of Volatile Solid Removal (VSR) were found for mixtures C, D, F and G. Therefore, the promising mixtures for next experimentations in large scale are B and D.

Effects of mixture ratio on anaerobic co-digestion with fruit and vegetable waste and food waste of China

The biochemical methane potentials for typical fruit and vegetable waste （FVW） and food waste （FW） from a northern China city were investigated, which were 0.30, 0.56 m3 CH4/kgVS （volatile solids） with biodegradabilities of 59.3% and 83.6%, respectively. Individual anaerobic digestion testes of FVW and FW were conducted at the organic loading rate （OLR） of 3 kg VS/（m3-day） using a lab-scale continuous stirred-tank reactor at 35°C. FVW could be digested stably with the biogas production rate of 2.17 ma/（m3-day） and methane production yield of 0.42 m3 CH4/kg VS. However, anaerobic digestion process for FW was failed due to acids accumulation. The effects of FVW： FW ratio on co-digestion stability and performance were further investigated at the same OLR. At FVW and FW mixing ratios of 2：1 and 1：1, the performance and operation of the digester were maintained stable, with no accumulation of volatile fatty acids （VFA） and ammonia. Changing the feed to a higher FW content in a ratio of FVW to FW 1：2, resulted in an increase in VFAs concentration to 1100-1200 rag/L, and the methanogenesis was slightly inhibited. At the optimum mixture ratio 1：1 for co-digestion of FVW with FW, the methane production yield was 0.49 m3 CH4/kg VS, and the volatile solids and soluble chemical oxygen demand （sCOD） removal efficiencies were 74.9% and 96.1%, respectively.

Methanogenic community dynamics in anaerobic co-digestion of fruit and vegetable waste and food waste

A lab-scale continuously-stirred tank reactor （CSTR）, used for anaerobic co-digestion of fruit and vegetable waste （FVW） and food waste （FW） at different mixture ratios, was operated for 178 days at the organic loading rate of 3 kg VS （volatile solids）/（m3.day）. The dynamics of the Archaeal community and the correlations between environmental variables and methanogenic community structure were analyzed by polymerase chain reactions - denaturing gradient gel electrophoresis （PCR-DGGE） and redundancy analysis （RDA）, respectively. PCR-DGGE results demonstrated that the mixture ratio of FVW to FW altered the community composition of Archaea. As the FVW]FW ratio increased, Methanoculleus, Methanosaeta and Methanosarcina became the predominant methanogens in the community. Redundancy analysis results indicated that the shift of the methanogenic community was significantly correlated with the composition of acidogenic products and methane production yield. Different mixture ratios of substrates led to different compositions of intermediate metabolites, which may affect the methanogenic community. These results suggested that the analysis of microbial communities could be used to diagnose anaerobic processes.

Effects of cow manure ratios on methane production and microbial community evolution in anaerobic co-digestion with different crop wastes

The present study investigated the effects of cow manure ratios mixed with maize stover,rice straw,and wheat stalk at 3,2,1(total solid based,TS-based),respectively,on methane production and microbial community structure during the anaerobic co-digestion process.Results showed cow manure co-digested with maize stover,wheat stalk,and rice straw at ratios of 2,1,and 3 had the highest cumulative methane yields(272.99,153.22167.73 mL/g volatile solid(VS),respectively)and better stability(e.g.pH,volatile fatty acids(VFAs)and their component).The main microbe evolution had a similar trend which was Petrimonas and Methanosaeta in the early digestion process(Days 0-7)and then evolved into Longilinea,Ruminofilibacter,and Methanosarcina with the progress of digestion,but the relative abundance of these microbes in each reactor was different.It was worth noting that Caldicoprobacter in cow manure to maize stover ratio of 2,and to rice straw ratio of three reactors had a relatively higher proportion than reactor of cow manure to wheat stalk ratio of 1,and Hydrogenophaga was the specific bacterium in cow manure to wheat stalk ratio of 1 reactor.In addition,Petrimonas showed positive relationship with VFAs and Longilinea was the opposite.Methanosaeta and Methanobacterium contributed the most during the peak period of methane production in cow manure and maize stover co-digested reactor,and showed positive relationship with acetic acid.However,Methanosarcina and Methanospirillum made a great contribution during the peak period of methane production in cow manure co-digested with wheat stalk and rice straw reactors.These findings could provide further information on the application of cow manure co-digested with crop wastes.

Anaerobic co-digestion of rice straw and digested swine manure with different total solid concentration for methane production

This study aimed to investigate potential methane production through anaerobic co-digestion of rice straw and digested swine manure with different total solids.The research was carried out in bench scale with utilizing batch system.To evaluate the stability of anaerobic co-digestion process,the experiment was run in triplicate.The anaerobic co-digestion process was operated in 500 mL batch digesters under constant agitation speed and temperature.The agitation speed was maintained at 270 r/min.Temperature of the batch system was set and maintained at 35℃.Digested swine manure utilized in this experiment was obtained from semi-continuous digesters run at steady state condition,with 25 days of hydraulic retention time under mesophilic condition.Rice straw(RS)generated the highest methane production at 3% total solids(TS)which was around(1814±47.43)mL,where in this concentration,it had C:N ratio at 10.6:1.Rice straw obtained the highest methane yield at 3% TS,which was around(141.4±3.70)mL CH_(4)/g volatile solids(VS)added.Rice straw also had the highest chemical oxygen demand(COD)removal and VS reduction at 3% TS which were around(52.97%±1.46%)and(61.81%±1.04%),respectively.

Anaerobic co-digestion of thermo-alkaline pretreated microalgae and sewage sludge: Methane potential and microbial community

To improve methane production from sewage sludge(SS),co-digestion of SS and microalgae(MA)was studied and the application of thermo-alkaline pretreatment to MA was evaluated.The results showed that thermo-alkaline pretreatment at 90℃ for 120 min on MA was the optimum pretreatment condition.Furthermore,when the volatile solids(VS)ratio of SS and MA was 1:2,the methane yield reached maximum(368.94 mL/g VS).Fourier transform infrared(FT-IR)and thermogravimetric analysis confirmed the synergetic effects of thermoalkaline pretreated MA on its co-digestion with SS.The analyses of microbial community indicated that Methanobacterium and Methanosarcina were the dominant methanogens during the co-digestion process.However,the relative abundance of Methanosarcina in thermoalkaline pretreated groups was higher compared to unpretreated groups.The microbial community structure might be affected by thermo-alkaline pretreatment rather than by the MA dosage in the co-digestion.

An automated medium scale prototype for anaerobic co-digestion of olive mill wastewater

Olive oil production constitutes one of the most important agro-industrial business for Mediterranean countries,where 97% of the international production is focused.Such an activity,mainly carried out through three phase olive oil mill plants,generates huge amounts of solid and liquid by-products further than olive oil.Physico-chemical features of these by-products depend on various factors such as soil and climatic conditions,agricultural practices and processing.As currently carried out,the disposal of these byproducts may lead to numerous problems taking into account management,economic and particularly environmental aspects.Indeed,olive mill wastewater is not easily biodegradable due to its high chemical and biochemical oxygen demand,its high content in phenolic compounds,high ratio C/N and low pH,leading consequently to soil and water source pollution.Considering,the above-mentioned statements,olive mill waste disposal constitutes nowadays a challenge for oil industry stakeholders.It becomes necessary to look for alternative solutions in order to overcome environmental problems and ensure the sustainability of oil industry.Anaerobic co-digestion of olive mill wastewater with other agro-industrial matrices could be one of these solutions;since it offers the possibility to produce green energy and break down toxicological compounds contained in these wastewater for a better disposal of the digested matrices as soil conditioner.In this contest,this note reports the functioning principle of an automated medium scale plant for anaerobic co-digestion of olive mill wastewater.

Anaerobic co-digestion of municipal biomass wastes and waste activated sludge: Dynamic model and material balances

The organic matter degradation process during anaerobic co-digestion of municipal biomass waste （MBW） and waste-activated sludge （WAS） under different organic loading rates （OLRs） was investigated in bench-scale and pilot-scale semi-continuous stirred tank reactors. To better understand the degradation process of MBW and WAS co-digestion and provide theoretical guidance for engineering application, anaerobic digestion model No. 1 was revised for the co-digestion of MBW and WAS. The results showed that the degradation of organic matter could be characterized into three different fractions, including readily hydrolyzable organics, easily degradable particulate organics, and recalcitrant particle organics. Hydrolysis was the rate-limiting step under lower OLRs, and methanogenesisis was the rate-limiting step for an OLR of 8.0 kg volatile solid （VS）/（m^3·day）. The hydrolytic parameters of carbohydrate, protein, and lipids were 0.104, 0.083, and 0.084 kg chemical oxygen demand （COD）/（kg COD·hr）, respectively, and the reaction rate parameters of lipid fermentation were 1 and 1.25 kg COD/（kg COD.hr） for OLRs of 4.0 and 6.0 kg VS/（m^3·day）. A revised model was used to simulate methane yield, and the results fit well with the experimental data. Material balance data were acquired based on the revised model, which showed that 58.50% of total COD was converted to methane.

Two-phase anaerobic co-digestion of dairy manure with swine manure

In order to solve the problems associated with high fiber content,and the ensuing lower biogas volume yield in anaerobic digestion of dairy manure,a study of the co-digestion of separated liquids from dairy manure combined with swine manure using a two-phase anaerobic digestion process was conducted.The influence of level of total solids(TS)and hydraulic retention time(HRT)of the mixed liquor on the specific methane production were studied.Three TS levels 8%,10%and 12%were investigated.Analysis of the results show that a maximum specific methane yield of 132.99 L/kg volatile solids(VS),can be obtained with a TS of 9%,an inoculation rate of 30%,the duration of hydrolytic acidification phase of 5 d,and an HRT of the methanogenic phase of 10 d.These findings could provide directions for improving the biogas production by performing the co-digestion of dairy manure with swine manure.

Anaerobic co-digestion of sodium hydroxide pretreated sugarcane leaves with pig manure and dairy manure

Sugarcane leaves(SL)pretreated by alkali was used as substrate to enhance biogas production via mesophilic anaerobic digestion(AD)in this study.Effectiveness of different concentrations of NaOH pretreatment on AD performance was investigated.Results showed that compared to untreated sample of SL,the lignocellulose(LCH)content of NaOH pretreated group was decreased by 5.79%-16.85%.However,the cumulative biogas production of the pretreated samples increased in the range of 34.54%-82.67%;moreover,T90 was shorten by 5-7 d.The highest anaerobic digestibility of SL was achieved at 6%NaOH pretreatment,which produced 287.30 mL/g TS of biogas.A significant interactive effect of the three parameters(temperature,SL/manure mixing ratio and C/N ratio)was found on the biogasification of anaerobic co-digestion,and a maximum biogas production was achieved at 36.2oC,mixing ratio of 1.6 and C/N ratio of 29.2.These show that the verification experiment confirmed the optimization results.This study provides meaningful insight for exploring efficient pretreatment strategy and optimal condition to stabilize and enhance AD performance for practical application.

Online measurement of alkalinity in anaerobic co-digestion using linear regression method

Alkalinity is a reliable indicator of process stability in anaerobic digestion system.Total alkalinity(TA)and partial alkalinity(PA)are usually monitored offline as indicators for the status of anaerobic digestion process.In order to online monitor TA and PA,the linear regression method was used as estimator to predict alkalinity via software sensor method.Parameters,namely,pH,oxidation and reduction potential(ORP),and electrical conductivity(EC),were used as input variables.EC was the most significant parameter with TA and PA.Multiple linear regression(MLR)models and simple linear regression models with EC were constructed to predict TA and PA in anaerobic co-digestion system.On the basis of the evaluation of prediction accuracy,the applications of linear regression models were better for monitoring PA than TA.MLR models provided higher accuracy for alkalinity prediction than simple linear regression models.The two MLR models based on single-phase anaerobic digestion system were also feasible to predict TA in anaerobic co-digestion systems.However,the accuracy of these models should be improved by calibrating for broad applications of linear regression method in online alkalinity measurement.