Effect Of Organic Loading Research Articles

Effect of organic loading on anaerobic digestion of cow dung: Methane production and kinetic study

Organic loading influences the effectiveness of producing biogas through anaerobic digestion. This study set out to investigate the effect of organic loading on the anaerobic mesophilic digestion of cow dung, the parameters involved in the digestion process and to evaluate the kinetics. Anaerobic digestion of cow dung at different organic loading (gVS/L) of 14 gVS/L, 18gVS/L, 22 gVS/L, 26 gVS/L and 30 gVS/L were investigated. Increasing the organic loading increased the methane yield of the cow dung. The highest cumulative methane yield was observed at 30 gVS/L with 63.42 mL CH4/gVS while the highest biogas yield was reported at 192.53 mL/gVS with the highest methane content of 89%. In addition, the modified Gompertz model equation with an R2 of 0.9980 demonstrated strong consistency and a good fit between predicted and experimental data. The high number of substrates added to the systems when increasing the organic loading increased the λ and slow down the nutrient transport and hydrolysis. This study provides current information on the effects of organic loading on the anaerobic digestion of cow dung in batch mode, including experimental conditions and operational parameters.

Effect of organic loading on bioelectricity generation potential of dual‐chambered microbial fuel cell treating chocolaterie wastewater

AbstractMicrobial fuel cells (MFC) are recent advancements in treating wastewater and generating power simultaneously. In the present study, chocolaterie wastewater rich in organic content was the substrate in a dual‐chambered MFC. Activated Carbon Fiber Felt (ACFF) electrodes (anode and cathode) were separated by Nafion 117 proton exchange membrane in the dual‐chambered reactor. The primary goal was to investigate the impact of organic loading on MFC efficiency in treating chocolaterie wastewater and carrying out microbial analysis. 1, 2, 3, and 4 gCOD/L were the organic loadings of the reactor. MFC performance increased till the optimum value, and after that, it declined. A total of 2 gCOD/L was the optimum organic loading. At this optimum organic loading, dual‐chambered MFC removed 79% of total chemical oxygen demand (TCOD), 70% of soluble chemical oxygen demand (SCOD), and 67% of total suspended solids (TSS). At 2 gCOD/L organic loading, the maximum power density was 99 mW/m2. Coulombic efficiency was 58% at 1 gCOD/L and 30% at 2 gCOD/L organic loadings. Microbial analysis revealed the presence of Ochrobactrum and Pseudomonas sp. as dominant exoelectrogens in the anodic biofilm. These species were proven for the contaminant degradation efficiency and potential for power generation. Hence dual‐chambered MFCs can treat high‐strength chocolaterie wastewaters efficiently at optimum operating conditions.

Dynamic alpha factors: Prediction in time and evolution along reactors

The performance of aeration – one of the most costly processes at water resource recovery facilities – is heavily impacted by actual wastewater characteristics which are commonly taken into account using the alpha factor (α). This factor varies depending on hydraulic and organic loading; such variance includes both time and spatial fluctuations. In standard design practice, it is often considered as a fixed number, or at best, a predefined time series. The objective of this paper is to propose a new method of predicting plantwide trends in the α factor through the use of process modelling which can accommodate diurnal and seasonal variations. The authors’ concept takes into account the dependence of α on sludge retention time in the form of degradation kinetics, the effects of organic loading (influent filtered COD), the presence or absence of anoxic zones, diffuser depth, and the impact of high MLSS found in certain, e.g., MBR, technologies. The developed model was calibrated using data from numerous facilities, relying on off-gas measurements and tests in clean and process water. Model validation was carried out against averaged α factor gradient data from one plant, and against diurnal air flow measurements from another. The Benchmark Simulation Model 1 configuration was used to demonstrate the applicability of the proposed model – in estimation of blower energy consumption and peak air flow requirements – comparing it with constant and scheduled α factor-based approaches.

Thermophilic Dark Fermentation of Olive Mill Wastewater in Batch Reactors: Effect of pH and Organic Loading

In recent decades, olive oil consumption has almost tripled worldwide. Olive oil production is linked with the production of enormous amounts of olive mill wastewater, the main by-product derived from three-phase olive mills. Due to the environmental risks of olive mill wastewater disposal, the management and valorization of the specific waste stream is of great importance. This work focuses on the thermophilic dark fermentation of olive mill wastewater in batch reactors, targeting pH optimization and the organic loading effect. A series of experiments were performed, during which the organic load of the substrate remained at 40 g/L after dilution with tap water, and the pH was tested in the range of 4.5 to 7.5. The maximum yield in terms of produced hydrogen was obtained at pH 6.0, and the yields were 0.7 mol H2/mol glucose or 0.5 L H2/Lreactor. At the same conditions, a reduction of 62% of the waste’s phenols was achieved. However, concerning the effect of organic loading at the optimized pH value (6.0), a further increase in the organic load minimized the hydrogen production, and the overall process was strongly inhibited.

Effect of organic loading on extracellular polymer secretion and phosphorus forms transformation in sludge

Effect of organic loading on extracellular polymer secretion and phosphorus forms transformation in sludge

Anaerobic mono-digestion of sugarcane trash and bagasse with and without pretreatment

The effect of organic loading on process performance and methane yields during anaerobic mono-digestion of sugarcane trash (ST) and sugarcane bagasse (SB) with and without dilute sulphuric acid impregnated steam explosion was investigated. At first, biochemical methane potential (BMP) of ST and SB was performed at 37 °C in batch assays with an inoculum to substrate (ISR) ratio of 2 on VS basis. Methane yields of 161.8 ± 4 and 187.9 ± 2.4 N mL g−1 VSadded were obtained for ST and SB, respectively. These yields were 55.6 and 53.8 % of the theoretical methane potentials for ST and SB respectively. Later, semi-continuous reactor experiments were conducted using four stainless steel reactors with working volume of 10 L and hydraulic retention time (HRT) of 35 d at 37 °C. Reactors were fed with untreated ST, untreated SB, steam exploded trash (TT) and steam exploded bagasse (TB). In all four reactors, methane production increased with increase in organic loading rate (OLR) from 1.5 to 2.5 gVS L-1 d-1. However, higher methane yields were noticed in TT (226 ± 37 NmL g-1VSfed) and TB (236 ± 22 NmL g-1VSfed) than for ST (121 ± 24 mL g-1VSfed) and SB (148 ± 25 mL g-1VSfed). Increase in OLR from 2.5 to 3.5 gVS L-1d-1 resulted in decreased methane yields and pseudo state stable conditions. Thus, steam explosion with dilute H2SO4 catalyst can improve the methane yields of both ST and SB.

Effect of organic loading on phosphorus forms transformation and microbial community in continuous-flow A2/O process.

A continuous-flow Anaerobic/Anoxic/Oxic (A2/O) system was operated at different organic concentrations to systematically investigate the effect on the nutrient removal, secretion characteristics of extracellular polymer, phosphorus forms transformation and changes in functional flora in this system. The results showed that high organic loading was more conducive to promote the secretion of extracellular polymeric substance (EPS), the increase of polysaccharide content was more obvious compared with protein, the impact of organic loading on the components of loosely bound EPS (LB-EPS) was higher than that of tight-bound EPS (TB-EPS). Phosphorus in sludge floc mainly existed in the form of inorganic phosphorus (IP), and IP mainly existed in the form of apatite inorganic phosphorus (AP). High organic load showed higher phosphorus storage in EPS, and the phosphorus content in EPS was positively correlated with the content of EPS. Non-apatite phosphorus (NAIP) content played an important role in the extracellular dephosphorization. The abundance of Nitrosomonas and Nitrospira responsible for nitrification decreased with the increase in organic loading. The group of denitrifiers was large, and Azospira was the most abundant genus among them. Dechloromonas, Acinetobacter, Povalibacter, Chryseolinea and Pirellula were the functional genera closely associated with phosphorus removal.

Effects of organic loading on bioelectricity and micro-algal biomass production in microbial fuel cells using synthetic wastewater

This study optimizes the performances of photosynthetic microbial fuel cells (PMFCs) under mixotrophic conditions in a cathode chamber inoculated with Chlorella vulgaris, compared to autotrophic conditions. In mixotrophic cultivation, microalgae in the cathode chamber were provided with organic and inorganic carbon. Different chemical oxygen demand (COD) concentrations of 100, 300, and 500 mg L−1 were added in the cathode chamber of PMFCs. The COD concentration in the anode chambers was maintained at 1000 mg L−1 and 1500 mg L−1 in the Batch 1, and 2, respectively. The mixotrophic PMFC with 100 mg L−1 of COD in the cathode chamber showed a longer power generation period with power densities of 3.93 (± 0.74) and 9.07 (± 1.40) mW m-2 in Batch 1 and 2, respectively. In comparison, the PMFC in autotrophic conditions showed lower power generation, and higher internal resistance. However, increasing the COD concentration more than 100 mg L−1, decreased the power generation period due to the favorable conditions for heterotrophic metabolism of microalgae. The algal biomass generation in the cathode chamber was highest at 300 mg L−1 of COD. The highest ammonium nitrogen removal efficiencies (92 % and 82 % in Batches 1 and 2, respectively) were obtained when the cathode chamber was enriched with 300 mg L−1 of COD. This study successfully demonstrated that PMFC performances can be increased in terms of power generation and biomass production under the mixotrophic cultivation of Chlorella vulgaris.

The effect of organic loading, protein and carbohydrate on biohydrogen production from soft shell of red pistachio, sugar beet pulp, and olive pulp cake

ABSTRACT The production of hydrogen by dark fermentation from biomass sources is important for renewable energy sources. In this study, the effect of total protein, total carbohydrate, and biomass loading in the biological hydrogen production were investigated, and soft shell of red pistachio (SRP), sugar beet pulp (SBP), and olive pulp cake (OPC) were used as sources of biomass. The highest hydrogen yields among these three biomasses were measured as 1.63 mg/g or 19.87 mg/l the 50 g/L concentration of SBP. The amount of protein in the production of biohydrogen has been determined to be an important factor and the increase in protein has decreased gas efficiency. The highest hydrogen gas efficiencies for SRP and OPC loadings on different organic loading concentrations were, respectively, measured as 0.3 mg/g or 3.6 ml/g. Hydrogen gas efficiency obtained for SBP with the highest carbohydrate quantity was calculated as 1.63 mg/g or 19.87 mg/l. As carbohydrate concentrations of the biomass resources used have increased, the efficiency of bio-hydrogen has also increased.

Comparative assessment of single-stage and two-stage anaerobic digestion for biogas production from high moisture municipal solid waste.

BackgroundAnaerobic digestion (AD) is a suitable process for treating high moisture MSW with biogas and biofertilizer production. However, the low stability of AD performance and low methane production results from high moisture MSW due to the fast acidify of carbohydrate fermentation. The effects of organic loading and incineration fly ash addition as a pH adjustment on methane production from high moisture MSW in the single-stage AD and two-stage AD processes were investigated.ResultsSuitable initial organic loading of the single-stage AD process was 17 gVS L−1 at incineration fly ash (IFA) addition of 0.5% with methane yield of 287 mL CH4 g−1 VS. Suitable initial organic loading of the two-stage AD process was 43 gVS L−1 at IFA addition of 1% with hydrogen and methane yield of 47.4 ml H2 g−1 VS and 363 mL CH4 g−1 VS, respectively. The highest hydrogen and methane production of 8.7 m3 H2 ton−1 of high moisture MSW and 66.6 m3 CH4 ton−1 of high moisture MSW was achieved at organic loading of 43 gVS L−1 at IFA addition of 1% by two-stage AD process. Biogas production by the two-stage AD process enabled 18.5% higher energy recovery than single-stage AD. The 1% addition of IFA into high moisture MSW was useful for controlling pH of the two-stage AD process with enhanced biogas production between 87–92% when compared to without IFA addition. Electricity production and energy recovery from MSW using the coupled incineration with biogas production by two-stage AD process were 9,874 MJ ton−1 MSW and 89%, respectively.ConclusionsThe two-stage AD process with IFA addition for pH adjustment could improve biogas production from high moisture MSW, as well as reduce lag phase and enhance biodegradability efficiency. The coupled incineration process with biogas production using the two-stage AD process was suitable for the management of MSW with low area requirement, low greenhouse gas emissions, and high energy recovery.

Remediation of nitrogen polluted water using Fe–C microelectrolysis and biofiltration under mixotrophic conditions

A hybrid biofilter was established on Fe–C supported carriers aimed to enhance nitrogen removal from polluted water of low Carbon/Nitrogen (C/N) ratio. Effects of organic loadings, hydraulic retention time (HRT), additional electron donor (Fe2+) supplementation and operation mode on the performance of the biofilter were investigated. Results showed that up-flow operation mode was better than down-flow mode in terms of nitrate and total nitrogen (TN) removal at low COD/N. The average removal of NO3−-N, NH4+ –N and TN attained 83.1%, 84.7% and 81.2%, respectively, under the conditions of influent COD/NO3−-N = 1.5–3.6, HRT = 10 h and up-flow operation. When the biofilter was operated under autotrophic conditions without organic compounds in influent as electron donors, the biofilter achieved a NO3−-N removal of 46% and TN removal of 56% depending on the innate electron donors provided by the Fe–C carriers. Supplementation of Fe2+ in influent further promoted autotrophic denitrifying process, and the removal of NO3−-N and TN increased to 96.3% and 84.7%, respectively, at the mol ratio of Fe2+/NO3− = 10 and HRT = 10 h. The microbial community was analyzed for the biofilm samples enriched under heterotrophic and autotrophic conditions. The Fe–C biofilter boosted the growth of a large population of mixotrophic denitrifying bacteria including Gallionella, heterotrophic denitrifying bacteria Denitratisoma, and autotrophic denitrifying bacteria Thiobacillus and Thioalkalispira. On the whole, the biofilter coupled with Fe–C micro-electrolysis provides a novel strategy to treat polluted water of low C/N under both heterotrophic and autotrophic conditions.

On the evaluation of filtered and pretreated cheese whey as an electron donor in a single chamber microbial fuel cell

In the present study, the valorization of cheese whey (CW) as an electron donor in an air-cathode single-chamber microbial fuel cell (MFC) was studied. Filter-sterilized raw and pretreated-acidified diluted CW (after 48 h of fermentation at mesophilic temperature) were used as substrates, in order to investigate the effect of the two different handlings on the MFC performance. The pretreatment-acidification experiments were performed under different operational conditions (initial dilutions giving chemical oxygen demand (COD) concentrations of 2 and 4 g/L as well as initial pH adjusted to 6.7 and without pH adjustment) in order to obtain maximum acidification efficiency and energy recovery, in the form of hydrogen. The effect of organic load on the efficiency of the MFC was studied, aiming at exploring the possibility of achieving a successful operation at the highest possible initial concentration of CW (smallest dilution). The experimental results showed that CW is a suitable and promising substrate for electricity production using MFC, with a maximum power density of 3.26 W/m3 (0.33 MJ/kg COD) for filter-sterilized CW diluted to an initial concentration of 0.8 g COD/L. Combining MFC technology with the pretreatment/acidification process, during which hydrogen is also produced, a total energy of 2.37 MJ/kg COD could be recovered.

Effect of organic loading, feed-to-inoculum ratio, and pretreatment on the anaerobic digestion of tobacco stalks

This work firstly investigated the suitable organic loading (OL) and feed to inoculum (F/I) ratio of three kinds of tobacco stalks (TS116, TS99, and TS85) during anaerobic digestion (AD) via response surface methodology (RSM). The highest experimental methane yield (EMY) of 148.1 mL/g VS was achieved from TS116 at OL of 20.2 g VS/L and F/I ratio of 1.1. To further increase EMY, various pretreatments including alkaline hydrogen peroxide (AHP), NaOH, KOH, Ca(OH)2, HCl, and oxalic acid (H2C2O4) were implemented on TS116. Results showed that AHP was most effective, and the maximal EMY of 350.7 mL/g VS and biodegradability (Bd) of 81.4% were obtained from 7% AHP pretreated TS116, which increased by 105.6% than untreated. XRD, FTIR, and SEM analyses evidenced that the structure of AHP pretreated TS116 was strongly disrupted. This study lays the foundation for applying this waste into AD in future applications.

Effect of inoculum type and organic loading on biogas production of sunflower meal and wheat straw

Inoculum plays a vital role in providing initial microbial population in anaerobic process. There is unavailability of standard inoculum in the Pakistan and the available inoculum requires pretreatment and preparation before use. Thus, in this study the effect of inoculum type and organic loading (OL) on the biogas yield of sunflower meal and wheat straw was evaluated. For this purpose, lab scale batch experiments were conducted at OL of 2 g VS L− 1 in 225 mL glass bottle using digested manure, acclimatized sludge and septic tank sludge as inoculum. The highest biogas yield and volatile solids reduction of 768 NmL g− 1 VS and 78%, respectively, were observed from sunflower meal with digested manure. Reactor inoculated with digested manure also showed better buffering capacity in terms of pH. The inoculum selected from first experiment was used to study the effect of OL (2, 6, 10 and 14 g VS L− 1) on biogas yield. Results showed that biogas yield decreased with the increased in OL. Stability parameters revealed that reactors can be operated safely up to OL of 10 g VS L− 1. Biogas production data were modelled by modified Gompertz function.

Psychrophilic anaerobic dynamic membrane bioreactor for domestic wastewater treatment: Effects of organic loading and sludge recycling

Two upflow anaerobic dynamic membrane bioreactors (AnDMBRs) with and without sludge recycling were operated in parallel at varied organic loadings and psychrophilic temperature for domestic wastewater treatment. A 75 μm nylon mesh, used as a supporting material, enabled quick and stable dynamic membrane formation. The AnDMBRs could operate continuously without relaxation at a high flux rate of 22.5 L/m2h; however, high organic loading accelerated the increasing rate of trans-membrane pressure (TMP). High chemical oxygen demand removal was achieved in both AnDMBRs with removal efficiencies of 70–90%. Sludge recycling enhanced the cross-flow velocity but negatively affected the effluent turbidity, sludge properties (particle size reduction and biopolymer release) and dynamic membrane filterability. Although increased organic loading enhanced biogas yield, the low biogas production was related to the dissolved methane loss in the effluent. Easy-operation, minimal maintenance and low-energy consumption makes the AnDMBR process cost-effective for practical wastewater treatment in temperate areas.

Performance of the hybrid growth sequencing batch reactor (HG-SBR) for biodegradation of phenol under various toxicity conditions

Hybrid growth microorganisms in sequencing batch reactors have proven effective for treating the toxic compound phenol, but the toxicity effect under different toxicity conditions has rarely been discussed. Therefore, the performance of the HG-SBR under toxic, acute and chronic organic loading can provide the overall operating conditions of the system. Toxic organic loading (TOL) was monitored during the first 7hr while introducing 50mg/L phenol to the system. The system was adversely affected with the sudden introduction of phenol to the virgin activated sludge, which caused a low degradation rate and high dissolved oxygen consumption during TOL. Acute organic loading (AOL) had significant effects at high phenol concentrations (600, 800 1000mg/L). The specific oxygen uptake rate (SOUR) gradually decreased to 4.9mg O2/(g MLVSS·hr) at 1000mg/L of phenol compared to 12.74mg O2/(g MLVSS·hr) for 200mg/L of phenol. The HG-SBR was further monitored during chronic organic loading (COL) over 67days. The effects of organic loading were more apparent at 800mg/L and 1000mg/L phenol concentrations, as the removal range was between 22%–30% and 18%–46% respectively, which indicated the severe effects of COL.

AnSBBR applied to biomethane production for vinasse treatment: effects of organic loading, feed strategy and temperature

Abstract This study assessed the feasibility of an anaerobic sequencing batch and fed-batch biofilm reactor (AnSBBR) with mechanical stirring for vinasse treatment and biomethane production. The amount of liquid medium used was 3 L, and the treated volume was 1 L per cycle. The cycle time was 8 h, with feeding times of 10 min (batch mode) and 240 min (fed-batch mode). Methane productivity increased with the increase in organic load from 1.0 to 10.0 gCOD.L-1.d-1. The maximum molar productivity and yield of methane were 123.4 molCH4.m-3.d-1 and 13.8 mmolCH4.gCOD-1 (88% of the theoretical), respectively. These parameters were lower in fed-batch mode than in batch mode and were lower at 45°C than at 30°C due to biomass adaptation. In general, the values of the kinetic parameters increased with organic load and were similar for the batch and fed-batch modes. Therefore, the increase in organic load positively influenced the process by increased COD removal and lower volatile acids accumulation as the load increased. The batch mode performed better than did the fed-batch mode and 30°C was more suitable than 45°C to produce methane under the studied conditions.

Potential of Cinnamon Oil Emulsions as Alternative Washing Solutions of Carrots

The objective of this study was to evaluate the potential of cinnamon oil emulsions as alternative washing solutions to improve the microbial safety of carrots. Whey protein concentrate (WPC), gum arabic (GA), lecithin, and their combinations were used to prepare cinnamon oil emulsions. The emulsions were characterized for their hydrodynamic diameter (Dh) during 7 days of storage and their antimicrobial activity against cocktails of Salmonella enterica , Escherichia coli O157:H7, and Listeria monocytogenes . The Dh of the emulsion prepared with the GA+WPC blend did not change significantly (195.0 to 184.1 nm), whereas all other emulsions showed varying degrees of increases in Dh. Compared with free cinnamon oil dissolved in 5% ethanol, all emulsions showed similar or lower MICs and MBCs. Emulsions prepared with GA and equal masses of GA and WPC were chosen and diluted to 0.2 and 0.5% cinnamon oil to wash carrots that were surface inoculated with bacterial cocktails because of their lower MICs and MBCs than free oil. Emulsions resulted in significantly higher reductions of pathogens on carrots than free cinnamon oil, 3.0 to 3.7 versus 2.1 to 2.3 log CFU/g at 0.5% cinnamon oil and 2.0 to 3.0 versus 1.0 to 1.7 log CFU/g at 0.2% cinnamon oil. No transfer of bacteria from inoculated carrots to wash solutions and no effects of organic load on log reductions were only observed for wash treatments with 0.5% emulsified cinnamon oil. Thus, the cinnamon oil emulsions are potential alternative postharvest washing solutions for fresh produce production.

Dominance of candidate Saccharibacteria in a membrane bioreactor treating medium age landfill leachate: Effects of organic load on microbial communities, hydrolytic potential and extracellular polymeric substances

A membrane bioreactor (MBR), accomplishing high nitrogen removal efficiencies, was evaluated under various landfill leachate concentrations (50, 75 and 100% v/v). Proteinous and carbohydrate extracellular polymeric substances (EPS) and soluble microbial product (SMP) were strongly correlated (p<0.01) with organic load, salinity and NH4+-N. Exceptionally high β-glucosidase activities (6700–10,100Ug−1) were determined during MBR operation with 50% v/v leachate, as a result of the low organic carbon availability that extendedly induced β-glucosidases to breakdown the least biodegradable organic fraction. Illumina sequencing revealed that candidate Saccharibacteria were dominant, independently of the leachate concentration applied, whereas other microbiota (21.2% of total reads) disappeared when undiluted leachate was used. Fungal taxa shifted from a Saccharomyces- to a newly-described Cryptomycota-based community with increasing leachate concentration. Indeed, this is the first report on the dominance of candidate Saccharibacteria and on the examination of their metabolic behavior in a bioreactor treating real wastewater.

Production of Bio-Based Hydrogen Enriched Methane from Waste Glycerol in a Two Stage Continuous System

In the present work, a continuous process was developed aiming at the production of bio-based hydrogen-enriched methane, from waste glycerol (WG) in a two-stage reactor system. In the first step, biohydrogen production was studied, using an attached mixed acidogenic consortium in an up-flow column bioreactor. Cylindrical porous ceramic beads with a surface area of 600 m2L−1 were used as attachment matrix of bacterial cells. The hydrogen yield, the substrate consumption and the distribution of soluble metabolites were investigated for two different substrate concentrations in the feed, i.e. 20 and 25 g WG/L. SEM pictures of the biofilm formed on the ceramic beads revealed that bacilli dominated in the reactor. Subsequently, RISA methodology showed that Klebsiella sp. and Clostridium sp. were among the dominant microorganisms. In parallel, a methanogenic reactor was started up and operated in continuous mode using initially commercial glycerol, and subsequently WG as carbon sources. In the sequel, the effluent of the hydrogenic reactor was fed to the methanogenic reactor (constituting thus the second stage in a two-stage process), and the effect of organic loading on the methane yield was studied. It was shown that the reactor managed to generate up to 73 % of the theoretically expected methane based on COD removal, corresponding to 256.0 ± 2.6 L CH4/kg WG. Moreover, simulation of the experimental data of the methanogenic reactor via the Anaerobic Digestion Model ADM1 revealed that the model was able to successfully describe the performance of the digester, even under dynamic conditions.