Feed COD Research Articles

A dual-chamber Microbial Electrolysis Cell for electromethanosynthesis from the effluent of cheese whey dark fermentation

Dark fermentation of cheese whey (CW) for the production of biohydrogen generates an acidic effluent, containing high concentrations of volatile fatty acids, which needs to be further treated before disposal and possibly further valorised. This study develops a dual-chamber Microbial Electrolysis Cell (MEC) that achieves simultaneously the reduction of the organic content of this effluent to environmentally acceptable levels, along with bio-electrochemical reduction of CO2 to CH4. The MEC was operated for 140 days and the effect of the following conditions on the MEC performance was examined: (a) the feed concentration of the acidic fermentate (in the range 6–81 gCOD/L), (b) the conductivity of the feed modified via KCl addition (range 2–22 mS/cm), (c) the MEC operation mode (with or without catholyte renewal) and (d) the solids content (modified via CW filtration prior to its use). The results showed that high COD removal (>95 %) was achieved in all cases, along with a CH4 production of up to 1.1 mmol/gCODconsumed. The best performance of the cell was obtained for a feed COD concentration of ∼30 gCOD/L and a feed conductivity of ∼15 mS/cm; these conditions resulted in a COD removal exceeding 99 %, a CH4 production of 1.1 mmolCH4/gCODconsumed and a net energy production of 15.8 % compared to the energy demand of the system. The electrochemical study of the system revealed that higher and lower feed COD concentrations were characterized by higher internal resistances. The results indicate that the MEC can be exploited for further treatment and valorization of a high-strength effluent along with the production of CH4 with an energy surplus, as an efficient waste-to-energy technology.

The integration of low temperature supercritical water gasification with continuous in situ nano-catalyst synthesis for hydrogen generation from biomass wastewater

A continuous hydrothermal process is demonstrated, for the first time, that can operate at low gasification temperature (430 °C) and residence time (20 s) by combining supercritical water gasification (SCWG) and partial oxidation with in situ synthesis of virgin metal oxide nano-catalyst. Using olive wastewater as the feedstock, this gasification study experimentally investigated the impact of multiple variables: (1) COD feed concentration, (2) the in situ synthesis of different metal oxide nano-catalysts, (3) the partial oxidation coefficient (ɳ) and (4) the nano-catalyst precursor solution concentration. The optimum conditions for the generation of hydrogen and methane from olive wastewater were a feed COD of 38.6 g/L, ɳ = 0.8, and 60 mM precursor concentration for the in situ synthesis of Fe2O3 nano-catalyst. These optimised conditions were further investigated using spent lees and stillage. The efficiency of hydrogen and methane yields and COD reduction were in the order of stillage > spent lees > olive wastewater. The highest hydrogen molar selectivity, hydrogen and methane yields at 18.8 %, 17 and 11.4 mol/(kg biomass) respectively were obtained with stillage feedstock. Gasification, COD and TOC reduction efficiencies were 68.8–71.7 %, 72.6–76.5 % and 53.9–55.7 % respectively, with this process. Importantly, this novel gasification approach prevents any performance drop or catalyst deactivation during continuous operation. This study exemplifies that the co-generation of catalyst during SCWG is a promising and economically feasible direction for large-scale continuous generation of hydrogen and methane from different types of biomass wastewater at < 450 °C, whilst lowering its COD and TOC. (249 words)

A new UV-grafted photocatalytic membrane for advanced treatment of biologically treated baker’s yeast (BTY) effluent: Fabrication, characterization and performance evaluation

In this study, a superior hydrophilic polyethersulfone (PES) membrane modified with L-Lysine (C, N codoped)-TiO2/WO3 (LTW) photocatalyst is presented to endow self-antifouling properties and amelioration of the membrane performance in versatile wastewater treatment. ATR-FTIR spectra, FESEM, 3D AFM images, and water contact angle (WCA) measurement indicated that successful connection of LTW photocatalyst on PES membrane surface led to improved membrane properties like hydrophilicity and surface roughness. The PES/LTW membranes demonstrated significant enhancement in water permeability (49.79 L/m2.h) and antifouling feature (flux recovery rate (FRR) of 96.96 %). The optimal membrane (M-2, 0.03 wt%) with the highest hydrophilicity, pure water flux (PWF), and fouling resistance, was used to evaluate the filtration performance in a cross-flow setup. Response surface methodology (RSM) was utilized to model and optimize the filtration process. The effects of three influential variables, including operating pressure (P, 3–5 bar), feed COD concentration (C, 500–1500 mg/l), and effect of irradiation on four responses, i.e., flux (L/m2.h), FRR (%), dye removal efficiency (%), and COD removal efficiency (%) were assessed in a continuous regime using nanofiltration of biologically treated baker's yeast (BTY) effluent. The optimum conditions were found to be 693 mg/l of feed COD concentration and 4.44 bar of operating pressure under visible light irradiation. The experimental data compared to the predicted ones indicated a good agreement that confirms the validity of the models describing the performance of the photocatalytic membrane.

The effect of heat pre-treatment on the anaerobic digestion of high-solid pig manure under high organic loading level.

Since more and more large-scale farms appear in China and changes in fecal sewage source disposal, the production of high-concentration solid manure waste is also increasing, and its conversion and utilization are gaining attention. This study investigated the effect of heat pre-treatment (HPT) on the thermophilic anaerobic digestion (AD) of high-solid manure (HSM). Pig manure (PM) feed with a total solids of 13% was used for the HPT and subsequent anaerobic digestion (AD) test. The HPT was carried out at 60°C, 80°C, and 100°C, respectively, for 15min after the heating reached the set temperature. The results show that HPT led to PM feed COD solubilization, observing a maximum increase of 24.57% after pretreated at 100°C, and the treated PM feed under this condition received the maximum methane production potential of 264.64 mL·g-1 VS in batch AD test, which was 28.76% higher than that of the untreated group. Another semi-continuous AD test explored the maximum volume biogas production rate (VBPR). It involves two organic loading rates (OLR) of 13.4 and 17.8g VSadded·L-1·d-1. The continuous test exhibited that all the HPT groups could produce biogas normally when the OLR increased to the high level, while the digester fed with untreated PM showed failure. The maximum VBPR of 4.71LL-1·d-1 was observed from PM feed after pre-treated at 100°C and running at the high OLR. This reveals that thermal treatment can weaken the impact of a larger volume of feed on the AD system. Energy balance analysis demonstrates that it is necessary to use a heat exchanger to reuse energy in the HPT process to reduce the amount of energy input. In this case, the energy input to energy output (E i /E o ) ranged from 0.34 to 0.55, which was much less than one, suggesting that biogas increment due to heat treatment can reasonably cover the energy consumption of the pre-treatment itself. Thus combining HPT and high-load anaerobic digestion of PM was suitable.

High Salinity Wastewater Treatment Study Using an Automated Pilot Combining Anaerobic and Aerobic Biofilm Processes

A 20-ft containerized biological pilot system consisting of both an anaerobic expended granular sludge bed (EGSB) and an aerobic biofilm continuous flow intermittent clean (CFIC®) system has been designed, constructed, and delivered onsite at a pharmaceutical wastewater producer for a wastewater treatment study. The pilot was operated for a total of 317 days, including 147 days of adaptive phase and 170 days of testing phase. A pilot adaptive phase feeding wastewater COD concentration from 2 to 50 g/L with salinity up to 16 g/L was carried out, achieving EGSB where COD removal reached over 80 to 95% at OLR up to 22 kg COD/m3·d. In the testing phase, with repressive practical wastewater, the EGSB can remove over 97% of feed COD (with up to 82% acetic acid) at an average 16.3 kg COD/m3·d. The high wastewater salinity at 20 g/L did not inhibit COD removal efficiency by the system. The complete system with EGSB and aerobic stage was very stable and removed over 90–97% of the total COD dependent on the wastewater composition. The pilot was demonstrated as a valuable tool because of its user-friendly nature with high automation level, as well as its high efficiency in treating specific wastewater under varying operational conditions. This study provides critical information for full-scale system design and offers training for the customer in handling a previously unfamiliar process in a confident manner.

Effect of Sludge Residence Time over Anaerobic Biodegradation of High Saline Biomass

Halophytes are unique in that they can thrive in a wide range of soil conditions, from normal to extremely saline. This has recently prompted researchers to consider using halophytes as a phytoremediation end-product as a source for biogas generation. Therefore, applying the anaerobic digestion process for halophytes may have the potential advantage in terms of efficient land utilization, soil remediation, and biogas production. Based on this, the anaerobic digestion efficiency of high saline biomass was investigated in continuous laboratory-scale anaerobic reactors at two different sludge residence times (SRT) of 40 and 80 days. Under mesophilic atmosphere, two reactors were operated, one reactor used organic substrate with 30 g-Na+.L-1 originating from sodium chloride whereas the other was operated with the presence of sodium bicarbonate and sodium sulfate. The salt-tolerant microorganism was gradually developed and the salt concentrations were selected based on the elemental analyses results of 30 species of wild halophyte plants taken from the saline-affected area of the Aral Sea in Uzbekistan during the early phase of the operation. For 40 and 80 days of SRT, respectively, 65.56 percent and 60.42 percent of the feed COD were converted into methane gas by the chloride system. However, only about 60% of the feed COD was converted into methane for bicarbonate, and the remaining fraction of gas was assigned to sulfide as a final product of increased sulfate reduction bacteria activity. These findings showed that the salt-tolerant microorganism could be incubated and the anaerobic digestion process could be adapted for a high-saline substrate, implying that the biodegradability of phytoremediation end-products may be used for methane production.

Enhancing stability of aerobic granules by microbial selection pressure using height-adjustable influent strategy

Optimizing granules size distribution is critical for both reactor performance and stability. In this research, an optimal size range of 1800 to 3000 μm was proposed regarding mass transfer and granules stability based on granules developed at DO around 8.0 mg L−1 with the feed COD:N:P at 100:5:1. A height-adjustable influent strategy was applied to facilitate the nutrient storage of granules at optimum size range via microbial selective pressure. Results suggested insufficient hydraulic shear stress led to overgrowth of granules size. High abundance of filamentous bacteria (Thiothrix sp.) was observed in oversized granules, which detached and affected the remaining granules, resulting in severe sludge bulking. Strong hydraulic shear stress suppressed uncontrolled growth of granules. However, fewer abundance of simultaneous nitrification and denitrification (SND) bacterium was acquired, which led to unfavored SND effect and total nitrogen (TN) removal efficiency. The height-adjustable influent strategy facilitated the poly-β-hydroxybutyrate (PHB) storage of granules at optimum size range, while limiting the overgrowth of granules size. Additionally, more than 87.51% of total granules situated in optimal sizes range, which led to higher abundance of SND bacterium and higher TN removal efficiency.

Hydrogen production by supercritical water gasification of black liquor: Use of high temperatures and short residence times in a continuous reactor

The Supercritical Water Gasification (SCWG) of black liquor (BL) to obtain hydrogen and dispose of organic waste simultaneously has been studied in a continuous reactor employing short residence times. The experiments were conducted at 600–700 °C, with times between 24.5–29.1 s, at 23 MPa and feedstock was diluted to different concentration levels (0.81–2.43 wt.%). Furthermore, different NaOH concentrations (0–1.2 wt.%) were added to maintain a basic medium and avoid the polymerization of the compounds. Hydrogen production and COD removal was conducted with short residence times. The best results regarding hydrogen yield were achieved at 700 °C, 24.5 s residence time and 0.9 wt.% NaOH concentration, with a production of 38.68 mol H2/kgsample. In contrast, and regarding COD removal, the best results were obtained at 700 °C, with 24.5 s residence time and the highest feed COD concentration used (2.43 wt.%). The COD removal levels reached were between 65–90 %.

Self-cleaning properties of L-Histidine doped TiO2-CdS/PES nanocomposite membrane: Fabrication, characterization and performance

The polyethersulfone (PES) membrane incorporated with L-Histidine doped TiO2-CdS photocatalytic nanocomposite is fabricated to improve the membrane performance and its antifouling properties. The L-Histidine doped TiO2-CdS/PES nanofiltration membrane was characterized by scanning electron microscopy (SEM), contact angle and atomic force analysis (AFM) analyses. SEM images and contact angle results are demonstrated that membrane porosity and its hydrophilic properties increase with adding of L-Histidine doped TiO2-CdS photocatalytic nanocomposite. Moreover, AFM images of the modified membranes indicate favorable changes in surface roughness resulting in the improvement of antifouling properties. The pure water flux, flux recovery ratio (FRR) during filtration of milk powder and activated sludge suspension were also measured in a dead end cell. Increasing membrane permeability and FRR value approved its effective role of the added nanoparticles into the PES matrix. The M3 (0.5 wt% of NPs) membrane is selected as an optimal nanocomposite membrane which exhibits a much higher pure water flux (42.1 kg/m2 h) and FRR value (90 and 97% during filtration of milk powder and activated sludge suspension, respectively). The photocatalytic capability and antifouling properties of the M3 membrane as an optimum membrane were also investigated in a cross flow cell under continuous visible light irradiation. As a result, the high permeation flux (34.7 kg/m2 h), COD removal (100%) and FRR value (99%) was achieved during filtration of biologically treated palm oil mill effluent (POME) with COD concentration of 1000 mg/L at feed flow rate of 150 L/h and pressure of 5 bar. Effect of feed flow rate (50 and 150 L/h) and COD concentration (1000, 3000 and 5000 mg/L) on the membrane performance and its fouling resistance was also evaluated. Increasing feed concentration shows a negative effect on the membrane performance while feed flow rate increases separation performance and self-cleaning properties of the M3 membrane.

Optimization of sulfide‐based autotrophic denitrification process in an anaerobic baffled reactor

AbstractBACKGROUNDHigh SO42‐, COD, and nitrogen‐containing wastewater treatment requires different bacterial groups and environmental conditions, which can be achieved by sequential separate processes. This study examined the simultaneous removal of SO42‐, COD and nitrogen in a four‐compartment ABR, which allowed enrichment of different group of bacteria in each compartment. Feed COD and SO42‐ concentrations were kept constant at 1200 and 1500 mg L‐1, corresponding to COD/SO4‐2 ratio of 0.8. Initially, ABR was tested at varying influent ammonium concentrations (25–1500 mg NH4+‐N/L). Further, the third compartment of ABR was supplemented with nitrate under varying loading rates (60–300 mgNO3‐N L‐1 d‐1) for autotrophic denitrification with the sulfide produced in the previous compartments. This kind of application mimicked the internal recirculation of nitrate, which can be generated via nitrification of ABR effluent.RESULTSHigh sulfate reduction efficiencies (over 86%) were observed up to 1000 mg L‐1 NH4+‐N, however, 1500 mg L‐1 NH4+‐N caused decrease in reduction efficiency. Optimum nitrate loading rate was determined as 146 mgNO3‐N L‐1 d‐1 at molar N/S ratio of 0.42, corresponding with 100% nitrate, 83% sulfate, and 79% COD removals. Nitrate removal decreased at higher nitrate loadings and high sulfate generation arising from sulfide oxidation was observed.CONCLUSIONSulfate and COD removals together with efficient sulfide‐based autotrophic denitrification succeeded in a single reactor configuration at S/N ratio of 0.42. The developed process has the potential to be used in lab‐scale applications. © 2017 Society of Chemical Industry

Efficient high strength petrochemical wastewater treatment in a hybrid vertical anaerobic biofilm (HyVAB) reactor: a pilot study

Performance of a pilot scale Hybrid Vertical Anaerobic Biofilm (HyVAB) reactor treating petrochemical refinery wastewater is presented here. The reactor is an integration of a bottom anaerobic sludge bed and a top aerobic biofilm stage and was operated continuously for 92 days at 21 ± 2 °C. Wastewater was fed continuously to the reactor with step flow increases reducing hydraulic retention time from 55 to 12 hours, increasing organic loading rate from 3 to 33 kg-COD/m3·d. The HyVAB removed on average 91% and 86% of the soluble and total feed COD, respectively, at steady state and loads up to 23 kg-COD/m3·d, of which 98% of the soluble COD removal occurred in the anaerobic stage. Methane yield ranged from 0.29 to 0.51 L/g-COD removed, including conversion of settled aerobic sludge to methane. Sludge production was low (0.04 kg-VSS/kg-COD removed) and biogas methane content high (84 ± 2%). The results demonstrated that HyVAB is an efficient, low footprint alternative for high strength wastewater treatment.

Bio-Gasification Under Partially Aerated Conditions

Anaerobic digestion (AD) under mild aerobic loading is investigated. Aeration can apparently have both positive and negative impacts on biogas generation. This study aims to recognize and describe these different aeration effects on AD. Seven series of batch experiments (BT 1- 7) were conducted under varying feed and oxygenation conditions at 35 oC. Oxygen was introduced as headspace air in four of the batch experiments and as pure oxygen in two series. Effects of extensive initial aeration of inoculum were investigated in one batch series. The methane yield of the reactors fed with starch (1.09 g COD/LReactor) was positively influenced by oxygenation in the load range up to 38 % O2 (as % of feed COD). A negative influence of oxygen was observed at the next experimental level of 79 % O2. For the glucose fed reactors under similar operating conditions, the oxygen impact was near linearly negative in the tested range of 0 - 49 % O2. These results demonstrate that digestion of soluble substrates like glucose is not enhanced by O2, while substrates requiring hydrolysis are. Thus, limited aeration can enhance biogas production from non-soluble substrates under batch conditions. According to the experiment where the effects of extensive initial aeration was investigated, lengthening of the aeration period increasingly slowed down the gas generation rate but eventually resulted in the same methane yield. The lag period before gas generation started was three times longer for the aerated inoculum reactors than un-aerated. These observations suggest that oxygen induced inhibition of the biomass activity is mostly reversible. Reduced biogas production rates with initial aeration extent suggest some permanent damage to the anaerobes. Extensively aerated inoculums generated less methane compared to the un-aerated inoculum, probably due to the loss of some biogas potential initially present in the inoculum. Oxygen assisted degradation of some recalcitrant organic matter, including biomass cells themselves, present in the inoculum is also detected in an unfed inoculum test series.

Evaluation of energy-distribution of a hybrid microbial fuel cell–membrane bioreactor (MFC–MBR) for cost-effective wastewater treatment

A low-cost hybrid system integrating a membrane-less microbial fuel cell (MFC) with an anoxic/oxic membrane bioreactor (MBR) was studied for fouling mitigation. The appended electric field in the MBR was supplied by the MFC with continuous flow. Supernatant from an anaerobic reactor with low dissolved oxygen was used as feed to the MFC in order to enhance its performance compared with that fed with synthetic wastewater. The voltage output of MFC maintained at 0.52±0.02V with 1000Ω resister. The electric field intensity could reach to 0.114Vcm−1. Compared with the conventional MBR (CMBR), the contents rather than the components of foulants on the cake layer of fouled MFC–MBR system was significantly reduced. Although only 0.5% of the feed COD was translated into electricity and applied to MBR, the hybrid system showed great feasibility without additional consumption but extracting energy from waste water and significantly enhancing the membrane filterability.

Microbial conversion of synthetic and food waste-derived volatile fatty acids to lipids

Lipid accumulation in the oleaginous yeast Cryptococcus albidus was evaluated using mixtures of volatile fatty acids (VFA) as substrates. In general, batch growth under nitrogen limitation led to higher lipid accumulation using synthetic VFA. During batch growth, an initial COD:N ratio of 25:1mg COD:mg N led to maximum intracellular lipid accumulation (28.3±0.7% g/g dry cell weight), which is the maximum reported for C. albidus using VFA as the carbon source, without compromising growth kinetics. At this feed COD:N ratio, chemostat cultures fed with synthetic VFA yielded statistically similar intracellular lipid content as batch cultures (29.9±1.9%, g/g). However, batch cultures fed with VFA produced from the fermentation of food waste, yielded a lower lipid content (14.9±0.1%, g/g). The lipid composition obtained with synthetic and food-waste-derived VFA was similar to commercial biodiesel feedstock. We therefore demonstrate the feasibility of linking biochemical waste treatment and biofuel production using VFA as key intermediates.

Anaerobic co-digestion of biodiesel waste glycerin with municipal wastewater sludge: Microbial community structure dynamics and reactor performance

Two 10L completely mixed reactors operating at 37°C and 20days SRT were used to evaluate the relationships between reactor performance and microbial community dynamics during anaerobic co-digestion of biodiesel waste glycerin (BWG) with municipal wastewater sludge (MWS). The addition of up to 1.35% (v/v) BWG to reactor feeds yielded increased VS and COD removal together with enhanced the biogas production and methane yield. This represented 50% of the MWS feed COD. Pyrosequencing analysis showed Methanosaeta (acetoclastic) and Methanomicrobium (hydrogenotrophic) to be the methanogenic genera present in greatest diversity during stable reactor operation. Methanosaeta sequences predominated at the lowest BWG loading while those of Methanomicrobium were present in greatest abundance at the higher BWG loadings. Genus Candidatus cloacamonas was present in the greatest number of bacterial sequences at all loadings. Alkalinity, pH, biogas production and methane yield declined and VFA concentrations (especially propionate) increased during the highest BWG loading.

Anaerobic co‐digestion of dairy cattle slurry and agro‐industrial fats: Effect of fat ratio on the digester efficiency

AbstractThe objective of the study was to optimize the co‐digestion of cattle slurry in the presence of fats from the food industry. A laboratory pilot plant operating continuously was used for the experimental study. Tests were carried out with only cattle slurry and with different fat ratio (0, 10, 25, 45 and 60 %w/w of the feed COD as fats). In the case of using cattle slurry feed and OLR from 0.4 and 3.0 kg VS · m−3 · day−1 (HRT between 125 days and 19 days), methane productivity versus OLR exhibit a linear relation reflecting optimum biodegradability of the organic matter. For OLR above 3 kg VS · m−3 · day−1 (HRT less than 19 days), a break in the slope is observed expressing a decrease of the organic matter degradation rate. For HRT equal to 30 days, the results show that fat incorporation ratio lower than 25 %w/w does not affect the digester operation while maintaining acceptable biodegradability of the fat. In contrast, with a fat ratio of 60 %w/w, the system became unstable and a significant decrease in the methane productivity was observed, due to an accumulation of undegraded Long Chain Fatty Acids (LCFA). The conclusion is that the fat ratio must be controlled to avoid the destabilization of digestion, and finally operational conditions are proposed for co‐digestion.

Optimization of separate hydrogen and methane production from cassava wastewater using two-stage upflow anaerobic sludge blanket reactor (UASB) system under thermophilic operation

The objective of this study was to investigate the separate hydrogen and methane productions from cassava wastewater by using a two-stage upflow anaerobic sludge blanket (UASB) system under thermophilic operation. Recycle ratio of the effluent from methane bioreactor-to-feed flow rate was fixed at 1:1 and pH of hydrogen UASB unit was maintained at 5.5. At optimum COD loading rate of 90kg/m3d based on the feed COD load and hydrogen UASB volume, the produced gas from the hydrogen UASB unit mainly contained H2 and CO2 which provided the maximum hydrogen yield (54.22mlH2/g COD applied) and specific hydrogen production rate (197.17ml/gMLVSSd). At the same optimum COD loading rate, the produced gas from the methane UASB unit mainly contained CH4 and CO2 without H2 which were also consistent with the maximum methane yield (164.87mlCH4/g COD applied) and specific methane production rate (356.31mlCH4/gMLVSSd). The recycling operation minimized the use of NaOH for pH control in hydrogen UASB unit.

Study on Recycling Alkali from the Wastewater of Textile Mercerization Process by Nanofiltration

This study has researched the treatment ability of nanofiltration technology in printing and dyeing mercerization process alkali wastewater and investigated the effect of different pressures and alkalinities on membrane flux. The effect of different operating conditions on COD removal rate and alkali penetration rate has been also investigated in this study. The experimental results show that nanofiltration technology can remove the COD in printing and dyeing mercerization process wastewater effectively and the removal rate is above 80%. We conclude that the membrane flux tends to increase as the operating pressure increases, and decrease as the concentration of alkali in feed liquor and COD increases. The infiltration liquor through membrane can be satisfactorily reused by the method of concentration, and the final recovery efficiency of alkali by nanofiltration membrane treatment is above 90%.

Efficiency of the anaerobic digestion of amine wastes

Laboratory-scale anaerobic degradation of monoethanolamine waste (MEAw) with co-substrate organics was conducted at room temperature and organic loading rates from 0.19 to 5.03 kg COD/m3 day for 486 days in a hybrid digester. 90 % feed COD conversion to methane was obtained at the lower loads and only 45 % at the highest MEA waste/COD ratio (MEAwr) of 0.62 due to inhibition of methanogenesis. Inhibition at comparable loads decreased with time, implying that the culture adapted to the challenging feed. Methane yield was negatively correlated to MEAwr applied and inhibition avoided at MEAwr <0.5. Acetate accumulation implies inhibition of acetoclastic methanogenesis that can be caused by ammonia, a product of MEAw degradation. Moderate total ammonia nitrogen and free ammonia nitrogen accumulation, maximum 2.2 g N/l and 90 mg N/l, respectively suggests, however, that other components of MEAw, and/or degradation products of such, also inhibit methanogenesis, disturbing the digester performance.

Electricity generation from young landfill leachate in a microbial fuel cell with a new electrode material

This study aims at evaluating the performance of a two-chambered continuously fed microbial fuel cell with new Ti-TiO₂ electrodes for bioelectricity generation from young landfill leachate at varying strength of wastewater (1-50 COD g/L) and hydraulic retention time (HRT, 0.25-2 days). The COD removal efficiency in the MFC increased with time and reached 45 % at full-strength leachate (50 g/L COD) feeding. The current generation increased with increasing leachate strength and decreasing HRT up to organic loading rate of 100 g COD/L/day. The maximum current density throughout the study was 11 A/m² at HRT of 0.5 day and organic loading rate of 67 g COD/L/day. Coulombic efficiency (CE) decreased from 57 % at feed COD concentration of 1 g/L to less than 1 % when feed COD concentration was 50 g/L. Increase in OLR resulted in increase in power output but decrease in CE.