Inoculation Of Sludge Research Articles

Analysis of organic compounds’ degradation and electricity generation in anaerobic fluidized bed microbial fuel cell for coking wastewater treatment

ABSTRACTA single-chambered packing-type anaerobic fluidized microbial fuel cell (AFBMFC) with coking wastewater (CWW) as fuel was built to treat CWW, which not only has high treating efficiency, but also can convert organic matter in wastewater into electricity. AFBMFC was constructed by using anaerobic sludge that was domesticated as inoculation sludge, which was used to biochemically treat CWW. The organic compounds in CWW were extracted by liquid–liquid extraction step by step every day. The extraction phase was concentrated by a rotary evaporator and a nitrogen sweeping device and was analyzed by GC–MS. And the electricity-generation performances of AFBMFC were investigated. The results show that the composition of CWW was complicated, which mainly contains hydrocarbons, phenols, nitrogenous organic compounds, alcohols and aldehydes, esters and acids and so on. After a cycle of anaerobic biochemical treatment, the content of organic compounds in the effluent decreased significantly. After the treatment of AFBMFC, 99.9% phenols, 98.4% alcohol and aldehydes and 95.3% nitrogenous compounds were biodegraded. In the effluent, some new compounds (such as tricosane and dibutyl phthalate) were produced. The chemical oxygen demand (COD) of CWW decreased from 3372 to 559 mg/L in the closed-circuit microbial fuel cell, and the COD removal was 83.4 ± 1.0%. The maximum power density of AFBMFC was 2.13 ± 0.01 mW m−2.

The Response of Biogas Production and Methanogenic Community to the Variation of Intermediate Vfas Produced During the Anaerobic Digestionof Food Waste

This study focused on the effect of the variation of intermediate volatile fatty acids (VFAs) caused by the change of organic load on methane production and methanogenic community shift during anaerobic digestion (AD). Eight groups with different F/I (VSfood wastes:VSsludge) were conducted, while the inoculation sludge had a same amount. Operational performance for every groups was monitored by assessing biological activity, methane production, concentration of VFAs. The major intermediate VFAs of anaerobic digestion were acetate, propionate, iso-butyrate, n-butyrate, n-valerate and iso-valerate; and acetate and n-butyrate were the most abundant components. The increasing of F/I changed the predominant VFAs type from acetic acid to n-butyric acid, while the total VFAs concentration increased. Besides, the methane production increased and then decreased, and reached the maximum (170.3 ml/g added VS-1) at F/I of 1. The methanogenic diversity was screened using the high-throughput sequencing, which shown VFAs had a significant impact on the archaeal community as the dominant archaea shifted from Methano bacterium to Methano sarcina.

Electricity Production and Characterization of High-Strength Industrial Wastewaters in Microbial Fuel Cell.

Microbial fuel cells (MFCs) convert electrochemical energy into electrical energy immediately and have a big potential usage for the same time wastewater treatment and energy recovery via electro-active microorganisms. However, MFCs must be efficiently optimized due to its limitations such as high cost and low power production. Finding new materials to increase the cell performance and reduce cost for MFC anodes is mandatory. In the first step of this study, different inoculation sludges such as anaerobic gum industry wastewater, anaerobic brewery wastewater and anaerobic phosphate were tested, and MFC that was set up with anaerobic gum industry wastewater inoculation sludge exhibited the highest performance. In the second step of this study, various wastewaters such as chocolate industry, gum industry and slaughterhouse industry were investigated for anode bacteria sources. Several electrochemical techniques have been employed to elucidate how wastewaters affect the MFCs' performance. Among all the mentioned wastewaters, the best performance was achieved by the MFCs fed with slaughterhouse wastewater; this device produced a maximum power density of 267mW·m-2.

Nitrifying–denitrifying filters and UV-C disinfection reactor: a combined system for wastewater treatment

ABSTRACTBiological treatment systems use the natural processes of ubiquitous organisms to remove pollutants and improve the water quality before discharge to the environment. In this paper, the nitrification/denitrification reactor allowed a reduction in organic load, but offered a weak efficiency in nitrate reduction. However, the additions of the activated sludge in the reactor improve this efficiency. A decrease of values from 13.3 to 8 mg/l was noted. Nevertheless, sludge inoculation led to a net increase of the number of pathogenic bacteria. For this reason, a UV-C pilot reactor was installed at the exit of the biological nitrification–denitrification device. Thus, a fluence of 50 mJ.cm-2 was sufficient to achieve values of 20 MPN/100 ml for fecal coliform and 6 MPN/100 ml for fecal streptococci, conforms to Tunisian Standards of Rejection. On the other hand, the DGGE approach has allowed a direct assessment of the bacterial community changes upon the treated wastewater.

Optimization of bio-drying of kitchen waste: inoculation, initial moisture content and bulking agents

Bio-drying has been proved to be a promising method for treatment of MSW (municipal solid waste) and sewage sludge due to its high energy efficiency and low operating cost. In this study, bio-drying was adopted to treat kitchen waste, which has quite different features from MSW and sewage sludge. The main operating factors of bio-drying, including sludge inoculation, initial moisture content, and different bulking agents, were systematically investigated. The trial with a high inoculation ratio showed a shorter lag phase and better temperature profile, thus resulting in a better drying performance with higher evaporation efficiency. Furthermore, 71.7 % of initial moisture content, which is relatively higher than the values reported in other studies, was found to be favorable for microbial activity, which could save the operating cost by reducing bulking agent in bio-drying of kitchen waste. Among the tested bulking agents (i.e., corncob, sawdust, and straw), straw was found to be the best in terms of better temperature profile and water removal efficiency due to its high water absorption capacity and the proper FAS. These results will provide some valuable information for efficient bio-drying of the kitchen waste.

The nitritation performance of biofilm reactor for treating domestic wastewater under high dissolved oxygen

The objective of this study was to investigate the nitritation performance in a biofilm reactor for treating domestic wastewater. The reactor was operated in continuous feed mode from phases 1 to 3. The dissolved oxygen (DO) was controlled at 3.5–7mg/L throughout the experiment. The biofilm reactor showed excellent nitritation performance after the inoculation of nitrifying sludge, with the hydraulic retention time being reduced from 24 to 7hr. Above 90% nitrite accumulation ratio (NAR) was maintained in phase 1. Afterwards, nitratation occurred with the low NH4+–N concentration in the reactor. The improvement of NH4+–N concentration to 20–35mg/L had a limited effect on the recovery of nitritation. However, nitritation recovered rapidly when sequencing batch feed mode was adopted in phase 4, with the effluent NH4+–N concentration above 7mg/L. The improvement of ammonia oxidizing bacteria (AOB) activity and the combined inhibition effect of free ammonia (FA) and free nitrous acid (FNA) on the nitrite oxidizing bacteria (NOB) were two key factors for the rapid recovery of nitritation. Sludge activity was obtained in batch tests. The results of batch tests had a good relationship with the long term operation performance of the biofilm reactor.

Advanced low carbon-to-nitrogen ratio wastewater treatment by electrochemical and biological coupling process.

Nitrogen pollution in ground and surface water significantly affects the environment and its organisms, thereby leading to an increasingly serious environmental problem. Such pollution is difficult to degrade because of the lack of carbon sources. Therefore, an electrochemical and biological coupling process (EBCP) was developed with a composite catalytic biological carrier (CCBC) and applied in a pilot-scale cylindrical reactor to treat wastewater with a carbon-to-nitrogen (C/N) ratio of 2. The startup process, coupling principle, and dynamic feature of the EBCP were examined along with the effects of hydraulic retention time (HRT), dissolved oxygen (DO), and initial pH on nitrogen removal. A stable coupling system was obtained after 51 days when plenty of biofilms were cultivated on the CCBC without inoculation sludge. Autotrophic denitrification, with [Fe(2+)] and [H] produced by iron-carbon galvanic cells in CCBC as electron donors, was confirmed by equity calculation of CODCr and nitrogen removal. Nitrogen removal efficiency was significantly influenced by HRT, DO, and initial pH with optimal values of 3.5 h, 3.5 ± 0.1 mg L(-1), and 7.5 ± 0.1, respectively. The ammonia, nitrate, and total nitrogen (TN) removal efficiencies of 90.1 to 95.3 %, 90.5 to 99.0 %, and 90.3 to 96.5 % were maintained with corresponding initial concentrations of 40 ± 2 mg L(-1) (NH3-N load of 0.27 ± 0.01 kg NH3-N m(-3) d(-1)), 20 ± 1 mg L(-1), and 60 ± 2 mg L(-1) (TN load of 0.41 ± 0.02 kg TN m(-3) d(-1)). Based on the Eckenfelder model, the kinetics equation of the nitrogen transformation along the reactor was N e = N 0 exp (-0.04368 h/L(1.8438)). Hence, EBCP is a viable method for advanced low C/N ratio wastewater treatment.

Effect of Wastewater Nitrification/Denitrification Treatment on Biofilm Expansion and Ammonia‐Oxidizing/Denitrifying Community

By considering its importance in biological wastewater treatment systems, biofilm formation over time and under activated sludge inoculation in a fixed biomass reactor was investigated. Experiments were conducted on a reactor composed of two successive PVC columns; a first gravel column and a second sandy one. The physico–chemical and bacteriological quality of treated water at the outlet of the biological reactor was tracked. Furthermore, a quantitative and qualitative study was made on the biofilm before and after addition of a carbon source. Thus, the attached volatile solid (AVS), exopolysaccharides (EPS), proteins (PN), and microbial DNA were quantified. The results showed that in the first column and at 80 and 168 cm depth, AVS and DNA were greater than those registered at 5 cm. A similar result was observed in the second column. Nevertheless, at the second sandy column and after sludge addition, the amounts of EPS and PN recorded at depth of 83 and 165 cm were smaller than those obtained at 5 and 10 cm of depth. On the other hand, the polymerase chain reaction‐denaturing gradient gel electrophoresis method coupled with sequence analysis was used to survey the diversity of ammonia‐oxidizing and denitrifying communities. The amoA gene sequencing showed that the majority of the ammonia‐oxidizing communities was affiliated to Nitrosomonas. With the second column sludge addition, the denitrifying community seems to be affected. A great diversity of denitrifying bacteria in 168 cm of depth was observed.

Nitrification of anaerobic digester effluent for nitrogen management at swine farms

Anaerobic digester effluent collected from a swine farm was nitrified in lab-scale bioreactors mimicking an innovative manure management system to understand factors relevant to a successful start-up. The effects of digester effluent strength, aeration time, nitrifying sludge inoculation, and initial pH control on the startup of the nitrification system were investigated. The results showed that initial NH4+-N concentrations higher than 800mgL−1 could severely inhibit the onset of nitrification if relying on native bacterial populations. When aeration time was increased from 4 to 12hd−1, ammonium oxidation occurred earlier, but nitrite oxidation was delayed. However, the delay was not observed when bioaugmentation with nitrifying sludge was conducted. Initial addition of acid for pH control was unsuccessful as initial depletion of alkalinity eventually resulted in self-inhibition of nitrification cause by decreasing pH over time. Overall, these results provide guidance on how to effectively start large-scale innovative animal waste treatment systems.

Mesophilic Anaerobic Digestion of Dairy Manure and Vegetable Waste Using Batch Reactor

Anaerobic digestion of single dairy manure, single vegetable waste, mixture of dairy manure and vegetable waste was conducted to produce biogas. Startup characteristic, leachate parameters and inoculation amount were investigated. The experimental results showed that anaerobic digestion can start up quickly with acclimated thickening sludge as inoculation sludge and 30% was appropriate inoculation percentage. Digestion of single dairy manure and mixture of dairy manure and vegetable waste appeared better buffering ability with higher alkalinity than single vegetable waste. Compared to single digestion of dairy manure or vegetable waste, mixture of dairy manure and vegetable waste is more suitable for anaerobic digestion. Under the conditions of TS=10% and T=(36±1)°C, cumulative biogas production of mixture of dairy manure and vegetable waste is 5281 mL during the period of 30 days and average daily gas production is about 176 mL. These results could provide theoretical data for practical biogas engineering.

Effects of Phosphate Fertilizer and Sewage Sludge Levels and Inoculation with Phosphate Dissolving Fungi on Growth and Absorption of Phosphor by Corn Plants (Zea myas L.)

Effects of Phosphate Fertilizer and Sewage Sludge Levels and Inoculation with Phosphate Dissolving Fungi on Growth and Absorption of Phosphor by Corn Plants (Zea myas L.)

Study of Anaerobic Digestion of Model Kitchen Waste

The characteristics such as pH, dry matter, carbon concentration, the total solid and volatile solid of kitchen wastes produced by a canteen in Guangzhou were measured. The anaerobic digestion process performances were evaluated through the examination of operational conditions like activated sludge inoculation, temperature on SS, biogas production, COD concentration and pH in the reactor. When the proportion between kitchen wastes to seed sludge inoculation was 1:1, the biogas production reached the peak at 45 °C. The kitchen waste pH decreased at the first four days then increased adversely after 4 days digestion, but COD concentration showed the opposite variation.

Start-Up of Anammox Process Using Municipal Sewage Sludge in One UASB Reactor

Using municipal sewage treatment plant sludge as the inoculation sludge, anaerobic ammonia oxidation experiment started in a UASB reactor with an effective volume of 3.5L. The experiment lasted 116d, experimental medium term, the system NH4+-N, NO2--N removal rates were above 50%. Changing influent load will cause a greater impact on the reactor, resulting in fluctuations of NH4+-N and NO2--N removal rate. Late, NO2--N / NH4+-N values ​​remain at around 1. The sludge in the reactor changed from gray-brown to pink. The system is more stable for removing NH4+-N and NO2--N.

The Harnessing Of Bioenergy From A Dual Chambered Microbial Fuel Cell (Mfc) Employing Sago-Processing Wastewater As Catholyte

The application of microbial fuel cell (MFC) for wastewater treatment is an emerging strategy for the simultaneous treatment of pollutants and generation of electricity. The feasibility of utilizing sago-processing wastewater as a catholyte and comparing it with synthetic catholyte was investigated using dual-chambered salt bridge MFCs. The wastewater catholyte was again varied as with and without sago sludge inoculation, and the effect of sludge addition on MFC performance was determined. Three dual-chambered salt bridge MFCs namely synthetic catholyte (MFC-SC), wastewater catholyte (MFC-WC), and Sludge inoculated wastewater catholyte (MFC-WS) were designed and their performance was compared. Synthetic catholyte was the best in power generation than the other two MFCs and it documented maximum open circuit voltage of 0.35 V and closed circuit voltage of 0.31 V. Sludge inoculated wastewater catholyte (MFC-WS) was better compared to wastewater catholyte (MFC-WC) in power generation with a maximum degradation in chemical oxygen demand of 80.4% and total removal of carbohydrates and starch. The attachment of bacteria on graphite electrode was observed using Scanning Electron Microscope (SEM). The results evidently demonstrated that wastewater catholyte can be a promising alternative to synthetic and chemical catholyte.

Experimental Study on the Start-Up Stage of Wheat Straw Pulp and Paper Wastewater Treatment in Immobilized and Suspended Biomass Combination Processing

The study on the start-up of the pilot-scale immobilized and suspended biomass combination processing to treat the comprehensive effluent from a wheat straw pulp and paper plant was performed. The carrier packing selected in this experiment is a new type of microbial carrier (modified polyurethane foam plastic packing) which dosing rate was 20% of the reactor volume. The low quantity of inoculation sludge way is used to start the system. The test results show that the removal efficiency of COD and SS by the immobilized and suspended biomass combination technology system after a weak or so can be stable, as the effluent SS was below 50mg/L, the removal rate of 95% or more and the effluent COD was below 260mg/L, the removal rate of 85% or more. From start to 10th day, the attached sludge concentration on biomass conversion was more than 20g/L, while the microscope observation to biological adherent microbes suspended sludge and carrier phase indicated abundant microbial species. The fact indicates that the start-up can be finished in 10 days.

Effect of [formula omitted] ratio and seed sludge on simultaneous methanogenesis and denitrification in intermittent organic solid waste treatment

The effect of the COD/NO3−–N ratio and seed sludges on methanogenesis and denitrification in intermittent organic waste treatment was investigated in a batch experiment. To evaluate the effects of denitrification sludge, two different experimental conditions were used: methanogenic sludge only conditions (M conditions) and methanogenic sludge plus denitrification sludge conditions (MD conditions). The experimental results showed that simultaneous methanogenesis and denitrification occurred at COD/NO3−–N ratio of 17.2 in the M conditions and 17.2 and 5.74 in the MD conditions. A relatively high denitrification efficiency (high nitrate removal rate and low N2O emission) and high methane production were achieved in the MD conditions, compared with the M conditions. The inoculation of denitrification sludge with methanogenic sludge appeared to enhance denitrification activity, resulting in the recovery of the methanogenesis activity. The performance of simultaneous methanogenesis and denitrification was affected by the COD/NO3−–N ratio in the batch reactor, rather than the COD/NO3−–N ratio of the substrate itself. The solubilization rate should also be considered when conducting simultaneous methanogenesis and denitrification in organic solid waste treatment.

Influence of process parameters on anaerobic biodegradation of DDT in contami-nated soil. Preliminary lab-scale study. Part II. Substrates and pH control

Suitability of various substrates for anaerobic biodegradation of DDT in contaminated soil was tested in lab-scale tests with granular sludge inoculation. Use of carbohydrate-based substances such as starch, sucrose, molasses and whey resulted in acidification, which in extreme cases inhibited DDT removal. A large amount of phosphate buffer prevented pH drop for starch, but not for sucrose. Better results were obtained with calcium carbonate as a buffering agent, which also had little effect on soil salinity. Very good effectiveness of biodegradation was achieved using sodium lactate which, however, caused alkalinisation of the soil, perhaps due to accumulation of sodium carbonate. Alkalinisation did not occur when calcium lactate was used instead. Experiments also demonstrated that Tween 80 surfactant could be successfully used as a substrate, without experiencing problems with pH control.

Biodegradation of phenol from a synthetic aqueous system using acclimatized activated sludge

Phenol is one of the aromatic hydrocarbons. Phenol and its derivatives are highly toxic. These pollutants can be observed in the effluents of many industries. This research investigates the removal of phenol by the use of activated sludge in a batch system. The effects of influencing factors on biodegradation efficiency have been evaluated. The main factors considered in this study were the volume of acclimatized activated sludge inoculation, pH, temperature, and initial concentration of phenol. The inoculation volumes of 1, 3, and 5 mL of acclimatized activated sludge were taken into account. Different pH values of 3, 5, 7, 9, and 11 were examined. The experiments were conducted for temperatures of 25, 30, 35, and 40 °C and initial phenol concentrations of 400, 800, 1,000, and 1,500 ppm. The results show that the acclimatized activated sludge has a high capacity for the removal of phenol. From a 100-mL aqueous solution was removed 1,500 ppm of phenol after 80 h. Furthermore, maximum phenol removal was observed for an inoculation volume of 5 mL for three different phenol concentrations of 100, 400, and 800 ppm. The best pH was 7 for the biodegradation process, and the optimum temperature was 30 °C. It was further found that an increase in the phenol concentration increased its removal time. Moreover, the activated sludge could effectively remove about 99.9 % of phenol from a synthetic aqueous solution in a batch system.

Membrane bioreactor (MBR) sludge inoculation in a hybrid process scheme concept to assist overloaded conventional activated sludge (CAS) process operations

This study analyzes the effect of inoculating membrane bioreactor (MBR) sludge in a parallel-operated overloaded conventional activated sludge (CAS) system. Modelling studies that showed the beneficial effect of this inoculation were confirmed though full scale tests. Total nitrogen (TN) removal in the CAS increased and higher nitrate formation rates were achieved. During MBR sludge inoculation, the TN removal in the CAS was proven to be dependent on MBR sludge loading. Special attention was given to the effect of inoculation on sludge quality. The MBR flocs, grown without selection pressure, were clearly distinct from the more compact flocs in the CAS system and also contained more filamentous bacteria. After inoculation the MBR flocs did not evolve into good-settling compact flocs, resulting in a decreasing sludge quality. During high flow conditions the effluent CAS contained more suspended solids. Sludge volume index, however, did not increase. Laboratory tests were held to determine the threshold volume of MBR sludge to be seeded into the CAS reactor. Above 16-30%, supernatant turbidity and scum formation increased markedly.

Bacterial Selection during the Formation of Early-Stage Aerobic Granules in Wastewater Treatment Systems Operated Under Wash-Out Dynamics.

Aerobic granular sludge is attractive for high-rate biological wastewater treatment. Biomass wash-out conditions stimulate the formation of aerobic granules. Deteriorated performances in biomass settling and nutrient removal during start-up have however often been reported. The effect of wash-out dynamics was investigated on bacterial selection, biomass settling behavior, and metabolic activities during the formation of early-stage granules from activated sludge of two wastewater treatment plants (WWTP) over start-up periods of maximum 60 days. Five bubble-column sequencing batch reactors were operated with feast-famine regimes consisting of rapid pulse or slow anaerobic feeding followed by aerobic starvation. Slow-settling fluffy granules were formed when an insufficient superficial air velocity (SAV; 1.8 cm s−1) was applied, when the inoculation sludge was taken from a WWTP removing organic matter only, or when reactors were operated at 30°C. Fast-settling dense granules were obtained with 4.0 cm s−1 SAV, or when the inoculation sludge was taken from a WWTP removing all nutrients biologically. However, only carbon was aerobically removed during start-up. Fluffy granules and dense granules were displaying distinct predominant phylotypes, namely filamentous Burkholderiales affiliates and Zoogloea relatives, respectively. The latter were predominant in dense granules independently from the feeding regime. A combination of insufficient solid retention time and of leakage of acetate into the aeration phase during intensive biomass wash-out was the cause for the proliferation of Zoogloea spp. in dense granules, and for the deterioration of BNR performances. It is however not certain that Zoogloea-like organisms are essential in granule formation. Optimal operation conditions should be elucidated for maintaining a balance between organisms with granulation propensity and nutrient removing organisms in order to form granules with BNR activities in short start-up periods.