Simultaneous oxidation of ammonium and p-cresol linked to nitrite reduction by denitrifying sludge

The metabolic capability of denitrifying sludge to oxidize ammonium and p-cresol was evaluated in batch cultures. Ammonium oxidation was studied in presence of nitrite and/or p-cresol by 55 h. At 50 mg/L NH₄⁺-N and 76 mg/L NO₂⁻-N, the substrates were consumed at 100% and 95%, respectively, being N₂ the product. At 50 mg/L NH₄⁺-N and 133 mg/L NO₂⁻-N, the consumption efficiencies decreased to 96% and 70%, respectively. The increase in nitrite concentration affected the ammonium oxidation rate. Nonetheless, the N₂ production rate did not change. In organotrophic denitrification, the p-cresol oxidation rate was slower than ammonium oxidation. In litho-organotrophic cultures, the p-cresol and ammonium oxidation rates were affected at 133 mg/L NO₂⁻-N. Nonetheless, at 76 mg/L NO₂⁻-N the denitrifying sludge oxidized ammonium and p-cresol, but at different rate. Finally, this is the first work reporting the simultaneous oxidation of ammonium and p-cresol with the production of N₂ from denitrifying sludge.     

Thermophilic anaerobic digestion of Lurgi coal gasification wastewater in a UASB reactor

Lurgi coal gasification wastewater (LCGW) is a refractory wastewater, whose anaerobic treatment has been a severe problem due to its toxicity and poor biodegradability. Using a mesophilic (35 ± 2 °C) reactor as a control, thermophilic anaerobic digestion (55 ± 2 °C) of LCGW was investigated in a UASB reactor. After 120 days of operation, the removal of COD and total phenols by the thermophilic reactor could reach 50-55% and 50-60% respectively, at an organic loading rate of 2.5 kg COD/(m³ d) and HRT of 24 h; the corresponding efficiencies were both only 20-30% in the mesophilic reactor. After thermophilic digestion, the wastewater concentrations of the aerobic effluent COD could reach below 200 mg/L compared with around 294 mg/L if mesophilic digestion was done and around 375 mg/L if sole aerobic pretreatment was done. The results suggested that thermophilic anaerobic digestion improved significantly both anaerobic and aerobic biodegradation of LCGW.     

Measurement of phenol and p-cresol in urine and feces using vacuum microdistillation and high-performance liquid chromatography

In this article, we describe a simple, sensitive, accurate, and repeatable method for the measurement of phenol and p-cresol (4-methylphenol) in human urine and feces. We examined a number of parameters to identify an optimal extraction protocol. Purification of sample extracts was achieved by low-temperature vacuum microdistillation. Separation was achieved in approximately 15 min by high-performance liquid chromatography (HPLC) with quantification by fluorescence at 284/310 nm. Limits of detection for phenol were 2 ng/ml for urine and 20 ng/g for feces, and those for p-cresol were 10 ng/ml for urine and 100 ng/g for feces. For comparison, approximate mean values for urine are 3 μg/ml for phenol and 30 μg/ml for p-cresol, and those for feces are 1 μg/g for phenol and 50 μg/g for p-cresol. An experienced analyst can process 60 samples each day using this method.     

Examination of microbial fuel cell start-up times with domestic wastewater and additional amendments

Rapid startup of microbial fuel cells (MFCs) and other bioreactors is desirable when treating wastewaters. The startup time with unamended wastewater (118 h) was similar to that obtained by adding acetate or fumarate (110-115 h), and less than that with glucose (181 h) or Fe(III) (353 h). Initial current production took longer when phosphate buffer was added, with startup times increasing with concentration from 149 h (25 mM) to 251 h (50 mM) and 526 h (100 mM). Microbial communities that developed in the reactors contained Betaproteobacteria, Acetoanaerobium noterae, and Chlorobium sp. Anode biomass densities ranged from 200 to 600 μg/cm² for all amendments except Fe(Ш) (1650 μg/cm²). Wastewater produced 91 mW/m², with the other MFCs producing 50 mW/m² (fumarate) to 103 mW/m² (Fe(III)) when amendments were removed. These experiments show that wastewater alone is sufficient to acclimate the reactor without the need for additional chemical amendments.     

Long term operation of pilot-scale biological nutrient removal process in treating municipal wastewater

The performance of a pilot-scale biological nutrient removal process has been evaluated for 336 days, receiving the real municipal wastewater with a flowrate of 6.8 m³/d. The process incorporated an intermittent aeration reactor for enhancing the effluent quality, and a nitrification reactor packed with the porous polyurethane foam media for supporting the attached-growth of microorganism responsible for nitrification. The observation shows that the process enabled a relatively stable and high performance in both organics and nutrient removals. When the SRT was maintained at 12 days, COD, nitrogen, and phosphorus removals averaged as high as 89% at a loading rate of 0.42–3.95 kg COD/m³ d (corresponding to average influent concentration of 304 mg COD/L), 76% at the loading rate of 0.03–0.27 kg N/m³ d (with 37.1 mg TN/L on average), and 95% at the loading rate of 0.01–0.07 kg TP/m³ d (with 5.4 mg TP/L on average), respectively.     

Effects of key operational parameters on biohydrogen production via anaerobic fermentation in a sequencing batch reactor

In this study, a series of tests were conducted in a 6 L anaerobic sequencing batch reactor (ASBR) to investigate the effect of pH, hydraulic retention time (HRT) and organic loading rate on biohydrogen production at 28 °C. Sucrose was used as the main substrate to mimic carbohydrate-rich wastewater and inoculum was prepared from anaerobic digested sludge without pretreatment. The reactor was operated initially with nitrogen sparging to form anaerobic condition. Results showed that methanogens were effectively suppressed. The optimum pH value would vary depending on the HRT. Maximum hydrogen production rate and yield of 3.04 L H₂/L reactor d and 2.16 mol H₂/mol hexose respectively were achieved at pH 4.5, HRT 30 h, and OLR 11.0 kg/m³ d. Two relationships involving the propionic acid/acetic acid ratio and ethanol/acetic acid ratio were derived from the analysis of the metabolites of fermentation. Ethanol/acetic acid ratio of 1.25 was found to be a threshold value for higher hydrogen production.     

Textiles wastewater treatment using anoxic filter bed and biological wriggle bed-ozone biological aerated filter

In this study, the performance of the anoxic filter bed and biological wriggle bed-ozone biological aerated filter (AFB-BWB-O₃-BAF) process treating real textile dyeing wastewater was investigated. After more than 2 month process operation, the average effluent COD concentration of the AFB, BWB, O₃-BAF were 704.8 mg/L, 294.6 mg/L and 128.8 mg/L, with HRT being 8.1-7.7 h, 9.2 h and 5.45 h, respectively. Results showed that the effluent COD concentration of the AFB decreased with new carriers added and the average removal COD efficiency was 20.2%. During operation conditions, HRT of the BWB and O₃-BAF was increased, resulting in a decrease in the effluent COD concentration. However, on increasing the HRT, the COD reduction capability expressed by the unit carrier COD removal loading of the BWB reactor increased, while that of the O₃-BAF reactor decreased. This study is a beneficial attempt to utilize the AFB-BWB-O₃-BAF combine process for textile wastewater treatment.     

Phenol removal from hypersaline wastewaters in a Membrane Biological Reactor (MBR): operation and microbiological characterisation

In this study, two Membrane Biological Reactors (MBR) with submerged flat membranes, one at lab-scale conditions and the other at pilot-plant conditions, were operated at environmental temperature to treat an industrial wastewater characterised by low phenol concentrations (8-16 mg L⁻¹) and high salinity (∼150-160 mS cm⁻¹). During the operation of both reactors, the phenol loading rate was progressively increased and less than 1 mg phenol L⁻¹ was detected even at very low HRTs (0.5-0.7 days). Membrane fouling was minimized by the cross flow aeration rate inside the MBRs and by intermittent permeation. Microbial community analysis of both reactors revealed that members of the genera Halomonas and Marinobacter (gammaproteobacteria) were major components. Growth-linked phenol degradation by pure cultures of Marinobacter isolates demonstrated that this bacterium played a major role in the removal of phenol from the bioreactors.     

Biodegradation of phenol and <Emphasis Type="Italic">m</Emphasis>-cresol by <Emphasis Type="Italic">Candida albicans</Emphasis> PDY-07 under anaerobic condition

Strain Candida albicans PDY-07 was used to study the anaerobic biodegradation of phenol and m-cresol as single and dual substrates in batch cultures. The strain had a higher potential to degrade phenol than m-cresol. The cell growth kinetics of batch cultures with various initial m-cresol concentrations was investigated, and the Haldane kinetic model adequately described the dynamic behavior of cell growth on m-cresol. When cells grew on the mixture of phenol and m-cresol, substrate interactions were observed. Phenol inhibited the utilization of m-cresol; on the other hand, m-cresol also inhibited the degradation of phenol. However, the presence of low-concentration phenol enhanced m-cresol biodegradation; 100 mg/l m-cresol could be completely degraded within a shorter period of time than m-cresol alone in the presence of 150–300 mg/l phenol. The maximum m-cresol biodegradation rate was obtained at the existence of 200 mg/l phenol. Phenol was preferably utilized by the strain as a carbon and energy source. In addition, a sum kinetics model was used to describe the cell growth behavior in binary mixture of phenol and m-cresol, and the interaction parameters were determined. The model adequately predicted the growth kinetics and the interaction between the substrates.     

Simultaneous Cr(VI) reduction and phenol degradation in pure cultures of Pseudomonas aeruginosa CCTCC AB91095

Simultaneous Cr(VI) reduction and phenol degradation were investigated in a reactor containing Pseudomonas aeruginosa CCTCC AB91095. Phenol was used as carbon source. P.aeruginosa utilized metabolites formed during phenol degradation as energy source for Cr(VI) reduction. Cr(VI) inhibited both Cr(VI) reduction and phenol degradation when Cr(VI) concentration exceeded the optimum value (20 mg/L), whereas phenol enhanced both Cr(VI) reduction and phenol degradation below the optimum initial concentration of 100 mg/L. Cr(III) was the predominant product of Cr(VI) reduction in cultures after incubation for 24 h. Both Cr(VI) reduction and phenol degradation were influenced by the amount of inocula. The concentration of Cr(VI) and phenol declined quickly from 20, 100 to 3.36, 29.51 mg/L in cultures containing of 5% (v/v) inoculum after incubation for 12 h, respectively. The whole study showed that P. aeruginosa is promising for the reduction of toxic Cr(VI) and degradation of organic pollutants simultaneously in the mineral liquid medium.     

Electricity generation using chocolate industry wastewater and its treatment in activated sludge based microbial fuel cell and analysis of developed microbial community in the anode chamber

Feasibility of using chocolate industry wastewater as a substrate for electricity generation using activated sludge as a source of microorganisms was investigated in two-chambered microbial fuel cell. The maximum current generated with membrane and salt bridge MFCs was 3.02 and 2.3 A/m², respectively, at 100 Ω external resistance, whereas the maximum current generated in glucose powered MFC was 3.1 A/m². The use of chocolate industry wastewater in cathode chamber was promising with 4.1 mA current output. Significant reduction in COD, BOD, total solids and total dissolved solids of wastewater by 75%, 65%, 68%, 50%, respectively, indicated effective wastewater treatment in batch experiments. The 16S rDNA analysis of anode biofilm and suspended cells revealed predominance of β-Proteobacteria clones with 50.6% followed by unclassified bacteria (9.9%), α-Proteobacteria (9.1%), other Proteobacteria (9%), Planctomycetes (5.8%), Firmicutes (4.9%), Nitrospora (3.3%), Spirochaetes (3.3%), Bacteroides (2.4%) and γ-Proteobacteria (0.8%). Diverse bacterial groups represented as members of the anode chamber community.     

Evaluation of performance and microbial community in a two-stage UASB reactor pretreating acrylic fiber manufacturing wastewater

A two-stage UASB reactor was employed to pretreat acrylic fiber manufacturing wastewater. Mesophilic operation (35 ± 0.5 °C) was performed with hydraulic retention time (HRT) varied between 28 and 40 h. Mixed liquor suspended solids (MLSS) in the reactor was maintained about 8000 mg/L. The results showed COD and sulfate removal could be kept at 51% and 75%, respectively, when the HRT was no less than 38 h. Sulfate reduction mainly occurred in the acidification-stage reactor while methane production mainly occurred in the methane-stage reactor. The size of granule formed in the acidification-stage reactor ranged between 1 and 5 mm while the largest size of granule in the methane-stage reactor ranged from 0.5 to 2 mm. Compared to microbial populations in the acidification-stage reactor, the microbial diversity in methane-stage reactor was more abundant. In the acidification-stage reactor, the Syntrophobacter sulfatireducens devoted to both sulfate reduction and acetate production.     

A membrane-free baffled microbial fuel cell for cathodic reduction of Cu(II) with electricity generation

A membrane-free baffled microbial fuel cell (MFC) was developed to treat synthetic Cu(II) sulfate containing wastewater in cathode chamber and synthetic glucose-containing wastewater fed to anode chamber. Maximum power density of 314 mW/m³ with columbic efficiency of 5.3% was obtained using initial Cu²⁺ concentration of 6400 mg/L. Higher current density favored the cathodic reduction of Cu²⁺, and removal of Cu²⁺ by 70% was observed within 144 h using initial concentration of 500 mg/L. Powder X-ray diffraction (XRD) analysis indicated that the Cu²⁺ was reduced to Cu₂O or Cu₂O plus Cu which deposited on the cathode, and the deficient cathodic reducibility resulted in the formation of Cu₄(OH)₆SO₄ at high initial Cu²⁺ concentration (500-6400 mg/L). This study suggested a novel low-cost approach to remove and recover Cu(II) from Cu²⁺-containing wastewater using MFC-type reactor.     

Performance evaluation and phylogenetic characterization of anaerobic fluidized bed reactors using ground tire and pet as support materials for biohydrogen production

This study evaluated two different support materials (ground tire and polyethylene terephthalate [PET]) for biohydrogen production in an anaerobic fluidized bed reactor (AFBR) treating synthetic wastewater containing glucose (4000 mg L⁻¹). The AFBR, which contained either ground tire (R1) or PET (R2) as support materials, were inoculated with thermally pretreated anaerobic sludge and operated at a temperature of 30 °C. The AFBR were operated with a range of hydraulic retention times (HRT) between 1 and 8 h. The reactor R1 operating with a HRT of 2 h showed better performance than reactor R2, reaching a maximum hydrogen yield of 2.25 mol H₂ mol⁻¹ glucose with 1.3 mg of biomass (as the total volatile solids) attached to each gram of ground tire. Subsequent 16S rRNA gene sequencing and phylogenetic analysis of particle samples revealed that reactor R1 favored the presence of hydrogen-producing bacteria such as Clostridium, Bacillus, and Enterobacter.     

Leachate treatment and greenhouse gas emission in subsurface horizontal flow constructed wetland

Organic and nitrogen removal efficiencies in subsurface horizontal flow wetland system (HSF) with cattail (Typha augustifolia) treating young and partially stabilized solid waste leachate were investigated. Hydraulic loading rate (HLR) in the system was varied at 0.01, 0.028 and 0.056 m³/m² d which is equivalent to hydraulic retention time (HRT) of 28, 10 and 5 d. Average BOD removals in the system were 98% and 71% when applied to young and partially stabilized leachate at HLR of 0.01 m³/m² d. In term of total kjeldahl nitrogen, average removal efficiencies were 43% and 46%. High nitrogen in the stabilized leachate adversely affected the treatment performance and vegetation in the system. Nitrogen transforming bacteria were found varied along the treatment pathway. Methane emission rate was found to be highest at the inlet zone during young leachate treatment at 79–712 mg/m² d whereas CO₂ emission ranged from 26–3266 mg/m² d. The emission of N₂O was not detected.     

Electricity generation and modeling of microbial fuel cell from continuous beer brewery wastewater

Electricity production and modeling of microbial fuel cell (MFC) from continuous beer brewery wastewater was studied in this paper. A single air-cathode MFC was constructed, carbon fiber was used as anode and diluted brewery wastewater (COD = 626.58 mg/L) as substrate. The MFC displayed an open-circuit voltage of 0.578 V and a maximum power density of 9.52 W/m³ (264 mW/m²). Using the model based on polarization curve, various voltage losses were quantified. At current density of 1.79 A/m², reaction kinetic loss and mass transport loss both achieved to 0.248 V; while ohmic loss was 0.046 V. Results demonstrated that it was feasible and stable for producing bioelectricity from brewery wastewater; while the most important factors which influenced the performance of the MFC are reaction kinetic loss and mass transport loss.     

Effects of hydraulic loading rate on pollutants removal by a deep subsurface wastewater infiltration system

The subsurface wastewater infiltration (SWI) system proved to be an effective and low-cost technique for decentralized sewage treatment in areas without adequate domestic treatment facilities. Field-scale experiments were conducted through a deep SWI system, with effective depth of 1.5 m, under hydraulic loading rates of 0.040, 0.065, 0.081 and 0.10 m³/m² d. Taking the hydraulic and treatment efficiencies into consideration, the hydraulic loading rate of 0.081 m³/m² d was recommended. Under this condition, NH₃-N, TN, and COD removal efficiencies were 86.2 ± 3.0, 80.7 ± 1.9 and 84.8 ± 2.1%, respectively. In the effluent, NH₃-N concentration declined to 2.3-4.4 mg/L, accounting for 63.2-65.6% of TN. NO₃-N concentration increased from 0.2 to 0.3 mg/L in the influent to 2.0-2.5 mg/L in the effluent. The nitrifying bacteria number declined with increased depth, while the amount of denitrifying bacteria increased. The analysis of results about the nitrifying and denitrifying bacteria distribution indicated that the most effective ranges for nitrification and denitrification process were 0.3-0.7 m and 0.7-1.5 m, respectively.     

Treatment of poultry slaughterhouse wastewater in hybrid upflow anaerobic sludge blanket reactor packed with pleated poly vinyl chloride rings

In this study, the performance of 5.4 L hybrid upflow anaerobic sludge blanket (HUASB) reactor for treating poultry slaughterhouse wastewater under mesophilic conditions (29-35 °C), was investigated. After starting-up, the reactor was loaded up to an OLR of 19 kg COD/m³ d and achieved varied TCOD and SCOD removal efficiencies of 70-86% and 80-92%, respectively. The biogas was varied between 1.1 and 5.2 m³/m³ d with the maximum methane content of 72%. The maximum methane yield was 0.32 m³/kg COD_removed at an OLR of 9.27 kg COD/m³ d. Black matured granules of size between 2.5 and 5 mm were observed at the end of 225 d operation. RTD study showed the flow behavior was in mixed regime at the end of performance study. Step wise polynomial regression analysis was fitted well. Methanobacterium and Methanosaeta bacteria were dominant at the end of start-up whereas Methanosarcina, Cocci and rods were predominant at the end of performance studies.     

Treatment of coal gasification wastewater by a two-continuous UASB system with step-feed for COD and phenols removal

A two-continuous mesophilic (37 ± 2 °C) UASB system with step-feed was investigated as an attractive optimization strategy for enhancing COD and total phenols removal of the system and improving aerobic biodegradability of real coal gasification wastewater. Through the step-feed period, the maximum removal efficiencies of COD and total phenols reached 55-60% and 58-63% respectively in the system, at an influent flow distribution ratio of 0.2 and influent COD concentration of 2500 mg/L; the corresponding efficiencies were at low levels of 45-50% and 43-50% respectively at total HRT of 48 h during the single-feed period. The maximum specific methanogenic activity and substrate utilization rate were 592 ± 16 mg COD-CH₄/(gVSS d) and 89 ± 12 mg phenol/(gVSS d) during the step-feed operation. After the anaerobic digestion with step-feed, the aerobic effluent COD concentration decreased from 270 ± 9 to 215 ± 10 mg/L. The results suggested that step-feed enhanced the degradation of refractory organics in the second reactor.     

Nitrogen removal from wastewater with a low COD/N ratio at a low oxygen concentration

The goal of the study was to determine the effectiveness of nitrification and denitrification and the kinetics of ammonia removal from a mixture of wastewater and anaerobic sludge digester supernatant in an SBR at limited oxygen concentration. In addition, the COD removal efficiency and sludge production were assessed.In the SBR cycle alternating aerobic and anaerobic phases occurred; in the aeration phase the dissolved oxygen (DO) concentration was below 0.7 mg O₂/L. The low DO concentration did not inhibit ammonia oxidation-nitrification and the efficiency was ca. 96-98%. However, a relatively high COD concentration in the effluent was detected. The values of K_m and V_max, calculated from the Michaelis-Menten equation, were 43 mg N-NH₄/L and 15.64 mg N-NH₄/L h, respectively. Activated sludge production was almost stable (0.62-0.66 g MLVSS/g COD). A high net biomass production resulted from a low specific biomass decay rate of 0.0015 d⁻¹.