Acrylic acid removal by acrylic acid utilizing bacteria from acrylonitrile-butadiene-styrene resin manufactured wastewater treatment system.

The aim of this study is to isolate the acrylic acid utilizing bacteria from the ABS resin manufactured wastewater treatment system. The bacteria should have the ability to remove acrylic acid and tolerate the acrylonitrile and acrylamide toxicity. The aim is also to understand the performance of isolated pure strain for treating different initial acrylic acid concentrations from synthetic wastewater. The results are: twenty strains were isolated from the ABS resin manufactured wastewater treatment system and twelve of them could utilize 600 mg/l acrylic acid for growth. Seven of twelve strains could tolerate the acrylonitrile and acrylamide toxicity, when the concentration was below 300 mg/l. Bacillus thuringiensis was one of the seven strains and the optimum growth temperature was 32 degrees C. Bacillus thuringiensis could utilize acrylic acid for growth, when the initial acrylic acid concentration was below 1,690.4 mg/l. Besides this, when the initial acrylic acid concentration was below 606.8 mg/l, the acrylic acid removal efficiency exceeded 96.3%. Bacillus thuringiensis could tolerate 295.7 mg/l acrylamide and 198.4 mg/l acrylonitrile toxicity but could not tolerate 297.3 mg/l epsilon-caprolactam.     

Characterization of biofilm of a rotating biological contactor treating synthetic wastewater

A four-stage rotating biological contactor (RBC) was designed and operated to treat synthetic wastewater containing 1,000 mg/l chemical oxygen demand (COD) and 112 mg/l NH(4)(+)-N. A mixed culture bacterial biofilm was developed consisting of a heterotrophic bacterium Paracoccus pantotrophus, nitrifiers and other heterotrophs. Applying the peculiar characteristics of P. pantotrophus of simultaneous heterotrophic nitrification and aerobic denitrification, high simultaneous removal of carbon and nitrogen could be achieved in the fully aerobic RBC. The microbial community structure of the RBC biofilm was categorized based on the nitrate reduction, biochemical reactions, gram staining and morphology. The presence of P. pantotrophus within the RBC biofilm was confirmed with an array of biochemical tests. Isolates from the four stages of RBC were grouped into complete denitrifiers, incomplete denitrifiers and non-denitrifiers. This categorization showed a higher relative abundance of P. pantotrophus in the first stage as compared with subsequent stages, in which other nitrifiers and heterotrophs were significantly present. High total nitrogen removal of upto 68% was in conformity with observations made using microbial categorization and biochemical tests. The high relative abundance of P. pantotrophus in the biofilm revealed that it could successfully compete with other heterotrophs and autotrophic nitrifiers in mixed bacterial biomass.     

Effect of didecyl dimethyl ammonium chloride on nitrate reduction in a mixed methanogenic culture.

The effect of the quaternary ammonium compound, didecyl dimethyl ammonium chloride (DDAC), on nitrate reduction was investigated at concentrations up to 100 mg/L in a batch assay using a mixed, mesophilic (35 degrees C) methanogenic culture. Glucose was used as the carbon and energy source and the initial nitrate concentration was 70 mg N/L. Dissimilatory nitrate reduction to ammonia (DNRA) and to dinitrogen (denitrification) were observed at DDAC concentrations up to 25 mg/L. At and above 50 mg DDAC/L, DNRA was inhibited and denitrification was incomplete resulting in accumulation of nitrous oxide. At DDAC concentrations above 10 mg/L, production of nitrous oxide, even transiently, resulted in complete, long-term inhibition of methanogenesis and accumulation of volatile fatty acids. Fermentation was inhibited at and above 75 mg DDAC/L. DDAC suppressed microbial growth and caused cell lysis at a concentration 50 mg/L or higher. Most of the added DDAC was adsorbed on the biomass. Over 96% of the added DDAC was recovered from all cultures at the end of the 100-days incubation period, indicating that DDAC did not degrade in the mixed methanogenic culture under the conditions of this study.     

Development and optimisation of VFA driven DEAMOX process for treatment of strong nitrogenous anaerobic effluents.

The recently proposed DEAMOX (DEnitrifying AMmonium OXidation) process combines the anammox reaction with autotrophic denitrifying conditions using sulphide as an electron donor for the production of nitrite from nitrate within an anaerobic biofilm. This paper firstly presents a feasibility study of the DEAMOX process using synthetic (ammonia + nitrate) wastewater where sulphide is replaced by volatile fatty acids (VFA) as a more widespread electron donor for partial denitrification. Under the influent N-NH+4/N-NO3(-) and COD/N-NO3(-) ratios of 1 and 2.3, respectively, the typical efficiencies of ammonia removal were around 40% (no matter whether a VFA mixture or only acetate were used) for nitrogen loading rates (NLR) up to 1236 mg N/l/d. This parameter increased to 80% by increasing the influent COD/N-NO3(-) ratio to 3.48 and decreasing the influent N-NH4 +/N-NO3(-) ratio to 0.29. As a result, the total nitrogen removal increased to 95%. The proposed process was further tested with typical strong nitrogenous effluent such as reject water (total N, 530-566 mg N/l; total COD, 1530-1780 mg/l) after thermophilic sludge anaerobic digestion. For this, the raw wastewater was split and partially ( approximately 50%) fed to a nitrifying reactor (to generate nitrate) and the remaining part ( approximately 50%) was directed to the DEAMOX reactor where this stream was mixed with the nitrified effluent. Stable process performance up to NLR of 1,243 mg N/l/d in the DEAMOX reactor was achieved resulting in 40, 100, and 66% removal of ammonia, NOx(-), and total nitrogen, respectively.     

Evaluation of nitrate removal by continuous culturing of an aerobic denitrifying bacterium, Paracoccus pantotrophus.

Nitrate removal under aerobic conditions was investigated using pure cultures of Paracoccus pantotrophus, which is a well-known aerobic-denitrifying (AD) bacterium. When a high concentration of cultures with a high carbon/nitrogen (C/N) ratio was preserved at the beginning of batch experiments, subsequently added nitrate was completely removed. When continuous culturing was perpetuated, a high nitrate removal rate (66.5%) was observed on day 4 post-culture, although gradual decreases in AD ability with time were observed. The attenuation in AD ability was probably caused by carbon limitation, because when carbon concentration of inflow water was doubled, nitrate removal efficiency improved from 18.1% to 59.6%. Bacterial community analysis using the polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) method showed that P. pantotrophus disappeared in the suspended medium on day 8 post-culture, whereas other bacterial communities dominated by Acidovorax sp. appeared. Interestingly, this replaced bacterial community also showed AD ability. As P. pantotrophus was detected as attached colonies around the membrane and bottom of the reactor, this bacterium can therefore be introduced in a fixed form for treatment of wastewater containing nitrate with a high C/N ratio.     

Biological nitrogen removal using bio-sorbed internal organic carbon from piggery wastewater in a post-denitrification MLE process.

Nitrogen removal from a piggery wastewater was investigated in a post-denitrification modified Lüdzack Ettinger (PDMLE) process. Overall hydraulic retention time (HRT) of the PDMLE, consisting of contact/separator (C/S), nitrification, denitrification and re-aerobic bioreactor was 10 days. 60% of the influent SCOD was separated in the C/S by contacting the return sludge with the synthetic wastewater, however, only 10% of the influent SCOD was separated from the piggery wastewater. Biosorption capacities of the synthetic wastewater and piggery wastewater were 800 and 150 mg/g-MLSS, respectively. In spite of the high organic and nitrogen load, nitrification efficiency was above 95%, and nitrification rate was about 180 mg-NH4+-N/L x day. The removed delta COD/delta nitrate ratios in the denitrification tank were 4.0 and 11.5 g-SCOD/g-nitrate, while denitrification rates were 8.4 and 2.6 mg-nitrate/day for synthetic and piggery wastewater, respectively. In the proposed PDMLE process, both bio-sorbed and bypassed organic matter could be successfully used for nitrate reduction as carbon sources and the final TN removal efficiency was as high as 95%.     

Enhanced denitrification with external carbon sources in a biological anoxic filter

Three parallel biological anoxic filters (BaFs) were operated to investigate the denitrification kinetics of methanol, brewery wastewater and bakery wastewater. The experiment was conducted within the temperature range of 15-20 °C, with an influent nitrate and carbon dosage of 30 mg/L and 150 mg COD/L (COD: chemical oxygen demand). The denitrification efficiencies of brewery wastewater, bakery wastewater and methanol were 84, 66 and 74%, specific denitrification rates were 1.44, 1.11 and 1.24 kg NO(3)-N/m(3) d, and total nitrogen (TN) removal rates were 74, 62 and 66%, respectively. The volatile attached solid (VAS) tests reveal that methanol has the minimum net biomass yield, so it needs the least carbon to nitrogen (expressed in COD to nitrate, C/N) ratio for complete denitrification. While the brewery wastewater and bakery wastewater need higher C/N ratio to remove all nitrate nitrogen, and they both may need pretreatment to remove phosphate when used as external carbon sources.     

Study of a three-stage fluidized bed process treating acrylic synthetic-fiber manufacturing wastewater containing high-strength nitrogenous compounds.

Polyacrylonitrile (PAN) is one of the major synthetic fibers commonly used in the mass production of clothing. The chemical synthesis of PAN is carried out by polymerization of the acrylonitrile (AN) monomers with co-monomers such as vinyl acetate, methyl acrylate and cyclohexyl acrylate. Using water quality analysis of the PAN wastewater, high concentration of organic nitrogen was found and the TKN/COD ratios achieved were 0.15-0.26, indicating the complicated biodegradation characteristics for the PAN wastewater. In order to enhance biodegradation of nitrogenous compounds in PAN wastewater, a combined three-stage process of thermophilic anaerobic/anoxic denitrification/aerobic nitrification fluidized bed reactors was employed. The results indicated that the concentration of effluent in the three-stage process of OD and organic nitrogen was 175 mg/L and 13 mg/L, respectively. Furthermore, molecular biotechnology was applied to study the microbial population in the thermophilic anaerobic fluidized bed reactor. From the results of denaturing gradient gel electrophoresis, the diversity of PAN-degrading bacteria would change in different volumetric loading. Furthermore, the bacteria communities in the thermophilic anaerobic fluidized bed reactor were also studied by fluorescence in situ hybridization and confocal laser scanning microscopy. Alpha and delta-Proteobacteria were dominant in the bacteria population, and some high G+C content bacteria and Clostridium could be characterized in this system.     

Inhibitory effects of nitrate reduction on methanogenesis in the presence of different electron donors.

The preferential utilization of different electron donors and their effects on the nitrate reduction and methanogenesis in a mixed, mesophilic (35 degrees C) methanogenic culture were investigated. Batch methanogenic cultures were fed with dextrin/peptone (D/P), propionate, acetate, and H(2)/CO(2) at an initial COD of 500 mg/L and an initial nitrate concentration of 50 mg N/L. Immediate cessation of methane production was observed in all nitrate-amended cultures. Methane production completely recovered in the D/P- and acetate-fed cultures, and partially recovered or did not recover in the propionate- and H(2)/CO(2)-fed, nitrate-amended cultures, respectively. Accumulation of denitrification intermediates was observed in both the propionate- and H(2)/CO(2)-fed cultures, which resulted in inhibition of fermentation and/or methanogenesis. The fastest and the slowest nitrate reduction were observed in the acetate- and propionate-fed cultures, respectively.     

Activated carbon fiber filler in aerated bioreactor for industrial wastewater treatment

The aerated bioreactor is a promising technology for wastewater treatment. Activated carbon fiber (ACF) used as a biomembrane carrier in wastewater disposal has attracted much more concern recently. The high modulus polyacrylonitrile (PAN)-based ACF was successfully used as a biomembrane carrier for hard-to-biodegrade industrial organic wastewater disposal in a lab-scale aerated biomembrane reactor at room temperature. The biocompatibility test shows that the biomembrane grows quickly on the ACF filler (ACFF) surface; bacteria and microzoon can breed on the ACFF surface at high chemical oxygen demand (COD) concentration. The COD removal rate tests show that the ACFF bioreactor has high capability to remove COD.     

In-situ characterization of microbial community in an A/O submerged membrane bioreactor with nitrogen removal.

The bacterial community involved in removing nitrogen from sewage and their preferred DO environment within an anoxic/oxic membrane bioreactor (A/O MBR) was investigated. A continuously operated laboratory-scale A/O MBR was maintained for 360 d. At a sludge age of 150 d and a C/N ratio of 3.5, the system was capable of removing 88% of the influent nitrogen from raw wastewater through typical nitrogen removal transformations (i.e. aerobic ammonia oxidation and anoxic nitrate reduction). Characterization of the A/O MBR bacterial community was carried out using fluorescence in situ hybridization (FISH) techniques. FISH results further showed that Nitrosospira spp. and Nitrospira spp. were the predominant groups of ammonia and nitrite oxidizing group, respectively. They constituted up to 11% and 6% of eubacteria at DO below 0.05 mg/l (low DO), respectively, and about 14% and 9% of eubacteria at DO between 2-5 mg/l (sufficient DO), respectively, indicating preference of nitrifiers for a higher DO environment. Generally low counts of the genus Paracoccus were detected while negative results were observed for Paracoccus denitrificans, Alcaligenes spp, and Pseudomonas stutzeri under the low and sufficient DO environments. The overall results indicate that Nitrosospira spp., Nitrospira spp. and members of Paracoccus spp. can be metabolically functional in nitrogen removal in the laboratory-scale A/O MBR system.     

Use of agro-food wastewaters for the optimisation of the denitrification process.

The aim of this work was to study the feasibility of the denitrification process enhancement, in the Ciudad Real (Spain) WWTP, by dosing agro-food wastewaters generated nearby the city. The studied agro-food wastewaters were characterised by a high COD and low nutrients concentration. The denitrification rates with these wastewaters were lower than those obtained either with acetate or urban sewage, however the dose of agro-food wastewaters raised significantly the denitrification capacity in the WWTP because of the significant increase of easily biodegradable substrates in the wastewater. From the laboratory NUR batch test it was observed that the best agro-food wastewater to enhance the denitrification process was that coming from tomato processing, which presented an average denitrification rate of 1.9 mg NOx-N/(g VSS.h) and an average denitrification yield of 0.2 mg NOx-N/mg COD. The viability of the use of tomato processing wastewater was checked in a pilot plant optimised for urban sewage treatment with biological nutrient removal. The optimum dose, 5.9 mg COD/mg NOx-N, was applied and 99% of the nitrate was removed from the wastewater without influencing negatively either the COD or P effluent concentrations.     

生物接触氧化流化床处理氨氮污水的实验研究

为了提高生物接触氧化流化床处理氨氮污水的脱氮效果,采用生物接触氧化流化床在自然温度下处理人工配制模拟生活污水实验的方法,研究了氨氮污水脱氮处理的可行性、方法与效果。实验结果表明:氨氮被氧化成硝酸可由两类独立的细菌分别催化完成;反应的适宜温度为20~35℃;亚硝酸菌的最适pH值为7~8.5之间,硝酸菌为6~7.5;亚硝酸菌和硝酸菌溶解氧质量浓度在0.5 mg/L以上才能取得较好的硝化效果。反应器内填料粒径在10 mm左右有利于提高氨氮的去除效率;间歇式进水方式使活性污泥具有良好的沉降性,可为氨氮的去除提供良好的环境条件。     

Nitrogen removal in a fluidized bed bioreactor by using mixed culture under oxygen-limited conditions.

Nitrogen removal involving nitrification and denitrification was investigated in a fluidized bed bioreactor by using mixed culture sludge under oxygen-limited conditions. Methane was used as a sole carbon source for denitrification. In this study, optimal nitrification and denitrification rates were examined by varying methane and oxygen gas dissolution flow rates, 90 ml/min, 400 ml/min and 650 ml/min, in each. Simultaneously nitrification and denitrification was achieved. The total nitrogen removal rate was 15-mg N/g VSS. d, 21-mg N/g VSS. d and 26.4-mg N/g VSS. d at gas dissolution flow rate 90 ml/min, 400 ml/min and 650 ml/min, respectively. No significant accumulation of nitrite was found in this experiment. Nitrogen removal rates depend on gas dissolution flow rates. DO concentration was at 0.5-2 mg/L.     

Substrate utilization characteristics of the predominant filamentous and floc-forming bacteria isolated from a chemical fiber factory wastewater treatment plant

To supply theoretical verification of the function of a selector to control aerobic activated sludge bulking in the wastewater treatment plant for a chemical fiber factory in Taiwan, the filamentous and floc-forming bacteria in the aeration tank in the full-scale plant were examined microscopically and isolated. The kinetic characteristics of filamentous and floc-forming bacteria were also investigated.The predominant filamentous organism was Sphaerotilus natans. In addition to this organism, 21 strains of non-filamentous bacteria were isolated using the plate count method. These included Aeromonas jandaei DNA group 9, Acinetobacter johnsonii/genospecies 7, Bacillus pasteurii and Bacillus sp. (using the Biolog identification system). Nine strains showed the ability to form flocs when cultivated in glucose mineral salts medium.With glucose and acetate as sole substrates, the 4 floc-forming bacteria tested showed different substrate utilization characteristics. The 4 strains could be divided into 3 groups. The first group was the substrate degrading bacteria, the second group was the acid degrading bacteria and the other strains were those that had the highest substrate degradation rates at low substrate concentrations (below 800 mg/l). None of the floc-formers could utilize ethylene glycol, which is the major wastewater component. The kinetic characteristics of filamentous bacterium S. natans (Km = 4.0 mg glucose/l, Vm = 0.43 μl O₂/l) and the flocforming bacterium Aeromonas jandaei DNA group 9 (Km = 34.8 mg glucose/l, Vm = 0.59 μl O₂/l) provided information for selector design.     

Comparison of aerobic denitrifying activity among three cultural species with various carbon sources.

Abilities of three aerobic denitrifiers such as Alcaligenes faecalis, Microvirgula aerodenitrificans and Paracoccus pantotrophus were compared from the viewpoints of nitrate removal efficiency and organic matter utilization. First, the effect of carbon source was investigated. Although nitrate reduction was observed in all strains under aerobic conditions, a change of carbon source considerably affected the denitrification ability. In the case of P. pantotrophus, nitrate and nitrite were completely removed in three days under sodium acetate or leucine as a carbon source. In the case of A. faecalis, sufficient nitrate removal was observed only when sodium acetate or ethanol was added. P. pantotrophus and A. faecalis showed a higher ability of nitrate removal than that of M. aerodenitrificans. Therefore, P. pantotrophus was selected in order to investigate the effects of concentration and repetitive addition of carbon. Sodium acetate was used as a sole carbon source. Nitrate was not reduced when the carbon concentration was below 500 mgC/L. However, when carbon source was added repeatedly, nitrate was reduced under 100 mgC/L after the optical density of the bacterium reached above 1.0. This result indicated that a high enough level of bacterial density was necessary to express aerobic denitrification activity.     

Nitrate removal with low N2O emission by application of sulfur denitrification in actual agricultural field.

Sulfur denitrification was applied to the agricultural field and the characteristics of the treatment were evaluated from the viewpoints of nitrate removal efficiency and nitrous oxide (N2O) emission. Two actual sites where sulfur denitrification was performed were surveyed. One is a valley bottom field, where groundwater contaminated with nitrate is coming up as spring water. The nitrate concentration in influent was about 45 mgN/L. The other was wastewater from a plastic greenhouse. The nitrate concentration in inflow water was about 200 mgN/L. Nitrate was almost removed by the containers packed with sulfur (S0)-CaCO3 blocks in both sites. Increase of sulfate indicated that nitrate was removed by sulfur denitrification. This was also estimated stoichiometrically from the relationships between the removed nitrate and produced sulfate. The N2O was supersaturated in water at most sampling points and the highest concentration of dissolved N2O reached 900 microgN/L in Saitama in March. It seemed that insufficient nitrate removal caused accumulation of intermediates during denitrification, such as nitrite and N2O, in this month. However, the emission ratio of N2O to the removed nitrate during these processes was kept low, ranging from 0.01 to 0.19%, at both two sites throughout all surveys.     

Onsite wastewater nitrogen reduction with expanded media and elemental sulfur biofiltration

A passive biofiltration process has been developed to enhance nitrogen removal from onsite sanitation water. The system employs an initial unsaturated vertical flow biofilter with expanded clay media (nitrification), followed in series by a horizontal saturated biofilter for denitrification containing elemental sulfur media as electron donor. A small-scale prototype was operated continuously over eight months on primary wastewater effluent with total nitrogen (TN) of 72.2 mg/L. The average hydraulic loading to the unsaturated biofilter surface was 11.9 cm/day, applied at a 30 min dosing cycle. Average effluent TN was 2.6 mg/L and average TN reduction efficiency was 96.2%. Effluent nitrogen was 1.7 mg/L as organic N, 0.93 mg/L as ammonium (NH(4)-N), and 0.03 as oxidized (NO(3) + NO(2)) N. There was no surface clogging of unsaturated media, nitrate breakthrough, or replenishment of sulfur media over eight months. Visual and microscopic examinations revealed substantially open pores with limited material accumulation on the upper surface of the unsaturated media. Material accumulation was observed at the inlet zone of the denitrification biofilter, and sulfur media exhibited surface cavities consistent with oxidative dissolution. Two-stage biofiltration is a simple and resilient system for achieving high nitrogen reductions in onsite wastewater.     

Comparison of sequentially combined carbon with sole carbon in denitrification and biological phosphorus removal.

The sequentially combined carbon (SCC) of methanol and acetic acid was used for the biological nutrient removal (BNR). Its BNR performance was compared with methanol or acetic acid as a sole carbon substrate. Compared to the sole carbon substrate, the use of SCC demonstrated the highest overall TIN removal of 98.3% at a COD ratio of 30 mg COD/l of methanol/50 mg CDO/l of acetic acid. Furthermore, denitrification was more enhanced when methanol was used as one of the SCC, rather than as a sole carbon source. Complete phosphorus removal was accomplished with a non-detectable o-P concentration when SCC was added. This research also showed that aerobic denitrifiers appear to prefer acetic acid to methanol, and the amount of poly-beta-hydroxybutyrate (PHB) stored by P accumulating organisms (PAOs) using acetic acid in the anoxic zone could be another important factor in improving the aerobic denitrification. The SCC was a very favorable carbon source for the aerobic denitrification since acetic acid was utilized more efficiently for P-release in accordance with increase of PHB stored in the cell of PAOs by removing nitrogen first using methanol.     

Possible denitrification technology for small settlement water supplies

A biological denitrification technology has been developed and tested. In the laboratory, the denitrifying bacteriumHyphomicrobium X was immobilised on polyurethane and polyvinylacetate foams, glass beads, glass wool, coarse river sand and also entrapped in alginate beads. In all cases the bacteria retained their capacity to actively denitrify with methanol as the carbon source. The establishment times and longevity of the bacteria on polyurethane and sand columns was studied, as was the effect of methanol/nitrate ratios on the denitrification process in flow-through experiments. Conditions were achieved where both nitrate and methanol were removed stoichiometrically. Complete removal of nitrate could be achieved in the temperature range 4 to 48 °C. Flow-through and batch procedures were investigated and a prototype batch system was developed which was capable of treating 200 litres of nitrate-containing water per day.