CH4 production potential of autotrophic nitrification bacteria produced in the submerged nitrification bioreactor in the laboratory and kinetic analysis.

In this study, CH4 production capacity of nitrification bacteria (NB) obtained from the submerged biofilter in the laboratory was investigated. Biochemical methane potential (BMP) test was carried out with the NB amount of zero (control, CR), 5% (R1), 10% (R2), and 15% (R3) at a temperature of about 37 ± 0.5°C. Compared to the CR, significantly higher cumulative CH4 volume of about 290, 490, and 715 mL were determined in the R1, R2, and R3, respectively. All the applied kinetic models gave good results (R2 ≥0.97), while the Transference Function and First-order models provided the better R2 values. The delay phase (λ) was not observed in the AD process, and CH4 production started immediately on the first day of operation. The predicted k value of 0.133 day-1 was high in CR, while it was approximately between 0.078 and 0.112 day-1 for the higher amount of NB containing BMP units, which indicated that the AD required long reaction time.

Effects of microwave irradiation at various temperatures on biosludge disintegration.

The waste biological sludge disintegration by using microwave irradiation was investigated at a ramping rate of 2°C/min and 5 min holding time at various target temperatures. Significant disintegration of biosludge was observed and the highest disintegration degree was determined about 82% at the temperature of 110°C. Increase of target temperature elevated the energy needs to 98, 123 and 148 kWh/kg TS at the temperatures of 75°C, 90°C and 110°C, respectively. The gradual increase of sugar and protein in the sludge slurry with increasing temperatures indicates successful degradation. The microwave pretreatment increased the specific surface area of the sludge by particle size reduction. The specific surface area of raw sludge was 70 m2/kg and rose to approximately 253.7 m2/kg at 110°C with an increment ratio of 260%. Although a significant NH4-N release was not observed, PO4-P concentrations increased from 11.0 mg/L to 16.3, 20.7 and 29.2 mg/L at the temperatures of 75°C, 90°C, 110°C, respectively. While the specific filter resistance of waste biological sludge was about 1.0 × 1013, increasing the microwave target temperature, the ability of dewatering decreased and the highest SFR value of 5.1 × 1014 was observed at the temperature of 110°C.

A kinetic study on the nitrification process in the upflow submerged biofilter reactor.

In extent of this study, ammonium removal from wastewater through biological nitrification process was performed in upflow biofilm reactors. The effects of hydraulic retention time (HRT) and nitrogen loading rate (NLR) on the nitrification process were investigated. For the nitrification process, the optimum HRT and NLR were determined to be 80 hr and 0.044 kg/m3.day, respectively. It is observed that the efficiency increased from 53% to 96% along with the increase in HRT from 22 hr to 80 hr and the decrease in NLR from 0.165 kg/m3.day to 0.044 kg/m3.day.The substrate consumption kinetics were studied in the attached growth reactor, and the Monod kinetic model, first-order kinetic model, modified Stover-Kincannon and Grau second-order kinetic models were examined. For the substrate consumption kinetic study, experimental studies were performed at 125, 150, 175, 200, 225 mg NH4-N/L substrate concentrations and 62 hr at HRT during the nitrification process. As a result of the considering kinetic studies, it was determined that the kinetic study was suitable for the modified Stover-Kincannon kinetic model that had the highest coefficient of regression by 0.997 and when the effluent NH4-N concentrations and NH4-N removal efficiencies calculated using kinetic models were examined, it was observed that the results closest to the experimental results (4.5, 10.1, 19.7, 26.2 and 42.3 mg NH4-N/L) were obtained through the modified Stover-Kincannon model (4.16, 10.71, 18.92, 28.12 and 39.51 mg NH4-N/L).

Influence of salinity on partial nitrification in a submerged biofilter.

Partial nitrification under various concentrations of NaCl (0-40 g/l) at a constant operational condition was investigated in a submerged biofilter reactor. The highest NO(2)-N/NO(x)-N ratio (0.76) was achieved at the NLR of 830 g NH(4)-N/m(3) day with salt free wastewater. Small increase the salt content led to higher activities and the NH(4)-N removal efficiency increased from 92% to 95% at 1 g/l NaCl concentration. Over this concentration, each NaCl addition provoked the NH(4)-N oxidation and a sharp increase of inhibition was observed. The total oxidized NH(4)-N was achieved at the nitrogen loading rate (NLR) and surface loading rate (SLR) of 0.754 kg/m(3)day and 3.23 g/m(2) day, respectively without salt in the feed wastewater and it was decreased to 0.322 kg/m(3) day and 1.38 g/m(2) day at the salinity of 40 g/l in the PNBR.

Influence of operational parameters and low nickel concentrations on partial nitrification in a submerged biofilter.

The effect of Ni(2+) concentrations on ammonium oxidation was studied in a batch and partial bionitrification reactor (PBNR). The nitrification rates up to the concentration of 0.1 mg Ni(2+)/l were close to those without Ni(2+). After testing the operational conditions in the PNBR, the highest NO(2)-N/NO( x )-N ratio was achieved at the DO concentrations of 2.0 mg/l and pH 9.00. The PNBR was operated at steady state (NH(4)-N loading rate and NO(2)-N/NO( x )-N ratio were 405 g m(-3) day(-1) and 0.74, respectively) before exposure to Ni(2+). The removal efficiency of NH(4)-N and NO(2)-N/NO( x )-N ratio in the effluent waters was increased by adding low concentrations of heavy metals to the PBNR. The average number of aerobic mesophilic bacteria at the biofilm surface and in the water in the void volume of PNBR were 1.0 × 10(4) CFU/g and 1.4 × 10(5) CFU/ml, respectively.

Ammonium oxidation via nitrite accumulation under limited oxygen concentration in sequencing batch reactors.

In this study, the effects of sludge retention time (SRT) on NH(4)-N oxidation and NO(x)-N accumulation in the nitritation reactors were studied. The gradually decrease of SRT also caused long reaction time to achieve 99% NH(4)-N removal. Although the target NH(4)-N removal was achieved in a short reaction time at 40 days of SRT, decreasing of SRT from 40 to 30, 25, 20 days, increase the reaction time from 168 to 240 and 265 h, respectively. The inlet NH(4)-N was almost oxidized and the concentration of NO(2)-N accumulated to a high level of 177 mg/l, while NO(2)-N/(NO(3)-N+NO(2)-N) ratio was about 0.9 at SRT of 40 days. However, the concentration of NO(3)-N increased slightly and NO(2)-N/(NO(x)-N) ratio dropped to 0.8 when the SRT was lower than 40 days. During the operation in a cycle, free ammonia concentration in the SBR was decreased from 2.8 to 0.7 mg/l which is below the lowest concentration causing inhibition of nitrite oxidizing bacteria (NOB). It was assumed that combined dissolved oxygen limitation and NH(3)-N inhibition on NOB caused NO(2)-N accumulation under the experimental conditions.

Nitritation and denitritation of ammonium-rich wastewater using fluidized-bed biofilm reactors.

Fluidized-bed biofilm nitritation and denitritation reactors (FBBNR and FBBDR) were operated to eliminate the high concentrations of nitrogen by nitritation and denitritation process. The dissolved oxygen (DO) concentration was varied from 1.5 to 2.5 g/m(3) at the top of the reactor throughout the experiment. NH(4)-N conversion and NO(2)-N accumulation in the nitritation reactor effluent was over 90 and 65%, respectively. The average NH(4)-N removal efficiency was 99.2 and 90.1% at the NLR of 0.9 and 1.2 kg NH(4)-N/m(3)day, respectively. Increasing the NLR from 1.1 to 1.2 kg NH(4)-N/m(3)day decreased the NH(4)-N elimination approximately two-fold while NH(4)-N conversion to NO(2)-N differences were negligible. The NO(2)-N/NO(x)-N ratios corresponded to 0.74, 0.73, 0.72, and 0.69, respectively, indicating the occurrence of partial nitrification. An average free ammonia concentration in the FBBNR was high enough to inhibit nitrite oxidizers selectively, and it seems to be a determining factor for NO(2)-N accumulation in the process. In the FBBDR, the NO(x)-N (NO(2)-N+NO(3)-N) concentrations supplied were between 227 and 330 mg N/l (NLR was between 0.08 and 0.4 kg/m(3)day) and the influent flow was increased as long as the total nitrogen removal was close to 90%. The NO(2)-N and NO(3)-N concentrations in the effluent were 3.0 and 0.9 mg/l at 0.08 kg/m(3)day loading rate. About 98% removal of NO(x)-N was achieved at the lowest NLR in the FBBDR. The FBBDR exhibited high nitrogen removal up to the NLR of 0.25 kg/m(3)day. The NO(x)-N effluent concentration never exceeded 15 mg/l. The total nitrogen removal efficiency in the FBBRs was higher than 93% at 21+/-1 degrees C.

Association of increased QTc dispersion and right ventricular hypertrophy.

BACKGROUND: There have been reports demonstrating an association between increased QT dispersion and ventricular arrhythmia in a variety of pathological cardiac conditions, including left ventricular hypertrophy. However, there are limited data about an association of right ventricular hypertrophy (RVH) and corrected QT (QTc) dispersion. MATERIAL/METHODS: Eighty-five persons who emigrated from a high-altitude region (2800-4200 m) of Afghanistan to Van, Turkey, (altitude: 1700-1800 m) 25 years ago were referred to our hospital for transthoracic examination between April 2003 and May 2007. RVH was detected in 37 of the persons, 12 of whom were not included in the study due to coexisting systemic hypertension, COPD, or pulmonary hypertension. Twenty-five individuals of the same population with normal echocardiographic findings were enrolled as the control group. Symptoms that may be consequent to arrhythmia (such as palpitation, dizziness, and syncope) were not reported by the study population. Twelve-lead electrography was performed to measure the heart rate, QTc intervals, and QTc dispersion values. RESULTS: The age and gender of both the patient and control groups were similar. There was no significant difference between patients and controls with respect to QTmax, QTmin, and heart rate. However, mean QTc dispersion values were significantly increased in patients with RVH compared with the control group (59.0+/-14.7 vs. 35.9+/-11.4 ms, p<0.001). CONCLUSIONS: Right ventricular hypertrophy is associated with an increase in QTc dispersion.

Biological denitrification of drinking water in a slow sand filter.

Biological removal of nitrate from drinking water was studied in a slow sand filter. Optimum carbon to nitrogen ratio (C/N) was found to be 1.8 when using acetic acid in batch tests. The filtration rates impact on NO(3)-N removal through the sand filter was assessed for 22.6 mgNO(3)-N/l concentrations while keeping C/N ratio as 1.8 for acetic acid. The filtration rates varied from 0.015, 0.02, 0.03, 0.04, 0.05, and 0.06 m/h, respectively, corresponding to an overall average NO(3)-N removal efficiency of 94%. Although increasing filtration rates decreased NO(3)-N removal, effluent NO(3)-N concentrations at the effluent port were lower than the limit value. The slow sand filter process was unable to provide NO(3)-N removal rate more than 27.1 gN/(m(2)day) (0.05 m/h flow rate). The NO(3)-N removal efficiency slightly dropped from 99% to 94% when the loading rate increased from 27.1 to 32.5 g/(m(2)day), but the effluent water contained higher concentration of NO(2)-N than the standard value.

The effects of short term (3 weeks) testosterone treatment on serum inflammatory markers in men undergoing coronary artery stenting.

OBJECTIVE: Inflammation markers can predict restenosis after successful intracoronary stenting. There is evidence that testosterone suppresses the expression of the inflammatory cytokines. We hypothesized that testosterone therapy after coronary stenting can reduce the inflammation markers. METHODS: We selected 41 men with coronary artery disease who underwent successful stent implantation for a >70% diameter stenosis of a major coronary artery. Patients, who had stable angina and positive exercise test results, were recruited after diagnostic coronary angiography. Twenty-five men were treated with 3 doses of i.m. testosterone administration once a week for 3 weeks following diagnostic angiography. Sixteen patients were recruited as a control group and they received standard therapy. First venous blood samples were obtained after angiography. Stents were implanted 3 weeks after diagnostic angiography. Second venous blood samples were taken 24 h after the coronary stenting. RESULTS: Baseline biochemical or hematological parameters were similar between the control and treatment groups. After coronary stenting, free testosterone, total testosterone, and sex hormone binding globulin were significantly elevated in the testosterone group (P<0.0001, P<0.0001 and P=0.02; respectively). After coronary stent implantation, there was a significant increase in IL-6 and CRP levels in the control group only (P=0.02 and P=0.038), while TNF-alpha levels were increased significantly in both groups (P=0.016 and P=0.014; respectively). Statistical analysis revealed that testosterone treatment prior to stent implantation attenuated IL-6 and hs-CRP levels significantly (P=0.042 and P=0.043; respectively). CONCLUSIONS: The present study shows that 3 weeks testosterone treatment prior to intracoronary stenting results in a significant suppression in hs-CRP and IL-6 levels after the stent implantation.

Simultaneous biological removal of endosulfan (alpha+beta) and nitrates from drinking waters using wheat straw as substrate.

Nitrate and endosulfan (alpha+beta) removal was studied in an upflow biological denitrification reactor packed with wheat straw as carbon source and support particles for microorganisms. While almost complete nitrate elimination and between 65% and 70% endosulfan (alpha+beta) elimination occurred when the temperature was higher than 20 degrees C; below that value, nitrate removal efficiency decreased to about 10%. Nitrate, dissolved organic carbon (DOC), and endosulfan (alpha+beta) removal efficiencies decreased considerably at 1500 microg/l endosulfan concentration in the batch experiments. Although a high removal efficiency was observed for endosulfan (alpha+beta) and nitrate in the biological denitrification continuous reactor, the effluent water could not be used for drinking purpose because of the unacceptable levels of endosulfan (alpha+beta), colour and dissolved organic content. During the continuous study, 23.4% of the initial weight of wheat straw was lost and 24 g was consumed per gram of nitrogen removed. The results of the continuous study showed that 21.3% of the endosulfan removal was achieved by adsorption onto the wheat straw and 68.2% of the endosulfan removal occurred by biological activity and the remaining portion was detected in the effluent water.