Simultaneous phosphate and CODcr removals for landfill leachate using modified honeycomb cinders as an adsorbent.

In this study, honeycomb cinders were employed to remove phosphate and Chemical Oxygen Demand (COD(cr)) simultaneously for landfill leachate treatment. Operating conditions of honeycomb cinders pretreatment, pH, temperature, honeycomb cinders dosage, reaction time, and settling time, were evaluated and optimized. The results revealed that the removal efficiencies of both phosphate and COD(cr) could be increased up to 99.9% and 66.7% under the optimal conditions, respectively. Moreover, the structures of raw/modified honeycomb cinders and resulting precipitates were detected by Scanning Electron Microscope (SEM), Energy Dispersive Spectrometers (EDS) analysis and X-ray Diffraction (XRD). The results suggested that the adsorption method using honeycomb cinders might be an effective strategy as a pretreatment technology for landfill leachate treatment.

[Enrichment and dynamic analysis of deammonification granules].

Deammonification process was started-up in a sequencing batch reactor (SBR) seeded with anaerobic granular sludge. A kinetic model describing deammonification process was proposed. Due to the presence of concentration gradient of dissolved oxygen (DO) in granular sludge, model correction factors of DO were introduced. The influences of denitrification process, nitrite and DO on granular sludge activity were studied by model and good agreement was obtained between the experimental results and simulation results. Heterotrophic denitrifiers has some influence on the ANAMMOX process during the initial cultivation, and the influence decreases gradually during the following operation period. When nitrite concentration is 20-30 mg/L, a total nitrogen removal efficiency begins to drop caused by inhibition of nitrite. With high or low DO concentration, the activity of deammonification is inhibited. A total nitrogen removal efficiency can simultaneously reach higher levels by controlling appropriate DO related NH4(+) -N concentration of inflow. In a NH4(+) -N concentration of 80 mg/L, the optimal DO level for a maximal nitrogen gas production is at 0.3-0.6 mg/L.

[Cultivation and nitrogen removal characteristics of deammonifition granules].

An SBR reactor seeded with anaerobic granular sludge was started up to enrich deammonifition bacteria and investigate its nitrogen removal characteristics. Research results showed that deammonification granular sludge could be cultivated successfully with firstly enriched ANAMMOX microorganisms in anaerobic condition and then controlled the dissolved oxygen in the SBR reactor between 0.3 and 0.5 mg/L, in which the maximum total nitrogen removal rate reach 75.3%. When the Ca and P concentrations of the medium exceeded the necessary quantity, salt precipitation was observed and interfered with microbial activity and caused a decrease of the nitrogen removal rate of the reactor system. Salt precipitation was avoided by diminishing adequately the Ca and P concentrations of the medium during the following operation period, and the total nitrogen removal rate restored.

[Biological phosphorus removal in sequencing batch reactor without anaerobic phase].

The performance of phosphorus removal with a sequencing batch reactor was investigated by simulated municipal wastewater. The experimental results showed that phosphorus removal could be achieved in sequencing batch reactor without anaerobic phase, which was conventionally considered as a key phase for phosphorus removal. Phosphorus concentration in the effluent was 1.0 mg x L(-1) below after 4 h aeration, during which pH was 7.0 +/- 0.2. Which indicated the removal rate of phosphorus was above 90% when the COD and phosphorus concentrationof influent were about 400 mg x L(-1), 15-20 mg x L(-1), respectively. Intracellular storage of poly-phosphate (poly-P) was increasing in the aeration after decreasing in first hour aeration (the content of poly-P was 83.034 mg x g(-1) at the beginning of aerobic phase, 79.980 mg x g(-1) in first aeration and 83.086 mg x g(-1) in end), but the energy storage poly-beta-hydroxyalkanoates (PHA) was constant nearly and the content was very low (PHA concentration was about 5 mg x L(-1)). The researches indicated that phosphate could be transformed to poly-P by poly-phosphate-accumulating organisms without anaerobic zone and PHA, biological phosphorus removal was obtained by removing sludge with rich phosphorus, and this phenomenon could not be explained by conventional theory.

Total concentrations and speciation of heavy metals in municipal sludge from Changsha, Zhuzhou and Xiangtan in middle-south region of China.

The presence of heavy metals in municipal sludge restricts its use for agricultural purposes. In this paper, the bioavailability and eco-toxicity of heavy metals in municipal sludge was evaluated, taking into consideration both the speciation of metals and the local environmental characteristics. The dewatered municipal sludge samples were collected from five sewage plants in Changsha, Zhuzhou and Xiangtan respectively, which are representative cities with characteristics of the middle-south region of China. Some agricultural significant parameters and total metal concentrations in the sludge were determined and the metal speciation was studied by using BCR sequential extraction procedure. It was found experimentally that in general the municipal sludge collected from the five sewage plants was rich in organics, N and P. Except that the sludge from Xia Wan Sewage Treatment Plant showed higher concentrations of heavy metals, the sludge from other plants all showed a low total content of heavy metals with only Cd slightly exceeding the permitted values of the national application standard of acid soil in China (GB18918-2002). The sequential extraction results showed that Cu and Zn were principally distributed in the oxidizable fraction, which meant a high potential toxicity, but the bioavailability of Zn might be overestimated to the soil of Hunan. Pb was mainly in the residual fraction. The distribution of Cd showed no obvious characteristics.

Kinetic studies for the biosorption of lead and copper ions by Penicillium simplicissimum immobilized within loofa sponge.

Biosorption potential of Penicillium simplicissimum (Penicillium sp.) immobilized within loofa sponge (PSILS) for lead and copper from aqueous media was explored. The effects of pH, contact time and initial concentration were studied in batch experiments. The maximum uptake of metal ions was obtained at pH 5.0. Biosorption equilibrium was established by 60 min. The pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models were applied to study the kinetics of the biosorption processes. The pseudo-second-order kinetic model provided the best correlation (R(2)>0.999) of the experimental data compared to the pseudo-first-order and intraparticle diffusion kinetic models. The maximum heavy metal ions adsorbed was found to be 152.6 and 112.3mg/g for Pb(II) and Cu(II), respectively. It was found that the biosorption of both Pb(II) and Cu(II) on PSILS was correlated well (R(Pb)(2)=0.999 and R(Cu)(2)=0.9978) with the Langmuir equation as compared to Freundlich isotherm equation under the concentration range studied. PSILS was regenerated by washing with a 100mM solution of HCl. The desorption efficiency was as high as 98%. The PSILS was reused in five adsorption-desorption cycles with negligible decrease in biosorption capacity. The present work showed that PSILS was an efficient biosorbent for removal of heavy metal ions from aqueous solution.

Biological phosphorus removal in sequencing batch reactor with single-stage oxic process.

The performance of biological phosphorus removal (BPR) in a sequencing batch reactor (SBR) with single-stage oxic process was investigated using simulated municipal wastewater. The experimental results showed that BPR could be achieved in a SBR without anaerobic phase, which was conventionally considered as a key phase for BPR. Phosphorus (P) concentration 0.22-1.79 mg L(-1) in effluent can be obtained after 4h aeration when P concentration in influent was about 15-20 mg L(-1), the dissolved oxygen (DO) was controlled at 3+/-0.2 mg L(-1) during aerobic phase and pH was maintained 7+/-0.1, which indicated the efficiencies of P removal were achieved 90% above. Experimental results also showed that P was mainly stored in the form of intracellular storage of polyphosphate (poly-P), and about 207.235 mg phosphates have been removed by the discharge of rich-phosphorus sludge for each SBR cycle. However, the energy storage poly-beta-hydroxyalkanoates (PHA) was almost kept constant at a low level (5-6 mg L(-1)) during the process. Those results showed that phosphate could be transformed to poly-P with single-stage oxic process without PHA accumulation, and BPR could be realized in net phosphate removal.

Impacts of sterilization, microwave and ultrasonication pretreatment on hydrogen producing using waste sludge.

Hydrogen production by sterilization, microwave and ultrasonication pretreated waste sludge was investigated in this study. A new strain of Pseudomonas sp. GZ1 (EF551040) was inoculated in pretreated waste sludge to produce hydrogen. The experimental results showed that different pretreated sludge had evident differences in the yield of hydrogen production and lag time. Sterilized sludge had the largest yield of hydrogen production, and the maximum yield was 15.02 ml/gTCOD. The lag time of using sterilized sludge was 15 h, longer than other two pretreated sludge. Using the ultrasonicated sludge, the hydrogen production yield was smallest and lag time was shortest in the three pretreated sludge. Protein and carbohydrate could be released from waste sludge by pretreatment. Protein was the main nutrient used for hydrogen production. The concentration of protein, carbohydrate and SCOD increased after pretreatment and fermentation. The impacts of different pretreatments on hydrogen production were also discussed in detail.

Screening and characterization of a bioflocculant produced by Aeromonas sp.

OBJECTIVE: To isolate the bioflocculant-producing bacteria from activated sludge and investigate the flocculating characteristics of the newly isolated bioflocculant. METHODS: Bacteria were screened from activated sludge samples to isolate bioflocculant-producing bacteria. Flocculating activity was used as a measure of the flocculating capability of the bioflocculant. RESULTS: A novel bioflocculant-producing bacterium was isolated, which was identified to belong to genus Aeromonas and named as Aeromonas sp. N11. Flocculating activity increased in the presence of K+, Na+, or Ca2+. The highest flocculating activities for kaolin suspension were obtained in acidic pH ranges, and optimum pHs for it were 3.0, 4.0, and 5.0 with 1 mmol/L K+, Ca+, and Na+ present, respectively. The highest flocculating activities for soil suspension were observed at pH 8.0. The bioflocculant had a good flocculating activity and could achieve a flocculating activity of 92.4% for kaolin suspension at a dosage of only 1 mgxL(-1), and its activity in kaolin suspension was decreased by only 9.2% after heating at 100 degrees C for 60 min. CONCLUSION: The bioflocculant produced by Aeromonas sp. N11 has strong flocculating activity and high stability, which affords high possibility of its practical use.

[Cultivation and nitrogen removal characteristics of ANAMMOX granules].

An SBR reactor seeded with anaerobic granular sludge was started-up to enrich ANAMMOX (anaerobic ammonia oxidation) bacteria and investigate its nitrogen removal characteristics. Research results showed that hydraulic retention time (HRT) was the most important factor to enrich ANAMMOX bacteria. When the HRT was controlled at 30 d during the initial cultivation, the SBR reactor presented ANAMMOX activity at t = 58 days. Simultaneously, the anaerobic granular sludge changed gradually from dust black to brownish color and its diameter became smaller. At t = 90 days, the ANAMMOX was obvious, and ANAMMOX granules was cultivated successfully. NH4(+) -N and NO2(-) -N were removed simultaneously with higher speed and maximum removal rate reached 14.6 g/(m3 x d) and 6.67 g/(m3 x d) respectively. Between t = 110 days and t = 156 days, the nitrogen load was increased gradually to a hydraulic retention time of 5 days. The removal rate of ammonium and nitrite were 60.6% and 62.5% respectively. The ratio of nitrite/ammonium was 1.12. The sludge changed to henna and formed ANAMMOX granulation with high nitrogen removal activity. The total nitrogen load was 34.3 g/(m3 x d).

[Simultaneous nitrogen and phosphorus removal in the reactor of inner loop SBR without anaerobic phase].

The performance of simultaneous nitrogen and phosphorus removal with an inner loop sequencing batch reactor were investigated by simulated municipal wastewater. The experimental results showed that COD, NH4(+) -N, and TP can be removed efficiently after four hours aeration, during which dissolved oxygen concentration was at 6 mg/L at the beginning of aerobic phase and pH was in the rang of 7 - 8. The COD and NH4+ -N as well as TP concentration in the effluent were about at 4 - 48 mg x L(1), 0 - 2.0 mg x L(-1), and 0 - 1.4 mg x L(-1) respectively, which indicated the removal rate for each item were about 89.7% +/- 6.5%, 97.4% +/- 3.6%, 95.6% +/- 4.4% when the concentration of influent were about 170 - 260 mg x L(-1), 20 - 30 mg- L(-1), 8 - 20 mg L(-1), respectively. The removal rate of TIN( NH4 -N + NO3(-) -N + NO2(-) -N) was also reached about 70%. It was found during the research process that phosphorus removal can be achieved without anaerobic phase, which was conventionally considered as a key phase for phosphorus removal, and this phenomena can not be explained by traditional theory.

[Nitritation-ANAMMOX process for treatment of ammonium rich wastewater].

Combination of a nitritation process and anoxic ammonium oxidation (ANAMMOX) process for the treatment of ammonia rich influents is evaluated. Herein the combined process was studied with manmade synthetic wastewater. Research results show that when the hydraulic retention time (HRT) was I day, the nitritation activity was stable and the influent ammonium concentration has little effect on it. When the influent ammonium concentration is 400-600 mg/L, the effluent nitrite concentration is always between 260 mg/L and 280 mg/L, so the effluent nitrite/ammonium ratio can be adjust by control the influent ammonium concentration. The total nitrogen elimination was depended strongly on the nitrite/ammonium ratio in the inlet of the ANAMMOX reactor. When the inlet ammonium was 480 mg/L of the combined process, the nitrite/ammonium ratio of the nitritation process was about 1.2, the total nitrogen elimination was 84%.