Enhanced biological nutrient removal by the alliance of a heterotrophic nitrifying strain with a nitrogen removing ecosystem

Nitrogen removal from synthetic wastewater was investigated in an airlift bioreactor （ALB）, augmented with a novel heterotrophic nitrifier Pseudonocardia ammonioxydans H9^T under organic carbon to nitrogen ratios （Corg/N） ranging from 0 to 12. Effect of the inoculated strain was also determined on the settling properties and the removal of chemical oxygen demand （COD）. Two laboratory scale reactors were set up to achieve a stable nitrifying state under the same physicochemical conditions of hydraulic retention time （HRT）, temperature, pH and dissolved oxygen （DO）, and operated under the sequencing batch mode. The level of DO was kept at 0.5- 1.5 mg/L by periodic stirring and aeration. Each specific Corg/N ratio was continued for duration of 3 weeks. One of the reactors （BR2） was inoculated with P ammonioxydans H9^T periodically at the start of each Corg/N ratio. Sludge volumetric index （SVI） improved with the increasing Corg/N ratio, but no significant difference was detected between the two reactors. BR2 showed higher levels of nitrogen removal with the increasing heterotrophic conditions, and the ammonia removal reached to the level of 82%-88%, up to10% higher than that in the control reactor （BR1） at Corg/N ratios higher than 6; however, the ammonia removal level in experimental reactor was up to 8% lower than that in control reactor at Corg/N ratios lower than 2. The COD removal efficiency progressively increased with the increasing Corg/N ratios in both of the reactors. The COD removal percentage up to peak values of 88%-94% in BR2, up to 11% higher than that in BR1 at Corg/N ratio higher than 4. The peak values of ammonia and COD removal almost coincided with the highest number （18%-27% to total bacterial number） of the exogenous bacterium in the BR2, detected as colony forming units （CFU）. Furthermore, the removal of ammonia and COD in BR2 was closely related to the number of the inoculated strain with a coefficient index （R2） up to 0.82 and 0.85 for ammonia and COD, respectively. These results suggest that it was more efficient for both the ammonia and carbon nutrient removals in a reactor inoculated with a heterotrophic nitrifier at high Corg/N ratio, inferring that the heterotrophic nitrifers would be practically more available in the treatment of wastewater with high level of ammonia and COD.

Micro-electrolysis technology for industrial wastewater treatment

Experiments were conducted to study the role of micro-electrolysis in removing chromaticity and COD and improving the biodegradability of wastewater from pharmaceutical, dye-printing and papermaking plants. Results showed that the use of micro-electrolysis technology could remove more than 90% of chromaticity and more than 50% of COD and greatly improved the biodegradability of pharmaceutical wastewater. Lower initial pH could be advantageous to the removal of chromaticity. A retention time of 30 minutes was recommended for the process design of micro-electrolysis. For the use of micro-electrolysis in treatment of dye-printing wastewater, the removal rates of both chromaticity and COD were increased from neutral condition to acid condition for disperse blue wastewater; more than 90% of chromaticity and more than 50% of COD could be removed in neutral condition for vital red wastewater.

Dyeing and printing wastewater treatment using fly-ash coated with chitosan

Printing and dyeing industry is a considerable source of environmental contamination. In this study treatment of printing and dyeing wastewater with a new type of sewage treatment agent, fly-ash coated with chitosan particles （FCCP）, was examined. The effects ofpH, stirring time, sedimentation time and temperature on color, COD, turbidity and NH3-N removal were determined. The optimum dosage of FCCP and the influence of individual factors on removal efficiency were tested. The optimum parameters determined using the L16 （45） orthogonal experiment were as follows： FCCP （weight ratio of chitosan to fly-ash 1：6） dosage, 4 g.L^-1; temperature, 35℃; pH, 4. The stirring time and sedimentation time were 20 min and 5 h, respectively. Under these optimum conditions, the color, COD and NH3-N removal ratios were 97%, 80% and 75%, respectively.

Fenton treatment of olive oil mill wastewater—applicability of the method and parameters effects on the degradation process

The low biodegradability of polyphenolic compounds typically found in olive processing indicated that biological treatment is not always successful in the treatment of olive oil mill wastewater in term of COD removal. In this study the results of investigations on the applicability of Fenton's reagent in the treatment of this effluent were discussed. The efficiency of this method was determined. 86 % of removal COD was obtained using 5 mol H 2O 2 and 0.4 mol Fe 2+ per liter of crude OMW. The main parameters that govern the complex reactive system, i.e., time, pH, [H 2O 2] and [Fe(II)] were studied.

Effect and Cost Research for Leachate Treatment in PAC/Fenton and Fenton/PAC Technology

To compare the treatment effects and the costs of coagulation/Fenton process and Fenton/coagulation process in leachate treatment,fresh and old leachates were respestively treated with these two techniques.The experimental results indicate that the highest chemical oxygen demand(COD)removal rate of Fenton reaction on leachate can be acquired under the conditions of pH=3.5,nH2O2/nFe2+=6,mH2O2/mCOD=3,and reaction time=4 h.Polyaluminium chloride(PAC)coagulation has the highest COD removal rate on leachate under the condition of mPAC/mCOD=0.6.Under the optimum reaction conditions,coagulation/Fenton and Fenton/coagulation processes were respestively adopted to treat raw leachate.The data also show that COD removal rate of coagulation/Fenton process on fresh and old leachates are 90.56% and 86.52% respectively and that of Fenton/coagulation process 89.99% and 85.99%,so there is no obvious difference.But the cost of coagulation/Fenton process for leachate treatment is RMB 62.6,lower than that of Fenton/coagulation process.Therefore,coagulation/Fenton process is more optimized than Fenton/coagulation process for leachate treatment.

Wet Air Oxidation of Organic Wastewater Catalyzed by Doped Ceria

The catalytic wet air oxidation (CWAO) of H acid and phenol was investigated in the presence of Cu or Fe doped CeOsolid solutions, which were obtained by sol-gel method. The experiment results showed that the incorporation of Cu or Fe into the fluorite lattice of CeOstrongly enhanced the oxidation activity of the catalyst. At 90 ℃ and 0.1 MPa, H acid conversion was 70% for the Ce0.9Fe0.1O2-δ and 60% for the Ce0.9Cu0.1O2-δ catalyst. For phenol removal, the conversion was 70% for the Ce0.9Cu0.1O2-δ catalyst, while for the Ce0.9Fe0.1O2-δ the conversion was 30%. The results indicated that Ce0.9Cu0.1O2-δ was suitable for the treatment of organic wastewaters while Ce0.9Fe0.1O2-δ was suitable for the removal of H acid. The 70% phenol removal rate with Ce0.9Cu0.1O2-δ catalyst was markedly increased to 90% with Ce0.8Cu0.2O2-δ catalyst. However, the phenol removal reduced from 30% to 15% with Fe content increasing from 10% to 20%. For the H acid, the increase of the content of Cu or Fe tended to obviously increase the original reaction rate while the COD removal changed little.

Treatment of Wastewater with Modified Sequencing Batch Biofilm Reactor Technology

This paper describes the removal of COD and nitrogen from wastewater with modified sequencing batch biofilm reactor. The strategy of simultaneous feeding and draining was explored.The results show that introduction of a new batch of wastewater and withdrawal of the purified water can be conducted simultaneously with the maximum volumetric exchange rate of about 70%.Application of this feeding and draining mode leads to the reduction of the cycle time, the increase of the utilization of the reactor volume and the simplification of the reactor structure. The treatment of a synthetic wastewater containing COD and nitrogen was investigated. The operation mode of F(D) O ( i.e ., simultaneous feeding and draining followed by the aerobic condition) was adopted. It was found that COD was degraded very fast in the initial reaction period of time, then reduced slowly and the ammonia nitrogen and nitrate nitrogen concentrations decreased and increased with time respectively, while the nitrite nitrogen level increased first and then reduced. The relationship between the COD or ammonia nitrogen loading and its removal rate was examined, and the removal of COD, ammonia nitrogen and total nitrogen could exceed 95%, 90% and 80% respectively. The fact that nitrogen could be removed more completely under constant aeration (aerobic condition) of the SBBR operation mode is very interesting and could be explained in several respects.

Process Optimization on Anaerobic Treatment of Citric Acid Wastewater

[Objective] The aim was to obtain higher COD removal rate so as to guide the process of citric acid industrial wastewater. [Method] The effects of controllable factors, acidification time, hydraulic retention time, and influent COD concentration, in-anaerobic treatment process of citric acid wastewater on COD removal rate were studied and the COD removal rate was optimized by response surface method. [Result] There was no interaction between acidification time and the other two factors. It was showed that hydraulic retention time and influent COD concentration had significant effect on COD removal rate and there was interaction between the two factors. The optimum COD removing process conditions was as follows: acidification time 1.53 h, hydraulic retention time 3.52 h and influent COD concentration 2 698 mg/L. Under the optimized conditions, the COD removal rate was 93.31% and it was much closed to the experimental result, 93.29%. [Conclusion] Using response surface method to optimize the anaerobic treatment of citric acid wastewater can result in optimized achievement.

Photoelectrocatalytic degradation of high COD dipterex pesticide by using TiO_2 /Ni photo electrode

A TiO2 thin film electrode deposited on porous nickel net （TiO2/Ni） was prepared by the sol-gel method, and the surface morphology, crystal structure features and the grain size were characterized by Field emission scan electron microscopy （FESEM） and X-ray diffraction （XRD）. The photoelectrocatalytic system was set up using a UV high-pressure mercury lamp as the light source, TiO2 coated on foamed nickel as photo anode, Pt sheet as counter electrode and the pesticide dipterex in synthetic wastewater. Various factors that influence the photoelectrocatalytic decomposition of dipterex pesticide have been studied, such as degradation time, the type of electrolyte, current density, original pH value and different degradation methods. The prepared catalysts were employed to photoelectrocatalytically degrade the pesticide dipterex under UV irradiation, comparing the results with photocatalytic degradation and electrochemical oxidation. The results indicated that under the optimal conditions of 0.02 mol/L NaC1 as the supporting electrolyte, current density = 2.5 mA/cm^2, pH 6.0 and dipterex pesticide 40 mg/L, and reaction time 2 hr, dipterex chemical oxygen demand （COD） removal rate and organophosphorous conversion of up to 82.6% and 83.5% were achieved, respectively. The method of photoelectrocatalytic degradation is more efficient than photocatalysis and electrochemical oxidation. The possible roles of the electrolytes on the reactions and probable mechanisms were also discussed.

Electricity generation and brewery wastewater treatment from sequential anode-cathode microbial fuel cell

A sequential anode-cathode double-chamber microbial fuel cell （MFC）, in which the effluent of anode chamber was used as a continuous feed for an aerated cathode chamber, was constructed in this experiment to investigate the performance of brewery wastewater treatment in conjugation with electricity generation. Carbon fiber was used as anode and plain carbon felt with biofilm as cathode. When hydraulic retention time （HRT） was 14.7 h, a relatively high chemical oxygen demand （COD） removal efficiency of 91.7%-95.7% was achieved under long-term stable operation. The MFC displayed an open circuit voltage of 0.434 V and a maximum power density of 830 mW/m^3 at an external resistance of 300 0. To estimate the electrochemical performance of the MFC, electrochemical measurements were carried out and showed that polarization resistance of anode was the major limiting factor in the MFC. Since a high COD removal efficiency was achieved, we conclude that the sequential anode-cathode MFC constructed with bio-cathode in this experiment could provide a new approach for brewery wastewater treatment.

Treatment of coking wastewater by a novel electric assisted micro-electrolysis filter

A newly designed electric assisted micro-electrolysis filter（E-ME） was developed to investigate its degradation efficiency for coking wastewater and correlated characteristics. The performance of the E-ME system was compared with separate electrolysis（SE） and micro-electrolysis（ME） systems. The results showed a prominent synergistic effect on COD removal in E-ME systems. Gas chromatography/mass spectrometry（GC–MS） analysis confirmed that the applied electric field enhanced the degradation of phenolic compounds.Meanwhile, more biodegradable oxygen-bearing compounds were detected. SEM images of granular activated carbon（GAC） showed that inactivation and blocking were inhibited during the E-ME process. The effects of applied voltage and initial p H in E-ME systems were also studied. The best voltage value was 1 V, but synergistic effects existed even with lower applied voltage. E-ME systems exhibited some p H buffering capacity and attained the best efficiency in neutral media, which means that there is no need to adjust p H prior to or during the treatment process. Therefore, E-ME systems were confirmed as a promising technology for treatment of coking wastewater and other refractory wastewater.

Enhancing nitrogen removal from low carbon to nitrogen ratio wastewater by using a novel sequencing batch biofilm reactor

Removing nitrogen from wastewater with low chemical oxygen demand/total nitrogen （COD/TN） ratio is a difficult task due to the insufficient carbon source available for denitrification. Therefore, in the present work, a novel sequencing batch biofilm reactor （NSBBR） was developed to enhance the nitrogen removal from wastewater with low COD/ TN ratio. The NSBBR was divided into two units separated by a vertical clapboard. Alternate feeding and aeration was performed in the two units, which created an anoxie unit with rich substrate content and an aeration unit deficient in substrate simultaneously. Therefore, the utilization of the influent carbon source for denitrification was increased, leading to higher TN removal compared to conventional SBBR （CSBBR） operation. The results show that the CSBBR removed up to 76.8%, 44.5% and 10.4% of TN, respectively, at three tested COD/TN ratios （9.0, 4.8 and 2.5）. In contrast, the TN removal of the NSBBR could reach 81.9%, 60.5% and 26.6%, respectively, at the corresponding COD/TN ratios. Therefore, better TN removal performance could be achieved in the NSBBR, especially at low CODfrN ratios （4.8 and 2.5）. Furthermore, it is easy to upgrade a CSBBR into an NSBBR in practice.