Study of Biological Activity and Process Stability in Submerged Membrane Bioreactors

Synthetic wastewater was treated in a bench scale submerged membrane bioreactor (SMBR). A long‐term experiment was conducted by varying the sludge residence time (SRT) (10–500 d) and BOD loading (1.3–0.25 kg/m³·d). The biological activity was observed in terms of the oxygen utilization rate (OUR) and adenosine triphosphate (ATP) profile; the process stability was analyzed based on the extent of organic degradation and suction pressure. The microbial population in the SMBR was dependent on the SRT and BOD loading, and its biological activity was increased with an increase in the SRT or BOD loading. At a low feed to microorganism (F/M) ratio (0.06 kg BOD/kg MLSS·d), the sludge production of the reactor was reduced to 0.04 kg MLSS/kg BOD, which is much less than in the conventional activated sludge process (0.4–0.6 kg MLSS/kg BOD). The F/M ratio influenced the biological activity (via ATP and the OUR) significantly at a short SRT (≤90 d). However, the effect of the F/M ratio ceased at a low F/M ratio (≤ 0.07 kg BOD/kg MLSS·d). The accumulation of organics in the SMBR was accompanied with an increase in the supernatant TOC, which caused a high suction pressure and an abrupt change in the operating conditions to process instability. However, the process stability of the SMBR increased with an increase in the SRT and a decrease in the BOD loading along with a concomitant decrease in the biological activity and sludge production.     

Influence of Nitrate and Sulfate on the Anaerobic Treatment of Pharmaceutical Wastewater

Anaerobic treatment of wastewater from the pharmaceutical industry, which contained about 3.2 g/L of sulfate, was carried out in an Upflow Anaerobic Sludge Blanket (UASB) reactor. After a startup period of 120 days, a chemical oxygen demand (COD) removal efficiency of more than 90 % was obtained along with an organic loading rate (OLR) of 1.5 g COD/(L day). During the same period, the sulfate removal was about 90 %. However, the performance of the reactor was affected when the loading rate was increased to 2.09 g COD/(L day). It was found that the accumulation of sulfides, combined with a decrease in the pH, affected the reactor performance. In batch reactor studies with pharmaceutical wastewater it was observed that methane production began only after the initiation of nitrate consumption. The denitrification process can inhibit sulfate reduction at high nitrate concentrations, but compared to reactors without nitrate, the sulfate reduction process and sulfide formation were quickly initiated at low nitrate concentrations. The methanogenic activity was however affected by the presence of more than 2 g/L of sulfate.     

Improvement of Process Stability of Microbiological Quinoline Degradation in a Three‐Phase Fluidized Bed Reactor

The biological degradation of quinoline by suspended and immobilized Comamonas acidovorans was studied under continuous and discontinuous operating conditions in a three‐phase fluidized bed reactor. C. acidovorans degrades quinoline into biomass and carbon dioxide. Quinoline and the intermediates of its metabolic pathway are found only by quinoline shockloads. The continuous degradation of quinoline by suspended biomass was only possible, if the dilution rate was less than the growth rate (μ_max =0.42 h^–1) and the concentration of a shockload was less than 1 kg/m³. A concentration greater than 1 kg/m³ led to an irreversible damage of the cells. Hence, two different carrier materials were used for immobilization by attachment, to increase the stability of the process. Using immobilization of biomass on carriers decouples the hydrodynamic retention time and the growth rate of the microorganisms. A comparison of the carrier material showed no differences with respect of activity and stability of the biofilm. The process stability of a three‐phase fluidized bed reactor was increased by immobilized biomass. The degradation of toxic shockloads was only possible with immobilized biomass. A dynamic model has been developed to describe the concentration profile of quinoline, 2‐hydroxyquinoline as metabolite and the suspended biomass. A comparison of the measured and calculated values showed good agreement.     

Protective Effect of Immobilized Ammonia Oxidizers and Phenol‐degrading Bacteria on Nitrification in Ammonia– and Phenol‐containing Wastewater

Phenol present in wastewaters from various industries has an inhibitory effect on nitrification even at low concentrations. Hence, the biological treatment of wastewater containing both phenol and ammonia involves a series of treatment steps. It is difficult to achieve nitrification capability in an activated sludge system that contains phenol at concentrations above the inhibitory level. Batch treatment of wastewater containing various concentrations of phenol showed that the ammonia oxidation capability of suspended Nitrosomonas europaea cells, an ammonia oxidizer, was completely inhibited in the presence of more than 5.0 mg/L phenol. To protect the ammonia oxidizer from the inhibitory effect of phenol and to achieve ammonia oxidation capability in the wastewater containing phenol at concentrations above the inhibitory level, a simple bacterial consortium composed of an ammonia oxidizer (N. europaea) and a phenol‐degrading bacterial strain (Acinetobacter sp.) was used. Ammonia oxidation did not occur in the presence of phenol at concentrations above the inhibitory level when suspended or immobilized N. europaea and Acinetobacter sp. cells were used in batch treatment. Following the acclimatization of the immobilized cells, accumulation of nitrite was observed, even when the wastewater contained phenol at concentrations above the inhibitory level. These results showed that immobilization was effective in protecting N. europaea cells from the inhibitory effect of phenol present in the wastewater.     

A Model for the Biofiltration of Butyl Acetate and Xylene Mixtures by a Trickle‐Bed Air Biofilter

A mathematical model that incorporates the rates of the mass transfer process and the biofilm reaction is presented to predict the performance of a trickle‐bed air biofilter (TBAB) for treating butyl acetate and xylene mixtures. A thorough understanding of the factors that influence these rates is necessary before the practical application of a TBAB for treating many kinds of pure and mixed volatile organic compounds (VOC) in the air stream. The model presented consists of a set of mass balance equations for butyl acetate, xylene and oxygen in the bulk gas phase and within the biofilm. The butyl acetate and xylene concentration profiles of the gas phase predicted by the model were in good agreement with the measured data documented in a previous study. The most relevant parameters were evaluated in a sensitivity analysis to determine their respective effects on the model performance. Four parameters were identified to strongly influence the model performance, the surface area of the biofilm per volume unit of the packing material (A_S), the empty‐bed residence time (EBRT), the maximum specific growth rate of the microorganism (μ_m), and the microbial yield coefficient (Y). The practical application of the model to derive the performance equation is also presented and discussed. This equation makes it possible to simultaneously obtain a relatively high VOC removal efficiency and to minimize the capital cost.     

Nitrogen-removal bioreactor capable of simultaneous nitrification and denitrification for application to industrial wastewater treatment

A bioreactor system with 30 packed gel envelopes was installed in a thermal power plant for the removal of nitrogen from ammonia-containing desulfurization wastewater. Each envelope consisted of double-sided plate gels containing Nitrosomonas europaea and Paracoccus denitrificans cells with an internal space in between for injecting an electron donor. The envelope can remove ammonia from wastewater in a single step. When the wastewater was continuously treated with the bioreactor system, it removed 95.0% of the total nitrogen in the inlet, and the total nitrogen concentration in the outlet was below 9.0 mg L⁻¹. The maximum nitrogen removal rate was 6.0 g day⁻¹ per square meter of the gel area. The maximum utilization efficiency of the injected ethanol for denitrification was 98.4%, and the total organic carbon concentration in the outflow was maintained at a low level. Since the bioreactor system could use the electron donor effectively, it was not necessary to use an additional aerobic tank to remove the electron donor and a settling tank to segregate the surplus sludge containing bacteria from wastewater. Our concept of using packed gel envelopes would be highly effective for constructing a simple and efficient nitrogen removal system capable of simultaneous nitrification and denitrification.     

The Role of the Liquid Phase in the Degradation of Toluene and m‐Cresol within a Biofilm Trickle‐Bed Reactor

The degradation of toluene and m‐cresol in a biofilm trickle‐bed reactor was experimentally and theoretically investigated. Degradation is the result of the cooperation between suspended and immobilized microorganisms in the trickling film and the biofilm. The role of the trickling film is that of a barrier for mass transfer to the biofilm or that of an additional reaction space. This is the result of physical availability of pollutants to the liquid phase as well as co‐substrate degradation of inherent biomass. An instationary reactor balance model is presented. In addition to this the change in wetting behavior of carrier surface due to biofilm formation is discussed. A partial wetting of biofilm surface by rivulets of the trickling film is proposed. The model was verified by experimental data. The different reactor operation modes denoted as biofilm regime versus trickling film regime for the chosen pollutant system were expressed in terms of dimensionless reactions and transfer numbers. It is shown that the volumetric reaction rates for toluene in a trickling film regime reaches values twice as high as that of a biofilm regime due to the presence of the second substrate m‐cresol. The limiting step in both cases is the mass transfer of oxygen to bacteria in the biofilm or trickling film.     

Investigating the performance of an up-flow anoxic fixed-bed bioreactor and a sequencing anoxic batch reactor for the biodegradation of hydrocarbons in petroleum-contaminated saline water

This work presents the biodegradation of petroleum hydrocarbons in an upflow anoxic fixed-bed bioreactor (UAnFB) and a sequencing anoxic batch reactor (SAnBR). The performances of the UAnFB and the SAnBR in the removal of petroleum hydrocarbons (TPH) were investigated as a function of inlet concentration at a hydraulic retention time of 24 h. The UAnFB had higher robustness and adapted better towards the transition in TPH concentration. The average TPH removal rates for concentrations of 950, 1450, and 2500 mg L⁻¹ were 99.9%, 99.6%, and 93.7%, respectively, for the UAnFB and 99.7%, 98.5%, and 87.7%, respectively, for the SAnBR. The highest rates of TPH biodegradation at a loading rate of 104 g m⁻³ h⁻¹ in the UAnFB and the SAnBR were 97.5 and 91.3 g m⁻³ h⁻¹, respectively. The UAnFB was more efficient than the SAnBR in biodegrading aromatic hydrocarbons. Accordingly, the UAnFB is an efficient and viable technology for the treatment of hydrocarbon-laden streams.     

Development of 16S rRNA-Gene-Targeted Group-Specific Primers for the Detection and Identification of Predominant Bacteria in Human Feces

For the detection and identification of predominant bacteria in human feces, 16S rRNA-gene-targeted group-specific primers for the Bacteroides fragilis group, Bifidobacterium, the Clostridium coccoides group, and Prevotella were designed and evaluated. The specificity of these primers was confirmed by using DNA extracted from 90 species that are commonly found in the human intestinal microflora. The group-specific primers were then used for identification of 300 isolates from feces of six healthy volunteers. The isolates were clearly identified as 117 isolates of the B. fragilis group, 22 isolates of Bifidobacterium, 65 isolates of the C. coccoides group, and 17 isolates of Prevotella, indicating that 74% of the isolates were identified with the four pairs of primers. The remaining 79 isolates were identified by 16S ribosomal DNA sequence analysis and consisted of 40 isolates of Collinsella, 24 isolates of the Clostridium leptum subgroup, and 15 isolates of disparate clusters. In addition, qualitative detection of these bacterial groups was accomplished without cultivation by using DNA extracted from the fecal samples. The goal for this specific PCR technique is to develop a procedure for quantitative detection of these bacterial groups, and a real-time quantitative PCR for detection of Bifidobacterium is now being investigated (T. Requena, J. Burton, T. Matsuki, K. Munro, M. A. Simon, R. Tanaka, K. Watanabe, and G. W. Tannock, Appl. Environ. Microbiol. 68:2420-2427, 2002). Therefore, the approaches used to detect and identify predominant bacteria with the group-specific primers described here should contribute to future studies of the composition and dynamics of the intestinal microflora.     

Influence of Plants and Organic Matter on the Nitrogen Removal in Laboratory‐Scale Model Subsurface Flow Constructed Wetlands Inoculated with Anaerobic Ammonium Oxidizing Bacteria

Anaerobic oxidation of ammonium has become an alternative for the treatment of wastewater with high ammonium loads, and it was also suggested to be involved in the nitrogen removal process in constructed wetlands. Nonetheless, its role has not been well evaluated as yet. In this paper, results of a lab‐scale study are presented focusing on the evaluation of the role of Anammox bacteria, plants, applied ammonia, nitrite nitrogen loads, and the presence of organic matter in nitrogen transformation processes in subsurface‐flow constructed wetlands. The inoculation of the experimental model wetlands with active Anammox biomass increased the total nitrogen and ammonium removal rates to values up to 5.7 g N/m² d, which is almost 10 times higher than those values reported for subsurface flow constructed wetlands. Although the presence of plants caused a higher removal rate, the role of the plants became less important with high nitrite influent concentration. Because the unplanted experimental system without the addition of any organic carbon source showed also high nitrogen removal rates, it can be concluded that beside the potential for “conventional” denitrification in the planted systems the main mechanism for explaining the high nitrogen removal rates obtained during the experiments was the anaerobic ammonia oxidation. The assay of the formation of hydrazine from hydroxylamine and the findings of the molecular biology tests fitted with the positive results for potential Anammox activity obtained in the bottle test. The addition of organic carbon, specifically acetate, apparently had no great influence on Anammox activity, which is in agreement with the findings reported by other authors. Nevertheless, the addition influenced the redox potential. Some questions are still left open, which are mainly associated with the scaling up of these results and the inoculation of Anammox biomass in full‐scale systems.     

New concepts of microbial treatment processes for the nitrogen removal in wastewater

Many countries strive to reduce the emissions of nitrogen compounds (ammonia, nitrate, NOx) to the surface waters and the atmosphere. Since mainstream domestic wastewater treatment systems are usually already overloaded with ammonia, a dedicated nitrogen removal from concentrated secondary or industrial wastewaters is often more cost-effective than the disposal of such wastes to domestic wastewater treatment. The cost-effectiveness of separate treatment has increased dramatically in the past few years, since several processes for the biological removal of ammonia from concentrated waste streams have become available. Here, we review those processes that make use of new concepts in microbiology: partial nitrification, nitrifier denitrification and anaerobic ammonia oxidation (the anammox process). These processes target the removal of ammonia from gases, and ammonium-bicarbonate from concentrated wastewaters (i.e. sludge liquor and landfill leachate). The review addresses the microbiology, its consequences for their application, the current status regarding application, and the future developments.     

ABR结合SBR法处理印染废水的研究

采用实验室规模的厌氧折流板反应器(ABR)与序批式活性污泥曝气反应器(SBR)结合工艺处理印染废水。通过对ABR-SBR处理系统工艺条件的试验,在ABR段HRT为24~36 h,污泥负荷为0.43~2.46 kg COD/(m3.d),进水pH值为6.5~8.0,温度20℃~35℃;SBR段的溶解氧为2 mg/L,曝气时间为3~10 h,沉淀时间为2 h的条件下,经处理的印染工业废水COD、色度和苯胺去除率分别为32%~95%、89%~99%和50%~98%,其COD为30.0~97.1 mg/L,色度为8~40倍,苯胺浓度为0.20~0.95mg/L,达到了国家一级排放标准。     

Temporal variations of membrane foulants in the process of using flat-sheet membrane for simultaneous thickening and digestion of waste activated sludge

Membrane foulants were extracted at different operation time in simultaneous sludge thickening and digestion reactors using flat-sheet membranes. Temporal variations of foulants were analyzed by three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy, gel filtration chromatography (GFC), particle size distribution (PSD) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. Results showed that during the first 4 days fouling was mainly assigned to internal membrane foulants (IMFs), and afterwards external membrane foulants (EMFs) increased dramatically. EEM analysis showed that both IMFs and EMFs changed during the operation. Cluster analysis demonstrated that the characteristics of IMFs were relatively similar; however, both quantity and properties of EMFs were changed. GFC analysis showed that EMFs contained more molecules with large molecular weight compared to IMFs. PSD analysis illuminated that particle size of EMFs gradually increased and was larger than that of IMFs. ATR-FTIR analysis indicated that the foulants on membranes consisted of polysaccharides and proteins.     

Industrial wastewaters and dewatered sludge: rich nutrient source for production and formulation of biocontrol agent, <Emphasis Type="Italic">Trichoderma viride</Emphasis>

Axenic cultivation of biocontrol fungus Trichoderma viride was conducted on a synthetic medium and different wastewaters and wastewater sludges in shake flasks to search for a suitable raw material resulting in higher biocontrol activity. Soluble starch based synthetic medium, dewatered municipal sludge, cheese industry wastewater sludge, pre-treated and untreated pulp and paper industry wastewater and slaughter house wastewater (SHW) were tested for T. viride conidia and protease enzyme production. The maximum conidia production followed the order, soluble starch medium (>10⁹ c.f.u./mL), untreated pulp and paper industry wastewater (4.9 × 10⁷ c.f.u./mL) > cheese industry wastewater (1.88 × 10⁷ c.f.u./mL) ≈ SHW (1.63 × 10⁷ c.f.u./mL) > dewatered municipal sludge (3.5 × 10⁶ c.f.u./mL) > pre-treated pulp and paper industry wastewater (1.55 × 10⁶ c.f.u./mL). The protease activity of T. viride was particularly higher in slaughterhouse wastewater (2.14 IU/mL) and dewatered municipal sludge (1.94 IU/mL). The entomotoxicity of soluble starch based synthetic medium was lower (≈6090 SBU/μL) in contrast to other raw materials. The entomotoxicity inversely decreased with carbon to nitrogen ratio in the growth medium and the conidia concentration and protease activity also contributed to the entomotoxicity. The residual c.f.u./g formulation of T. viride conidia were up to approximately, 90% after 1 month at 4 ± 1 °C and about 70% after 6 months at 25 ± 1 °C. Thus, production of T. viride conidia would help in marketability of low cost biopesticide from the sludge and safe reduction of pollution load.     

Assessment of the Automobile Assembly Paint Process for Energy, Environmental, and Economic Improvement

A coat of paint adds considerable value to an automobile. In addition to consuming up to 60% of the energy needed by automobile assembly plants, however, the painting process also creates both economic and environmental impacts. This study investigated the degree of cost and environmental impact improvement that can be expected when modifications are considered for existing paint processes through heat integration. In order to accomplish this goal, a mathematical model was created to describe the energy use, costs, and environmental impacts from energy consumption in an automobile assembly painting facility. The model agrees with measured energy consumption data for process heating and electricity demand to within about 15% for one Michigan truck facility from which model input parameters were obtained. Thermal pinch analysis determined an energy conservation target of 58% of paint process energy demand. A heat exchanger network optimization study was conducted in order to determine how closely the network design could achieve this target. The resulting heat exchanger network design was profitable based on a discounted cash flow analysis and may achieve reductions in total corporate energy consumption of up to 16% if implemented corporatewide at a major automobile manufacturer.     

Comparison of the Adsorption Capabilities of Myriophyllum spicatum and Ceratophyllum demersum for Zinc,Copper and Lead

Industrial wastewaters contain various heavy metal components and therefore threaten aquatic bodies. Heavy metals can be adsorbed by living or non‐living biomass. Submerged aquatic plants can be used for the removal of heavy metals. This paper exhibits the comparison of the adsorption properties of two aquatic plants Myriophyllum spicatum and Ceratophyllum demersum for lead, zinc, and copper. The data obtained from batch studies conformed well to the Langmuir Model. Maximum adsorption capacities (q_max) were obtained for both plant species and each metal. The maximum adsorption capacities (q_max) achieved with M. spicatum were 10.37 mg/g for Cu²⁺, and 15.59 mg/g for Zn²⁺ as well as 46.49 mg/g for Pb²⁺ and with C. demersum they were 6.17 mg/g for Cu²⁺, 13.98 mg/g for Zn²⁺ and 44.8 mg/g for Pb²⁺. It was found that M. spicatum has a better adsorption capacity than C. demersum for each metal tested. Gibbs free energy and the specific surface area based on the q_max values were also determined for each metal.     

An Integrated System for the Bioremediation of Wastewater Containing Xenobiotics and Toxcic Metals

An integrated system for the biotreatment of acidic wastewaters containing both toxic metals and organics is presented. It consists of two bioprocess stages (i) an anaerobic, SRB stage (containing alkaline‐tolerant s ulfate‐ r educing b acteria) that at pH 8 (chosen to acclimatize the bacteria in the biomedium) produces high concentrations of total sulfide ions (more than 400 mg/L) which are added to the wastewater to precipitate the heavy metals out at pH 2 as metal sulfides, and (ii) an aerobic, acidophilic stage containing heterotrophic bacteria (WJB3) that degrade organic xenobiotics. The anaerobic system was comprised of a 4‐L fluidized bed bioreactor with immobilized SRB, a mixing tank, and a precipitation tank. The effluent from the bioreactor with a high concentration of sulfide ions was fed into a mixing tank where model wastewaters containing toxic metals and phenol at pH 2 were also fed at increasing loading rates until free metal ions could be detected in the precipitation tank outlet. Then the effluent from the precipitation tank outlet was fed into a 2.5‐L aerobic bioreactor in which phenol was degraded. In this research, 100 % removal efficiencies were obtained with wastewaters containing more than 400 mg/L metal ions and 900 mg/L phenol at a 6‐h HRT of the mixing tank.     

Isolation of Pseudomonas stutzeri in wastewater of catfish fish-ponds in the Mekong Delta and its application for wastewater treatment

The aim of this study was to explore the potential for reducing soluble N load in fishpond wastewater using naturally occurring denitrifying bacteria. Twenty-seven isolates were selected from in wastewater (liquid/solid) of catfish-ponds located along the Tien river, in the Mekong Delta, Vietnam in SW-LB medium (artificial seawater Luria-Britani medium) supplemented with 10 mM NH₄ and NO₃ and twenty-five isolates were identified as Pseudomonas stutzeri based on similarity of PCR-16S rRNA using universal primers and specific primers. Four isolates were effective in lowering soluble N (NH₄, NO₂ and NO₃) levels in fishpond water from 10 mg/L to negligible amounts after four days. Further experiments are underway to determine the fate of N lost from solution and the relative activity of ammonia oxidation, and nitrite and nitrate reduction by P. stutzeri isolates.