模糊控制强化生物除磷SBR系统的除磷过程

采用在线ORP和pH仪对两个平行的强化生物除磷(EBPR)SBR反应系统的厌氧放磷、缺氧吸磷和好氧吸磷过程进行监测。针对聚糖菌(GAO)和聚磷菌(PAO)的竞争和影响PAO和反硝化聚磷菌(DPAO)的各种因素,验证了以氧化还原电位(ORP)和pH作为除磷过程模糊控制参数的可行性和有效性。在此基础上,确立了厌氧／好氧(A／O)SBR系统和厌氧／缺氧(A2)SBR系统除磷过程的模糊控制策略。对ORP和pH的在线检测不仅可以模糊控制厌氧放磷、缺氧吸磷和好氧吸磷过程所需时间,节约能源优化处理效果,而且可以指示系统运行效果和功能微生物种群的竞争行为。     

The effects of selected parameters on the nitric oxide removal by biofilter

A bench-scale biofilter was used to demonstrate the treatability of off-gas containing nitric oxide (NO) by examining selected operational parameters. After 6 days of operation, the biofilter reached to a steady state and NO reduction was significant, reducing from 200 ppm to 95 and 40 ppm after 6 and 40 days of continuous operation. The oxygen concentrations in the inlet would affect NO removal performance significantly; as oxygen content decreasing from 6% to 0%, the NO removal efficiency increased from 55% to 99%, indicating that oxygen inhibited the progress of denitrification. NO removal was inversely proportional to inlet NO concentration, removal efficiency decreased from 88% to 40 % as NO concentration increasing from 60 to 500 ppm. Column height would significant effect on the NO removal efficiency, under column height=6.5m and O(2)=6% conditions, 90% of removal efficiency was achievable. The effect of glucose added into biofilter would significantly enhance the NO removal efficiencies for both anaerobic and aerobic conditions of which 99% and 55%, respectively.     

Using UV pretreatment to enhance biofiltration of mixtures of aromatic VOCs

Mixtures of airborne toluene and o-xylene, two relatively recalcitrant volatile organic compounds (VOCs), were treated effectively using integrated UV-biofiltration. The set-up consisted of a biofilter receiving UV-pretreated stream and a reference biofilter receiving no pretreatment. Experimental conditions included UV fluences of 6 and 12 mJcm(-2) as well as air flow rates of 6.3 and 9.4 Lmin(-1), corresponding to biofilter empty bed retention times (EBRTs) of 45 and 30s, respectively. The inlet concentration of organics (toluene and o-xylene) ranged between 70 and 650 mg(carbon)m(-3). The UV-biofilter consistently provided removal efficiencies of greater than 95% over the range of toluene and o-xylene inlet concentrations. Also, the coupled UV-biofiltration system provided up to 60% additional contaminant removal compared to the sum of that offered by UV and reference biofilter, demonstrating the synergistic effect of UV on biofilter performance. The UV photooxidation partially oxidized a fraction of toluene and o-xylene into water soluble and more biodegradable intermediates, such as acetaldehyde and formaldehyde, which were readily removed in the downstream biofilter. These intermediates along with up to 20ppmv ozone, formed through the photolysis of oxygen by 185 nm UV, contributed to the enhanced degradation of parent VOCs in the biofilter as well as the absence of any inhibitory effects of the VOCs on one another. Also, the presence of ozone helped control the growth of excess biofilm in the UV-coupled biofilter. While the standalone biofilter showed significant pressure drop increase (of up to 14 mm H(2)Om(-1) of the bed) over the course of experiment, the UV-coupled biofilter maintained a relatively low pressure drop of less than 3 mmH(2)Om(-1) of the bed.     

Performance of low pH biofilters treating a paint solvent mixture: continuous and intermittent loading

Two biofilters packed with a reticulated polyurethane foam medium were inoculated with a compost-derived enrichment culture grown under acidic conditions (pH 3.0) and then operated over a period lasting 63 days. Both biofilters were supplied with a humidified gas stream containing a five-component mixture of acetone, methyl ethyl ketone, toluene, ethylbenzene, and p-xylene at a total VOC loading rate 80.3 gm(-3)h(-1) to simulate treatment of air emissions resulting from manufacture of reformulated paint. One biofilter was operated under continuous loading conditions and the other received intermittent loading with contaminants supplied only 8 h/day. Nutrient solution with pH 3.0 was supplied approximately once per week to provide nitrogen and other nutrients. Data are presented which demonstrate that undefined mixed cultures acclimated at low pH can successfully treat paint solvent mixtures in biofilters. The biofilter receiving continuous loading reached high overall removal efficiency (greater than 90% overall removal) 3 weeks after startup, and performance increased over time reaching overall removal in the range of 97-99% after 50 days. Performance of the intermittently loaded biofilter developed more slowly, requiring 6 weeks to stabilize at an overall removal efficiency in excess of 90%. In both biofilters, ketone components were more rapidly degraded than aromatic components, and removal of aromatic compounds was somewhat unstable even after 2 months of biofilter operation. Scanning electron microscopy (SEM) revealed that fungi dominated the microbial populations in both biofilters.     

Low-biodegradable composite chemical wastewater treatment by biofilm configured sequencing batch reactor (SBBR)

Biofilm configured system with sequencing/periodic discontinuous batch mode operation was evaluated for the treatment of low-biodegradable composite chemical wastewater (low BOD/COD ratio approximately 0.3, high sulfate content: 1.75 g/l) in aerobic metabolic function. Reactor was operated under anoxic-aerobic-anoxic microenvironment conditions with a total cycle period of 24 h [fill: 15 min; reaction: 23 h (aeration along with recirculation); settle: 30 min; decant: 15 min] and the performance of the system was studied at organic loading rates (OLR) of 0.92, 1.50, 3.07 and 4.76 kg COD/cum-day. Substrate utilization showed a steady increase with increase in OLR and system performance sustained at higher loading rates. Maximum non-cumulative substrate utilization was observed after 4h of the cycle operation. Sulfate removal efficiency of 20% was observed due to the induced anoxic conditions prevailing during the sequence phase operation of the reactor and the existing internal anoxic zones in the biofilm matrix. Biofilm configured sequencing batch reactor (SBR) showed comparatively higher efficiency to the corresponding suspended growth and granular activated carbon (GAC) configured systems studied with same wastewater. Periodic discontinuous batch mode operation of the biofilm reactors results in a more even distribution of the biomass throughout the reactor and was able to treat large shock loads than the continuous flow process. Biofilm configured system coupled with periodic discontinuous batch mode operation imposes regular variations in the substrate concentration on biofilm organisms. As a result, organisms throughout the film achieve maximum growth rates resulting in improved reaction potential leading to stable and robust system which is well suited for treating highly variable wastes.     

Evaluating the impact of water supply strategies on p-xylene biodegradation performance in an organic media-based biofilter

The influence of water irrigation on both the long-term and short-term performance of p-xylene biodegradation under several organic loading scenarios was investigated using an organic packing material composed of pelletised sawdust and pig manure. Process operation in a modular biofilter, using no external water supply other than the moisture from the saturated inlet air stream, showed poor p-xylene abatement efficiencies (≈33 ± 7%), while sustained irrigation every 25 days rendered a high removal efficiency (RE) for a critical loading rate of 120 g m(-3)h(-1). Periodic profiles of removal efficiency, temperature and moisture content were recorded throughout the biofilter column subsequent to each biofilter irrigation. Hence, higher p-xylene biodegradation rates were always initially recorded in the upper module, which resulted in a subsequent increase in temperature and a decrease in moisture content. This decrease in the moisture content in the upper module resulted in a higher removal rate in the middle module, while the moisture level in the lower module steadily increased as a result of water condensation. Based on these results, mass balance calculations performed using measured bed temperatures and relatively humidity values were successfully used to account for water balances in the biofilter over time. Finally, the absence of bed compaction after 550 days of continuous operation confirmed the suitability of this organic material for biofiltration processes.     

Kinetics of the removal of mono-chlorobenzene vapour from waste gases using a trickle bed air biofilter

The performance of a trickle bed air biofilter (TBAB) in the removal of mono-chlorobenzene (MCB) was evaluated in concentrations varying from 0.133 to 7.187 g m(-3) and at empty bed residence time (EBRT) varying from 37.7 to 188.52 s. More than 90% removal efficiency in the trickle bed air biofilter was achieved for the inlet MCB concentration up to 1.069 g m(-3) and EBRT less than 94.26 s. The trickle bed air biofilter was constructed with coal packing material, inoculated with a mixed consortium of activated sludge obtained from sewage treatment plant. The continuous performance of the removal of MCB in the trickle bed air biofilter was monitored for various gas concentrations, gas flow rates, and empty bed residence time. The experiment was conducted for a period of 75 days. The trickle bed air biofilter degrading MCB with an average elimination capacity of 80 g m(-3) h(-1) was obtained. The effect of starvation was also studied. After starvation period of 8 days, the degradation was low but recovered within a short period of time. Using macrokinetic determination method, the Michaelis-Menten kinetic constant K(m) and maximum reaction rate, r(max) evaluated as 0.121 g m(-3) s(-1) and 7.45 g m(-3), respectively.     

Effects of adsorptive properties of biofilter packing materials on toluene removal

Various adsorptive materials, including granular activated carbon (GAC) and ground tire rubber (GTR), were mixed with compost in biofilters used for treating gaseous toluene, and the effects of the mixtures on the stability of biofilter performance were investigated. A transient loading test demonstrated that a sudden increase in inlet toluene loading was effectively attenuated in the compost/GAC biofilter, which was the most significant advantage of adding adsorptive materials to the biofilter packing media. Under steady conditions with inlet toluene loading rates of 18.8 and 37.5 g/m³/h, both the compost and the compost/GAC biofilters achieved overall toluene removal efficiencies greater than 99%. In the compost/GAC mixture, however, biodegradation activity declined as the GAC mass fraction increased. Because of the low water-holding capacity of GTR, the compost/ground tire mixture did not show a significant improvement in toluene removal efficiency throughout the entire operational period. Furthermore, nitrogen limitations affected system performance in all the biofilters, but an external nitrogen supply resulted in the recovery of the toluene removal efficiency only in the compost biofilter during the test periods. Consequently, the introduction of excessive adsorptive materials was unfavorable for long-term performance, suggesting that the mass ratio of the adsorptive materials in such mixtures should be carefully selected to achieve high and steady biofilter performance.     

Influence of hydraulic loading and air flowrate on urban wastewater nitrogen removal with a submerged fixed-film reactor

Nutrient disposal to sensitive areas, particularly nitrogen and phosphorus from wastewater treatment plants, provokes eutrophication reducing water quality. Fixed film technology is widely used for the removal of organic matter and nitrogen by the biological process of nitrification-denitrification. This paper studies a nitrification and post-denitrification lab-scale plant with a downflow aerobic submerged filter for removal of organic matter and nitrification, followed by an anoxic upflow biofilter for denitrification. Recycled construction material (clay shists) was employed as support material and methanol was used as carbon source. After 2 weeks of acclimation in which nitrification reached steady-state conditions, different hydraulic loadings (0.35-1.59 m(3)/m(2)h) and air flowrates (7.78-43.5 m(3)/m(2)h) were applied for 1 year. The highest hydraulic loading which complied with the EU regulation on nitrogen disposal was 0.71 m(3)/m(2)h (1.6 h). Hydraulic retention time (HRT), which corresponded to a nitrogen removal of 0.64 kg N/m(3) per day operating at an air flowrate of 25.6 m(3)/m(2)h. Concerning to organic matter removal efficiency, the aerobic reactor accepted a maximum chemical oxygen demand (COD) volumetric loading of 16.0 kg COD/m(3) per day with a 75% COD removal efficiency. For all the tests carried out, suspended solids (SS) concentration in the outlet water was less than 35 mg/l.     

Confirming Pseudomonas putida as a reliable bioassay for demonstrating biocompatibility enhancement by solar photo-oxidative processes of a biorecalcitrant effluent

The performance of a sequencing batch reactor (SBR) seeded with aerobic granular sludge was studied. The lab-scale SBR treating domestic wastewater operated at a volumetric loading rate (VLR) of 0.75-3.41 kg COD/(m(3)d). The granule stability was related to the organic loading, and high loading would be favorable for granule stability. Analysis of typical cycle showed that granular sludge had good ability to simultaneously remove nitrogen and phosphorus. Most organic substances were removed at the anaerobic stage. At the aerobic stage, simultaneous nitrification and denitrification (SND) happened with phosphorus absorption. The SBR had good removal performance for organic matter and phosphate. However, the total nitrogen (TN) removal performance was ordinary, with average removal efficiency of about 52%. Batch experiments indicated that increases of influent C/N ratio and a large percentage of granule in the sludge were conducive for SND in SBR.     

Aerobic decolourization of the indigo dye-containing textile wastewater using continuous combined bioreactors

An aerobic bioprocess was applied to Indigo dye-containing textile wastewater treatment aiming at the colour elimination and biodegradation. A combined aerobic system using continuous stirred tank reactor (CSTR) and fixed film bioreactor (FFB) was continuously operated at constant temperature and fed with the textile wastewater (pH: 7.5 and total chemical oxygen demand (COD): 1185 mg l(-1)). The CSTR is a 1l continuous flow stirred tank reactor with a 700 ml working volume, and operated with a variable wastewater loading rate (WLR) from 0.92 to 3.7 g l(-1) d(-1). The FFB is a 1.5l continuous flow with three compartments packed with a rippled cylindrical polyethylene support, operated with a variable WLR between 0.09 and 0.73 g l(-1) d(-1). The combined two bioreactors were inoculated by an acclimated microbial consortium and continuously operated with four total WLR. This system presented high COD elimination and colour removal efficiencies of 97.5% and 97.3%, respectively, obtained with a total hydraulic retention time (HRT) of 4 days and total WLR of 0.29 g l(-1) d(-1). The effects of WLR on absorption phenomena on the yield of conversion of substrate on biomass (R(TSS/COD)) and on the yield of conversion of substrate on active biomass (R(VVS/COD)) are discussed. The increase of WLR and the decrease of HRT diminished the performances of this system in terms of decolourization and COD removal explained by the sloughing of biofilm, and the washout phenomena.     

Simultaneous nitrification-denitrification and phosphorus removal in a fixed bed sequencing batch reactor (FBSBR)

Biological nutrient removal (BNR) was investigated in a fixed bed sequencing batch reactor (FBSBR) in which instead of activated sludge polypropylene carriers were used. The FBSBR performance on carbon and nitrogen removal at different loading rates was significant. COD, TN, and phosphorus removal efficiencies were at range of 90-96%, 60-88%, and 76-90% respectively while these values at SBR reactor were 85-95%, 38-60%, and 20-79% respectively. These results show that the simultaneous nitrification-denitrification (SND) is significantly higher than conventional SBR reactor. The higher total phosphorus (TP) removal in FBSBR correlates with oxygen gradient in biofilm layer. The influence of fixed media on biomass production yield was assessed by monitoring the MLSS concentrations versus COD removal for both reactors and results revealed that the sludge production yield (Y(obs)) is significantly less in FBSBR reactors compared with SBR reactor. The FBSBR was more efficient in SND and phosphorus removal. Moreover, it produced less excess sludge but higher in nutrient content and stabilization ratio (less VSS/TSS ratio).     

碳源类型对AOA-SBR系统的除磷特性和菌群组成的影响

分别以乙酸钠、丙酸钠为碳源,采用厌氧-好氧-缺氧(AOA)模式运行SBR反应器,考察该系统内的除磷特性和聚磷微生物菌群结构。驯化25天后,两系统均表现出较为稳定的除磷效果,两系统稳定期磷的去除率分别在88%和97%左右。乙酸钠系统的污泥沉降性较好,污泥增长缓慢;丙酸钠系统的污泥除磷性能较好,生长速率快,但沉降性较差。荧光原位杂交(FISH)分析表明,两系统均富集出了大量的聚磷菌Accumulibacter,但类型上存在差异。乙酸钠系统内的Accumulibacter主要为II型,而I型Accumulibacter在丙酸钠系统内占主导地位。     

The kinetic behaviors of simultaneous phosphorus release and denitrification on sludge for BNR processes

Abstract

In this study, we investigated the kinetic behaviors of phosphorus release and denitrification on sludge for two biological nutrient removal (BNR) processes, i.e., suspension growth process (A₂O) and combined suspension‐biofilm growth process (TNCU) under anoxic condition. The readily biodegradable substrate and nitrate loadings, 20–180 mg HAc‐COD/g MLSS and 4–25 mg NO₃‐N/g MLSS respectively, are controlled in a batch reactor for phosphorus release and denitrification of sludge taken from A₂O and TNCU processes under various SRT (5, 10 and 15 days) operating conditions. Experimental results indicated that the occurrence of simultaneous phosphorus release and denitrification is a kinetic competition mode under anoxic condition in the presence of a readily biodegradable substrate. Moreover, the available substrate in bulk solution determined the kinetic behaviors of phosphorus release and denitrification. To prevent nitrate inhibition, the sludge is exposed to a C/N ratio higher than 6.1 for phosphorus release. The sludge's phosphorus content (as created by different SRT processes) and initial nitrate loading dominated the kinetics of phosphorus release and denitrification, respectivley. Moreover, the sludge of suspension gorwth process demonstrated a higher phosphorus release potential than the combined suspension‐biofilm growth process. However, the nitrate inhibition is significant for A₂O sludge also. Based on proposed phosphorus release rate equation, the rate constant would be reduced by denitrification about 31–67% and 20–45% for A₂O and TNCU processes, respectively.     

Biological nitrogen and phenol removal from saline industrial wastewater by submerged fixed-film reactor

In this study a biological nitrogen removal process using a submerged fixed-film reactor was applied to treat industrial wastewater with phenol (1g/l), a high nitrogen concentration (0.4 g N/l) and high salinity (30 g/l). The process consisted of a pre-denitrification system with a down-flow-up-flow biofilter (two columns, each with an effective volume of 21 l) packed with clayey schists from recycled construction material. The efficiency of the system for reducing COD, phenol concentration and total nitrogen was tested under different running conditions such as influent flow (10, 12 and 15 l/d), air loading (6.8 and 13.6m(3)/m(2)h) and effluent recirculation (300%, 400%, and 600%). The system demonstrated a high capacity for reducing COD concentration (95.75+/-0.72%), independently of running conditions. The aerobic column eliminated most of the phenol in the influent. Nitrogen removal took place mainly in the anoxic column, and was conditioned by the air loading in the aerated column, owing to the dependence of nitrification on the supply of oxygen. However, this process was not able to achieve a nitrogen oxidation superior to 63%, in spite of a sufficient supply of oxygen and the diluting effect of high recirculation (600%) on the phenol concentration in the influent. In spite of the limitations observed in the process of nitrification, results for the removal of total nitrogen were as high as 83%, owing to a combination of different processes for nitrogen removal.     

A comparative assessment of biofiltration and activated sludge diffusion for odour abatement

The deodorization performance of a biofilter and an activated sludge diffusion (AS) system was comparatively evaluated in terms of removal efficiency (RE) and process stability at empty bed residence times (EBRT) ranging from 94 to 32s. Both bioreactors were fed with a synthetic odorous emission containing H(2)S, butanone and toluene at 23.6-43.3, 4.3-6.3 and 0.4-0.6 mg m(-3), respectively. While the outlet H(2)S concentration was always lower than 1.4 mg m(-3), the REs for butanone and toluene remained higher than 95% in both bioreactors regardless of the EBRT. The continuous supply of wastewater in the AS unit did not affect removal and appeared to be a requirement for efficient pollutant abatement. Despite the narrow carbon source spectrum treated, the AS system maintained a large bacterial diversity over time. Therefore, the results obtained confirmed the potential of AS systems as a robust and efficient biotechnology for odour treatment in WWTPs.     

Removal of styrene vapor from waste gases by a trickle-bed air biofilter

The trickle-bed air biofilter (TBAB) performance for the removal of high-strength styrene was evaluated under different gas flow rates and influent concentrations. Under pseudo-steady-state conditions, the elimination capacity increased but the removal efficiency decreased with the increase of styrene loading. More than 90 and 80% removal efficiencies were achieved for influent styrene loadings below 32 and 55g/m(3)/h, respectively. The TBAB appears to be an effective treatment process for controlling high-strength styrene emission under low-to-medium loading conditions, and the effectiveness could be maintained over 140 days of laboratory operation.     

Application of a hybrid system comprising carbon-doped TiO2 film and a ceramic media-packed biofilter for enhanced removal of gaseous styrene

It is difficult to efficiently remove gaseous styrene using a TiO(2) film-coated photoreactor under UV light. Therefore, we used a hybrid system consisting of a carbon-doped TiO(2) (C-TiO(2)) film and a media-packed biofilter in order to enhance the removal efficiency (RE) of gaseous styrene compared to that of a pure (undoped) TiO(2) photoreactor. The C-TiO(2) was synthesized by a sol-gel combustion method, and its absorption spectrum was stronger that of pure (undoped) TiO(2) in the UV-vis range. The resultant RE of the C-TiO(2) film was 113-200% higher than that of the pure TiO(2) film. The initial RE of the photoreactor for input styrene concentrations of 630 mg m(-3), 420 mg m(-3), and 105 mg m(-3) was 20.6%, 29.8%, and 40.0%, respectively. When the biofilter was added, the RE increased to 93.3%, 97.9%, and 99.0%, respectively. Thus, application of the hybrid system consisting of both a photoreactor coated with a C-TiO(2) film and a biofilter is advantageous in terms of the removal efficiency of gaseous styrene.     

Steady- and transient-state effects during the biological oxidation of gas-phase benzene in a continuously operated biofilter

Biofiltration is an aerobic degradation process in which a well-humidified contaminated air stream is passed through a porous packed medium that supports a thriving population of microbes. The removal of benzene vapor was investigated in a laboratory-scale biofilter packed with compost, inoculated with a mixed microbial consortium. This biofilter was operated continuously in six different phases for a period of 8 months at different flow rates, 0.024–0.144 m³ h⁻¹ with benzene concentrations ranging up to 1.7 g m⁻³. Under steady-state conditions, the removal efficiencies (REs) in the biofilter was consistently greater than 78% when benzene loading was less than 20 g m⁻³ h⁻¹. The maximum elimination capacity (EC) achieved in this study is 64 g m⁻³ h⁻¹ at an inlet loading rate of 128 g m⁻³ h⁻¹. The response of the biofilter to shutdown, restart operations and fluctuations in inlet concentration, and flow rate was determined by subjecting the biofilter to inlet loads of up to 120 g m⁻³ h⁻¹. The biofilter responded effectively to these loading conditions and was found to recover rapidly. The results from this study suggest that a compost biofilter is effective in treating benzene vapor under steady- and transient-conditions.     

Evaluation of gas removal and bacterial community diversity in a biofilter developed to treat composting exhaust gases

The performance of a new, but simply constructed, biofilter system, developed to purify composting exhaust air, was evaluated. The biofilter was packed with mature compost mixed with activated carbon and sludge sourced from a wastewater treatment plant. An alternating air flow system and a bioaerosol reduction device were designed to prevent pressure drop and reduce bioaerosol release. Experimental results demonstrated that satisfactory removal efficiencies of nitrogen-containing compounds, sulfur-containing compounds, fatty acids, total hydrocarbon and odor were achieved at an empty bed retention time (EBRT) of 30s. No significant acidification or alkalinity in the biofilter was observed, and the system was characterized by a small pressure drop and a low level of bioaerosol emission. Denaturing gradient gel electrophoresis (DGGE) and fluorescence in situ hybridization (FISH) techniques were used to uncover the changes in the bacterial community of the biofilter during the deodorization processes. A minimum of 16 bands were observed in the DGGE profile. Phylogenetic analysis revealed the phylum of Proteobacteria to be predominant, followed by Actinobacteria, Bacteroidetes, and Firmicutes, in descending order. However, the occurrence and predominance of specific bacterial species varied with the environmental conditions of the biofilter. Our results demonstrate - from both an engineering and biological point of view - the feasibility of the biofilter system described herein in purifying the gases derived from composting food waste.