反硝化脱氮碳源研究现状

针对目前我国污水处理厂存在的脱氮碳源不足的问题,提出了以纤维素为主的固体碳源、污泥水解产生的挥发性脂肪酸以及有机工业废水等新型碳源,并探讨了这几种新型碳源的研究现状,为提高脱氮效率提供了依据。     

Wheat straw as substrate for water denitrification

Biological denitrification of drinking water was studied in up-flow laboratory reactors packed with wheat straw which served as the sole carbon source as well as the only physical support for the microorganisms. The highest rates of denitrification (0.053 g N removed l⁻¹ d⁻¹) were observed in fresh reactors during their first week of operation and the efficiency of the process declined thereafter. The addition of fresh wheat straw brought about a temporary improvement of the denitrification performance and a regime of one weekly addition prevented the deterioration of a reactor which was operated for 5 months. The rate of denitrification was affected by the water velocity and decreased at velocities above 0.054 m d⁻¹. Colour and soluble organic carbon associated with fresh straw were removed by adsorption on powdered activated carbon.     

阴离子交换膜生物反应器反硝化性能的研究

考察了进水硝酸盐浓度对阴离子交换膜生物反应器反硝化性能的影响。试验结果表明,当进水NO3-为47.01～168.55mg/L时,流动池出水中的NO3-N浓度满足我国生活饮用水水质标准中小于10mg/L的要求(NO3-≤44.29mg/L)。厌氧生物反应器对硝酸盐具有较高的反硝化性能。流动池出水中的Cl-浓度随着进水NO3-浓度的增加而升高,但出水pH值稳定在6.8左右。出水总有机碳浓度与进水的保持一致,表明其未受到"二次污染"和"微生物污染"。     

Concurrent denitrification and oxygen uptake in microbial films

Mixed microbial films were grown on the inner walls of a tubular reactor with recirculation of the reactor contents and continuous flow-through of nutrient solution. The loss of total oxidized nitrogen was correlated to the film population, the nitrite concentration and the dissolved oxygen concentration in the reactor. When film population was greater than 0.5 × 10⁹ cells cm⁻², reactor dissolved oxygen concentration greater than 1 mg l⁻¹ had little effect on the nitrate loss. Nitrate loss declined for film populations greater than 2 × 10⁹ cells cm⁻². Models based on Monod and zero-order microbial kinetics were calibrated using these data and a nonlinear least squares method. There was little difference in the residual errors with these methods.     

Mixing in upflow anaerobic filters and its influence on performance and scale-up

Tracer studies were carried out in laboratory-scale and pilot-scale upflow anaerobic filters to determine the effect of liquid velocity, gas production and media depth on mixing patterns. A computer simulation model was developed to analyse tracer-response curves. In water studies at laboratory scale, gas production was shown to have a significantly greater effect on mixing than liquid upflow velocity. A reduction in the quantity of media also resulted in greater mixing due to the greater void space in which synthetic gas bubbles could cause turbulence. In the presence of sludge during reactor operation, at pilot and laboratory-scale, gas production had a significant influence on mixing. However, liquid velocity played an important role in solids distribution in the filter, in conjunction with media depth. At pilot-scale, at a low solids concentration, a high liquid velocity lifted the sludge “bed”, raising the source of gas production. The absence of gas below the sludge bed resulted in a plug flow regime which the incoming substrate entered. A reduction in the quantity of media increased the degree of mixing for a given liquid velocity and gas surface load. Lower liquid upflow velocities are required at a reduced media depth to prevent excessive biomass loss. Shear rates increase at high liquid and gas velocities, resulting in detachment of solids from the media and biomass washout. A close correlation was established between mixing and process performance which led to the development of a programme for start-up and operation of the filter to maintain optimum biomass/substrate contact. A strategy for scale-up was proposed through the development of correlations obtained from laboratory-scale filter studies which were used to predict pilot-scale mixing characteristics. This research highlighted the important factors influencing mixing patterns and scale-up in anaerobic upflow filters.     

Chemolithotrophic denitrification with elemental sulfur for groundwater treatment

Denitrification for the treatment of nitrates in wastewater typically relies on organic electron donating substrates. However, for groundwater treatment, inorganic compounds such as elemental sulfur (S0) are being considered as alternative electron donors in order to overcome concerns that residual organics can cause biofouling. In this study, a packed-bed bioreactor supplied with S0:limestone granules (1:1, v/v) was started up utilizing a chemolithotrophic denitrifying enrichment culture in the form of biofilm granules that was pre-cultivated on thiosulfate. The granular enrichment culture enabled a rapid start-up of the bioreactor. A nearly complete removal of nitrate (7.3 mM) was NO3- attained by the bioreactor at nitrate loading rates of up to 21.6 mmol/(L(reactor)d). With lower influent concentrations (1.3 mM nitrate) comparable to those found in contaminated groundwater, high nitrate loads of 18.1 mmol/(L(reactor)d) were achieved with an average nitrate removal efficiency of 95.9%. The recovery of nitrogen as benign N2 gas was nearly stoichiometric. The concentration of undesirable products from S0-based denitrification such as nitrite and sulfide were low. Comparison of bioreactor results with batch kinetic studies revealed that denitrification rates were dependent on the surface area of the added S0. The surface area normalized denitrification rate was determined to be 26.4 mmol /(m2 S0 d).     

Sludge accumulation pattern in an anaerobic pond under Mediterranean climatic conditions

The main objective of this study was to observe the sludge accumulation pattern of an experimental, covered, anaerobic pond treating municipal wastewater under Mediterranean climatic conditions throughout a 2-year operational period (1999-2000) in order to form a seasonal sludge accumulation model which may be used to predict the required desludging time, not only of the particular anaerobic pond used in the study, but also for other types of anaerobic ponds and operational situations. The 4-m deep pond was supplied with pre-screened, untreated wastewater from the nearby treatment plant of Thessaloniki, Greece, initially at a flow rate of 120m3/day and later at a flow rate of 150m3/day. The influent characteristics were BOD5 441 mg O2/L, COD 942 mg O2/L and suspended solids (SS) 574 mg/L. BOD5, COD, and SS concentrations of the pond effluent were reduced by 50%, 53%, and 64%, respectively, in comparison with those of the influent. During the operational period, three distinctly different zones were seen to form within the anaerobic pond: The first zone, which formed at the bottom of the pond, consisted of inert, high-density sludge. The second zone, which formed above this, contained a high concentration of volatile (easily biodegradable) sludge. The third upper zone (supernatant), was a liquid layer low in suspended solids. The accumulation of sludge in the pond followed an annual sinusoidal pattern with high values during winter and low ones during summer due to the increased digestion rate. The maximum high-density sludge height observed was 0.7m, or 2% (14 m3) of the total pond volume. The maximum volatile sludge accumulation reached 3.1 m, or 53% (300 m3) of the pond volume. A seasonal sludge accumulation model, based on the sludge inflow and seasonal digestion rates, was used to simulate the annual fluctuation in accumulation rate for the local (Mediterranean type) climatic conditions. Monthly values of accumulation (or digestion) rate of sludge (K(AS)) were experimentally estimated at specific mean monthly air temperatures and approximated by a regression second degree polynomial equation to be used with the model. The predicted desludging interval for our experimental pond was 3 years.     

纺织污水处理厂厌氧水解及接触氧化工艺调试

介绍了空港经济区纺织污水处理厂＂厌氧水解＋接触氧化＋化学混凝法＋沉淀分离＂组合工艺的运行调试过程,针对纺织废水水质间歇性超标、水质波动大以及纺织废水与市政污水的比例波动等问题,通过合理调整气水比、溶解氧、生物膜厚度、加药量等工艺参数,使系统的出水水质达到了设计要求,可为同行业污水处理厂的试运行调试提供参考。     

Application of response surface methodology to optimize nitrate removal at low temperature by aerobic denitrificator Pseudomonas strain An‐1

Response surface methodology (RSM) was applied to optimize the conditions of nitrate removal by Pseudomonas strain AN‐1 at low temperature, which was isolated from aniline‐contaminated groundwater. A three‐factor, three‐level Box–Behnken experimental design and analysis of variance were combined with the obtained second‐order polynomial equation and applied for RSM optimization. By solving the second‐order polynomial equation and analysing the 3D response surface, a ‐N concentration of 65.29 mg/L, an initial pH of 6.65, and an initial DO of 7.53 were identified as the optimized conditions. These conditions achieved a removal percentage of 53.7485% after 48 h at 10°C, which was in good agreement with the predicted 53.8085%. This study showed the excellent ability of the Pseudomonas strain AN‐1 to degrade nitrate at low temperatures, which provided a solid foundation for the further application of this microorganism in the treatment of nitrate‐contaminated groundwater.     

Sulfide-induced nitrate reduction in the sludge of an anaerobic digester of a zero-discharge recirculating mariculture system

The anaerobic digester is a vital component in a zero-discharge mariculture system as therein most of the organic matter is mineralized and nitrogen-containing compounds are converted to gaseous N₂. Although denitrification is a major respiratory process in this nitrate-rich treatment stage, also sulfate respiration takes place and may cause undesirable high sulfide concentrations in the effluent water. To examine the effect of sulfide on nitrate reduction, in situ depth profiles of inorganic nitrogen and sulfur compounds were determined. Additionally, nitrate reduction was examined as a function of ambient sulfide concentrations in sludge collected from different locations in the anaerobic reactor. Depth profiles showed high concentrations of nitrate and low concentrations of sulfide and ammonia in the aqueous layer of the reactor. A sharp decrease of nitrate and an increase in sulfide and ammonia concentrations was measured at the water-sludge interface. Nitrate reduction was highest in this interface zone with rates of up to 8.05 ± 0.57 μmol NO₃⁻ h⁻¹ g_(sludge)⁻¹. Addition of sulfide increased the nitrate reduction rate at all sludge depths, pointing to the important role of autotrophic denitrification in the anaerobic reactor. Dissimilatory nitrate reduction to ammonia (DNRA) was found to be low in all sludge layers but was enhanced when sludge was incubated at high sulfide concentrations. Although nitrate reduction rates increased as a result of sulfide addition to sludge samples, no differences in nitrate reduction rates were observed between the samples incubated with different initial sulfide concentrations. This as opposed to sulfide oxidation rates, which followed Michaelis-Menten enzymatic kinetics. Partial oxidation of sulfide to elemental sulfur instead of a complete oxidation to sulfate, could explain the observed patterns of nitrate reduction and sulfide oxidation in sludge incubated with different initial sulfide concentrations.     

粗骨料表面分维的研究

混凝土浆体用量越少,其体积稳定性越好。混凝土浆体用量与粗骨料的表面分维有关.采用所提出的试验方法,可得到粗骨料的比表面积、粗骨科表面积形状因子与体积形状因子的比值,代入理论公式可求出粗骨料表面分维.采用所提出的试验和理论相结合的方法,可以较准确得到粗骨料表面分维.研究成果可用于混凝土配合比的设计和优化.     

用厌氧产氢反应器出水培养好氧颗粒污泥的研究

以厌氧产氢反应器出水为底物，在序批式反应器中研究了好氧颗粒污泥的培养过程。结果表明，以厌氧产氢反应器出水为底物，在60d内能够培养出粒径大、沉降性能优异且对污染物去除能力强的好氧颗粒污泥。在活性污泥的颗粒化过程中，伴随着污泥体积指数的减小。污泥的粒径和沉速增大，反应器内的污泥浓度增加，从而提高了反应器的处理效能。     

由水泥颗粒比表面积引发的思考

结合教学实践,详细推导了水泥颗粒粒径的大小与水泥比表面积之间的换算关系,得出了粉粒状物料比表面积的计算公式Sn=4^3√nπR1^2,并给出了水泥颗粒比表面积的大小对水泥物理力学性质的影响情况,以期为学习水泥专业的人士提供指导。     

Sensory pollution from bag-type fiberglass ventilation filters: Conventional filter compared with filters containing various amounts of activated carbon

As ventilation filters accumulate particles removed from the airstream, they become emitters of sensory pollutants that degrade indoor air quality. Previously we demonstrated that an F7 bag-type filter that incorporates activated carbon (a “combination filter”) reduces this adverse effect compared to an equivalent filter without carbon. The aim of the present study was to examine how the amount of activated carbon (AC) used in combination filters affects their ability to remove both sensory offending pollutants and ozone. A panel evaluated the air downstream of four different filters after each had continuously filtered outdoor suburban air over a period of 6 months. Interim assessments (mid-term evaluation) were performed after 3 months. During both assessments, four unused filters, identical in type to the loaded filters, were also evaluated. The evaluated filters included a conventional F7 fiberglass filter and three modifications of a bag-type fiberglass combination filter: the “Heavy” corresponded to a commercially available filter containing 400 g of carbon per square meter of filter area, the “Medium” contained half as much carbon (200 g/m²), and the “Light” contained a quarter as much carbon (100 g/m²). Each filter was weighed at the beginning of the soiling period and after 3 and 6 months of service. Additionally, up- and down-stream ozone concentrations and filter pressure drops were measured monthly. Following 6 months of service, the air downstream of each of the combination filters was judged to be significantly better than the air downstream of the 6-month-old F7 filter, and was comparable to that from an unused F7 filter. Additionally, the combination filters removed more ozone from the air than the F7 filter, with their respective fractional removal efficiencies roughly scaling with their carbon content.     

Removal of nitrogen from industrial wastewaters with the use of algal rotating disks and denitrification packed bed reactor

An attempt was made to use an algal rotating disk system in a two-step biological purification of nitrogen fertilizer industry wastewaters. The proposed method involved the removal of ammonium by Stichococcus bacillaris growing on the rotating disk and of oxidized forms of nitrogen by denitrifying bacteria. The use of a rotating algal disk followed by denitrification bed as the second step of biological treatment removed about 90% of nitrogen from the wastewater. A change of purification sequence resulted in the appearance of NO ⁻₃ and NO⁻₂ in the purified wastewater caused by the activity of nitrifying bacteria accompanying algae in the biological film on the disk. It was found that methanol used as a carbon source for denitrifying bacteria could be replaced by organic matter of algal origin.     

Denitrification studies with glycerol as a carbon source

Based on the results of experimental work, the use of glycerol as a carbon source for denitrification is discussed. Investigations were carried out in modified UASB reactor using a mixed bacterial population in medium containing 600 mg NO₃---N and essential biogens. It was found that at the most favourable C:N RATIO = 1.0 the efficiency of denitrification depended on nitrate load as well as on cell residence time. At nitrate loads in the range 220–670 mg NO₃---Nl⁻¹ day⁻¹ (0.08–0.14 mg NO₃---N mg⁻¹ day⁻¹) nitrogen removal was 0.6–0.12 mg N mg⁻¹ day⁻¹, respectively. Denitrification unit biocenosis was composed of bacteria, fungi and protozoa. The number of denitrifying bacteria per sludge weight unit within the studied range of nitrate loads was constant and averaged 23 × 10⁷ cells mg⁻¹.     

关于水泥密度和比表面积检测准确性的研究

解读了水泥密度和比表面积的测试方法标准,通过试验分析了测试结果准确性的影响因素,并提出提高准确性的方法与建议。     

比粒度--一种表示砂石粒度的新概念

经多年反复研究,发现了集料粒度与表面积关系法则,提出了以“比粒度”表述砂石粒度的新方法,解决了以“细度模数”表述砂子细度的不足之处,即解决了细度模数与不同细度砂子的比表面积没有相关性的问题.     

用超细矿渣微粉配制C80混凝土的研究

利用矿渣微粉及粉煤灰的活性,采用P·O42.5R级水泥和聚羧酸高效减水剂等配制C80高性能混凝土.通过正交试验对比研究表明,掺活性指数较高的矿渣粉可以配制C80混凝土,该混凝土具有成本低、取材方便、耐久性好等特点.     

Simultaneous nitrification/denitrification in a biofilm airlift suspension (BAS) reactor with biodegradable carrier material

Simultaneous nitrification and denitrification in one reactor has been realized with different methods in the past. The usage of biodegradable biocompounds as biofilm carriers is new. The biocompounds were designed out of two polymers having different degradability. Together with suspended autotrophic biomass the biocompound particles were fluidized in an airlift reactor. Process water from sludge dewatering with a mean ammonium nitrogen concentration of 1150 mg L⁻¹ was treated in a two stage system which achieved a nitrogen removal of 75%. Batch experiments clearly indicate that nitrification can be localized in the suspended biomass and denitrification in the pore structure of the slowly degraded biocompounds. Images taken with CLSM prove the concept of the pore structure within the biocompounds, which provide both a heterotrophic biofilm and carbon source.