Behavior of solid carbon sources for biological denitrification in groundwater remediation

The present study was conducted to compare the behavior of wheat straw, sawdust and biodegradable plastic (BP) as potential carbon sources for denitrification in groundwater remediation. The results showed that a greater amount of nitrogen compounds were released from wheat straw and sawdust than from BP in leaching experiments. In batch experiments, BP showed higher nitrate removal efficiency and longer service life than wheat straw and sawdust, which illustrated that BP is the most appropriate carbon source for stimulation of denitrification activity. In column experiments, BP was able to support complete denitrification at influent nitrate concentrations of 50, 60, 70, 80, and 90 mg NO(3)(-)-N/L, showing corresponding denitrification rates of 0.12, 0.14, 0.17, 0.19, and 0.22 mg NO(3)(-)-N.L(-1).d(-1).g(-1), respectively. These findings indicate that BP is applicable for use as a carbon source for nitrate-polluted groundwater remediation.     

Use of agro-food wastewaters for the optimisation of the denitrification process.

The aim of this work was to study the feasibility of the denitrification process enhancement, in the Ciudad Real (Spain) WWTP, by dosing agro-food wastewaters generated nearby the city. The studied agro-food wastewaters were characterised by a high COD and low nutrients concentration. The denitrification rates with these wastewaters were lower than those obtained either with acetate or urban sewage, however the dose of agro-food wastewaters raised significantly the denitrification capacity in the WWTP because of the significant increase of easily biodegradable substrates in the wastewater. From the laboratory NUR batch test it was observed that the best agro-food wastewater to enhance the denitrification process was that coming from tomato processing, which presented an average denitrification rate of 1.9 mg NOx-N/(g VSS.h) and an average denitrification yield of 0.2 mg NOx-N/mg COD. The viability of the use of tomato processing wastewater was checked in a pilot plant optimised for urban sewage treatment with biological nutrient removal. The optimum dose, 5.9 mg COD/mg NOx-N, was applied and 99% of the nitrate was removed from the wastewater without influencing negatively either the COD or P effluent concentrations.     

Nitrogen isotope fractionation as a tool for determining denitrification in constructed wetlands.

Constructed wetlands (CWs) treat municipal wastewater through the retention of nutrients and particles. The retention of nitrogen (N) was studied in the laboratory using columns and meso-scale trenches filled with shellsand and light-weight aggregates (LWA). The objective was to examine whether measuring the natural abundance of delta15N in NO3(-) could be used to estimate the relative contribution of denitrification to the total NO3(-) removal in these treatment systems. In both the columns and the trenches it was seen that denitrification was more efficient in shellsand and LWA collected from on-site treatment systems compared to new LWA. This was due to the high pH value (about 10) of new LWA. The enrichment factors (epsilon) from the column study were in general lower than values found in laboratory tests of isotope discrimination in denitrification, but similar to epsilon values found for denitrification in groundwater systems. No enrichment factors could be found for the trench study due to simultaneous denitrification and nitrification and inhomogeneous N transformation patterns. When NH4+ was partially nitrified in the upper parts of the trench, this diluted the 15N enrichment of NO3(-) due to denitrification. Thus, in systems with high NH4+ concentrations and partial aerobic conditions, the method of natural abundance is not suitable for estimating the relative contribution of denitrification to the total NO3(-) removal.     

Distillery wastes as external carbon sources for denitrification in municipal wastewater treatment plants

In this study, by-products from alcohol production were examined in terms of their potential application as external carbon sources for enhancing denitrification in biological nutrient removal systems. Three types of batch tests were used to compare the effects of the distillery by-products, such as fusel oil, syrup and reject water, on the non-acclimated activated sludge. Much higher nitrate utilization rates (NURs) were observed for the latter two carbon sources. In the conventional NUR measurements (one-phase experiments), the observed NURs with syrup and reject water were 3.2-3.3 g N/(kg VSS h) compared with 1.0 g N/(kg VSS h) obtained for fusel oils from two different distilleries. When the carbon sources were added at the beginning of the anoxic phase preceded by an anaerobic phase (two-phase experiments), the NURs were 4.2 g N/(kg VSS h) (syrup and reject water) and 2.4-2.7 g N/(kg VSS h) (fusel oils). The heterotrophic yield coefficient, determined based on the conventional OUR measurements, varied in a relatively narrow range (0.72-0.79 g COD/g COD) for all the examined carbon sources. Due to advantageous composition (much higher COD concentrations and COD/N ratios), fusel is a preferred carbon source for practical handling in full-scale wastewater treatment plants.     

酒类废水特征及其作为反硝化碳源的可行性

研究了酒类废水作为污水处理厂反硝化碳源的可行性.首先分析了不同类型酒类废水的物化和微生物群落特征.活性污泥添加酒类废水后,反硝化速率为1.85～2.60 mgNO3-N/(gVSS.h),效果好于对照组乙酸钠(1.72).抑制性测试表明添加酒类废水对活性污泥的硝化速率、释磷和吸磷速率均无显著不利影响.残留COD测试表明添加酒类废水对出水COD的影响较小可控.碳源效率测试表明低浓度过滤酒类废水最佳,其碳源消耗质量比(△COD/△N)为7.1,低于对照组乙酸钠(10.9).综上所述,经过适当处理后的酒类废水是优质反硝化碳源.     

Influence of wastewater composition on denitrification and biological P-removal in the S-DN-P-process: effects of different substrates (a).

The influence of the wastewater composition on the denitrification and biological P-elimination in the Sorption Denitrification P-eliminations Process (S-DN-P-process) was examined. Batch type experiments were performed to examine the influence of various substrates. Among the three different substrates prepared, only 11% COD(filt) was taken up from starch containing wastewater (starch preparation). Acetate is an easily degradable substrate for the biological P-elimination, and showed ca. 30% more acetate was taken up compared to the raw wastewater (wastewater preparation). Starch is a barely degradable substance, because it must be hydrolysed before digestion. Starch initially sorbs slowly (approximately 30 min), and may be hydrolysed during this time. During the investigations, the biological P-elimination and the denitrification were found to be dependent on the wastewater composition. The P-elimination rate was determined to be 38% with the acetate preparation, while a P-elimination of 6% was obtained with the starch preparation. The wastewater preparation showed a P-elimination of 56%, the value of which was almost 18% more than the acetate preparation. The biological P-elimination and denitrification depend not only on the dissolved parts in the wastewater, but also on the undissolved content.     

一体化生物膜脱氮反应器介绍

根据传统好氧硝化和缺氧反硝化生物脱氮的工艺原理,开发了一体化生物膜反应器,用于生活污水的脱碳和脱氮处理。反应器分为好氧区、缓冲区和缺氧区,分别设置了不同密度的弹性纤维填料。反应器对CODCr和TN的去除率分别达96%和80%。     

A distillery by-product as an external carbon source for enhancing denitrification in mainstream and sidestream treatment processes

The use of fusel oil as an 'alternative' carbon source for denitrification in the mainstream and sidestream treatment processes was studied. Research comprised two kinds of batch experiments as well as acclimation of process biomass to external carbon sources. In the conventional nitrate utilization rate (NUR) measurements (one-phase experiments with non-acclimated biomass), the NUR with fusel oil was 1.4-1.7 g N/(kg VSS·h which was comparable to NUR with ethanol and with slowly biodegradable fraction of the settled wastewater. When fusel oil was added at the beginning of the anoxic phase, preceded by an anaerobic phase (in two-phase experiments with non-acclimated biomass), the NURs of 2.5-2.9 g N/(kg VSS·h) were comparable to the tests without the addition of any external carbon sources. The addition of fusel oil and ethanol resulted in a significant enhancement of the denitrification efficiency in lab-scale sequencing batch reactors treating sludge reject water. The NURs continuously increased from below 1 g N/(kg VSS·h) to over 10 g N/(kg VSS·h) over the entire 4-week operational period, indicating gradual acclimation to the substrate. The overall total N removal efficiency reached ～90%.     

城镇污水生物脱氮达标排放工艺选择

《城镇污水处理厂污染物排放标准》(GB18918—2002)中规定了新的氮排放标准。通常污水处理厂采用生物脱氮处理工艺时,出水中氮含量远低于规定值,为此,提出了生物脱氮处理工艺出水水质恰好达标的几种工艺,以节约投资与运行费用。     

MBR的脱氮除磷工艺研究

采用厌氧/缺氧池/好氧MBR工艺处理模拟的城市生活污水,就系统主要的运行参数对氮磷去除的影响进行了研究.结果表明:TN、TP、NH3-N去除率分别达到80%、90%、95%以上,出水各项指标完全满足城市杂用水水质标准的要求.     

Possible denitrification technology for small settlement water supplies

A biological denitrification technology has been developed and tested. In the laboratory, the denitrifying bacteriumHyphomicrobium X was immobilised on polyurethane and polyvinylacetate foams, glass beads, glass wool, coarse river sand and also entrapped in alginate beads. In all cases the bacteria retained their capacity to actively denitrify with methanol as the carbon source. The establishment times and longevity of the bacteria on polyurethane and sand columns was studied, as was the effect of methanol/nitrate ratios on the denitrification process in flow-through experiments. Conditions were achieved where both nitrate and methanol were removed stoichiometrically. Complete removal of nitrate could be achieved in the temperature range 4 to 48 °C. Flow-through and batch procedures were investigated and a prototype batch system was developed which was capable of treating 200 litres of nitrate-containing water per day.     

污染河道水质强化脱氮生化工艺研究

应用生化工艺对河道污染水体进行修复是目前最经济的一条途径,但其面临的一个突出问题是在生物脱氮过程中可利用碳源不足,从而影响其处理效果。本研究采用分段进水生物接触氧化工艺来强化受污染水脱氮性能,与传统单点进水方式相比,两段进水对有机物和总氮去除率有显著提升,CODMn平均去除率从50.6%提升到66.3%;总氮平均去除率从31.4%提升到60.9%。沿程统计硝化细菌和反硝化细菌数量,硝化细菌主要集中在曝气区,数量为5.58×106,反硝化细菌主要集中在非曝气区的中后段,数量为6.49×105。同时检测沿程溶解氧和各氮素浓度,溶解氧浓度沿程降低,最后出水仅为0.2 mg/L;氨氮在曝气区转化为硝态氮,在非曝气区硝态氮还原成氮气,其结果进一步证实了硝化细菌和反硝化细菌的分布特征。     

不同固态碳源用于反硝化去除污水处理厂尾水中硝态氮的研究

针对污水处理厂尾水氮素高度硝化的现状,研究了不同固体碳源在不同条件下的反硝化速率及对硝态氮的去除率。结果表明:麦秆、PBS和PHAs较其他固态碳源具有更好的脱氮效果,25℃为最适宜反应温度;进水硝态氮浓度与硝态氮去除率之间有很好的相关性;随着反应时间的延长,各碳源脱氮效率也在不断加速,至24 h时,PBS、PHAs和麦秆对应的去除率分别为98.53%、93.41%和73.26%。对三种碳源反应前后的表面进行扫描电镜分析,证实了三种碳源作为反硝化固体碳源的可行性。COD反弹和硝态氮积累试验表明,麦秆更适用于污水处理厂尾水的生态净化工艺。     

Chemical denitrification for nitrogen removal from landfill leachate.

A new system that removes nitrogen from landfill leachate and other waste waters with similar properties has been proposed with nitritation (i.e. oxidation of ammonium to nitrite) of half of the influent ammonium followed by chemical denitrification with a reaction between equal amounts of ammonium and nitrite to form nitrogen gas. Chemical denitrification occurs at high concentrations and the reactions were studied in combination with a concentration step. Studied concentration methods were freezing/thawing and evaporation/drying. Chemical denitrification is well-known in inorganic chemistry and has been observed in natural systems. Studies in laboratory were focused on chemical denitrification and showed that nearly complete removal of soluble nitrogen can be obtained in evaporation/drying of water solutions or leachate with equal amounts of ammonium and nitrite. Freezing/drying was less efficient with a removal of about 50-60% at high initial concentrations. Chemical denitrification is much influenced by concentration, pH-value, temperature and some compounds in leachate have an inhibiting effect on the reaction. Factors as safety (ammonium nitrite as a salt is explosive above 60 degrees C) and possible side-reactions as formation of ammonia and nitrogen oxides must be carefully evaluated before use in full-scale. Conductivity is a suitable parameter to follow-up the chemical denitrification process.     

Influence of temperature on microbial colonisation of clayey schist as a support media of a submerged filter for groundwater denitrification.

The effect of temperature on biofilm formation and denitrification activity was evaluated. Assays were made in a lab-scale submerged filter for the denitrification of polluted groundwater, with and without a previous inoculation. The inoculation was carried out with a selected strain of Pseudomonas mandelii. Different temperatures were tested: 5, 10, 20 and 30 degrees C. Biofilm observations were made, and monitoring of the denitrification capacity of the system was maintained during the experiment. Our results showed that both colonisation of the support material of the filter and biofilm maturity have a dependency with temperature, with an optimum temperature of 20 'C if the system was previously inoculated with the Pseudomonas mandelii strain. For a correct achievement of the denitrification process, a previous inoculation of the system is essential. Although the development of a biofilm from the natural microbiota present in the groundwater is possible, it is not capable to adequately denitrify polluted groundwater. In terms of the correct achievement of the denitrification process, temperature affects the operation of the system at cold environments, although the use of Pseudomonas mandelii strain A103 allows denitrification at 10-30 degrees C with very good results (above 90% removal), affecting only to the time needed for the stabilisation of the system.     

猪场废水脱氮处理工程实践

猪场废水氨氮浓度高、处理难度较大,采用IC—SBBR—人工湿地工艺,在进水CODCr6000～8000mg/L,NH3—N258～635mg/L、pH7.5～8.5,出水CODCr80～300mg/L、NH3—N6～78mg/L、pH7.8～8.4,达到《畜禽养殖业污染物排放标准》(GB18596—2001)要求。工程实践表明,SBBR具有对猪场废水氨氮较强的抗冲击负荷能力,且对氨氮的去除率平均为77%。     

Six years of operation of a fluidised bed reactor for denitrification.

At Himmerfj?rden wastewater treatment plant, a fluidised bed reactor for nitrogen removal has been operated since 1997. Despite its small footprint, the system enables a far-reaching nitrogen removal. The current nitrate reduction in the reactor is 95%. The reduction of total nitrogen at the wastewater treatment plant is 80-90% at normal operation. The concentration of nitrate in the effluent is easily controlled by changing the dose of carbon. As part of a series of full-scale experiments, the plant has, for the last two years, been operated without denitrification for a couple of months during spring/summer, in order to benefit a favourable N/P-ratio in the recipient and to counteract the growth of nitrogen fixing blue-green algae, When resuming the dosage of carbon, full denitrification was re-established in about two weeks. Important factors to take into consideration when operating the fluidised bed reactor are the abrasive characteristics of the carrier material (sand), the increased concentration of suspended solids in the effluent, and the importance of a suitable N/P-ratio in the influent, as lack of phosphorus might cause an uncontrolled microbiological growth.