Determination of the dynamics of the odour release from a pig house, using an electronic odour sensor.

The widely fluctuating operating conditions in pig husbandry, due to climatic and biological changes (changes in temperature and air flowrate between day and night, as well as between summer and winter, increasing animal mass during the fattening process, etc.) exert a significant influence on the amount of actual odour emission. The project presented here comprised the measurement of seasonal (fattening course), daytime-related, and short-term (feeding) dynamic effects of odour release, as well as the identification of potential factors which influence the amount of odour emitted. In parallel with "classic" olfactometry, an electronic odour sensor with a chemosensor array of ten metal oxide sensors was employed. The highest odour emissions are measured on hot summer days, while the lowest emissions were determined on cold winter days. On the one hand, the sensor signals of the electronic odour sensor exhibited considerable differences on days with large volume flow alterations. On the other hand, continuous measurement with the electronic odour sensor allowed changes in the gas- and odorant composition of the exhaust air during feeding times to be shown. From the measurement results, recommendations for odour sampling, the consideration of seasonal odour emission fluctuations, and the use of electronic odour sensors for the evaluation of odour emissions have been derived.     

Odour and ammonia removal from pig house exhaust air using a biotrickling filter.

Odour from agricultural activities, such as the spreading of manure and the housing of animals, is increasingly being considered a nuisance in densely populated countries like the Netherlands. The objective of this research was to study the odour removal from pig house exhaust air by a biotrickling filter that had been implemented for ammonia abatement. At a regular pig production farm, the performance of a running full-scale biotrickling filter was studied for 72 days. Ammonia and odour removal efficiency were on average 79% and 49% respectively. Ammonia removal appeared to be based on an unintended accumulation of ammonium and nitrite in the system, instead of on production and discharge of nitrate. The odour removal efficiency showed a large variation that, for a major part, about 80%, could be attributed to actual changes in the performance of the biotrickling filter. These changes were probably caused by variations in the composition of the air that were not completely reflected by the olfactometrically measured odour concentration, as the many different components that make up the odour each have different removal characteristics. It seemed that the biotrickling filter was operated below its maximum absolute odour removal capacity [OUE/(m3 filter)/s], which means that the absolute odour removal will probably rise at increasing load. It was, however, not possible to distinguish between the influence of either the odour load or the odour concentration on the odour removal, because of a positive correlation between the odour concentration and the air flow. To increase the odour removal efficiency (%), the design of the filter probably needs to be optimised for both well and poorly water-soluble odour components.     

Removal of geosmin and 2-methylisoborneol by biological filtration.

The quality of drinking water is sometimes diminished by the presence of certain compounds that can impart particular tastes or odours. One of the most common and problematic types of taste and odour is the earthy/musty odour produced by geosmin (trans-1, 10-dimethyl-trans-9-decalol) and MIB (2-methylisoborneol). Taste and odour treatment processes including powdered activated carbon, and oxidation using chlorine, chloramines, potassium permanganate, and sometimes even ozone are largely ineffective for reducing these compounds to below their odour threshold concentration levels. Ozonation followed by biological filtration, however, has the potential to provide effective treatment. Ozone provides partial removal of geosmin and MIB but also creates other compounds more amenable to biodegradation and potentially undesirable biological instability. Subsequent biofiltration can remove residual geosmin and MIB in addition to removing these other biodegradable compounds. Bench scale experiments were conducted using two parallel filter columns containing fresh and exhausted granular activated carbon (GAC) media and sand. Source water consisted of dechlorinated tap water to which geosmin and MIB were added, as well as, a cocktail of easily biodegradable organic matter (i.e. typical ozonation by-products) in order to simulate water that had been subjected to ozonation prior to filtration. Using fresh GAC, total removals of geosmin ranged from 76 to 100% and total MIB removals ranged from 47% to 100%. The exhausted GAC initially removed less geosmin and MIB but removals increased over time. Overall the results of these experiments are encouraging for the use of biofiltration following ozonation as a means of geosmin and MIB removal. These results provide important information with respect to the role biofilters play during their startup phase in the reduction of these particular compounds. In addition, the results demonstrate the potential biofilters have in responding to transient geosmin and MIB episodes.     

Nitrification processes in scrubbing liquid of an exhaust air treatment system of a large-scale pig housing facility

The use of multi-staged exhaust air treatment systems is an effective method of substantially reducing the emission of ammonia, dust particles and odorous substances. Wet filter walls are able to absorb large amounts of ammonia when scrubbing fluid containing sulphuric acid is used. In addition, due to their large surface areas and the permanent supply of oxygen and nutrients, wet filter walls provide a basis for the development of biofilms containing nitrogen-converting bacteria. Cyclic nitrification processes could be observed in a two-stage exhaust air treatment system, which had been converted to function as a regulated process control system (elutriation at κ = 20 mS cm(-1); pH 6.5-6.8). With this system, the sulphuric acid requirement was periodically reduced every 6-8 weeks to less than 1 kg H(2)SO(4) per fattening place and year. There was an increased formation of nitrous oxide gas during nitrification after the wet filter stage. Electron-microscopic images of the biofilm growing on the wet filter wall showed aggregates of possible ammonium-oxidising and nitrite-oxidising bacteria.     

The anatomy of odour wheels for odours of drinking water, wastewater, compost and the urban environment.

In the drinking water and air pollution fields, odour quality characterisation and intensity of each odour characteristic needs to be developed to evaluate the causes of the odours present. Drinking water quality characterisation has matured to the point where an "odour wheel" is described and the primary chemicals producing the odour are known and therefore a potential treatment can be defined from the odours reported. Sufficient understanding of the types of odorous compounds that can arise from wastewater and compost treatment processes and odours in the urban environment are starting to emerge. This article presents the anatomy of the odour wheels. It is hoped that the foundation of odour wheels will evolve as odour quality data are reported and linked with chemical causation. The compost and urban odour wheels are presented in print for the first time.     

空气曝气与纯氧曝气生物滤池应用于污水深度处理的研究

采用两种不同气源的曝气生物滤池对污水处理厂二级出水进行深度处理中试研究.结果表明,空气曝气和纯氧曝气生物滤池对COD_(Mn)的去除率相近,分别为30.5%和30.9%;以纯氧为气源的生物滤池硝化能力远强于空气曝气生物滤池,氨氮总去除率77.4%,出水氨氮为2.1～6.3 mg/L;纯氧曝气提高了滤池上部氨氮去除效果,维持滤池内溶解氧在6 mg/L以上,沿水流方向使pH逐渐下降.纯氧曝气生物滤池是污水深度处理中去除氨氮的有效工艺.     

The odour of digested sewage sludge--determination and its abatement by air stripping.

This paper describes a project to investigate the odour of sewage sludge after anaerobic digestion. The impact of air stripping on the odour of liquid sludge and on the quality of the dewatered product was evaluated at a full-scale sludge treatment installation. A continuous and a batch air-stripping mode were tested. Odour samples were collected during air stripping from the liquid sludge and from the biosolids surface during long term storage. The biosolids were also analysed for hedonic tone and for their potential odour expressed as an odour unit per unit mass. The odour emission profiles for continuous and batch air stripping demonstrated a reduction in the overall (time weighted) emissions during a 24 hr-period compared with emissions from the quiescent liquid storage tank. The averaged specific odour emission rate (Esp) of the biosolids derived from the continuous process was only 13% of the Esp of the biosolids derived from unaerated liquid sludge during the first month of storage. The results of the total potential odour and the hedonic tone of the biosolids underpin the beneficial effects of the air stripping. Odour dispersion modelling showed a noticeable reduction in overall odour impact from the sludge centre when air stripping was applied. The reduction was primarily associated with the reduced odour from stockpiled biosolids. The continuous air-stripping mode appeared to provide the greatest benefits in terms of odour impact from site operations.     

基于藻类连续生长的生物慢滤池深度净化污水的研究

利用藻类连续生长的生物慢滤池开展污水深度净化实验,通过分析生物慢滤池不同深度区域污染物浓度,考察其对氮磷等污染物质的降解规律。研究结果表明:在生物慢滤池中,总氮的去除主要依靠填料表层中微生物的降解和藻类吸收作用,其降解幅度可达31.5%;总磷的去除主要依靠滤柱深层的滤料的吸附作用以及上覆水中藻类的吸收,其降解幅度可达47.0%;氨氮浓度的降低主要依靠硝化转化作用和滤池上覆水表面的挥发作用,其降解幅度为21.8%。可见,生物慢滤池的上覆水和填料表面存在有大量的微生物和藻类,其对水质的净化起到了关键作用。     

Treatment of source-separated urine by a combination of bipolar electrodialysis and a gas transfer membrane.

Urine contains nutrients which can be applied usefully as a fertiliser in agriculture, but the relatively high pH can lead to ammonia evaporation. Electrodialysis with bipolar membranes was combined with an additional mass transfer unit in order to render a product containing ammonium and phosphate at a low pH. In one case, the additional mass transfer unit consisted of bubble columns placed in acid and basic concentrate streams, connected with a circulating gas phase. In the other case, the unit consisted of a gas-filled (hydrophobic) membrane placed in between the circulating acid and basic concentrate streams. The results showed that ammonia was transferred through the gas phase, but also carbonate, which is present in stored urine originating from the hydrolysis of urea. Although the pH in the product stream decreases initially, it rises above pH 7 at longer operation times. This pH increase can be attributed to a combination of proton compensating effects. The use of ammonia-selective membranes for the transfer into the acid concentrate could provide a solution to generate an ammonium phosphate product at low pH and high recoveries.     

Evaluation of a novel wind tunnel for the measurement of the kinetics of odour emissions from piggery effluent.

A novel laboratory wind tunnel, with the capability to control factors such as air flow-rate, was developed to measure the kinetics of odour emissions from liquid effluent. The tunnel allows the emission of odours and other volatiles under an atmospheric transport system similar to ambient conditions. Sensors for wind speed, temperature and humidity were installed and calibrated. To calibrate the wind tunnel, trials were performed to determine the gas recovery efficiency under different air flow-rates (ranging from 0.001 to 0.028m3/s) and gas supply rates (ranging from 2.5 to 10.0 L/min) using a standard CO gas mixture. The results have shown gas recovery efficiencies ranging from 61.7 to 106.8%, while the average result from the trials was 81.14%. From statistical analysis, it was observed that the highest, most reliable gas recovery efficiency of the tunnel was 88.9%. The values of air flow-rate and gas supply rate corresponding to the highest gas recovery efficiency were 0.028 m3/s and 10.0 L/min respectively. This study suggested that the wind tunnel would provide precise estimates of odour emission rate. However, the wind tunnel needs to be calibrated to compensate for errors caused by different air flow-rates.     

Variability and repeatability of olfactometric results of n-butanol, pig odour and a synthetic gas mixture.

For the purposes of a research project for the Flemish authorities, olfactometric measurements were carried out at six closed pig farms and six fattener farms. The results of these olfactometric measurements were compared with the olfactometric results of n-butanol samples and samples of a synthetic gas mixture of ethanethiol, methylacetate and 2-propanol in nitrogen, both analysed on the same days as the air samples from the pig farms. The results of the n-butanol tests for all panellists showed that nobody was qualified according to the CEN criteria, and that, consequently, these criteria are rather stringent. Comparing the variability of the results for the three different odours showed that the mean and standard deviation of the mean variance were not significantly different for the three odour types, which means that the repeatability of the panellist results was equal for the examined odour types. The principle of traceability was checked by comparing the variance of the n-butanol, pig odour and synthetic mixture ratio. For the complete dataset, the principle of traceability could not been proven for n-butanol. For the restricted dataset, the principle of traceability was more valid for n-butanol than for the mixture, but differences were small. Finally, normalization was looked for with regard to olfactometric measurements of air samples from pig arms based either on n-butanol or on the synthetic mixture. Both models had low determination coefficients, but the model based on the synthetic mixture gave better results than the one based on n-butanol.     

Sewer odour abatement monitoring - an Australian survey

Odourous emissions from sewer networks can significantly impact a local population causing odour annoyance. A survey of nine Australian wastewater utilities that serve over 8.4 million people and operate over 59,000 km of sewer networks was undertaken to summarise the current monitoring practices in Australia with the view to assist the water industry to further improve their practices in operating and monitoring sewer odour abatement systems. Results indicated that most odour abatement systems were monitored through complaints from the surrounding community, H(2)S is the dominant online and offline monitoring parameter and that a variety of different H(2)S instruments are used across the industry but the reported use is dominated by two manufacturers. The monitoring data were primarily used for decision making and diagnosis, and there was limited use of non-H(2)S odourant analysis. The water industry had several significant limitations in terms of its inability to provide gas flow data, process monitoring and complaint data as well as being able to link process monitoring data with maintenance information for instrumentation. The improved collection and management of this data would yield benefits to the water industry in terms of odour abatement design, performance and management.     

Interaction of oxygen concentration and retention of pollutants in vertical flow constructed wetlands for CSO treatment.

The EU Water Framework Directive (WFD) calls for a good quality of all water bodies. Retention soil filters (RSF) have been developed to treat discharges from combined sewers systems. RSF have proved over the past 15 years to be the most effective measure to meet the EU WFD standards, especially for small or particularly sensitive receiving waters, which require an enhanced reduction of emissions from combined sewer overflows (CSOs). The paper presents results from laboratory-scale experiments, in which the oxygen measurement in the filter plays a main role. The results show remarkable differences in oxygen concentrations in different filter depths. The highest oxygen consumption takes place in the upper part of the filter. In the lower part the re-aeration of sewage from the soil air dominates. This indicates that the biological activity is limited to the upper part of the filter. The availability of oxygen in the filter is a sign for degradation of wastewater compounds (ammonium, COD) under certain conditions and already takes place during the filter operation. The removal of ammonium especially cannot be strictly divided into phases of sorption during the loading and oxidation during the dry period any more.     

曝气生物滤池降解规律试验研究

采用实际分散型生活污水作为试验原水,对曝气生物滤池的降解规律进行了试验研究。结果表明,与传统的观点不同,曝气生物滤池在处理低浓度有机废水时并不发生严格的有机物与氨氮的分段去除现象,有机废水氨氮与有机质基本在同一区域内去除,滤料在10～40cm段的去除率增长速度最快,在70cm之后去除率的增长开始逐渐变缓。在进口段,由于有机质浓度高,供氧充足,有机质的去除率较高;由于异养菌和氨化菌的作用,氨氮浓度在进口段不但不减少,反有微小升高。     

Ecological assessment of waste air treatment systems in the case of biological waste treatment.

In this paper, the authors present a technique aimed at increasing the efficiency of biological waste air treatment. The objective is to modify the existing biological waste air treatment systems (i.e. biofilters) to reduce the emitted substances and their potential environmental impacts. The principle of the ionization system is described, along with the first experiences of applying those methods during the rotting process. The investigated system is evaluated by means of life cycle impact assessment, with a focus on odour. It is demonstrated which of the measured substances (i.e. VOC) can potentially contribute to the odorant concentration. Further, it is shown which odour-intensive substances can be reduced by deploying ionization. Finally, the authors respond to the fact that the cleaning efficiency of ionization strongly depends on the humidity of the treated waste gas stream.     

江苏省2006-2015年水生态环境质量变化特征分析

以2006-2015年江苏省地表水监测数据为基础,统计分析了该10年间的水生态环境质量特征和趋势,并对太湖湖体主要水质指标的变化特征进行了拟合。结果表明:全省水生态环境质量在2006-2015年间总体呈改善趋势,水质主要污染指标均有不同程度下降;太湖主要水质指标下降趋势显著,高锰酸盐指数和氨氮浓度基本进入稳定期,总氮浓度也接近稳定期,太湖总磷浓度仍处于不稳定的变化期;"十二五"期间全省水生态环境改善的幅度均较"十一五"有所收窄,全省水生态环境治理进入攻坚克难阶段。     

Ion selective transistor modelling for behavioural simulations.

Computer aided design and simulation of complex silicon microsystems oriented for environment monitoring requires efficient and accurate models of ion selective sensors, compatible with the existing behavioural simulators. This paper concerns sensors based on the back-side contact Ion Sensitive Field Effect Transistors (ISFETs). The ISFETs with silicon nitride gate are sensitive to hydrogen ion concentration. When the transistor gate is additionally covered with a special ion selective membrane, selectivity to other than hydrogen ions can be achieved. Such sensors are especially suitable for flow analysis of solutions containing various ions. The problem of ion selective sensor modelling is illustrated here on a practical example of an ammonium sensitive membrane. The membrane is investigated in the presence of some interfering ions and appropriate selectivity coefficients are determined. Then, the model of the whole sensor is created and used in subsequent electrical simulations. Providing that appropriate selectivity coefficients are known, the proposed model is applicable for any membrane, and can be straightforwardly implemented for behavioural simulation of water monitoring microsystems. The model has been already applied in a real on-line water pollution monitoring system for detection of various contaminants.     

Experience with the upgrading of 14 treatment plants to N & P removal in the municipality of Aarhus

The experience with the upgrading of 14 treatment plants to N and P removal is presented. For all plants it has been possible to fulfil the effluent standards. Through process optimization it has been possible to achieve * stable biological P-removaL The introduction of control systems based on on-line sensors for ammonia, nitrate and phosphate has resulted in a more stable effluent quality and an increased capacity. The experience also shows mat it can be very difficult to predict and control the changes in the industrial load. From mis it is concluded that instead of spending a lot of time on fine-tuning the design criteria in the design phase, it may be better to incorporate a considerable flexibility into the design, allowing the processes to be adjusted to the changing operational conditions during time.     

Use of non-thermal plasma and UV-light for removal of odour from sludge treatment

Non-thermal plasma (NTP) systems can be used for abatement of odour nuisances. Odour reductions are achieved by radical-initiated oxidation and dust collection in the plasma reactor. For some emissions a sequence of NTP followed by UV-light can improve the odour reduction further. This study was conducted to evaluate the efficiency of NTP technology combined with UV-light towards odour emissions from sludge treatment. Air from a pilot sludge dryer was treated with a pilot NTP and a UV unit. The effect of using an acid scrubber upstream the NTP system was also tested. Thermal desorption gas chromatography and mass spectrometry (TD-GC/MS) was used to analyse samples taken from the inlet and the outlet of the NTP system. The TD-GC/MS used was also equipped with a sniffing port that made it possible to record odour-active compounds eluting from the column. Relative amounts of odour-active compounds in the inlet and the outlet flow from the NTP system were compared. Bag samples from inlet and outlet were also separately analysed by an external lab and by two operators using a one-man olfactometer, a modified NasalRanger(TM). These results indicated a significant odour removal efficiency of 70-90% depending on the settings and combinations of abatement equipment.     

生物慢滤池用于污水深度处理的实验研究

利用生物慢滤池对人工模拟污水和西安市某污水处理厂的二级出水进行了深度净化处理实验,通过分析进出水中氮、磷含量和高锰酸盐指数及上层水和出水中的叶绿素a含量等指标,考察了生物慢滤池的净化效果。结果表明:生物慢滤池对人工模拟污水的处理效果较好,总氮、氨氮、总磷和高锰酸盐指数的去除率分别为66.4%、40.2%、66.4%和73.3%;深度净化污水厂二级出水,总氮、氨氮、总磷和高锰酸盐指数的去除率分别为35.1%、21.0%、30.2%和12.6%,去除率略低于人工模拟实验;生物慢滤池对叶绿素a有很好的截留效果,去除率分别为93.4%和66.4%;生物慢滤池处理后的再生水水质达到《城市污水再生利用景观环境用水水质》要求,可回用于城市景观水体,作为城市景观水体的补充水源,避免水体富营养化的发生。