A Nitrification Model for Mineral-Media Trickling Filters

Trickling filters represent the biological treatment component of about 70% of sewage works in the UK. Increasingly, they are being required to achieve a high degree of nitrification consistent with 95 percentile compliance with effluent discharge consents as low as 2 mg/1 of ammoniacal nitrogen. The available design models for the simultaneous removal of BOD and ammoniacal nitrogen are poor and have led to a lack of confidence in the ability of the process to comply with such standards.
This paper describes the development and application of an empirical model based upon the performance of eleven sets of trickling filters at five sites covering a wide range of organic and hydraulic loading.     

Ammoniacal Nitrogen Removal in Biological Aerated Filters: The Effect of Media Size

Recent legislation has led to stringent ammoniacal-nitrogen consents and the need for first-time sewage treatment in coastal areas where land is limited. This has led to the need to improve 'small footprint'sewage-treatment processes (such as biological aerated filters) which can be used for carbonaceous treatment, nitrification, or for combined treatment. The removal of ammoniacal nitrogen in filters containing different sizes of Lytag medium and operated for combined carbonaceous treatment and nitrification, was compared at different hydraulic and volumetric loading rates. The results suggest that filters containing the smallest media size (2–4 mm), gave optimum nitrification at ammoniacal-nitrogen loading rates up to 0.6 kg/m³. d. At higher loading rates there was a rapid decrease in nitrification for this size of medium but, with 2.8–5.6 mm medium, nitrification continued at loading rates up to 1 kg amm. N/m³ d. The filters containing larger media sizes (4–8 mm and 5.6–11.2 mm) exhibited low levels of nitrification above a loading rate of 0.2–0.4 kg amm. N/m³. d.     

Nitrification Trials at Dunnswood Sewage-Treatment Works and Process Modelling Using WRc STOAT

The paper describes an experimental programme on an existing full-scale plant to demonstrate the conditions which are necessary to achieve nitrification. The programme was guided by parallel computer modelling of the plant using the WRc STOAT simulation package. Nitrification was successfully achieved, and the studies and computer modelling indicated how the plant should be extended to provide year-round nitrification. The effect of storm flows on effluent quality was assessed for each process option. The effluent quality consent of 5 mg/l ammoniacal nitrogen as a 95 percentile was achieved, and there was a significant improvement in river water quality with respect to ammoniacal nitrogen.     

A design model for nitrification on structured cross flow plastic media trickling filters

An empirical model has been developed to predict the effluent ammoniacal nitrogen concentration from structured cross flow plastic media trickling filters operated over the range of BOD loadings 0.12–0.38 kg/m³/day and ammoniacal nitrogen loadings of 0.06–0.23 kg/m³/day. The model gives good predictions based on 24‐h average effluent concentrations over a range of filter depths, organic and hydraulic loading rates. When incorporated with suitable hydraulic models, effluent ammoniacal concentration can be predicted through the diurnal range. The data gathering for the model included depth profiles on three filters. These have shown that at all but the very highest BOD loadings, nitrification commences from the very top of the filter in the presence of soluble BOD loadings previously thought to preclude the development of nitrifying biomass. Several reasons have been proposed to explain this, with the key argument being that the efficient oxygen transfer afforded by the media design is sufficient to satisfy heterotroph and autotroph oxygen demand simultaneously.     

Operational Experience with Biological Aerated Filters1

Yorkshire Water has two full-scale biological aerated filters in operation. The first was installed at North Bierley sewage-treatment works for the tertiary nitrification of humus―tank effluent to secure consent compliance and ascertain if anticipated future standards could be achieved. The second was recently commissioned at Hedon sewage-treatment works for secondary treatment, as part of an evaluation of compact plant to meet the requirements of the urban waste water treatment Directive at coastal sites. The plant at North Bierley (near Bradford) is constructed mainly of steel and is designed to achieve an effluent quality of 10 mg/l suspended solids, 10 mg/l BOD, and 5 mg/l ammoniacal nitrogen. The plant at Hedon (near Hull) is constructed of concrete and is designed to achieve a 30 mg/l suspended solids and 25 mg/l BOD standard. Both plants have proved to be capable of meeting their respective effluent requirement. For each works, the paper describes (i) the identification of the problem, (ii) the reasons for selecting the biological aerated filter process, (iii) details of the plant, (iv) operating experiences, and (v) plant performance.     

Operational experiences with structured plastic media filters: 10 years on

The performance of 10 cross flow structured plastic media trickling filter plants is discussed. The sites are arranged in a number of configurations with the plastic media filters operating as sole secondary process units, in parallel with other process units or in double filtration configuration. Data for 2003 and 2004 show that the plants are performing well. Data are presented for the plastic media filter stream where it is available. Two operational problems are discussed; overgrazing of nitrifying biofilms by excessive populations of snails and loss of nitrification performance in cold weather, particularly on smaller sites. Overgrazing by snails, identified as Lymnaea peregra has been controlled on one site by the annual treatment of an isolated filter with high ammoniacal nitrogen strength sludge dewatering liquors. On a second site suffering a similar problem the plastic media filter duty was changed from single filtration to being the primary filters in a double filtration system with existing stone media filters used for secondary filters. Loss of nitrification performance has been associated with excessive heat loss on some sites. Filters built as tower structures, with typically 4–5 m media depth allow easy control of airflow via restriction of the engineered ventilation openings at the base of the filter. This has been found to have a direct impact on the degree of cooling. However, airflow control on plastic media retrofitted into wide shallow stone media filter shells with 1.6–2 m media depth is more difficult. These structures offer less opportunity for control of airflow and associated heat losses.     

生物沸石滤池去除微污染水源水中氨氮的挂膜启动

对沸石滤料生物滤池处理微污染水源水中低浓度氨氮的挂膜启动性能进行了研究。试验结果表明,挂膜过程可以根据氨氮、亚硝酸盐氮、硝酸盐氮浓度的变化分为三个阶段：初期沸石发挥本身对铵离子的吸附交换性能,氨氮去除率达88％以上;中期开始出现生物硝化作用,亚硝酸盐积累明显,硝酸盐出水浓度不稳定,氨氮去除率稳定,但下降至65％左右;后期硝化反应稳定进行,亚硝酸盐迅速转化为硝酸盐,氨氮去除率稳定在60％以上。生物沸石滤池挂膜同时应考察亚硝酸盐氮、硝酸盐氮浓度变化,在出水亚硝酸氮明显积累后又稳定降低,且硝酸盐氮稳定积累时方可认为挂膜成功。进出水pH值的变化可以指示硝化反应的进行程度和生物膜形成阶段。     

The performance of tertiary lagoons in the United Kingdom: I

Two tertiary lagoons at Holmwood Sewage Treatment Works in the United Kingdom were sampled over a 1 year period. Each lagoon is approximately 39×28 m, receives domestic wastewater only, and serves approximately 2000 people. The aim of the work is to gain a greater understanding of the performance of the lagoon with respect to a number of chemical, biological and physical parameters. Samples were analysed for E. coli, enterococci, total coliforms, BOD, COD, suspended solids, ammoniacal nitrogen, nitrite, nitrate, total oxidised nitrogen and soluble phosphate. Occasional samples were also analysed for Cryptosporidium, Giardia and enteroviruses. Cusum charts were used to analyse the cumulative variations that were seen for the parameters being investigated, and had the advantage of emphasising their distinct seasonal trends. Although good percentage removals were seen, there was a lack of consistency in performance for all parameters over the year. No ammonia or phosphorus removal was found, although limited nitrification does appear to occur. None of the bacterial criteria for the WHO guidelines on wastewater reuse or the EC directive on bathing water were reached.     

双循环两相生物工艺处理生活污水的脱氮中试

采用双循环两相生物工艺(BICT)处理生活污水,探讨了在不同运行模式和试验条件下系统的脱氮性能.试验结果表明:BICT工艺通过设置独立的生物膜法硝化池,强化了系统的硝化效率,减轻了泥龄对系统脱氮的影响,提高了脱氮的稳定性.运行模式和硝化液回流比是影响系统脱氮效果的主要因素.在适宜的条件下,系统的脱氮率可达85%以上,出水TN<15 mg/L.     

Onset of severe nitrification in mildly nitrifying chloraminated bulk waters and its relation to biostability

Triggers of severe nitrification in distribution systems are still not clearly understood. Recently, the biostability concept was proposed to explain the chloramine residual below which signs of nitrification would be seen. To improve understanding, mildly nitrifying bulk water samples (nitrite less than 0.010mg-N/L) from Sydney Water distribution systems were incubated at constant temperatures and periodically analysed for nitrogenous compounds and total chlorine. Total ammoniacal nitrogen in the sample was between 0.25 and 0.35mg-N/L. Severe nitrification was triggered when chloramine residuals dropped below about 0.4mg/L - the critical threshold residual. In 45 such samples, the critical threshold residual was 0.2-0.65mg/L. The biostability concept was found to be useful in explaining the residual below which net growth of microorganisms begins. However, this alone could not predict the critical threshold residual. Different means of overcoming this problem are discussed. One of these is the use of the microbial decay factor method, since microbiologically assisted chloramine decay in the samples studied was found to be mostly the result of ammonia-oxidising bacterial activity. Nitrite levels in winter were found to be poor indicators of nitrifying status. Overall the results were found to be useful in controlling nitrification and to obtain early warning of severe nitrification.     

In situ nitrogen management in controlled bioreactor landfills

The characteristics of leachate from landfills vary according to site-specific conditions. Leachates from “old” landfills are often rich in ammonia nitrogen due to the hydrolysis and fermentation of the nitrogenous fractions of biodegradable substrates, with decreases in concentration mainly attributable to leachate washout. At landfills where leachate containment, collection and recirculation is practiced to accelerate decomposition of readily biodegradable organic constituents, leachate ammonia nitrogen concentrations may accumulate to higher levels than during conventional single pass leaching, thereby creating an ultimate leachate discharge challenge. Landfill leachate treatment options include complex and often costly sequences of external physical–chemical and biological processes for removal of high-strength organics and inorganics, including nitrogen. Therefore, this paper focuses on investigations with bioreactor landfill simulations to demonstrate the potential for in situ nitrogen removal in dedicated nitrification/denitrification zones. Using leachate recirculation, associated system modifications provided separate aerobic and anoxic zones for ammonia nitrogen transformations to nitrate and nitrogen gas, respectively. Results from the three simulated optional stages of methanogenesis, nitrification and denitrification indicated that nitrogen conversion and removal was dependent on the operational stage. Both separate and combined reactor operation with internal leachate recycle provided 95% nitrogen conversion. In contrast, combined reactor operation with single pass leaching provided a conversion efficiency per cycle ranging between 30–52% for nitrification and 16–25% for denitrification, thereby indicating the efficacy of using the landfill itself for attenuation of leachate ammonia nitrogen concentrations to levels acceptable for ultimate discharge.     

混凝吸附作用在垃圾渗滤液处理中的应用浅析

垃圾渗滤液具有高COD浓度、高氨氮、高重金属的特点,直接采用常规生物方法难以使处理过程正常运行。物化法作为垃圾渗滤液生物处理的预处理工艺,可降低渗滤液中的生物毒性,为后续生物处理提供良好条件。因此,对垃圾渗滤液预处理方法研究具有重要的理论意义和工程实践意义。     

生物脱氮新技术

结合生物脱氮机理,介绍了同步硝化反硝化、短程硝化反硝化及厌氧氨氧化等新的生物脱氮技术的机理、影响因素、代表工艺及其技术特点,指出这些技术都具有经济、高效、低耗的优势,符合可持续发展要求,应在此基础上进一步开发适合中国国情的生物脱氮工艺。     

新型生物脱氮工艺--OLAND工艺

OLAND工艺是基于亚硝酸型硝化-厌氧氨氧化脱氮技术而开发的生物脱氮新工艺.该工艺首先采用限制溶解氧浓度实现氨氮的部分亚硝化并实现亚硝酸盐氮的浓度积累,接着进行厌氧氨氧化反应,从而达到去除含氮污染物的目的.与传统生物脱氮工艺相比,该工艺具有耗氧量少、污泥产量少、不需外加碳源等优点.     

Nitrogen pollution and source identification in the Haicheng River basin in Northeast China

A survey was conducted in the Haicheng River near Liaodong Bay to analyze the characteristics and sources of the in-stream nitrogen pollution throughout the year 2010. The results indicated that the total nitrogen (TN) concentrations in the river water all exceeded the GB3838-2002 standard for Class V guideline of 2.0 mg/l at all sampling sites during the sampling seasons. Ammoniacal nitrogen (NH₃-N) dominated TN during the spring season, while nitrate nitrogen (NO₃-N) dominated during the summer and autumn seasons. Different forms of nitrogen had significant seasonal variations (p < 0.01 or p < 0.05). Only NH₃-N and NO₃-N displayed distinct spatial differences at p < 0.05 and p < 0.001, respectively. Most forms of nitrogen were interrelated with physicochemical parameters during different seasons, displaying nitrification and denitrification processes that occurred in the river rather than seasonal biological demand. Based on the nitrogen parameters, the 30 sampling sites were divided into three clusters, by which the pollution sources from chemical nitrogen fertilizers, animal wastes, domestic sewage, and industrial wastewater were identified. Generally, the Haicheng River basin provided about 700 tons of the annual TN flux, contributing to the eutrophication of the Liaodong Bay and Bohai Sea.     

新型填料曝气生物滤池去除氮化合物的效果

采用聚丙烯腈中空纤维膜段作为上流式曝气生物滤池的填料,就系统启动期间生物膜的形成以及对生活污水中氮化合物的去除规律进行了研究,并考察了稳定运行阶段的气水比、水力停留时间等对硝化和反硝化的影响.试验发现:在载体的外表面进行硝化反应的同时,其内部还发生了反硝化反应;中空纤维膜段的形状结构和表面特点使其适宜作为生物膜的载体.     

Effects of water sample preservation and storage on nitrogen and phosphorus determinations: implications for the use of automated sampling equipment

The effects of freezing, acidification, refrigeration and extended storage without refrigeration on measured concentrations of forms of nitrogen and phosphorus were assessed in water samples taken from polluted and unpolluted streams in dry and wet weather. Emphasis was placed on likely changes associated with the use of automatic samplers in field conditions. The response of measured nutrient concentrations to different preservation methods and to extended storage without preservation varied widely between samples. For polluted streams where nutrient concentrations were high (ammoniacal nitrogen >0.1 mg l⁻¹; oxidised nitrogen, total Kjeldahl nitrogen, total and filterable phosphorus >1 mg l⁻¹), there was generally little proportional change in nutrients other than ammoniacal nitrogen after up to 6 d of storage without preservation. Where nutrient concentrations were low, up to 90% of ammoniacal nitrogen, 50% of oxidised nitrogen, 84% of total Kjeldahl nitrogen and 67% of total phosphorus was lost after 6 d. If samples cannot be retrieved immediately, automatic samplers should be refrigerated where possible. Acidification is a suitable alternative for preservation of nitrogen. Samples for filterable phosphorus should be filtered as soon as possible after collection. In some circumstances, unpreserved samples may provide an acceptable level of accuracy for evaluation of broad temporal trends or estimation of nutrient loadings.     

全程硝化与短程硝化的特性对比研究

为了深入了解全程硝化和短程硝化的异同,采用SBR反应器研究了全程硝化和短程硝化的脱氮除磷特点。结果表明,在曝气量一定的情况下,短程硝化的DO上升速率大于全程硝化的,而全程硝化的氨氮降解速率大于短程硝化的。全程硝化过程中亚硝态氮的浓度始终较低,而短程硝化的亚硝态氮浓度则逐渐升高且增加速率保持稳定。全程硝化和短程硝化的硝态氮浓度都是从某一时间之后以恒定的速率增长。全程硝化过程中,亚硝态氮的积累率先短期升高之后逐步下降;在短程硝化中,亚硝态氮积累率逐渐上升,在好氧吸磷结束后亚硝态氮积累率保持稳定。     

Effect of some pesticides on nitrogen transformations in soil

It has been observed that the pesticides, phenmedipham and oxamyl, affect the mineralization of nitrogen in soil. Both mineralization and nitrification were sensitive to a number of other pesticides depending on the chemical and biological properties of a particular soil. Concentrations of even 0.5 times the regular field dose of phenmedipham or oxamyl inhibited nitrification in soil.Oxamyl decreased the rate of denitrification. In addition, both chemicals had a harmful effect on nitrogenase activity in soil as measured by the acetylene reduction technique.     

短程硝化-反硝化生物脱氮技术研究

对传统生物脱氮工艺原理和短程硝化—反硝化工艺原理进行了比较 ,分析了短程硝化 -反硝化技术的实用价值 ,提出了实现短程反硝化的控制条件。