Ammonium removal from digested sludge liquors using ion exchange

Liquors arising from the dewatering of digested sludge typically contain ammonium levels in the range 200-700mgl(-1) NH(4)(+)-N. These liquors are frequently recycled to the head of the wastewater treatment works (WwTW) untreated and can constitute >25% of the total nitrogen load entering the works at inlet. This paper investigates the use of a clay-based material, MesoLite, as an ion exchange medium for ammonium removal from recycle streams. Pilot-scale studies performed at Didcot WwTW, part of the Thames Water wastewater treatment network, indicate that MesoLite is highly selective for the ammonium ion. Results show that >95% of ammonium was removed from belt press liquors with an initial ammonium nitrogen concentration >600mgl(-1), with an overall ion exchange capacity >51g NH(4)(+)-Nkg(-1) medium and this resulted in an operating capacity in the range 27-36gNH(4)(+)-Nkg(-1).     

Side-Stream Treatment of Raw-Sludge Liquors using Activated Sludge: Pilot Investigations and Full-Scale Design Rationale

The end of sludge disposal at sea in 1998 will lead to increased volumes of sludge requiring treatment and disposal. Accordingly, there will be further quantities of high-strength liquors arising from sludge thickening and dewatering processes, and additional treatment capacity will therefore be required at treatment works.
This paper describes a three-year project to develop a dedicated side-stream treatment process for the treatment of raw-sludge liquors at Knostrop sewage-treatment works (Leeds) based on the activated-sludge process. Large pilot-scale trials are described which assisted in the construction of simple process design models for full-scale design. Together with additional pilot-scale aeration testing and modelling, a cost model for a full-scale plant was developed, allowing the lowest whole-life cost plant, based on 'net present cost'analysis, to be specified.     

25 years of the AMTREAT® process treating high‐strength ammonia liquors

Over the last 30 years, a number of biological treatment processes have emerged for treating high‐strength ammonia liquors arising from the dewatering of anaerobic digestate. The AMTREAT® process was the first process to become established and recognised as a viable and reliable process to treat these high‐strength ammonia liquors. The process is a high‐rate activated sludge plant supplied by ACWA Services Ltd. The first full‐scale plant was installed in 1995, treating centrate produced when dewatering anaerobically digested sludge. The process is a compact, high‐rate ammonia treatment system, which has a relatively small footprint compared to conventional activated sludge treatment processes. Originally designed to fully nitrify dewatering ammonia liquors by controlling the environmental conditions of the treatment reactor, the process has evolved first to include alkalinity recovery and subsequently to offer total nitrogen removal. This paper discusses the development of the AMTREAT® process from its initial development in 1992, to the modern day third generation plants which achieve typical achieve ammonia removal exceeding 99% and total nitrogen removal in excess of 80%.     

Design of Sewage-Treatment Plants in Brisbane, Australia

Brisbane City Council provides sewage-treatment facilities for a population of 800 000, together with industrial effluents having an organic loading equivalent to a further 600 000 people. Three projects are described to illustrate some of the different designs and operating parameters used in Brisbane, where the sewage temperatures range from 18°C to 29°C and stormwater is collected separately. The first project is a 400 000 population equivalent augmentation to a conventional activated-sludge plant located at Luggage Point. The two other plants have to comply, inter alia , with an effluent standard of 10 mg/l for total nitrogen. This requirement, together with site constraints and an economic evaluation of alternatives, resulted in the selection of the extended-aeration process incorporating anoxic zones and separate mixing and aeration. These contemporary designs are specific to Brisbane conditions, and are intended to facilitate reliable operation as well as being cost effective.     

Potential phosphorus recovery by struvite formation

Formation of struvite (MgNH4PO4 x 6H2O) at sewage treatment works can cause operational problems and decrease efficiency. Struvite has a commercial value and the controlled formation and recovery of it would be beneficial. A mass balance was conducted at full scale across the whole sewage treatment plant in order to identify a stream to conduct bench-scale struvite crystallisation studies. The most suitable stream was identified as the centrifuge liquors. The average flow of the liquor stream was 393 m3 d(-1) and the composition was as follows: 167 mg L(-1) phosphorus, 44 mg L(-1) magnesium, 615 mg L(-1) ammonium, 56 mg L(-1) calcium and 2580 mg L(-1) of alkalinity. The pH averaged at 7.6 and the stream had a predicted struvite precipitation potential of 140 mg L(-1). Struvite crystallisation occurred quickly during the trials, by raising the pH of the centrifuge liquors to 9.0 and dosing with magnesium. Up to 97% phosphorus removal as struvite was achieved. Struvite formation occurred when the molar ratio of magnesium:phosphorus was at least 1.05:1. Below this ratio phosphorus removals of 72% were observed, but not exclusively as struvite. Annual yields of struvite were calculated to be 42-100 tonnes a year, depending on the dose regime. Revenue from the sale of produced struvite could be between Pound Sterling8400 and Pound Sterling20,000 a year.     

新型双泥生物反硝化除磷脱氮工艺

在对生物脱氮与除磷机理进行深入研究后发现，生物脱氮与除磷是两个相对独立而又相互交叉的生理过程，其交叉点是部分聚磷菌在缺氧状态下的反硝化吸磷脱氮。在此基础上提出的新型双泥生物反硝化除磷脱氮工艺（由两个不同功能的SBR反应器组成）成功地解决了硝化菌与聚磷菌的泥龄之争。反硝化与聚磷菌厌氧释磷的矛盾等难题，该工艺运行稳定且处理效果良好，特别适合于处理BOD5/TP值低的污水。     

Optimization of a full‐scale site to achieve total nitrogen removal through implementation of a denitrification‐submerged anoxic filter

A full‐scale wastewater treatment plant with a 5500 population equivalent was retrofitted with a pre‐denitrification‐submerged anoxic filter (SAnoF) in order to achieve new total nitrogen (TN) consent of 35 mg/L. A 36 m³ SAnoF was installed downstream the primary settling tanks. The optimal operation of the anoxic SAnoF was investigated by varying the recirculation ratio, the carbon‐to‐nitrate ratio, and the hydraulic retention time. After stable operation was achieved, nitrate was removed by 80% at a loading of 0.5 kg NO₃/m³ day and a retention time of 60 min. The SAnoF presented a number of advantages, including the use of internal carbon for denitrification, decrease of carbon load to the trickling filter by 30%, and production of alkalinity required for nitrification in the trickling filter (11 mg CaCO₃/mg NH₄ removed). Overall, the SAnoF was satisfactory and the effluent TN concentration reached 20–25 mg TN/L.     

The Use of High-Rate Nitrification for the Pretreatment of Ammoniacal Digested Sludge Liquors

Anaerobic sludge digestion reduces most of the organic nitrogen in raw sludge to ammonia. Where the digested sludge is dewatered, the ammonia in the liquors can represent up to 25% of the total ammonia load on the receiving wastewater-treatment plant. This can cause problems with compliance and also limit the throughput of the digestion plant. The paper describes how Anglian Water addressed this problem at Cliff Quay wastewater-treatment plant, Ipswich by installing the Amtreat^TM high-rate nitrifying process. The reasons for the necessity to reduce the ammonia load to the plant are presented and the rationale behind the selection of this solution is outlined. The Amtreat^TM plant is described and its performance is evaluated. The Cliff Quay site is the first application of this process to a municipal wastewater-treatment plant in the UK, although there are several installations operating with industrial effluents.     

优化分段进水生物脱氮工艺设计参数

结合实际处理工艺，采用模型探讨了分段进水生物脱氮工艺设计中需考虑的参数(如进水流量分配、回流污泥量、溶解氧控制、碳源和碱度的投加)对脱氮效果的影响。     

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.     

人防工程结构设计中的等价等效静载法

人防工程设计时采用等效静载形式,由于动、静荷载计算特征性质不同,相互之间难于直观的比较,从而给设计及研究工作带来很多不便。等价等效静载是将有关动我特征内容(如构件强度设计安全系数不同,材料强度提高系数等)全部反应到拟研究的等价等效静载的数值内,从而可直接应用钢筋混凝土结构设计规范(TJ10-74)及有关图表进行人防结构设计而不必再考虑动载特征之影响。可使民用结构设计人员也能准确的完成上述两规范要求的防护工程设计。     

Energy saving in activated sludge plants by the use of more efficient fine bubble diffusers

Many activated sludge plants (ASP) use fine bubble diffused air as their source of oxygen. Blowers are attached to air pipework, which distributes air to a network of diffusers installed on the floor of the ASP tank. Modern diffusers are made from a rubber membrane which flexes to allow fine bubbles of air to pass through holes in the diffusers which then pass into the mixed liquors in the tank. The diffusers come as circular discs, tubes and more recently mats or panels. Yorkshire Water is in the process of building new ASP at some of their biggest sewage treatment works to meet new final effluent consent standards associated with the freshwater fisheries directive (FFD). These new works will treat sewage from a combined population of over two million people in the Yorkshire area. Black & Veatch is involved in some of the first works to have a new type of fine bubble diffuser installed in the ASP basins. These diffusers resemble a mat or panel and are fixed to the floor of the tank as opposed to circular and tubular diffusers which as fixed above the floor. Oxygen transfer testing has been carried out to show the efficiency of these aeration systems, which may offer significant savings in operating costs to water operators. This paper examines the results from the tests and compares them with other tests carried out in the United States and tests that have been carried out on other types of diffusers. The paper will discuss the results of the oxygen transfer tests and present capital and net present costs (NPC) for various diffuser installations.     

2020s scenario analysis of nutrient load in the Mekong River Basin using a distributed hydrological model

A distributed hydrological model, YHyM, was integrated with the export coefficient concept and applied to simulate the nutrient load in the Mekong River Basin. In the validation period (1992–1999), Nash–Sutcliffe efficiency was 76.4% for discharge, 65.9% for total nitrogen, and 45.3% for total phosphorus at Khong Chiam. Using the model, scenario analysis was then performed for the 2020s taking into account major anthropogenic factors: climate change, population, land cover, fertilizer use, and industrial waste water. The results show that the load at Kompong Cham in 2020s is 6.3 × 10⁴ tN a^− 1 (+ 13.0% compared to 1990s) and 4.3 × 10³ tP a^− 1 (+ 24.7%). Overall, the noticeable nutrient sources are cropland in the middle region and urban load in the lower region. The installation of waste water treatment plants in urban areas possibly cut 60.6%N and 19.9%P of the estimated increase in the case without any treatment.     

The influence of heat treatment on the metallic and polycyclic aromatic hydrocarbon content of sewage sludge

Heat treatment followed by vacuum filtration or filter pressing is one method of dewatering sewage sludge. The concentrations of certain heavy metals and polynuclear aromatic hydrocarbons in raw sewage sludge, treated sludge cake and the resultant liquors have been determined in samples collected from three sewage treatment works in the United Kingdom utilising heat treatment. Mass balances have been calculated using the results obtained and the degree of resolubilisation of these materials which occurs during the treatment process has been determined.     

污水脱氮除磷处理中的化学药剂投加

污水处理厂脱氮除磷处理中,在各个工艺环节需要投加化学药剂。着重介绍了反硝化的碳源、生物除磷中挥发性脂肪酸、碱度、化学除磷药剂中的各种药剂投加方法的基本原理、投加量计算、操作要求以及投加量的控制。     

4. Pollution Risks and Countermeasures for Surface Water Intakes

T he risks and severity of pollution events affecting surface waters have to be assessed from an inventory of pollution threats in each catchment, from regional and national statistics on pollution incidents, and from measurements on the travel and dispersal of pollutants in water courses. Inspection of factory premises, farms, and sewage treatment works commonly reveals ways of stopping potential sources of pollution. Other countermeasures include: bunding of chemical stores and handling areas; processing waste liquors on site; promptly notifying tanker accidents and other spills; broad band monitoring of river water quality; control of intake, buffer storage and water treatment, in light of pollution arrival and chemical data.     

利用储碳活性污泥强化反硝化脱氮研究

为提高脱氮效果,在SBR进水的缺氧操作结束后取出部分储碳污泥并加以保存,待好氧末返投储碳污泥作为碳源来强化缺氧反硝化反应.结果表明:对TN的去除率可达98%左右,远高于以缺氧/好氧方式运行的SBR;在好氧段的污泥浓度约为3 000 mg/L的情况下,选择缺氧搅拌段的污泥浓度为5 000 mg/L左右能使TN基本全部被去除.SBR经改造后,能有效实现取、返储碳污泥,提高了脱氮效果.     

粉末炭/SBR工艺处理高浓豆制品废水研究

对粉末炭(PAC)/SBR工艺处理高浓度豆制品生产废水进行了研究,探讨了PAC用量、曝气时间、曝气方式对处理效果的影响.结果表明:在PAC用量为400 mg/L、PAC/SBR反应器进水COD负荷<6 000 mg/L及限制曝气时间为6h时,最终出水的COD和NH 4-N浓度均能达标.COD由2850 mg/L降至611mg/L时,反应符合零级反应动力学规律;COD<611 mg/L时,反应符合一级反应动力学规律.     

城镇污水处理厂尾水中氮磷形态及光谱特征分析

为了进一步探究污水厂尾水排放对受纳水体的潜在影响,选取巢湖流域采用3种典型处理工艺(氧化沟、SBR、A²/O工艺)的7座污水厂为研究对象,分析了尾水中氮、磷的形态及水体中溶解性有机质(DOM)的光谱特征。结果表明,不同工艺对TN、TP、COD等指标均具有很好的去除效果且无明显差异。尾水中颗粒态总氮(PN)占比在13.4%以下,主要以溶解态总氮(DTN)形式存在,其中溶解态无机氮(DIN)占比高于溶解态有机氮(DON)。尾水中颗粒态总磷(PP)占比在10.1%~66.7%,磷主要以溶解态总磷(DTP)形式存在,其中溶解态无机磷(DIP)占比在60%以上。DOM的三维荧光光谱显示,不同工艺尾水中的DOM均具有4类荧光特征峰,其中腐殖酸类物质C峰与紫外区类富里酸物质A峰较为明显。根据DOM的荧光特性参数(HIX值<4、FI值>1.9、BIX值>1.0),各污水厂出水中的DOM主要为自生来源。由此表明,污水处理厂削减了大量的入河碳、氮、磷等负荷,其尾水可用于城市河道生态补水水源,实现城市污水资源再生利用。     

Floodplain nutrient and sediment dynamics on the Kent Stour

Floodplain land use is currently of concern. Agri‐environmental policy favours grass over arable agriculture, while urban development is deemed unsuitable. The role of meadowland requires evaluation because it exhibits a potential to deliver environmental goods beyond flood detention and habitat creation; it has the potential to take up particular elements and trap sediment. This is particularly important where there is eutrophication of water from agriculture and wastewater and also physical degradation of the channel and floodplain. In this study, carbon (C), nitrogen and phosphorus (P) status and sediment deposition at typical locations on a southern English floodplain were investigated. It is concluded that C sequestration could be significant and there is sediment trapping during times of flood but further P accumulation in the topsoil of grazing land is limited. It is concluded that nutrient loading of the river from sewage effluent and from agriculture is best prevented at source.