The Options Available for Ammonia Removal at Davyhulme Sewage-Treatment Works

Davyhulme sewage-treatment works, which serves the Manchester drainage area, is one of the lagest in the UK. The dry-weather flow is 300 000 m³/d, and the plant receives a wide range of industrial effluents. The works has been identified as a major source of pollution in the Mersey estuary, with an average discharge of 6500 kg ammonia/day. As part of its initiative to improve the Mersey estuary, North West Water intends to reduce the daily ammonia load from Davyhulme to about 1000 kg/d by 1995. In order to assess the capabilities of both conventional and novel processes to achieve this degree of ammonia removal, a number of on-site pilot plants were established. This paper reports on the pilot-plant studies and the selection of process options. Recommendations with regard to design parameters and final process selection are given.     

The Reconstruction of Sewage-Treatment Works in Osaka City

Osaka has nearly completed its sewerage system, and twelve sewage-treatment works are now in operation. Tsumori and Ebie works, the two oldest, were commissioned in 1940. For these works, full-scale reconstruction has just commenced.
This paper reports on the reconstruction of the Tsumori works, and outlines the plan for future reconstruction of the city's sewage-treatment works.     

Control and Stabilisation of Odorous Sludge from Fleetwood Sewage-Treatment Works

Following completion of the construction of Fleetwood sewage-treatment works in 1996, the sludge (from the plant) was causing health and safety problems for the workforce and there were complaints of odour from the local community. Problems arose due to overloading of the biological-treatment units, resulting in little or no dissolved oxygen in parts of the process. There was a need to stabilise the sludge in the short term, culminating in the need for chemical conditioning, and an investigation into operational procedures to stabilise the sludge in the long term. The sludge was successfully stabilised using ferric chloride and sodium hydroxide. The long-term stability of the sludge was further improved using operational changes (such as the inclusion of step feeding and by demonstrating the effect of load removal upstream from the existing biological process) via pilot-plant studies.     

The Use of Redox Potential to Control Ferric Sulphate Dosing during Phosphate Removal

In recent years, the Norfolk Broads have been enriched with sewage effluent and runoff from heavily fertilized land. Nitrogen and phosphorus compounds from these sources can cause ecological problems by stimulating increase in algal biomass in the water, so part of Anglian Water's programme of research in Broadland has been to remove phosphate from major sewage effluents discharged to the Rivers Ant and Bure. This is achieved by dosing ferric sulphate to secondary effluent and settling the resultant insoluble complex.
At three sites on the River Bure, the performance of timeclock- and redox-based dose control systems was evaluated. Redox control, by restricting dosing when phosphate load was low, increased the efficiency of phosphate removal and produced up to 19 per cent savings in chemical costs. Modifications are described which made the system self-regulating and ensured that savings were not eroded by maintenance costs. The system now operates efficiently and routinely at major sites on the Rivers Ant and Bure.     

厌氧下的PHB和聚磷酸盐及其生化机理研究

用氧化还原电位仪严格监测反应过程,准确测定了在厌氧状况下ＰＨＢ的合成量与聚酸盐的释放量;对活性污泥细胞内的ＰＨＢ颗粒和聚磷粒进行了大量染色及显微镜检验分析。通过试验证明,厌氧状况发生了ＰＨＢ大量合成与聚磷酸盐大量释放,并得出二者关系曲线图,对其生化机理进行了深入研究。     

某城市污水处理厂改造工程的中试研究

采用厌氧塘/预曝气/絮凝沉淀/好氧生化工艺对工业废水所占比例较高的城市污水进行中试研究.结果表明,厌氧塘出水经30 min的预曝气后进行絮凝沉淀,当FeSO4投加量为150mg/L、聚合氯化铝(PAC)投加量为100 mg/L时,对COD的单元去除率能够达到52%,且BOD5/COD值由0.4提高到0.6;对好氧系统采用周期性改变反应池内溶解氧浓度和外加碳源的措施,能够提高生物脱氮效果;经该工艺处理后,出水水质能够达到GB 18918-2002标准的一级B标准;经核算,该工艺的直接运行成本为0.65元/m3(不合污泥处理费).     

Effect of soluble microbial products on microbial metabolisms related to nutrient removal

In this study, the effect of soluble microbial products (SMP) on the metabolisms related to phosphate or nitrogen removal of activated sludge was investigated. Two anaerobic-aerobic activated sludge processes were operated, one with a hydraulic retention time (HRT) of 48 h (RunL) and the other 6.4 h (RunS). The longer HRT of RunL was intended to promote the accumulation of SMPs in the supernatant. With the sludge from RunS and the supernatant from both of the runs, supernatant exchange batch experiments (SEBEs) were conducted, in which the acetate uptake rate and phosphate release rates under anaerobic conditions and the phosphate uptake rate under aerobic conditions were measured as these metabolisms are related to enhanced biological phosphorus removal. The nitrification rate was also measured. The statistical analyses of the results from the SEBEs showed that the supernatant from RunL had an inhibitory effect on the anaerobic acetate uptake and nitrification of the sludge from RunS. The cause of which was attributed to SMPs in the supernatant from RunL. As a result, the inhibitory effect of SMPs on nitrification and anaerobic acetate uptake was confirmed.     

曝气生物滤池对印花废水的脱氮效果研究

采用曝气生物滤池(BAF)处理印花废水,重点考察了水力停留时间(HRT)、C/N值、气水比对其脱氮效果的影响.结果表明:在HRT为4 h、C/N值为2、气水比为5:1的条件下,BAF可达到最佳脱氮效果,对TN、NH<,4><'+>-N的去除率分别达到50%、90%以上.     

AB法工艺的水处理功能及其局限性

系统分析了 AB法工艺的原理、特点及其在脱氮除磷方面的局限性 ,对 AB法在脱氮除磷功能方面的强化进行了讨论     

无锡市胡埭污水处理厂升级改造工艺设计

无锡市胡埭污水处理厂升级改造工程实施规模为0.7×104m3/d,采用强化C-TECH二级生物脱氮除磷以及增加三级盘片式微过滤工艺进行工艺改造,出水达到《城镇污水处理厂污染物排放标准》(GB 18918—2002)中的一级A标准。介绍了升级改造工程处理工艺选择、工程设计参数、设备配置情况等,总结分析了升级改造工艺设计的技术特点和要求。     

Modelling biological and chemically induced precipitation of calcium phosphate in enhanced biological phosphorus removal systems

The biologically induced precipitation processes can be important in wastewater treatment, in particular treating raw wastewater with high calcium concentration combined with Enhanced Biological Phosphorus Removal. Currently, there is little information and experience in modelling jointly biological and chemical processes. This paper presents a calcium phosphate precipitation model and its inclusion in the Activated Sludge Model No 2d (ASM2d). The proposed precipitation model considers that aqueous phase reactions quickly achieve the chemical equilibrium and that aqueous-solid change is kinetically governed. The model was calibrated using data from four experiments in a Sequencing Batch Reactor (SBR) operated for EBPR and finally validated with two experiments. The precipitation model proposed was able to reproduce the dynamics of amorphous calcium phosphate (ACP) formation and later crystallization to hydroxyapatite (HAP) under different scenarios. The model successfully characterised the EBPR performance of the SBR, including the biological, physical and chemical processes.     

Uptake and release of phosphate by a pure culture of Acinetobacter calcoaceticus

Uptake and release of phosphate by a pure culture of Acinetobacter calcoaceticus were investigated under aerobic and anaerobic conditions. The total phosphorus content of this bacterium varied from 0.3 to 1.7 mmol g⁻¹ dry cells or from 0.93 to 5.3% of dry cell weight under various culture conditions. The log-phase cells accumulated polyphosphates of 0.33−0.64 mmol P g⁻¹ dry cells. ³¹P NMR spectra suggested that a portion of polyphosphates was likely bonded to some sort of structural components of the cell. A. calcoaceticus release phosphate linearly with time when transferred from aerobic to anaerobic conditions. The release rate was in the range of 5.9–14.7 × 10⁻³ mmol P g⁻¹ dry cells h⁻¹ and about 4–8% of cellular phosphorus was released during the initial 6 h. During the process of phosphate release acetate was not taken up by this bacterium.     

Effect of anaerobic conditions on activated sludge filamentous bulking in laboratory systems

The effect of anaerobic conditions on the occurrence of filamentous microorganisms in the biocenosis of activated sludge has been studied in laboratory systems. These systems consisted of an anaerobic completely mixed tank followed by an oxic one. A single oxic completely mixed tank served as a control unit. Synthetic wastewater was used incorporating glucose and ethanol as a carbon source in order to support the growth of filamentous microorganisms in completely mixed tanks. It has been demonstrated that the growth of some filamentous organisms, for instance Type 021N and Sphaerotilus natans, was suppressed under anaerobic conditions as a result of lower rates of polyphosphate depolymerization under anaerobic conditions. However, the positive effect of the anaerobiosis may be eliminated if simultaneous dissimilatory sulphate reduction occurs. In this case filamentous bulking caused by presence of such microorganisms like Thiothrix is possible.     

兖州市污水处理厂改扩建工程设计

针对兖州市污水处理厂改扩建工程存在的出水水质标准提高、工程规模扩大以及工程可利用面积受限等问题,对污水厂原AB工艺进行了改造:超越原有A段曝气池,将中间沉淀池改造为初沉池;将原B段曝气池改造为A2/O工艺的好氧段,并新建厌、缺氧池,使之成为A2/O工艺。在对原B段曝气池的改造中,采用投加生物填料的HYBASTM工艺(填充率为41.7%)。工程完成后一年的出水水质监测结果表明,出水N、P能够稳定达到《城镇污水处理厂污染物排放标准》(GB 18918—2002)的一级B标准。     

The trophic potential of sewage effluent resulting from various levels of treatment

On Italy's Adriatic coast there are a large number of aerobic sewage treatment plants, the majority of which do not feature high-efficiency tertiary treatment processes. In order to investigate the relationship between these plants and the trophic potential of the water they discharge, we constructed a pilot plant capable of reproducing the sewage treatment process with four different levels of purification on a rising scale of efficiency in terms of the best-known macronutrients (nitrogen and phosphorus). Water samples taken at various points on the plant for each of the four operating modes underwent laboratory assessment to establish their trophic potential in relation to a dinoflagellate alga (Prorocentum micans). We were thus able to demonstrate that after biological treatment alone the sewage water has a high eutrophication effect; this gradually decreases as the nutrients are removed and virtually disappears when the plant is providing maximum removal at full efficiency.     

Cadmium solubility in paddy soils: effects of soil oxidation, metal sulfides and competitive ions

Cadmium (Cd) is a non-essential element for human nutrition and is an agricultural soil contaminant. Cadmium solubility in paddy soils affects Cd accumulation in the grain of rice. This is a human health risk, exacerbated by the fact that rice grains are deficient in iron (Fe) and zinc (Zn) for human nutrition. To find ways of limiting this potential risk, we investigated factors influencing Cd solubility relative to Fe and Zn during pre-harvest drainage of paddy soils, in which soil oxidation is accompanied by the grain-filling stage of rice growth. This was simulated in temperature-controlled “reaction cell” experiments by first excluding oxygen to incubate soil suspensions anaerobically, then inducing aerobic conditions. In treatments without sulfur addition, the ratios of Cd:Fe and Cd:Zn in solution increased during the aerobic phase while Cd concentrations were unaffected and the Fe and Zn concentrations decreased. However, in treatments with added sulfur (as sulfate), up to 34 % of sulfur (S) was precipitated as sulfide minerals during the anaerobic phase and the Cd:Fe and Cd:Zn ratios in solution during the aerobic phase were lower than for treatments without S addition. When S was added, Cd solubility decreased whereas Fe and Zn were unaffected. When soil was spiked with Zn the Cd:Zn ratio was lower in solution during the aerobic phase, due to higher Zn concentrations. Decreased Cd:Fe and Cd:Zn ratios during the grain filling stage could potentially limit Cd enrichment in paddy rice grain due to competitive ion effects for root uptake.