Factors affecting measurement of specific methanogenic activity.

Specific methane production (SMP) tests have been used to determine the potential loading rate capacity of anaerobic reactors, to characterize biomass prior to its use as an inoculum for new anaerobic reactors, to detect changes in biomass activity during operation, or to assess the occurrence of toxic conditions. SMP tests also provide a basis for estimating specific methanogenic activity in mixed anaerobic cultures. SMP protocols used to date have varied widely in both procedure and objective. Tests conducted by the present authors indicated that biomass concentration, substrate type and concentration, and mixing intensity are factors that can affect the results of SMP tests.     

自循环曝气厌氧膜生物反应器培养厌氧氨氧化菌的研究

利用浸没式厌氧膜生物反应器(SAnMBR)对Anammox细菌进行富集培养,同时利用Anammox反应产生的氮气对膜组件进行自循环吹扫,有效地缓解膜污染,实现SAnMBR与Anammox工艺的有机结合。选用絮状污泥为接种泥,反应器成功运行了69 d。在此过程中,最大氮负荷为1.8 kg/m3·d,总氮去除率整体维持在83%,增加曝气量对Anammox菌的活性和颗粒粒径无明显影响。除此之外,应用循环曝气系统对膜表面进行在线冲刷,相比无曝气条件,保持曝气量为0.2 m3/h时,膜使用周期由4 d延长到38 d。选用Lawrence-McCarty模型研究Anammox菌的生长动力学特性,得真实产率(YT为0.17 mg/mg,衰减系数(Kd)为0.01 d-1,Anammox菌增长速度快。相比其他反应器(如SBR、UASB),MBR具有更好的富集效果。     

A one-stage system with partial nitritation and anammox processes in the moving-bed biofilm reactor.

The ability of bacterial cultures to create biofilm brings a possibility to enhance biological wastewater treatment efficiency. Moreover, the ability of Anammox and Nitrosomonas species to grow within the same biofilm layer enabled a one-stage system for nitrogen removal to be designed. Such a system, with Kaldnes rings as carriers for biofilm growth, was tested in a technical pilot plant scale (2.1 m(3)) at the Himmerfj?rden Waste Water Treatment Plant (WWTP) in the Stockholm region. The system was directly supplied with supernatant originating from dewatering of digested sludge containing high ammonium concentrations. Nearly 1-year of operational data showed that during the partial nitritation/Anammox process, alkalinity was utilised parallel to ammonium removal. The process resulted in a small pH drop, and its relationship with conductivity was found. The nitrogen removal rate for the whole period oscillated around 1.5g N m(-2)d(-1) with a maximum value equal to 1.9 g N m(-2)d(-1). Parallel to the pilot plant experiment, a series of batch tests were run to investigate the influence on removal rates of different dissolved oxygen conditions and addition of nitrite. The highest nitrogen removal rate (5.2g N m(-2)2d(-1)) in batch tests was obtained when the Anammox process was stimulated by the addition of nitrite. In the simultaneous partial nitritation and Anammox process, the partial nitritation was the rate-limiting step.     

Microbial community of anammox bacteria immobilized in polyethylene glycol gel carrier

Anaerobic ammonium oxidation (anammox) is a recently discovered microbial pathway in the biological nitrogen cycle and a new cost-effective way to remove ammonium from wastewater. We have so far developed new immobilization technique that anammox bacteria entrapped in polyethylene glycol (PEG) gel carrier. However, fate and behavior of anammox bacteria in a gel carrier is not well understood. In the present study, we focused on the population changes of anammox bacteria in a gel carrier. Three specific primer sets were designed for real-time PCR. For quantification of anammox bacteria in a gel carrier, real-time PCR was performed. The anammox bacteria related to HPT-WU-N03 clone were increased the rate in anammox population, and found to be a major population of anammox bacteria in a gel carrier. Furthermore, from the results of nitrogen removal performance and quantification of anammox bacteria, the correlation coefficient between copy numbers of anammox bacteria and nitrogen conversion rate was calculated as 0.947 in total anammox population. This is the first report that population changes of anammox bacteria immobilized in a gel carrier were evaluated.     

Engineering aspects of a mixed methanotrophic culture in a membrane-aerated biofilm reactor.

Methanotrophic biodegradation using the membrane-aerated biofilm reactor (MABR) is a technology offering several advantages over both conventional biofilm reactors and suspended-cell processes. In this study the oxidation efficiency of a methanotrophic biofilm in a 1.5 litre MABR was investigated. Measurements of oxygen and methane uptake rates together with biofilm thickness were taken for developing biofilms. It was found that the specific rate of metabolic activity of the biofilm was unusually high as determined by the methane and oxygen uptake rates. Microbial activity stratification was evident and the location of stratified layers of oxygen consuming components of the consortium could be manipulated via the intra-membrane oxygen pressure.     

On-line estimation of the dissolved zinc concentration during ZnS precipitation in a continuous stirred tank reactor (CSTR).

In this paper a method is presented to estimate the reaction term of zinc sulphide precipitation and the zinc concentration in a CSTR, using the read-out signal of a sulphide selective electrode. The reaction between zinc and sulphide is described by a non-linear model and therefore classical observer theory cannot be applied directly, as this theory was initially developed for linear systems. However, by linear reparametrization of this non-linear system, the linear observer theory can be applied in an effective way. This is illustrated by a zinc sulphide example using real data.     

影响黏性土表面干缩裂缝结构形态的因素及定量分析

本文在室内试验的基础上,采用计算机图片处理技术,在对不同黏土厚度、干湿循环次数和土质成分等条件下黏性土干缩裂缝网络进行对比和定量分析的基础上,探讨了聚丙烯纤维对黏性土干缩裂缝的抑制作用和机理。结果表明,土层厚度、干湿循环次数和土质成分对裂缝网络的节点个数、裂缝条数、裂缝长度和宽度、块区个数、块区面积、裂缝率和裂缝网络的分形维数等定量参数均有一定的影响;裂缝网络的节点个数、块区个数和裂缝率是描述其形态结构和几何特征的基本指标;在黏性土中加入适量的聚丙烯纤维能够改变干缩裂缝的发展规律,降低土体的裂隙率,提高土体结构物的稳定性和防渗性能。     

Treatment of nitrogen-rich wastewater using partial nitrification and anammox in the CANON process.

Partial nitrification combined with Anammox in a single reactor (the CANON process) is an energy-efficient N-removal technology that could substantially lower the N-load of a WWTP by separate treatment of nitrogen-rich side streams, preventing the need for extensive expansion and reducing the total energy requirement. This study looks at the enrichment of Anammox from activated sludge and its application in the CANON process on lab-scale. The aim was to identify the critical process control parameters necessary for successful operation of CANON. An Anammox culture capable of removing 0.6 kg N/m3/d was enriched in 14 weeks in a sequencing batch reactor. Nitrifying biomass was inoculated into the Anammox reactor (10% v/v) together with limited oxygen supply (< 8 mL/min) to initiate the CANON process in continuous culture. The small flocs formed by the biomass (< 1000 microm) were sensitive to low O2 concentrations (< 0.1 mg/L) which prevented simultaneous nitrification and Anammox. Operation with 20 min aerobiosis and 30 min anaerobiosis was necessary to achieve sustained, completely autotrophic N-removal for an extended period at a rate of 0.08 kg N/m3/d. Essential process control parameters for stable CANON operation were the nitrite concentration, oxygen concentration, pH and the temperature.     

Monitoring of pH inhibition on microbial activity in a continuous flow reactor by pseudo toxic concentration (C(PT)) concept and time delay model.

The pseudo toxic concentration (C(PT)) concept was introduced as a quantification method to describe pH as an inhibitor concentration. In this research, the applicability of the C(PT) concept model for the detection of pH inhibitions was expanded for a continuous flow activated sludge reactor. A pilot equipped with an inhibition detection system was installed. Inhibitory wastewater was injected for 1 h and the relative activity was calculated by the maximum respiration rate. At the same time, the coefficients for the C(PT) concept model were estimated. At the dynamic conditions, the estimated relative activity by the C(PT) concept model showed time lag compared to the measured one. However, the time lag problem was successfully resolved by introducing a transfer function into the C(PT) concept model. The C(PT) concept model combined with a transfer function (C(PT) + TF model) successfully tracked the variation of the relative activity under dynamic conditions. The C(PT) + TF model could detect 50% inhibition faster than the respirometry based method by approximately 10 min. Moreover, it had additional advantages such as being inexpensive, easy to install and simple to operate. In conclusion, the C(PT) + TF model was an effective and convenient detection method of pH inhibition.     

Solar disinfection for the post-treatment of greywater by means of a continuous flow reactor

SODIS (solar disinfection) is a low-cost alternative for water decontamination. The method is based on the exposure of water, contained in PET bottles, to direct sunlight, and mainly its UV-A and infrared components. The present research studied SODIS as a low cost alternative for the inactivation of Escherichia coli (E. coli) in treated greywater, aiming at its reuse for more noble applications. Experiments were performed in (i) batch mode (2 L PET-bottles), testing the effect of turbidity on system efficiency and, (ii) in a continuous pilot-scale reactor prototype (51 L, using interconnected 2 L-PET bottles), testing hydraulic retention times (HRT) of 18 and 24 h. Samples were exposed to an average solar radiation intensity of 518 W/m2. The results obtained indicate that the SODIS system has potential for total coliforms and E. coli inactivation in the pre-treated greywater, reaching 2.1 log units E. coli inactivation in batch experiments for low turbidity samples (21 NTU), and > 2 log units inactivation of total coliforms (and E. coli, when present) for the 24 h HRT-continuous prototype. The continuous flow prototype needs more testing and structural improvements to cope with the difficulties posed by algae growth, as they complicate maintaining conditions of constant flow and make frequent maintenance inevitable.     

SBBR自养型短程硝化的实现及其影响因素研究

采用序批式生物膜反应器(SBBR)以及模拟无碳源的理想生活污水,对系统内各参数进行反复调试,在一个月内实现了自养型短程硝化系统的启动,氨氮去除率为98%,亚硝态氮积累率为95.29%。当温度控制在20～35℃时都会实现短程硝化,而30℃时短程硝化的效果最佳;系统其他条件不变的情况下DO为1.5 mg/L时,短程硝化的效果最好;系统具有一定的承受有机负荷的能力,在进水中外加COD_(Cr)浓度不超过75 mg/L时,不会对系统产生影响且COD_(Cr)的去除率为50%。     

影响反硝化除磷与厌氧氨氧化耦合的因素

氧对厌氧氨氧化菌有毒,但在颗粒污泥和生物膜中的厌氧氨氧化菌对氧有较高的耐受能力,并且聚磷菌能消耗影响氧氨氧化菌生长的氧。厌氧氨氧化菌的生长无需有机物的参与,聚磷菌释磷需要吸收有机物,少量有机物的加入对厌氧氨氧化菌的活性影响不大。亚硝酸盐是厌氧氨氧化菌氧化氨的电子受体,较高浓度的亚硝酸盐对反硝化聚磷有抑制作用,但合适浓度的亚硝酸盐(该浓度可以通过驯化来提高)可以作为反硝化聚磷菌吸磷的电子受体。厌氧氨氧化过程中有硝酸盐生成,反硝化聚磷菌能利用这部分硝酸盐。另外,两类菌都适宜于中温略偏碱性的环境。因此,通过创造同时对厌氧氨氧化菌和反硝化聚磷菌有利的微生态环境,发挥两者在脱氮除磷方面的协同耦合作用,达到高度脱氮除磷,是极有前景的废水厌氧(缺氧)处理研究方向。     

Assessment of biological activity during temperature changes in a bench-scale sequencing batch reactor fed with synthetic medium containing lignin

The influence of temperature on activated sludge in a bench-scale SBR fed with a synthetic medium simulating paper mill effluents was determined using biological methods based on the measurement of enzymatic activities. Redox activity inside cells and in the extracellular polymeric substances as well as the proportion of active cells in the sludge were measured by the reduction of the tetrazolium salts XTT and CTC, respectively. A significant shift in the size distribution of lignin at 30°C correlated with a maximum of extracellular redox activity. The percentage of active cells in the biocoenosis was independent of temperature. α-glucosidase and L-alanine-aminopeptidase activities were steady at 20, 30 and 40°C. After shifting the temperature to 50°C there was an enormous short-time increase of both enzyme activities because of the change from mesophilic to thermophilic conditions. Of the biological parameters tested, only extracellular redox activity correlated with degradative activity as detected by a change in molecular size distribution of lignin molecules.     

Factors affecting the longevity of sub-surface horizontal flow systems operating as tertiary treatment for sewage effluent.

Compared with other forms of domestic wastewater treatment, reed beds require very little in the way of operational and maintenance input. This is even more markedly the case with tertiary treatment systems (than with secondary treatment systems) where the necessary maintenance amounts to only a few days/year. Unfortunately, in practice this frequently results in them receiving little or no attention at all. Tertiary treatment reed beds are not a "fit and forget" solution but they are often treated this way because they are very forgiving and abuse-tolerant. After a number of years a few of these tertiary reed beds have deteriorated to an extent whereby they are close to failing to comply with the regulator's requirements. Severn Trent Water Ltd has recognised this situation and has committed a budget for a programme of reed bed maintenance. This work has started with a survey of the condition of their beds and particularly to determine the common problems and hence the maintenance regime required. Five main problems occurred either singly or in combination namely: (a) sludge deposition; (b) above surface flooding (partially caused by (a), (c), and (d)); (c) inlet flow distributor problems/clogging; (d) outlet collector problems/incorrect level; (e) weed infestation.     

Microbiological studies of an anaerobic baffled reactor: microbial community characterisation and deactivation of health-related indicator bacteria.

This WRC funded project has studied the appropriateness of the ABR (anaerobic baffled reactor) for on-site primary sanitation in low-income communities. A 3,000 L pilot reactor was located at the Kingsburgh wastewater treatment plant south of Durban, South Africa. Feed to the reactor was raw domestic wastewater containing a significant proportion of particulate organic matter. The compartments of the ABR were routinely monitored for pH, COD, and gas production, among other physical-chemical determinants. The microbial population in each compartment was analysed by fluorescent in situ hybridisation, using general oligonucleotide probes for eubacteria and archeae and a suite of 10 genera or family specific probes. Scanning electron microscopy was conducted on the sludge fraction of each compartment. Mixed fractions from each compartment were also analysed for health-related indicator bacteria (total coliforms and E. coli). Results indicated that methanogenesis was not occurring to the expected extent in the latter compartments, and that this was probably due to a hydraulic load limitation. This contrasted with earlier studies on industrial effluent, for which the organic load was exclusively in soluble form. Inactivation of health-related indicator bacteria was less than 1 log, indicating the need for an additional post-treatment of the effluent to protect community health.     

Photocatalytic oxidation of low concentration 2,4-D solution with new TiO2 fiber catalyst in a continuous flow reactor.

Environmental pollution by low concentrations of 2,4-Dichlorophenoxyacetic acid (2,4-D) is a concern these days due to ever increasingly stringent regulations. Photocatalysis with immobilized TiO2 fiber is a promising oxidation method. Laboratory experiments on photocatalytic degradation of 0.045 mmol l(-1) 2,4-D with the world's first high-strength TiO2 fiber catalyst were carried out in a continuous flow reactor in which the degradations were, in general, similar to those with high 2,4-D concentrations investigated elsewhere. Degradation and mineralization of 2,4-D were significantly enhanced with no initial pH adjustments. The rate constants for total organic carbon (TOC) without pH adjustment were about two-fold bigger than the pH adjustment cases. CO2 gas measurement and carbon mass-balance were carried out for the first time, where about 34% organic carbon converted into CO2 gas during four-hour oxidation. 2,4-Dichlorophenol (2,4-DCP), phenol, benzyl alcohol and two unknowns (RT = 2.65 and 3.78 min.) were detected as aromatic intermediates while Phenol was the new aromatic in HPLC analysis. Dechlorination efficiencies were high (> 70%) in all the cases, and more than 90% efficiencies were observed in chloride mass balance. Bigger flow rates and solution temperature fixed at 20 degrees C without pH adjustment greatly enhanced 2,4-D mineralization. These results can be an important basis in applying the treatment method for dioxin-contaminated water and wastewater.     

Start up of an anaerobic inverse turbulent bed reactor fed with wine distillery wastewater using pre-colonised bioparticles.

The long start-up period of fluidized bed biofilm reactors is a serious obstacle for their wide installation in the anaerobic treatment of industrial wastewater. This paper presents the results of an anaerobic inverse turbulent bioreactor treating distillery wastewater during 117 days of operation at a laboratory scale. The pre-colonized bioparticles for this work were obtained from a similar reactor processing the same wastewater and which had a start-up period of 3 months. The system attained carbon removal efficiency rates between 70 and 92%, at an organic loading rate of 30.6 kg m(-3) d(-1) (chemical oxygen demand) with a hydraulic retention time of 11.1 h. The results obtained showed that the start-up period of this kind of reactors can be reduced by 3 using pre-colonized bioparticles.     

Quantification of ammonia-oxidizing bacteria populations in full-scale sewage activated sludge systems and assessment of system variables affecting their performance.

This study carried out quantification of ammonia-oxidizing bacteria (AOB) populations in 12 full-scale sewage activated sludge systems that were different in ammonia removals and treatment processes during three different seasons. Experiment was divided into 3 parts: 1) analysis of AOB communities by PCR-DGGE-cloning-sequencing of 16S rRNA genes; 2) development of four real-time PCR primer sets for quantification of the particular AOB of interest; and 3) quantification of AOB populations by using the newly developed real-time PCR primer sets. The results suggested that all the primer sets gave good reproducibility and specificity for PCR amplification with the detection limits of 10(2) copies/PCR reaction. Although the 12 systems were different in several aspects, one of the identified sequence types of Nitrosomonas oligotropha cluster was the dominant AOB in every system and every season studied. However, the other sequence type of this cluster was not significantly involved in ammonia removals in the systems. The occurrence of N. communis cluster in the systems seemed to depend on the remaining oxygen concentrations in the sludge floc and thus the activity of aerobic heterotrophs in the aeration tanks. N. europaea-Nitrosococcus. mobilis solely existed in one A20 system of which the influent contained twice the chloride concentrations than those of other systems.     

Denitrification with epsilon-caprolactam by acclimated mixed culture and by pure culture of bacteria isolated from polyacrylonitrile fibre manufactured wastewater treatment system.

The aim of this study is to isolate denitrifying bacteria utilizing epsilon-caprolactam as the substrate, from a polyacrylonitrile fibre manufactured wastewater treatment system. The aim is also to compare the performance of PAN (polyacrylonitrile) mixed bacteria cultures acclimated to epsilon-caprolactam and isolated pure strain for treating different initial epsilon-caprolactam concentrations from synthetic wastewater under anoxic conditions. The result showed that the PAN mixed bacteria cultures acclimated to epsilon-caprolactam could utilize 1538.5 mg/l of epsilon-caprolactam as a substrate for denitrification. Sufficient time and about 2200 mg/l of nitrate were necessary for the complete epsilon-caprolactam removal. Paracoccus thiophilus was isolated from the polyacrylonitrile fibre manufactured wastewater treatment system and it could utilize 1722.5 mg/l of epsilon-caprolactam as a substrate for denitrification. About 3500 mg/l of nitrate was necessary for the complete removal of epsilon-caprolactam. When the initial epsilon-caprolactam concentration was below 784.3 mg/l, the removal efficiency of epsilon-caprolactam by Paracoccus thiophilus was better than that for the PAN mixed bacteria cultures. The growth of Paracoccus thiophilus was better. However, when the initial epsilon-caprolactam concentration was as high as 1445.8 mg/l, both the epsilon-caprolactam removal efficiency by Paracoccus thiophilus and Paracoccus thiophilus specific growth rate were similar to the PAN mixed bacteria cultures.