Monitoring Biofilm Thickness Using A Non-Destructive, On-Line, Electrical Capacitance Technique

Abstact The present study was designed to evaluate indirect, non-invasive, on-line measurement of biofilm thickness using an electrical capacitance technique. Several assays were carried out and the results showed that, at a frequency of 1 kHz, electrical capacitance could be used to measure biofilm thickness indirectly (with a correlation coefficient of 0.9495). The reproducibility revealed by the assays was also highly satisfactory.However, in contrast to what was expected, there was an inverse relationship between electrical capacitance and biofilm thickness, i.e. electrical capacitance diminished with the increase in the biofilm thickness.The tests were also carried out at different frequencies (1 kHz, 10 kHz and 100 kHz)     

Monitoring the impact of dissolved oxygen and nitrite on anoxic biofilm in continuous denitrification process

An anoxic biofilm involved in continuous denitrificationprocess was monitored to investigate the effect of differentconcentrations of influent dissolved oxygen (DO) or nitrite onthe biofilm. Microelectrode measurements evidenced nitrateremoval activity of biofilm. When different concentrations ofDO were applied to the reactor, generally decreasedconcentrations of DO were observed as bed depth increased fromthe bottom of the reactor. Greatest decrease of the DO wasobserved in the lower 20% of the bed depth. Nitrate removalefficiency was inversely proportional to influent DOconcentrations (8.3-11.9 DO mg L^-1) or nitrite loadingrates (0-5.5 N-NO₂ ^- kg m^-3 day^-1) employed in this study. Nitrite loading rates to achieve morethan 90% of nitrate removal efficiency were 1.46 N-NO₂ ^-kg m^-3 day^-1 or less at pH 7.5 and 0.34 N-NO₂ ^- kg m^-3 day^-1 or less at pH 6.8. Nitrate removal efficiency was 63% or more within the lower 20% of the bed depth at the nitrite loading rates that allowed more than 90% of nitrate removal efficiency of the reactor. The results of this study provide first quantitative data that nitrate removalperformance of an anoxic biofilm is inhibited by DO or nitrite,reported to be a limiting factor in the suspended biologicaldenitrification process.     

Transient modeling of trickling filters for biological ammonia removal

A dynamic model for nitrifying trickling filters is developed, based on material balances in the biofilm and the bulk liquid. The model predicts the profile of ammonia as a function of the operating parameters (volumetric flow rate and feed ammonia concentration) and the biofilm thickness as a function of filter depth and time. This revised version was published online in July 2006 with corrections to the Cover Date.     

Adaptive Consensus Principal Component Analysis for On-Line Batch Process Monitoring

As the regulations of effluent quality are increasingly stringent, the on-line monitoring of wastewater treatment processes becomes very important. Multivariate statistical process control such as principal component analysis (PCA) has found wide applications in process fault detection and diagnosis using measurement data. In this work, we propose a consensus PCA algorithm for adaptive wastewater treatment process monitoring. The method overcomes the problem of changing operating conditions by updating the covariance structure recursively. The algorithm does not require any estimation compared to typical multiway PCA models. With this method process disturbances are detected in real time and the responsible measurements are directly identified. The presented methodology is successfully applied to a pilot-scale sequencing batch reactor for wastewater treatment.     

Use of microbial activity measurements for monitoring RBC biofilms

Fixed biomass technologies, such as rotating biological contactors or biodiscs, have been applied for wastewater depuration both in large and medium–small-sized agglomerations. Biofilm’s composition and microorganism activity are essential parameters for the successful operation and control of these systems. Biofilm’s thickness and total dry weight have been widely used for biofilm’s characterization but, actually, are not sufficient to describe biofilm activity. In fact, biofilm’s activity is not proportional to the quantity of fixed biomass, but increases with the thickness of biofilm up to a determined level called the “active thickness”. Above this level, the diffusion of nutrients through the film becomes a limiting factor. A stable, thin, and active biofilm thus offers numerous advantages in water and wastewater treatment. Different parameters have been used to evaluate biofilm’s activity. The specific oxygen uptake rate, INT-dehydrogenase activity, and the ratio active/total cells have been applied for that purpose. These methods are not only simple and rapid but also sensitive, precise, and representative. The results obtained confirm the potential of the microbial activity measurements studied for an accurate biofilm’s characterization and biomass activity estimation in fundamental research and for the practical operation and control of fixed biomass depuration systems.     

Operational and Design Considerations of a Trickling Filter for Ammonia Removal from Potable Water

We studied the steady-state behavior of a mathematical model of a nitrifying trickling filter. In particular, we studied the effect of the operating conditions of the filter on the complete and safe nitrification. We presented the results with the help of the operating diagram of the system and we determined the range of operating conditions resulting in optimal operation. We also computed biofilm thickness along the filter depth and concentration profiles inside the biofilm, and compared them with experimental results found in the literature. The comparison shows very good qualitative agreement between model predictions and experimental data.     

气相色谱法测定水和废水中丙烯腈

本文通过采用气相色谱法，以ＧＤＸ－５０２为固定相，ＦＩＤ为检测器测定水和废水中的丙烯腈，精密度和回收率高．方法简便易行，能满足行业废水和地面水的监队是水和废水中丙烯腈分析的较理想方法。     

Cleanup of fractured rock aquifers. II. Effects of matrix diffusion and nonaqueous phase liquid

Model calculations are used to explore the effects of the kinetics of diffusion of dissolved organic compounds into and out of low-permeability porous materials and of the rate of solution of nonaqueous phase liquid (NAPL) droplets (into the aqueous phase) on the rate of cleanup of contaminated aquifers. Two models are presented: (1) the flushing of organic compounds initially distributed as NAPL droplets in a fracture in a porous rock aquifer, and (2) the removal of organic compounds initially present as NAPL in an aquifer containing low-permeability porous clay lenses. NAPL droplet size is found to be of much less importance than the spacing of the fractures in the porous rock in the first model or the thickness of the clay lenses in the second.     

Methodology for environmental assessment of proposed activity using risk analysis

This study applies a process of detailed assessment to summarize the potential impact of a proposed construction or other activity on the environment before implementation of an investment plan. The aim of the study was to develop a general methodology for analysis and evaluation of environmental issues connected with planned activities and proposed projects (especially buildings and engineering constructions, required implementation of environmental impact assessment process) using a risk analysis method, thus enabling the best option among the proposed activities to be chosen. The methodology was developed for conditions in Slovakia but could be arranged for any other country considering national conditions, requirements, standards and legislative. Application of the developed methodology in environmental impact assessment could create preconditions for more effective implementation of the EIA process. This paper provides a framework for the risk analysis component of the scoping phase within the EIA process. The process outlined in this paper will assist with determination of an estimation of risks to environmental and health of proposed activities.     

Long-term monitoring of streambed sedimentation and scour in a dynamic stream based on streambed temperature time series

This study presented the monitoring and quantification of streambed sedimentation and scour in a stream with dynamically changing streambed based on measured phase and amplitude of the diurnal signal of sediment temperature time series. With the applied method, changes in streambed elevation were estimated on a sub-daily scale with 2-h intervals without continuous maintenance of the measurement system, thus making both high temporal resolution and long-term monitoring of streambed elevations possible. Estimates of streambed elevation showed that during base flow conditions streambed elevation fluctuates by 2–3 cm. Following high stream stages, scouring of 2–5 cm can be observed even at areas with low stream flow and weak currents. Our results demonstrate that weather variability can induce significant changes in the stream water and consequently sediment temperatures influencing the diurnal temperature signal in such an extent that the sediment thickness between paired temperature sensors were overestimated by up to 8 cm. These observations have significant consequences on the design of vertical sensor spacing in high-flux environments and in climates with reduced diurnal variations in air temperature.     

Modular evaluation method for subsurface activities (MEMSA). A novel approach for integrating social acceptance in a permit decision-making process for subsurface activities

We investigate how the decision support system ‘Modular Evaluation Method Subsurface Activities’ (MEMSA) can help facilitate an informed decision-making process for permit applications of subsurface activities. To this end, we analyze the extent the MEMSA approach allows for a dialogue between stakeholders in a transparent manner. We use the exploration permit for the underground gas storage facility at the Pieterburen salt dome (Netherlands) as a case study. The results suggest that the MEMSA approach is flexible enough to adjust to changing conditions. Furthermore, MEMSA provides a novel way for identifying structural problems and possible solutions in permit decision-making processes for subsurface activities, on the basis of the sensitivity analysis of intermediate rankings. We suggest that the planned size of an activity should already be specified in the exploration phase, because this would allow for a more efficient use of the subsurface as a whole. We conclude that the host community should be involved to a greater extent and in an early phase of the permit decision-making process, for example, already during the initial analysis of the project area of a subsurface activity. We suggest that strategic national policy goals are to be re-evaluated on a regular basis, in the form of a strategic vision for the subsurface, to account for timing discrepancies between the realization of activities and policy deadlines, because this discrepancy can have a large impact on the necessity and therefore acceptance of a subsurface activity.     

Assessing water quality of drinking water distribution system in the South Taiwan

This investigation conducted a full-scale survey the drinking water distribution system in Kaohsiung city, Taiwan. The aim was to investigate whether the distribution system was capable of maintaining high water quality from the water treatment facilities through to the end user. The results showed that the distribution system can maintain high water quality, except for suitable chlorine residuals. The authors plotted chlorine residual contour maps to identify areas with low chlorine residuals, helping them prioritize sections that must be flushed or renewal. The contour maps also provide sufficient and clear information for locating booster chlorination stations. Contour maps enable water facilities to identify how water quality decays in the distribution systems and the locations of such decay. Water quality decay can be caused by properties of pipeline materials, hydraulic conditions, and/or biofilm thickness. However, understanding the exact reasons is unnecessary because the contour maps provide sufficient information for trouble-shooting the distribution systems.     

Landscape scale ecological monitoring as part of an EIA of major construction activities: experience at the Turkish section of the BTC crude oil pipeline project

Ecological monitoring is a complementary component of the overall environmental management and monitoring program of any Environmental Impact Assessment (EIA) report. The monitoring method should be developed for each project phase and allow for periodic reporting and assessment of compliance with the environmental conditions and requirements of the EIA. Also, this method should incorporate a variance request program since site-specific conditions can affect construction on a daily basis and require time-critical application of alternative construction scenarios or environmental management methods integrated with alternative mitigation measures. Finally, taking full advantage of the latest information and communication technologies can enhance the quality of, and public involvement in, the environmental management program. In this paper, a landscape-scale ecological monitoring method for major construction projects is described using, as a basis, 20 months of experience on the Baku-Tbilisi-Ceyhan (BTC) Crude Oil Pipeline Project, covering Turkish Sections Lot B and Lot C. This analysis presents suggestions for improving ecological monitoring for major construction activities.     

CONCRETop - A multi-criteria decision method for concrete optimization

CONCRETop is a novel multi-criteria decision method developed by the authors of this study for concrete optimization, which can be used to optimize either conventional or non-conventional concrete mixes. It can be used to identify the main differences between concrete mixes in terms of three perspectives, namely quality performance, environmental impacts and cost efficiency, and the corresponding causes.The characteristics of concrete fundamentally depend on its target application (e.g. the structural design project). In other words, it depends on the requested characteristics demanded by the consumer. However, this method allows optimizing concrete mixes based on the three mentioned perspectives even if the specific characteristics of concrete for the selected application are unknown. For complicated cases like this one, five scenarios (business as usual, green, strength, service life, and cost) were proposed with different threshold values, in order to cover most of the construction cases (the majority of concrete applications).The major outcome of this method is to provide researchers with a validated approach to support the development of non-conventional materials with optimized technical performance and minimum cost, environmental impact and natural resources' consumption. The method is valid for any case studies and concrete mixes worldwide. Most importantly, this optimization process may change how we take care of the next generation and find sustainable alternative materials for the concrete industry.     

Determination of isocyanates, aminoisocyanates and amines in air formed during the thermal degradation of polyurethane

An air sampling method for the determination of isocyanates, aminoisocyanates and amines formed during the thermal degradation of polyurethane (PUR) is presented. The method is based on the collection of air samples using impinger flasks containing di-n-butylamine (DBA) in toluene with a glass fibre filter in series. Isocyanates are derivatized with DBA to urea derivatives, and amines are derivatized in a subsequent work-up procedure with ethyl chloroformate (ET) to carbamate esters. Amine, aminoisocyanate and isocyanate derivatives were characterized using liquid chromatography-time of flight mass spectrometry (LC-TOFMS) and liquid chromatography-chemiluminescent nitrogen detection (LC-CLND). Quantification was performed by LC-MS, monitoring molecular ions [MH]+ in the electrospray mode. The instrumental detection limits for amines, aminoisocyanates and isocyanates were in the ranges 30-40, 2-3 and 3-70 fmol, respectively. Thermal degradation products of PUR were observed in high concentrations during welding in district heating pipes and PUR-coated metal sheets. Eleven isocyanates, three amines and five aminoisocyanates were identified. The concentrations of isocyanates, aminoisocyanates and amines in samples collected in the smoke close to the welding spot were in the ranges 150-650, 4-290 and 1-70 ppb, respectively. In samples collected in the breathing zone, isocyanates and aminoisocyanates were observed in the ranges 9-120 and 4-19 ppb, respectively. The compounds were present in both gas and particle phases. Volatile compounds dominated in the gas phase, whereas less volatile compounds dominated in the particle phase. The method presented makes it possible to sample and determine amines and aminoisocyanates, in addition to isocyanates. The need to monitor these compounds is clearly illustrated by the high concentrations found during the thermal degradation of PUR.     

Multi-criteria group decision-making based sustainability measurement of wastewater treatment processes

There are various processes which can be used for wastewater treatment (WT), and the selection of the most sustainable one among different processes is a hard task. This study aims at helping the decision-makers (DM) to address this by developing an intuitionistic fuzzy set (IFS) theory based group multi-attribute decision analysis (MADA) method. Ten criteria in environment, economy, society-politic, and technology dimensions were employed to achieve sustainability measurement (SM) of WT processes. The multi-criteria sustainability assessment method developed in this study allow different experts to attend the SM, and enable the participants to employ the natural language/words to depict their intuitionistic opinions. Accordingly, the proposed method can achieve group SM under uncertainties. An illustrative case including four processes for wastewater treatment, namely Anaerobic-Anoxic-Oxic (AAO) process, Triple Oxidation Ditch (TOD) process, Anaerobic single-ditch oxidation (ASD) process, and Sequencing batch reactor activated sludge process (SBR), has been studied, and the results reveal that this method can determine sustainability sequence of different WT processes.     

固相萃取-液相色谱/质谱法测定水中硝基苯酚类化合物

建立了固相萃取-液相色谱/质谱测定水中硝基苯酚类化合物的方法。在最优条件下,7种硝基苯酚类化合物的分离度较好,目标物在0.02~3.00 mg/L范围内线性良好,相关系数均0.998,检出限为0.007~0.026μg/L,加标回收率为71.1%~95.9%,精密度为7.36%~18.6%。该方法操作简便、准确,具有较好的实用性。     

Measurement instability and temporal bias in chemical soil monitoring: sources and control measures

Concern that human impacts on the environment may be harmful to natural resources such as soils as well as to living conditions is the major motivation for long-term environmental monitoring. However, the evidence that measurement bias is not constant through time affects time series as an artifact; this also holds true for chemical soil monitoring. Measurement instabilities occur along the whole measurement chain, from soil sampling to the expression of results. The first step in controlling measurement instability is to identify its relevant sources, and the second is to control it by stabilizing, minimizing, or quantifying measurement instability. For all five steps in the measurement process, from soil sampling to the expression of the analytical results, sources of measurement instability are identified and measures of control discussed, leading to the main conclusion concerning the requirement to continuously control the relevant environmental and measurement boundary conditions that may affect measurement instability. The innovative aspect of this paper consists in explicitly addressing measurement instability in chemical soil monitoring and tracking it along the whole measurement chain. The paper is also a plea for a change of paradigm in long-term environmental monitoring, namely to consider temporal measurements as unstable unless their degree of stability is traceably demonstrated, adequately quantified, and included in interpretation.     

UPLC-MS/MS法同时测定地表水中多种有机污染物

采用超高效液相色谱-串联质谱法直接进样测定地表水中26种有机污染物,通过优化试验条件,使各目标化合物在1.00μg/L^100μg/L范围内线性良好,相关系数(r 2)>0.995,方法检出限为0.003μg/L^1.0μg/L。将该方法用于地表水样的测定,加标回收率为79.0%~120%,6次测定结果的RSD均<15%。