Monitoring Of Biofouling Research Articles

Mechanisms, diagnosis, and monitoring of biofouling in membrane processes: a review

Mechanisms, diagnosis, and monitoring of biofouling in membrane processes: a review

Monitoring biofouling as a management tool for reducing toxic antifouling practices in the Baltic Sea

Over two million leisure boats use the coastal areas of the Baltic Sea for recreational purposes. The majority of these boats are painted with toxic antifouling paints that release biocides into the coastal ecosystems and negatively impact non-targeted species. Regulations concerning the use of antifouling paints differ dramatically between countries bordering the Baltic Sea and most of them lack the support of biological data. In the present study, we collected data on biofouling in 17 marinas along the Baltic Sea coast during three consecutive boating seasons (May–October 2014, 2015 and 2016). In this context, we compared different monitoring strategies and developed a fouling index (FI) to characterise marinas according to the recorded biofouling abundance and type (defined according to the hardness and strength of attachment to the substrate). Lower FI values, i.e. softer and/or less abundant biofouling, were consistently observed in marinas in the northern Baltic Sea. The decrease in FI from the south-western to the northern Baltic Sea was partially explained by the concomitant decrease in salinity. Nevertheless, most of the observed changes in biofouling seemed to be determined by local factors and inter-annual variability, which emphasizes the necessity for systematic monitoring of biofouling by end-users and/or authorities for the effective implementation of non-toxic antifouling alternatives in marinas. Based on the obtained results, we discuss how monitoring programs and other related measures can be used to support adaptive management strategies towards more sustainable antifouling practices in the Baltic Sea.

In-situ monitoring of biofouling on reverse osmosis membranes: Detection and mechanistic study using electrical impedance spectroscopy

Electrical impedance spectroscopy (EIS) was employed to monitor biofilm formation on the membrane surface in-situ and non-invasively. An EIS-derived parameter, the normalized conductance of the diffusion polarization (GDP) layer showed two stages of biofilm formation. The first stage was related to the accumulation of bacterial cells and the formation of the respiration products from the bacteria. The second stage referred to the accumulation of the extracellular polymeric substances (EPS) which was the main component for the formation of the biofilm matrix. The effect of a biostat, sodium azide was also investigated and its presence slowed down the growth of bacteria and caused the partial detachment of bacteria from the membrane surface. Sodium azide's effects were also reflected in the normalized GDP plot. The sustainable flux, at which the fouling was minimal, could be estimated from the rate of change of the initial increase of the normalized GDP with respect to flux. Conventional monitoring methods such as transmembrane pressure (TMP) or autopsy by confocal laser scanning microscopy (CLSM) on their own gave little insights into the mechanisms of the biofilm formation. This study demonstrates the ability of EIS to be incorporated into a “canary” cell located in a side stream of the high pressure membrane vessel for the monitoring of biofouling as well as for the assessment of the cleaning efficiency in a water treatment plant.

Online monitoring of biofouling using coaxial stub resonator technique

Here we demonstrate the proof-of-principle that a coaxial stub resonator can be used to detect early stages of biofilm formation. After promising field tests using a stub resonator with a stainless steel inner conductor as sensitive element, the sensitivity of the system was improved by using a resonator of shorter physical length, implying higher resonance frequencies (and by that a higher frequency range of operation) and improved sensitivity towards dispersion. In addition, the space between inner and outer conductor was filled up with glass beads, thereby exploiting the larger surface area available for biofilm formation.Analysis of the biofilm and the stub resonator signal, both as function of time, indicates that the sensor allows detection of early stages of biofilm formation. In addition, the sensor signal clearly discriminates between the first stages of biofilm formation (characterized by separated, individual spots of bacterial growth on the glass beads) and the presence of a nearly homogeneous biofilm later on in time. Model simulations based on the transmission line theory predict a shift of the sensor response in the same direction and order of magnitude as observed in the biofouling experiments, thereby confirming the operating principle of the sensor.

Interspecies interaction extends bacterial survival at solid–air interfaces

Despite the ubiquity of biofilms in natural and man-made environments, research on surface-associated cells has focused primarily on solid–liquid interfaces. This study evaluated the extent to which bacterial cells persist on inanimate solid–air interfaces. The desiccation tolerance of bacterial strains isolated from indoor air, as well as of a test strain (Pseudomonas aeruginosa), was determined at different levels of relative humidity (RH) using the large droplet inoculation method in an aerosol chamber. The cells survived longer at lower (25 and 42%) than at high RH (95%). Four of the seven indoor strains selected for further study showed extended period of survival following deposition as 0.05–0.1 ml of washed culture followed by desiccation, each with different effects on the survival of the test strain, P. aeruginosa. A strain closely related to Arthrobacter species afforded the highest level of protection to the test strain. Even though the desiccation-tolerant strains survived when they were deposited as bioaerosols, the protective role towards the test strain was not observed when the latter was deposited as a bioaerosol. These, which are often-unculturable, bacteria may go undetected during routine monitoring of biofouling, thereby allowing them to act as reservoirs and extending the habitat range of undesired microorganisms.

Research for Biofouling Detection Based on Optical Fiber Self-Referencing Technique and ANN

More attention is paid to on-line monitoring of biofouling in industrial water process systems. Combined optical fiber self-referencing technology with artificial neural networks (ANN) technology, real time detection technique for forming thickness and ingredient is put forward, which provides technical support and reliable data for analyzing biofouling influencing factors, contaminant separation and warning. Unclad fiber sensing mechanism and self-referencing fiber optic sensor are presented. Compensation technology based on radial basis function (RBF) neural network and learning algorithm are studied in order to solve the problem of measurement precision and range. Biofouling forming and optical characteristics in industrial real water systems are researched. A new method is provided for the research on biofouling in real water system, which can be used in other fields such as mining, environment protection, medical treatment and transportation of oil, gas and water.

Quartz crystal microbalance based on torsional piezoelectric resonators

A quartz crystal microbalance (QCM) is described, which is based on a torsional resonator, rather than a conventional thickness-shear resonator. Typical applications are measurements of film thickness in the coating industry and monitoring of biofouling. The torsional QCM is about a factor of 100 less sensitive than the conventional QCM. On the other hand, it can probe film thicknesses in the range of hundreds of microns, which is impossible with the conventional QCM due to viscoelastic artifacts. Data acquisition and data analysis proceed in analogy to the conventional QCM. An indicator of the material's softness can be extracted from the bandwidth of the resonance. Within the small-load approximation, the frequency shift is independent of whether the sample is applied to the face or to the side of the cylinder. Details of the geometry matter if the viscoelastic properties of the sample are of interest.

Monitoring of biofouling in papermill process waters

Slime or biofilm formation on paper machine equipment requires costly countermeasures. To provide early detection and efficacy control of countermeasures, deposit formation should be monitored. In this study, a monitoring method was developed based on differential turbidity measurement (DTM). Measurement was performed continuously, on-line, non-destructively, and in real time. As reference techniques, automatic pressure drop (PD) measurement and accumulation of biomass on slime boards were used. Both DTM and PD proved to be useful for the measurement of deposit formation on line in the side stream of a paper machine whitewater circuit. With these methods, the efficacy of chemical cleaning procedures and bacteriostatic compounds could be demonstrated, whereas enzymes and nontoxic dispersants turned out to be less effective. The effect of toxic substances confirms the role of vital microbial cells in the formation of the deposits. The use of such substances, which represent a potential hazard to the environment, can be optimized by automated monitoring systems as presented in this study.

Spectrophotometric monitoring of biofouling

The monitoring of biofouling is continuously evolving with new and better techniques being developed all the time. The major drawback of the currently used techniques is that these methods are complicated and time-consuming, involving culturing and counting of attached organisms. A continuously circulating batch culture system was therefore designed to study biofouling spectrophotometrically. Absorbance of bacteria attached to a glass tube was compared with direct counts done on DAPI-stained bacteria attached to 3CR12 coupons. Direct measurements of absorbance correlated well with the total counts obtained using the DAPI technique (r2=0.925). Spectrophotometry proved to be an easy, inexpensive and reliable alternative to techniques requiring laborious counting of microorganisms, for example the DAPI technique, for quantification of biofouling.

Spectrophotometric monitoring of biofouling

The monitoring of biofouling is continuously evolving with new and better techniques being developed all the time. The major drawback of the currently used techniques is that these methods are complicated and time-consuming, involving culturing and counting of attached organisms. A continuously circulating batch culture system was therefore designed to study biofouling spectrophotometrically. Absorbance of bacteria attached to a glass tube was compared with direct counts done on DAPI-stained bacteria attached to 3CR12 coupons. Direct measurements of absorbance correlated well with the total counts obtained using the DAPI technique (r2=0.925). Spectrophotometry proved to be an easy, inexpensive and reliable alternative to techniques requiring laborious counting of microorganisms, for example the DAPI technique, for quantification of biofouling.

Practical aspects of biofouling control in industrial water systems

Abstract Both water consumption and discharge in industrial water systems are currently minimised. The circulation of such water results in concentration of dissolved and suspended substances, promoting the growth of waterborne microbes, biofouling and subsequent macrofouling of the system and concomitant microbially induced corrosion. A number of reviews have been published on the mechanisms of microbially induced corrosion and the organisms involved. The subject of biofilm formation has also been well covered in the literature. A lack of information on the community structure and physiology is, however, apparent. Many advances have, nevertheless, been made in biofouling control. Probably the most important is the shift in emphasis from planktonic bacterial monitoring to sessile bacterial monitoring. This led to the introduction of a variety of different sessile monitoring techniques. Much experience has since been obtained on the use and limitations of these techniques and, to date, one of the main problem areas remaining is the monitoring of biofouling. Research has also indicated the problem of microbial resistance to nonoxidising biocides. This has suggested that some of these compounds may be mutagens. From an environmental point of view, it has become very important to verify this. This has also indicated the need to develop biocides which do not induce resistance in micro-organisms, and to investigate whether oxidising biocides are also capable of inducing resistance in micro-organisms. Recent studies have indicated that biofilm ecosystems respond to stress (i.e. biocides) in ways similar to macro-ecosystems. Generally, there is a decline in species diversity and a selection of more tolerant isolates. These developments have placed the spotlight on alternative technologies, like biodispersants, which have shown potential as biofouling control agents, and which should be investigated further. Physical control measures are currently still limited to pigging, although a number of other technologies show promise. Although fluid dynamics and their effect on biofouling control programmes have been well reported in the literature, it remains an aspect which is neglected by industry in terms of practical applications.

Diagnosis and monitoring of biofouling in enclosed flow systems — experience in groundwater systems

A monitoring cell (moncell) has been developed for the diagnosis and monitoring of biofouling and other problematic processes in groundwater systems. The device, relatively simple in design and application, is proving to be a useful tool, particularly for engineers who are not always aware of the processes occurring within their systems. All too often the yields from water supply boreholes and irrigation tubewells can decline without initially causing due concern. Yield decline can result from the clogging of parts of the system, (e.g. the screen, filter, pump, pipework) due to biofilm growth, chemical/biochemical deposition, and/or particle migration. Being unaware of the problem, or the nature of the problem, for too long a period can often lead to complete failure of the system. Early diagnosis is essential for optimum operation, maintenance and if necessary rehabilitation of the system. Trials with the moncell suggest that it could be used in other enclosed flow systems where a simple visual monitorin...