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[en] Biological and/or chemical fouling in utility service water system heat exchangers adversely affects operation and maintenance costs, and reduced heat transfer capability can force a power deaerating or even a plant shut down. In addition, service water heat exchanger performance is a safety issue for nuclear power plants, and the issue was highlighted by NRC in Generic Letter 89-13. Heat transfer losses due to fouling are difficult to measure and, usually, quantitative assessment of the impact of fouling is impossible. Plant operators typically measure inlet and outlet water temperatures and flow rates and then perform complex calculations for heat exchanger fouling resistance or ''cleanliness''. These direct estimates are often imprecise due to inadequate instrumentation. Electric Power Research Institute developed and patented an on-line condenser fouling monitor. This monitor may be installed in any location within the condenser; does not interfere with routine plant operations, including on-line mechanical and chemical treatment methods; and provides continuous, real-time readings of the heat transfer efficiency of the instrumented tube. This instrument can be modified to perform on-line monitoring of service water heat exchangers. This paper discusses the design, construction of the new monitor, and algorithm used to calculate service water heat exchanger fouling
[en] Essentially all industries include treatments with corrosion inhibitors, deposit control agents, and biocides as a part of their control of general corrosion, localized corrosion, fouling, and microbiologically influenced corrosion (MIC) in cooling waters and process waters. Most such treatments rely exclusively on monitoring the concentrations of the control chemicals rather than monitoring the effectiveness of those treatments. Inhibitors and biocides are expensive, can produce undesirable side effects as they interact with other chemicals, and will always be subject to effluent controls. Over-dosing of treatment chemicals, especially oxidizing biocides, will have undesirable side effects, including increased corrosion of piping, heat exchangers, and process equipment. This presentation provides results of biofilm monitoring at Exelon's Peach Bottom Atomic Station, including biocide optimization efforts. (author)
[en] There is a current need to develop novel non-toxic antifouling materials. The mechanisms utilized by marine organisms to prevent fouling of external surfaces are of interest in this regard. Biomimicry of these mechanisms and the ability to transfer the antifouling characteristics of these surfaces to artificial surfaces are a highly attractive prospect to those developing antifouling technologies. In order to achieve this, the mechanisms responsible for any antifouling ability must be elucidated from the study of the natural organism and the critical surface parameters responsible for fouling reduction. Dermal denticles of members of the shark family have been speculated to possess some natural, as yet unidentified antifouling mechanism related to the physical presence of denticles. In this study, the dermal denticles of one particular member of the slow-swimming sharks, Scyliorhinus canicula were characterized and it was found that a significant natural variation in denticle dimensions exists in this species. The degree of denticle surface contamination was quantified on denticles at various locations and it was determined that the degree of contamination of the dorsal surface of denticles varies with the position on the shark body. In addition, we successfully produced synthetic sharkskin samples using the real skin as a template. Testing of the produced synthetic skin in field conditions resulted in significant differences in material attachment on surfaces exhibiting denticles of different dimensions.
[en] In this research work, experiments were done to study the fouling behavior and performance of lab-made membranes using humic acid solution as feed. These membranes were prepared in lab using polyvinyl chloride membranes and Hydrophilic Bentonite nano particles via a non-solvent induced phase separation method. Membranes were further used in a dead-end filtration setup to filter a synthetic solution of humic acid and water to perform separation and fouling studies. Feed with different concentrations of humic acid was subjected to membrane system and performance was studied in terms of various parameters like flux, fouling ratio, flux recovery, relative flux, and rejection rate. Pure water flux, permeate flux, flux recovery, fouling ratio and rejection of humic acid of membranes increased in the presence of more hydrophilic Bentonite particles because of improved hydrophilicity. Total fouling was also affected, and irreversible fouling decreased in the presence of nano particle. However, agglomeration was observed between inorganic nano particles for 1.5 wt%. So membrane performance started decreasing by adding hydrophilic Bentonite nano particles more than 1%. (paper)
[en] Membrane fouling by soluble microbial products (SMP) remains one of the limitations for widespread applications of membrane bioreactor (MBR) systems. Over the past two decades, the characteristics and behaviors of SMP have attracted much attention, and efforts have been dedicated to clarify their role in membrane fouling in MBRs. However, to date, there are only few reviews directly relating this area, and the objective of previous reviews is to concentrate on SMP and their implications in biological treatment systems and their effluents. This brief review relating only to SMP-caused membrane fouling evaluation at the fractional level (SMP key components, sub-fractions and hydrophilic and hydrophobic fractions) and at the overall level (SMP overall roles, characteristics and factors) is presented, which could greatly help researchers and engineers to better understand SMP actual contribution to membrane fouling and adopt effective measures to avoid SMP-caused fouling in MBRs.
[en] The cooling water composition and microbial components of biofilms attached to stainless steel wafers submerged in three lake water types were evaluated to determine whether their biofouling potential differed in a predictable manner. The composition of the lake waters was different which affected biofilm composition, where the predominance of specific microbial groups varied between test systems and with time. Some prediction of biofouling potential was possible, and it was concluded that the cooling water in the vicinity of Bruce NGS had the lowest biofouling potential whereas greater biofouling could be expected in the Pickering and Nanticoke stations
[en] At high temperature, the circulation of fluid in heat exchangers provides a tendency for fouling accumulation to take place on the internal surface of tubes. This paper shows an experimental process of thermophysical properties estimation of the fouling deposited on internal surface of a heat exchanger tube using genetic algorithms (GAs). The genetic algorithm is used to minimize an objective function containing calculated and measured temperatures. The experimental bench using a photothermal method with a finite width pulse heat excitation is used and the estimated parameters are obtained with high accuracy
[en] The antifouling properties for some mortars with steel making slags were investigated by real marine immersion tests and a unique laboratory acceleration tests with a specially devised biofilm acceleration reactors. Mortars mixed with steel making slags containing abundant iron elements tended to form biofilm and also bifouling. The two kinds of biofilm formation tests were used in this study. Real immersion in marine environments and laboratory test with a specially devised biofilm acceleration reactor. The former evaluated the biofouling characteristics more properly, while the latter did the biofilm formation characteristics more effectively
[en] The objective of this project was to move the testing of uranium adsorbents from the laboratory to the field. We were successfully able to test fibers in both a flume and ocean environment under varying conditions to quantify the adsorptive properties and uranium uptake of adsorbents under coastal ocean conditions. Through this testing we have identified numerous challenges to be overcome prior to large-scale deployment of these fibers This project began in Phase I with laboratory experiments examining the effects of flow rates and water filtration on the absorption of uranium to fibers in flow-through columns. In this experiment we found that fibers adsorb most efficiently at a flow rate of 250 ml/min, on a per liter basis. However faster flow rates increase exposure volume and allowed for slightly greater total U absorption. Therefore a balance between current speeds that are too fast and potentially break down fibers and those that are slower will be important to consider, alongside bio-fouling and exposure time, when deciding which current regimes are best to place fibers in the ocean. Phase II examined biofouling, comparing exposure of fibers in filtered flume water to that in a coastal ocean environment. Results from the dock and flume parallel experiment indicate a strong effect of biofouling on the capacity of the adsorbent fibers to adsorb uranium towards the very end of the experiment. Dock and flume samples showed comparable adsorption rates with the flume maximum achieved at day 49 with an adsorbance of 3.4 g U/kg-ads while the dock maximum was reached at day 42 with an adsorbance of 2.7 g U/kg-ads. Biofouling mitigation techniques were also examined. A comparison of 5 m and 12 m samples showed less growth at 12 meters where there is less light as well as less growth on the copper cages, which are toxic to many marine organisms. Overall despite biofouling, particles and other elements present, the fibers adsorbed uranium up to 2.7 g U/kg-ads in our open water dock experiments. This is lower than the maximum achieved in the flume of 3.4 g U/kg-ads and much lower than rates observed with synthetic seawater in laboratory experiments. Phase III involved two parts: working at Woods Hole Oceanographic Institution (WHOI) we examined the feasibility of reusing fibers after ocean deployment. Fiber reuse is an important consideration for operational costs associated with deployment. At present our data implies that reuse after open ocean exposure may not be significantly more effective than a single long deployment of fibers. The second part of Phase III involved collaboration with A. Slocum and M. Haji at MIT to examine the effects of various enclosures for fibers. This also involved testing a rotating system, designed to be deployed as part of an offshore wind turbine.