Microbiological Fouling Research Articles

Evaluation of Bio-Fouling Effect in Cooling Tower by Chemical Treatment

The main aim of this work is to check the bio fouling in cooling tower and its effect on power generation. The way to reduce bio fouling is necessary issue within the thermal power station, as it results in reduction of the heat transfer rate and ultimately reduction in the power generation rate of plant. So as to attenuate the energy consumption in process plant equipped with device network. In various branches of chemical industries fouling builds up on heat transfer surfaces is a heat transfer equipment burning extra fuel to compensate for a reduced heat recovery accepting reduction of plant output due to periodic equipment cleaning and recovering the cost of cleaning interventions. Microbiological fouling can cause energy losses and loss of tower efficiency. The pilot plant is very useful in the thermal power plant to test the cooling water and then it is used in the thermal power plant to reduce the losses due to the bio fouling. In large power plant they having pilot plant with PLC system and microprocessor with highly accurate sensors. It will give very accurate and direct digital readings on screen.

Composite material for optical oxygen sensor

A new composite material for use in optical molecular oxygen sensors is proposed. The absence of pores on the surface of the material avoids microbiological fouling and concomitant deterioration of the characteristics with time, and the presence of the mesoporous phase results in a linear calibration and acceptable response times, even for layers that are significant in thickness.

Results from 99 seawater RO membrane autopsies

This paper presents results from ninety-nine seawater reverse osmosis (SWRO) membrane autopsies carried out by the Genesys laboratory in Madrid from 2002 and outlines the technical issues surrounding fouling and scaling of sea water membranes. The authors discuss historical results of membrane autopsies and link recent trends and changes in plant design to potential fouling and scaling issues that may result in the future. Forty per cent of autopsies showed the presence of iron, 33% clay and 21% calcium and magnesium. The principle reason for membrane failure showed 27% was due to microbiological fouling, 19% were abraded, 18% oxidized, 12% of the samples showed metal oxide present as iron, manganese and aluminium. Scale formation from calcium carbonate, calcium sulfate and silica scale accounted for 8% of the membrane failures. Only 10% of the membranes were described as clean. There has been a trend over the last decade to increase recovery rates from 30% to 40–50%. This results in a greater concentration of cations and anions and likelihood of scale formation in last position elements. The presence of suspended solids and micro-organisms causes fouling in lead elements. To counter this there is a common practice of chlorinating, acidifying and coagulating the feed water. This is done principally with the commodity chemicals, sodium hypochlorite, sulfuric acid and iron chloride coagulant. The authors conclude from the results of ninety-nine SWRO membrane autopsies that the use of these commodity chemicals can be beneficial in the pre-treatment system but also can have some serious side effects for the membranes. Suggestions for alternative strategies are made.

Performance Analysis of Automated Control System for Condenser Water Treatment Unit

The air conditioning system in the Umm Al-Qura University (Albdiya Campus) was conceived to be a district cooling by a remote chilled water plant. Recently, there are two chilled water plants in the university installed strategically to provide chilled water to all the academic and administrative buildings of the university through distribution network with total capacity approximately of 12,000 tons of refrigeration. The plants were built based on cooling towers with open water cycle as heat rejection system. Water treatment chemicals has been used to protect the cooling systems from corrosion, scaling and microbiological fouling accompanied with dissolved and suspended water impurities. Different methods are being used to determine and control the treatment chemical concentrations and system performance indicators. Traditional chemical controller has drawback of indirect measurements and set points. The purpose of this paper is to present a solution to overcome the problems of traditional and conventional chemical treatment and control sys-tems. Central cooling plant number (1) assigned to perform experimental setup using new chemical treatment technology. Advanced automatic chemical treatment controller installed on condensers (1, 2 and 3), and certain key performance indicators were selected and monitored such as chemical and water consumption, power, energy saving, and maintaining system integrity and efficiency. Satisfactory results were obtained in terms of performance and cost of operation.

Effect of the surface modification of polymer membranes on their microbiological fouling

Composite polymer membranes with chemically different surfaces are prepared by the photochemical modification of Millipore microfiltration poly(vinylidene fluoride) and polysulfone membranes using 2-acrylamido-2-methyl-1-propanesulfonic acid, 2-hydroxyethyl methacrylate, and 2-(dimethylamino)ethyl methacrylate quaternized with methyl chloride. It is shown that, during the filtration of an E. coli suspension, the membrane flux substantially decreases with time owing to the fouling of the membrane surface by bacterial cells. The membranes with the hydrophilic surface are less susceptible to fouling than hydrophobic membranes, while the ability to recover the performance upon washing is higher for the membranes with a chemically neutral surface than for charged membranes. It is shown that the susceptibility of membranes to microbiological fouling reduces with a decrease in the roughness of the membrane surface. It is established that the membranes modified with the quaternized 2-(dimethylamino)ethyl methacrylate possess antibacterial properties. These membranes proved to be the most efficient in the filtration of natural surface water in a noncontinuous regime, a result that is explained by the ability of membranes to prevent the formation of a fouling biofilm on their surfaces.

Analysis of microbial community structure in a biofilm on membrane surface in the submerged membrane bioreactor treating domestic wastewater on the basis of respiratory quinone profiles

The objective of this study was to investigate the microbial community structure of the biofouling film formed on hollow-fiber membrane surfaces in the submerged membrane bioreactor (SMBR) with a nitrification-denitrification process. In this experiment, aeration was conducted intermittently (60 min off, 90 min on) cyclic anoxic and oxic conditions in the SMBR. The dominant quinone types of biofilm on the membrane surface in an intermittently aerated SMBR were ubiquinone (UQs)-8, -10, followed by menaquinones (MKs)-8(H4), -8(H2) and -7, but those of suspended microorganisms were UQ-8, UQ-10 followed by MKs-8, -9(H4) and -6. The change in quinone profiles of biofilm on the membrane surface suggested that UQ-9, MK-7, MK-8(H2) and MK-8(H4) contributed to microbiological fouling in the intermittently aerated SMBR treating domestic wastewater. The microbial diversities of suspended microorganisms and biofilm, calculated based on the composition of all quinones, were 9.5 and 10.9, respectively.

00/01568 Improving cooling water system performance

Several serious problems were encountered in three different cooling water systems during the commissioning of a new synthetic fuels complex in 1992. Fouling of heal exchangers with a silica sediment and cases of microbiological growth were found. These problems persisted and after the first year of operation, serious corrosion damage, iron precipitation, and microbiological fouling of carbon steel exchanger tubes were detected. This article reviews the dramatic improvements made since July 1994 in terms of corrosion control, fouling control, pH control, total dissolved solids/conductivity control, and the control of microbiological species.

The effect of turbulent flow and surface roughness on biofilm formation in drinking water

There is considerable interest in both Europe and the USA in the effects of microbiological fouling on stainless steels in potable water. However, little is known about the formation and effects of biofilms, on stainless steel in potable water environments, particularly in turbulent flow regimes. Results are presented on the development of biofilms on stainless steel grades 304 and 316 after exposure to potable water at velocities of 0.32, 0.96 and 1.75 m s−1. Cell counts on slides of stainless steel grades 304 and 316 with both 2B (smooth) and 2D (rough) finishes showed viable and total cell counts were higher at the higher flow rates of 0.96 and 1.75 m s−1, compared to a flow rate of 0.32 m s−1. Extracellular polysaccharide levels were not significantly different (P< 0.05) between each flow rate on all stainless steel surfaces studied. higher levels were found at the higher water velocities. the biofilm attached to stainless steel was comprised of a mixed bacterial flora including Acinetobacter sp, Pseudomonas spp, Methylobacterium sp, and Corynebacterium/Arthrobacter spp. Epifluorescence microscopy provided evidence of rod-shaped bacteria and the formation of stands, possibly of extracellular material attached to stainless steel at high flow rates but not at low flow rates.

Multicomponent Corrosion Inhibitor System for Recirculating Cooling Water SystemsBased on Nitrite, Molybdate, and Inorganic Phosphate

Abstract This paper presents the results of a study that was undertaken to optimize the ratio of the components of a new multicomponent inhibitor blend composed of nitrite/molybdate/inorganic phosphate. The mechanistic aspects of inhibition of the blend were also studied. Weight-loss and polarization data indicated that the optimum ratio of nitrite:molybdate:phosphate:orthophosphate was 3:2:1:1. The mechanism of inhibition in aerated tap water in the pH range 6.5 to 8.5 seemed to be a direct result of action on the anodic dissolution process. It appeared that the molybdate component promoted passive film formation. The blend had some obvious advantages compared with molybdate or nitrite blends. A decrease in the molybdate concentration would lower costs, whereas a decrease in nitrite concentration would reduce microbiological fouling tendency.

The use of planktonic bacterial populations in open and closed recirculating water cooling systems for the evaluation of biocides

Uncontrolled microbiological growth in recirculating water cooling towers results in biofouling and sludge formation with subsequent fouling of the system and microbiologically-induced corrosion. Biocides have therefore been used and are still being used to control such microbiological fouling. The problem has, however, been to find suitable methods for evaluating these biocides. During this study, planktonic bacterial numbers and population structure studies were used to evaluate biocides in situ. The results indicate that this method could be used to evaluate biocides objectively.

A screen arc model well to simulate iron bacterial fouling

A laboratory modelling system is described within which the activities associated with the microbiological fouling (plugging) of a well can be stimulated at much higher rates than are experiented in the field. The method employs a miniaturised quadrant of a well established within a defined chemostat system in which a nutrient enriched water is flowed through a gravel pack to a slotted stainless steel arc of well screen material into a discharge cistern where either drainage or over-spillage can be used to partially control flow. Oxygen conditions may be manipulated by either the introduction of continues or sequential pulses of air or oxygen exclusion through a nitrogen sparging the enclosed system. Monitoring is undertaken by determining the drainable volume of water from the well which declines as the biofilm volume increases and intercedes flow and also by measuring the drainage time which increases as a resistance to flow is generated by the biofilm growth. A process of self-purification of a model well subjected to total plugging with a consortial iron bacterial growth is described by way of an illustration of the usefulness of the procedure.

Comparison of the Rhine River and the O¨resund Sea Water Fouling and Its Removal by Chlorination

Microbiological fouling is usually the main fouling mechanism occurring on heat transferring surfaces immersed in natural water of temperature between 5–50°C. The fouling rate of two natural waters—the Rhine river and the sea water of O¨resund—has been studied. The dependence of fouling on flow rate and temperature is given. Chlorination is one of the most common biofouling control methods and it may be used for removal of already formed microbiological deposits. Tests performed on the Rhine water deposit are described and a mathematic description of the chlorination kinetics is presented. The dependence of biofilm destruction on flow rate, temperature, concentration, and operation conditions was examined.

GUPCO'S Experience in Treating Gulf of Suez Seawater for Waterflooding the El Morgan Oil Field

Summary Pressure maintenance by waterflooding in some reservoirs may be considered essential for satisfactory oil recovery. The main objective of waterflooding is to place water into a rock formation at both the desired rate and pressure with minimal expense and trouble. This objective, however, cannot be achieved unless this water has certain characteristics. The water, therefore, should be treated and conditioned before injection. This treatment should solve problems associated with the individual injection waters, including suspended matter. corrosivity of water scale deposition, and microbiological fouling and corrosion. Gulf of Suez Petroleum Co. (GUPCO) is waterflooding two fields, El Morgan and July, with Gulf of Suez (GOS) water. The paper addresses the treatment phases adopted to improve seawater quality before injection, and to control problems associated with untreated seawater. Also discussed are GUPCO'S experience in seawaterfloods, problems encountered, and corrective actions taken to overcome these problems. The chemical treatment programs adopted are presented along with final conclusions and recommendations that can be applied to similar floods in Egypt with GOS. Introduction Any treatment should be designed to solve the problems associated with individual injection waters. These problems involve suspended matters in the water, corrosivity. scale deposition, and microbiological fouling and corrosion. Additional problems that may result from water injection are injection well plugging and scale deposition both downhole in the oil producers and at surface in production equipment because of incompatible water mixing. Historically, in injection projects subsurface and/or makeup waters, river waters, and lake waters have been used. Seawater also has been used in many waterfloods. Pacific Ocean water, North Sea water, and Gulf of Mexico water have been used in similar waterflooding projects. ADMA has one seawater injection project in Abu Dhabi making use of Arabian Gulf water, which also is used in a large ARAMCO water injection project in Saudi Arabia and in Dubai as well. GUPCO has two injection projects for the El Morgan and July fields involving use of Gulf of Suez water. There is no published information on the characteristics of GOS water the treatment requirement for injection, or GUPCO'S operational experience with these projects. The main purpose of this paper is to introduce some information relative to GUPCO'S seawater injection system for the El Morgan field. Water Injection and Formation Plugging The quality of an injection water depends on its properties-e.g., suspended matter (turbidity caused by organisms and particulates), corrosivity in the system handling this water, and the tendency of the water to deposit scale. Hence the net water quality is dependent on all these properties simultaneously and is primarily connected with its capability to plug the formation rocks. Jones discussed rock plugging by solids. Generally, the tendency of an injection well to become plugged is dependent on the characteristics of both the formation and the injection water. The matrix of any rock is a fine filter for solids in the injection water (free or suspended). This is generally true in spite of differences in pore sizes that formation porous rocks may have. Consequently, the formation face of the water injection well is a good filter for the suspended solids present in the injection water and can become clogged. JPT P. 1449.