Cooling Tower Water Research Articles

Evaluation of DNA isolation procedures for detecting and quantifying environmental Legionella by real-time quantitative PCR

Six methods, QiAamp DNA Mini Kit (Q), Q with Sepharose 4B gel column (Q/G), Q with low melting point agarose (Q/L), freeze-thaw/phenol-chloroform lysis (FT-PC), FT-PC/G, and FT-PC/L, were evaluated for their ability to isolate DNA of sufficient quality to quantify Legionella using qPCR. Samples of mixing Legionella pneumophila (ATCC33152) and humic acid (HA, 0-126.8 mg/l) were treated by the six methods. Q, Q/G, Q/L, FT-PC/G, and FT-PC/L removed HA from 1.9-126.8 to <1 mg/l determined by A260 with a spectrophotometer. Q obtained the highest DNA yield, followed by Q/G. Dilution (10- to 100-fold) of DNA arising from extraction using Q, Q/G, FT-PC, or FT-PC/G prevented qPCR inhibition. The highest recovery of cells was found in DNA extracted by Q and diluted 100-fold, and followed by Q/G. The applicability of Q and Q/G with dilution was further validated with cooling tower waters. Q or Q/G with 10-fold dilution increased L. pneumophila detection, whereas 100-fold dilution obtained the highest cell concentrations. Similar results were found for Legionella spp. except that both 10- and 100-fold dilutions increased cell concentrations. Thus, Q with 10-fold dilution is suggested to detect and quantify Legionella spp. and detect L. pneumophila. For L. pneumophila-positive samples, 100-fold diluted DNA must be re-analyzed to accurately quantify L. pneumophila.

Energy and water conservation from air handling unit condensate in hot and humid climates

This study investigates the potential for energy and water sustainability in hot and humid climates by utilizing the condensate captured from large dedicated air handling units (AHUs) for pre-cooling outdoor air in another AHU and subsequently offsetting cooling tower water needs. In such climates, latent load is large enough throughout the year to produce a substantial amount of condensate, which is typically drained away from all the AHUs. In this study, condensate is collected from several AHUs and directed through another coil that pre-cools the warm and humid outdoor air which is supplying another AHU, called the condensate assisted pre-cooling (CAP) AHU. During the same time, the cooling towers require considerable amounts of make-up water to replace water losses occurring on a regular basis. The condensate, including that from the main cooling coil of the CAP AHU, is first supplied to the pre-cooling coil of the CAP AHU and is then routed through the cooling tower, which significantly reduces potable water usage and improves cooling tower water chemistry. It is found that condensate production is large enough to make pre-cooling cost-beneficial with energy savings of approximately 10% and the ability to offset cooling tower water demand in excess of 50%.

Membrane treatment of side-stream cooling tower water for reduction of water usage

A pilot study was conducted to determine whether membrane treatment on a side stream of recirculating cooling-tower water could reduce overall water usage and discharge. The treated permeate was returned to the cooling tower while the concentrate was discharged to the sanitary sewer. Flow rates, pressures and water chemistry were monitored. The pilot demonstrated potential substantial water savings. Maximum make-up water and discharge reduction were 16% and 49%, respectively. As high as possible permeate recovery is needed to maximize water conservation. Silica scaling on the membranes limited water savings in this pilot. Development of membranes with a solute-rejection capacity less than the 92% average of the membranes used in the pilot would assist in optimizing water savings. Decreased water outlays compensated for the additional energy used by membrane treatment. Scaling control is critical for economic operation.

Biofilm formation on galvanized steel by SRB isolate obtained from cooling tower water

In this study, we investigated biofilm formation on galvanized steel coupons by anaerobic bacteria isolate including sulphate-reducing bacteria (SRB) isolated from cooling tower water in a lab-scaled experimental setup. The test coupons were exposed to the culture of anaerobic bacteria isolate during 744 hours. In the course of time, anaerobic bacteria isolate could form biofilm on galvanized steel coupons. According to the statistical analyses, there was no significant difference between sessile and planktonic SRB counts, while a positive correlation was found out between SRB counts (P<0.01). Extracellular carbohydrate appeared to be degraded by bacteria culture in the test system. Keywords: Sulphate-reducing bacteria (SRB), cooling tower water, galvanized steel, biofilm.

Total and Viable Legionella pneumophila Cells in Hot and Natural Waters as Measured by Immunofluorescence-Based Assays and Solid-Phase Cytometry

A new method was developed for the rapid and sensitive detection of viable Legionella pneumophila. The method combines specific immunofluorescence (IF) staining using monoclonal antibodies with a bacterial viability marker (ChemChrome V6 cellular esterase activity marker) by means of solid-phase cytometry (SPC). IF methods were applied to the detection and enumeration of both the total and viable L. pneumophila cells in water samples. The sensitivity of the IF methods coupled to SPC was 34 cells liter(-1), and the reproducibility was good, with the coefficient of variation generally falling below 30%. IF methods were applied to the enumeration of total and viable L. pneumophila cells in 46 domestic hot water samples as well as in cooling tower water and natural water samples, such as thermal spring water and freshwater samples. Comparison with standard plate counts showed that (i) the total direct counts were always higher than the plate counts and (ii) the viable counts were higher than or close to the plate counts. With domestic hot waters, when the IF assay was combined with the viability test, SPC detected up to 3.4 × 10(3) viable but nonculturable L. pneumophila cells per liter. These direct IF methods could be a powerful tool for high-frequency monitoring of domestic hot waters or for investigating the occurrence of viable L. pneumophila in both man-made water systems and environmental water samples.

A new scheme for cooling tower water conservation in arid-zone countries

Cooling towers (CTs) that are used for heat rejection in water-cooled (WC) systems consume a large quantity of water, which is generally not available naturally. CTs are selected when the maximal cooling load is desired and under the worst design conditions. Typically, CTs operate under partial-load conditions and/or favorable weather conditions. Moreover, for most of the summer season, the dry bulb temperature (DBT) of the incoming ambient air is significantly greater than the incoming hot water temperature, and the air undergoes sensible cooling. Currently, the control scheme that is commonly used in most CTs maintains a constant exiting water temperature for different cooling loads and a different ambient wet bulb temperature (WBT) by regulating the air circulation through the CT. The air circulation is reduced with the help of a variable frequency drive (VFD), which results in a significant reduction in the fan power of the CT. This paper presents an assessment of CT performance with a VFD application using a computer simulation program and illustrates a proposed scheme for maximal water savings. These theoretical results demonstrated that reducing the air flow by applying a VFD in a CT can achieve at least a 25% reduction in water consumption.

Quantification of viable Legionella pneumophila cells using propidium monoazide combined with quantitative PCR

One of the greatest challenges of implementing fast molecular detection methods as part of Legionella surveillance systems is to limit detection to live cells. In this work, a protocol for sample treatment with propidium monoazide (PMA) in combination with quantitative PCR (qPCR) has been optimized and validated for L. pneumophila as an alternative of the currently used time-consuming culture method. Results from PMA-qPCR were compared with culture isolation and traditional qPCR. Under the conditions used, sample treatment with 50 μM PMA followed by 5 min of light exposure were assumed optimal resulting in an average reduction of 4.45 log units of the qPCR signal from heat-killed cells. When applied to environmental samples (including water from cooling water towers, hospitals, spas, hot water systems in hotels, and tap water), different degrees of correlations between the three methods were obtained which might be explained by different matrix properties, but also varying degrees of non-culturable cells. It was furthermore shown that PMA displayed substantially lower cytotoxicity with Legionella than the alternative dye ethidium monoazide (EMA) when exposing live cells to the dye followed by plate counting. This result confirmed the findings with other species that PMA is less membrane-permeant and more selective for the intact cells. In conclusion, PMA-qPCR is a promising technique for limiting detection to intact cells and makes Legionella surveillance data substantially more relevant in comparison with qPCR alone. For future research it would be desirable to increase the method's capacity to exclude signals from dead cells in difficult matrices or samples containing high numbers of dead cells.

Prevalence of Legionella Cooling Tower Water Contamination and Legionella pneumophila Antibodies Among Hotel Workers of Jiangsu, China

PP-29-162 Background/Aims: To determine the prevalence of Legionella spp. in the cooling tower (CT) water in Chinese Jiangsu hotels and evaluated their potential effects on the exposed population. Methods: A total of 148 CTs were investigated and cultured for Legionella spp. Water samples (500 mL) from each CT was collected and measured the prevalence of Legionella. A total of 304 staffs worked in 2 hotels with only Legionella pneumophila serogroup 1 (L. pneumophila serogroup 1) contaminated CT and 270 staffs without exposure to CT were recruited, and their serum anti-L. pneumophila antibodies were examined, and a total of 200 urinal samples were collected for L. pneumophila serogroup 1 antigen. Results: The prevalence of Legionella in the CT water was 75%, and L. pneumophila group 1 counts for 85.6%. The serum prevalence of anti-L. pneumophila group 1 antibodies in the exposed population was not significantly higher than unexposed subjects (OR = 1.05, P = 0.865). No Legionella urinary antigen was detected. Conclusion: Working in L. pneumophila group 1 contaminated CT did not increased exposed risk to L. pneumophila. We should not pay too much attention to the role of the Legionella spp. polluted CT in the infection pathway of Legionnaires disease.

Determination of Heavy Metals in Condenser Cooling Water System of FBTR

Fast Breeder Test Reactor (FBTR) is a 40MWt/13Mwe, sodium cooled nuclear reactor. Its cooling water system (CWS) consists of an open re-circulating type with an induced draft cooling tower and Palar river water is used the cooling medium. The metallurgy of CWS consists of carbon steel, copper, admiralty brass, aluminum brass, bronze, cupronickel etc. The possible release of metals (including heavy metals) to the environment from the CWS as a result of corrosion or due to the cooling water treatment chemicals are examined in this study using High Pressure Ion Chromatography (HPIC). The Zinc and Nickel concentrations in the makeup water as well as CWS blow down samples were found to at trace level. The concentrations of transition metals are well within the general standards for discharge of Environmental pollutants.

Simultaneous detection of Legionella species and Legionella pneumophila by duplex PCR (dPCR) assay in cooling tower water samples from Jakarta, Indonesia

Aim: Since culture method is time-consuming and has low sensitivity, we developed a duplex PCR (dPCR) assay for the detection of Legionella sp. and L. pneumophila in cooling tower samples. We used culture method as a gold standard. Methods: Optimization of dPCR method was performed to obtain an assay with high sensitivity and specifi city. The optimized method was used to detect Legionella sp. dan L. pneumophila in 9 samples obtained from 9 buildings in Jakarta. For culture method, the bacteria were grown or isolated on selective growth factor supplemented-buffered charcoal yeast extract (BCYE) media. Results: Of 9 samples tested by dPCR assay, 6 were positive for Legionella species,1 was positive for L. pneumophila, and 2 showed negative results. For the same samples, no Legionella sp. was detected by the culture method. Conclusion: dPCR assay was much more sensitive than the culture method and was potentially used as a rapid, specifi c and sensitive test for routine detection of Legionella sp. dan for L. pneumophila in water samples. (Med J Indones 2010; 19:223-7)

Calcium carbonate hardness removal by a novel electrochemical seeds system

Scale prevention is widely encountered in cooling water systems and is one of the main difficulties in both thermal and membrane water desalination processes. The usual scale control method applied in water desalination systems is based on the dosage of inhibiting compounds which are able to suppress scale precipitation up to a certain degree. Electrochemical scale control systems are beneficially used for hardness abatement of cooling tower waters. The main drawback hindering their use in desalination applications is the very high electrode area requirement. The novel electrochemical system developed in this study enables drastic reduction in the electrode area requirement. This is achieved by directing the precipitation to occur in a seeds crystallization vessel rather than on the cathode. Results obtained in preliminary experiments have already yielded a reduction in the specific cathode area by a factor exceeding 10 without altering the specific energy requirement. Furthermore, the seeds system appears to be free from the restriction of an asymptotic precipitation rate limit. The outstanding advantages of the low electrode area seeds system opens possibilities for widespread applications of electrochemical hardness removal in diverse processes requiring scale prevention measures.

An installation of technological importance at INCAS: – The air conditioning plant and its annexes

The air conditioning plant, the water recycling station, the water-cooling tower and the air storage tanks together with the trisonic wind tunnel form a whole complex technological assembly intended for aerodynamic experiments on different types of models in order to establish the optimal configurations, the drag and other aerodynamic parameters of importance for the aircraft designing. Building this complex technological installation was possible after many thorough technical-economic studies performed by Romanian and foreign specialists during 4 to 5 years of research and documentation, between the years 1967 and 1972 respectively and its construction lasted until 1978, when the first blowdowns were run in the trisonic wind tunnel, on April 17.

Boiler feed water: Purifying cooling tower water reduces costs

Boiler feed water: Purifying cooling tower water reduces costs

Removal of TDS from Cooling Tower Water by Using EDTA-Modified Bagasse Fibers

Modified by ethylenediaminetetraacetic acid (EDTA) salts and unmodified bagasse fibers were tested for the removal of total dissolved solids (TDSs) from cooling tower water. Parameters such as hydrogen ion concentration (pH), particle size of bagasse fibers, and the concentrations of adsorbent and adsorbate were studied to optimize the conditions to be applied on a commercial scale for the decontamination of effluents of cooling tower water. The optimum pH for TDS removal was between 6 and 6.5. The efficiency of TDS removal increased when the size of fiber particles decreased ( 100 μm ) and when the concentration of EDTA salt increased to reach 78 mg/g of modified bagasse fibers. The adsorption parameters were determined using both Langmuir and Freundlich isotherms. The preferential mechanisms for the retention of TDSs are a complexation process between the TDSs and chemical functions present on the surface of fibers, and the chelation process with the EDTA attached to the fibers. The results obtained cou...

Real-Time Testing of Bioburdens in Metalworking Fluids Using Adenosine Triphosphate as a Biomass Indicator

Adenosine triphosphate (ATP) assays have been used to quantify bioburdens (biomass) in low-organic-compound-content fluids (freshwater, seawater, cooling tower water, and similar fluids) since the early 1950s. The original methodology was labor intensive and required considerable laboratory skill. Over the past half-century, the protocol has been simplified substantially, but until recently, chemical interferences made it impractical to use the ATP test in metalworking fluids (MWF). This article presents precision and bias statistics for a new test protocol for ATP in emulsifiable oil, semisynthetic and synthetic MWF at end-use dilutions. Additionally it presents the results of field tests in which ATP data are compared with other MWF condition monitoring data. The field evaluation demonstrates the applicability of the new protocol to MWF bioburden condition monitoring.

Legionella in industrial cooling towers: monitoring and control strategies

Legionella contamination of industrial cooling towers has been identified as the cause of sporadic cases and outbreaks of legionellosis among people living nearby. To evaluate and control Legionella contamination in industrial cooling tower water, microbiological monitoring was carried out to determine the effectiveness of the following different disinfection treatments: (i) continuous chlorine concentration of 0.01 ppm and monthly chlorine shock dosing (5 ppm) on a single cooling tower; (ii) continuous chlorine concentration of 0.4 ppm and monthly shock of biocide P3 FERROCID 8580 (BKG Water Solution) on seven towers. Legionella spp. and total bacterial count (TBC) were determined 3 days before and after each shock dose. Both strategies demonstrated that when chlorine was maintained at low levels, the Legionella count grew to levels above 10(4) CFU l(-1) while TBC still remained above 10(8 )CFU l(-1). Chlorine shock dosing was able to eliminate bacterial contamination, but only for 10-15 days. Biocide shock dosing was also insufficient to control the problem when the disinfectant concentration was administered at only one point in the plant and at the concentration of 30 ppm. On the other hand, when at a biocide concentration of 30 or 50 ppm was distributed throughout a number of points, depending on the plant hydrodynamics, Legionella counts decreased significantly and often remained below the warning limit. Moreover, the contamination of water entering the plant and the presence of sediment were also important factors for Legionella growth. For effective decontamination of outdoor industrial cooling towers, disinfectants should be distributed in a targeted way, taking into account the possible sources of contamination. The data of the research permitted to modify the procedure of disinfection for better reduce the water and aerosol contamination and consequently the exposure risk.

Free Cooling Using Walter–side Economizer: Process Cooling Application At a Plastic Extrusion Plant

ABSTRACT This article is based on a detailed feasibility study conducted in 2007 for the installation of a free cooling system for process cooling at a plastic extrusion plant in the greater Toronto area utilizing a water economizer circuit. The energy consumption of the cooling system, which had a 130-ton chiller capacity, comprised 20 percent of the total electrical energy consumption for the production plant under study. Although the case study presented in this article is for a plastic extrusion process application, the findings can be applied to the design and savings calculations of free cooling systems for other industrial processes and for space cooling applications as well. This study proposed a free cooling system design for the process cooling system. The design makes use of a plate and frame heat exchanger that serves as a water-side economizer to cool the chilled water holding tank, using cooling tower water during cold weather conditions. This article explores the technical and financial fea...

Comparison of Plate Counts, Petrifilm, Dipslides, and Adenosine Triphosphate Bioluminescence for Monitoring Bacteria in Cooling‐Tower Waters

Effective bacterial control in cooling-tower systems requires accurate and timely methods to count bacteria. Plate-count methods are difficult to implement on-site, because they are time- and labor-intensive and require sterile techniques. Several field-applicable methods (dipslides, Petrifilm, and adenosine triphosphate [ATP] bioluminescence) were compared with the plate count for two sample matrices--phosphate-buffered saline solution containing a pure culture of Pseudomonas fluorescens and cooling-tower water containing an undefined mixed bacterial culture. For the pure culture, (1) counts determined on nutrient agar and plate-count agar (PCA) media and expressed as colony-forming units (CFU) per milliliter were equivalent to those on R2A medium (p = 1.0 and p = 1.0, respectively); (2) Petrifilm counts were not significantly different from R2A plate counts (p = 0.99); (3) the dipslide counts were up to 2 log units higher than R2A plate counts, but this discrepancy was not statistically significant (p = 0.06); and (4) a discernable correlation (r2 = 0.67) existed between ATP readings and plate counts. For cooling-tower water samples (n = 62), (1) bacterial counts using R2A medium were higher (but not significant; p = 0.63) than nutrient agar and significantly higher than tryptone-glucose yeast extract (TGE; p = 0.03) and PCA (p < 0.001); (2) Petrifilm counts were significantly lower than nutrient agar or R2A (p = 0.02 and p < 0.001, respectively), but not statistically different from TGE, PCA, and dipslides (p = 0.55, p = 0.69, and p = 0.91, respectively); (3) the dipslide method yielded bacteria counts 1 to 3 log units lower than nutrient agar and R2A (p < 0.001), but was not significantly different from Petrifilm (p = 0.91), PCA (p = 1.00) or TGE (p = 0.07); (4) the differences between dipslides and the other methods became greater with a 6-day incubation time; and (5) the correlation between ATP readings and plate counts varied from system to system, was poor (r2 values ranged from < 0.01 to 0.47), and the ATP method was not sufficiently sensitive to measure counts below approximately 10(4) CFU/mL.

Role of bacterial adhesion in the microbial ecology of biofilms in cooling tower systems

The fate of the three heterotrophic biofilm forming bacteria, Pseudomonas aeruginosa, Klebsiella pneumoniae and Flavobacterium sp. in pilot scale cooling towers was evaluated both by observing the persistence of each species in the recirculating water and the formation of biofilms on steel coupons placed in each cooling tower water reservoir. Two different cooling tower experiments were performed: a short-term study (6 days) to observe the initial bacterial colonization of the cooling tower, and a long-term study (3 months) to observe the ecological dynamics with repeated introduction of the test strains. An additional set of batch experiments (6 days) was carried out to evaluate the adhesion of each strain to steel surfaces under similar conditions to those found in the cooling tower experiments. Substantial differences were observed in the microbial communities that developed in the batch systems and cooling towers. P. aeruginosa showed a low degree of adherence to steel surfaces both in batch and in the cooling towers, but grew much faster than K. pneumoniae and Flavobacterium in mixed-species biofilms and ultimately became the dominant organism in the closed batch systems. However, the low degree of adherence caused P. aeruginosa to be rapidly washed out of the open cooling tower systems, and Flavobacterium became the dominant microorganism in the cooling towers in both the short-term and long-term experiments. These results indicate that adhesion, retention and growth on solid surfaces play important roles in the bacterial community that develops in cooling tower systems.

Legionellapollution in cooling tower water of air-conditioning systems in Shanghai, China

To determine Legionella pollution prevalence, describe the amount of Legionellae with respect to temperature in Shanghai cooling tower water (CTWs) in various types of public sites. Six urban districts were selected as the study fields, adopting multiple-phase sampling methods. Routine culture was used to identify Legionellae. Of the samples, 58.9% (189/321) were observed to be positive, 19.9% were isolated over 100 CFU ml(-1). Legionella pneumophila serogroup 1 was the most frequently isolated species (155/189, 82.0%), followed by Leg. micdadei that was at the second place (44/189, 23.3%). The mean CFU ml(-1) of Legionellae in CTWs reached its peak from July to September. Over all 15.4% of the samples exceeding 100 CFU ml(-1) were observed in a hospital setting. The prevalence of Legionella pollution in CTWs, especially in CTWs of subway stations and hospitals, is worrying, and the positive rate and CFU ml(-1) of Legionellae in CTWs have a close relationship with air temperature. The study demonstrates pollution prevalence rates in different types of sites and various seasons, and provides a proportion of different serogroups of Legionellae. It illuminates an urgent need for dealing with the potential risk of legionellosis in Shanghai, through improved control and prevention strategies.