Cooling Tower Water Research Articles

Salinity and Boron Effects on Growth and Yield of Tepary and Kidney Beans

Crops tolerant to salt and boron have an advantage when grown in soils, near power plants, that are contaminated by saline cooling tower water or by waste products such as coal fly ash containing high levels of B. In addition, tolerant crops may have higher yields in arid and semi arid regions where salt and B problems coexist. This greenhouse study was conducted in order to compare the response of tepary bean (Phaseolus acutifolius A. Gray) and kidney bean (Phaseolus vulgaris L.) to combinations of high levels of solution B and chloride salts. The plants of both species were grown in 10-L plastic buckets containing silica sand and were irrigated with half-strength Hoagland's No. 1 nutrient solution to which boric acid and a mixture of NaCl and CaCl2·2H2O on a 1:1 equivalent ratio were added. Boron treatments consisted of 5, 20, and 25 mg·L-1 and the target electrical conductivity (EC) levels were 1, 4, 8, 12, and 15 dS·m-1. The maximum growth and yield for tepary bean occurred at 5 mg·L-1 B and 4 dS·m-1. These values of B and salinity were 6.5 and 4 times higher than those threshold values reported for kidney bean. Furthermore, tepary bean produced profitable yield (80% of control) in the 5 mg·L-1 B, 8 dS·m-1 treatment and it even produced beans at B concentration as high as 20 mg·L-1 B, four times higher than that observed for kidney bean.

Sampling and detection of Legionella pneumophila aerosols generated from an industrial cooling tower

Cooling tower water has frequently been cited as a source of infection in outbreaks of Legionnaires' disease. However, there have been few reports on the presence of legionellae in aerosols from cooling towers. This paper describes our use of an impinger or a six-stage microbial impactor for detecting legionellae in air around a cooling tower contaminated with L. pneumophila (1.2±0.3×105 CFU/100 ml). Phosphate-buffered saline, Page's saline, 2% yeast extract solution and buffered yeast extract (BYE) broth were tested to evaluate their collection efficiency. These solutions were compared in laboratory experiments using an aerosol of L. pneumophila serogroup (SG) 1. Because BYE broth was the most efficient and storable collecting fluid among them, it was used for outdoor air sampling. In the outdoor air sampling, aerosolized L. pneumophila SG 6 was detected in the air around the cooling tower by the impinger (0.09 CFU/l. air). No legionellae were detected by the impactor with Legionella-selective agar plates (WYOα) because the plates were overgrown with fungi. Repetitive element PCR (rep–PCR) and arbitrarily primed PCR (AP–PCR) were employed to assess the epidemiological relationship among Legionella isolates from the air sample and the cooling tower water samples. L. pneumophila SG 6 isolated from the aerosols produced rep–PCR and AP–PCR fingerprints identical to those of L. pneumophila SG 6 strains from the cooling tower water, suggesting that the bacterium was aerosolized from the cooling tower.

Sampling and detection of <italic>Legionella pneumophila</italic> aerosols generated from an industrial cooling tower

Cooling tower water has frequently been cited as a source of infection in outbreaks of Legionnaires' disease. However, there have been few reports on the presence of legionellae in aerosols from cooling towers. This paper describes our use of an impinger or a six-stage microbial impactor for detecting legionellae in air around a cooling tower contaminated with L. pneumophila (1.2+/-0.3x10(5) CFU/100 ml). Phosphate-buffered saline, Page's saline, 2% yeast extract solution and buffered yeast extract (BYE) broth were tested to evaluate their collection efficiency. These solutions were compared in laboratory experiments using an aerosol of L. pneumophila serogroup (SG) 1. Because BYE broth was the most efficient and storable collecting fluid among them, it was used for outdoor air sampling. In the outdoor air sampling, aerosolized L. pneumophila SG 6 was detected in the air around the cooling tower by the impinger (0.09 CFU/l. air). No legionellae were detected by the impactor with Legionella-selective agar plates (WYOalpha) because the plates were overgrown with fungi. Repetitive element PCR (rep-PCR) and arbitrarily primed PCR (AP-PCR) were employed to assess the epidemiological relationship among Legionella isolates from the air sample and the cooling tower water samples. L. pneumophila SG 6 isolated from the aerosols produced rep-PCR and AP-PCR fingerprints identical to those of L. pneumophila SG 6 strains from the cooling tower water, suggesting that the bacterium was aerosolized from the cooling tower.

Effect of electronic anti-fouling treatment on fouling mitigation with circulating cooling-tower water

The purpose of the present study was to investigate the effect of electronic anti-fouling (EAF) technology on fouling mitigation in a heat exchanger in an open cooling-tower system. Two tests were performed in a rectangular heat-transfer channel at 5 cycles of concentration: one without the EAF treatment and the other with the EAF treatment. The fouling resistance in the case with the EAF treatment was about 70% less than that in the case without the EAF treatment at the end of 270-hr tests.

Bactericidal Effect of Calcium Oxide and Calcined Shell Calcium on Legionella pneumophila.

Both calcined shell calcium, which was recently reported to have bactericidal effects on Escherichia coli O157 : H7, Pseudomonas aeruginosa, and Staphylococcus aureus, and calcium oxide, which is the main component in calcined shell calcium, were examined as a bactericide against Legionella species. A calcined shell calcium solution of 0.025% or above reduced L. pneumophila counts from the original 7.0 × 106 CFU/ml to less than 300 CFU/ml after an incubation period of 1 hr. In water samples taken from the cooling tower of a prefabricated house, a calcined shell calcium solution of 0.05% or above reduced L. pneumophila counts to less than 10 CFU/ml after an incubation period of 1 hr. There was no difference between the bactericidal effects of the calcined shell calcium manufactured from the shells of surf clams and that manufactured from oysters; surf clams and oysters are equally effective. Calcium oxide also showed similar bactericidal effects against L. pneumophila, and thus we believe that the effect is not specific to calcined shell calcium, but rather to effects caused by the alkalinity of calcium oxide. The use of calcium oxide or calcined shell calcium as a bactericidal agent against Legionella species in the cooling tower water of hotels or other buildings is therefore expected.

Fouling in enhanced tubes using cooling tower water: Part II: combined particulate and precipitation fouling

This work addresses fouling in a family of seven internally helically ridged tubes, which have different ridge heights, helix angles, and a number of ridge starts. Of specific interest are long term, combined precipitation and particulate fouling (P&PF) in cooling tower systems, and accelerated particulate fouling. The comparison of the P&PF and accelerated particulate fouling data shows a unique relationship. This allows one to infer the relative long-term P&PF performance of different enhanced tube geometries from accelerated particulate fouling data. For a small number of ridge starts (less than 25) and helix angles below 35°, the fouling resistance is proportional to the heat transfer coefficient (or the mass transfer coefficient, via the heat–mass transfer analogy). However, for a large number of starts and high helix angles (e.g., 45°), the fouling factor is considerably higher than one would predict, based on the mass transfer coefficient. It appears that this occurs because of low shear stress (affecting the foulant removal rate) in the interfin region. Recommendations are offered on geometries that will avoid high fouling penalty.

Fouling in enhanced tubes using cooling tower water: Part I: long-term fouling data

This paper describes the results of long-term fouling tests for cooling tower water flowing inside enhanced tubes. The data were taken using 800 ppm calcium hardness water supplied to an operating chiller/cooling tower system. The fouling mechanism is a combination of precipitation fouling and particulate fouling. Fouling data were measured for seven different enhanced tube geometries over a 2500 h operating period. The tubes tested had internal helical ridges, and the number of ridge starts varied from 10 to 45. Little fouling occurred until 1300 h. After 1300 h, moderate fouling began to occur in the tubes having a large number of starts. These tubes also provide the highest water-side heat transfer coefficients. Significant fouling existed in the tubes having 30–45 starts at the end of the test period. The salient finding of this work is that the potential for fouling increases as the number of starts and helix angle increases.

Treatment of industrial wastewater for reuse

Faced with environmental and water shortage problems at their Tutuka Power Station, Eskom, the South African Power Company approached Envig to assist them in finding a solution. This was achieved by the installation of a spiral reverse osmosis (SRO) plant to treat 12 Mld of mine water and spent cooling water. The result is a mine with no effluent problems, a new source of water for the power station and a treatment plant which produces significantly better cooling tower water and zero liquid discharge. Process details and 6 months of operational data are presented which demonstrate that good pretreatment and cleaning system design allow SRO to produce consistent high-quality water from this difficult and varying feed.

Mathematical modeling of evaporative cooling of water films in water-cooling towers

A mathematical model of evaporative cooling of water films flowing down vertical guards in a chimney-type water-cooling tower is developed. Results of a qualitative analysis of the nonlinear mathematical model are reported. Data obtained from a numerical solution of a boundary-value problem for a system of ordinary differential equations are presented in the form of graphs.

Ozone in the United States of America -- State-Of-The-Art

Applications for ozone in the United States have evolved through a lengthy maturation process, which began with drinking water treatment (taste/odor/color removal) in the early 1900s, and grew slowly until acceleration began in the mid-1980s. Although deodorization became a stable market in the 1960s-1970s, these applications were small, for the most part. One of the largest uses for ozone is oxidation of process chemicals in the chemical industry, which began in the USA about the 1940s, and subsequently has spread worldwide. Today, thanks primarily to environmental regulatory pressures which began to impact ozone in the mid-1980s, ozone now is used increasingly in the USA for drinking water treatment and for some municipal and industrial wastewater applications. The U.S. Environmental Protection Agency (EPA) has recognized the growing importance of ozone (> 200 drinking water plants use ozone today), and has appointed IOA representatives to two of its regulatory development committees as stakeholders. Several U.S. cities have installed or are installing wastewater treatment processes for potable reuse purposes, which include the use of ozone. Three full-scale U.S. pulp bleaching plants use tons/day quantities of ozone. Smaller applications for ozone include water treatment for cooling tower waters (biofouling control), swimming pools and spas, marine aquaria, bottled water disinfection and maintenance of high purity waters in the pharmaceuticals and electronics industries. A new application for ozone is in commercial laundries to reduce energy costs and replace chemicals. In mid-1997, a public declaration was made by an expert panel that ozone is Generally Recognized As Safe (GRAS) for contact with foods. This declaration opens the door for ozone to be used in U.S. food processing industries. U.S. research scientists and engineers are at the forefront in studies which define the technical aspects of ozone technologies in a variety of applications employing advanced oxidation, including the treatment of hazardous wastes, groundwater remediation, and process water recovery and reuse in the semi-conductor industry.

The Neutralizing of M-alkalinity of Cooling Tower Water by Air Pollutants

The Neutralizing of M-alkalinity of Cooling Tower Water by Air Pollutants

Development of a new seminested PCR method for detection of Legionella species and its application to surveillance of legionellae in hospital cooling tower water.

The presence of PCR inhibitors in water samples is well known and contributes to the fact that a practical PCR assay has not been developed for legionella surveillance. In this study, we devised a new seminested PCR assay for detection of Legionella spp. in water samples as a means of overriding the PCR inhibitors without loss of sensitivity. The seminested PCR assay utilized primers to amplify the 16S rRNA gene (LEG primers) of 39 Legionella spp. The assay was specific to legionellae, and the sensitivity was 1 fg of extracted Legionella DNA in laboratory examination. To evaluate the feasibility and sensitivity of the PCR assay in identifying the presence of legionellae, it was used to survey Legionella contamination in the water of 49 cooling towers of 32 hospitals. A commercially available EnviroAmp Legionella kit and a culture method were also used in the survey for comparison with the seminested PCR assay. The detection rates of legionellae in the samples were 91.8% (45 of 49) by the PCR assay and 79.5% (39 of 49) by the culture method. The EnviroAmp kit revealed that 30.6% of the water samples (15 of 49) contained inhibitors of the PCR amplification. However, the seminested PCR assay could produce the Legionella-specific DNA bands in 14 of the 15 samples. Although 8 of the 14 samples were positive in the first-step PCR, 6 of the 14 samples became positive in the second-step PCR. These results suggest that the effect of PCR inhibitors in samples, if any, can be reduced because of the dilution of the sample in the second-step PCR and that sensitivity of detection can be increased by the second-step PCR. Thus, the seminested PCR assay with LEG primers to amplify the 16S rRNA gene of 39 Legionella spp. was a practical and sensitive method to detect Legionella spp. in water samples.

Microphysical and optical features of polluted cooling tower clouds

In November 1993 an airborne field study was performed in order to investigate the microphysical and radiative properties of cooling tower water clouds initiated by water vapour emissions and polluted by the exhaust from coal-fired power plants. The number-median diameter of the droplet size distributions of these artificial clouds was in the range of 13 μm. The concentration of smaller droplets (diameters d D < 10 μm) increased with height and horizontal distance from the cooling towers. Close to the cooling towers, bimodal spectra were found with a second mode at 19 μm. The liquid water content (LWC) ranged between 2 and 5 g/m 3 and effective droplet radii ( R e) between 6 and 9 μm were measured. LWC and R e decreased with altitude, whereas the droplet concentration ( N D) remained approximately constant (about 2000 cm −3 ). An enrichment of interstitial aerosol particles with particle diameters ( d p) smaller 0.2 μm compared to the power plant plume in the vicinity of the clouds was observed. Particle activation for d m > 0.3 μm. was evident, especially in cooling tower clouds further apart and separated from their sources. Furthermore, radiation measurements were performed, which revealed differences in the vertical profiles of downwelling solar and UV radiation flux densities inside the clouds. The effective droplet radius R e was parameterized in terms of LWC and N D using equations known from literature. The close agreement between measured and parameterized Re indicates a similar coupling of R e, LWC and N D as in natural clouds. By means of Mie calculations, volume scattering coefficients and asymmetry factors are derived for both the cloud droplets and the aerosol particles. For the cloud droplets, the optical parameters were described by parameterizations from the literature. The results show, that the link between radiative and microphysical properties of natural clouds is not changed by the extreme pollution of the artificial clouds.

Practical Guidelines For Safe Operation Of Cooling Tower Water Ozonation Systems

Abstract Guidelines for the successful use of ozone as a stand-alone cooling tower water treatment method are discussed. Included are recommendations for system sizing, proper ozone residuals, mixing and distribution of the ozonated water, and potential problems and solutions. These include excessive or insufficient cycles of concentration, chemical contamination, low flow rates, high heat exchanger temperatures, and extended system turnover times. Also discussed are recommended maximum system downtimes, preferred types of towers and heat exchangers to treat with ozone, use of filtration systems, and elastomer compatibility with ozone. System monitoring and maintenance procedures are discussed along with ozonation safety considerations. With this information, two recently reported ozonation system failures are analyzed and the causes of failure are discussed.

Detection and occurrence of waterborne bacterial and viral pathogens

Detection and occurrence of waterborne bacterial and viral pathogens

A Comparison ofLegionellaand Other Bacteria Concentrations in Cooling Tower Water

Abstract A field study was conducted in which water samples collected from air conditioning cooling water reservoirs of high-rise buildings throughout an urban area were assayed for Legionella and for total bacteria. Buildings included within the study had ongoing biocldal treatment programs for the cooling towers. Separate sample analyses were performed to measure the viable colony concentrations of total bacteria and of Legionella in the process waters. The occurrence and viable counts of Legionella in 304 environmental water samples were determined by inoculating them onto plates of buffered charcoal yeast extract (BCYE) agar medium (a presumptive screening method). The samples were collected during summer months between July and September. BCYE plate cultures of 50 (16.4%) of the samples yielded Legionella with viable counts ranging from 2 to 608 colony forming units per milliliter. In the water samples, 281 (92.4%) yielded viable counts of bacteria that ranged from 9 to 1.2 × 106 per milliliter. This study demonstrates that Legionella are commonly present in the water of air-conditioning cooling towers and that there is no significant correlation between concurrently sampled culture plate counts of Legionella and total bacteria plate counts. Correspondingly, there is no demonstrated validity for use of total bacterial counts as an inferential surrogate for the concentration of Legionella in the water.

Distribution of legionellae in cooling tower water in Japan

Distribution of legionellae in cooling tower water in Japan

Simulation of the process of aerosol washout from the vent pipe plume of a nuclear power station on interaction with the steam-air plume of a water-cooling tower

Based on results of mathematical simulation and laboratory modeling, estimates are obtained for the effect of the washout of aerosol and its deposition on the surface of the earth in mixing of the plumes from the vent pipe and cooling tower of a nuclear power station (NPS).

Detection of Legionella spp. in cooling tower water by the polymerase chain reaction method

The presence of Legionella spp. in cooling tower water was investigated by using the polymerase chain reaction. Total Legionella spp. detection was performed with 20-mer 5S rRNA complementary DNA sequence primers, and specific Legionella pneumophila detection was performed with 20-mer and then 21-mer macrophage infectivity potentiator gene sequence primers. Of 27 cooling tower water samples, 25 were positive for Legionella spp., and 14 of these contained L. pneumophila.

Effect of Ozone on Corrosion of Metals Used in Cooling Towers

Abstract The effect of dissolved ozone on the corrosion of mild steel, copper (Cu), 90 Cu-10 Ni (nickel), 70 Cu-30 Ni, and admiralty in typical cooling tower waters with different solute contents was studied using electrochemical techniques. Results showed ozone at typical usage (0.1 to 0.2 mg/L) had no significant effect on the anodic passivation of mild steel. In general, corrosion in the presence of ozone was dictated by water chemistry. In supersaturated solution, general corrosion was suppressed by a layer of insulating mineral scale on the surface, regardless of the presence of ozone. In some solutions, however, high localized corrosion rates were observed both when ozone was present and when ozone was absent. In solution with low levels of Ca2+ and HCO3−, corrosion rates much higher than industry standard were observed with or without ozone. In a non-scaling, medium hardness water, ozone generally increased the corrosion rates of all yellow metals, especially at high concentration or under conditio...