Water usage calculations

Because of often significant differences between the design evaporation and bleed rates and the actual operating conditions during the year, it is important for both the seller and user of water treatment chemicals to understand what water usage numbers should be part of any chemical consumption calculations, and from where they originated. 

the answers to the questions on total water usage are not always fully known or measured, and so it makes sense to attempt to calculate water usage more than one way, as a double check. 

It may well be found that evaporation is much less than anticipated due to, for example, inadequate airflow through the tower, insufficient rate of water recirculation, poor distribution of hot water spray through the tower, a fouled or damaged tower fill, a low hot water temperature returning to the tower, or a very high relative humidity. Such a reduced evaporation may be evidenced by only a small difference in the hot water temperature to the tower and the cold water temperature from the tower (AT). 

NOTE Typically the cooling range designed into a cooling tower will be around 15 to 25°F (8.3 to 13.9°C) 

Evaporation in a cooling system can normally be calculated to an acceptable degree of accuracy from simple, generalized formulas, as given below. Similarly, formulas and relationships exist for the calculation of drift, bleed, makeup, and cycles of concentration. There do not appear to be universally accepted standard symbols used in these formulas. 

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Using mass-integration strategies of segregation, recycle, interception and sink/ source manipulation, fresh-water usage can in principle be completely eliminated. Hence, for the same reaction conditions and water losses, tl target for wastewater discharge can be calculated from the overall water balance as follows (Fig. 4.4) ... 

The level of radioactivity encountered in the usual radioimmunoassay procedures is low enough so that liquid wastes may be disposed of in the sink with running water. In calculating the amount of radioactive material that may be disposed of via the sewage system from one building, one must know the water usage. This may be obtained from the water bill. The allowable quantity of in sewage is 4.0 x 10" /ii Ci/ml of water... 

As with the need to use more than one method for calculating overall water usage, when precise numbers do not exist, it is advisable, where possible and relevant, to use more than one chemical analysis parameter to calculate cycles of concentration. 

In a saturator installation, after each of day of operation total water usage was 16 gal (42 mL/min) as indicated by the water supply meter. The flow meter for the water being treated with sodium fluoride measured 300,000 gal daily. The analysis provided by the manufacturer indicates that the product contains 98.2% of sodium fluoride and the solubility is 4.0 % at 60°F. What is the calculated fluoride concentration ... 

Assume that the average water usage of a community is approximately 130 gal per person per day. After implementing water saving practices, the average water usage drops to 87 gal per person per day. A 10 million gallon per day (MGD) wastewater treatment plant is used for which 60% of the flow is residential wastewater. Calculate... 

The procedure for calculating methanol usage can best be explained by an example. Given a flowing temperature for one well of our example field of 65°F (as could occur with a remote well and subsea flow line), calculate the methanol required to prevent hydrates from forming. Assume that at the high flowing pressure there is no free water, but the gas is saturated. 

In terms of developing QSARs, water solubility is not a commonly used parameter in the development of quantitative models. When used it is usually in the form of the logarithm to the base 10 (log Saq). The reasons for its low usage are probably due to difficulty in calculation and colinearity with log Kow (which should be used in preference), rather than its lack of meaning or relevance. Despite this, the use of log Saq in QSAR should not be discounted either to describe the solubility cut-off, or as a parameter in it own right. 

The llux of monomers diffusing from the droplets to the particles will decrease as the former reservoirs are depleted, but reasonable calculations lead to the expectation that the arrival rate at the particle-water interface will exceed the usage rate even when more than 90% of the monomer has already left the droplets. 

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