Water quality fluctuations

Responsibility for mine water quality and quantity From time to time, the quality and flow rate of the mine water fluctuate significantly, and this may cause overloading of the entire system and subsequent non-compliance with permitted discharge concentrations, which can be only be buffered by the reactive filter materials. In this respect, contractual questions must be resolved between the operator of the wetland (WISUTEC) and the owner of the mine water (WISMUT) as to who is responsible for treatment and discharge. 

A very large petrochemical facility has many cooling systems and a variable water quality due to seasonal fluctuations. The river water makeup supply water is pumped approximately 100 km across a desert plain. The supply water pH can quickly increase to 8.6, the TDS rises to 1300 ppm, SS to 500 ppm (before clarification), chlorides to 650 ppm, and total hardness to 600 ppm. As a consequence, priority is given to stabilizing the makeup water quality as much as possible using acid dosing, but control is poor and acid incursions take place. 

The critical issue for a successful RO plant is pretreatment. Long-term operating experience proves the viability of continuous MF/UF pretreatment of RO for the desalination of a wide variety of water sources. MF/UF has proven to simplify and reduce the costs of traditional pretreatment, comprised of deep-bed media filters combined with chemical treatment. MF/UF produces filtrate of a consistent quality almost irrespective of fluctuations in feed-water quality. In the last five years, RO-membrane improvements, combined with the use of membrane filtration for pretreatment, have halved the cost of advanced treatment and are now more widely used for the reuse of municipal wastewater. 

There are rapid fluctuations in water treatment volume as well as water quality. Thus sterilization equipment must be flexible. 

The effect of tap water quality is illustrated in Figure 4.7, which shows the relationship between pH and copper or temperature and copper with CRECEP water (values measured during pipe rig experiments). The figure shows that when copper corrosion is stabilized (> 150 days operation), variations in copper concentration may be explained by pH and temperature fluctuations. 

In contrast to chemical analysis, in which standardization is already well advanced, statistical methods used for evaluating water quality data are, with few exceptions, not standardized but mostly a matter of tradition. The basis of all statistical evaluations should be an investigation plan which encompasses formulation of problems, data acquisition and an evaluation strategy. When drawing up plans for random sampling, all information which is already available about possible fluctuations of the system under examination should be taken into account. 

Trends and fluctuations can have different causes. These can be simply understood through their relationship to other water quality parameters by... 

The quality of process water can fluctuate with the seasons or change rapidly after rainfall. 

Hydraulic Transients in Pipes. Unsteady flow in pipe networks can be gradual therefore, it can be modeled as a series of steady solutions in an extended period simulation, mostly usefiil for water-quality analysis. However, abrupt changes in a valve position, a sudden shutoff of a pump because of power failure, or a rapid change in demand could cause a hydrauUc transient or a water hammer that travels back and forth in the system at high speed, causing large pressure fluctuations that could cause pipe rupture or collapse. 

SWRO system. For example, a partial second-pass configuration is nsed at the 95,000-m / day Tampa Bay seawater desalination plant. The second pass at this facility is designed to treat up to 30% of the permeate produced by the first-pass SWRO system as needed in order to maintain the concentration of chlorides in the plant product water always below lOOmg/L. The partial second pass at the Tampa Bay seawater desalination plant was installed to provide operational flexibility and to accommodate the wide fluctuations of source water salinity (16,000-32,000mg/L) and temperature (18-40°C). Typically, the product water quality target chloride concentration of 100 mg/L at this plant is achieved by only operating the first pass of the system. However, when source water TDS concentration exceeds 28,000 mg/L and/or the source water temperature exceeds 35°C, the second pass is activated to maintain adequate product water quality. The percent of first-pass permeate directed for additional treatment through the second pass is a function of the actual combination of source water TDS and temperature and is adjusted based on the plant product water chloride level. 

As for the turbines, no steam-purifying equipment of the type used on drum boilers is feasible, so that the steam from super-critical boilers tends to be of inferior quality. Deposits have been reported of cuprous oxide on the extra high-pressure turbines and of cupric oxide on some high-pressure turbines of sub-critical plant. These deposits may lead to a loss of efficiency and to some risk of corrosion. At intervals, slugs of solute are carried over in the steam, which is therefore of fluctuating quality. This is countered by periodic water-washing of the boilers. 

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