For a working example of a simple water and salt balance, go to this page: Water and Salt Balance Example using Excel
There are various ways for management to quantify pollution of the environment and to assess the loss of product, raw materials or wastes to a stream. Some methods have more merit than others, while some are more costly than others and in general produce results of varying value. The application of a Water and Salt Balance through a plant or just through one section of a plant or process is one of these methods that will produce a better than average return on your investment.
Why a water & salt balance?
Under normal circumstances, when determining water balances, one tends to only refer to the hydraulic balance, i.e. the accounting of all the in- and output volumes entering and leaving a system. Opposed to this, a water and salt balance uses the hydraulic balance, but then also accounts for the dissolved solids carried in the water streams. In other words, a water and salt balance can be seen as a means of accounting for all the products carried in a system where the one value can be used to verify the accuracy of the other. A Water and Salt balance can best be described as a management tool, which assists the user in determining not only the concentration of dissolved solids in a body of water, but also more importantly, to determine the mass of salts carried in a dynamic system. Such a system can be river or a network of pipes, tanks and channels such as encountered in a metallurgical plant or at a mineshaft, or, for that matter, any other type of industry that uses water in its process.
Salt load mass balance
The amount of salts dissolved in water is normally expressed as a concentration such as in mg/l. This provides an indication of the concentration of the dissolved salt, but does not provide any information on the actual amount of salt dissolved in the system. If, however, the volume and the flow rate of the water are brought into the equation, a more meaningful result can be achieved. In this case, not only the concentration of the dissolved substance, but also the mass of the substance flowing past a specific point for a specific time period can be calculated. Expressions such as Kg/hour or Tons/day will now be the type of units used. When evaluating a dynamic system (i.e. moving opposed to stagnant water) then the latter method is far more meaningful.
Due to the fact that the greater part of South Africa, especially the industrialised areas, receives a rainfall well below the world average, South Africa is classified as a semi-arid country. We here in South Africa have a greater problem with salination (salting) of our river systems than many other countries, especially during the dry winter months when all, but a few rivers cease to flow. Salts and other eutrophic substances are continuously added to the rivers through various effluent streams or just through storm-water run-off or other diffuse pollution sources.
Our country’s water legislation has recently been amended to take this into account and the focus has now been shifted from a simple and uniform concentration-based water quality limit for effluent streams to an in-stream water quality objective. In the latter case each individual stream is evaluated and the safe mass of salt load it can assimilate is calculated, taking all factors (including the environment) into account.
Computer software
In the light of the above, it has therefore become essential that any industry that discharges water into a stream, be it water pumped from a mine, sewage effluent or any other industrial effluent or storm-water run-off, calculate the mass of salts added to this stream. This is done by measuring the flows of various streams inside the industry and couples these to chemical analyses results of these streams. In all but the simplest of cases, these calculations can become extremely complicated. AED will therefore developed a computer software model that automates all these calculations for each particular site. This program includes a database where all relevant data is stored and managed, and calculates the water and salt balances over any process in your industry. Depending on your needs, it can even automatically compile and print a month-end report, flagging areas where you have been wasting water or where you may have been wasting raw products. More importantly, it will tell you exactly to what extent your operation is impacting on the river system and complying (or not complying) with the water use license.
Apart from being extremely accurate, the second most important aspect of our software products is the user-friendliness. Many other developers of technical modelling programs often overlook this aspect. You only require a very basic knowledge of computer operation to understand our products.
For detailed information on this product and how we can customise our product to suit your needs, please contact us at info@aed.co.za.