ABSTRACT

Many water/wastewater calculations involve the use of formulas and equations; for example, process control operations may require the use of equations to solve for an unknown quantity. To make these calculations, you must first know the values for all but one of the terms of the equation to be used. What is an equation? Put simply, an equation is a mathematical statement telling us that what is on one side of an equal (=) sign is equal to what is on the other side; for example, 4 + 5 = 9. Now, suppose we decide to add 4 to the left side (4 + 4 + 5). What must we do then? We must also add 4 to the right side (4 + 9). Consider the equation 6 + 2 = 8. If we subtract 3 from the left side (6 + 2 – 3), what must we do next? We must also subtract 3 from the right side (8 – 3). It follows that if the right side were multiplied by a certain number, we must also multiply the left side by that same number. Finally, if one side is divided by, for example, 4, then we must also divide the other side by 4.