Problem 1
Estimate the total organic carbon (TOC) concentration of waste water whose chemical oxygen demand (COD) is \(500 \mathrm{mgL}^{-1}\left(\mathrm{O}_{2}\right)\). What fraction of the total (dissolved and particulate) solids content of \(720 \mathrm{mg} \mathrm{L}^{-1}\) is then made up of organic material? Assume the organic fraction can be represented as \(\left[\mathrm{CH}_{2} \mathrm{O}\right]\). Of what might the remaining solids consist?
Problem 2
An influent waste-water stream contains \(330 \mathrm{mg} \mathrm{L}^{-1}\) organic matter (both suspended and soluble) and \(27 \mathrm{mg} \mathrm{L}^{-1}\) ammonium ion (as \(\mathrm{N}\) ). Calculate the total BOD. What assumptions is it necessary to make?
Problem 4
After waste-water treatment in the activated sludge process, nitrogen is mainly in the form of ammonia and ammonium ion. Plot the fraction of nitrogen that is in the ammonia form (and therefore strippable by air purging) as a function of pH (at \(25^{\circ} \mathrm{C}\) ) over the \(\mathrm{pH}\) range from 6 to 10 .
Problem 7
Nitrification of ammonium ion is one of the steps during biological nitrogen removal processes. In waste water, whose pH and alkalinity are \(7.2\) and \(156 \mathrm{mg} \mathrm{L}^{-1}\left(\right.\) as \(\left.\mathrm{CaCO}_{3}\right)\), a concentration of \(7.8 \mathrm{mg} \mathrm{L}^{-1}\) (as \(\mathrm{N}\) ) ammonium ion is present before the process begins. Calculate the pH and alkalinity after nitrification has gone to completion, assuming this to be the only reaction that affects the \(\mathrm{pH}\).
Problem 8
A waste-water treatment plant produces sludge containing \(1800 \mathrm{~kg}\) of dry organic solids each day. Assuming the generic formula \(\left[\mathrm{CH}_{2} \mathrm{O}\right]\) for the solids and complete anaerobic digestion by reaction \(16.16\), calculate the fuel value of the generated methane in joules, barrels of oil, and kilowatt hours.
