Theme 3-3-Water quality control measures in urban water distribution systems

Abstract

The sodium hydroxide, sodium silicate, polyphosphate, and zinc-orthophosphate have been assessed for their effectiveness for corrosion inhibition in drinking water supply of the City of Thunder Bay. The data for each water quality parameter from control and test zones was assembled into two categories. The data pertaining to water samples collected during the first two weeks prior to the application of an inhibitor was assembled into the “before application category”. Likewise, the data pertaining to water samples collected during the last two weeks of the application of an inhibitor was assembled into the “Ending application category”. In each category, the grouping of data for the two weeks period provided statistical stability in the data set for subsequent analyses. After statistical screening of the data sets, these data sets were analyzed for variety test procedures. Based on the results of these tests, the polyphosphate, sodium hydroxide, and sodium silicate respectively were found to produce the greatest decrease (60%, 58%, and 45%) in lead levels, while zinc-orthophosphate caused an increase in lead level by 17%. The lead level in the control zone diminished gradually throughout the test. On the other hand, the sodium hydroxide, sodium silicate, polyphosphate, and zinc-orthophosphate respectively reduced copper level by 86%, 59%, 38%, and 4%. Again, the copper level in the control zone was found to diminish gradually throughout the test.