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4'dater Treatment Plant Production Study <br />Innovati~-e Appioadhe~ PradiceI !?esults <br />requirement in the second quarter. Ferric sulfate continued to ouiperfonn <br />Alum in removing TOC in the third and fourth quarters. Typical alum <br />dosages used at this plant range from 65 mg/L to 70 mg/L. A low dose (0.5 <br />mg/L) of polymer is also used at the Grapevine WTP to aid in coagulation. <br />♦ All coagulating chemicals produced settled water with acceptable turbidity <br />levels. There were no significant performance differences beiween alum and <br />fecric sulfate in terms of turbidity removal at the plants. <br />Ozonation Pilot Testing <br />♦ At the Grapevine plant, preozonation slighUy improved turbidity removal in <br />six of eight jars tested over the four quarters. This comparison was made <br />each quarter behueen samples of the raw, low-ozonated, and high-ozonated <br />water using the same coagulant dose. [n the other two cases, lower coagulant <br />doses (than those used with the raw water) produced lower turbidities in the <br />ozonated water. This suggests that o2onated water may require different <br />doses of coagulant (from raw water) in order to achieve the same turbidity <br />removal. <br />~ Preozonation alone did not improve TOC removal. TOC levels in the <br />unozonated and ozonated settled water were approximately the same. <br />However, it is anticipated that the TOC removal at the full-scale ozone plants <br />will improve because of additional TOC removal in the biological filters. <br />Ozone condirions water so that biological growth can occur in the filters. <br />~ Preozonation conholled chlorination byproduct (TTHMs and HAAs) <br />formation. It is very likely that the City's finished water TTHM and HAA <br />levels would be below 0.04 and 0.03 mg/L respectively, if preozonaHon <br />facilities were installed. <br />~ The threshold odor numbecs (TON) were not reduced significanfly by <br />preozonaflon. Raw TON numbers were typically low enough at this plant that <br />it would be difficult to determine the eKect that ozonation would have on <br />them. ~ <br />~ Bromate levels exceeding the SDWA MCL of 10 Ug/L. were formed by high <br />ozone doses in two of the four quarters. lt is likely that this could be <br />controfled by adding ammonia to the raw water upstream of ozonation. <br />PR[LS[-NIC <br />