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<br />Production <br /> <br />Treatment Plant <br /> <br />WClter <br /> <br />-- <br /> <br />requirement in the second quarter. Ferric sulfate continued to outperform <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 between alum and <br />ferric sulfate in terms of turbidity removal at the plants. <br /> <br />. <br /> <br />Ozonation Pilot Testing <br /> <br />. At the Grapevine plant, preozonation slightly improved turbidity removal in <br />six of eight jars tested over the four quarters. This comparison was made <br />each quarter between samples of the raw, low-ozonated, and high-ozonated <br />water using the same coagulant dose. In 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 ozonated water may require different <br />doses of coagulant (from raw water) in order to achieve the same turbidity <br />removal. <br /> <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 conditions water so that biological growth can occur in the filters. <br />. Preozonation controlled chlorination byproduct (lTHMs and HAAs) <br />formation. It is very likely that the City's finished water lTHM and HM <br />levels would be below 0.04 and 0.03 mg/L respectively, if preozonation <br />facilities were installed. <br />. The thr~shold odor numbers (TON) were not reduced significantly by <br />preozonation. Raw TON numbers were typically low enough at this plant that <br />it would be difficult to determine the effect that ozonation would have on <br />them. <br />. Bromate levels exceeding the SDWA MCL of 10 Dg/L were formed by high <br />ozone doses in two of the four quarters. It is likely that this could be <br />controlled by adding ammonia to the raw water upstream of ozonation <br /> <br /> <br />.~. <br /> <br /> <br />,,-.~ ,..", <br /> <br />-~-.._------- <br />,;,;L2'.:~:-~:::~~~:<':~~f:~~:":~ <br /> <br />;'~~:~~;~:_~:,~~~7;~~:~_~~;;:~~~~~::ili~~.:~~~~~~~'~~':~_~~~~~~~~:;;j/~~~~~~;,::~~.c~~~J:_;;1;~:~~;;i:~~~~~ <br />InllovCitive Approoches. .. Procticol eesults <br />