Water Environment Federation (WEF) Discussion ForumsWater Environment Federation (WEF) Discussion Forumshttp://www.wef.org/TechnicalDiscussions/jfuller@wef.orgThu, 21 Aug 2008 17:29:56 GMT20http://www.wef.org/TechnicalDiscussions/Topic8410-9-1.aspxDave,</P><P>Ferric chloride is very efficient at P removal and is commonly done as a standalone process or in conjunction with BIO P. Like all chemical treatment processes it will add sludge to the system , the amount varies by where the addition point is in the process. There has been significant discussions recently elsewhere in this forum if you want check them out.</P><P>The impact on BIO-P uptake is also affected by the dosing position and by the dose rates.</P><P>Theoretically the two can work together particularly if the dose point is after the aeration tank and the dose is kept low. However if ferric is being dosed to meet discharge standards there will always be the likelihood of overdosing. </P><P>Think of this scenario.</P><P>Your plant has a bad day for BIO-P. Perhaps you have had some breakdowns or something that has resulted in a low BIO -P uptake so your effluent results are higher than you would like. Knowing that the BIO-P may take a couple of days to stabilize you increase your chem dose to get the effluent back where you want. After a couple of days things are going well so you decide to cut back the ferric. The effluent P will immediately climb because the BIO-P requires some time to re-adjust to the conditions. So you go back to where you were. A bit further down the track you have another problem and you have to increase the ferric dosing , and so the cycle continues.</P><P>If you are not careful you will end up doing 100% chemical P removal and i have seen this happen at a number of plants that were suppossedly doing chemical polishing after a BIO P process.</P><P>Regards</P><P>TerryFMon, 18 Feb 2008 16:03:02 GMTTerryFhttp://www.wef.org/TechnicalDiscussions/Topic8410-9-1.aspxWe add alum to the secondary clarifier influent if we get above 0.5 mg/l O-PO4. We then take grabs daily of the aerator effluent before the alum addition to see how the EBPR is doing. When it gets back below 0.5 we shut off the alum to that train. There is a 'flywheel" effect in that it takes a while for the alum to have an effect and it continues to have an effect for a while after shutting it off since the RAS brings it back to the aerator. You would probably see a lower release since the alum will be grabbing some P in the anaerobic zone but that should not effect the important P uptake in the aerobic zones. Of course you can over dose.....Mon, 18 Feb 2008 14:57:09 GMTRob Baurhttp://www.wef.org/TechnicalDiscussions/Topic8410-9-1.aspxDoes anyone have experience or knowledge on the effects of ferric chloride addition on the biological removal of phospahtes from a BNR system. Will addition of a metal salt inhibit the functioning of PAOs in any way?</P><P>DaveMon, 18 Feb 2008 08:53:25 GMTpappa