Water Environment Federation (WEF) Discussion ForumsWater Environment Federation (WEF) Discussion Forumshttp://www.wef.org/TechnicalDiscussions/jfuller@wef.orgSun, 07 Sep 2008 17:21:49 GMT20http://www.wef.org/TechnicalDiscussions/Topic8565-9-1.aspxI was thinking only that Mg was brought into the digester as a counter ion to balance the PO4 charge in the bio-P "bug" and released when mixed with the VFA in the digester. With our very soft water in the Pacific North West we have very low Ca and Mg levels in most drinking water. Hadn't thought of that route of Mg transport.</P><P>We are looking at a 25,000 gpd grease trap facility to recover 5,000 gpd grease for Bio-diesel and put the emulsion and water content (72,000 COD) into the digester. Would that be a source of Mg or do restaurants just use detergents, not soaps?Mon, 10 Mar 2008 13:01:42 GMTRob Baurhttp://www.wef.org/TechnicalDiscussions/Topic8565-9-1.aspxIf you are referring to struvite precipitation in or after anaerobic digestion you have to factor in the routes by which soluble Mg2+ gets to the digester. Besides the dissolved Mg2+ concentration in the raw wastewater you need to condiser the fact that in hard, high alkalinity wastewaters the Mg2+ can form insoluble salts with soaps (stearate, oleate etc). These reactions act to increase the amount of soluble magnesium present in the digester becuase the stearates, oleates etc are degraded by anaerobic fermentation and the Mg2+ is released.Sat, 08 Mar 2008 11:14:11 GMTd jenkinshttp://www.wef.org/TechnicalDiscussions/Topic8565-9-1.aspxSince the limiting element for struvite is magnesium, does anyone control Mg discharges to their plant? Anyone have a significant Mg discharger? Epsom salt manufacturer or nigra tofu maker or?Thu, 06 Mar 2008 16:55:22 GMTRob Baur