Manganese Removal- Water Treatment

[tipp79]

I'm currently working on a few water treatment plant upgrades which have been failing historically to meet Manganese PCVs in the treated water. One site, in particular, failed to meet the Utilities Design Spec of 25ug/l on 70 occasions and the Reg PCV of 50ug/l on 30 occasions between 1999 and 2006. There appears to be a decreasing no. of failures in the past 3 years.

Does anyone know of any good reference papers/ chapters in books which deals with the cause of manganese in reservoirs giving background to how manganese might be treated by better reservoir management? A lot of people talk about "manganese season" but no one seems to know why it happens and what the conditions are for manganese season to occur.


Cheers

 

[bimr]

Manganese is normally associated with ground waters. Some surface and shallow well waters may contain organic or colloidal manganese.

In treating waters than contain manganese, it frequently occurs that the pH is not raised high enough, with the result that iron (that is also present) is oxidized and removed and part of the manganese stays in solution. The pH values required for oxidation of manganese (with an aeration process) are much higher than that required for iron oxidation. The pH will probably need to be in the pH range of 9-10 units for oxidation of manganese.

You have not presented specifics on your treatment scheme and/or reservoir, but one would suspect that the manganese issue is related to the pH of the water.

 

[sbush]

I remember reading at least one article on this specific subject (i.e., seasonal manganese spikes in lakes and reserviors) in the AWWA Journal (not recently, however). You might try doing a search on the AWWA's web site (

http://www.awwa.org).

S. Bush

http://www.water-eg.com

 

[tipp79]

Cheers for the guidance.

The reservoir is an upland reservoir (actually 2 reservoirs). The process at the works is coagulation&flocculation, clarification (sedimentation), filtration and disinfection. Some but not all the manganese failures coincide with filter breakthroughs. From 1999-2007, there were 8,16,18,14,6,5, 2, none so far failures (above 25ug/l). Would improving reservoir management help? Adding aerators?

 

[49merc]

The addition of an oxidant such as chlorine, chlorine dioxide, or sodium permanganate can cause manganese to precipitate out. A usefull source for information is "Chemistry of Water Treatment" by Faust and Aly, available at the AWWA bookstore. There are some case studies in the manual aslo.