[USCC] Addition of Water Treatment Plant (Lime) Sludge to Biosolidsfor Composting

[Rufus Chaney]

Ken:

Adding Fe and Al rich water treatment residues (WTR) to biosolids and manure is increasingly practiced because the Al and Fe help lower the solubility of phosphate from the organic fertilizer. 

But you asked about lime WTR. High Ca can also help limit P solubility. If the WTR is really high pH (>10.5), it will delay the start of composting. CO2 generated is used initially to react with remaining CaO to make CaCO3 and the pH falls to 7.5-8 and composting proceeds normally. In the DC biosolids composting programs over the years, most incoming biosolids were about pH 10.5 from use of lime to reduce malodor. But if they tried to compost biosolids taken to full "Class A lime treatment" over pH 11 for 30 minutes or something close to that, it substantially delayed composting. But please recall that large amounts of the "Compro" product were marketed in bags and bulk for many years before the composting ceased because of political issues.

Mixing of high pH WTR with digested biosolids will cause a large release of NH3 which many would consider adverse; you raise odor from NH3 and loose N from the product. Undigested biosolids don't loose as much N as digested.

Product composts have pH about 7.5 from CaCO3 remaining in the final compost. Such composts supply limestone equivalent in addition to N, P, etc., and in many situations this adds to the value of the compost. Applications to acidic soils are more beneficial because limestone accompanies the other benefits of composted biosolids. Distrubed land in eastern Kansas and much of MO would be benefitted by the limestone. For really high limestone biosolids, use at soil conditioner rates can interfere with growing acid loving plants; Fe in the compost counteracts the higher pH, but azalea and rhododendron can be chlorotic. When used at "fertilizer" rates, or used for revegetation of roadside soils, other disturbed land, etc., the product is simply better than a lime free compost. If bagged, alkaline (pH 7.5 compost containing free CaCO3 equivalent) products need a label statement about not to be used for acid requiring plants.

Regards,

Rufus Chaney
Beltsville, MD

>>> KPowell at kdhe.state.ks.us 08/22/06 08:57AM >>>

Good Early Morning Compost World,

We have a medium size biosolids composting facility that would like to add
lime sludge to biosolids and wood chips for composting for odor control and
to make the compost have some characteristics as ag lime.  They are
proposing adding between 20% and 30% lime sludge to a mix of biosolids and
wood chips at the start of the composting process.  Two concerns I have are
disrupting the composting process because of it being too alkaline and the
end product having a high pH.  Has anyone done any experimentation with
this type of mix?   Does the amount of lime sludge being added seem to be
too high or about right?  They are currently producing a Class A compost
and would like to continue to produce this product.  Is the production of a
Class A compost possible with this mix.

Thanks for any help.


Ken Powell
Environmental Scientist
SW Processing Facilities Unit
Kansas Department of Health & Environment
Bureau of Waste Management
1000 SW Jackson, Suite 320
Topeka, KS  66612-1366
Phone: (785) 296-1121
Fax: (785) 296-1592
E-mail  kpowell at kdhe.state.ks.us 
www.kdheks.gov/waste 

_______________________________________________
Compost maillist  -  Compost at composter.com 
http://mailman.cloudnet.com/mailman/listinfo/compost 

This list is a service provided by the US Composting Council.

_______________________________________________


Ongoing Sponsors of the USCC Discussion list are:

Food Industry Environmental Network (FIEN), a regulatory and policy e-mail alert service for environmental, food and agricultural industry professionals.
Contact Jack Cooper 301/384-8287 JLC at fien.com --- www.fien.com 

Renewable Carbon Management, LLC with the containerized, in-vessel NaturTech Composting System www.composter.com rcm at composter.com 

(c) Copyright 2006 United States  - All rights reserved

Members posting CC copies to the list and other addresses will have their posting privelages suspended.  No exceptions!

Opinions expressed represent only the poster and are not necessarily the opinion or policy of any organization.

Non-members of USCC are encouraged to join the Council through our website at: http://www.compostingcouncil.org/membership.cfm     For discussion list policies and information regarding subscribing, unsubscribing, digest or other options, go to:http://mailman.cloudnet.com/mailman/listinfo/compost

For additional help in unsubscribing or to report bugs and problems, send a message to the List Manager, Jim McNelly, at compost-owner at composter.com