© 2007 IWA Publishing. Organic Waste Recycling: Technology and Management. Authored by
Chongrak Polpresert. ISBN: 9781843391210. Published by IWA Publishing, London, UK.
9 Land treatment of sludge
Land treatment of sludge has become a method that is being increasingly
considered by many municipalities throughout the world. It offers the advantage
of recycling nutrients back to the land at low cost, and of reclaiming lands being
spoiled by strip mining, deforestation and too much application of inorganic
fertilizers. Sludge is normally stabilized by anaerobic digestion or other suitable
means before application on land. Such stabilization eliminates obnoxious
odours and fly problems. Yield of grain and forage crops are increased by the
nutrients and water supplied by irrigating with digested sludge. Organic matter
in digested sludge accumulates in and imparts favourable characteristics to soils
because of its normally high humus content. “Biosolid” is a term commonly
used to describe sludge solids that are suitable for beneficial land application or
digestion to produce compost and/or biofuels as described in Chapters 3 and 4,
respectively.
Sludge production in the U.S. in 2005 was estimated to 7.6 millions dry tons,
and this quantity is expected to increase to 8.3 millions dry tons by 2010 (U.S.
EPA 1999). Table 9.1 shows the various means of sludge disposal in which
smaller wastewater treatment plants tend to use land application more than do