What is sludge farming?

Question

What is sludge farming?

Answer 1

Wastewater treatment produces sludge, and sludge farming is an old-fashioned name for land disposal of sludge.

The wastewater may be industrial, domestic, or a mixture.  The sludge may be generated by primary treatment or secondary treatment.  Primary sludge is just the stuff that settles out of raw wastewater, so it is unstabilized and foul-smelling (almost pure s#!t, you might say :-).   Secondary sludge comes, for example, from activated sludge treatment processes.  Both types of sludge are often treated before land disposal.  Treatments can include chemical treatment  with precipitating agents or polymers, dewatering, and/or anaerobic digestion.  Digested sludge is probably the most common type of sludge that is land disposed.

Land disposal is a good method to return the organic matter and nutrients to the soil, but the problems lie with contaminants (like trace elements and pesticides) and with public acceptance (odor and perceptions of risk).  To give the process a better image, sludge is now sometimes referred to "biosolids".  "Sludge farming" is an oxymoron, because you're not growing sludge, you're getting rid of it er, excuse me, recycling it.  The preferred term would be "land disposal of biosolids".

Reference provided.