Impacts of tilling and covering treatments on the biosolids solar drying conversion from Class B to Class A

Inhong Song, Susan A. O'Shaughnessy, Christopher Y. Choi, Charles P. Gerba

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


The objective of this study was to evaluate the effects of tillage and cover treatments of solar drying on the conversion of Class B treated sewage sludge to a Class A product. The experiments were performed over two years at Green Valley, Arizona in steel-constructed sand-filled drying beds of 1.0 m (width)×3.0 m (length)×0.6 m (depth). Freshly produced aerobically and anaerobically digested biosolids from nearby wastewater treatment plants received tillage and cover treatments for expediting solar drying and microbial inactivation. During the summer drying, covered drying bed increased faecal inactivation rate by 26% over other treatments and automated rain shield abated faecal coliform regrowth from summer rains. Tilling accelerated evaporation of moisture from the biosolids and increased the inactivation rate of faecal coliforms during the summer season. An automated retractable roof to protect the biosolids from rain aided in maintaining Class A criteria by preventing dried biosolids from re-wetting by rainfall. However, results from tilling and passive solar heating during the cold winter seasons did not improve the faecal coliform inactivation rate due mainly to lower ambient temperatures. Thus, tilling and cover treatments can be effective in accelerating biosolids solar drying and thus enhancing pathogen inactivation during the summer season. Investigation on the effects of tillage depth and frequency is recommended to determine optimal tilling practice.

Original languageEnglish (US)
Pages (from-to)2610-2618
Number of pages9
JournalEnvironmental Technology (United Kingdom)
Issue number20
StatePublished - Oct 18 2014


  • Biosolids
  • cover structure
  • faecal coliforms
  • solar drying
  • tillage

ASJC Scopus subject areas

  • Environmental Chemistry
  • Water Science and Technology
  • Waste Management and Disposal


Dive into the research topics of 'Impacts of tilling and covering treatments on the biosolids solar drying conversion from Class B to Class A'. Together they form a unique fingerprint.

Cite this