Monday 9:30 AM
[Presentation PDF]

Room: Diamond

Evaluation of Biosolids Composting Using Low Rates of Bulking Materials

A study is being conducted to determine the degree of composting under low rates of bulking materials to improve the District’s air-dried biosolids production process through integrating the "composting component.” The experiment includes two types of biosolids: centrifuge-dewatered lagooned-aged biosolids (aged biosolids) and centrifuge-dewatered biosolids (unaged biosolids), and three types of locally available bulking materials: tree leaves, wood chips and landscaping waste mixture (LWM). Each type of biosolids was mixed with a bulking material at the ratio of 2:1 (w/w) biosolids:bulking. There were two additional ratios for LWM treatments at 4:1 and 1:1 biosolids:LWM. The mixtures were then piled in a windrow of 5 feet wide, 4 feet high and 50 feet long. For the same bulking material and ratio, the windrow temperature was higher in the unaged than aged biosolids. For the same biosolids, it was higher in the LWM than in leaves and wood, and increased with the decrease in biosolids:bulking ratio. The unaged biosolids:LWM mixture at the ratio of 1:1 (w/w) or 3:1 (v/v) maintained the highest temperatures, which could meet the composting temperature standard of 55°C for 15 consecutive days. The preliminary results show that the addition of low rates of bulking materials could improve the stability of the District’s air-dried biosolids, and it is possible to develop a process to achieve biosolids composting that does not require a greater volume of bulking materials than biosolids. Biosolids stability and quality and pathogen levels will be determined at the completion of composting.

Moderator:  Lou Kollias


Guanglong Tian - MWRD

•PhD, 1992, Wageningen University, Netherlands
•Senior Environmental Soil Scientist, MWRD, 2002-
•Research Soil Scientist (10 years), International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria
•Advised: 8 MS and 6 PhD students
•Published: 110 scientific papers
•Recipient: the 1999 Young Scholar Award (early career award) of Soil Science Society of America